º º º º º ºfflº º º --- º i - --~~ ºffl i. º º º º i º - - º º º º º ºffl ----------- º * H. º - - º --- --- º º --------- º --- º - - - --- º i. - i. ºffli º --~. º i º ------ º ºffl º º --- º --- º --- ºffl ºfflº º º #. - º º º º º - ºffl º º - º - ºfflºº ºfflº º º º º - º --- - #. º --~~~~ --~~ º ºffl º ºffl ºffli ºfflº iº --~~~~ - ------- º: ºffl º º º º: - º º - --~~~~ º º º - - - - º º --- º - - t º º --~~~ º º - º º º º --~~~~ º º º º - --> º º º --~~~~ - º º - - - - - | º - - --- º MICROIMPLANTS AS TEMPORARY ORTHODONTIC ANCHORAGE This volume includes the proceedings of the Thirty-Fourth Annual Moyers Symposium February 24-25, 2007 Ann Arbor, Michigan Editor James A. McNamara, Jr. Editorial Associate Katherine A. Ribbens Volume 45 Craniofacial Growth Series Department of Orthodontics and Pediatric Dentistry School of Dentistry; and Center for Human Growth and Development The University of Michigan Ann Arbor, Michigan ©2008 by the Department of Orthodontics and Pediatric Dentistry, School of Dentistry and Center for Human Growth and Development The University of Michigan, Ann Arbor, MI 48109 Publisher’s Cataloguing in Publication Data Department of Orthodontics and Pediatric Dentistry and Center for Human Growth and Development Craniofacial Growth Series Microimplants As Temporary Orthodontic Anchorage Volume 45 ISSN 0.162 7279 ISBN 0-929921-00-3 ISBN 0-929921–40–0 No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form by any means, electronic, mechanical, photocopying, re- cording, or otherwise, without the prior written permission of the Editor-in-Chief of the Craniofacial Growth Series or designate. CONTRIBUTORS ALFREDO ALVAREZ, Private Practice of Orthodontics, Necochea, Buenos Ai- res, Argentina; Postgraduate Orthodontic Training Program, University of El Sal- Vador. GEORGE ANKA, Department of Orthodontics, Nihon University, Tokyo, Japan. JESSE DONALD ARBON, Department of Orthodontics, University of North Carolina, Chapel Hill, North Carolina. TIZIANO BACCETTI, Assistant Professor, Department of Orthodontics, The University of Florence, Florence, Italy; Thomas M. Graber Visiting Scholar, De- partment of Orthodontics and Pediatric Dentistry, School of Dentistry, The Uni- versity of Michigan, Ann Arbor, Michigan. S. JAY BOWMAN, Private Practice of Orthodontics, Portage, Michigan. PETER H. BUSCHANG, Professor and Director of Research, Baylor College of Dentistry, Texas A&M University Health Science Center, Dallas, Texas. ROBERTO CARRILLO, Graduate Student, Baylor College of Dentistry, Texas A&M University Health Science Center, Dallas, Texas. BONG-KYU CHANG, Department of Orthodontics, School of Dentistry, Kyung- pook National University, Daegu, Korea. JASON B. COPE, Assistant Professor, Department of Orthodontics and Depart- ment of Oral and Maxillofacial Surgery, Baylor College of Dentistry, Texas A&M University Health Science Center, Dallas, Texas. MARIE A. CORNELIS, Experimental Morphology Unit, Orthodontics Unit, Université Catholique de Louvain, Brussels, Belgium; Visiting Research Scholar, Department of Orthodontics, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina. HUGO DE CLERCK, Professor, Department of Orthodontics, Université Catho- lique de Louvain, Cliniques Universitaires de St. Luc, Brussels, Belgium. JOHN W. GRAHAM, Private Practice of Orthodontics, Litchfield Park, Arizona. DUANE GRUMMONS, Assistant Clinical Professor, Department of Orthodon- tics, School of Dentistry, Loma Linda University, Loma Linda, California; Private Practice of Orthodontics, Spokane, Washington. SARANDEEP HUJA, Associate Professor, Department of Orthodontics, College of Dentistry, Ohio State University, Columbus, Ohio. SHOU-HSIN KUANG, Head, Department of Orthodontics, School of Dentistry, Veterans General Hospital; Lecturer, Orthodontic Department, Faculty of Den- tistry, National Yang-Ming Medical University Taipei, Taiwan, R.O.C. HEE-MOON KYUNG, Professor, Department of Orthodontics, School of Den- tistry, Kyungpook National University, Daegu, Korea. YOUNG-GYU LEE, Clinical Instructor, Department of Orthodontics, School of Dentistry, Kyungpook National University, Daegu, Korea. BIRTE MELSEN, Professor and Head, Department of Orthodontics, Royal Den- tal College, University of Aarhus, Aarhus, Denmark. CATHERINE NYSSEN-BEHETS, Experimental Morphology Unit, Or- thodontics Unit, Université Catholique de Louvain, Brussels, Belgium. GIOVANNI OBERTI, Assistant Professor, Department of Orthodontics, CES University, Medellín, Colombia. HYO-SANG PARK, Associate Professor, Department of Orthodontics, School of Dentistry, Kyungpook National University, Daegu, Korea. TERRY R. PRACHT, Private Practice of Orthodontics, Columbus, Ohio. MANI K. PRAKASH, Director, Indian Board of Orthodontics; Honorary Consul- tant Orthodontist, Medical Research Centre, Bombay Hospital, Mumbai, India. JAHNAVIRAO, Department of Orthodontics, Ohio State University, Columbus, Ohio. DIEGO REY, Professor and Head, Department of Orthodontics, The University of CES, Medellín, Colombia. JEFFERY A. ROBERTS, Private Practice, Roberts Orthodontics, Indianapolis, Indiana. W. EUGENE ROBERTS, Jarabak Professor and Head, Section of Orthodontics, Indiana University, School of Dentistry, Indianapolis, Indiana. P. EMILE ROSSOUW, Professor and Chairman, Department of Orthodontics, Baylor College of Dentistry, Texas A&M University Health Science Center, Dal- las, Texas. JON.W. SILCOX, Department of Orthodontics, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina. JANICE STRUCKHOFF, Private Practice of Orthodontics, Independence, Ken- tucky. JAE-HYUN SUNG, Professor Emeritus, Department of Orthodontics, School of Dentistry, Kyungpook National University, Daegu, Korea. J.F. CAMILLA TULLOCH, Distinguished Professor, Department of Orthodon- tics, School of Dentistry, University of North Carolina, Chapel Hill, North Caro- lina. CARLOS VILLEGAS, Assistant Professor, Department of Orthodontics and Maxillofacial Surgery, The Institute of Health Sciences, University of CES, Medellín, Colombia. PREFACE Microimplants are one of the most important advances in orthodontics to appear in recent years. These small temporary anchorage devices can be used to provide absolute anchorage to facilitate tooth movement in ways not thought pos- sible previously. Most typical orthodontic movements result in the generation of reciprocal forces that often require significant patient compliance (e.g., headgear, intermaxillary elastics) to achieve the desired treatment result. The introduction of microimplant protocols not only has reduced the need for substantial patient cooperation, but it also has facilitated specific tooth movements (e.g., tooth intru- sion, maximum incisal retraction, posterior space closure) that were difficult or even impossible to achieve with routine orthodontic mechanics. When a force is delivered to move teeth using microimplant anchors, tooth movement presumably is predictable and more efficient. The indications and contraindications for microimplant use as well as their clinical management were addressed during the 34"Annual Moyers Sympo- sium, which was held on The University of Michigan campus on Saturday, Febru- ary 24, and Sunday, February 25, 2007. The Moyers Symposium has had a long tradition of dealing with current topics in orthodontics and craniofacial biology, and this year was no exception. We invited eight internationally known clinicians and scientists to provide data on this most interesting subject. In addition, the 33” International Annual Conference on Craniofacial Research (the so-called “Presymposium”) was held on the Friday before the Symposium (February 23") in the Ballroom of the Michigan League. The Pre- symposium Conference featured papers relevant to orthodontics and craniofacial biology presented by an international group of investigators. Many of the presen- tations that focused on the topic of microimplants also are included as chapters in this volume. As in previous years, the Symposium honored the late Dr. Robert E. Moyers, Professor Emeritus of Dentistry and former Chair of the Department of Orthodontics and Fellow Emeritus and Founding Director of the Center for Hu- man Growth and Development. The meeting was co-sponsored by the School of Dentistry and the Center for Human Growth and Development. One individual whose tireless efforts must be acknowledged is Katherine Ribbens, who once again coordinated the editing and production of this volume of the Craniofacial Growth Series and without whom this volume would not exist. Kathy has managed all aspects of the preparation of this volume, from knowl- edgeable editing of content to the manipulation of the figures to typesetting the pages of the book. Her professional expertise and personal warmth are appreci- ated greatly by everyone involved with the Moyers Symposium. Thanks also to Debbie Montague, Michelle Jones, and Karel Barton from the Office of Continuing Dental Education for handling the registration process for the Symposium efficiently and smoothly, as in past years. The Department of Orthodontics and Pediatric Dentistry acts as publish- er of the monograph series along with the Center for Human Growth and Devel- opment. We thank Dr. Sunil Kapila, the Chair of the Department of Orthodontics and Pediatric Dentistry and Dr. Daniel Keating, the Director of the Center for Human Growth and Development for their financial support of this publishing en- deavor. This book, as well as all of the Craniofacial Growth Series monographs, are distributed through Needham Press of Ann Arbor and are available on the Web through www.needhampress.com. Finally, I thank the readers of this volume. You have helped facilitate the publication of the knowledge gained during the Moyers Symposia and Presym- posia meetings over the years. This monograph series provides a written legacy of excellence in orthodontics and craniofacial biology spanning more than three decades, a record of which the many participants can be proud. James A. McNamara, Jr. Ann Arbor, Michigan December, 2007 FRIENDS OF THE SYMPOSIUM George Anka Chester S. Handelman John C. Hall Robert J. Isaacson New-Conn Orthodontic Foundation John O. Nord Michael W. Paulus William D. Paulus Norman J. Pokley Michael E. Spoon TABLE OF CONTENTS Contributors Preface Friends of the Symposium What Influence Has Skeletal Anchorage Had on Orthodontics? Birte Melsen Microimplant Site Selection and Placement Hee-Moon Kyung, Bong-Kyu Chang and Young-Gyu Lee Bone Physiology and Biomechanics of Implant Anchorage: Closing Atrophic Edentulous Spaces W. Eugene Roberts and Jeffery A. Roberts The Treatment of Open Bite with Microimplant Anchorage Hyo-Sang Park, Hee-Moon Kyung and Jae-Hyun Sung Distalizing Mechanics with Modified Miniplates Hugo De Clerck and Marie Cornelis Temporary Skeletal Anchorage: The Experimental Literature Marie Cornelis, Hugo De Clerck, Catherine Nyssen-Behets and J.F. Camilla Tulloch Review and Implications of Translational Research to TADs Sarandeep Huja, Janice Struckhoff and Jahnavi Rao Complications Associated with the Use of Microimplants During Orthodontic Treatment Shou-Hsin Kuang Potential Complications with Temporary Anchorage Devices: Classification, Prevention and Treatment Jason B. Cope and John W. Graham Surgical Recovery and Patient Cost Associated with Temporary Skeletal Anchorage Treatment of Open Bite Jon W. Silcox, Jesse Donald Arbon and J.F. Camilla Tulloch Treatment of the Canted Occlusal Plane George Anka and Duane Grummons Microimplants: Little Partners for Big Challenges Alfredo Alvarez Thinking Outside the Box with Miniscrews S. Jay Bowman 33 51 111 135 149 171 189 221 245 263 297 327 Efficiency of a Bone-Supported Pendulum in the Distalization of Maxillary Molars: A Cephalometric Study Giovanni Oberti, Carlos Villegas, Diego Rey and Tiziano Baccetti The Baylor Experience with Using Mini-Implants for Orthodontic Anchorage: Clinical and Experimental Evidence P Emile Rossouw, Peter H. Buschang and Roberto Carrillo What We Do Know and What We Don’t Know About Microscrew Implant Anchorage Methods Mani K. Prakash The Edgewise Temporary Anchorage Device Terry R. Pracht 391 407 459 493 WHAT INFLUENCE HAS SKELETAL ANCHORAGE HAD ON ORTHODONTICS” Birte Melsen Skeletal anchorage is not new. It was introduced to clinical orthodontics in case reports that did not attract much attention when they were first published. Creekmore and Eklund (1983) used a surgical screw under the anterior nasal spine as anchorage for intrusion of incisors, and Fontenelle (1991) described how a surgical screw could reinforce the stability of a transpalatal bar used as anchorage for the retraction of anterior teeth. At the same time, prosthodontic implants were being used for orthodontic anchorage (Douglass and Killiany, 1987; Matthews, 1993; Odman et al., 1994; Favero et al., 2002; Ong and Wang, 2002). It was from this source that the first temporary anchorage systems were developed. The palatal implants and the retromolar implant both originated from the dental im- plant (Roberts et al., 1989, 1990; Wehrbein et al., 1996; Wehrbein and Merz, 1998). However, the palatal implant attracted the largest interest as it was replacing headgear as anchorage for the retraction of anterior teeth. The retromolar implant, on the other hand, did allow for treatment options that would not have been possible with conventional anchorage such as moving the mandibular mesially molars without any reactive forces act- ing on the anterior teeth. The reason for the greater interest in the palatal implant was due most likely to the fact that clinicians did not have to alter their treatment routines when replacing a headgear with a transpalatal arch reinforced by an implant. It may seem strange that in spite of the early reports mentioned above, clinicians did not realize the possibilities of the surgical screw be- fore accepting the palatal implant. The fact that palatal implants were in- troduced as a replacement for the compliance-dependent headgear may have been the reason. There always is a lag time between the introduc- tion and acceptance of a new approach. The first reports of the applica- tion of screws as anchorage also were case reports in which a screw re- placed what was then conventional anchorage. This occurred due to a lack of available anchorage teeth or to difficulty in obtaining sufficient compliance for the retraction of anterior teeth (Costa et al., 1998; Wehr- bein and Merz, 1998; Wehrbein et al., 1999). A different use of skeletal anchorage was described by Kanomi (1997) who used a small screw as anchorage for the intrusion of incisors in the mandible. Following these Skeletal Anchorage Influence reports, attention shifted gradually to the possibilities offered by skeletal anchorage resulting in the introduction of a large number of different skel- etal anchorage devices. The focus, however, still is centered overwhelmingly on the ad- Vantage offered by skeletal anchorage of providing treatment that is in- dependent of patient compliance. A review paper by Papadopoulos and Tarawneh (2007) demonstrated that the majority of reports on the use of skeletal anchorage were describing treatments that could have been com- pleted using compliance-dependent anchorage. The tooth movements for which the skeletal anchorage was serving were mostly to correct overjet and to distalize and/or upright molars. The immaturity of this subject is reflected in the fact that there are an overwhelming number of case reports and a limited number of research papers on the topic. The research comprises anatomical studies of bone quality in various insertion sites (Wilmes et al., 2006), retrospective stud- ies of factors important to the successes and experimental studies of the tissue reaction surrounding the screws (Huja et al., 2005; Cornelis et al., 2007). An attempt to define the indications for when and when not to use skeletal anchorage was made by the author of this paper (Melsen, 2005). Skeletal anchorage should not be considered an alternative to conven- tional anchorage but an opportunity to widen the spectrum of orthodontic treatment protocols. The focus of the present chapter, therefore, is on the differences in orthodontic practice before and after the introduction of the so-called TAD (temporary anchorage device). The question posed in the title of this chapter can be restated as two questions: 1. Has skeletal anchorage changed the clinical routine of the orthodontist? 2. Can the orthodontist perform treatments today that were not possible before the advent of TADs? HAS SKELETAL ANCHORAGE CHANGED THE CLINICAL ROUTINE OF THE ORTHODONTIST? When reviewing the literature, it becomes obvious that one of the major challenges the orthodontist has had to face is the lack of patient compliance. Consequently, a large number of compliance-free appliances have been introduced over the last decennia. Although presented as com- pliance free, most of these appliances cannot provide absolute anchorage. The addition of skeletal anchorage has made it possible for appliances Melsen such as the Pendulum appliance and the Distal Jet to obtain absolute anchorage (Carano and Testa, 1996; Karaman et al., 2002; Chiu et al., 2005; Ferguson et al., 2005; Kircelli et al., 2006; Escobar et al., 2007; Velo et al., 2007). The same argument can be used in relation to the inten- sive use of headgear that often is abandoned in favor of other appliances such as the Twin Block or Herbst, both of which are anchored in the man- dibular arch with predictable and sometimes undesirable side effects to the mandibular anterior teeth. In addition, with reference to these appliances, skeletal anchorage has facilitated the clinical routine for the orthodontist. High-pull headgear routinely used for vertical control has been replaced, to a large extent, by skeletal anchorage protocols; the possibility of molar intrusion the skeletal anchorage was introduced by Sugawara as a valid alternative to surgical impaction of the maxilla (Sugawara et al., 2002; Sugawara, 2005). This was corroborated further by De Clerck and colleagues (De Clerck et al., 2002; De Clerck and Cornelis, 2006). CAN THE ORTHODONTIST PERFORM TREATMENTS TODAY THAT WERE NOT POSSIBLE BEFORE THE ADVENT OF TADS? In order to answer this question, the limitations of conventional orthodontics should be discussed. There are three factors that must be in- cluded in any such discussion: (1) the anatomy, (2) the equilibrium of the force system developed by the appliance, and (3) bone metabolism. The Anatomy Understanding the anatomy of any given malocclusion is crucial when determining whether to choose orthodontic treatment or orthogna- thic surgery. The length and morphology of the basal bony components cannot be changed with orthodontic treatment and the level of acceptance determines whether surgery is the only possible option (Fig. 1; Proffit et al., 2003; Arnett and McLaughlin, 2004). On the other hand, the limitations of the alveolar process are dom- inated, to a large extent, by the skill of the orthodontist and by dogmas, not Science. One such dogma often accepted by the orthodontists is that teeth cannot be displaced outside the genetically given envelope (Wennstrom, 1987). Discussions have focused on the transverse dimension relative to the increasing use of expansion as an alternative to extractions as a solu- tion to crowding. Skeletal Anchorage Influence Figure 1. Left: Profile photograph and radiograph of an adult female patient with a pronounced convex profile. The shape and the length of the mandible do not allow for camouflage treatment. Note the short posteriorly inclined mandible. Right: Profile photograph and radiograph of the same patient following combined orthodontic treatment and orthognathic surgery includ- ing intrusion and retraction of the maxillary incisors and bisagittal split os- teotomy surgery combined with mentoplasty. Photographs and radiographs are provided courtesy of A. Fontenelle and J.F. Tulain. Melsen The controversy over expansion vs. extraction is far from being resolved (Vanarsdall and Secchi, 2005). Those authors warning against expansion hold that dehiscence is a result of expansion, while authors warning against extraction claim that the mode of expansion may be a determinant for the result (Handelman, 1997; Handelman et al., 2000; Bassarelli et al., 2005). Expansion frequently is generated with preformed super-elastic wires. Recently, Damon (1998, 2005) introduced the term “bio-zone” as a justification for expansions performed with the “Damon appliance.” However, there is little scientific evidence for either limits or the bio-zone, as the documentation has been limited to noting that dehis- cence often occurs with expansion. Skeletal anchorage has no bearing on the question of whether or not to expand. Still, it offers a real solution relative to unilateral expansion or contraction. Attempting to perform unilateral movement previously has been based on the generation of tipping against bodily movement (Bur- stone and Koenig, 1981). This differentiation invariably results, however, in equal and opposite forces acting on the two sides. With skeletal anchor- age, the adverse effect of a unilateral transverse movement can be avoided either by consolidating the anchorage side with a mini-implant or by the movement of the active unit directly against a mini-implant. With regard to Sagittal expansion, another dogma focused on in- cisor inclination. Particularly in adult patients, the limitations related to incisor inclination become critical, as surgery is considered a valid al- ternative to retraction of the maxillary teeth only in the case of a large overjet. Maxillary incisor retraction, however, often leads to undesirable side effects on the soft tissue profile, especially in adult patients. Pro- clination or protrusion of the mandibular incisors is an alternative that often will have a beneficial effect on the soft tissue profile, but the position of the mandibular incisors is still a matter of discussion. No consensus has been reached. Some authors consider proclination of the mandibu- lar incisors a risk (Dorfman, 1978; Hollender et al., 1980; Genco, 1996), but Diedrich (1996) demonstrated that if both the gingival health and the force system were monitored carefully, teeth could be moved outside of the existing alveolar process with their surrounding periodontium. This explains why several authors have failed to find an association between proclination and gingival recession (Ártun and Krogstad, 1987; Wenn- strom et al., 1987; Ruf et al., 1998; Ártun and Grobety, 2001). The find- ings of these authors were corroborated by Allais and Melsen (Allais and Melsen, 2003; Melsen and Allais, 2005) who studied 150 consecutive Skeletal Anchorage Influence Figure 2. Young female patient with pronounced dentoalveolar retrognathism. Her occlusion is characterized by overeruption of the maxillary incisors and a deep bite with both palatal and lingual gingival impingement. The headfilm reveals a pronounced pogonion and steep incisors, with the interincisal angle approximating 180°. Photographs and radiograph are provided courtesy of D. Allais. Melsen Figure 3. Photographs of the patient seen in Figure 2 following treatment. The mandibular incisors have been protracted and proclined in order to open space for two implants behind the mandibular canines. Note that the periodontium has improved and no dehiscence or retractions can be seen. There is a pronounced proclination of the upper and lower incisors following treatment. Skeletal Anchorage Influence cases (mean age = 33.7 ± 9.5) in which the mandibular incisors were moved labially. They found that no significant increase in the mean gingi- val recession (GR) occurred during treatment and that only the presence of a baseline recession, gingival biotype and gingival inflammation were related to a reduction in the periodontal support during treatment. None of the orthodontically related variables were associated significantly with the development of recession (Figs. 2 and 3). If Sagittal expansion is considered an option, skeletal anchorage can facilitate movements that otherwise would be possible only if the pos- terior teeth would serve as anchorage and the expansion would result in space opening up for either a bridge or an implant. With skeletal anchor- age, requirements to the posterior anchorage can be abandoned (Figs. 4 and 5). When the biotype does not allow for anterior displacement of the incisor segment distraction osteogenesis of the canine-to-canine segment, opening space for an implant in the premolar region has been recommend- ed (Triaca et al., 2004). However, the distraction appliance generally is anchored to the teeth and, as such, loads the weak labial periodontium. The loading of the incisors can be limited, on the other hand, if the forces generated during distraction are transferred to a skeletal anchorage Screw inserted immediately prior to the surgical procedure. This is exemplified by the 59-year-old male patient who presented with a large overjet and overbite with gingival impingement that resulted in periodontal breakdown lingual to the maxillary incisors (Figs. 6 and 7). In addition, the maxil- lary left central incisor had endured a trauma, which resulted in necrosis and endodontic treatment. In spite of the large overjet, the facial skeleton was characterized by a skeletal Class III. The large overjet was entirely dentoalveolar in origin and was caused by a pronounced dentoalveolar retrognathism. The malocclusion could not be treated with conventional orthodontic therapy and surgical intervention was not advisable due to the patient’s age. It was decided, therefore, to perform a distraction osteotomy to displace the canine-to-canine segment of the mandibular arch forward and downward, thereby opening space for an implant distal to the canines. The distraction was performed with a custom-made appliance. The poste- rior segment anchored to the consolidated posterior unit was connected to the anterior unit where the teeth were secured to two mini-implants by two Forestadent” expansion screws. Following the loosening of the anterior segment, an expansion of 8 mm was performed by turning the expansion screw daily for approximately one week until the 8 mm expansion was reached. Melsen Figure 4. A 43-year-old female patient with a prominent chin, a deep men- tolabial sulcus and large overjet with full distal occlusion. In the mandibular arch, the left canine has been removed due to ankylosis and there is moderate crowding. A 30-year-old female patient presented with the same type of malocclusion, i.e., a prominent pogonion and an increased overjet, the treatment indication of which was a forward displacement of the man- dibular anterior segment (Fig. 8). Whereas the age of the patient and the Severity of the malocclusion were the main reasons for considering this Skeletal Anchorage Influence - Figure 5. Patient seen in Figure 4 following treatment. The space for the miss- ing canine has been opened and the space filled with an implant. The protraction of the lower dentition against two mini-implants in the Symphysis has led to a marked improvement in the profile. treatment approach, the biotype of the periodontium related to the mandib- ular incisors in younger patients indicates that it would be risky to displace the anterior segment if the forces were transferred to the teeth. Therefore, mini-implants were inserted between the incisor and canine roots and se- cured to the incisors. This also allowed the line of action of the distraction force to be close to the CR of the anterior teeth. 10 Melsen Lack of Equilibrium Lack of equilibrium is most likely the cause of the majority of adverse effects seen in orthodontics. Forces delivered by any orthodon- tic appliance are equal and opposite to the active and the reactive unit and when trying to obtain differentiated anchorage tipping the active unit against the bodily movement of the reactive unit, this approach is accom- panied by the generation of vertical or transverse forces. Overcoming this obstacle clearly is the most valuable contribution that skeletal anchorage offers orthodontics. * The lack of equilibrium can be seen in relation to: • Space closure with absolute anchorage, • intrusion of extruded teeth, • correction of a tilted occlusal plane, • inconsistent tooth movement, and • regeneration of lost alveolar bone. In relation to space closure with absolute anchorage, the category of patients most frequently referred to is that of patients for whom the anterior teeth must be retracted without anchorage loss and skeletal an- chorage, as mentioned above, is providing the absolute anchorage (Parket al., 2001; Kyung et al., 2003; Chae, 2006; Fukunaga et al., 2006; Escobar et al., 2007). Another category of patients is that of patients presenting With agenesis for whom space closure is an alternative to the insertion of replacement bridges or, more recently, to the restoration of missing teeth With implants. If more than one tooth is missing per quadrant, replacement With implants still is needed. However, a displacement of the existing teeth Still may be needed before final reconstruction. The uprighting and mesial displacement of a first molar in the case of agenesis of the mandibular left second premolar is illustrated in Figure 9. Before initiating mesial displacement, uprighting was performed with a cantilever. As the molar was tied to the mini-implant while uprighting, the crown could not move distally and the rotation took place around the mesial aspect of the crown. Following uprighting, mesial displacement Was performed with the line of action of the force passing through the CR, Causing the molars to translate mesially. A 17-year-old female patient presented with a Class II maloc- clusion and agenesis of both maxillary second premolars, the maxil- lary left second premolar, and the mandibular left second premolar and persistence of the corresponding deciduous teeth (Figs. 10-12). The Class II relationship was corrected with a cast Herbst appliance with 11 Skeletal Anchorage Influence 12 Melsen R->F sequence is controlled by growth and ischemic factors that are superimposed on mechanically- induced inflammation (Roberts and Hartsfield, 2004c). The physiologic inflammatory response is secondary to functional and parafunctional load- 1119. A - \ Anabolic Modeling Catabolic Modeling |ſ - \ Remodeling Remodeling Anabolic Modeling Catabolic Modeling Figure 3. A generalized view of bone physiology showing the labial translation of a mandibular tooth. Remodeling is the internal turnover of alveolar bone driven by functional loading. Tooth movement and change in position of the alveolar process depend on catabolic and ana- bolic modeling. Adapted with permission from Roberts et al. (2006). 54 Roberts and Roberts INTEGRATED VS. NONINTEGRATED IMPLANTS Osseointegrated endosseous implants do not move in response to orthodontic loads. Displacement of the implant requires a loss of integra- tion (Starck and Epker, 1995; Aparicio and Orozco, 1998) or fracture of the interface (Roberts et al., 1984). Rigidly integrated TADs have a very high success rate (Wehrbein and Merz, 1998a; Odman et al., 1994; Rob- erts et al., 2004), but do require a separate surgical procedure to remove the endosseous fixture. Miniscrew systems do not achieve rigid fixation with bone routinely because of their design and surface characteristics. Adaptation of present miniscrews to achieve Osseointegration routinely is problematic. Once they are integrated, removal from bone can be difficult and there is a high probability of fracture when sufficient torque is applied to break the bone-implant interface (Morais et al., 2007). Development of reliable osseointegrated miniscrews for orthodontic anchorage will require a substantial research effort to develop second generation devices that are user friendly. It is necessary to achieve a level of rigid osseous fixation that is adequate for orthodontic or orthopedic anchorage (Roberts et al., 1989), but atraumatic removal of the TAD at the end of treatment is an essential requisite. The surgical placement of endosseous implants results in a layer of dead bone at the interface (Fig. 4; Roberts, 1984, 1988a; Roberts et al., 1987, 1989a). The manner in which this nonvital osseous tissue is resolved determines whether or not an implant will integrate. The most successful implant designs for osseointegration are titanium screws with a roughened surface and hydroxylapatite (HA)-coated cylinders, both of which osseointegrate via the physiologic process of bone remodeling. The mechanism of osseointegration was described first for HA-coated implants (Fig. 5) because their surface geometry is less complex compared to a Screw. Rigid Osseous fixation (osseointegration) was adopted as the clini- cal standard for dental implants at the second National Institute of Health (NIH) consensus conference sponsored by the NIDR in 1987 (Roberts, 1988a,b). Figure 5 illustrates some of the original histological material presented at this meeting that established bone remodeling as the biologi- cal mechanism of Osseointegration. That living bone incorporates bone labels at the interface of miniscrews has been confirmed (Deguchi et al., 2003; Huja et al., 2006). Woven bone and composite bone are formed adjacent to a miniscrew 55 Bone Physiology and Biomechanics Veins Oral Mucosa Arteries Devitalized bone Figure 4. A schematic drawing shows the vascular gradient (pink arrows) through cortical bone in the oral cavity. Postop- eratively, the bone interface of an endosseous implant is devi- talized (light blue) within -1 mm of the implant surface. Figure 5. An HA-coated implant (I) was placed in the femur of a rabbit. After a six-week healing phase, a tetracycline bone label was administered and the specimen was retrieved two days later. The Osseous interface of the same section was examined with fluorescent (FI), brightfield (Bf) and phase contrast (PC) microscopy. A perioste- al callus (P) is noted superiorly, and cutting cones (CC) of osteoclasts are leading the bone multicellular units that are remodeling the dead bone at the interface and the adjacent supporting bone. New second- ary Osteons (S) rigidly connecting the implant to adjacent supporting bone is the mechanism of osseointegration. 56 Roberts and Roberts particularly when it penetrates the cortical bone and extends into the tra- becular bone and marrow. However, no miniscrew studies have demon- strated that true osseointegration occurs, which means that the interface integrates with lamellar bone (Figs. 5 and 6) that remodels within 1 mm of the interface at a very high rate indefinitely (Fig. 7). INTRODUCTION OF MINISCREWS The bone reaction to current miniscrew systems is different than that to osseointegrated implants, so similar rates of success are unlikely. Current miniscrew systems are nonintegrated devices, physiologically akin to the dental implants in use prior to the introduction of osseointegration. Nonintegrated implants were predisposed to instability and a relatively high failure rate because they failed to routinely integrate with supporting bone. Although miniscrews provide anchorage for some clinical prob- lems, their reliability in routine use in orthodontic practice is questionable (Cornelis et al., 2007; Skeggs et al., 2007). Current miniscrew systems were introduced to the American mar- ket with little or no reliable scientific verification by independent inves- tigators. They were approved for sale in the United States via a 510k exemption from the Food and Drug Administration (FDA) because they Were similar to other endosseous implant devices on the market. No Micromotion Oral Mucosa º º º BMU Endosteal Callus Cutting/Filling cone Figure 6. A schematic diagram based on histological specimens, such as that seen in Figure 5, shows the remodeling mechanism of implant healing and integration. 57 Bone Physiology and Biomechanics º Figure 7. A schematic di- agram of an osseointe- grated implant shows that the inner portion (~1mm thick) of the remodeled in- terface is lamellar bone that has undergone prima- ry (P) mineralization. The bone adjacent to the im- plant turns over too rapid- ly to achieve secondary mineralization, so it is more compliant than the more mature lamellar bone supporting it, which has undergone secondary (S) mineralization. Adapt- ed from Roberts (1999). specific research was required for premarketing approval. The 510k exemption was the same mechanism that allowed the introduction of a plethora of clones and new designs for osseointegrated implants after the Brănemark system received FDA approval. To put this into perspective, it is important to remember that the Bränemark osseointegrated implant system was a second generation device approved for clinical use in the United States after more than 20 years of intensive research and clinical studies that included more than 10 years of intensive follow-up. In con- trast, miniscrews were developed largely through clinical trial and error. The current clinical interest in miniscrews has generated a market that hopefully will encourage the research and development of more versatile and reliable TADS. There has been little research to establish the basic bone biology of miniscrew anchorage systems. This deficiency limits their effective routine use in orthodontic practices. At present, clinicians must rely on fundamental principles of bone physiology, biomaterials and biomechan- ics as the most reliable means for selecting supplemental anchorage de- vices. Miniscrew TADs can be used effectively for some challenging problems if the clinician and the patient have realistic expectations. The 58 Roberts and Roberts healing and mechanical adaptation of bone is the physiologic basis for the use of miniscrews as anchorage units in orthodontics and dentofacial or- thopedics. A review of basic principles follows to help clinicians develop an appropriate scientific perspective for evaluating miniscrews. PHYSIOLOGIC BASIS OF ORTHODONTICS AND DENTOFACIAL ORTHOPEDICS The discipline of orthodontics and dentofacial orthopedics is the science of dentofacial adaptation to the application of applied loads, su- perimposed on function. Typical therapy involves fixed and removable appliances, using intraoral and extraoral anchorage, to apply static and/or intermittent loads to the dentoalveolar processes. The therapeutic load- ing changes the dynamic equilibrium of the stomatognathic system. The reactive elements for accomplishing dentofacial correction are the tem- poromandibular joint, PDL, subperiosteal bone surfaces, and maxillary sutures. These mediators of Osseous adaptation must undergo modeling of bone and joint surfaces until the morphology of the face and jaws returns to a dynamic equilibrium consistent with all applied loads (Parr, 1999; Roberts, 1999, 2006; Roberts and Hartsfield, 2004c; Roberts et al., 2004d). All of the associated osseous structures subsequently remodel internally to maintain structural integrity. Changes in the spatial relationship of bones and teeth are physi- ologic manifestations of catabolic and anabolic modeling. Orthodontics is dependent on the adaptive physiology of the periodontium, especially with respect to bone modeling within the PDL and subperiosteal compart- ments (Roberts et al., 2004d). In addition to subperiosteal bone modeling (Fig. 3), facial orthopedics involves sutural responses and temporoman- dibular adaptation. Predictable manipulation of the stomatognathic sys- tem requires a practical knowledge of bone physiology with respect to the biomechanical response to applied loads superimposed on function. When miniscrews are used as intraoral anchorage, their support- ing bone is exposed to the dynamic loading of stomatognathic function. The physiologic implications for miniscrew anchorage involve the influ- ences of both dentofacial biomechanics and systemic calcium metabolism (Roberts, 2005). Clearly, the potential for problems is much greater than is commonly appreciated. For miniscrews to be employed broadly as orthodontic anchor- age, they must withstand a wide range of dynamic loads that generate dentofacial flexure. Subperiosteal flexure is manifest as variable areas of surface compression and tension that control bone modeling (Roberts et 59 Bone Physiology and Biomechanics al., 2004d). The bone and periodontal physiology, associated with the suc- cess and failure of miniscrews, is much more complex than the obvious ability of a miniscrew to resist a static orthodontic load. The demands on endosseous implant anchorage are dictated by the nature of the response to therapeutic loads that are superimposed on function. BONE VASCULARITY Miniscrew success depends on a favorable postoperative osseous response, which in turn is dependent on material properties and shape of the device, surgical technique, and host compatibility (osseous site, sys- temic health and immunological reaction). An important surgical consid- eration is the vascularity of cortical bone sites that are suitable for TADs. The arterial supply for all long bones is via internal (nutrient) arteries. This is true for the thin cortex of the maxilla and the thick cortices of the mandible. The inferior alveolar arteries are the arterial supply for the mandible. The perfusion of blood is from the endosteal to the periosteal surface, as shown by the large pink arrows in Figure 4. There are two nu- trient sources (bilateral inferior alveolar arteries) for the mandible because it evolved from two bones that fused at the midline. The bilateral arterial supply of the maxilla is via the maxillary arteries, which branch into a series of superior alveolar arteries that traverse the cortex in the posterior superior region. With respect to the alveolar processes, the arterial supply of the peripheral cortex is similar: arteries penetrate the cortex, divide into arterioles that then perfuse cortical bone from the endosteal to the perios- teal surfaces via the Haversian and Volkmann’s canals. The principle ve- nous return for all compact bone is via the periosteum (Chanavaz, 1995). An important aspect of bone wound healing is the formation of a subperiosteal callus at the surgical site. Periosteal stripping devitalizes the outer layer of the cortical bone and destroys the osteogenic component of the periosteum. Thus, the vascular invasion of the clot to form a periosteal callus must emanate from undamaged subperiosteal regions peripheral to the mucoperiosteal flap (Roberts et al., 1987; Roberts, 1988a,b). MUCOPERIOSTEAL FLAPS Reflection of a soft tissue flap has long been the preferred surgi- cal method for visualizing the implant site and providing soft tissue for primary closure. With the advent of tomography, computer-assisted to- 60 Roberts and Roberts mography (CAT) scans, and now cone-beam commuted tomography (CBCT), it is no longer necessary to reflect soft tissue to visualize the bone surface. Minimal soft tissue surgery is now the preferred method for placing most implants. Soft tissue over the implant site is removed with a surgical punch or small incision. A hole is drilled in the bone and the implant is inserted as a self-tapping fixture (Fig. 4). It often is desirable to drill a small hole in the bone to guide the direction of a self-drilling miniscrew. Avoiding a mucoperiosteal flap has numerous advantages: de- creased bleeding, minimal devitalization of bone, less disruption of the subperiosteal healing response and diminished postoperative pain (Kuroda et al., 2007; Fortin et al., 2006). The soft tissue punch is a simplified sur- gical procedure that results in a more favorable postoperative course for miniscrew placement and removal. Currently, the trend for screw (root- form) implants is toward flapless surgery (Fortin et al., 2006; Oh et al., 2006; Wittwer et al., 2006), if there is adequate bone and attached gingiva (Flanagan, 2007). IMPLANT HEALING AND OSSEOUS INTEGRATION The capabilities and limitations of bone as a structural material is the product of the specific interaction of the basic genetic and physical factors that determine bone morphology (Fig. 1). Miniscrew installation may appear to be a simple surgical procedure but the bone reaction to it is not. Wounding of bone and the thermal gradients associated with osseous surgery (Davidson and James, 2003) disrupt collateral circula- tion and compromise the diffusion efficiency of the network of canaliculi (Fig. 2; Roberts, 1988). These physiologic problems result in the death of osteocytes and the supporting connective tissue in the vascular spaces of the affected area (Fig. 4). The relatively atraumatic installation of an endosseous screw results in a layer of devitalized bone that is about 1 mm thick. This dead tissue is removed and replaced via a vascular induction and invasion process (Fig. 5), which results in a revascularization process for replacing the devitalized tissue. The fundamental healing process for cortical bone is remodeling, i.e., turnover of dead and damaged bone to healthy osseous tissue. More specifically, the interface between the mini- screw and its supporting bone is determined by static loading (orthodontic anchorage) and functional flexure (micromotion). Interaction of physical and genetic factors relative to wound healing and miniscrew mobility is illustrated in Figure 2. 61 Bone Physiology and Biomechanics During the process of rigid Osseous fixation, devitalized compact bone at the implant interface is resorbed and the resorption cavity is filled with new osseous tissue that connects the original cortical bone with the surface of the implant (Fig. 5). This is the biologic mechanism for achiev- ing osseointegration, which first was demonstrated for HA-coated implants as shown in Figure 5. A similar bone remodeling mechanism for achiev- ing rigid Osseous fixation subsequently was reported for threaded titanium implants (Fig. 6; Roberts et al., 1989b, 1990; Garetto et al., 1995). Tita- nium Screws routinely integrate during an unloaded, postoperative healing phase if the surface of the implant has adequate microtexture and is free of contamination (Roberts et al., 1984, 1987). The Osseous healing response (interface remodeling) is a threat to implant stability for the first month or two postoperatively (Figs. 5 and 6), but once rigid Osseous fixation is achieved, endosseous implants are very stabile and highly resistant to displacement (Fig. 7; Roberts, 1999, 2000b). With regard to orthodontic anchorage, an integrated implant (rigid osse- ous fixation) is equivalent to an ankylosed tooth. Rigidly integrated im- plants do not move relative to basilar bone except when osseointegration fails (Quirynen et al., 1992; Starck and Epker, 1995; Aparicio and Orozco, 1998; Polizzi et al., 2000, Eckert et al., 2001) or the bone interface is frac- tured (Roberts et al., 1984; Roberts, 1999, 2000b). Osseointegration is a stable physiologic condition that can be maintained indefinitely (Roberts, 1999, 2000b; Huja and Roberts, 2004). Failure of an endosseous implant to achieve Osseointegration results in a fi- brous tissue interface (Fig. 8; Piattelli et al., 1998; Brunski, 1999; Esposito et al., 2000), which is an avascular layer of scar tissue that is equivalent to an orthopedic nonunion. A nonunion is a serious healing complication fol- lowing a fracture or osteotomy. A secondary surgical procedure is usually required to remove the fibrous connective tissue, stabilize the segments and graft the defect. It is highly unlikely that a nonintegrated implant will heal (integrate) spontaneously. Excessive motion between an implant and its adjacent bone results in progressive thickening of the fibrous connec- tive tissue interface and decreased stability (Soballe et al., 1992). MINISCREW HEALING Distinguishing between bone modeling (Roberts et al., 2004d) and remodeling (Roberts et al., 2006b) is essential for understanding the bone physiology of miniscrews. Teeth move by anabolic and catabolic modeling (Fig. 3), but endosseous implants heal by remodeling. Wound- 62 Roberts and Roberts Mobility Fibrous Inflammation Connective Tissue Figure 8. A schematic drawing of a miniscrew in cortical bone shows the mechanical factors associated with the variable degree of mobility. Stability of the device is inversely related to the width and distribution of the fibrous connective tissue interface. ing bone initiates a regional acceleratory phenomenon (RAP), which is manifest as an elevated rate of remodeling at the implant interface and up to about 5 mm into the adjacent supporting bone (Figs. 5 and 6; Huja and Roberts, 2004; Yip et al., 2004; Roberts, 2005; Roberts et al., 2006a,b). Postoperative remodeling of a miniscrew interface can result in a close approximation of living bone (Deguchi et al., 2003; Melsen and Carlaberta, 2005; Huja et al., 2006). On the other hand, unfavorable host Compatibility, excessive micromotion, and/or therapeutic overload can re- Sult in increased thickness of the fibrous interface and instability of the miniscrew (Roberts and Roberts, 2007b). There is an inverse relationship between the thickness of the fibrous interface, particularly at the periosteal margin, and the stability of a miniscrew (Fig. 8). Assuming the healing reaction to orthodontic miniscrews is simi- lar to other endosseous screw-type implants, some degree of fibrous tissue encapsulation is the most likely scenario for miniscrews with a polished surface (Piattelli et al., 1998; Esposito et al., 2000). Because of the lack of rigid integration, an encapsulated miniscrew is inherently weak in tor- Sion and pull-out strength (Huja et al., 2006). An increase in the size of the bone defect at the periosteal surface is the most likely mechanism for miniscrew failure. Animal studies of bone adaptation to miniscrews have used bone labels and histomorphometry (Deguchi et al., 2003, Huja et al., 2006). Neither self-tapping nor self-drilling miniscrews osseointegrate, but 63 Bone Physiology and Biomechanics direct bone contact has been noted on some specimens. Increased sur- face roughness is associated with a higher prevalence and degree of os- seointegration (Suzuki et al., 1997; Grizon et al., 2002), so it follows that Smooth titanium screws resist integration. Mechanical testing suggests that miniscrews do not benefit from a healing phase before loading (Chen et al., 2006; Yao et al., 2006). These data are consistent with: (1) nonvital bone providing good initial stability, and (2) compressive loading of the dead bone at the interface inhibiting postoperative remodeling in the line of force. Thus, immediate loading of miniscrews is preferable to a healing phase prior to being engaged for anchorage (Giancotti et al., 2004b; Yano et al., 2006). When a miniscrew is loaded immediately, maximum compression (hoop strain) is along the line of force passing through the nonvital peri- osteal margin. Contrary to osseointegrated implants, an unloaded healing phase is not beneficial for miniscrews serving as TADs. However, addi- tional research is needed to determine the optimal loading window for the various miniscrew designs currently available. Long-term, nonintegrated miniscrews are not physiologically stable structures, but they can serve as adequate anchorage for relatively short-term procedures. Miniscrews have an unpredictable interaction with supporting bone and may or may not be successful in a specific set of cir- cumstances. Despite obtaining a successful result in one patient, implant- ing a miniscrew in the same site in another patient or in a different site in the same patient may result in failure. This lack of physiologic predict- ability is the principal problem restricting the clinical predictability of the currently available miniscrews. They are successful most of the time, but their failure rate still is unacceptable and makes them unreliable for rou- tine use in clinical practice. STABILITY The postoperative stability of an implant depends on the shear resistance of the bone-implant interface (Rohner et al., 2003). Rigid Osseous fixation (osseointegration) with living bone results in the most favorable shear and torsion resistance. An implant may fail to integrate because of Surgical trauma, surface contamination and/or postoperative micromotion (Fig. 8; Brunski, 1999). Current miniscrews are not de- signed to integrate, so they are susceptible to forming a fibrous tissue interface (Piattelli et al., 1998; Esposito et al., 2000), which varies in width and distribution according to the degree of functional micromo- tion and resistance of supporting bone to resorption (Soballe et al., 1992). 64 Roberts and Roberts Even clinically successful (firm) miniscrews move relative to the apical base of bone (Liou et al., 2004). These data are consistent with a fibrous tissue interface and a lack of rigid osseous fixation. Prior to the advent of Osseointegration, a fibrous tissue interface (pseudoperiodontium) was considered a desirable characteristic for pros- thetic implants. Long term, the devices had a relatively high failure rate due to excessive mobility and infection, but some of these endosseous abutments provided satisfactory service for five years or more (Babbush, 1972; Proussaefs and Lozada, 2002; Cappuccilli et al., 2004; DiStefano et al., 2006). The history of nonintegrated dental implants is similar to the current experience with miniscrew TADs. Despite many successful case reports, miniscrews are unpredictable; numerous authors have addressed their substantial risks and relatively high failure rates (Cheng et al., 2004; Kravitz and Kusnoto, 2007b; Kuroda et al., 2007). Important factors for the initial stability of miniscrews are the thickness of the cortical plate, density of osseous support, and the degree of thread penetration into adjacent bone (Fig. 8). The basic principle is the same as that for joining materials with screws rather than nails when a structure is to be loaded cyclically. Threads have increased resistance to surface shear, which is particularly important for dynamic functional load- ing. With respect to rigidly integrated screws, the transfer of force to bone depends on thread design. Symmetrical threads are more favorable than asymmetric threads for bone development and maintenance (Roberts et al., 1989b). Furthermore, finite element calculations demonstrate that the maximum principal stress is at the tips of the threads, which are the areas that show the highest rates of bone remodeling (Chen et al., 1995, 1999). Miniscrews are mechanically retained devices. Relatively high success rates have been reported with nonintegrated miniscrews (Tseng et al., 2006; Kravitz and Kusnoto, 2007b), but success is a relative term. Numerous reports have focused on the risks and potential compromises associated with miniscrew anchorage (Miyawaki et al., 2003; Cheng et al., 2004; Park et al., 2006; Kravitz and Kusnoto, 2007b), but a consensus on what actually constitutes success has been elusive. HOST COMPATIBILITY Host compatibility to miniscrews is unclear, but the physiologic mechanisms probably are similar to those for endosseous prosthetic im- plants (Keller, 1998; Hedia and Mahmoud, 2004). Many factors have been implicated such as genetics, osseous geometry of the site, inherent 65 Bone Physiology and Biomechanics remodeling activity, metabolic health of the patient, functional loading, and vigor of the RAP associated with postoperative healing (Frost, 1992; Roberts et al., 2006a,b). The physiology of the host response is an impor- tant area of TAD research that has received little attention. Bone remodeling associated with wound healing is an inherent physiologic response that is driven by the localized production of cyto- kines. After healing is complete, bone remodeling of the Osseointegrated interface appears to be mechanically driven (Garetto et al., 1995; Chen et al., 1995, 1999). Reportedly, bone is in direct contact with at least a portion of the surface of some miniscrews (Melsen and Carlaberta, 2005), but there is no reliable data on the long-term maintenance of Osseous Sup- port. Genetic predisposition to miniscrew failure may be related to the intensity of the bone resorptive response following surgical placement. At present, there is no direct evidence for a genetic link to miniscrew success. However, clinical experience has demonstrated that multiple, unexplained failures often occur in the same patient. This observation suggests that there may be a genetic predisposition to miniscrew failure. Schierano and colleagues (2005) have proposed that Interleukin-1 Beta (IL-13) is an important factor in miniscrew host compatibility similar to the mechanism that has been proposed for dental implants. Remodeling of necrotic bone adjacent to the surface of an implant is physiologically similar to the undermining resorption mechanism that initiates tooth movement. Undermining resorption is required to remove alveolar bone adjacent to a necrotic PDL that is in the path of tooth move- ment. Evidence for IL-13 control of the undermining resorption process is derived from its involvement in the expression of external apical root resorption (EARR). Clinical and animal data are consistent with EARR being secondary to fatigue failure of the root of a tooth associated with a prolonged lag phase at the initiation of the tooth movement response (Al- Qawasmi et al., 2003, 2004, 2006; Hartsfield et al., 2004; Roberts et al., 2004a). A similar IL-13 mediated, resorptive response (Schierano et al., 2005) may be involved in the postoperative remodeling of dead bone at the bone interface of a miniscrew. An initial investigation to test the hypothesis of genetic predispo- sition to miniscrew failure would be to determine whether there is a cor- relation between EARR and the failure rate of miniscrews in the same pa- tient. If a correlation is found, specific studies of candidate genes related to root resorption would be indicated (Al-Qawasmi et al., 2003a, 2003b, 2004, 2006; Hartsfield et al., 2004; Roberts et al., 2004a). 66 Roberts and Roberts MINISCREW FAILURE Nonintegrated miniscrews have a high risk of failure in some intra- oral sites (Miyawaki et al., 2003; Cheng et al., 2004; Kravitz and Kusnoto, 2007b; Kuroda et al., 2007). Loss of stability, often manifest as exfolia- tion of the miniscrew, usually is noted during the first three to four weeks of the postoperative healing period. Immediate loading may contribute to a lower failure rate because it is more difficult for osteoclasts to remove bone resisting the displacement of the TAD. In contrast to Osseointegrated implants, preserving a nonvital bone interface around miniscrews may be advantageous for anchorage stability. Some immediately-loaded minis- crews are firmly retained, and Chen and colleagues (2006) have reported an average removal torque of 8.7 N-cm. Substantial numbers of unloaded miniscrews (~ 20%) fail to be retained in bone. Huja and colleagues (2006) reported on the six-week postoperative period for self-drilling, tapered miniscrews. After inserting 102 miniscrews (6 to 8 mm in length) in multiple intraoral sites in dogs, 20 failed (were loose or lost) after six weeks. Most of the failures (16) oc- curred in the maxillary and mandibular anterior areas, of which the man- dibular anterior area was the most problematic (all 12 miniscrews failed). These data suggest that the relatively thin cortices in the anterior segments are poor sites for miniscrews. A contributing factor may be the increased functional flexure of a cantilever bone such as the dog jaw. Excessive micromotion may be generated by masticatory function and/or extraneous loading due to rubbing against the sides of the cage or gnawing the paws in response to intraoral irritation. The latter may be important clinically because some patients report that they frequently test intraoral miniscrews with their fingers “to see if they are loose.” For miniscrews that survived a six-week healing period in dogs, there was no significant difference in pull-out strength compared to that of miniscrews immediately post-operative (Huja et al., 2006). For these “successful” screws, bone contact at the interface ranged from 79% to 95% (Huja et al., 2006). It is important to emphasize that the miniscrews were tapered and that there was no evidence that rigid osseous fixation (osseointegration) had occurred. Postoperative failure of miniscrews probably is due to interface remodeling of the peripheral cortex. The remodeling mechanism of postoperative healing, to replace devitalized bone at the implant inter- face (Fig. 6), is well documented (Roberts, 1989a; Brunski, 1992; Ga- retto et al., 1995; Huja et al., 1998). The bone supporting all endosseous implants remodels postoperatively, but only portions of the surface are 67 Bone Physiology and Biomechanics uncovered by resorption at any point in time (Fig. 7; Roberts, 1997). If there is adequate bone to support the implant, as its interface is progres- sively remodeled, the implant will remain stable despite immediate load- ing. The most critical period is about three weeks after the miniscrew is placed. Cutting cones to remove the devitalized interface emanate from the endosteal surface and progress to the periosteal surface (Fig. 5; Rob- erts, 1988). About three weeks postoperatively the most peripheral bone is removed near the periosteal surface. If there is inadequate osseous tis- sue supporting the remainder of the implant interface, the miniscrew will displace in the direction of the applied load (Roberts et al., 1984). Under these circumstances, the miniscrew becomes mobile and may exfoliate. In clinical practice, a common scenario is evolving relative to miniscrew failure. Postoperatively, patients experience little pain and dis- comfort; no problem is evident until about three weeks after the device is placed and loaded. An initial sign of a problem is the abrupt sensa- tion that the miniscrew has moved within the bone. These observations are consistent with a loss of osseous support subsequent to remodeling of the periosteal interface of the miniscrew. A study of bilateral miniscrews implanted in the same patient, with one side immediately loaded and the other side unloaded, would be helpful in determining the importance of the loading protocol relative to miniscrew success or failure. Another concern is pain that can be caused when the TAD is load- ed with therapeutic force. The pain probably is related to communication of the fibrous interface with innervated structures such as PDL or neuro- vascular bundles. Painful miniscrews should be removed and replaced with other TADs as needed. LIMITATIONS OF NONINTEGRATED MINISCREWS Numerous clinicians have reported on the efficacy of using mini- screws for orthodontic anchorage (Kanomi, 1997; Maino et al., 2005; Melsen and Carlaberta, 2005). Several reports have described major fa- cial changes due to retraction of incisors and impaction of molars achieved with miniscrew anchorage (Ko et al., 2006; Choi et al., 2007; Paik et al., 2007; Xun et al., 2007). To date there are no well-controlled clinical trials of miniscrew anchorage performed by independent clinicians who have no vested interest in the products being used. Miniscrews are used widely as TADs for orthodontic tooth movement, but contrary to osseointegrated implants, they have yet to be established as effective orthopedic anchors. 68 Roberts and Roberts Having used a variety of miniscrews for orthodontic anchorage, my colleagues’ and my experience has been that the failure rate for most current miniscrew devices is excessive. Failures are uncomfortable for the patient, delay treatment and may result in therapeutic compromises that are difficult to correct. More reliable TADs with a broader range of appli- cations are needed. Important horizons for second generation devices are serving as anchorage for orthopedic therapy and as temporary prosthetic replacements for missing teeth. BONE BIOMECHANICS An orthopedic experiment in rabbits published in the orthodon- tics literature used endosseous bone fixtures (2 mm diameter miniscrews) to test the bone modeling and remodeling responses to dynamic flexure (Figs. 9 and 10; Roberts et al., 1984). Two mm diameter, acid-etched miniscrews routinely achieved rigid osseous fixation (osseointegration) following a six-week unloaded healing phase. It is important to remember that all living bone is functionally loaded by musculoskeletal activity. The term “unloaded” in the dental implant field refers to a lack of supplemental masticatory and/or orthodontic loading (Roberts et al., 1989a,b; Morais et al., 2007). The rabbit femur experiment discussed above used rigidly inte- grated implants to test two hypotheses: 1. a basic premise of orthodontics therapy, i.e., continuous, static force results in movement of a tooth through bone along the line of force; and 2. compressive loading (more concave flexure) of a bone surface results in anabolic modeling (bone formation). Relative to the first hypothesis, the static loading concept of ortho- dontics was in conflict with a large body of orthopedic literature that held that static loads are ineffective in eliciting a bone response; bones only respond to dynamic loads. However, the compressive load of 1N applied between the implants is similar to orthodontic mechanics. It is a static load superimposed on function, which is a dynamic load that is the sum of the two (Roberts et al., 1984). The second hypothesis tested Frost’s “laws of bone flexure” (Frost, 1982) by applying a 1N compressive load between two rigidly integrated (ankylosed) titanium miniscrews in rabbit femora (Roberts et al., 1984). The spring was oriented along the neutral axis of the bone or lateral to it (Figs. 9 and 10). The anabolic modeling response emanated 69 Bone Physiology and Biomechanics Figure 9. Top: Miniscrews were placed along the neutral axis (thin red line) that is perpendicular to the plane of the radio- graph. Bottom: A coil spring delivered opposing compressive forces (yellow arrows) in the plane of the implants. The result- ing bone flexure is shown by the curved dashed line compared to the solid red one. Under these conditions, bone apposition (anabolic modeling) occurs superiorly in the plane of the im- plants (red arrow). Adapted from Roberts (1984). from the spot on the bone surface that was subjected to maximal concave flexure. Thus, anabolic modeling occurs in subperiosteal spaces where bone is exposed to surface compression by dynamic loading exceeding about 2500 microstrain (Frost, 1982; Roberts et al., 1984; Rubin and Lan- yon, 1985; Roberts, 2005). When the bone surface is loaded along the long axis of the bone, the hypertrophic reaction is in the plane of the abut- ments (Fig. 9). If the implants are loaded lateral to the long axis of the bone, anabolic modeling is directed laterally (Fig. 10). 70 Roberts and Roberts Figure 10. Top: In contrast to Figure 9, miniscrews were placed lateral to the neutral axis (red solid line) and loaded with a simi- lar compressive force. The direction of curvature of the bone is shown by the dashed red line compared to the solid one. These mechanics resulted in surface compression (yellow arrows) and anabolic modeling in the lateral direction (red arrow). Bottom: The hypertrophic reaction extended to the inferior border of the femur of the same specimen. Adapted from Roberts (1984). Considering these data in a clinical perspective, bone model- ing and remodeling are controlled by dynamic (intermittent) loading in repetitive short-term cycles (Roberts et al., 2004d, 2006a). In contrast, most Orthodontic therapy is accomplished by long-duration intermittent or Static loads applied by fixed appliances. After orthodontic appliances are 71 Bone Physiology and Biomechanics activated, the patient progressively returns to normal function. Mastica- tory and parafunctional loading involves applying intermittent forces and moments that are several orders of magnitude greater than the static ther- apeutic loads delivered by orthodontic appliances. Therefore, the static loads used for orthodontic and dentofacial orthopedic therapy actually are dynamic loads because they are superimposed on function (Roberts, 2005). Thus, the orthodontic and orthopedic literatures are consistent when func- tional loading is considered (Roberts et al., 1984, 2004d; Roberts, 2005). The advent of osseous anchorage devices (TADs) has challenged orthodontists to expand the envelope of traditional mechanotherapy. Op- timizing clinical capability requires an advanced level of understanding of the osseous biomechanics of the periodontium. Moving healthy teeth into alveolar defects generates new bone and attached gingiva (Roberts et al., 1990, 1996; Roberts, 1999). Implant anchorage expands the opportunities to generate new periodontium orthodontically, as opposed to relying on Surgical augmentation procedures. Tooth movement involves distinctive osseous modeling responses adjacent to the PDL and along alveolar bone surfaces. It is important for orthodontists to distinguish orthodontic from orthopedic biomechanics rel- ative to the PDL and subperiosteal compartments of alveolar bone on the labial and lingual surfaces (Roberts et al., 2004d). The PDL is a unique, genetically-defined peri-Osseous tissue with no counterpart anywhere else in the body (Roberts, 2005). It is a heavily loaded, compliant tissue con- necting two relatively rigid osseous structures. If a tooth is displaced by therapeutic and/or functional loading, the width of the PDL is restored by catabolic and anabolic bone modeling. Modeling of the alveolus also is controlled by flexure at the PDL/bone interface (Grimm, 1972; Tanne et al., 1987). Flexural loading (“bone bending,” Grimm, 1972; Tanne et al., 1987; Meikle, 2006) controls modeling of alveolar bone in the subperi- osteal compartment of the periosteum within the inner cambium (osteo- genic) layer (Roberts et al., 2004d). PERIODONTAL BIOLOGY Basilar bone of the maxilla and mandible are determined genet- ically, but the dentition is the raison d'être for the periodontium. The epithelial attachment, PDL, alveolar process and attached gingiva are all induced by the development and eruption of teeth. No periodontium forms if teeth are missing and it atrophies when teeth are lost. Once 72 Roberts and Roberts formed, the maintenance of periodontal support tissues is dependent on the healthy functional loading of the dentition. Figure 11 shows the dentition of a 55-year-old female (Case 1) with an acquired malocclusion secondary to the bilateral loss of posterior occlusal stops. A compromised removal partial was constructed to restore her dentition. She had severe atrophy of the edentulous areas due to disuse atrophy and the mucosal loading of the prosthesis (Fig. 12). Figure 11. Case 1. Intraoral photographs show an acquired malocclusion sec- ondary to the loss of bilateral posterior occlusal support. The patient was dis- Satisfied with the esthetics and function of her dentition. When a tooth is extracted, there is a postoperative healing reaction that fills the extraction site with woven bone. The bone in the edentulous area remodels to lamellar bone organized into a peripheral cortex with internal trabecular bone. Eventually, the alveolar bone and gingiva in the edentulous space atrophy because of a lack of optimal loading (disuse at- rophy). For relatively small spaces, only a portion of the alveolar process resorbs because it continues to be loaded by adjacent teeth. Over time, large edentulous spaces may experience a complete atrophy of the alveolar Process and attached gingiva (Fig. 12), particularly if the patient is experi- encing negative calcium balance. 73 Bone Physiology and Biomechanics Figure 12. Case 1. A radiograph of the mandibular left posterior segment reveals the bone atrophy in the edentulous space me- sial to the third molar. The red arrows on the teeth are opposing forces and moments that load the edentulous bone surface in compression (yellow arrows). This scenario results in anabolic modeling in the direction of the blue arrow. The principle of disuse atrophy is well understood, but few clini- cians are aware that the same principles of biomechanics that caused atro- phic loss of the periodontium can be reversed to regenerate healthy dental support in an edentulous area (Roberts et al., 2004d). In that both alveolar bone and attached gingiva can be regenerated therapeutically, orthodontic closure of an atrophic edentulous space is a viable option (Roberts et al. 1990; Wehrbein et al., 1990). Predictable tissue engineering in atrophic edentulous areas requires effective use of osseous flexure to provide ad- equate subperiosteal bone formation to receive a moving tooth (Roberts et al., 2004d). PREPROSTHETIC ALIGNMENT The treatment plan for Case 1 (Figs. 12-19) was to open the bite. move the mandibular anterior segment anteriorly to establish a bilateral Class I canine relationship and achieve optimal incisal coupling. Pre- prosthetic alignment of the entire mandibular dentition required rigid Osseous anchorage. Miniscrews are not a viable option for this type of acquired malocclusion because placing them between the roots of teeth 74 Roberts and Roberts Figure 13. Case 1. Mesial translation and intrusion of a mandibular left third molar is accomplished with direct anchorage from a retromolar implant. A. At three months, the initial mesial movement is accomplished on a 0.018” stain- less steel archwire with a compressed NiTi coil spring between the tooth and the implant. B: At six months, the third molar has moved about 3 mm with the Same mechanics. C. At nine months and after about 5 mm of crown movement, an uprighting spring (.018 x ,025” TMA) slides along the wire to move the roots mesially. D. At 16 months, mesial translation of the third molar has resulted in anabolic modeling of the bone surface (yellow arrow). New immature woven bone (*) is noted on the mesial of the molar Would block the path of tooth movement and introduce an undesirable intrusive component on the mandibular molars (Fig. 19). Insertion into the atrophic space would inhibit orthodontic regeneration of bone and at- tached gingiva (Figs. 15C and 16). Preprosthetic alignment of the com- plex malocclusion in three dimensions required osseointegrated implants as prosthetic abutments or as retromolar fixtures for indirect anchorage (Figs. 14-16). 75 Bone Physiology and Biomechanics Figure 14. Case 1. A series of panoramic radiographs document treatment prog- ress. A: Initial pretreatment view. B: A mandibular right implant-supported crown opens the vertical dimension of occlusion, and a mandibular left retro- molar implant is anchorage for mesial translation and intrusion of the adjacent third molar. C. Preprosthetic orthodontic treatment is completed. D: Fixed par- tial dentures were placed bilaterally in the mandibular arch. Following delivery of the left fixed partial denture, the third molar developed a periapical lesion that required endodontic treatment. 76 Roberts and Roberts *º- Figure 16. Case 1. Superimposition of tracings of the panoram- ic radiograph series (Fig. 14) shows that both the canine and third molar were moved me–sially with direct anchorage from the retromolar implant. Note the unilateral anabolic modeling in the atrophic edentulous area as the third molar is moved me- sially and intruded. *H Figure 15. Case 1. A series of intraoral photographs documents the preprosthetic orthodontic treatment of the left side of the mandibular arch. A: Initial view with a black line and arrow *Vealing the depth of an atrophic edentulous space B. Sixteen months progress: note that the edentulous defect is filling with *W periodontium as the third molar is move mesially and in- "uded. C. The preprosthetic finish shows increased attached gingiva on the mesial of the third molar, which borders on the residual edentulous space. Adapted with permission from Rob- erts (1999). 77 Bone Physiology and Biomechanics The fundamental orthopedic principles demonstrated by load- ing implants in a rabbit femur (Figs. 9 and 10) are applicable clinically (Fig. 12) as demonstrated by Case 1 (Figs. 13–19). If teeth adjacent to an atrophic edentulous area are healthy, the space can be closed or reduced in size in preparation for restorative dentistry. Applying equal and op- posite equivalent force systems to healthy teeth on either side of an atro- phic defect (Fig. 12) results in surface compression along the periosteal surface in the depth of the defect. Similar to the rabbit bones (Figs. 9 and 10), subperiosteal surface compression results in anabolic modeling to fill the defect (Fig. 16). A series of clinical radiographs (Figs. 15 and 17) documents the intrusion and mesial translation of the mandibular third molar into an atrophic defect secondary to loss of the first and second molars > 20 years ago. New bone and attached gingiva are generated as on the right side, i.e., an increase in the vertical dimension of occlusion via an implant-supported crown, a Class I canine relationship, and incisal coupling (guidance). B: The objectives of preprosthetic alignment were achieved on the left side, i.e., mandibular third molar occluding with the maxillary first molar in a full cusp Class II relationship, a Class I canine relationship, and incisal cou- pling. C. Right side with finished prostheses and a maxillary bite plate to retain the vertical dimension of the occlusion. D: Left side with a finished mandibular prosthesis and a Hawley bite plate with buccal clasp to control the overjet of the maxillary second premolar and first molar. 78 Roberts and Roberts the molar is moved mesially to close the space (Figs. 15-17; Roberts, 1999, 2005; Roberts et al., 2004d). Tissue engineering with orthodontics is an important clinical application of basic and applied principles of oral development, bone physiology and biomechanics. In comparing Figures 12 through 14, it is apparent that the man- dibular left third molar and second premolar were not moved together with equal and opposite force systems. In fact, the second premolar moved mesially, as evidenced by the pattern of bone formation noted in Figure 14B. Thus, the retromolar implant was used as direct anchorage to move the entire left buccal segment mesially to achieve a Class I canine rela- tionship and full cusp Class II relationship between the molars (Figs. 14C and 15C). During the period of active mechanics, it was necessary for the patient to wear an interocclusal orthotic to establish the desired vertical dimension of occlusion. The orthotic was a modified Hawley maxillary bite plate with interocclusal acrylic. The clinical documentation (Figs. 13-15) demonstrates that uni- directional tooth movement of the third molar into the edentulous area provided sufficient compressive loading to achieve a tissue engineering response (Figs. 15C and 16). Anabolic bone modeling and gingival hyper- trophy filled the defect with new periodontium to support the third molar in what was previously an atrophic edentulous space (Fig. 12). ANABOLIC MODELING TO CLOSE SPACES With respect to bone surfaces, the biomechanics principles for subperiosteal anabolic modeling (bone formation) appear to be the op- posite of that for the PDL response, but in fact it is a manifestation of the same physiologic response. The periodontium of a healthy tooth actually is a hydraulic system in which the fluid of the PDL is sealed off from the oral cavity by firmly attached gingiva (Picton and Wills, 1978; Picton, 1988). Thus, tooth displacement compressing the PDL applies a normal (perpendicular) force to the bone, resulting in a tensile loading of the sur- face adjacent to the area of maximal compression. The tensile flexure due to PDL compression results in bone resorption. In effect, tooth movement generates catabolic modeling at the PDL-bone interface of the affected area of the alveolus. The labial or lingual plate of bone flexes in the di- rection of tooth movement, thereby generating subperiosteal compression and anabolic modeling (bone formation; Roberts et al., 2004d). 79 Bone Physiology and Biomechanics _ Pretx – Post Ortho - Post Pros Figure 18. Case 1. Superimposed cephalometric tracings document the opening of the vertical dimension of occlu- sion and the preprosthetic alignment of the mandibular dentition. Films were exposed pretreatment (Pretx, black), after completion of preprosthetic alignment (Post Ortho, red), and following completion of prosthetic treatment (Post Pros, green). Compression along the subperiosteal surface elicits bone forma- tion (Figs. 9 and 10; Roberts et al., 1984). The latter is one of the “laws of orthopedic flexure” originally described by Frost (1982). Figure 12 is a pretreatment radiograph of an atrophic edentulous space mesial to a mandibular third molar. When the tooth mesial to the space (second pre- molar) and distal to it (third molar) is loaded with a force and a moment (equivalent force system; Smith and Burston, 1985) to close the space. the subperiosteal bone surface between the teeth is loaded in compres- sion. This mechanism results in anabolic bone modeling (formation) ahead of a moving tooth (Fig. 13). However, as previously discussed, a 80 Roberts and Roberts ------- Figure 19. Case 1. Mandibular tracings corresponding to Fig- ure 18 were superimposed on the internal symphysis, inferior alveolar canal and implants. unidirectional force and moment can achieve an asymmetric anabolic modeling response as shown in Figure 16. AS bone is formed to fill the defect, new attached gingiva is gen- erated (Figs. 15C and 17B) by proliferation and invasion of competent subepithelial connective tissue. The latter reaction is dependent on the periodontal health of the tooth or teeth moved into the space. The bio- logic width of the soft tissue attachment is very important, particularly the collagen fibers apical to the base of the epithelial attachment (Roberts et al., 2004d. Roberts, 2005). When the connective tissue attachment to the teeth is compromised by apical migration of the epithelial attachment, the potential for generating new periodontium is inhibited (Roberts et al., 2004d. Roberts, 2005). Periodontally compromised teeth can be treated orthodontically if the active infectious process of periodontitis is controlled. Periodontitis is an infection of the subperiosteal space that compromises anabolic model- ing by inhibiting the formation of osteoblasts (Roberts et al., 2004d). In the presence of periodontitis, physiologic drift of the alveolar plate ahead of a moving tooth does not occur. Simultaneous resorption along the PDL . periosteal surfaces results in loss of the entire alveolar crest (Roberts. 005). Once the infectious etiology of periodontitis is controlled, ortho- dontics is a viable option, but treatment objectives must be realistic be- *use the subepithelial connective tissue attachment to the teeth is dam- aged (Roberts et al. 2004d). Moving periodontally compromised teeth 81 Bone Physiology and Biomechanics into an atrophic defect is not recommended because of inadequate biologic width of the periodontal attachment. Migration of the epithelial attach- ment and further compromise of the periodontal support is likely. In large measure, the viability of generating new bone and attached gingiva in atro- phic alveolar defects (Fig. 16) depends on a healthy periodontium, as de- fined by a normal band of connective tissue fibers attaching the gingiva to the cervical region of the root (Roberts et al., 2004d; Roberts, 2005). PERIODONTIUM REGENERATION VS. BONE AUGMENTATION Atrophic defects can be augmented surgically with onlay grafts. The procedure is effective for increasing the width of an edentulous de- fect, but it is difficult to achieve an increase in height. In selected patients, distraction osteogenesis can achieve an increase in height, but multiple surgical procedures may be necessary (Saulacic et al., 2007). When peri- odontally healthy teeth are moved into an atrophic defect, the subperios- teal surface of the concave osseous defect is loaded in compression (Fig. 12). The tooth is not moved into an Osseous void because the biomechan- ics of space closure generates new bone and attached gingiva ahead of the moving roots (Figs. 13-16). Following preprosthetic alignment (Figs. 17A and B), periodontal crown-lengthening surgery was performed in the max- illary anterior region, the dentition was bleached, and the final mandibular prosthesis was constructed (Roberts, 1999). Case 2 presents an adult female patient requiring preprosthetic orthodontic therapy to move teeth into three types of atrophic areas: (1) natural atrophic ridge, (2) successfully augmented edentulous space, and (3) an alveolar defect in which surgical augmentation had failed (Fig. 20). Orthodontic treatment was successful in moving teeth into the natural atro- phic ridge and alveolar defect where the bone graft had failed. However, it was very difficult to move a tooth into the posterior maxillary area that had been augmented successfully with a bone graft. The treatment results for this patient show that bone augmentation prior to orthodontics is not indicated because most mineralized grafts (bone and/or biomaterials) turn over into natural bone very slowly, if, in fact, they form viable bone at all. Osteoclasts have difficulty removing large areas of dead bone and bioma- terials. Thus, the resorption resistant material in the path of tooth move- ment resisted root movement, so there was excessive tipping of the crown of the tooth and lateral root resorption was noted (Fig. 200). 82 Roberts and Roberts Figure 20. Case 2. A: At the initial evaluation, the patient presented with a his- tory of a successful sinus lift and onlay bone augmentation (S), a failed augmen- tation bone graft (F), and a mobile distal abutment on a fixed prosthesis (M). B. Two osseointegrated implants were placed for orthodontic anchorage – one in the mandibular right retromolar region (R) and the other in the maxillary left tuberosity area (T). The retromolar implant was direct anchorage (DA) for me- sial movement of the first premolar and canine and indirect anchorage (IA) to upright the mandibular right third molar. C. The maxillary incisors were moved into the atrophic area (a) following the failed augmentation graft, and the maxil- lary first premolar was moved distally into the area that was grafted successfully (b). D. The realigned mandibular right third molar was a satisfactory abutment (a) for a 5-unit, fixed partial denture. The maxillary incisors were readily moved into the atrophic defect, thereby creating a pontic space (p) between the left lateral incisor and the canine. Only limited success was achieved in moving the maxillary left first premolar into the bone grafted space, and it resulted in substantial lateral root resorption (r). When managing edentulous spaces in multidisciplinary treatment planning, orthodontics should be a prospective consideration (Goodacre et al., 1997). Tooth movement to close or decrease the width of a Space re- quires healthy teeth that can be moved into unoperated edentulous spaces. If an edentulous space is augmented surgically, it is wise to place implants in the space rather than attempt to move teeth into it. Vital bone is not an *sential prerequisite for receiving an implant, but it is necessary for an Optimal osteoclastic response of removing bone in the path of tooth move- ment. 83 Bone Physiology and Biomechanics DIRECT AND INDIRECT ANCHORAGE Facial morphology, parafunctional habits and the treatment plan are important considerations when selecting TAD mechanics for mesial translation of premolars and molars. Direct anchorage is when the de- sired force is attached to and directly resisted by the TAD (Fig. 21A). In- direct anchorage refers to stabilizing a tooth or teeth in the arch with a wire from a TAD, and then using the dental unit(s) as anchorage to move other teeth (Fig. 21B). Miniscrews placed between the roots of mandibu- lar premolars to move molars mesially are effective direct anchorage units if it is desirable to intrude the molars (Fig. 21A). However, most partially edentulous malocclusions have a decreased occlusal vertical dimension requiring extensive correction of the mandibular dentition in three dimen- sions (Figs. 18, 19 and 21A). The four cases presented in this chapter demonstrate the effectiveness of using retromolar implants for direct and indirect anchorage (Fig. 21B). Case 1 (Figs. 11-19) is an example of direct anchorage in which the mandibular implant-supported prostheses were used to anchor coil springs to move the dentition mesially and open the vertical dimension of the oc- clusion. Case 2 (Fig. 20) is an example of Osseointegrated implants used for both direct and indirect anchorage. Case 3 (Fig. 21) is that of an adult male with a missing mandibular first molar and a closed vertical dimen- sion of occlusion. The line of force from a miniscrew placed between the roots of the premolars would have resulted in an undesirable intrusion of the molars and maxillary incisor occlusal trauma. The patient was treated successfully with indirect anchorage from a retromolar implant (Roberts et al., 1994). The patient presented in Case 4 (Figs. 22–28) benefited from the use of retromolar osseointegrated TADs to move maxillary and man- dibular buccal segments mesially to close first premolar extraction sites. The use of a retromolar TAD to move the mandibular buccal segments mesially is a well established form of indirect anchorage (Fig. 22). If a patient has an adequate overbite, the mandibular arch, particularly if Sup- ported by retromolar implants, can provide adequate anchorage to move maxillary molars mesially to close space (Fig. 25A; Roberts et al., 1994). Implant-supported prostheses and retromolar implants are essen- tial for partially edentulous malocclusions in patients with a closed ver- tical dimension of occlusion (Figs. 19, 21A and 22). It is unlikely that any of these patients could have been treated successfully with mini- screws placed between the roots of teeth because the mechanics produce intrusive components that would aggravate the malocclusion and result in 84 Roberts and Roberts incisal trauma (Fig. 21A). The patient presented in Case 4 had a history of maxillary incisor resorption secondary to occlusal trauma, which was related to inadequate posterior occlusal stops and clenching (Fig. 26B). jº |) |A | Z My A. W Cover screw |c ºsse; Ti Implant º º º & B º º * . § º Figure 21. Case 3. A: An adult male with a closed vertical dimen- Sion of occlusion had a missing mandibular first molar and the sec- ond and third molars were tipped mesially. If a miniscrew (green dot) is placed between the second and first premolar roots to serve as direct anchorage, the line of force (red dashed arrow) results in a desirable mesial component (red solid arrow) but an undesirable intrusive component (yellow arrow). Intruding the molars out of occlusion results in incisal trauma (yellow circle). B: Indirect an- chorage with a retromolar titanium (Ti) implant and a TMA anchor- age wire extended to the second premolar is a superior mechanism for mesial movement of mandibular molars in patients with a closed Vertical dimension of occlusion. The intrusive component of force is controlled by a steel ligature connecting the anchorage wire to the third molar (*). 85 Bone Physiology and Biomechanics Because of their limited stability in bone, miniscrews usually are employed as direct anchorage units, meaning the line for force passes through the head of the TAD (Fig. 21). This form of direct anchorage is effective for intrusion of molars and retraction of anterior maxillary seg- ments, but may be a problem for some patients. Protracting mandibular molars with a miniscrew placed between premolars results in an intrusive component on the molars. This vector of force is dictated by placing the miniscrew sufficiently apical to access adequate interradicular bone. The line of force may be desirable for patients with extruded molars, an ante- rior open bite, and/or hyperdivergency. However, it is inappropriate for patients who have hypodivergency, deep-bite and/or a clenching history (Figs. 21A and 22). Indirect mechanisms that use rigid implant anchorage in the palate and retromolar areas can be used to reposition the entire dentition in three dimensions. For example, the TADs can be used to open or close the bite while simultaneously retracting incisors or protracting molars (Figs. 16, 18 and 28). Because the osseointegrated TADs are located outside of the arches, they are very reliable and pose minimum risk to the patient. Rigidly integrated retromolar implants are loaded immediately because they are not in occlusion. There have been no failures of retro- molar anchorage implants when the surgeon followed the manufacturer’s protocol. If an osseointegrated fixture fails, it usually is due to a lack of integration during the healing phase (early failure) of palatal or prosthetic fixtures. These failures rarely compromise a patient’s treatment because the orthodontist is aware of the failure before critical mechanics are em- ployed. Miniscrew failures usually are late failures, occurring months af- ter initiation of critical mechanics. Late failures are more likely to result in treatment failures and compromised outcomes. CLOSED VERTICAL DIMENSION OF OCCLUSION Case 3 is that of a 34-year-old female (Fig. 22) who presented with a four-year history of fixed orthodontics therapy to correct “an un- comfortable bite.” The problem originally was diagnosed as a bimaxil- lary protrusion and the four first premolars were extracted. After four years of sliding wire mechanics failed to close the extraction sites, the patient sought a second opinion because she was informed by another practitioner that she was experiencing maxillary incisor root resorption. At transfer, a progress cephalometric tracing demonstrated that the en- tire maxillary and mandibular dentition had moved mesially about 5 mm 86 Roberts and Roberts Figure 22. Case 4. Left: An adult female with a chief compliant of maxillary incisor root resorption had a four-year history of fixed orthodontic treatment that failed to close four first premolar extraction sites. Right: Superimposition of trac- ings from the original head plate (solid line) and cephalogram at transfer (dashed line) reveal that the mandible, chin and entire dentition have moved mesially. (Fig. 22). Questioning of the patient, clinical examination, and a review of the records (Figs. 22-25) revealed that she was an habitual clincher. who braced her tongue against the dentition to alleviate jaw pain.” The discomfort apparently was secondary to overloading the condyles due to a Poor bilateral posterior occlusion (Fig. 23). The tongue bracing expanded the maxillary arch until it was almost in a full buccal crossbite (scissors bite) relationship (Fig. 24). The previous orthodontist had attempted to °ontrol the maxillary expansion with a transpalatal arch. Following the transfer of care, the treatment plan was redirected to correcting the etiology of the problem rather than treating the symp- toms. In a series of myofunctional therapy sessions, the patient was in- structed to relax her tongue and avoid occlusal contact except when eat- "8. Once the tongue bracing was corrected, the maxillary transpalatal 87 Bone Physiology and Biomechanics Figure 23. Case 4. The pretreatment panoramic radiograph shows a missing maxillary right first molar and an impacted third molar (red circle). X marks the first premolars that were extracted. Right and left intraoral photographs reveal the patent extraction sites after four years of orthodontic treatment. arch was removed. Mandibular retromolar implants were placed bilateral- ly, .019°x.025” titanium alloy wires (TMA) were attached to the implants, and the anchorage wires were extended mesially to stabilize the mandibu- lar canines (indirect anchorage). The anchorage wires were secured to the first molars with steel ligatures to prevent apical buckling (Roberts et al., 1994; Schneider et al., 2006). Sliding wire mechanics were used to trans- late the mandibular buccal segments mesially to close the extraction sites. The maxillary extraction sites were closed with sliding wire mechanics using the overbite as anchorage. Anchorage implants are rarely needed in the maxillary arch to protract buccal segments in patients with a closed vertical dimension of occlusion (Fig. 25; Roberts et al., 1994). Figure 25 is a composite of the panoramic radiographs docu- menting the implant-anchored mesial translation of the maxillary and mandibular buccal segments. Once the impacted molar was recovered and optimal bilateral posterior occlusion was established, the root resorp- tion ceased (Fig. 26). Facial profile photographs show that as the vertical 88 Roberts and Roberts Figure 24. Case 4. Intraoral photographs at transfer reveal an expanded maxil- lary arch that has resulted in excessive buccal overjet. A transpalatal arch had been used, apparently in an attempt to control the excessive expansion. dimension of occlusion increased, the lips became less protrusive (Fig. 27). Superimposition tracings of the cephalometric radiographs (Fig. 28) reveal that as the buccal segments moved mesially, the vertical dimension of occlusion increased and the mandible moved downward and forward due to an increase in its effective length (Ar–Pg). These data suggest that the mandible was functionally retruded by parafunctional clenching sec- ondary to an uncomfortable occlusion. A TMJ growth response (Roberts, 2005) occurred once the habit was corrected, and bilateral posterior occlu- Sion was established (Fig. 28). BIOMECHANICS OF SPACE CLOSURE To avoid excessive extrusion of buccal segments during space closure, it is important to place a gable (inverted V bend) in the extrac- ºn site (Fig. 29). When the archwire is inserted in the brackets, it will deliver equal and opposite moments to the anterior and posterior seg- "ents (Roberts et al., 1994). Activation of the loop in the archwire by Cinching back distal to the second molars provides the force for space 89 Bone Physiology and Biomechanics Figure 25. Case 4. A panoramic radiograph series documents that the impacted maxillary third molar was recovered (yellow box) and the maxillary extraction sites were closed as indicated by the red arrows. Retromolar implants were used as indirect anchorage for mesial translation of the molars in the direction of the yellow arrows to close the mandibular extraction sites. After the spaces were closed, the TMA anchorage wires were cut off with a distal end-cutter (yellow circles). closure. These mechanics are indicated for TAD anchored space closure when opening the vertical dimension of occlusion is undesirable (Fig. 21B). Sliding wire space closure (Fig. 30) is indicated when the treat- ment plan is to increase the vertical dimension of occlusion. Since there is no inverted V-bend (gable) in the extraction site, the chain of elastics delivers a force along the archwire that displaces the roots of the teeth against the wall of the alveolus. Because the root and its alveolus are 90 Roberts and Roberts Figure 26. Case 4. The result seen in the maxillary occlusal ra- diograph taken at the end of active treatment is consistent with the following scenario; correction of the occlusal trauma to the maxillary incisors followed by a decrease in mobility, arrest of root resorption, and fill-in of new bone (yellow arrow) in the Space previously occupied by a widened PDL. tapered, teeth tend to extrude due to an inclined plane effect (Fig. 30; Rob- erts, 2005). These extrusive, space closure mechanics were used to open the bite for the patient seen in Case 4 (Figs. 22–28). MINISCREW INDICATIONS AND CONTRAINDICATIONS Miniscrews are appealing to orthodontists because the surgical Procedures to insert and remove them appear to be relatively simple. How- ºver, placing the TADs between the roots of teeth and outside the dental arches may be problematic. In addition. they have a relatively high failure **te, which is a major concern if there is no viable contingency plan. De- spite their limitations, miniscrews can be very effective anchorage for a Wide Variety of problems, but it is important that both the clinician and the Patient have realistic expectations and a viable alternative treatment plan In case the TAD fails. 91 Bone Physiology and Biomechanics Transfer 9 months Finish - -- º Figure 27. Case 4. Photographs taken at the same magnification document the decrease in lip protrusion that occurs as the lower facial height increases Secondary to correction of the clenching habit, as well as due to extrusive space closure mechanics. 92 Roberts and Roberts Figure 29. Non-extrusive space closure mechanics. A schematic diagram of indirect anchorage from a retromolar implant demon- Strates space closure mechanics for mesial translation of molars to close an edentulous space. A 019 x .025” TMA anchorage wire extends from the implant to a vertical slot in the bracket on the pre- molar. A gable bend (red and black dashed line) is placed in a .019 X.025” steel keyhole arch and the wire inserted into the archwire slot by applying moments to the wire in the direction of the green arrows, which generates equal and opposite moments on the teeth (green arrows). The space closure loop is activated by cinching back (black arrows). This mechanism generates equal and opposite forces and moments, which affects the molars but is negated by the anchorage wire for the implant. Furthermore, the anchorage wire Superior to the brackets prevents extrusion of the molars. *H = Figure 28. Case 4. Left: Cephalometric tracings superimposed On the anterior cranial base documents the downward and forward Positioning of the mandible secondary to extrusive space closure mechanics as well as correction of tongue bracing and clenching habits. Retreatment, progress (transfer) and finish are black, blue and red lines, respectively. Right: Maxillary superimposition shows that molars intruded and incisors flared during the clenching phase (black to blue). Subsequently, the molars extruded and the incisors Wºre retracted when the habit was controlled and the spaces were closed (blue to red). Mandibular superimposition demonstrates that the mandible increased in effective length (arrow) from pretreat- "ent to finish. The change in S-N line orientation documents for- Ward rotation of the mandible during clenching (black to blue), but *Overy to a more parallel descent after the habit was controlled (blue to red). 93 Bone Physiology and Biomechanics \ Figure 30. Extrusive space closure mechanics. Unless re- strained by a TAD or prosthetic implant, sliding wire me- chanics are extrusive, because activation with a spring or chain of elastics compresses the PDL in the direction of the force. The PDL is compressed maximally and the walls of the tapering alveolus serve as an inclined plane that ex- trudes the teeth (red arrow). Thus, space closure actually is a reciprocal guided eruption as shown by the black arrows on each tooth. Miniscrews are particularly effective for posterior maxillary an- chorage to intrude molars (Carano et al., 2004; Lee et al., 2004; Jeon el al., 2006). Posterior maxillary miniscrews can be used as direct anchorage to retract incisors and reduce the overjet of partially edentulous patients. but there are some important biomechanic considerations. The anterior portion of the NiTi spring can be attached to the archwire or the canine bracket if intrusion of the incisors is desired. Otherwise, a power-arm can be installed on the archwire so that the force of the spring has no intrusive component (Fig. 31). The current clinical interest in miniscrews has stimulated manu- facturers to produce a number of auxiliary devices used to simplify the 94 Roberts and Roberts - - Figure 31. Miniscrew mechanics. Bilateral miniscrews were installed in max- illary posterior alveolar bone to retract and intrude the maxillary anterior seg- ment. NiTi springs are attached to the miniscrews with steel ligatures (A). The medial aspect of the spring is tied to the archwire at the level of the canine bracket (B) or directly to a power-arm (yellow) attached to the archwire (C). Both approaches produce a retracting force (blue arrows), but only the attach- ment to the canine bracket produces an intrusive component (red arrow). Specialized mechanics employed to optimize TAD use. Slip-on connec- tors attached to NiTi springs (G&H Wire, Greenwood, IN) considerably simplify the connection of a spring to a miniscrew (Tomas R, Dentaurum, |Springen, Germany; Fig. 31). When a NiTi spring extends from the mo- lar to the lateral incisor or canine region, gingival tissue impingement is likely (Fig. 32). Preformed keyhole arches (G&H Wire, Greenwood, IN) are use- ful adjuncts for retraction of anterior segments with TADs. The Superior *Spect of the keyhole configuration also is a secure location for attaching the NiTi Spring to the archwire. The keyholes can be activated to provide Tetraction force, which is offset by the attachment of a Niſi spring be- Ween the TAD and the superior aspect of the keyhole. This mechanism eliminates the effect of friction, which can be a substantial problem when *tracting teeth on an archwire. The keyholes on the preformed archwires are also useful for controlling soft tissue contact when springs are ex- tended around the corner of the arch (Fig. 32). Alternatively, the hooks 95 Bone Physiology and Biomechanics and gingival extensions on brackets can be used to prevent the spring from contacting the mucosa (Fig. 33). Figure 32. A NiTi spring extending from a miniscrew in the posterior maxilla to the canine bracket (red ar- row) is likely to impinge on the gingiva. Figure 33. It is convenient to attach a device (upper left) to a miniscrew that will retain the TAD if it pulls out. The latter is important in preventing aspiration of the small miniscrew. To avoid soft tissue impingement, as shown in Figure 32, the NiTi Spring is restrained from the gingiva by spurs on the brackets. 96 Roberts and Roberts Miniscrews are not usually the TADs of choice for closing eden- tulous sites, particularly if the space is atrophic. Creating bone ahead of a moving tooth requires anabolic modeling along the periosteal surface of the atrophic defect. If the TAD is placed in or near an edentulous space that is to be closed, it may interfere with the anabolic modeling reaction to generate new bone and attached gingiva. Osseointegrated prosthetic implants often experience some loss of bone at the periosteal margin, and there is no evidence that bone increases in height adjacent to an implant (Aparicio and Orozco, 1998; Hultin et al., 2000). Furthermore, mini- screws do not integrate, so there is usually some degree of inflammation and localized infection at the periosteal margin (Fig. 8). Similar to peri- odontitis, this environment is known to inhibit osteogenesis (Roberts et al., 2004d, Roberts, 2005). When it is clinically desirable to close an edentulous space in the mandible, the TAD should be placed outside the zone where new bone for- mation is required. Since placing the miniscrew between the roots of teeth may be a biomechanical problem (Figure 21A), the most reliable solution for closing atrophic spaces continues to be a retromolar Osseointegrated implant (Figs. 14 and 25). MINISCREWS: REVOLUTION, EVOLUTION OR FAD? An osseointegrated device that is small, reliable, user friendly, easily removed, and low risk to the patient would be revolutionary. Rigid- ity relative to basal bone is an essential characteristic. At present, there are no miniscrews on the market that fit these criteria for a truly revolutionary device. The evolution of nonintegrated miniscrews has resulted in the de- velopment of a wide variety of useful designs that can be installed in small Osseous sites. Self-tapping and self-drilling fixtures have advantages and disadvantages, but no particular design is dominant. Although dozens of miniscrews are on the market and many more are seeking approval, none of them have achieved the reliability of osseointegrated fixtures. Short Osseointegrated devices that engage only the peripheral plate of cortical bone would have considerable appeal. However, this wor- thy goal may be difficult to achieve because healing and long-term main- tenance of Osseointegration is associated with loss of marginal bone at the periosteal surface (Quirynen et al., 1992; Aparicio and Orozco, 1998; Costa et al., 2006). 97 Bone Physiology and Biomechanics Some would argue that miniscrews are no more than a fad. Be- cause of the lack of rigorous regulation, almost anyone can make a mini- screw and market it. Despite limited capabilities of current systems, miniscrews have generated great interest in TADs among most orthodon- tists. It is my opinion that miniscrews are important evolutionary devices that will propel research and development of more reliable and versatile TADS. CONVENTIONAL MECHANICS Although the risk for typical miniscrew applications is minimal (Costa et al., 2006), they are invasive procedures that should be reserved for challenging problems that are not effectively managed with conven- tional mechanics. An appropriate use of miniscrew anchorage is treating skeletal open bite malocclusions that would otherwise require orthognathic surgery (Ko et al., 2006; Kravitz and Kusnoto, 2007b; Xun et al., 2007). On the other hand, an undesirable trend is substituting miniscrews for con- ventional anchorage when managing routine malocclusions. Overreliance on miniscrews may be necessary for a general dentist who is attempting to treat a challenging malocclusion, but not for a well-trained specialist. Conventional anchorage is not obsolete. There is more to quality orthodontics than miniscrews and NiTi wires. It is important to separate marketing hype from clinical reality. From the patient’s perspective, mini- screws are undesirable, invasive procedures. If they are necessary, the risk for the patient (Cheng et al., 2004; Kravitz and Kusnoto, 2007b; Kuroda et al., 2007) may be justified; otherwise, it is not. There are some alarming clinical reports of misuse and abuse of miniscrews, some of which were presented at the 2007 Moyers Symposium. An anchorage loss due to the failure of a miniscrew-dependent force system certainly will increase treatment time and may result in an avoidable compromise in outcome. If a critical miniscrew-dependant an- chorage system has an 80% success rate (Cheng et al., 2004; Kuroda et al., 2007), the 20% that fails may precipitate major clinical problems. This is an unacceptable rate of failure for elective orthodontics procedures. Fur- thermore, even “successful” miniscrews move relative to their osseous support (Liou et al., 2004), so there may be some anchorage compromise for most patients. Numerous proponents of miniscrews confess that they had a relatively high failure rate when they began using the devices (“learning curve”). However, carefully selecting patients and miniscrew sites, the 98 Roberts and Roberts success rate increases to about 90%. This begs the question of what is “success?” Determining a scientifically reliable “success rate” for mini- screw anchorage systems requires well-defined prospective research car- ried out by independent investigators. The trials should be restricted to challenging anchorage problems in which TADs are required to achieve an optimal result. Evaluation of “success” should be determined by blinded, independent investigators using rigorous prospective criteria. ORTHODONTIC EDUCATION Orthodontic educators have seen many fads and trends come and go. The appropriate role for miniscrews in routine clinical practice is yet to be defined. Educators must guard against an erosion of interest by stu- dents in learning the principles of biomechanics and anchorage control in favor of managing all anchorage problems with miniscrews. If the en- trepreneurs who offer orthodontics for general dentists jump on the band wagon, miniscrews may provide an unexpected benefit for orthodontists. It may evolve that a specialist’s ability to manage malocclusions without miniscrews will be an important marketing advantage. Few patients or parents would prefer the expense and risk of miniscrews if routine me- chanics is a viable option. The faculty of graduate orthodontic programs should offer expo- Sure to miniscrews, but the major emphasis should continue to be on con- ventional mechanics and quality outcomes. Students should be challenged to solve anchorage problems with conventional mechanics and only use miniscrews when there is no viable alternative. DEVELOPMENT OF NEW ANCHORAGE DEVICES At present, the field of miniscrew TADs is evolving largely on the basis of clinical trial and error. Historically, the current surge in mini- screws is akin to the initial development of endosseous blade and root- form dental implants prior to about 1980. At present, the only reliable means for discriminating between current miniscrew systems is via a thor- ough knowledge of the fundamental principles of bone biology, osseo- integration and biocompatibility (Roberts and Roberts, 2007). The déjà vu of this statement is haunting because this was the same rationale for selecting prosthetic implants at the start of the osseointegration era in the 1980s (Roberts et al., 1987; Roberts, 1988). Development of more reli- able and versatile TADs probably will evolve similarly to that of dental implants. The concept of osseointegration was revolutionary for dental 99 Bone Physiology and Biomechanics implants and probably is the essential element needed to elevate mini- screws to the level of truly reliable anchorage devices. . The marketing exuberance in recent years for nonintegrated mini- screws has been impressive, particularly since there is little reliable inde- pendent research supporting the efficacy of use for any of the miniscrew systems currently available. Clinical applications have exceeded the scien- tific rationale for their effective use considerably. Hopefully, manufactur- ers with substantial R&D capabilities will recognize the market potential for improved, second generation devices. The latter probably will exploit the proven biotechnology of rigid Osseous fixation (osseointegration). Most of the titanium miniscrews currently available could be adapted to osseointegrate. However, animal trials of such devices have shown that the removal torque is dangerously close to the yield strength of the screws (Morais et al., 2007). Addressing this problem will be an important factor in designing second generation miniscrews that can serve as rigid anchorage devices, yet be removed easily at the end of active treatment. It is important for second generation devices to be relatively simple to place and remove. Furthermore, they must achieve a high rate of suc- cess for all orthodontic and orthopedic applications, across the full scope of dentofacial therapy. Practical, rigidly integrated devices for indirect anchorage in the retromolar and palatal regions would be helpful. Placing TADs outside the dental arch avoids interradicular surgical problems and does not interfere with the path of tooth movement. CONCLUSIONS • Osseointegrated TADs are the gold standard for anchorage reli- ability but are relatively complex and expensive to use. • Nonintegrated miniscrews are much less reliable, particularly for challenging problems. • Small osseointegrated TADs are needed for convenient place- ment and removal in the palate and retromolar regions. • Indirect anchorage with retromolar implants is preferable to placing miniscrews between the roots of teeth when treating partially edentulous patients with decreased vertical dimension of occlusion. • Direct anchorage with miniscrews is indicated for posterior maxillary anchorage to intrude molars for correction of open 100 Roberts and Roberts bite and for retracting anteriorsegments in noncompliant patients. • From the patient’s perspective, TADs are undesirable and re- quire invasive procedures that should be reserved for problems for which there is no reasonable alternative. 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J Esthet Dent 1998a;10:315-324. Wehrbein H, Merz BR, Diedrich P, Glatzmaier J. The use of palatal im- plants for orthodontic anchorage. Design and clinical application of the orthosystem. Clin Oral Implants Res 1996;7:410-416. Wehrbein H, Merz BR, Hämmerle CH, Lang NP. Bone-to-implant contact of orthodontic implants in humans subjected to horizontal loading. Clin Oral Implants Res 1998b;9:348-353. Wehrbein H, Riess H, Meyer R, Schneider B, Diedrich P. Bodily movement of teeth in atrophic jaw segments. Dtsch Zahnarztl Z 1990;45:168- 171. Wittwer G, Adeyemo WL, Schicho K, Gigovic N, Turhani D, Enislidis G. Computer-guided flapless transmucosal implant placement in the 109 Bone Physiology and Biomechanics mandible: A new combination of two innovative techniques. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006; 101:718–723. Xun C, Zeng X, Wang X. Microscrew anchorage in skeletal anterior open- bite treatment. Angle Orthod 2007;77:47-56. Yano S. Tapered orthodontic miniscrews induce bone-screw cohesion fol- lowing immediate loading. Eur J Orthod 2006:28:541-546. Yip G, Schneider P, Roberts WE. Micro-computed tomography: High resolution imaging of bone and implants in three dimensions. Semin Orthod 2004; 10:174–187. 110 THE TREATMENT OF OPEN BITE WITH MICROIMPLANT ANCHORAGE Hyo-Sang Park Hee-Moon Kyung Jae-Hyun Sung Treatment of open-bite malocclusion has been one of the most difficult treatments in conventional orthodontic mechanics. There have been sev- eral attempts to treat open bite after intrusion of the posterior teeth with the posterior bite block, the magnetic bite block and/or the vertical chin cap (Kuster and Ingervall, 1992; Dellinger and Dellinger, 1996; Iscan et al., 2002). All of these appliances require a great deal of patient compliance to be successful. However, skeletal anchorage devices such as dental im- plants, miniplates and mini- or microscrew implants, which use bone for anchorage, have provided the clinician with a new, easy and efficient way to intrude teeth with little patient compliance required and few side effects (Creekmore, 1983; Shapiro and Kokich, 1988; Kanomi, 1997; Park, 1999; Umemori et al., 1999; Park et al., 2001; Sherwood et al., 2002). Dental implants require extensive surgery, are expensive and have anatomical limitations, all of which have kept them from being used rou- tinely in orthodontic practice. The tiny microscrew implants, however, can be placed into interradicular space and be positioned along the line of force needed to achieve a specific treatment objective. Easy placement and removal, low cost, and little need for patient compliance have made the microimplant an indispensable tool for the orthodontic clinician (Park et al., 2001). Skeletal anchorage can be very effective at maintaining anchor- age during retraction and intrusion of teeth (Park, 2003; Park et al., 2003). Surgical mini-plates were used to intrude the posterior teeth and to treat open bites (Umemori et al., 1999; Sherwood et al., 2002). Microscrew implants have shown their efficacy in treating open bite after intrusion of the posterior teeth in both extraction and nonextraction treatments (Park et al., 2004, 2006). In nonextraction treatment, simple intrusion of the posterior teeth brings about closure of the anterior open bite by autorotation of the mandible (Umemori et al., 1999; Sherwood, 2002; Park et al., 2006). 111 Treatment of Open Bite However, in high mandibular plane angle patients, simple intrusion may not produce sufficient autorotation to obtain profile improvement. The ex- traction of teeth may be helpful in closing the mandibular plane angle (Garlington and Logan, 1990; Aras, 2002). However, the mesial tipping of posterior teeth caused during closure of extraction spaces opens the mandibular plane angle by extruding the distal cusp tips, especially in high angle cases (Kim, 1987). Therefore, it is important to maintain a verti- cal position of the upper and lower posterior teeth and to prevent them from tipping mesially. The role of microimplants in extraction treatment for anterior open bite is to provide anchorage not only for anterior teeth retraction, but also for intrusion or vertical control of the posterior teeth. The retraction of the anterior teeth and autorotation of the mandible after intrusion and uprighting of the posterior teeth contribute to positive facial profile changes. * In this chapter, we would like to discuss microimplant mechanics for treatment of anterior open bite using two case studies to illustrate our points. DIAGNOSIS The anterior open-bite patient has the skeletal characteristics of a high mandibular plane angle, a forward-tipped palatal plane, and a large interlabial gap. Intrusion of posterior teeth can produce autorotation of the mandible. Nonextraction treatment of open bite includes only intrusion of the molars to close the anterior open bite and some distal movement of the anterior teeth. The autorotation of the mandible after intrusion of the pos- terior teeth produces a positive profile improvement in high mandibular plane angle open-bite cases in which the chin is located distal to the norm. Therefore, the amount of profile change that occurs after intrusion of the molars should be checked. A 1 mm intrusion of the molars may produce a 2 to 3 mm of anterosuperior rotational movement of the chin. The decrease in vertical dimension affects the profile tremendously by eliminating hy- peractive mentalis muscle activity. There also is an increase in the SNB angle, which may have positive effects on treating Class II malocclusions. Detailed diagnostic steps have been discussed in a previous report (Park et al., 2006). The extraction of teeth in the middle of the arch provides space for anterior teeth retraction and mesial movement of the posterior teeth. Mesial movement of the posterior teeth may close the mandibular plane angle by moving the fulcrum, i.e., posterior teeth, forward. The posterior teeth should be brought forward without tipping, because the mesial tip- 112 Park et al. ping movement may cause the distal cusps of the posterior teeth to pro- trude occlusally and resultantly brings about bite opening anteriorly. Ex- traction treatment of open bite cases uses these two movements, i.e., intru- sion of molars and mesial movement of molars. They effectively can close the mandibular plane angle. The decision to extract teeth when treating an open bite can be made based on the amount of arch length discrepancy and the patient’s pretreatment profile, vertical dimension, and interlabial gap. If a patient has a severe arch length discrepancy and/or retropositioned chin, long low facial height and a large interlabial gap, the extraction of teeth should be considered. Intrusion of molars alone may not produce enough autorota- tion of the mandible to improve the profile of patients who have a high mandibular plane angle. PLACEMENT OF MICROIMPLANTS Location of the Microimplants In extraction open-bite treatment, the microimplants should be placed in the buccal alveolar bone between the maxillary second premolar and first molar. The microimplants must provide anchorage for intrusion of the posterior teeth as well as for retraction of the anterior teeth. As il- lustrated in a previous report, the available implant space is widest in the radicular area between the maxillary second premolars and first molars (Park, 2002). For nonextraction open-bite treatment, the palatal interra- dicular bone between the maxillary first and second molars can be used. Mandibular microimplants can be placed in buccal alveolar bone between the first and second molars in both extraction and nonextraction treatment. Mandibular microimplants can be used to intrude the mandibu- lar molars and to upright mesially tipped mandibular molars. TREATMENT MECHANICS Extraction Treatment The treatment mechanics for open-bite correction combined with extraction of premolars is similar to that of microimplant anchorage (MIA) sliding mechanics, except for the addition of intrusion force applied to the maxillary posterior teeth from the microimplants placed in the maxilla (Fig. 1; Park, 2001; Park et al., 2001, 2005; Park and Kwon, 2004). 113 Treatment of Open Bite Figure 1. Microimplant treatment mechanics combined with extraction of the premolars for open-bite correction. The occlusogingival position of the microimplants should be clos- er to the gingival margin than in MIA sliding mechanics. The low position of the microimplants causes lingual tipping of the maxillary incisors dur- ing retraction, and lingual tipping of the incisors tends to close the open bite. In MIA sliding mechanics when combined with premolar extractions. the microimplants should be placed 8 to 10 mm from the archwire in the maxilla; however, microimplants must be placed 4 to 6 mm from the max- illary archwire to facilitate closure of the anterior open bite. To prevent buccal tipping of the posterior teeth by buccal intrusion forces in the max- illa, a transpalatal bar should be used. Nonextraction Treatment The intrusion force applied to the posterior teeth produces intru- sion of the molars, which leads to autorotation of the mandible and clo- sure of the anterior open bite (Fig. 2). The intrusion force distal to the center of resistance of the dentitions can produce a clockwise rotation in the maxillary dentition and a counter-clockwise rotation in the mandibu- lar dentition, which produces closure of the open bite anteriorly. The in- trusion of posterior teeth in one arch may lead to extrusion of posterior teeth in the opposite arch, and may not produce bite closing anteriorly. || 4 Park et al. Therefore, the intrusion force should be applied to both arches. Applying an intrusion force only to one side, buccal or lingual, produces adverse buc- cal or lingual tipping of the teeth. To prevent this, a transpalatal bar (Fig. 3) and lingual arch (Fig. 4) should be placed in the posterior teeth segment. We prefer to connect both first and second molars to the transpalatal bar or lingual arch when intruding the posterior segments. 4. Figure 2. Microimplant treatment mechanics for nonextraction Open-bite correction. Figure 3. Transpalatal bar connecting the first and second molars to prevent lingual tipping of the posterior teeth during intrusion. 115 Treatment of Open Bite Figure 4. A lingual arch connecting the first and second molars to prevent buccal tipping of posterior teeth during intrusion. Refeation The most difficult task in open-bite treatment is retention. Accord- ing to previous studies, 30% to 40% of patients who underwent orthodon- tic or orthognathic surgical treatment for open bite relapsed or showed an increase in facial height (Lopez-Gavito et al., 1985; Denison et al., 1989). In fact, there are many factors that affect the stability of open-bite treatment. The length of the masticatory muscle is determined during growth and cannot be changed with treatment after completion of growth. Therefore, functional exercises, which strengthen the muscle force, may be helpful (English, 2002), as might be clear invisible retainers made from plastic sheets that provide uniform thickness from the posterior teeth to the anterior teeth and exert differentially heavier force during chewing to the posterior teeth (Fig. 5). This type of retainer provides good stability during retention. Another method for maintaining anterior over-bite correction is to keep the microimplants in the bone and use them as anchorage for elastics for a period of time (Fig. 6). In Case 1 presented in this chapter, we left the lower microimplants in the bone and asked the patient to wear elastics during the night that were anchored from the microimplants and attached to hooks on the clear retainer in the canine area. The direction of force was downward and backward, which was helpful in obtaining intrusion and a slight distal movement of the mandibular dentition. 116 Park et al. Figure 5. A clear plastic retainer provides intrusion force to the posterior teeth. Figure 6. Mandibular microimplants still in place after treatment can be used as anchorage for elastics to retract and intrude teeth. CASE PRESENTATIONS Case I A 31-year-old male patient presented with a relapsed anterior Open bite after two bouts of open-bite treatment with conventional mecha- notherapy (Fig. 7). He had strain on circumoral muscle during lip closure, and his tongue protruded during swallowing. Cephalometric analysis showed an ANB angle of 4° and a man- dibular plane angle of 28° (Table 1). The anterior overbite and overjet *** -2 mm and 0.5 mm, respectively. He was diagnosed with a skeletal Class II open-bite malocclusion. Dentally, the mandibular anterior teeth showed labioversion and arch length discrepancies in the maxilla and the ||7 Treatment of Open Bite Figure 7. Pretreatment facial and intraoral photographs and radiographs for Case 1 patient. Table 1. Cephalometric measurements for Case 1 patient. Pretreatment Post-treatment SNA (*) 76 76 SNB (*) 72 73.5 ANB (*) 4 2.5 FMA (*) 28 26.5 PFH/AFH 53.5/89 (0.6) 54.5/87 (0.63) FH to Occ P(*) 12.5 12.5 U1 to FH (*) 109.5 106 IMPA (*) 105 96.5 Z Angle (*) 60° 63.5 Upper lip to E Line -1 –0 Lower lip to E Line 4 2 mandible were 0 mm and -1 mm, respectively. He had severe attrition of both maxillary and mandibular posterior teeth as well as severe root resorption of both maxillary and mandibular incisors. Due to previous treatment, posterior teeth in both arches showed uprighting to the occlu- 118 Park et al. sal plane, and there was mesial inclination of teeth from premolars to an- terior teeth. Treatment Planning. Because the patient had an acceptable profile and minimal arch length discrepancies, nonextraction treatment was cho- Sen. To intrude the posterior teeth, the microimplants were placed in the posterior area. The distal retraction of the mandibular anterior teeth and re-approximation of the mandibular incisors were carried out to increase Overjet and overbite. Because the anterior teeth exhibited root resorption, they were not included in the mechanotherapy during the initial treatment period. Alignment of incisors was to be completed in the finishing stage of treatment. To retain treatment results, the mandibular microimplants were left in place after active treatment was finished to be used as anchorage for elastics. Treatment Progress. MBT brackets (.022.”) were bonded from the canines to the second molars. Two months into treatment, two microim- plants (SH 1312-07, Dentos Ltd., Daegu, Korea) were placed in the alveo- lar bone between the maxillary second premolars and first molars, and two microimplants (SH1312-06, Dentos Ltd.) were placed between the mandibular first and second molars in the widest available interradicular Space (Park, 2002; Fig. 8). The details of the implant surgical procedure have been presented in previous reports (Park, 2001; Park et al., 2004; Sung et al., 2006). A month after microimplant placement, the mandibular microimplants became mobile; two new microimplants were placed more apically than the previous ones. Because the patient was a heavy smoker, he experienced several microimplant failures during the course of treat- ment. A transpalatal bar soldered to the maxillary first and second molars On both sides was installed, the purpose of which was to prevent buccal tipping during intrusive force application from the buccal microimplants (Fig. 9). The mandibular arch received a lingual arch connecting the first and second molars of both sides also to prevent buccal tipping during in- trusion. Figure 8. Intrusion force applied from the buccal microimplants. Note that the *Sors were not included in the mechanotherapy. |19 Treatment of Open Bite Figure 9. A transpalatal bar and lingual arch were installed to prevent buccal or lingual tipping of the teeth, as the anterior teeth had begun to contact each other After placing the mandibular microimplants into the deep vesti- bule between the first and second molars, we applied elastomeric intrusive force from hooks made of ligature wire to the mandibular archwire. In the maxillary arch, the microimplants that were placed buccally between the second premolars and first molars did not produce an appropriate line of force to the center of the whole maxillary arch. Because of the difference in the amount of time intrusion took to occur between the posterior and an- terior teeth, there was not much improvement in anterior vertical overlap. even with intrusion of the posterior teeth. After failure of the maxillary mi- croimplants on the right side, we placed two microimplants into the palatal alveolar bone between the first and second molars (Fig. 9). The intrusion force applied from the palatal microimplants to the maxillary posterior teeth produced comparatively rapid intrusion and bite closing anteriorly. The anterior teeth in the upper and lower arches may have contacted pre- maturely following the creation of an open bite posteriorly, leading to trau- matic occlusion anteriorly. This may cause trauma from occlusion at the anterior teeth area. To prevent this, clinicians need to apply a distal force in the mandible and/or perform reapproximation of the mandibular anterior teeth (Fig. 10). These procedures also help increase overbite and overjet. The weak musculature of patients sometimes may not provide settling of the occlusion, in which case vertical elastics are required to obtain better interdigitation. After 13 months of treatment, brackets were bonded to the anterior teeth for alignment (Fig. 11). Total active treatment time was 19 months, after which lingual retainers were bonded 3–3 in the maxilla and 4–4 in the mandible (Fig. 12). A wrap-around retainer also was placed in the maxilla, and a clear 120 Park et al. invisible retainer, made from a sheet of plastic, was placed in the man- dible. The patient was asked to wear elastics at night that were attached from the mandibular microimplants to hooks in the canine area on the clear retainer sheet (Fig. 14). Treatment Results. There was a remarkable decrease in anterior facial height and the FMA angle. In addition, after intrusion of the poste- rior teeth, the mandible autorotated and the ANB angle decreased from 4° to 2.5° following an increase in the SNB angle by 1.5° (Table 1). Intraorally we obtained Class I canine and molar relationships with a slight open bite of the posterior teeth (Fig. 12). While the anterior teeth exhibited root resorption initially, it did not seem to be aggravated by treatment based on the panoramic radiograph taken at the end of active treatment. Superimposition of cephalometric tracings showed intrusion of the maxillary and mandibular posterior teeth and the resultant autorotation of the mandible (Fig. 13). In addition, a positive overjet and overbite were obtained by these movements, with lingual tipping of the both the maxil- lary and mandibular incisors. Seven-month retention photographs showed a well maintained dentition with only a slight open bite of the posterior teeth (Fig. 14). Figure 10. Distal and intrusive force was applied to the mandibular dentition to increase the overjet and overbite. - Figure 11. After 13 months of treatment, brackets were bonded to the anterior teeth to align them. 121 Treatment of Open Bite Case 1 patient. - Pre-treatment - Post-treatment º (ſ Figure 13. Superimpositions of pretreatment and post- treatment cephalometric tracings. 122 Park et al. - - CIn Figure 14. Intraoral photographs with and without retainers taken after sev months of retention. Case 2 Microimplant mechanics used to treat open-bite malocclusions - - - - - The When the extraction of premolars is necessary is discussed in Case 2 123 Treatment of Open Bite extraction of premolars helps reduce the vertical dimension, and in severe open bite or open bite with moderate to severe arch length discrepancies, extraction of premolars should be considered even though vertical control and molar intrusion can be achieved with microimplants alone. A 23-year-old female patient presented with an anterior open bite, temporomandibular disorder and eroded condylar heads (Fig. 15). She also had protruded lips and a retropositioned chin, with an SNB angle of 75.5° and an ANB angle of 6° (Table 2). Vertically she had a high man- dibular plane angle (FMA angle of 35°). Intraorally this patient had -4 mm of overbite and 4 mm of overjet. The arch length discrepancies in the maxilla and mandible were 0 and -2 mm respectively, and the curve of Spee was 4.5 mm. The only teeth that were in occlusal contact with their opposing teeth were the second molars. All of the posterior teeth tipped mesially to the bisected occlusal plane. Treatment Plan. Because the patient complained of lip protru- Sion, the first premolars were extracted. To provide anchorage for retrac- º -- Figure 15. Pretreatment facial and intraoral photographs and radiographs of Case 2 patient. 124 Park et al. Table 2. Cephalometric measurements for Case 2 patient. Pretreatment Post-treatment SNA (°) 81.5 80 SNB (°) 75.5 75.5 ANB (°) 6 4.5 FMA (°) 35 34 PFH/AFH 39.5/70 (0.56) 40/68.5 (0.58) FH to Occ P (*) 15 11 U1 to FH (°) 113 104 IMPA (°) 90 . 80 ZAngle (°) 68 74 Upper lip to E Line 0.5 -1.5 Lower lip to E Line 1.5 -1.5 tion of the maxillary anterior teeth, microimplants were placed between the second premolars and first molars in the largest interradicular space available in the maxilla (Park, 2002). The mesial movement of the uprighted posterior teeth can close the mandibular plane by moving a fulcrum forward. To facilitate mesial movement of the posterior teeth, the mandibular second premolars also were extracted. To prevent the posterior teeth from tipping forward during space closure, power arms, which move the line of force from the bracket level to the level of center of resistance of the posterior teeth, were used. The lower microimplants were placed between the lower first and second molars. The purpose of these microimplants was to apply intrusion force to the mandibular second molars and counterclockwise moment to the first molars. Mesially tipped posterior teeth should be uprighted to the occlusal plane to ensure stable results. Intrusion and uprighting of the mandibular molars produced autorotation of the mandible with the resultant profile improvement. Treatment Progress. After extraction of the maxillary first and mandibular second premolars, 022-slot straight wire brackets were placed. A transpalatal bar was installed to prevent distortion of the arch form and to prevent the posterior teeth from tipping buccally from the applied intru- sion force on buccal side. Microimplants (AbsoAnchor”, SH1312-08, Dentos Ltd., Daegu, Korea) were placed between the maxillary second premolars and first mo- lars on both sides using the self-drilling method (Fig. 16). Immediately after microimplant placement, NiTi coil springs were connected with a 125 Treatment of Open Bite light force of less than 70 g from microimplants to canines. A month later, a .017 x .025” archwire with hooks was inserted, and a retraction force of 150 g was applied on each side. To maintain the inclination of the maxil- lary anterior teeth during retraction, 3° of bend was applied between the lateral incisors and canines and just distal to canines to increase the coun- terclockwise moment. The intrusion force also was applied from the microimplants to the posterior teeth by an elstomeric thread in the maxilla. The second mo- lars were connected to the first molars by a main archwire on the buccal side and by a sectional archwire on palatal side. This prevented differential torque from occurring between the first and second molars (Fig. 17). The mandibular microimplants (Abso Anchor") were placed be- tween the first and second molars using the self-tapping method and 100 g of force was applied immediately to the microimplants by connecting an elastomeric thread from the archwire to the microimplant (Fig. 18). At four months of treatment, a .016 x 022.” TMA wire was inserted and a 100 g of intrusion force was applied to intrude and upright the mandibu- lar molars. To minimize forward tipping of the mandibular molars during space closure, the power arm was extended gingivally on the mandibular first molars (Fig. 19). This oriented the force near to the center of resis- tance of the mandibular first molars and minimized the clockwise mo- ment on the first molars during space closure. The intrusion force distal to the first molars produced a counterclockwise moment on the first mo- lars, which also was a factor in preventing mesial tipping of the first mo- - - tº | - |s º * * * - Figure 16. The maxillary microimplants initially were used for anterior teeth retraction. 126 Park et al. Figure 17. Retraction archwires attached to the microimplants were used to º tract the maxillary anterior teeth. The transpalatal bar and a sectional archwire Were used for second molar control. to the posterior teeth. lars. The buccal intrusion force in the mandible can produce buccal tip- Ping. This should be prevented by applying lingual crown torque to the archwire and by reducing the level of force to 50 g. The application of light force over a long period can produce intrusion or uprighting of the molars. 127 Treatment of Open Bite Figure 19. Intrusion force supplied by the maxillary microimplants and power arms at the mandibular first molars directed force to the center of resistance. Figure 20. At the final stage of treatment, vertical elastics were used for occlusal settling. The microimplant on the mandibular left side showed slight mo- bility at 17 months of treatment and failed four months later. The other mi- croimplants remained firm throughout treatment and were easily removed at the end of treatment by turning them in counterclockwise direction. At 21 months of treatment, vertical elastics were used to facilitate occlusal settling (Fig. 20). Total active treatment time was 26 months. A lingual bonded retainer was bonded to both maxillary and mandibular anterior teeth. Wrap-around retainers also were delivered. Treatment Results. There was improvement in the patient’s fa- cial profile after retraction of the anterior teeth (Fig. 21). Anterior facial height decreased and the FMA angle decreased by 1°. There was a reduc- 128 Park et al. tion in Point A after bodily retraction of the maxillary anterior teeth. Con- sequently, there was a decrease in the ANB angle from 6° to 4.5°. Intraorally, Class I canine and molar relationships were obtained with good interdigitation. There was no obvious root resorption apparent on the panoramic radiograph. Cephalometric superimpositions revealed that in the maxilla, the posterior teeth had been intruded and the anterior teeth had been distally retracted bodily (Fig. 22). In the mandible, the posterior and anterior teeth had been uprighted. The patient was not experiencing TMJ discomfort at the end of treatment, and the erosion of the condylar heads did not seem to have been aggravated. | * , Figure 21. Post-treatment facial and intraoral photographs and radiographs of Case 2 patient. DISCUSSION Microimplants can produce intrusive force to the teeth, because they are placed in the alveolar bone, which is apical relative to bracket 129 Treatment of Open Bite - Pre-treatment - Post-treatment W Figure 22. Superimposition of pretreatment and post-treatment cephalometric tracings for Case 2 patient. slots. Therefore, it is much easier to apply intrusive force than extrusive force with microimplants. The intrusive force applied to posterior teeth can lead to auto- rotation of the mandible and bite closure. Sometimes there is premature contact of the maxillary and mandibular anterior teeth in the course of the molar intrusion. To prevent premature contact, the mandibular anterior teeth should be distalized and/or tooth size reduced. Distal tipping of the anterior teeth increases the anterior overbite. In extraction treatment, the posterior teeth do not need to move distally; however, in nonextraction treatment the teeth need to be distalize to resolve anterior crowding or to increase overjet and overbite in the man- dible. When planning distal movement of the posterior teeth, third molars, if present, should be removed to enhance distal movement of molars. The newly created socket facilitates distal tooth movement. Microimplants should not touch tooth roots; contact at the time of placement or during the course of intrusion stops tooth movement, includ- ing distal retraction and intrusion. Therefore, the maxillary microimplants used to intrude molars should be placed high above the roots of teeth. If there is retarded intrusion of the posterior teeth, the clinician must make sure that there is no chance of root contact. If there is contact, the clinician should consider placing a new microimplant in a higher position. 130 Park et al. Microimplants can be loaded immediately after placement, but the force needs to be small. We apply less than 70 g of force immediately after placement and increase the level of force two or three months after placement. The force level needed to intrude a molar suggested by previous reports ranges from 90 to 500 g (Kalra et al., 1989; Melsen and Fiorelli, 1996; Umemori et al., 1999; Sung et al., 2006). The greater the increase in the level of force, the greater would be the expected root resorption (Del- linger, 1967). It seemed reasonable to apply 200 g of force on each side to intrude the posterior segment in the nonextraction treatment case, which was equivalent to 100 g of force for each molar. However, the force ap- plied to the mandibular posterior teeth in the extraction treatment case was only 50 g. The heavier force might have caused buccoversion of the poste- rior teeth. To prevent this, we applied very light force and applied lingual crown torque on the lower archwire. Although the level of force was light, when applied for a long period of time, there is intrusion of the posterior teeth. The small amount of intrusion of the posterior teeth can cause a big change in the anterior vertical dimension. Therefore, there is no need to apply heavy force on the mandibular posterior teeth. The transpalatal bar and lingual arch should provide sufficient ri- gidity to resist the force that can induce buccal or lingual tipping of the teeth. Therefore, we used stainless steel wire to make the transpalatal bar and lingual arch. The transpalatal bar should have free way from palatal mucosa to evade impingement. By using microimplants as anchorage for retraction of anterior teeth in extraction open-bite treatment, there is no mesial force being ap- plied to the maxillary posterior teeth that could cause mesial tipping of the posterior teeth. Mesial tipping of the posterior teeth may produce the force that intrudes the anterior teeth. To ease the open-bite treatment, clinicians need not apply mesial force to the posterior teeth at the bracket level, but rather to the center of resistance of the posterior teeth. The force passing apical to the center of resistance of the posterior teeth can upright the pos- terior teeth and cause spontaneous closure of the anterior open bite. The high mandibular angle patients have weak musculature, so the occlusion cannot be settled down occasionally even after having loss of contact of the posterior teeth after intrusion. Although premature con- tact happens, the mandible may not show deviation to evade premature contact and to increase teeth contact surface. Therefore, to facilitate set- tling of occlusion, vertical elastics can be used to guide the mandible. 131 Treatment of Open Bite With regard to retention of open-bite treatment results, both surgi- cal and orthodontic treatments incur some amount of relapse (Lopez-Gav- ito et al., 1985; Denison et al., 1989). The extruded teeth are less stable than intruded teeth according to Reitan and Rygh (Reitan and Rygh, 1994). Therefore, the treatment of open bite after intrusion of the posterior teeth may have an inherent advantage of better stability and facial profile im- provement following counterclockwise autorotation of the mandible. To improve stability after treatment, Sugawara and colleagues suggest overcorrection (Sugawara et al., 2002). Simple over-intrusion of the posterior teeth does not increase overjet and overbite. However, distal retraction and/or reapproximation of the mandibular anterior teeth do facilitate increasing overjet and overbite. Therefore, it seems better to prolong treatment and use additional retention devices if this improves long-term stability of treatment results. The lingual bonded retainer, which connects premolar to premolar, also can be helpful, as can the clear type retainer, which provides more intrusion force to posterior teeth during chewing due to the same thickness of sheet on the occlusal surface from anterior to posterior teeth, and it makes early contact of posterior teeth. The active way to apply intrusive force during retention is to maintain the microimplant in the mouth after completion of treatment and to apply an intrusive force during the night from the microimplant to a lingual button attached to the clear retainer at the first premolar. However, microimplants that have remained in bone for a long period of time have osseointegrated tightly with the bone, and clinicians must make sure not to fracture the microimplant when finally removing it. REFERENCES Aras A. Vertical changes following orthodontic extraction treatment in skeletal open bite subjects. Eur J Orthod 2002:24:407-416. Creekmore TD. The possibility of skeletal anchorage. J Clin Orthod 1983;17:266-269. Dellinger EL. A histologic and cephalometric investigation of premolar intrusion in the Macaca speciosa monkey. Am J Orthod 1967:53:325- 355. Dellinger EL, Dellinger EL. Active vertical corrector treatment – Long- term follow-up of anterior open bite treated by the intrusion of poste- rior teeth. Am J Orthod Dentofacial Orthop 1996;110:145-154. 132 Park et al. Denison T, Kokich V, Shapiro P. Stability of maxillary surgery in openbite versus non-openbite malocclusion. Angle Orthod 1989:59:5-10. English JD. Early treatment of skeletal open bite malocclusion. Am J Or- thod Dentofacial Orthop. 2002; 121:563-565. Garlington M, Logan LR. Vertical changes in high mandibular plane cases following enucleation of second premolars. Angle Orthod 1990;60:263-268. Iscan HN, Dincer M, Gültan A, Meral O, Taner-Sarisoy L. Effects of verti- cal chincap therapy on the mandibular morphology in open-bite pa- tients. Am J Orthod Dentofacial Orthop 2002;122:506-511. Kalra V, Burston CJ, Nanda R. Effects of a fixed magnetic appliance in the dentofacial complex. Am J Orthod Dentofacial Orthop 1989;95:467– 478. Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod 1997:31:763-767. Kim YH. Anterior openbite and its treatment with multiloop edgewise archwire. Angle Orthod 1987:57:290–321. Kuster R, Ingervall B. The effects of treatment of skeletal open bite with two types of bite-blocks. Eur J Orthod 1992; 14:489–499. Lopez-Gavito G, Wallen T, Little R, Joondeph D. Anterior open-bite maloc- clusion: A longitudinal 10-year postretention evaluation of orthodonti- cally treated patients. Am J Orthod 1985;87:175-186. Melsen B, Fiorelli G. Upper molar intrusion. J Clin Orthod 1996:30:91- 96. Park HS. The skeletal cortical anchorage using titanium microscrew im- plants. Kor J Orthod 1999:29:699-706. - Park HS. The Use of Micro-Implant as Orthodontic Anchorage. Seoul, Nare Pub Co., 2001. Park HS. An anatomical study using CT images for the implantation of micro-implants. Kor J Orthod 2002:32:435-441. Park HS. Intrusion molar con anclaje de microimplantes (MIA, Micro-im- plants Anchorage). Orthodoncia Clinica 2003;6:31-36. Park HS, Bae SM, Kyung HM, Sung JH. Micro-implant anchorage for treatment of skeletal Class I bialveolar protrusion. J Clin Orthod 2001:35:417-422. Park HS, Bae SM, Kyung HM, Sung JH. Simultaneous incisor retraction and distal molar movement with microimplant anchorage. WJ Orthod 2004;5:164-171. Park HS, Kwon OW, Sung JH. Microscrew implant anchorage sliding me- chanics. W J Orthod 2005;6:265-274. 133 Treatment of Open Bite Park HS, Kwon OW, Sung JH. Nonextraction treatment of an anterior openbite with microscrew implant anchorage. Am J Orthod Dentofa- cial Orthop 2006; 130:391-402. Park HS, Kwon TG. Sliding mechanics with microscrew implant anchor- age. Angle Orthod 2004;74:703–710. Park HS, Kwon TG, Kwon OW. The treatment of openbite with microscrew implants anchorage. Am J Orthod Dentofacial Orthop 2004; 126:627- 636. Park YC, Lee SY, Kim DH, Lee SH. Intrusion of posterior teeth using miniscrew implants. Am J Orthod Dentofacial Orthop 2003; 123:690- 694. Reitan K, Rygh P. Biomechanical principles and reactions. In: Graber TM, Vanarsdall RL, eds. Orthodontics-Current Principles and Techniques. 2" ed., St Louis, Mosby, 1994:168-169. Shapiro PA, Kokich VG. Uses of implants in orthodontics. Dent Clin North Am 1988:32:539-550. Sherwood KH, Burch JG, Thompson WJ. Closing anterior open bites by intruding molars with titanium miniplate anchorage. Am J Orthod Dentofacial Orthop 2002; 122:593-600. Sugawara J, Baik UB, Umemori M., Takahashi I, Nagasaka H, Kawamura H, Mitani H. Treatment and post-treatment dentoalveolar changes fol- lowing intrusion of mandibular molars with application of a skeletal anchorage system (SAS) for open bite correction. Int J Adult Orthod Orthognath Surg 2002; 17:243-253. Sung JH, Kyung HM, Bae SM, Park HS, Kwon OW, McNamara JA Jr. Microimplants in Orthodontics. Daegu, Korea: Dentos Ltd., 2006. Umemori M., Sugawara J, Mitani H, Nagasaka H, Kawamura H. Skeletal anchorage system for open-bite correction. Am J Orthod Dentofacial Orthop 1999; 115:166-174. 134 DISTALIZING MECHANICS WITH MODIFIED MINIPLATES Hugo De Clerck Marie Cornelis The main advantage of miniplate skeletal anchorage is its ability to be at- tached rigidly with two or three screws at a safe distance from the roots of the teeth. This makes it a good choice for distalization of the complete maxilla (De Clerck and Cornelis, 2006). Adult patients with moderate crowding, mild overjet or who already have had premolar extractions can be treated in this way. Miniplates are placed most commonly on the infrazygomatic crest of the maxillary buttress (De Clerck et al., 2002). The miniplate has three holes for the maxilla and two holes for the mandible. It is fixed to the bone by monocortical, 2.3 mm diameter screws, 5 or 7 mm in length. A round connection bar brings the point of force application close to the dental arch (Fig. 1). The bar perforates the soft tissues just below the mucogingival line. The attached gingiva adapts well around the round section of the connecting bar, with minimal risks for bacterial infiltration. Local infec- tion is responsible for bone loss and is the major reason for the loosening of skeletal anchorage devices (Choi et al., 2005). Positioning of the miniplate during surgery is the key to success. The screws should be placed on top of the infrazygomatic crest, and the lower part of the connecting bar should be below the mucogingival line (Fig. 2) and in contact with the bone surface (Cornelis et al., in prepara- tion). Depending on the angulation of the crest, the intraoral part will be positioned between the first premolar and the second molar. Therefore, the fixation unit is useful for changing the point of force application. The cylindrical fixation unit has two 0.045” diameter slots into which 0.032” x 0.032” stainless steel wire can be inserted and a blocking screw. Temporary skeletal anchorage devices do not support intermit- tent forces with variable direction and magnitude. During the first weeks after surgery these variable forces may be responsible for increased mo- bility, often with no signs of local infection. For this reason, patients should be instructed to not touch the bone anchor repeatedly with their tongues, and continuous orthodontic loading should be applied no later 135 Miniplate Mechanics than two weeks after surgery to neutralize the forces. Initial loading should not exceed 150 ch, but, if indicated clinically, it can be raised by 50 ch each month up to 300 ch. Fixed appliance should be bonded before mini- plate placement. Once the arches are leveled and aligned, the patient is referred to the surgeon. The patient should be informed about post-opera- tive swelling, which can last, on average, five days after surgery (Cornelis et al., in press). Figure 1. The miniplate (M) contains two holes for the man- dible and three holes for the maxilla. The round connecting bar (C) has two bends of 90°. The fixation unit (F) has two slots and a blocking screw (S). - Figure 2. Positioning of the miniplate during surgery. The Screws are inserted on the crest. The lower part of the connec- tion bar is facing attached gingiva and in contact with the bone surface. 136 De Clerck and Cornelis BIOMECHANICS OF DISTALIZING BUCCAL SEGMENTS Maxillary teeth usually are moved along the archwire by sliding mechanics. The forces are applied at the level of the bracket below the center of resistance, resulting in a moment of force and crown tipping (Fig. 3). The crown tip is limited by the clearance between the archwire and bracket and the elastic properties of the archwire. Contact between bracket and archwire on the inner mesial and distal boarder of the bracket slot results in binding. A force couple is generated and is responsible for root uprighting. Successive crown tip and root uprightings result in a translation of the tooth along the archwire (De Clerck and Cornelis, 2006). Friction related to the material properties of brackets, archwires and types of ligation also can restrict the sliding movement. For example, friction is higher for ceramic brackets than for metal brackets (Nishio et al., 2004) and is lower for stainless steel ligatures than for elastomers. Self-ligat- ing brackets eliminate the friction caused by ligation (Henao and Kusy, 2004), but binding still can occur. If several teeth are moved at once, the resistance against sliding will be the sum of friction and binding in each bracket. For this reason, we distalize the upper first and second molars initially. The upper arch is only partially bonded, i.e., the molars, canines and, when there is crowding, the most labially positioned incisors. Pro- viding indirect anchorage by means of a rigid connection from the skeletal anchorage to a premolar should be avoided. The molars also can be distal- ized by compressing an open coil spring against the first molar tube, acti- vated by a ligature or rigid connection fixed to the skeletal anchorage (Fig. 4). However, unwanted vertical components of force may be created, and if the connection to the bone anchor fails, anchorage loss may occur due to the pressure of the coil spring against the mesial side of the canine bracket. In a later stage, we used sliding jigs. However, a labial rolling of the sliding jig often was observed generating irritation of the upper lip. To overcome these disadvantages, we now prefer to use a closed coil in combination with a sliding hook (De Clerck and Cornelis, 2006). The section of the tube of the sliding hook should be round to avoid unwanted torque of the archwire by rolling of the hook and the hook should be very short to avoid irritating the soft tissues. We use a 150 cm, nickel titanium coil spring fixed between the sliding hook and the fixation unit of the bone anchor, which pushes the sliding hook against the closed coil spring and the coil spring against the molar tube. The horizontal force generates a distal crown tipping of the first molar and 137 Miniplate Mechanics binding between the archwire and tube (Fig. 5). This, in turn, creates friction, which pulls the archwire distally and explains why the canines partially move with the molars spontaneously (Cornelis and De Clerck, in press). Figure 3. Top: The force applied at a distance from the center of resistance (CR) results in a crown tipping. Bottom: A couple of force generates a moment and uprighting of the root. 138 De Clerck and Cornelis Figure 4. A: Rigid extension from the fixation unit compresses an open coil Spring. B. A sliding jig is pushed against the molar tube. C. A combination of a sliding hook with a closed coil spring. Figure 5. The molars are distalized by the pressure of a closed coil against the first molar tube (Fm). Binding in the molar tube pulls the archwire distally (Fa) and results in canine distalization (Fe) and reduction of the overjet. The Premolars are displaced (Fpm) by traction of the supracrestal fibers. - A reduction of the overjet should be observed as long as there * no initial contact between the upper and lower incisors. If the molars * Only distalized on one side, the midline will shift to that side (Fig. 6). 139 Miniplate Mechanics Since premolars are not bonded, they spontaneously migrate distally thanks to the stretching of the supracrestal periodontal fibres as long as there are no occlusal interferences. The intercanine and intermolar widths increase during molar distalization; the more the teeth are moved back- ward, the wider the arch becomes. Furthermore, from an occlusal view, the direction of the traction is slightly oriented to the outside, pulling the canines labially (Fig. 7). A rotation around the palatal root of the upper molar also contributes to the increase in intermolar width. Therefore, the second molars always should be bonded. Figure 6. Spontaneous shift of the upper midline during unilateral distalization of the molars. Figure 7. The intercanine width is increased by a horizontal component of force (Fh). A horizontal bend (Hb) is made at a distance from the Second molar tube. 140 De Clerck and Cornelis The archwire should not be cut immediately behind the second molar tube as this might cause irritation and impingement of the soft tis- Sues when the end of the archwire slides into the tube. We recommend bending the wire parallel to the occlusal plane 3 to 5 mm distal from the molar tube. The length of the wire extending beyond the molar tube be- comes shorter during the molar distalization process. Therefore, every two to three months, the archwire should be replaced with a longer one. Since the binding in the molar tubes may be not equal on the left and right sides, the archwire may be pulled to one side causing irritation of the cheek and blocking the molar distalization on the other side. To avoid this, a double stop always should be made in the archwire against the mesial side of the brackets of both central incisors (Fig. 8). This eventually may result in space being added between both incisors. º - - º … - - Figure 8. A stop is made in the archwire mesial to the brackets of each central incisor. Once both molars have been moved into an overcorrected Class I occlusion, the premolars and the remaining incisors can be bonded. After levelling, the canines are distalized along the archwire until a Class I oc- clusion is achieved. A coil spring is directly fixed between the skeletal anchor and the canine bracket. To avoid rotation of the canine and to minimize friction, only the distal wings of the bracket are tied by a stain- less steel ligature. The movement of both canines and premolars is time ºnsuming and may be restricted by occlusal interferences. This some- times requires the fixation of the first molar by a ‘molar holding spring a small piece of wire in the fixation unit that slightly pushes the molar tube distally to avoid anchorage loss. 141 Miniplate Mechanics During canine retraction and distal crown tipping, the anterior segment of the archwire is pulled downward, which results in an increased overbite. Bite opening is postponed until a stable Class I occlusion of the canines is obtained. With a T-loop arch, the four incisors are intruded and distalized immediately (Fig. 9). This generates reaction forces that extrude the canines, which is limited by interdigitation with the lower ca- nine and first premolar. It is recommended, therefore, to compress the archwire slightly in the canine region. The T-loop is activated by pulling the archwire distal to the first molar tube and bending it upward. The reaction force responsible for rotating the molar around its palatal root is limited by a transpalatal arch. In order to avoid anchorage loss, a coil spring is maintained between the canine and the skeletal anchor. When there is a deep curve of Spee in the lower arch, as often is observed in Class II, division 2 cases with over-erupted incisors, it should be flattened to reduce the overbite. For an efficient leveling of the curve of Spee, the lower second molars should be bonded. Elimination of the curve of Spee always results in protrusion of the lower incisors, which restricts the use of Class II elastics. Figure 9. Retraction and intrusion (Fi) of the upper incisors by a T-loop arch. Extrusion of the canine (Fc”) is limited by the occlusion. The Class I occlusion is maintained by a distalizing force from the skeletal anchor to the upper canine (FC). Molar rotation (Mm”) is restricted by a transpalatal arch. Six to eight months are needed to reach a Class I molar occlu- sion, depending on the severity of the Class II malocclusion (Cornelis and De Clerck, in press). However, the time needed to move the canines 142 De Clerck and Cornelis and premolars into a Class I occlusion may take an additional six months. For this reason, we began distalizing both molars and premolars at the same time. In patients with crowding, we bonded only part of the incisors to avoid labial tipping and to increase the overjet during the initial level- ing stage. Stainless steel ligatures are fixed around the distal wings of the brackets of the canine and the first and second premolars (Fig. 10). Ini- tially, a 150 ch force is used and is sometimes increased to 200 ch. Dis- talizing the molars and premolars together does not take two months more than distalizing molars alone. The canines partially follow the movement of the first premolar, and the overjet is reduced as long as there is no oc- clusal interference from the lower incisors. Figure 10. Distalization of the molars and premolars at the same time. Steel ligatures are fixed around the distal wings of the premolar brackets. Another difference between miniplate skeletal anchorage and Conventional anchorage is the ability to apply intrusive forces to the an- terior segment without causing adverse reaction forces to the rest of the dentition. An auxiliary intrusion arch can be inserted directly into the fixation unit of the skeletal anchor and ligated to the incisors. Applying Vertical force to the brackets of the incisors, at a distance from their center of resistance, can result in labial tipping. This does not happen thanks to the fiction generated by the distalizing mechanics in the buccal segments. Correcting an open bite in an earlier stage of treatment will result in a seater reduction of the overjet during molar distalization. 143 Miniplate Mechanics DISCUSSION Most commonly, headgear is used to distalize upper molars. Heavy forces are applied during the night and interrupted during the day. When cervical traction is used, the vertical component of force may re- sult in some extrusion and bite opening (Ulger et al., 2006). Although a spontaneous drift of the premolars also is observed, the overjet will not be affected. Once the molars have been moved into a Class I occlusion, fixed appliances are bonded. Chain elastics fixed between the anterior segment and the first molar will cause some anchorage loss of the newly distalized molars. This usually is compensated for by using Class II elastics, which may cause protrusion of the lower incisors. ‘. A majority of Class II cases treated without extractions initially have crowding of the upper incisors. Leveling the incisors at the begin- ning of treatment results in an increased overjet, the correction of which will require supplementary anchorage and a longer treatment time. There- fore, only the most labially positioned incisors should be bonded. During distal migration of the canines, space is created for the remaining incisors. This results in a spontaneous unraveling and alignment (Fig. 11). Only when crowding is eliminated should the remaining incisors be bonded. When a modified miniplate is used to distalize the molars, light, continuous forces can be used without the need for patient compliance (Cornelis and De Clerck, in press). Once molar distalization has been achieved, the canines and premolars are moved back without using the previously distalized molars for anchorage, limiting the risk for anchor- age loss. However, closing the remaining spaces between the molars and premolars may be time-consuming. This problem can be avoided by dis- talizing the premolars and molars at the same time, but this will increase friction and resistance to sliding. In order to avoid rotation of the premolars, the distal wings of the edgewise brackets should be tied to the archwire by a 0.010” stain- less steel ligature. When the buccal segments are distalized, it results in friction and binding at the interface between bracket and archwire and continuous posterior traction on the incisors occurs. The overjet will be reduced as long as there is no contact with the lower teeth (Fig. 12). Moreover, the overbite may increase during distal movement of the buc- cal segments and canting of the occlusal plane, which is favorable in open-bite cases but is unwanted in deep-bite cases. For this reason, it might be interesting to add some intrusive force to the incisors at an early 144 De Clerck and Cornelis Figure 11. A: The start of molar distalization. B: Spontaneous distal drift of the premolars. Distal movement of the canines and reduction of anterior crowding. C. Spacing for the lateral incisors. D. Enlargement of the lateral incisors by composites. Stage of treatment instead of correcting the deep bite with T-loop arches Once a Class I canine occlusion is obtained. When a miniplate is used as anchorage, an auxiliary intrusion arch can be fixed to the skeletal anchor without producing any side ef- fects on the molars. Some extra intrusion also can be obtained thanks to the upward inclination of the line of force connecting the anterior seg- ment to the skeletal anchor, intruding the anterior part of the dental arch and opening the bite. The combination of an intrusive force and the re- traction force generated by friction in the buccal segments results in bite opening and reduction of the overjet without producing any adverse effect on the molars. This absolutely improves efficiency of the correction of Class II cases. Depending on the severity of the initial Class II malocclu- Sion, a molar and premolar Class I occlusion can be obtained after six to nine months; the canines follow part of the movement, the crowding of the incisors is eliminated and the overjet and overbite are reduced. The Space between the canine and first premolar is further closed by sliding mechanics, i.e., connecting a coil spring from the canine to the skeletal anchor. The remaining overbite and overjet are corrected by a T-loop 145 Miniplate Mechanics arch in the upper jaw and by leveling the curve of Spee in the lower arch. The final occlusion is obtained by finishing steps in a continuous archwire combined with intermaxillary elastics to improve the interdigitation. - - - - - - - - - - - - º - Figure, 12. Left: Class II occlusion at the start of treatment. Right: After molar distalization: Spontaneous distal drift of the canine and premolars. Reduction of the Sagittal overbite. CONCLUSIONS Skeletal anchorage is much more than an alternative treatment choice to headgear. It needs an adapted biomechanical approach. In com- bination with a better understanding and control of friction, treatment ef- ficiency can be greatly improved with skeletal anchorage. Absolute an- chorage with no need for patient compliance opens new perspectives for treatment of Class II malocclusions without extractions. REFERENCES Choi BH, Zhu SJ, Kim YH. A clinical evaluation of titanium miniplates as anchors for Orthodontic treatment. Am J Orthod Dentofacial Orthop 2005; 128:382–384. Cornelis MA, De Clerck H.J. Maxillary molar distalization with miniplates assessed on digital model: A prospective clinical trial. Am J Orthod Dentofacial Orthop, in press. Cornelis MA, Scheffler NR, De Clerck HJ, Tulloch JFC. Modified mini- plates used for temporary skeletal anchorage in orthodontics: Place- ment and removal surgeries. J Oral Maxillofac Surg, in preparation. Cornelis MA, Scheffler NR, Nyssen-Behets C, De Clerck HJ, Tulloch JFC. Patients and orthodontists perceptions of miniplates used for tempo- rary skeletal anchorage. A prospective study. Am J Orthod Dentofacial Orthop, in press. 146 De Clerck and Cornelis De Clerck HJ, Geerinckx V, Siciliano S. The zygoma anchorage system. J Clin Orthod 2002:36:455-459. De Clerck HJ, Cornelis MA. Biomechanics of skeletal anchorage. Part 2: Class II nonextraction treatment. J Clin Orthod 2006;40:290–298. Henao SP, Kusy RP. Evaluation of the frictional resistance of conventional and self-ligating bracket designs using standardized archwires and dental typodonts. Angle Orthod 2004;74:202-211. Nishio C, da Motta AF, Elias CN, Mucha JN. In vitro evaluation of fric- tional forces between archwires and ceramic brackets. Am J Orthod Dentofacial Orthop 2004;125:56-64. Ulger G, Arun T. Sayinsu K, Isik F. The role of cervical headgear and lower utility arch in the control of the vertical dimension. Am J Orthod Dentofacial Orthop 2006;130:492-501. 147 TEMPORARY SEELETAL ANCHORAGE: THE EXPERIMENTAL LITERATURE Marie A. Cornelis Hugo J. De Clerck Catherine Nyssen-Behets J. F. Camilla Tulloch One important challenge in orthodontics is to find sufficient anchorage to achieve planned tooth movements. Conventional approaches take advan- tage of the biological potential of the dentition, frequently in combina- tion with compliance dependent devices such as intermaxillary elastics or headgear. Anchorage possibilities are reduced in adult patients with partial edentulism and/or periodontally compromised dentitions. The develop- ment of skeletal anchorage systems has increased the orthodontic treat- ment possibilities and reduced dependence on patient compliance (Creek- more and Eklund, 1983). Conventional dental implants, when used to provide absolute an- chorage (Higuchi and Slack, 1991; Willems et al., 1999), quickly were Seen to have the disadvantage of high cost and significant space require- ments. This argued in favor of developing implants that could be placed outside the dental arch and that were designed specifically for orthodontic needs. Retromolar (Roberts et al., 1990) and palatal implants (Wehrbein et al., 1996, 1999a) were introduced later, but their use is restricted to specific locations; they are expensive, they require three months of healing to allow for osseointegration before orthodontic loading, and they provide only indirect anchorage. Smaller, cheaper devices such as miniscrews (Costa et al., 1998; Melsen and Costa, 2000) and miniplates (Jenner and Fitzpatrick, 1985; Sherwood et al., 2002), which can be placed in various locations within or adjacent to the dental arch, allow wider orthodontic applications and are associated with less surgical trauma and shorter healing time. These devices, grouped under the term of temporary skeletal anchorage devices (TSADs), are documented in the clinical literature mostly by case reports or case series (Sugawara et al., 2002, 2004; Miyawaki et al., 2003; Cheng et al., 2004; Liou et al., 2004; Ari-Demirkaya et al., 2005; Choi et al., 2005; Park et al., 2006; Tseng et al., 2006; Kuroda et al., 2007a,b; Luzi et al., 2007; Cornelis et al., 2008). 149 TSAD Experimental Literature Miniscrews, which are small and frequently placed by the ortho- dontists themselves (Freudenthaler et al., 2001; Park et al., 2003, 2005; Giancotti et al., 2004; Park and Kwon, 2004; Schnelle et al., 2004; Hong et al., 2005; Poggio et al., 2006), are associated with a high failure risk when placed in unattached gingiva (Miyawaki et al., 2003; Cheng et al., 2004; Liou et al., 2004) and root injury when placed in keratinized mucosa (Park et al., 2003). While root impingement is less probable with smaller screws, the risk of failure (Miyawaki et al., 2003) and screw fracture dur- ing placement (Buchter et al., 2005) increases as screw diameter decreas- es. Unscrewing moments must be avoided during force application (Costa et al., 1998), and miniscrews may need to be repositioned during treatment to allow complete tooth movements. Orthodontic miniplates are surgical osteosynthesis plates modified to allow a connection to an orthodontic appliance (Jenner and Fitzpatrick, 1985; Umemori et al., 1999; Chung et al., 2002; De Clerck et al., 2002; Sherwood et al., 2002; Sugawara et al., 2002, 2006; Choi et al., 2005; Cornelis and De Clerck, 2006; Erverdi et al., 2006). Miniplates present some advantage in that the fixation screws are placed at a safe distance from the roots, while the connection to the orthodontic appliance still is located in attached gingiva close to the dental arch. The roots, therefore, can slide past the device and en masse distalization of an entire dental arch can occur (De Clerck and Cornelis, 2006). Clinical reports suggest that miniplates have lower failure rates than miniscrews (Miyawaki et al., 2003). Miniplates also may provide more secure anchorage when higher forces such as orthopedic forces are needed (Kircelli et al., 2006). How- ever, miniplate placement requires flap elevation, so placement usually is carried out by an oral surgeon or periodontist. Clinical studies provide some evidence concerning the relative success rate, orthodontic indications and efficiency of these devices, but questions regarding the factors influencing TSAD stability or the bone re- sponse to orthodontic loading remain largely unanswered by the clinical orthodontic literature alone. Dental implants have been well-described in the prosthodontic literature, but there are substantial differences between prosthetic and orthodontic anchors: conventional prosthodontic implants generally are loaded only after osseointegration has occurred and are intended to be in place permanently; miniscrews and miniplates usually are loaded long before osseointegration can be achieved and are intended to be removed relatively soon after initial placement. Conventional implants are subject to the high intermittent forces of mastication, while forces to miniscrews 150 Cornelis et al. and miniplates are light and continuous. The direction of loading and di- mensions of the devices also vary between the systems. These fundamen- tal differences raise several important questions about the use of implants for orthodontic anchorage that may be clarified by reference to the experi- mental literature. Studies to determine the functional and morphologic tissue reac- tions around orthodontically loaded TSADs have been conducted in a va- riety of animal models. These studies are important because they gener- ally are controlled and frequently allow histologic evaluation of the bone implant interface and the response of tissues to force. However, there are some important factors that need to be considered when translating the results of experimental studies in animals to the clinic, such as: • differences between humans and animals in the rate of turno- Ver that results in the transformation of immature bone into ma- ture load-resistant bone; • the body mass of the experimental animal relative to the mag- nitude of the load delivered; and • the location of the implant in the different experimental mod- els. Currently, three types of orthodontic anchors have been studied in animals: conventional, palatal or retromolar implants; miniscrews with a 2.2 mm diameter or less; and bone plates. The literature concerning the ex- perimental use of miniscrews and miniplates has been reviewed recently (Cornelis et al., 2007), but data from orthodontically loaded conventional, palatal or retromolar implants was not included. Interesting insights can be gained by including information about these particular precursor implants, and new information on plates and screws now is available. The PubMed electronic database was the primary source of the relevant literature included in this systematic review. Only those articles that reported on animal studies using orthodontically loaded, intraosse- ous, metal TSADs have been included for a total of 34 studies. Articles on extraosseous implants, wires or onplants, as well as articles involving distraction were excluded. The articles were divided into three groups: animal studies testing dental, palatal or retromolar implants under orth- odontic load (Table 1); animal studies using miniscrews (Table 2); and animal studies with orthodontic miniplates (Table 3). The information is summarized to address the specific issues of stability, and tissue response to loading. 151 TSAD Experimental Literature Table 1. Studies testing implants: sample and implant characteristics; loading protocols and outcomes. No. No. of No. of Length Authors & Animal of & nCn- x dia- & - loaded Manufacturer year published model * | TSADs loaded meter mals TSADS (mm) 1 Akin-Nergiz et Dog 3 6 12 Bonefit, Strau- 12 x al., 1998 mann, Switzerland 4.1 2 Aldikacti et Dog 5 6 2 Straumann, 10 x al., 2004 Switzerland 4.1 3 Asikainen et Sheep 5 20 0 Straumann, 4.5 x al., 1997 Switzerland 3.5 4 Cattaneo et al., | Monkey 4 14 2 Exacta, Biaggini 7 x 3.3 2007 Med. Devices, Italy 5 Fritz et al., Dog 4 15 1 Orthosys., Strau- 4 x 3.3 2003 mann, Switzerland 6 Gotfredsen et Dog 3 18 6 ITI Dental Implant | 8 x 3.3 al., 2001 a Sys., Straumann, Switzerland 7 Gotfredsen et Dog 3 12 0 Straumann, 8 x 3.3 al., 2001b Switzerland 8 Gotfredsen et Dog 3 36 () ITI Dental Implant | 8 x 3.3 al., 2001c Sys., Straumann, Switzerland –msº 9 Hürzeler et al., | Monkey 5 20 20 Nobel Biocare, 7 x 1998 Germany 3.75 10 Liang et al., Dog 2 12 () BAM, Huashen, 10 x 1998 China 3.5 11 || Liang et al., Dog 2 24 0 BAM, Huashen, 13 x 1999 China 3.5 12 Linder- Monkey 2 2 0 Biotes, Nobel- 7 x Aronson et al., pharma, Sweden Ulfl- 1990 known 13 | Majzoub et al., | Rabbit 10 16 4 Not reported 3.25 x 1999 4 14 Oyonarte et Dog 5 20 10 Innova Corpora- 5 x 4.1 al., 2005a,b tion, Canada 15 Roberts et al., Rabbit 14 28 28 Not reported 8 x 3.2 1984 16 || Roberts et al., | Rabbit" | 6*, 12*, 12*, Not reported 7x32 1989 Dog” 4++ 8++ 8++ Biotes, Nobel- 13 x pharma, Sweden 3.75 17 Saito et al., Dog 4 8 8 Not reported 7 x 2000 3.75 18 Southard et Dog 8 8 0 Nobelpharma, 10 x al., 1995 Chicago, Illinois 3.75 19 Turley et al., Dog 6 8 34 Not reported 6 x 2.4 1988 & 4.75 20 Wehrbein & Dog 2 8 4 Brănemark 10 x - Diedrich, 1993 3.75 21 Wehrbein et Dog 2 6 4 Bonefit, Strau- 6 x 4 al., 1997 mann, Switzerland sº 22 Wehrbein et Dog 2 6 4 Bonefit, Strau- 6x4 al., 1999b mann, Switzerland ſº 152 Cornelis et al. Table 1. Continued. Ti Lengt e Osseointe- 1me h of Failures gration & TSAD before Force before/ º Material e s load- index-loaded location loading (g) * after (wks) 1ng loading & Stable (wks) TSADs (%) 1 Titanium Mandible 12 500 36 0-0 40-56 2 Titanium/ Maxilla/ 6 200 52 0–0 40-49 SLA surface mandible 3 Titanium/ Forehead 15 250-350 12 0–3/20 NA TPS Surface 4 Titanium/ Maxilla/ 17 50 16 0–0 52–86 Sandblasted mandible , surface 5 Titanium/ Maxilla/ 24 50-200 12 4/16-0 NA SLA surface mandible 6 Titanium/ Mandible 12 NA9 24 0–0 66 TPS Surface 7 Titanium/ Mandible 12 NA9 24 0-0 53–60 TPS Surface/ uncoated 8 Titanium/ Mandible 12–48 NA9 10-48 0–0 81–83 TPS surface 9 Titanium Mandible 16 300 26-32 NA 57 10 Titanium/ Mandible 12 150 13 0–0 NA HA surface 11 Titanium/ Femur 12 200 8 0-0 NA HA surface/ TPS surface/ uncoated 12 Titanium Mandible 8 60 8 0–0 NA 13 Titanium Calvaria 2 150 8 0–1/16 75 14 Ti-6Al-4V Mandible 7 300 22 0-1/20 50-72 alloy/porous- Surface/ uncoated 15 Titanium/ Femur 0-6-12 100 4-8 0–9/28 NA acid etched 16 Titanium/ Femurº 6*, 100% 4+ 0-0% >50% acid-etched: Man- 8** 300++ 13 ** 1/16-0++ –24** | | titanium dible+* 17 | Titanium Mandible 18 200 24-32 0-0 70 18 Titanium Mandible 12 50-100 16 0-0 NA 19 Titanium/ Mandible/ 10–24 300- 7-18 18/42-0 NA acid etched maxilla/ 1000 temporal/ Zygoma 20 Titanium Maxilla/ 25 200 26 0-0 NA *= mandible 21 Titanium Maxilla 8 100-200 26 0-0 NA 22 Titanium Maxilla 8 200 26 0-0 NA *The orthodontic force was described as being generated by an expansion device and was not –4*ntified; only the distance and frequency of activation were reported. 153 TSAD Experimental Literature Table 2. Studies testing miniscrews: rotocols and outcomes. Sample and implant characteristics; loading Authors & Ani No. No. of No. of Length x nimal of nC)n- dia- year pub- model ani- loaded loaded Manufacturer meter lished mals TSADS TSADS (mm) Buchter et al., | Minipig 8 160 32 Absoanchor", 10 x 1.1/ 2005 Dentos; Dual- 10 x 1.6 Topº, Jeil - Korea Buchter et al., | Minipig 8 160 32 Absoanchor", 10 x 1.1/ 2006 Dentos; Dual- 10 x 1.6 Topº, Jeil - Korea Deguchi et Dog 8 48 48 Stryker Leibinger, 5 x 1 al., 2003 Kalamazoo, Mich. Kim et al., Dog 2 32 () Osas, Epoch NA X , 2005 Medical, Korea 1.6 Melsen & Monkey 4 16 0 Aarhus Screw, 8 x 2.2 Costa, 2000 Medident, Denmark Melsen & Monkey 6 10 2 Straumann, 6 x 2.2 Lang, 2001 Switzerland Morais et al., Rabbit 18 36 36 Conexao Sistemas 6 x 2 2007 de Proteses, Brazil Ohmae et al., Dog 3 12 24 Sankin, Japan 4 x 1 2001c Yano et al., Rat 20 20 20 ISA Orthodontic 4 x 1.2/ 2006 Implants, Biodent, 4 x 1.4 Japan Table 3. Studies testing miniplates: sample and implant characteristics; loading protocols and outcomes. Authors & g No. No. of No. of Length x Animal of Il OIl- dia- year pub- tº loaded Manufacturer lished model * | TSADs loaded meter mals TSADS (mm) Cornelis et Dog 10 40 40 Bollard, Surgi- 5 x 2.3 al., in press Tec, Belgium (2/plate) a,b ==== Daimaruya et Dog 6 6 6 Sankin, Japan/ 5/7 x 2 al., 2001 Leibinger, (3/plate) Germany Daimaruya et Dog 6 6 6 Sankin, Japan/ 5/7 x 2 al., 2003 Leibinger, (3/plate) Germany 154 Cornelis et al. Table 2. Continued. Time Length Failures Osseointe- Materi TSAD before Force of before/ gration aterial l te º e index-loaded OCation loading (g) loading after & stable (wks) (wks) loading TSADs (%) 1 Titanium' - Mandible 0 100- 3-10 0–5/160 NA Ti-6Al-4V 300- alloy” 500 2 Titanium' - Mandible 0 100- 3-10 0–5/160 49–86 Ti-6Al-4V 300- alloy” ſº 500 3 Titanium Maxilla/ 3-6-12 200- 12 3/96-0 31-40 mandible 300 4 Titanium Maxilla/ 1 200- 11 NA-3/32 23–44 mandible 300 5 Titanium Maxilla/ 0 25–50 4-8-16- 0–2/16 10–58 Vanadium mandible 24 6 Titanium/ Mandible 12 100- 11 0-0 40–45 TPS surface 200- 300 7 Ti-6Al-4V Tibia 0 100 1-4-12 0–3/30 NA alloy 8 Titanium Mandible 6 150 12-18 0-0 25 9 Titanium Tibia 0-6 200 2 NA-3/20 33-88 Table 3. Continued. Time Length Failures * Material TSAD before | Force of * index-loaded location loading (g) loading fore/after & stable (wks) (wks) loading TSADs (%) 1 Plates: tita- Maxilla/ 2 125 5-27 2/80- 1-77 nium/screws: mandible 17/40 Ti-6Al-4V alloy 2 Titanium Mandible 12 100- 16-28 0-0 NA *-l– 150 3 Titanium Maxilla 12 80-100 16-28 0-0 NA 155 TSAD Experimental Literature STABILITY Failure rates varied widely from 0% to 43% in studies with con- ventional implants (Table 1), 0% to 15% for miniscrews (Table 2) and 0% to 42% for miniplates (Table 3). In general, one might expect a higher success rate in humans than animals, since hygiene and compliance should be easier to control. Based on this systematic review, we can hypothesize Some factors determining stability, including healing time, magnitude of load, soft tissue inflammation and screw-to-root contact. Healing Time One important issue facing clinicians is determining the optimal time before loading a TSAD. The healing times reported vary between 0 and 48 weeks for implants (Table 1), 0 and 12 weeks for miniscrews (Table 2) and 2 and 12 weeks for miniplates (Table 3). Implants. In the rabbit model, clinically acceptable stability is apparently achieved after a short healing time (two weeks), with a high percentage of direct bone-to-implant contact (Majzoub et al., 1999). An initial healing time of six weeks without loading was thought to be neces- sary by Roberts and coworkers (1984), since direct bone-implant contact depends not only on rigidity at the point of insertion into vital bone, but also on the mechanical stability obtained during the first weeks of healing. They observed spontaneous fractures and 100% implant failure after im- mediate loading in rabbit femurs and concluded that immediate loading is not indicated in any animal species. However, the applied load was high (100 g) and the implant large with reference to the size of animal. Miniscrews. In dogs, three, six and twelve weeks of healing pe- riods were compared. The authors concluded that a three-week healing period is sufficient for orthodontic loading (Deguchi et al., 2003). When this is transposed to the human bone remodeling cycle, it corresponds to a four to five week healing period being sufficient to allow resistance to the light forces generally used in orthodontic tooth movement. This raises the question as to whether immediate loading could or should be recommended. Five of the animal experiments (Table 2, au- thors 1, 2, 5, 7 and 9) reported immediate loading. In general, the suc- cess rates were very high, varying from 89% to 97%. Supporting this conclusion, Yano and co-workers (2006) found no difference in bone- implant contact between immediately loaded tapered miniscrews and the 156 Cornelis et al. same screws loaded after a sz-week healing period. In addition, Morais and colleagues (2007) did not find any increase in removal torque values between one and four weeks of healing, although they did note that af- ter 12 weeks, the removal torque values increased significantly, perhaps suggesting favorable bone changes with increased time. Finally, Huja and colleagues (2006) showed that pullout strength stresses of miniscrews did not differ between immediate placement and six weeks post-insertion, supporting the concept of immediate loading. This finding is not cited in Table 2 because the implants remained unloaded in Huja’s experiment. Implant stability depends on the initial degree of mechanical sta- bility achieved at placement. Mechanical stability depends on the thickness of the cortical bone (Huja et al., 2005, 2006), the implant site preparation – the larger the pre-drilling diameter, the lower the primary stability – and the screw design (Wilmes et al., 2006). Tapered screws seem to provide better primary stability than straight screws (Yano et al., 2006). Implant stability can be optimized by using a non-drilling procedure, since a high- er bone-to-implant ratio was found to be correlated with the absence of preliminary drilling when compared to a procedure that required drilling before placement (Kim et al., 2005). This finding was confirmed by two in vitro studies that suggested pre-drilling procedures should be required in all regions of high bone density such as thick cortical bone (Lohr et al., 2000; Wilmes et al., 2006), whereas non-drilling procedures perform bet- ter in cancellous bone (Lohr et al., 2000). Miniplates. None of the miniplate experiments used immediate loading. One team loaded the miniplates after 12 weeks (Daimaruya et al., 2001, 2003) and the other after two weeks (Cornelis et al., in press a,b), which corresponds to the healing time of three weeks recommended by the same authors in patients (De Clerck and Cornelis, 2006). In this study, mobility occurred, on average, five weeks after implantation, which might represent the critical stage of transition between primary and secondary stability (Schenk and Buser, 1998). If correct, this observation would sug- gest that loading should be planned either earlier or later than five weeks, but not close to that specific time point. It is apparent that surgical technique is important to the enhance- ment of primary stability. Woven bone was observed as a repair proc- ess when the initial hole had to be redrilled on a slightly different axis (Cornelis et al., in press b). Since this re-drilling procedure is likely to produce some instability, a drill-free technique might be preferred. Hei- demann and colleagues (2001) showed that screw-bone contact with 157 TSAD Experimental Literature drill-free screws was superior to that of self-tapping screws used for osteo- synthesis after orthognathic surgery or fracture. Magnitude of Load With regard to the selection of appropriate forces, the experimental studies report such a wide variation in forces, particularly when consider- ing the size of the experimental animals, that interpretation of the findings is difficult. It is impossible to determine from the evidence so far available what the lower and upper thresholds might be for switching a positive bal- ance to a negative one. This is an important area for future research, since the application of TSADs in orthodontics already has broadened to include such applications as single tooth or whole arch intrusion and orthopedic correction of skeletal problems. These applications may all call for very different force systems, but the threshold for bone resorption or negative remodeling still is not known clearly. Implants. A majority of the studies tested forces ranging from 50 to 350 g, and very few failures were noted (Table 1). The one study that showed a higher failure rate used forces ranging from 300 to 1000 g, although it was not clearly shown that increased load was associated with failure (Turley et al., 1988). Miniscrews. The forces that were tested ranged from 25 to 500 g (Table 2). Using finite element analysis correlated to histological results (Melsen and Lang, 2001) suggests that both very low and very high strain values resulted in a high incidence of resorption and a negative remodel- ing balance. Between these extremes, an increase in strain was followed by an increase in bone remodeling, which generated a positive balance. In minipigs, mobility was observed with a 300 g loading force, whereas no mobility was reported with a 100 g loading force (Buchter et al., 2005, 2006). Miniplates. The forces tested varied between 80 and 150 g (Table 3), and loading appeared to have no definite effect on stability, since the success rate was not significantly different for loaded vs. nonloaded plates (Cornelis et al., in press a). Soft Tissue Inflammation The clinical literature shows that prevention of inflammation of the peri-implant tissue is a critical factor for miniplate success (Choi et al., 2005; Miyawaki et al., 2003). Sato and colleagues (2007) recently reported that crevices around titanium orthodontic plates in patients sup- 158 Cornelis et al. ported the anaerobic growth of bacteria likely to stimulate peri-implant inflammation leading to implant loosening. Implants. Mild clinical inflammation was noted in most of the studies, but there were no reports of severe inflammatory reactions. At the microscopic level, most authors reported no inflammation in the interface zone, except for in the marginal area where inflammation due to gingivitis was observed frequently. An early study in dogs suggested that implant placement in non-keratinized tissue constitutes a risk factor, because it might generate soft-tissue inflammation (Turley et al., 1988). Miniscrews. The highest rate of screw mobility was reported in the only study that placed screws in non-keratinized mucosa (Melsen and Costa, 2000), suggesting that placement in non-keratinized mucosa might be a risk factor. In contrast, immediate loading of submerged TSADs (screws and coil-springs completely covered by soft tissues) had a low failure rate (only five out of 160 TSADs; Buchter et al., 2005), suggesting once again the key role played by the soft tissues. Miniplates. Miniplate mobility was reported to be systemati- cally associated with gingival inflammation (Cornelis et al., in press, a), although one other study showed slight inflammatory changes at the trans- mucosal area but reported no failures (Daimaruya et al., 2001, 2003). Screw-to-Root Contact In the clinical literature, root proximity has been proposed as a major risk factor for miniscrew failure (Kuroda et al., 2007b). An experi- ment in dogs (not included in the review since no loading was applied on the orthodontic miniscrews) showed that the repair of the periodontal structure was almost complete within 12 weeks after the root damage was caused by the screws (Asscherickx et al., 2005). For all three types of TSADs, implant root contact was reported so infrequently that conclu- sions drawn were tenuous at best. TISSUE RESPONSE TO LOADING The effect of loading on bone healing around implants is of criti- cal importance; a negative effect might decrease TSAD stability, where- as a positive effect could compromise the ease of removal of the device once it is no longer needed. The effect of loading on bone-implant con- tact and bone remodeling has been discussed in the literature. Huja and 1.59 TSAD Experimental Literature colleagues (1999) hypothesized that remodeling around implants gener- ates a compliant layer of bone preventing microdamage accumulation and allowing long-term success of endosseous implants. Microcalli have been observed in clinical conditions and attributed to microrepair after ortho- dontic load (Trisi and Rebaudi, 2002). With regard to the effect of load on Osseointegration, the strain levels generated by orthodontic treatment are considerably lower than occlusal forces and lower than the adapted win- dow magnitudes (Frost, 1990), suggesting an absence of effect of load on bone-implant contact (Cattaneo et al., 2007). Implants. The reported bone-implant contact in the studies varied from 24% to 86% (Table 1). Minimal integration index related to stabil- ity of orthodontically loaded implants was reported to be 10% (Roberts et al., 1989). High bone remodeling was observed by most of the authors (Table 1: 2, 4–8, 16, 19) around loaded and nonloaded implants. Loading increased bone remodeling (Table 1: 1, 4, 15, 20–22), although the six studies reporting quantitative data did not show a statistically significant effect of orthodontic load on bone-implant contact (Table 1: 2, 9, 13, 14, 16, 17). The type of stress applied, whether compression or tension, was not associated with difference in bone response in nine of the studies (Ta- ble 1: 2, 6, 8, 13, 14, 17, 20–22). Thus, the hypothesis that the degree of Osseointegration is affected by load is not supported by the quantitative analyses currently available. It may be that the morphometric techniques used to determine integration indices differ so widely among studies that unequivocal conclusions cannot be drawn about the relationship between load and Osseointegration. The effect of coating around regular implants has been stud- ied. Hydroxyapatite- (HA-) coated implants had the highest shear bond strength compared to titanium plasma sprayed- (TPS-) implants and un- coated implants (Liang et al., 1999). TPS-implants (Gotfredsen et al., 2001b) and porous-surface implants (Oyonarte et al., 2005a,b) showed increased bone-implant contact compared to machined-surface implants. From these studies, we can speculate that uncoated implants might be pre- ferred as they may help prevent excessive osseointegration and the need for complicated surgery to remove the implants. Miniscrews. Bone-implant contact varied from 25% to 86% (Table 2). Thus, titanium screws do resist orthodontic forces in general, maintaining their initial positions without marginal bone loss. This con- tradicts some clinical studies that state that screws are clinically stable but not absolutely stationary when loaded (Liou et al., 2004). Osseous contact with an implant as low as 5% has been shown to resist orthodon- 160 Cornelis et al. tic loads (Deguchi et al., 2003). Ohmae and colleagues (2001) suggest that an integration index of 25% is a reliable anchorage tool. Lower values of Osseointegration generally were obtained with miniscrews compared to conventional implants (Table 2: 3, 5, 6, 8). Obviously complete os- Seointegration is undesirable for a temporary anchor device, and it seems clear that screws can serve as anchorage even with a very low integration index. As long as mechanical stability is obtained, osseointegration prob- ably is not necessary at all, but when titanium is used, a certain percentage of bone-implant contact occurs, even if achieving osseointegration is not a goal in itself. Remodeling was greater around loaded screws than unloaded screws (Melsen and Lang, 2001; Ohmae et al., 2001). High bone remod- eling with intense formation of woven bone around the screws was ob- served three weeks after placement, whereas predominant lamellar bone was found after six or 12 weeks (Deguchi et al., 2003). However, quan- titative studies could not determine any significant effect of orthodontic loading on bone-screw contact (Table 2: 2, 3, 6, 8, 9), even though removal torque values were reported to be higher in nonloaded implants compared to loaded ones (Morais et al., 2007). The type of stress applied, whether compression or tension, was not associated with differences in bone re- sponse (Melsen and Costa, 2000; Melsen and Lang, 2001). The degree of Osseointegration increased as the period during which the miniscrews were loaded increased (Buchter et al., 2006; Melsen and Costa, 2000). Miniplates. Direct bone-to-metal contact was reported around ti- tanium bone screws supporting osteosynthesis miniplates used for man- dibular fracture treatment (Cheung et al., 1995; Hwang et al., 2000; Hirai et al., 2001). Only two teams studied bone healing around orthodontically loaded miniplates in experimental conditions. One group described bone- to-metal contact around the screws supporting the miniplate system and claimed that it increased under loading (Daimaruya et al., 2001). This has not been assessed quantitatively however. The other group found no significant differences in bone-implant contact between the screws of the loaded plates and the screws of the nonloaded ones (Cornelis et al., in press, b). In this study, bone-implant contact of screws associated with a stable plate ranged from 1% to 77%. However, plate stability with a screw having a bone-to-metal contact as low as 1% could result from a high per- centage of bone-to-metal contact around the other fixation screw or to the presence of bone in contact with the miniplate itself. 161 TSAD Experimental Literature They also reported that bone-implant contact increased with time, not only with the screw but with the plates as well (Cornelis et al., in press b). This might argue in favor of removing the plates as soon as they are no longer necessary, since osseointegration of the screws and plates could seriously impede plate removal. CONCLUSIONS Using titanium devices for skeletal anchorage has gained rapid ac- ceptance in orthodontic practice. The experimental literature, when sum- marized, provides some interesting insights into the application of TSADS and to their management in clinical practice. While implant failure remains largely unexplained, factors such as healing time, magnitude of load, soft tissue inflammation and possibly screw-to-root contact may influence TSAD success rate. There is as yet lit- tle agreement as to what is the optimal loading needed to maintain stabili- ty. Immediate loading of miniscrews seems to be acceptable if the range of forces is low, although currently there is no evidence to support immediate loading of implants or miniplates. Further research is needed. Immediate loading requires fair primary stability, which depends on the thickness of the cortical bone, placement technique and screw design. All of the studies agreed on the clinical stability of TSADs under orthodontic loading and that some degree of bone-implant contact occurs. TSADs do, in general, resist orthodontic displacement forces, absolutely maintaining their initial position, even in the presence of levels of osseointegration as low as 10% for implants and 5% for miniscrews. Might there be other materials that are as biologically acceptable, but do not encourage osseointegration in the way titanium does? Some stainless steel screws are available on the market, but they have been tested only in vitro (Chin et al., 2007). Loading increases bone remodeling, but not bone-to-implant con- tact. Uncoated implants, miniscrews or miniplates are preferred due to their ability to avoid excessive osseointegration. 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Am J Orthod Dentofacial Orthop 1999a;116:678-686. Wehrbein H, Glatzmaier J, Yildirim M. Orthodontic anchorage capacity of short titanium screw implants in the maxilla. An experimental study in the dog. Clin Oral Implants Res 1997;8:131-141. Wehrbein H, Merz BR, Diedrich P, Glatzmaier J. The use of palatal im- plants for orthodontic anchorage. Design and clinical application of the orthosystem. Clin Oral Implants Res 1996;7:410-416. Wehrbein H, Yildirim M, Diedrich P. Osteodynamics around orthodonti- cally loaded short maxillary implants. An experimental pilot study. J Orofacial Orthop 1999b;60:409–415. Willems G, Carels CE, Naert IE, van Steenberghe D. Interdisciplinary treatment planning for orthodontic-prosthetic implant anchorage in a partially edentulous patient. Clin Oral Implants Res 1999; 10:331-337. 169 TSAD Experimental Literature Wilmes B, Rademacher C, Olthoff G, Drescher D. Parameters affecting primary stability of orthodontic mini-implants. J Orofacial Orthop 2006;67:162-174. Yano S, Motoyoshi M., Uemura M, Ono A, Shimizu N. Tapered ortho- dontic miniscrews induce bone-screw cohesion following immediate loading. Eur J Orthod 2006:28:541-546. 170 REVIEW AND IMPLICATIONS OF TRANSLATIONAL RESEARCH TO TADS Sarandeep Huja Janice Struckhoff Jahnavi Rao The purpose of this chapter is to review the current state of knowledge of the biomechanics and biologic adaptation of temporary anchorage devices (TADs). These devices rapidly are becoming a part of routine orthodon- tic practice and have great potential for enhancing orthodontic anchorage. Their application has been heralded as a paradigm shift, but their future potential remains incompletely explored. We begin by comparing TAD adaptation to endosseous implant adaptation. We then go further to high- light and discuss features and clinical issues unique to these devices. GENERAL ADAPTATION VS. LOCAL ADAPTATION It is important to distinguish between general and local adaptive response (Huja and Roberts, 2004). A generalized adaptive response pro- duces adaptation in the whole bone and not just at a specific focal point. For example, the loading of a long limb such as the femur results in an adaptive response in the entire limb (Robling et al., 2001). A local adap- tive response affects only the bone in the immediate area such as the adap- tive response seen in bone supporting an endosseous implant. - Bone adaptive events surrounding endosseous implants occur mostly within 3 mm of the implant interface. This phenomenon has been demonstrated repeatedly (Roberts et al., 1986; Roberts, 1988; Chen et al., 1994; Huja et al., 1998). This distinction is important, as it means that the biology at the interface should be the focus for studying and understanding the new TAD technology. While the host site may differ between individu- als and species, there is evidence to suggest that “elevated remodeling is a universal mechanism necessary for long-term retention of rigidly inte- grated implants” (Garetto et al., 1995). The vast amount of information available on endosseous implant adaptation will translate easily to TAD technology. After all, the major differences between TADs and endosseous implants are the smaller size of TADs and the lack of surface preparation necessary for TADs. 171 Translational Research TYPICAL ADAPTIVE EVENTS IN BONE SURROUNDING ENDOSSEOUS IMPLANTS The short-term adaptive events following insertion of an endosse- ous implant are: a) formation of a callus on the periosteal and/or endosteal surface; b) revitalization through remodeling of a necrotic or dam- aged bone at the interface; and c) development of load bearing bone. It is important to understand these well described events (Rob- erts, 1984; Roberts et al., 1986; Garetto et al., 1995). The use of TADs is relatively short term (months rather than years). It is important, therefore, that the clinician have an understanding of the microdamage physiology (Huja, 2005b) associated with implant insertion, i.e., the damage that is created during insertion of any screw-type device into bone. The damage is repaired by bone remodeling, and the role of targeted damage in bone healing is well documented in the orthopedic literature (Burr, 1993; Mori and Burr, 1993). In addition, it is likely that damage physiology is impor- tant in understanding tooth movement and root resorption (Hartsfield et al., 2004; Roberts and Hartsfield, 2004). ADAPTATION PHYSIOLOGY AND BIOMECHANICS OF BONE-SUPPORTED TADS The primary differences between endosseous implants and TADs are that TADs typically are not subject to surface preparations and they are smaller than endosseous implants. In addition, TADs are placed in the monocortical plate of the alveolar process. Given that the alveolar process can be very thin (1 to 2 mm), one must ask if the bone adaptation response around TADs is similar to that of endosseous implants. Quantification of osseointegration is not well defined and methods vary. Although TADs are biocompatible and there is a level of integration between these devices and bone, it is overcome easily during their removal from the supporting bone. Whether these devices should have higher levels of removal torque to resist certain types of direct anchorage applications (e.g., wire directly into the head of the TAD to upright a tooth) remains to be answered. The obvious disadvantage of higher removal torque is the possibility of the screw head fracturing during removal. 172 Huja et al. In our research, we asked two basic questions for which there is no information available in the literature: 1. Does the bone provide sufficient holding power for orthodontic force application to the TADs? 2. Is the short-term bone adaptation response to insertion of TADs similar to that of endosseous implants? Biomechanical Performance Using a canine model, the study design consisted of two time points: T, represented day of insertion and T. represented six weeks post insertion (Huja et al., 2005; Huja et al., 2006b). Fourteen Synthes self- drilling screws (2 mm in diameter and 6 or 8 mm in length) were placed in the anterior, middle and posterior regions of the maxilla and mandible of each animal (Figs. 1 and 2). In addition, one screw was placed in the palate. After the test period, bone block specimens containing the screws were obtained from the sites and prepared for mechanical testing. The de- tails of this protocol have been published elsewhere (Huja et al., 2005). The screws essentially were extracted from the supporting bone in an axial pull-out test (Standard Specification and Test Methods for Metallic Medi- cal Bone Screws, 2002). The peak force from the load/displacement curve was recorded and represented as the holding power of the screw (Fig. 3). The mean hold- ing power of these screws ranged from 160 to 380 N (Fig. 4). There were no clinically significant differences between the two time points. Thus, the six-week adaptation period did not increase or decrease the biomechanical performance of these screws. Even though the two time points involved two different sets of dogs, the data suggest that the holding powers were similar. Clinically, the load to these devices is applied in cantilever bend- ing. However, it is not possible to conduct standardized tests in cantilever bending. For example, a tooth root may interfere with such a load applica- tion. The bone thickness at the screw extraction site was recorded at To by visual microscopic measurement (not an exact histological meth- od), and the mean bone thickness at various sites ranged from 1.2 to 2.4 mm (Fig. 5). This thickness of bone affords a very high holding pow- er. These data must be interpreted in light of the fact that orthodontic forces necessary for movement of a single tooth may only be 2 N and even en masse retraction forces rarely exceed 6 to 10 N per side. A re- cent study of 10 patients quantified monocortical bone thickness in the posterior regions of the maxilla and mandible from CT images (Deguchi 173 Translational Research Figure 1. Photographs depicting various screw sites six weeks post placement in the canine jaws. Top: anterior (a), mid (b). and posterior (c) sites in the maxilla. Bottom: posterior (a) and mid site (b) in the mandible. Figure 2. Radiograph of the canine mandible depicting the location of the three screws. P4 was missing in this particular dog. 174 Huja et al. Tooth Pull-out -- JSO1 180 160 140 120 100 80 60 40 20 : O 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 Displacement (mm) Figure 3. Graph of the peak load-to-failure at six weeks post-insertion. All measurements are in Newtons. Peak load failure represents the max- imum holding power of the screw. 500- | - T | | Today 6 wº 400 O MD POST MD MID MX POST MX MID MX ANT PAL MD ANT Region Figure 4. Peak pull-out strength (Mean ESEM) at T, and T. at various locations In the canine jaw. All measurements are in Newtons. No significant differences Were found between T, and T. at any of the locations. 175 Translational Research || 0 Day swee, 1 5- 0. 5– 0– MDPOST MDMID MXMID MXPOST PAL MXANT MD ANT Location Figure 5. Mean bone thickness (Mean ESEM) at T, and T. All measure- ments are in mm. No significant differences were found between T, and T. at any of the locations. et al., 2006). Bone thickness of 1.3 to 1.8 mm was recorded in the maxilla and 1.8 to 2.0 mm in the mandible. These are very similar to the thickness- es recorded in our animal study. Given the study design and limitations, direct extrapolation of results is not possible. However, the animal and human study data collectively confirm clinical case reports and suggest that adequate holding power for application of orthodontic loads can be provided by current TAD technology. Histological Analyses A total of 23 screws were obtained from 7 adult dogs at 6 weeks post insertion and examined using static and dynamic histomorphometric methods. Details of this study and sample are published elsewhere (Huja et al., 2006b). Bone Contact. Bone contact was higher in the mandible than in the maxilla, with mean contact varying anywhere from 84% to 94%. In failed specimens that also were examined, minimal contact was seen be: 176 Huja et al. tween the screws and the bone (Fig. 6). These screws were mobile or re- tained by soft tissue. What is apparent in the image of the failed screw is a lack of adequate bone volume to support the screw due to the proximity of anatomical structures. This observation is in agreement with anecdotal evidence that screws placed close to roots have a high chance of failure. º N. . Figure 6. Epifluorescent micrograph (40x) of a failed screw-supporting bone in the maxillary palatal region. Note the lack of adequate bone con- tact and the presence of fibrous tissue at the bone screw interface. Porosity of Cortical Plates. TADs are placed typically in the buc- cal cortical plate of the alveolar process. We found that these plates had only 10% to 22% porosity (Fig. 7). The porosity was determined by cal- culating the bone volume/total volume. Again, there was little difference in porosity between different locations. This finding is in contrast to the typical bone types (I-IV) for the jaws that are described in the prosthodon- tic literature (Brănemark, 1986). The bone types cited in the prosthodontic literature refer to the thickness of the cortical plate and porosity within the jaws. This is different from the location where most TADs are placed, i.e., the monocortical plate. It is unlikely that the trabecular bone provides sup- port for the success of the TAD. 177 Translational Research 100 : E c º -- º % = § 3. : . a. × s s s -> s s DL Figure 7. Porosity of cortical plates (Mean E SEM) at T. All measurements are in percents. The average porosity for all sites ranges from 10% to 22%. No significant differences were found between the maxilla and the mandible or between different loca- tions within each jaw. Formation of Callus in Response to TAD Insertion and Healing. The stages of healing subsequent to endosseous implant insertion have been well described in the literature (Roberts, 1988). We found that the periosteal callus in the maxilla was thicker (~ 250 um) than in the man- dible (~50 um). In addition, the mean thickness of the maxillary cortical plate was 0.5 mm thinner than the mandibular cortical plate (Fig. 8). Thus it seems that a thinner plate results in a larger periosteal response, prob- ably due to the bone stabilizing the TAD. The effect of load application on this callus is unknown for TADS. Bone Formation Rate (BFR) or Bone Turnover. The pattern of bone turnover adjacent to the screws was comparable to that reported in the literature for endosseous implants (Garetto et al., 1995). First, there is more turnover or bone activity in the bone (Figs. 9-10) close to the inter- face than in the bone further away. Second, the mean BFR in the femur of these dogs was 1.67% per year. The rate of turnover in the bone Sup- porting the screws clearly was higher than the baseline turnover rate in 178 Huja et al. the femur. However, these results should be viewed with caution, as the turnover rate in the jaws of dogs is 6 to 10 times greater than in the fe- Iſlur. Figure 8. Epifluorescent micrograph of the screw-supporting bone in the maxillary (100x) and mandibular (40x) region. Note the abundant periosteal response in the maxilla vs. the man- dible. Significant differences in the periosteal thickness were found between maxilla and mandible at T. (p = 0.03). There was a threefold increase in the periosteal thickness of the max- illa compared to that of the mandible. 179 Translational Research 1000 ſm Figure 9. Epifluorescent micrographs (100x and 40x) of the screw Sup- porting bone in the mandibular region. Note the abundant osteonal re- modeling in the vicinity of the screw surface. Significant differences (p = 0.01) in the bone formation rate (BFR, 9%/yr) were found between near (< 1 mm) and far (> 1 mm) locations at 6-week post insertion. BFR in the near bone was threefold greater than in the far bone. 180 Huja et al. Comparison to the Histomorphometric Data of Deguchi and Colleagues One recent study used methods very similar to our methods (De- guchi et al., 2003). Therefore, we can compare the results of the Deguchi study to those of our study. The primary differences between the two stud- ies were: 1) The Deguchi study used self-tapping screws with pilot hole preparation prior to screw insertion rather than TADs. 2) Their dogs were approximately 9 months old, whereas the dogs in our study were adults. 3) The Deguchi study was much more extensive than ours, with multiple time points and healing control and force application groups. Our results can be compared to those of the Deguchi six-week healing control group. Overall, the pattern of bone formation events ob- served in the two studies was very similar. However, the BFR was nearly tenfold higher in the Deguchi study than in ours. It is difficult to account for this difference based solely on the age of the dogs and screw design. However, it is clear that bone formation events in the immediate vicinity of the screws are readily apparent and may play a role in the retention of the devices in the jaws. Bone Turnover in the Jaws. There is limited information on in- tracortical bone turnover in the alveolar process (Marotti and De Lena, 1966; Tricker et al., 2002; Huja et al., 2006a). Bone turnover is involved in tooth movement, distraction osteogenesis and in any new application such as TADs being placed in jaws. In addition, bisphosphonates have the potential to interfere with bone resorption and bone turnover. The mecha- nism for this elevated bone turnover in jaws is not understood. Also, bone turnover in the skeleton decreases with age, although the relative amounts of turnover still remain high in the jaws of aged animals (Dixon et al., 1997). Finally, high doses of etidronate, an early non-nitrogen containing bisphosphonate, can abolish bone turnover in the jaws as well (Handick, 2001). The consequences of a lack of bone turnover on tooth movements are unclear, but they need urgent investigation. BISPHOSPHONATES AND OSTEONECROSIS OF THE JAWS (ONJ) ONJ is an undesirable sequala of oral and IV bisphosphonate therarapy. Bisphosphonates have been used for more than 30 years for a variety of medical problems and are considered one of the standards 181 Translational Research of care in cancer patients for supportive therapy. ONJ lesions are painful and debilitating. The prevalence of ONJ is estimated to be 4% to 10% and is especially high in patients receiving IV doses (e.g., zoledronic acid, a potent bisphosphonate). We have limited evidence to offer our adult patients regarding oral bisphosphonates. No study has evaluated the likelihood of complica- tions that could result in failure of TADs or, more seriously, the onset of ONJ in patients receiving bisphosphonates. One case report documents the failure of successfully integrated endosseous implants in a post meno- pausal woman that failed after diphosphonate treatment (Starck and Epker, 1995). However, Jeffcoat (2006) reported in a controlled clinical study that there were no adverse effects from oral bisphosphonates on the outcome of endosseous implants. Unlike endosseous implants, however, TADs are removed after a period of use creating an oral wound in direct communica- tion with the oral cavity. While TAD sites typically heal uneventfully fol- lowing the removal of the device, little is known about the healing process after TAD removal in patients who have or are susceptible to ONJ. PERIOD PRIOR TO LOADING It may be advantageous to load the TAD on the day of insertion. However, progressive loading over the first two weeks is recommended by some clinicians (Ohashi et al., 2006). In that TADs do not osseointegrate, the waiting period is a time not for osseointegration, but for healing. Based on the healing events described earlier in this chapter, it probably is best to wait one week to allow the periosteal callus to form prior to loading. However, a specific study designed to address this issue is needed. The level of primary stability (Huja, 2005a) may be a better indicator of the appropriate time to load a TAD than are other factors. Insertion and Removal Torque The amount of torque applied during insertion is primarily a re- flection of the density of the bone at the site of insertion and may provide an estimate of the primary stability. Removal torque for a machined screw without surface preparation is a measure of its ability to withstand tor- sional forces during the period of service of the device. If a device or an implant becomes osseointegrated, the amount of torque needed to remove the device is a measure of the strength at the interface. It is probably more important to understand both insertion and removal torque in the service of endosseous implants than the new designs of TADs. 182 Huja et al. Self-Tapping and Self-Drilling Screws Self-tapping TADs typically need the pre-insertion preparation of a pilot hole that is similar to the preparation needed for endosseous im- plants of sequential drill sizes. However, in the case of TADs, only one pilot hole is needed. Self-drilling screws typically have been used only in thin plates of bone (e.g., finger bones, neurosurgery applications) similar to the alveolar process. A self-drilling screw inserted into thick cortical bone (e.g., the femur) has the potential to fracture the bone. Differences exist in the thickness of the alveolar plates in the maxilla and mandible, but typically this difference, is not more than 0.5 mm. If a TAD is placed in thick bone (e.g., toward the external oblique ridge or in a torus), a pi- lot hole would be advisable. Without a pilot hole, the insertion torque is far greater than typically experienced during placement of these devices. Even in the alveolar process of the mandibular posterior region (e.g., be- tween the first and second molar), it is possible that a screw may fracture during insertion because the insertion torque might exceed the strength of the screw. Bone Stock for Placement Probably the most critical factor for the clinician to evaluate is bone availability and the relative location of its mucogingival junction to the site of insertion (Schnelle et al., 2004). Most TADs are placed at an angle with the tip of the TAD pointing away from the occlusal table. This allows for further apical placement as more interradicular space becomes available at this location. A 1.5 mm diameter screw probably should not be placed in less than 3 mm of bone. A certain bone volume must exist around the device, or it is likely to fail due to lack of bone support (Fig. 10). Accurate placement (e.g., less than 0.25 mm) is not possible even with stents. While more bone may be found at the apical areas of the root, this tissue is covered by movable mucosa (Lang and Loe, 1972). The decision then must be made whether to make a punch or small incision in the mov- able mucosa. While this may be a common procedure performed in some practices, it is typical in the United States to have a surgeon perform the procedures, as risk of tissue growth may have to be managed in the future. Most orthodontic practitioners currently are more comfortable placing these devices at the mucogingival junction. A schematic depicting typical width of attached gingiva in the posterior regions and sites with adequate bone stock for placement as estimated from a recent study by Poggio and colleagues (2006) illustrates that some sites with adequate bone are lo- cated beyond the attached gingiva (Fig. 10). 183 Translational Research Figure 10. Schematic of attached mucosa and relative location of bone stock as derived from the data of Poggio and colleagues. Note there are multiples sites where bone exists for safe screw placement that are not covered by attached mucosa. CONCLUSIONS Currently, the choice of a particular device (manufacturer) seems to be based on factors other than its biological adaptation capabilities. Clinical experience with a device also may outweigh other disadvantages. We do not have convincing evidence of the need for chlorhexidine mouth- wash before and after surgery or proper guidelines for the use of antibi- otics, the types of anesthesia or the use/need for stents. We do not fully understand the implications of perforation into the maxillary sinus. In the United States we do not know what training is provided to current gradu- ate students or to practicing orthodontists who would like to use these de- vices. While there is a variety of devices and modes of skeletal anchorage in vogue, we do not have clear clinical or experimental evidence to define the range of tooth movement with miniscrews versus that with miniplates. There is an urgent need to define the indications, risks and benefits of these devices and to establish guidelines for their use versus the use of tradi- tional anchorage preparations. REFERENCES Brănemark P-L. Introduction to osseointegration. In: Brănemark P-1, Zarb GA, Albrektsson T, eds, Tissue-Integrated Prostheses: Osseointegra- tion in Clinical Dentistry. Chicago, Quintessence Publishing Co. Inc. 1986: 11–76. Burr DB. Remodeling and the repair of fatigue damage. Calcif Tissue Int 1993:53:S75–S81. 184 Huja et al. Chen J, Lu X, Paydar N, Akay HU, Roberts WE. Mechanical simulation of the human mandible with and without an endosseous implant. Med Eng Phys 1994; 16:53-61. Deguchi T, Nasu M, Murakami K, Yabuuchi T, Kamioka H, Takano-Yama- moto T. Quantitative evaluation of cortical bone thickness with com- puted tomographic scanning for orthodontic implants. Am J Orthod Dentofacial Orthop 2006; 129:721 e7-12. Deguchi T, Takano-Yamamoto T, Kanomi R, Hartsfield JK Jr, Roberts WE, Garetto LP. The use of small titanium screws for orthodontic an- chorage. J Dent Res 2003;82:377-381. Dixon RB, Tricker ND, Garetto LP. Bone turnover in elderly canine man- dible and tibia. J Dent Res 1997;76:336. Garetto LP, Chen J, Parr JA, Roberts WE. Remodeling dynamics of bone supporting rigidly fixed titanium implants: A histomorphometric com- parison in four species including humans. Implant Dent 1995; 4:235- 243. Handick KE. The effect of etidronate on alveolar bone remodeling in dog mandible. Indianapolis: Unpublished Master’s Thesis, Indiana Uni- versity School of Dentistry, 2001. Hartsfield JK Jr, Everett ET, Al-Qawasmi RA. Genetic factors in external apical root resorption and orthodontic treatment. Crit Rev Oral Biol Med 2004; 15:115-122. Huja SS. Biologic parameter that determine success of screws used in orthodontics to supplement anchorage. In: McNamara JA Jr, ed, Implants, Microimplants, Onplants and Transplants; New Answers to Old Questions in Orthodontics. Craniofacial Growth Series. The Department of Orthodontics and Pediatric Dentistry and Center for Human Growth and Development, The University of Michigan, Ann Arbor 2005a:42:177-188. Huja SS. Biological mechanisms of bone adaptation to orthodontic an- chors. In: Cope JB ed, Temporary Anchorage Devices in Orthodon- tics. Dallas, Under Dog Media, 2005b. Huja SS, Fernandez SA, Hill KJ, Li Y. Remodeling dynamics in the al- veolar process in skeletally mature dogs. Anat Rec A Discov Mol Cell Evol Biol 2006a;288: 1243–1249. Huja SS, Katona TR, Moore BK, Roberts WE. Microhardness and anisot- ropy of the vital osseous interface and endosseous implant supporting bone. J Orthop Res 1998;16:54-60. Huja SS, Litsky AS, Beck FM, Johnson KA, Larsen PE. Pull-out strength of monocortical screws placed in the maxillae and mandibles of dogs. 185 Translational Research Am J Orthod Dentofacial Orthop 2005;127:307-313. Huja SS, Rao J, Struckhoff JA, Beck FM, Litsky AS. Biomechanical and histomorphometric analyses of monocortical screws at placement and 6 weeks postinsertion. J Oral Implantol 2006b;32:110-116. Huja SS, Roberts WE. Mechanism of osseointegration: Characterization of supporting bone with indentation testing and backscattered imag- ing. Semin Orthod 2004; 10:162-173. Jeffcoat MK. Safety of oral bisphosphonates: Controlled studies on alveo- lar bone. Int J Oral Maxillofac Implants 2006:21:349-53. Lang NP, Loe H. The relationship between the width of keratinized gin- giva and gingival health. J Periodontol 1972:43:623-627. Marotti G, De Lena M. Quantitative analysis of the structural reconstruc- tion process in the dog mandible in relation to age. Arch Ital Anat Embriol 1966;71:229-252. Mori S, Burr DB. Increased intracortical remodeling following fatigue damage. Bone 1993; 14:103-109. Ohashi E, Pecho OE, Moron M, Lagravere MO. Implant vs. screw loading protocols in orthodontics. Angle Orthod 2006;76:721-727. Poggio PM, Incorvati C, Velo S, Carano A. “Safe zones:” A guide for miniscrew positioning in the maxillary and mandibular arch. Angle Orthod 2006;76:191-197. Roberts EW, Poon LC, Smith RK. Interface histology of rigid endosseous implants. J Oral Implantol 1986; 12:406-416. Roberts WE. Rigid endosseous anchorage and tricalcium phosphate (tcp) coated implants. J Calif Dent Assoc 1984;12:158-161. Roberts WE. Bone tissue interface. J Dent Educ 1988:52:804-809. Roberts WE, Hartsfield Jr JK (2004). Bone development and function: genetic and environmental mechanisms. Semin Orthod 2004;10:100- 122. Robling AG, Burr DB, Turner CH. Skeletal loading in animals. J Muscu- loskel Neuron Interact 2001:1:249-262. Schnelle M, Huja SS, Beck FM, Jaynes R. A radiographic evaluation of the availability of bone for placement of miniscrews. Angle Orthod 2004;74:830-835. Standard Specification and Test Methods for Metallic Medical Bone Screws. West Conshohocken: ASTM International, 2002. Starck WJ, Epker BN. Failure of osseointegrated dental implants after di- phosphonate therapy for osteoporosis: A case report. Int J Oral Maxil- lofac Implants 1995;10:74–78. Tricker ND, Dixon RB, Garetto LP (2002). Cortical bone turnover and 186 Huja et al. mineral apposition in dentate bone mandible. In: Garetto LP, Turner CH, Duncan RL, Burr DB eds, Bridging the Gap Between Dental and Orthopaedic Implants. Indianapolis, School of Dentistry, Indiana Uni- versity 2002:226-227. 187 COMPLICATIONS ASSOCIATED WITH THE USE OF MICROIMPLANTS DURING ORTHODONTIC TREATMENT Shou-Hsin Kuang Using skeletal anchorage for orthodontic tooth movement is not a new idea. In the past, there have been many skeletal anchorage devices such as vitallium screws, zygomatic wires, endosseous implants, mini bone plates, on-plants, midpalatal implants, etc. Most of these devices require invasive procedures to implement, and they add considerably to the cost of treat- ment, all of which has prevented orthodontists from using them routinely. However, a new era has begun in orthodontic treatment with the advent of the mini-screw or microimplant (also called the mini-pin or temporary anchorage device [TAD]). Microimplants provide enough anchorage to Support diverse tooth movements; they have minimal anatomic limitations with regard to placement; they are less costly than previous skeletal an- chorage devices, both in terms of risk and cost of treatment to patients; and they require simpler and less traumatic surgery. Based on the many clinical cases reported in literature, there is no doubt about the efficiency and power of these tiny screws. They allow the orthodontist to treat many types of malocclusions effectively with little or no surgery that, in the past, required invasive procedures because of insuf- ficient anchorage. The microimplant has broadened the field of ortho- dontics such that treatment goals can be achieved with “orthognathic-like effect” (Fig. 1). Using microimplants for anchorage is not completely risk free, however. In this chapter, we will discuss the problems most likely to be encountered when using microimplants, i.e., root injury, microimplant fracture, soft-tissue irritation, loosening of microimplant screws, and me- chanical problems. We also will make some suggestions as to how to re- solve these problems. ROOT INJURY Even though microimplants can provide reliable anchorage for tooth movement, inserting a microimplant into the bone still is an inva- sive procedure. Orthodontists and oral surgeons must take care of the im- portant anatomic structures involved such as blood vessels, nerves and 189 Potential TAD Complications - A Figure 1. “Orthognathic-like” effect of treatment with microimplants. Top: Pre- treatment photographs. The patient had a bidentoalveolar protrusion with an extreme convex profile indicating the need for orthognathic surgery. Bottom: Post-treatment photographs. Four microimplants were placed in each quadrant for anchorage and four first premolars were extracted for maximum anterior teeth retraction. the maxillary sinus. The most severe complication associated with mi- croimplant placement is injury to the root caused when a microimplant is placed in a tooth bearing area (Figs. 2 and 3). How to Avoid Root Injury 1. Use advanced radiological images such as 3D cone-beam CT images in order to obtain a more accurate 3D interdental bone structure to help select proper implant site (Gracco et al., 2006; Kim et al., 2006). 2. Use the data calculated by panoramic X-rays or volumetric tomographic images to determine the greatest bone stock areas, so called “safe zones”, in which to place microimplants (Carano et al., 2004; Sch- nelle et al., 2004; Deguchi et al., 2006; Pottio et al., 2006; Liou et al., 2007). 190 Kuang Figure 2. A: Iatrogenic root injury to the mesial root of the mandibular right first molar. Neither patient nor orthodontist discovered the com- plication until a routine X-ray was taken several months after the injury occurred. B: Post-debonding panoramic film; the pulp test of the man- dibular right first molar still is positive. 3. Use surgical guides, surgical stents or templates combined With periapical X-rays to increase the accuracy of microimplant insertion (Melsen, 2005; Morea et al., 2005; Cousley and Parberry, 2006). 4. Avoid perpendicular insertion pathways in dental-bearing areas. Using an approximate 45° oblique, apical direction for insertion provides a wider interdental space and more bone stock and cortical bone Support for microimplants (Deguchi et al., 2006; Mizrahi and Mizrahi, 2007). 5. Select non-tooth-bearing areas like the infrazygomatic crest, mid-palatal suture or external oblique ridge, etc. 191 Potential TAD Complications Figure 3. Root apex trauma of the maxillary left central incisor caused during insertion of a palatal microimplant, a and b; Predrilling and insertion of the microimplant. c and d. The root apex had been perforated during predrilling. e: Apical X-ray taken after debonding. Note the short root length of the left maxillary incisors. (Photograph is courtesy of Dr. H.C. Cheng, Taipei Medical University). However, no matter what kind of modality we select, precise and accurate surgical technique is the basic requirement for avoiding damaging roots or periodontal structures when we insert a microimplant. Cone-beam CT image technology has been developed to replicate the dental model and construct a surgical guide. This new technology can help orthodontists place a microimplant precisely in the proper site (Kim et al., 2007). Anoth- er new advance in surgical technique being developed is “computerized navigation surgery” (Wexler et al., 2007) in which the surgical drill can be traced and animated in real time on radiology images of the surgical site. This potential technique can increase the accuracy and safety for surgeons and orthodontists when inserting a microimplant. Considering the cost and benefits of applying microimplants at the present time, perhaps the most important prerequisite is an accurate periapical X-ray taken with long cone technique (Figs. 4a and b) as we usually can check the bone dimension on a periapical X-ray. Most micro- implants have diameters between 1.2 mm and 2.0 mm. So, if we can find 192 Kuang a space that is 2 mm greater than the microimplant, we can perform the procedure safely. Sometimes, the bifurcation area of mandibular first mo- lars is a good choice for the implant site (Figs. 4c and d). I do not recom- mend using panoramic films as the reference for the implant site because panoramic films have greater magnification and distortion rates. More- over, if we intend to place microimplants in the interdental area, we first should consider: 1. Is there a possibility that microimplant will hit the teeth to be moved? For instance, if we plan to retract the entire dentition, it is unwise to place a microimplant between the roots of the molar and premolar. Mi- croimplants often need to be replaced during the retraction stage. 2. Will the movement of the microimplant under stress cause it to hit the adjacent roots? According to the study of Liou and colleagues (2004), microim- plants are not stationary; they may migrate 1 to 1.5 mm under pressure. Therefore, clinicians should allow a safety zone for clearance between the microimplant and the dental root. Figure 4. An accurate periapical X-ray is the basic requirement for implant site Selection. a-b; Three millimeters of space between adjacent roots can provide a 1.4 mm microimplant site. c-d: The area of bifurcation of the mandibular first molar can be a good place to insert microimplants. 193 Potential TAD Complications What Is the Root Damage Rate When the Microimplant Is Placed in the Dental Bearing Area? There are still no definite statistics available on the root damage rate when microimplants are used in orthodontic treatment. We can get some information from oral surgeons, however, who use the intermaxil- lary fixation screw to fix fractured jaw bones (Jones, 1999). • In a study of 55 patients who received 232 intermaxillary fixa- tion screws, Fabbroni and colleagues (2004) reported that the rate of minor tooth contact was 15.9%, major tooth contact was 11.2% and six teeth were devitalized by the screws. • In a study of 62 patients with fractured mandibles who received cortical bone screw for intermaxillary fixation, Roccia and co-workers (2005) reported that the rate of root damage was 11%. • In a five-year retrospective study of the long term outcome of teeth transfixed by osteosynthesis screws, Borah and colleagues (1996) reported that the incidence of root impingement was 3.4%. Mandibular teeth were more at risk than maxillary teeth by a ratio of 10:3. • Farr and co-workers (2002) reported that 13 roots were dam- aged by intermaxillary fixation screw in a study of 31 cases and that four screws appeared to have entered the pulp cavity. Farr suggested that use of intermaxillary screws should be restricted because of an unacceptably high rate of root damage. • In contrast, Coburn and colleagues (2002) reported that only two patients experienced root damage out of 122 patients who received bicortical bone screws for intermaxillary fixation of mandibular. Because the diameter of intermaxillary fixation screws usually is greater than 2 mm and because jawbone fracture is a more complicated condition than that with which orthodontic patients usually present, we are able to use smaller diameter microimplants and can choose appropriate implant sites. This should translate into a lower rate of root injury than those reported above. What Is the Prognosis If the Root Is Damaged By the Microimplant? In Roccia and colleagues’ report (2005), teeth damaged by corti- cal screws with a scratch of their root remained vital and were not abnor- mally mobile. In Borah and Ashmead's report (1996), none of the transfixed teeth developed periapical abscesses during the follow-up period. They concluded that impingement of roots does not have an adverse effect on the Survival rate of affected teeth. 194 Kuang According to Asscherickx and colleagues’ (2005) animal study, the damaged root surface was repaired by cementum and returned to its normal periodontal structure 12 weeks after removal of the miniscrew. The hole created by the miniscrew filled with normal bone tissue and periodon- tal tissue completely recovered 18 weeks after miniscrew removal. Even though the Asscherickx animal study generated optimistic results for microimplant usage in orthodontic patients, it does not mean that we can ignore the possible severe complications of root damage caused by microimplants. Key reported (2000) that the roots damaged by intermaxil- lary fixation screws generally heal with good bone regeneration, but if the pulp is traumatized, the tooth may become non-vital. Hommez and col- leagues (2006) also reported a patient who had a jawbone fracture whose treatment with fixation screws resulted in severe external root resorption. Sometimes, the periodontal tissue is damaged by microimplantation, and the damaged tooth is stimulated by further orthodontic forces that can lead to severe periodontal destruction and tooth loss (Fig. 5). Figure 5. Microimplant damage to the periodontal structure caused severe peri- Odontal destruction and result in loss of tooth, a Pretreatment panoramic X- ray showed periodontally healthy structure. b. Panoramic X-ray taken the day of microimplant insertion; note that the microimplant may be inserted into the periodontal space of the mandibular left second molar. The microimplant failed after four weeks. c. Panoramic film taken on the day of debonding; note severe periodontal destruction of the mandibular left second molar. 195 Potential TAD Complications MICROIMPLANT FRACTURE Microimplant fracture is a troublesome condition for the ortho- dontist who plans to use microimplants as anchorage in treatment. In the early stages of developing microimplant procedures, the treatment proto- col for microimplant placement was based on the principles of prosthetic dental implant treatment, and osseointegration became the golden rule for microimplant protocols as well. Therefore, the only material used for mi- croimplants was commercially pure titanium with no exceptions. How- ever, because commercially pure titanium is not strong enough and the diameter of microimplants is very small, there were many microimplants broken during the insertion or removal procedures (Fig. 6). After several years of experience with microimplants, orthodon- tists finally realized that the requirements for orthodontic anchorage are different from those of prosthetic dental implants. Almost all orthodontists Figure 6. Microimplant fracture. a. The mesially-inclined mandibular third molar was to be protracted and uprighted using microimplant anchorage. b. Post-insertion periapical X-ray, c. Fracture of the microimplant occurred im- mediately upon application of the initial loading force. d: The broken pieces of the microimplant after removal. 196 Kuang now agree that microimplants used for anchorage are temporary anchor- age devices (TADs). Osseointegration is unnecessary for microimplants and even may cause detrimental effects during microimplant removal. The healing period required for Osseointegration also is unnecessary. The anchorage provided by microimplants is based on the mechanical lock with the cortical bone, thus orthodontic force can apply immediately (Bu- chter et al., 2005; Lai et al., 2005; Ohashi et al., 2006; Freire et al., 2007). Because of the concept change, the material for microimplants also has changed. Most of the current microimplants are manufactured out of tita- nium alloys (Papadopoulos and Tarawneh, 2007). Titanium alloy has 2.5 times the strength of pure titanium. Some dental companies even choose to make microimplants out of medical stainless steel. These materials greatly decrease the incidence of microimplant fracture. How to Avoid Microimplant Fracture 1. Check bone density on the X-ray and feel the hardness of bone by probe Sounding. This can provide some preliminary information on bone quality. 2. Use more advanced radiological techniques such as quantita- tive computed tomography (QCT) or quantitative cone-beam computed tomography (QCBCT) to evaluate bone density (Aranyarachkul et al., 2005; Lee et al., 2007). 3. In general, the cortical plate of mandible is thicker and bone density is greater than that of the maxilla. Therefore, orthodontists must be cautious when placing microimplants in the mandible. 4. Be clear about what material the implant(s) should be made of and the type of microimplant insertion system to be used, and follow the manufacturer’s instructions for placing microimplants. 5. If predrilling is required, the predrilling depth should be equal to the length of the microimplant to be inserted. 6. Regardless of what kind of material is used for the microim- plant, using the self-drilling technique is not recommended for use with microimplants less than 1.5 mm in diameter. 7. Avoid excess torque force when inserting a microimplant with a Screwdriver. We highly recommend using a driver with a torque gauge to control the application of torque force. 8. If the resistance is too strong to insert a microimplant into the depth that was planned, remove the microimplant and perform the pre- drilling procedure again to widen the implant site. 197 Potential TAD Complications Management of the Fractured Microimplant Microimplants can fracture during insertion or removal. Most of the time microimplants fracture at the level of the cortical bone surface. It is difficult to remove the fractured part of the microimplant that is in the bone. If the fractured part of the microimplant does not impact the follow- ing tooth movement, it can be left in place and followed long term. If it must be removed, however, the orthodontist can try to use a thin fissure bur to remove the coronal portion of the bone and expose 2 mm infrabony portion of the microimplant and use needle holders or Weingart pliers to rotate and pull it out slowly (Fig. 6d). If this technique does not work, an oral surgeon can try to remove the fractured microimplant with a trephine instrument. Supra-Structure and Strength of Microimplants For convenience and versatility, the modern microimplants used in orthodontic treatment have many different designs of the head portion Such as the neck, a round or rectangular hole, edgewise slot or composite Supra-structures. The hole or slot provides an attachment site for power chains, coil springs or rectangular wires for 3D tooth movement control. But these designs also create a weak point or the site at which the micro- implant breaks because of its small diameter at that point (Fig. 7). The manufacturer should consider the structural strength when designing the Supra-structure of microimplants. Orthodontists also should pay attention to this problem when inserting a microimplant. Figure 7. Broken supra-structure of the microimplant. a. A microimplant had been inserted successfully, but the supra-structure was distorted. b. The implant broke immediately upon the application of force. c. The narrow neck and a too- large hole in the shank weakened the structure of microimplant. 198 Kuang SOFT TISSUE IRRITATION The Boundary of the Implant Site – Mucogingival Junction The mucogingival junction is a very important anatomic structure with respect to the implant site, and this is especially true on the buccal site of the alveolar process. The soft tissue coronal to the mucogingival junc- tion is keratinized attached gingiva and immobile connective tissue. The tissue gingival to the mucogingival junction is non-keratinized mucosa and mobile, elastic tissue. If the implant site is beyond the mucogingi- Val junction, chronic inflammation around the microimplant will occur. This response is a result of the persistent rubbing of the mobile soft tis- Sue against the microimplant. Mild inflammation around the microimplant causes pain and swelling and results in granulation tissue surrounding the microimplant (Fig. 8). More serious inflammation will cause hyperplasia of the gingival tissue, and the overgrowth tissue may cover the supra- Structure of microimplant. This tissue hypertrophy will make the microim- plant difficult for the orthodontist to use (Fig. 9). In some extreme cases, acute peri-implant abscess or facial cellulites can occur (Fig. 10). Soft tissue inflammation is a definite risk factor for the stability of microimplants and has been reported as such in many studies (Miyawaki et al., 2003; Cheng et al., 2004; Park et al., 2006; Kravitz and Kusnoto, 2007). It is an important microimplant anchorage issue, and we must pay attention to it. Figure 8. Mild inflammation can be seen around the microimplant. Note that the microimplant is inserted beyond the mucogingival junction. 199 Potential TAD Complications wº - Figure 9. Severe soft tissue inflammation and hyperplasia caused embedding of the microimplant. Figure 10. Severe soft tissue inflammation caused peri-implant abscesses and the overgrowth granulation tissue could embed the microimplant and retraction spring. In some cases, the microimplant must be placed beyond the muco- gingival junction. If this occurs, the microimplant should have a broad soft tissue platform or a healing cap, and the patient should be instructed to clean around the microimplant thoroughly. The patient should use chlorhexidine solution as a mouthwash or cotton pellets dipped in a chlorhexidine solu- tion to clean around the microimplant. It will minimize the occurrence of inflammation and gingival tissue hyperplasia. 200 Kuang The “closed method” is another solution for microimplant place- ment beyond the mucogingival junction. This means that the microimplant is embedded beneath the soft tissue and a ligature wire is attached to the microimplant and extended out of the soft tissue. The wire extension in the oral cavity then is used for direct or indirect anchorage control. Use of the “close method” also can decrease the incidence of soft tissue inflammation effectively. Soft Tissue Damaged by the Supra-Structure of the Microimplant The portion of the microimplant that is exposed in the oral cavity is a source of irritation to the oral mucosa. Only the supra-structure should extend into oral cavity; the neck portion and thread of the screw must be embedded in the mucosa. The design of the supra-structure should include the proper size and the surface should be smooth to decrease the irritation of oral mucosa. The discomfort caused by the irritation of the oral mucosa by the Supra-structure, just like the initial period of orthodontic treatment, can be minimized by using beading wax and oral paste. In the few cases in which the mucosa irritation persists, composite resin can be used on the supra- Structure to decrease the irritation to the adjacent mucosa. Soft Tissue Damaged by the Acting Force In most cases, the microimplant insertion site is near the apical portion of alveolar process around the first molar area. When using direct anchorage with elastic chains or close coil springs for anterior teeth retrac- tion or intrusion, it is difficult to avoid damaging the mucosa of the curved alveolar process with straight line force (Figs. 11 and 12). Figure 11. When using a microimplant as direct anchorage in the molar area to retract anterior teeth, the retraction spring usually will impinge On the alveolar mucosa around the canine and first premolar areas. 201 Potential TAD Complications - Figure 12. a. A microimplant inserted between the lower sec- ond premolar and first molar for anchorage to retract and erupt the impacted canine. b. The soft tissue is severely damaged due to the direct impingement of the retraction elastics. To avoid the soft tissue trauma due to direct acting forces: 1. Add a protective plastic shield to the closed-coil spring or elastic thread (Figs. 13a and b). 2. Use a guiding pin or power arm to keep the elastic thread or closed-coil spring away from the gingival tissue and avoid soft tissue dam- age (Figs. 13c and d). 3. Change the force application method by changing the force application point or by using indirect instead of direct anchorage. 202 Figure 13. Using a plastic protection shield (a and b) or a power arm (c and d) helps avoid soft tissue impingement. - - - Figure 14. a-b; To intrude over-erupted maxillary first molars on both sides, two microimplants were inserted to apply intrusive force. c-d: Because the intrusion forces are on the buccal side of the molars, it will cause molar buccal flaring. A transpalatal arch should be used to prevent this side effect from occurring. 203 Potential TAD Complications Indirect Soft Tissue Damage Due to Moving a Tooth or an Appliance When using bilateral buccal microimplants for the purpose of mo- lar intrusion (Fig. 14), it is advisable to place a transpalatal arch to connect bilateral molars to avoid the side effect of buccal tipping. If we do not re- member that the transpalatal arch will move with the teeth, when intrusion occurs, the transpalatal arch can impinge on the tissue of the hard palate (Fig. 15). Therefore, a safe amount of clearance should be maintained be- tween the transpalatal arch and the hard palate when intruding molars. Figure 15. a. Pretreatment transpalatal arch used for controlling the molar axis during intrusion. b. Post-treatment first molar on both sides had been intruded by microimplant successfully but soft tissue impingement by the transpalatal arch occurred. c. Close-up view of right intruded molar. MICROIMPLANT LOOSENING There are many articles published that discuss the stability and success rate of microimplants and the reasons that screws become loose (Miyawaki et al., 2003; Cheng et al., 2004; Park et al., 2006; Kravitz and Kusnoto, 2007; Kuroda et al., 2007a). In my opinion, it is not easy to differentiate the actual reason(s) for a specific microimplant loosening: 204 Kuang we can assume that the cause is multifactorial. Even though it seems that no serious complications result from a loosened microimplant, it possibly might be troublesome to both orthodontists and patients. The factors that affect the stability of microimplants can be divided into host factors and Surgical factors Host Factors Bone Quality. Bone quality is the most important host factor. Usually it determines the success of a microimplant (Kravitz and Kusnoto, 2007). According to Misch's classification of bone density (1990), D3 and D4 bone types are not dense enough and cortical bone is too thin. D3-type bone density is relatively contraindicated and D4-type bone density is ab- solutely contraindicated for microimplant insertion. Pneumatic Bone Structure. The most likely sites for microimplant insertion are the buccal areas between the maxillary second premolars and second molars. However, the bone support could be inadequate in these areas for patients who have a low maxillary sinus floor. Allergy to Metal. The incidence of allergy to metal is not high, but it still cannot be ruled out completely; there are patients who have an allergic reaction to specific metal components in microimplants. Functional Problems. Types of food, a patient’s chewing pattern, and specific lip and tongue habits can cause abnormal force to be applied to microimplants, all of which can affect their stability. Oral Hygiene. It is very important to maintain good oral hygiene around the microimplant. Inadequate oral hygiene will cause inflammation around the microimplant, which can lead to destruction of the supporting tissue and loosening of the microimplant. Skeletal Morphology. It has been reported that patients who have a steep mandibular plane angle will have a higher microimplant failure rate (Miyawaki et al., 2003; Papadopoulos and Tarawneh, 2007). The pos- sible reason for this may be that these patients also usually have thin corti- cal bone. Surgical Factors Lack of Initial Stability. When inserting a microimplant into the bone, using either of the predrilling or self-drilling methods, the screw- driver and the microimplant should be keep in a straight line. The cli- nician must be careful not to jiggle the screwdriver during the insertion 205 Potential TAD Complications procedure so as not to inhibit the mechanical lock between the cortical bone and the microimplant. Insertion on Unattached Gingiva. The risk of the screw loosening increases if it is inserted beyond the mucogingival junction because the loose and mobile soft tissue has a greater risk of becoming irritated and good oral hygiene is difficult to maintain. Overloading. The application of force to a microimplant should be less than 300 gm or the surrounding tissue may not be able to support the loading, which will cause microimplant failure. . Over-Torquing During Insertion. Too much implant placement torque (IPT) will cause local ischemia and necrosis of bone, which can lead to microimplant failure. Motoyoshi and co-workers (2006) suggest that the optimal IPT for a 1.6 mm diameter microimplant should be 5 to 10 Ncm. Overheating. It is necessary to provide the appropriate amount of cooling during the process of predrilling or insertion of the microimplant to prevent overheating the implant site; overheating can lead to necrosis of the supporting bone. Root Contact. Microimplant contact with the root increases the rate of microimplant failure (Kuroda et al., 2007b) because the orthodon- tic force and physiologic tooth movement will persist hitting on the micro- implant and cause screw failure. There are two types of microimplant loosening: immediate and de- layed. Immediate loosening, defined as the microimplant becoming loose within one month of insertion, is the result of a lack of initial stability. If stability is not achieved immediately upon insertion, it will not become stable in the future. The microimplant in question should be removed im- mediately and reinserted. If the instability is due to a lack of mechanical lock with cortical bone, a wider microimplant can be reinserted in the same implant site. If the instability is caused by poor bone density, how- ever, it is best to find another implant site. Delayed loosing usually occurs after three months of microim- plant insertion. This type of failure is related to poor oral hygiene, inflam- mation around the microimplant and overloading of orthodontic force. 206 Kuang MICROIMPLANT MECHANICAL PROBLEMS The design of the microimplant has improved a great deal since its inception. It used to offer only one point of support for a single direction of force. Now, however, microimplant anchorage enables three-dimensional control of tooth movement. Although the advancements in microimplant design and use are significant, there still are limitations in the design of the supra-structure as a result of the small diameter of the microimplant. These limitations include the following: • The supra-structure Öf microimplant should not be placed at the same level of the dental arch; it is almost impossible to connect with other teeth in a straight line. • The microimplant usually is apical to the dental arch line. This makes the microimplant inherently intrusive. • The microimplant usually is close and adjacent to the soft tissue of the vestibule. This limits the space available for attaching complicated orthodontic apparatus. • Microimplants cannot withstand excessive loading forces. • Microimplants cannot resist any torque that is applied in the op- posite direction of the insertion pathway. Because of these limitations, microimplants still should be used most of ten as a point attachment to support orthodontic force and as anchorage to control tooth movement. Orthodontists often encounter the following problems when using microimplants as anchorage. . Microimplants Always Produce Intrusive Force Because microimplants almost always are placed on the gingival side of the line of the dental arch, any orthodontic apparatus that uses microimplants for anchorage will exert intrusive force in the system. Usu- ally, the teeth near the microimplants receive more intrusive effect than other teeth. Intrusion of the teeth is beneficial to patients who have long faces and high mandibular plane angles. In the past it was impossible for orthodontists to intrude molars, but now they can do it easily with micro- implants. Remember that microimplants are inherently intrusive. For patients who do not need molar intrusion, however, it be- comes a negative side effect of microimplant anchorage. For example, when using microimplants as anchorage and sliding mechanics for ante- rior teeth retraction by means of a continuous archwire, first molars were 207 Potential TAD Complications Figure 16. a-b; Microimplants and sliding mechanics are used to retract the anterior teeth. c-d: After space closure, all of the molars have been intruded causing a posterior openbite (red box). e. Close-up view of the area outlined by the red box seen in d. Note that the unwanted intrusive force not only intruded the molars; it also caused them to tip buccally. intruded after several months whether microimplant anchorage was direct or indirect (Figs. 16a-d). If the second molars are not bonded and con- nected to the archwire, the step between first and second molars will be obvious. Since the force from the microimplant usually is applied at the buccal and gingival side of teeth, intrusion always is accompanied by a buccal tipping movement (Fig. 16e). 208 Kuang In another example (Fig. 17), the maxillary left second molar must be extracted due to a poor prognosis, and the over-erupted third molar in- truded and protracted to replace the second molar. The microimplant was placed between the second premolar and first molar on the buccal and lin- gual side to provide anchorage for protracting the third molar. Two months later, the third molar was protracted completely to close the space created by the extraction of the second molar; it was intruded at the same time. Microimplants Cannot Provide Extrusive Force Easily º It is difficult for microimplants to provide an extrusive force be- cause they always are positioned on the gingival side of the dental arch. However, in the case of a deeply impacted tooth, microimplants can be used for anchorage to force eruption of the tooth, because the impacted Figure 17. a. The maxillary right second molar is hopelessly compromised and must be extracted. The patient wished to protract the over-erupted third molar forward to take the place of the extracted second molar b: The second molar was extracted and two microimplants were inserted. c. The microim- plants, placed between the second premolar and the first molar on the buccal and lingual side, began to protract third molar forward by means of closed-coil Springs, d. Two months later, the second molar extraction space was closed and third molar showed significant intrusion and mesial tipping. 209 Potential TAD Complications Figure 18. a. A deeply impacted mandibular canine caused by an odontoma needed to be retracted and erupted into its normal position. b. A microimplant inserted between the second premolar and the first molar (arrow) was used for anchorage to retract the mandibular canine. c. Six months after retraction and uprighting of the canine. - tooth is apical to the microimplant (Fig. 18). Giancotti and colleagues (2004) also reported a case in which microimplants were used as anchor- age to extrude and upright a severely impacted mandibular second molar. In contrast, if a pushing force is created by using microimplants. extrusive force will be achieved. Anke and colleagues (2004) reported a case in which they designed an apparatus in which a microimplant was used as anchorage to apply an extrusive force on a bridge. This extrusion of the bridge evened the gingival level with adjacent teeth and resulted in a more aesthetic prosthesis. Yun and co-workers (2005) describe a tech- nique in which the microimplant was used to provide indirect anchorage to upright an impacted mandibular second molar. Microimplants Cannot Provide 3-Dimensional Control Easily Many modern microimplants have edgewise bracket-like Su- pra-structure designs to allow orthodontists three-dimensional control of 210 Kuang tooth movement. However, orthodontists must have precise wire-bending technique to use these kinds of microimplants because the position be- tween the microimplant and line of the dental arch is uneven and the space for setting up the orthodontic apparatus is limited. The direction of the microimplant insertion (clockwise or coun- terclockwise) also must be considered. In general, the direction of micro- implant insertion is clockwise. If a microimplant is used with edgewise slot-and-loop mechanics to retract anterior teeth, it will be stable on the right side and unstable on the left side, because the axial direction of the moment created by the acting force is the same direction as the microim- plant insertion (clockwise). In contrast, if the microimplant is placed in the anterior region to protract the molar, the left side will be stable and the right side unstable (Fig. 19). Some manufacturers design microimplant with different insertion pathways. The clinician, therefore, must be very careful to use the correct microimplant in the each situation. Although microimplants designed with edgewise slots have some limitations, three-dimensional tooth control still can be achieved with modification of the microimplant. In the case seen in Figure 20, for ex- ample, the left first and second mandibular molars were lost and the third molar was tilted mesially. The plan was to upright the tilted third molar and use it as an abutment for mandibular dentures. Two microimplants were inserted at the edentulous area and a core of composite resin was built up on them. After that the implants were “banded” with a bracket, turning them into the equivalent of a single, “stationary ankylosed tooth,” which was used to upright the mesially tilted third molar. Five months later, the third molar was uprighted by the microimplant created “tooth” with no extrusion, which often accompanies traditional uprighting proce- dures (Fig. 21). Kyung and colleagues (2005) described a technique in which an orthodontic attachment was bonded to the head of a miniscrew; this modi- fied miniscrew then was used to correct root axis and rotation of a tooth. Altering the Occlusal Plane Orthodontists often insert microimplants for anchorage in the molar region and then use sliding mechanics to retract the anterior teeth. Because the microimplant usually is placed apically relative to the an- terior teeth, the orientation of the microimplant gives orthodontists the false impression that the sliding mechanics can retract and intrude an- terior teeth at the same time. However, based on many clinical cases, it 211 Potential TAD Complications - Figure 19. A microimplant with a rectangular slot for control of 3D tooth move- ment. In this case, both right and left first molars were protracted to close the edentulous space with a closing loop. a. The acting force will derotate the microimplant and cause the screw to loosen. b. In contrast, the closing force will ‘tighten” the microimplant because both microimplants were inserted in a clockwise direction. Figure 20. Modification of microimplants for 3D tooth control. a. Mandibular third molar mesially inclined due to early loss of first and second molars. b. Two microimplants inserted on the edentulous ridge. c. Composite resin was used to build up a “core” on the heads of the two microimplants. d: The “core” was banded with a bracket making it a stationary abutment for uprighting the third molar. appears that the overbite increases and does not decrease when using such mechanics (Fig. 22). Why does the overbite increase? When using 212 Kuang Figure 21. Top: Pretreatment panoramic film. Bottom: Post-treatment pan- oramic film. Note the third molar has been uprighted successfully without any unwanted extrusion. sliding mechanics to retract anterior teeth, a rigid continuous archwire is used. As Figure 23 illustrates, the continuous arch wire connects all of the teeth together as a single unit. In the maxilla, the center of resistance for the whole dentition is much higher than the point at which the microim- plant can be inserted, so all of the retraction force that is applied against the microimplant will pass below the center of resistance of the dentition. The retraction force on anterior teeth also creates a clockwise moment on the maxilla, and this moment makes the occlusal plane rotate clockwise. This is why the overbite is increased. There are several possible approaches that avoid making the bite deeper: • use loop mechanics instead of sliding mechanics (Fig. 24); • use a segmental arch approach (Fig. 25); • insert the microimplant just beneath the anterior nasal spine (Ohnish et al., 2005) or insert two microimplants between the lateral incisors and canines (Lin et al., 2006) to intrude the anterior teeth (Fig. 26); • use an intrusion arch in one arch and lever arms bilaterally in the other arch (Liou and Lin, 2007). 213 Potential TAD Complications Using microimplants to correct a canted occlusal plane also has been dis- cussed by Jeon and colleagues (2006). Figure 22. Eight months of treatment of an openbite case with sliding me- chanics using microimplants as anchorage to retract the anterior teeth in both arches. Even though the positions of microimplants are gingival to the anterior teeth, the original openbite became a deepbite after retraction. jºr A -ºº: Figure 23. Illustration of a microimplant used with sliding mechanics to change the occlusal plane. Point A is the most common place to in- sert a microimplant. Point B is the estimated center of resistance of the maxillary dentition. The retraction force on the anterior teeth always is below point B. This orientation creates a clockwise moment on the maxillary dentition and results in an increased overbite. 214 Kuang Figure 24. Loop mechanism combined with microimplants used for anterior teeth retraction and vertical control. a-b: Before retraction. c-d: After retrac- tion. Note the decreased overbite. Figure 25. Segmented arch combined with microimplants for anterior teeth retraction. a-b: At the beginning of en mass retraction of the anterior teeth. C-d. During retraction of the anterior teeth. Note how the overbite has de- creased during retraction. 215 Potential TAD Complications Figure 26. Anterior microimplants were added for overbite control during retraction of the anterior teeth. a-b: Two microimplants were inserted be- tween the lateral incisor and canine with elastic thread to intrude the anterior teeth. c-d: One microimplant was inserted in the anterior nasal spine using the closed method. A ligature wire was extended between the central incisors with an elastic ring to apply intrusive force. SUMMARY A workman wishing to make good his work must first sharpen his tools. Now that orthodontics has entered a new era of skeletal anchorage- supported treatment, orthodontists must acquire the knowledge and skill to use microimplants successfully. Orthodontists must educate their patients about this new tool, because treatment using microimplants still requires a modicum of patient cooperation to ensure success. Even though microimplants provide extra anchorage to help us achieve results that were not easily accomplished in the past, we should not give up the anchorage concepts that we have learned and depend only on microimplant-based anchorage. No matter what kind of anchorage we use, mechanics still are the basic tool for controlling tooth movement. Only by understanding completely the pros and cons of microimplant- based anchorage can we use this tool to accomplish our treatment goals ef- fectively and avoid the possible complications associated with this general treatment approach. 216 Kuang REFERENCES Anke R, Yildirim M, Diedric P. Force eruption with microscrew anchor- age for pre-prosthetic leveling of the gingival margin. Case report. J Orofacial Orthop 2004;65:513–519. Aranyarachkul P. Caruso J, Gantes B, Schulz E, Riggs M, Dus I, Yamada JM, Crigger M. Bone density assessments of dental implant sites: 2. Quantitative cone-beam computerized tomography. 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Clinical consideration of titanium miniscrew used for orthodontic anchorage. Clin J Periodontal 2005;10:229-239. 218 Kuang Lee S, Gantes B, Riggs M, Crigger M. Bone density assessments of dental implant sites: 3. Bone quality evaluation during osteotomy and im- plant placement. Int J Oral Maxillofac Implants 2007;22:208-212. Lin CY, Yeh CL, Liou JW. Severe “gummy Smile” correction using mini- implant anchorage. Implant Dent Supp 2006; 14:30–37. Liou EJ, Chen PH, Wang YC, Lin CY. A computed tomographic image study on the thickness of the infrazygomatic crest of the maxilla and its clinical implications for miniscrew insertion. Am J Orthod Dento- facial Orthop 2007;131:352-356. Liou EJ, Lin CY. The tomas system. In: Cope JB, ed. Ortho Tads: The Clinical Guide and Atlas. Dallas: Under Dog Media 2007:213. Liou EJ, Pai BC, Lin JC. Do miniscrews remain stationary under orth- odontic force? Am J Orthod Dentofacial Orthop 2004;126:42-47. Melsen B. Mini-implants: Where are we now? J Clin Orthod 2005:39:539- 547. Misch CE. Density of bone: Effect on treatment plans, surgical approach, healing, and progressive bone loading. Int J Oral Implantol 1990;6:23- 31. Miyawaki S, Koyama I, Inoue M, Mishima K, Sugahara T, Takano-Yama- moto T. Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage. Am J Orthod Den- tofacial Orthop 2003;124:373-378. Mizrahi E, Mizrahi B. Mini-screw implants (temporary anchorage devic- es): Orthodontic and pre-prosthetic application. J Orthod 2007:34:80– 94. Morea C, Dominguez GC, Wuo ADV, Tortamano A. Surgical guide for op- timal positioning of mini-implants. J Clin Orthod 2005:39:317-321. Motoyoshi M, Hirabayashi M., Uemura M, Shimizu N. Recommended placement torque when tightening an orthodontic mini-implant. Clin Oral Implant Res 2006; 17:109-114. Ohashi E, Pecho OE, Moron M, Lagravere MO. Implant vs. screw load- ing protocols in orthodontics. A systemic review. Angle Orthod 2006;76:721–727. Ohnish H, Yag T, Yasuda Y, Takada K. A mini-implant for orthodontic an- chorage in a deep overbite case. Angle Orthod 2005;75:444-452. Papadopoulos M, Tarawneh F. The use of miniscrew implants for tempo- rary skeletal anchorage in orthodontics: A comprehensive review. Oral Surg Oral Med Oral Path Oral Radiol Endod 2007;103:e6-e15. 219 Potential TAD Complications Park HS, Jeong SH, Kwon OW. Factors affecting the clinical success of screw implants used as orthodontic anchorage. Am J Orthod Dentofa- cial Orthop 2006;130:18-25. Poggio PM, Incorvati C, Velo S, Carano A. “Safe Zone”: A guide for mini- screw positioning in the maxillary and mandibular arch. Angle Orthod 2006;76:191-197. Roccia F, Tavolaccini A, Dellacqua A, Fasolis M. An audit of mandibu- lar fractures treated by intermaxillary fixation using intraoral cortical bone screws. J Craniomaxillofac Surg 2005:33:251-254. Schnelle MA, Beck FM, Jaynes RM, Huja SS. A radiographic evaluation of the availability of bone for placement of miniscrew. Angle Orthod 2004;74:832-837. Tseng YC, Hsieh CH, Chen CH, Shen YS, Huang IY, Chen CM. The ap- plication of mini-implants for orthodontic anchorage. Int J Oral Max- illofac Surg 2006:35:704–707. Wexler A, Tzadok S, Casap N. Computerized navigation surgery for the safe placement of palatal implants. Am J Orthod Dentofacial Orthop 2007;131:s100-s105. Yun SW, Lim WH, Chun YS. Molar control using indirect miniscrew an- chorage. J Clin Orthod 2005:39:661-664. 220 POTENTIAL COMPLICATIONS WITH TEMPORARY ANCHORAGE DEVICES: CLASSIFICATION, PREVENTION AND TREATMENT* Jason B. Cope John W. Graham The current enthusiasm for orthodontic temporary anchorage devices (Ortho'TADs) has encouraged a great number of orthodontists to become involved in this fast-growing and challenging field. Most orthodontists, however, are not formally trained in the placement and use of TADs and have treated few cases. While there are numerous case reports demonstrat- ing that OrthoIAD placement is predictable and stable (Bae et al., 2002; Bantleon et al., 2002; Erverdi et al., 2002; Chung et al., 2004; Hong et al., 2004), implementation of the procedure by clinicians who have no adequate training in the basic biological and biomechanical fundamentals germane to Ortho'TADs may lead to less-than-ideal treatment results or even complications. This in turn may lead to the inaccurate presumption that the procedure is ineffective. However, this false assumption can be disproved by understanding and using proper placement techniques. Often when a new technique, procedure, or appliance is devel- oped, the developers understand all too well the possible pitfalls encoun- tered during implementation. This may create the illusion for others that the procedure is technically simple. The difference, of course, is experi- ence. To quote James Boswell, “Men are wise in proportion, not to their experience, but to their capacity for experience.” Experience can be gained in three ways. First, it can be ascer- tained indirectly by obtaining fundamental knowledge before the fact. Second, it can be borrowed by learning from the success and failures of others. Third, it can be gleaned directly by experiencing complications firsthand. This chapter addresses the first two by presenting basic facts about anatomy, TADs, and biomechanics and by discussing the compli- cations incurred by clinicians as reported in the literature. The hope is *Excerpted from Graham JW, Cope JB. Potential complications with OrthoIADs: Classification, pre- vention, and treatment. In: Cope JB, ed. OrthoIADs: The Clinical Guide and Atlas. Under Dog Media, LP, Dallas, 2007, with permission (including all figures) from Under Dog Media, LP, www.orthotads. COIſl. 221 Potential TAD Complications that this indirect and borrowed experience will minimize significantly the complications experienced by future users of TADs. In addition, we have outlined a classification system of TAD-related complications. TERMS AND E)EFINITIONS A review of the TAD-related literature reveals two types of com- plications: • any unwanted event during treatment such as minor pain (Brănemark et al., 1969), cheek irritation (Erverdi et al., 2004), swelling/pain after flap closure (Miyakawa et al., 2003), soft tissue inflammation (Brănemark et al., 1969; Mi- yakawa et al., 2003; Erverdi et al., 2004) and screw tipping or migration (Erverdi et al., 2002); and • problems that change the outcome of treatment such as soft tissue overgrowth (Park et al., 2005), peri-implant infection (Cheng et al., 2004), screw failure caused by rotational forces (Costa et al., 1998), screw loosening (Brănemarket al., 1969; Miyakawa, 2003; Cheng et al., 2004), screw failure (Park et al., 2005), plate loosening (Sugawara and Nishimura, 2005), root shortening (Sugawara et al., 2002), and intrusion-associ- ated root resorption (Daimaruya et al., 2001, 2003; Sugawara et al., 2002; Ari-Demirkaya et al., 2005). The former suggests that even expected (but unwanted) sequelae such as temporary postoperative edema or discomfort should be considered com- plications. The latter actually may narrow the group of complications to only those that produce unexpected problems. In clinical practice, how- ever, identical complications (i.e., inadequate cortical purchase) may seri- ously affect the treatment outcome in one patient and minimally affect the treatment outcome in another patient. Alternatively, some minor, short- term problems such as soft tissue impingement may produce serious long- term problems (i.e., gingival recession). In order to define the scope of complications pertaining to Or- tho'TADs more clearly, we have defined the terms problem and compli- cations for use herein. A problem is a state of difficulty that needs to be resolved (Miller, 2003). Put another way, a problem is an occurrence during treatment that was not expected or predicted based on the treat- ment plan. If the problem is not identified or solved, it most likely will progress into a complication. A complication is a pathologic process or 222 Cope and Graham event occurring during a disease that is not an essential part of the disease; it may result from the disease or from independent causes (Kleinedler, 2002). In this instance, the “disease” is malocclusion. Fortunately, with Ortho'TADs, complications are infrequent, and when they do occur, they are rarely significant. Interestingly, there is often no direct relationship between prob- lems and complications; similar problems can create different complica- tions. Moreover, a single problem may possibly result in several compli- cations. For example, an inaccurately-used drill bit may leave an over en- larged pilot hole, with clinically imperceptible miniscrew implant (MSI) mobility, which, when immediately loaded with too high a force level, may cause MSI tipping or migration that may allow soft tissue impinge- ment by the attachment mechanics. It is important to pay attention to any problem that occurs during the course of treatment, even when this problem initially might seem in- significant. For example, slight soft tissue erythema and irritation around an MSI may not seem cause for concern, particularly because most or- thodontists are all too familiar with appliance-associated gingivitis. This localized inflammation adjacent to an MSI, however, has the potential to worsen because the MSI perforates the soft tissue and cortical bone and resides within the medullary bone. The orthodontist must address this problem immediately with vigorous oral hygiene protocols, chlorhexidine rinses, and more frequent follow-up appointments. If left unchecked, this problem could progress into a soft tissue infection that could progress to osteomyelitis. POTENTIAL PROBLEMS Problems that occur during TAD procedures can be divided into two major groups: (1) clinician- or auxiliary-related problems and (2) pa- tient-related problems. The first group can be subdivided further into three categories: (1) primary or strategic problems, (2) secondary or tactical problems, and (3) technical problems. Primary or strategic problems occur during treatment planning and may include incorrect indications for TAD use, unrealistic treatment objectives or inappropriate patient selection, which includes patients who are psychologically unprepared for TADs or who cannot implement the normal hygiene procedures required during TAD treatment. Other strate- gic problems include the selection of inappropriate biomechanics or inad- equate force level calculation for tooth movement. 223 Potential TAD Complications Secondary or tactical problems usually result from an inadequate attempt to correct a developing complication. This type of problem of ten results in a new pathologic condition (secondary complication) that sometimes is more difficult to correct than the initial complication. An ex- ample would be inadequate adjustment of the moment arm length (tactical problem) to correct upper incisor torque problems during retraction (initial complication), which, in turn, developed because of an inadequately cal- culated anterior segment center of resistance (strategic problem) during treatment planning. This may lead to premature anterior contact upon jaw closure, fremitus, incisor wear and dental pain. Technical problems are those that are made during a surgical procedure, application of attachment mechanics, or execution of tooth movement procedures. Technical problems usually are a direct result of insufficient training and/or lack of experience. An example would be in- accurate placement of the TAD, leading to inadequate biomechanics of orthodontic force attachments, inaccurate tooth movement, possible soft tissue impingement, or even damage to an adjacent tooth root. In addition, this group includes technical problems associated with TAD defects or fracture. Patient-related problems are those that may be attributed to poor compliance or failure to follow instructions such as inadequate oral hy- giene (Fig. 1), playing with the TADs or attachment mechanics with the tongue or fingers (Fig. 2), or engaging in activities that may damage the TAD or attachment mechanics. Patient-related problems are often directly related to insufficient patient/parent education and may occur because of strategic problems during treatment planning. POTENTIAL COMPLICATIONS The complications that may occur during Ortho'TAD use may be grouped into four categories: (1) bone, (2) tooth, (3) soft tissue, and (4) biomechanics. Bone Inadequate Primary Stability. Research clearly has demonstrat- ed that primary stability is critical for temporary anchorage devices. Pri- mary stability refers to the movement, or lack thereof, of a TAD upon initial placement. A lack of primary stability almost routinely leads to overt TAD mobility and subsequent failure. Recent evidence suggests that the majority of primary TAD stability is provided by cortical bone, with somewhat less stability provided by medullary bone (Dalstra et al., 224 Cope and Graham c Figure 1. Patient with poor oral hygiene/inflammation. A. MSI upon initial placement and activation. B. MSI after eight weeks of activation. Note the poor oral hygiene and inflammation around the MSI head. C. MSI after 10 weeks of activation. Note that good oral hygiene and a chlorhexidine rinse have com- pletely resolved the inflammation. Figure 2. Patient-induced MSI failure. A. Buccal photograph of initial MSI placement during first premolar extraction. B. Buccal photograph of MSI six Weeks after placement. Patient “did not realize” there was a problem. 2004). This group of complications basically results from inadequate Cortical bone around the TAD. Causes of inadequate primary stabil- ity can be divided into three major categories: (1) inadequate bone Stock, (2) pilot hole over enlargement, and (3) pilot drill overheating. Upon placement, an MSI should have at least 0.5 to 0.75 mm of available bone stock around its circumference. If not, the MSI has an increased risk of failure. Recently, several authors have provided data outlining predictable intraalveolar and extraalveolar sites that provide adequate bone stock for TAD placement (Schnelle et al., 2004; Costa et 225 Potential TAD Complications al., 2005; Poggio et al., 2006). If an MSI is placed in a region of question- able cortical bone thickness or density such as adjacent to a pneumatized sinus or a recent extraction site and the screw feels even subtly mobile, the orthodontist should consider a new location. MSI mobility is a certain pre- dictor of soft tissue irritation, which may increase the chance of infection. Because most TADs are intended to be placed and loaded at the same visit, the clinician should be confident that the miniscrew has adequate cortical bone purchase and exhibits no mobility. If mobility is present at the time of placement, it will never get better and most certainly will get worse. The TAD should be relocated immediately. Another reason for inadequate primary stability is an over-drilled pilot hole (Heidemann et al., 1998, 2001). This problem is more probable in thin cortical and soft cancellous bone (Nunamaker and Perren, 1976; Phillips and Rahn, 1989). The main reason for hole over-enlargement is inability to hold the handpiece stable and perpendicular to the bone sur- face during drilling. Any angular movement other than straight up-and- down during drilling will enlarge the pilot hole and minimize the tight fit of the MSI in the pilot hole. Excessive trauma during implant surgery is considered an im- portant cause of implant failure (Lundskog, 1972; Albrektsson and Er- iksson, 1985). During a pilot-hole osteotomy, most of the energy not used in the cutting process is transformed into heat. The amount of heat depends on the drill flute geometry (Jacobs et al., 1974; Wiggins and Malkin, 1976), the sharpness of the cutting tool (Adell et al., 1985), the pressure applied (Adell et al., 1985), the duration of the cutting action (Albrektsson and Eriksson, 1985; Ågren and Arwill, 1968), the cooling technique (Eriksson and Albreksson, 1984; Lavelle and Wedgewood, 1980), the speed of the drill (Costich et al., 1964; Bolla et al., 2002), and bone density (Yacker and Klein, 1996). These factors are important be- cause heat production leading to a temperature rise above 47°C for more than one minute negatively affects living bone (Eriksson and Albreksson, 1983) and compromises its regeneration (Thompson, 1958). It follows that placing a pilot hole for TADs can generate enough heat to damage bone. In this event, the bone margins of the pilot hole undergo necro- sis, followed by remodeling. This results in the hole getting larger, which may lead to decreased stability of the TAD. Importantly, this is a delayed complication that occurs one to three weeks after placement. The prob- ability increases in the posterior mandible, where cortical bone is thicker and denser than most other locations in the oral cavity. Complications in 226 Cope and Graham this area are best avoided by using drill-free screws or by using copious irrigation with brief, intermittent pressure during pilot hole placement. Insufficient Bone Plate Adaptation. For miniplate implants (MPIs), a well-formed plate is essential to avoiding complications. Inti- mate plate-to-bone contact is critical for two major reasons: first, complete miniscrew engagement is possible only if the plate is flush with the bone it contacts; and second, any “dead space” created by an ill-adapted bone plate will provide space for hematoma formation and a possible environ- ment for infection. The clinician must take the time to adapt the bone plate completely to fit the individual osseous anatomy while ensuring that the holes for screw placement are away from tooth roots and sinuses. Implant Mobility. Implant mobility can be divided into two peri- ods: immediate and delayed. Immediate mobility upon placement also is referred to as inadequate primary stability as covered earlier in this chap- ter. Delayed mobility occurs days to months after placement and is a sepa- rate entity. This type of mobility usually is caused by implant overloading or by epithelial ingrowth. Implant overloading is caused by force levels applied to the im- plant that exceed the functional loading capacity of the bone-to-implant interface. Although it might be assumed that orthodontic force levels are the only cause of this type of mobility, other factors should be consid- ered. Patient manipulation with the fingers or tongue also can overload the bone-to-MSI interface (Fig. 2). A traumatic accident such as getting hit in the face with a ball can dislodge an MSI. Not all mobile MSIs must be removed. Miniscrew implants with subtle, not frank, mobility of -1 (using the periodontal mobility score; Fleszar et al., 1980) need not be removed. If the MSI is stable enough to be loaded by orthodontic forces and has no frank mobility, it usually can be left in place. If the MSI is considerably mobile, it should be removed and replaced, because mobility can lead to other problems such as patient discomfort. Soon after an MSI becomes mobile, the surrounding peri-implant tissues may become irritated and in- flamed. This inflammation is not only painful to the patient, it also sets the stage for infection. Epithelial ingrowth also is possible, which would undermine any remaining mechanical purchase. This is different from the placement of a traditional dental implant, for which the gingiva and periosteum is re- flected prior to placement. When a drill-free MSI is placed, it is pushed through gingiva and periosteum, possibly introducing epithelial cells into the bone-to-screw interface. A key to the success of using MSIs may be 227 Potential TAD Complications immediate loading. Immediate loading creates pressure at the bone-to-im- plant interface, thus preventing epithelial ingrowth. If a TAD is not loaded immediately, epithelial ingrowth may occur between the bone and the im- plant, thereby leading to mobility that may worsen with time. One must keep this concept in mind when applying an elastic material to the TAD for activation. If the orthodontist allows the patient to go too long between visits with elastic thread or chain, the potential exists for loss of implant tension, followed by epithelialization of the bone-to-implant interface. Pa- tients must be educated before leaving the office with a TAD to recognize MSI mobility and to contact the orthodontist at once if MSI mobility oc- CUITS. Upon confirmation of frank implant mobility, the orthodontist should remove the loose MSI immediately and choose an alternate site located away from any inflammation to place a new MSI. If no alter- nate location is readily available, the patient should be sent home with a chlorhexidine rinse protocol, and the clinician should attempt reimplanta- tion after tissue irritation has subsided and the hole is filled by new bone. Oroantral Communication. During placement of a TAD in the maxilla, there is always a chance that the miniscrew might perforate the maxillary sinus. The possibility of this happening is increased if pneuma- tization of the sinuses is noted in the preoperative radiographic evaluation. The most concerning sequelae following a sinus perforation are postop- erative maxillary sinusitis and formation of a chronic oroantral fistula. The probability that either of these two sequelae will occur is related to the size of the communication. The diagnosis of a perforation is best performed by having the patient blow through the nose gently with the nostrils pinched together. If bubbling of air is observed at the site of the suspected perfora- tion, then a diagnosis of sinus perforation is established. An alternative test is to hold a mouth mirror over the suspected communication and have the patient gently breathe through the nose. If the mirror fogs, a diagnosis of sinus perforation is established. If the communication is 2 mm or less, no further management is required other than routine postoperative observa- tion and sinus precautions (Schow, 1993). This usually is the case, because most MSIs currently available are less than 2 mm in diameter. Sinus precautions help ensure that an adequate blood clot is formed and its integrity is maintained. Precautions include avoidance of nose blowing, sucking on straws, drinking of carbonated beverages, and smoking. Although not necessary routinely, the clinician may prescribe an antibiotic, a nasal decongestant, and an oral decongestant. The prima- 228 Cope and Graham ry reason for these medications is to prevent maxillary sinusitis by antibi- otic prophylaxis and maintenance of ostium patency. Should the communication be between 2 and 6 mm, a figure- eight suture over the site is recommended to preserve blood clot coverage. Again, sinus precautions should be followed. Any oroantral communica- tion greater that 6 mm should be considered for flap coverage by an oral and maxillofacial surgeon. Temporary Anchorage Peri-implantitis (TAP). Peri-implantitis has been studied extensively since the advent of osseointegrated implants. It is appropriate to include a discussion of peri-implantitis at this juncture because of the nature of the MSI location in bone. However, to label infec- tions involving the bone surrounding miniscrews as peri-implantitis is a misnomer. Peri-implantitis is defined as the pathologic changes confined to the surrounding hard and soft tissues adjacent to an Osseointegrated im- plant (Goldberg, 2002). The diagnosis of peri-implantitis is confirmed by a gradual loss of bone around an osseointegrated implant documented via probing depths and serial radiographs. Because no such osseointegration takes place with most TADs and their removal usually occurs less than 12 months after initial placement, a term that is more applicable to TADs in orthodontics is needed. For the purposes of this discussion, the term temporary anchorage peri-implantitis, or TAP, will be used to properly dif- ferentiate this phenomenon from true peri-implantitis. Much like peri-implantitis, TAP may result from anaerobic bacte- rial infection between the bone-to-miniscrew interface. Although peri-im- plantitis results in progressive attachment loss (not an issue with TADs), localized bone loss may occur with TAP, resulting in progressive mini- screw mobility and pain. Radiographic evidence may not be helpful in these situations, given the brief nature of the TAD role in an orthodontic treatment plan. As such, the clinician must identify the potential existence of TAP by clinical evaluation and move forward with appropriate TAP treatment. In the instance of peri-implantitis, great efforts are made to sal- vage an osseointegrated implant with a questionable future. Fortunately, TADs do not require such heroic efforts. Once identified, the miniscrew that has TAP should be removed. Antibiotic therapy generally is not in- dicated, although, several days of chlorhexidine rinses should be insti- tuted to aid in resolving any associated inflammation. Whether or not to place a new miniscrew immediately following the removal of the af- fected miniscrew is left to the judgment of the clinician. Allowing the 229 Potential TAD Complications periodontal tissues time to heal before placing another miniscrew in the immediate area certainly would be prudent. Tooth Root Impingement. Of all the potential complications that are possible with TAD placement, the most feared seems to be placing a miniscrew into a tooth root. There is a paucity of literature regarding this subject, howev- er, and only a few studies shed any light on the topic. In a study by Borah and Ashmead (1996), 387 consecutive facial fractures were examined for teeth transfixed by osteosynthesis screws. The incidence of root impinge- ment per screw was 0.47% (13 transfixed teeth per 2,340 screws). The results suggest that mandibular teeth are more at risk for screw impinge- ment than maxillary teeth by a ratio of 10:3 and that posterior teeth are more at risk than anterior teeth. Interestingly, none of the impinged teeth developed any documented periapical abscess during follow-up. None of the patients in the study were required to undergo endodontic treatment or surgical apicoectomy to any of the impinged teeth. The authors concluded that impingement of tooth roots by osteosynthesis screws during fracture fixation does not appear to adversely affect the survival of affected teeth. In fact, they suggest that if the periodontal ligament (PDL) or cementum is contacted, but there is no disruption of the apical neurovascular bundle or frank invasion of the pulp canal, the chance of devitalization is minimal. Further, the authors note that teeth that were transfixed generally do not become infected and do not appear to require extraction more often than similar adjacent teeth. A comparable study by Fabbronni and colleagues (2004) found similar results. Careful planning and determination of the precise implant loca- tion, radiographic survey evaluation, and clinical examination can mini- mize the risk of root impingement. If during the operative procedure, the clinician does not feel a “drop” into the medullary space as the drill bit or miniscrew continues to advance, the clinician should assume that the root is being contacted. Another sign of root impingement is failure of the screw to advance despite adequate operator pressure. Indication that a root has been contacted mandates miniscrew removal followed by re- direction away from the root (Fig. 3). This is the only step that is nec- essary in this instance, although the involved tooth should be observed during routine follow-up. To place an Ortho Implant (IMTEC Corp., Ardmore, Oklahoma) directly into a tooth root, even with the drill-free property of the screw, is nearly impossible (Fig. 4). Furthermore, the placement protocols call for a mere perforation of the cortical plate when 230 Cope and Graham Figure 3. MSI placement positions adjacent to tooth roots. A. Panoramic ra- diograph taken after the patient complained of diffuse pain on the right side of her face. Note the MSI position relative to the canine root (white circle). B. Panoramic radiograph taken immediately after removal and redirection of the right miniscrew (white circle), which left the patient pain free. the pilot hole is drilled. Care not to extend the pilot hole further into the bone should minimize the chance of contacting an adjacent tooth with the drill. If the PDL or cementum is contacted, the most frequent concern is that the tooth may undergo ankylosis. Evidence put forth by Tsukiboshi and colleagues (2001) and others (Andreasen and Kristerson, 1981) sug- gests that this is not likely. They indicate that deficits of PDL on the root Surface are repaired by new attachment, which is defined as regeneration and attachment of PDL tissue to a root surface that lost PDL pathologi- cally or mechanically. The mechanism for developing new attachment is formation of connective tissue between exposed root surface and sur- rounding tissue (bone and gingival connective tissue) by proliferation of cells derived from the PDL around the exposed root surface with addi- tion of cementum on the root and inclusion of Sharpey’s fibers into ce- mentum. The study protocol was to elevate a flap and prepare a cavity through bone, PDL, cementum and into dentin. Over the first three to nine days, the PDL proliferated from the ruptured PDL tissue. From day 14 to 21, new PDL tissue filled the cavity; new cementum was deposited on dentin, and bone was deposited on the socket wall. From day 21 to 28, bony healing progressed. From day 60 to 470, the cavity was repaired by new cementum and PDL, with the PDL space eventually being re- established. It appears that healing was determined by three factors, the most important of which was vitality of the PDL. The other factors were the deficit size on the root and the distance of the cavity from the socket Wall. The authors found that up to 2 mm of PDL width loss on the root 231 Potential TAD Complications Eº º Figure 4. Potential tooth root damage. A. Extracted tooth before pilot hole and implant placement. B. Extracted tooth after pilot hole and implant placement. Note that less than 0.25 mm of surface indentation is evident. C. Moderate pressure was used to place a pilot hole with a 1.1 mm pilot drill in a slow-speed handpiece. D. Maximum force was used for 10 complete 360° revolutions us- ing the original IMTEC non-drill-free Ortho Implant (round tip). E. Maximum force was used for 10 complete 360° revolutions using the new IMTEC drill- free Ortho Implant (sharp tip). surface can be repaired by new attachment with no ankylosis. Again, most MSIs currently available are less than 2 mm in diameter. Soft Tissue Soft Tissue Tearing. Careful attention is sufficient to avoid most soft tissue injuries. With the vast majority of TAD placements, little or no soft tissue manipulation is required. If a miniscrew is placed in an area that is covered by attached gingiva, an indirect approach may be 232 Cope and Graham used to avoid the likelihood of soft tissue trauma. After anesthetizing the area, the clinician uses a slow-speed drill to puncture the attached gingiva and cortical bone, after which the clinician places the miniscrew without further tissue manipulation. Some have suggested using a sterile tissue punch to remove attached gingiva and periosteum, followed by a slow- speed drill to perforate the cortical plate. If a drill-free miniscrew is used, the clinician inserts the screw through the attached gingiva and manually screws it into the cortical bone without the aid of a drill (Fig. 5). This is the simplest method of miniscrew placement, but it requires bone thin enough to facilitate penetration by the miniscrew alone. Mandibular cortical bone, 3 mm or more thick, may prove to be too dense in some instances to allow drill-free insertion of a miniscrew. Figure 5. Standard placement of a drill-free screw through attached gingiva. A. Buccal photograph of initial MSI placement after topical anesthetic application. B. Buccal photograph taken on completion of MSI placement. C. Buccal photo- graph of final MSI position. There may be cases in which a miniscrew needs to be placed in a location that is covered by unattached gingiva. In this instance, it is nec- SSSary to use a sterile tissue punch to remove mucosa and periosteum. If 233 Potential TAD Complications a tissue punch is not used, the mucosa has a tendency to wrap around the drill or MSI during insertion, causing needless soft tissue trauma. Miniplate implant use requires a mucoperiosteal flap to provide adequate adaptation of the miniplate. The most common injury in flap procedures is tearing of the flap itself. Tearing usually is a by-product of inadequate flap size, requiring retraction for visualization that is beyond the ability of the tissue to withstand. To prevent tearing of a mucoperios- teal flap, the operator must visualize how much access will be necessary to place the MPI and then make the flap large enough to accommodate such access. Retraction forces should always be minimal, and the clinician should inspect the edges of the incision frequently for tears. If a flap tear should occur, the flap should be carefully repositioned such that the clini- cian can adequately suture the tear without placing the flap under tension. Improper Temporary Anchorage Device Emergence. Evaluation of the location of the terminal attachment of a TAD and its relationship to the force vector desired is critical. If, for instance, one is using an MPI and it is properly adapted to the bone, but the plate fails to emerge from the flap as desired or is in the incorrect location for the required biomechan- ics, the clinician should remove the plate and reposition it. It is important to ensure that, after an MPI is placed in an ideal location and position, the flap is sutured such that the terminal attachment hole is completely visible to allow proper engagement after surgery. The same is true for miniscrew placement. One must be sure that if the miniscrew traverses soft tissues such as that in the area of the zygomatic buttress it is long enough to at- tain a strong cortical engagement and an adequate emergence into the oral cavity. Another aspect of emergence that must be addressed is the local tissue irritation that a high-profile TAD may cause. If the TAD emergence profile is too prominent, significant irritation to adjacent soft tissue struc- tures may occur. For example, MSIs placed between the maxillary lateral incisors and canines for anterior segment intrusion may inadvertently em- bed themselves in the soft tissue of the upper lip (Fig. 6). This situation may be initially treated conservatively with chlorhexidine rinses and lib- eral applications of orthodontic wax, but removal of the miniscrews may be required if the irritation and swelling persist. Soft Tissue Impingement. Once biomechanical activation is initi- ated following TAD placement, evaluation of the local soft tissues and their relationships to elastics, open coil springs and the like is critical. 234 Cope and Graham Figure 6. MSI-induced soft tissue trauma. Two days after MSI placement, the patient returned with soft tissue ulceration (black circle) from MSI placement high in the vestibule. Soft tissues that are adjacent to the TAD itself or close to auxiliary me- chanical devices are subject to trauma and irritation (Fig. 7). Careful ex- amination of all soft tissues after active mechanics have been initiated is important to the ultimate success of TADs. Patients should be aware of What has been attached to the TAD and know how to evaluate any discom- fort they might have subsequent to placement and activation. For those instances in which soft tissue impingement occurs, auxiliaries such as hooks, arms (Fig. 8) or ligatures may be used to redirector relieve gingival pressure created during TAD use. Temporary Anchorage Peri-implant Mucositis (TAM). As the name Suggests, peri-implant mucositis is a localized infection of the mar- ginal tissues surrounding TADs. This is a reversible inflammatory change that is analogous to gingivitis and is primarily an inflammatory disorder Caused by plaque accumulation (Pontoriero et al., 1994). Once proper hygiene is established, the inflammation resolves without any permanent bone or tissue damage. Implant removal in these cases is not necessary unless the patient is unable to maintain adequate hygiene or the inflam- mation does not subside within several days. The inflammation should be addressed immediately, however, because Cheng and colleagues (2004) Suggest that bacteria play a role in the failure of orthodontic MSIs. 235 Potential TAD Complications Figure 7. MSI attachment-induced soft tissue trauma. The NiTi spring placed from the MSI to protract the maxillary molar caused gingival blanching (black circle), indicating undue pres- sure on the soft tissues. A - - Figure 8. Correction of MSI attachment-induced soft tissue trauma. A. The NiTi spring placed from the MSI to retract the mandibular anterior teeth was embedded in the gingival tissue. Note the overgrowth of tissue around the closed coil spring (black circle). B. The simple addition of an auxiliary wire lifts the coil spring away from the gingiva and corrects the problem. Soft Tissue Infection. Although relatively uncommon, localized infections caused by TAD placement and activation can and do occur. The placement of TADs to facilitate orthodontic mechanics requires vigilant clinical examination for the presence of TAD mobility and soft tissue infection. Fortunately, TAD-related infections are easy to recognize and treat. Locally, signs and symptoms such as pain, swelling, surface ery- thema, pus formation, and TAD mobility are possible. Recall that not all of the clinical signs of infection need to be apparent for infection to be present (Peterson, 2002). On routine follow-up, slight erythema and MSI mobility may be noted. In this instance, the orthodontist’s clinical judg- ment must guide the course of therapy. 236 Cope and Graham Slight erythema and discomfort immediately adjacent to a TAD indicate the early signs of a localized infection. If caught early enough, placing a patient on a regimen of chlorhexidine gluconate rinses for five to seven days and reviewing proper hygiene practice are sufficient to amelio- rate the infection (Fig. 9). If the infection persists for more than ten days or worsens, it is imperative to remove the TAD to allow for infection resolu- tion and complete tissue healing. The orthodontist must decide whether to prescribe oral antibiotics for a TAD-related infection. Frank pus, increas- ing pain, fever, malaise, and other signs of a progressive infection indi- cate the need for antibiotics. Upon resolution of the active infection, the clinician may choose a suitable alternative location for TAD placement. In order to avoid further infection, frequent office visits and examinations are prudent necessities for a patient who has experienced a TAD-related infection. Figure 9. Soft tissue infection. A. Initial placement of an MSI with O-Cap to pre- Vent cheek irritation. B. Twelve weeks after initial placement, the patient returned With a soft tissue infection caused by embedding of the closed coil spring into the gingiva and excessive pressure caused by sleeping habits. C. The O-Cap was removed, the site was well-irrigated, oral hygiene procedures were reviewed, and chlorhexidine and antibiotics were prescribed for ten days. D. Seven days later the infection was resolved without the need for MSI removal. 237 Potential TAD Complications Neurovascular Impingement. A solid understanding of the neuro- vascular anatomy within the oral cavity should prevent any neurovascular impingement. Fortunately, miniscrews are small, and if vascular damage does occur, treatment is straightforward. If excessive, continuous bleeding is noted immediately upon insertion of the miniscrew or drill bit, the clini- cian should remove the screw and apply direct pressure until hemostasis is achieved. Once the bleeding has stopped, another location may be chosen and the procedure continued. The patient will note nerve impingement as continued discomfort after the effects of the local anesthetic have ended. In this situation, the clinician should anesthetize the area once again and remove and redirect the miniscrew. This is the same protocol used for tooth root impingement. Nerve impingement is rarely an issue when using topical anesthetic alone or with local infiltration. With these techniques, the PDL and tooth roots are not anesthetized, which allows the patient to sense the discomfort be- fore PDL contact or root impingement. Often the patient will describe a diffuse pain involving the ipsilateral side of MSI placement (Fig. 3). Biomechanics Undesirable Tooth Movement. A well-thought-out vector analysis is critical to TAD success. Unwanted intrusive or extrusive movements are common with TADs unless careful attention is paid to the vectors and forces involved. Molar intrusion may introduce unwanted tipping or crown torque unless proper counter forces are used to prevent such prob- lems. If, for example, a TAD is used in the buccal cortex to intrude a maxillary molar, a force must be placed on the lingual via another TAD, or the molars must be stabilized by a transpalatal arch to prevent unwanted buccal crown torque. Retraction of anterior tooth segments may be subject to intrusive forces or to excessive palatal crown torque. If intrusion is not part of the treatment plan, auxiliaries must be used to place the TAD force vector closer to the center of rotation, thus inducing a translational move- ment of the segment. Temporary Anchorage Device Interference. When TADs are used to assist in dental intrusion, it is important to evaluate the anticipated path of the tooth in question. Often, in an attempt to optimally locate a TAD for intrusion, the body of the implant is placed directly in the path of the tooth. Progression of the intrusive movement will obviously be arrested, and continued forces on the tooth may contribute to iatrogenic root resorp- tion. 238 Cope and Graham Evaluating the path of the tooth to be moved before TAD place- ment also is necessary to avoid the need for moving the anchor during therapy due to loss of mechanical advantage. For example, it is important to make sure that the MSI is placed far enough away from the tooth in question to provide ample distance for continuous activation. If a mini- Screw is placed too close to the tooth that must be intruded, there may be a point during treatment at which the miniscrew no longer can provide anchorage. In fact, the MSI itself may interfere with the mechanics of the movement (Fig. 10). B - - - Figure 10. MSI interference with tooth movement. A. Initial palatal photograph of MSI used for maxillary molar intrusion (white circle). B. Progress palatal pho- tograph of MSI used for maxillary molar intrusion. Note the relationship of the palatal MSI relative to the arch wire (white circle). The MSI impeded further intrusion and had to be removed and replaced more apically to allow continued intrusion. Temporary Anchorage Device Fracture. Although infrequent, the chance for miniscrew fracture always exists during the placement pro- cedure. When the miniscrew fractures at the level of the bone, making removal difficult, it may be appropriate to leave the miniscrew in place. The clinician should choose another site adjacent to the fractured screw and place a new miniscrew. In this instance, a postoperative radiograph can determine whether root impingement is the cause for the miniscrew fracture. If the root has been contacted or penetrated by the fractured mini- Screw, removal of the remnant is necessary to avoid any possible sequelae. If the miniscrew is difficult to remove, a small, round bur can be used to Create a trough around the exposed miniscrew remnant, allowing adequate access for retrieval. On occasion, implant fracture may occur postoperatively during the course of TAD activation. The protocol for this situation is the same as for fractures that occur during implant placement. If the miniscrew 239 Potential TAD Complications remnant is accessible, the clinician can remove it and place a new mini- screw in a different location. If the miniscrew remnant is difficult to re- move, it may be left in place. It is important to attempt to identify any possible causes of mini- screw fracture such as occlusal forces, eating of inappropriate foods, and parafunctional habits so that a repeat fracture does not occur. The clinician must educate the patient as to the potential for screw fracture and the pro- tocol that will be followed should it occur. THE LEARNING CURVE As with any new procedure, a learning curve accompanies the placement and use of TADs. Fortunately, the placement procedure is straightforward. The greatest leap of faith that a practitioner must make is in the placement of the first five to ten TADs. Complications associated with proper TAD use are infrequent and usually minor. Proper treatment planning, tempered with appropriate clinical judgment, will avoid almost all potentially serious complications. As mentioned previously, most prob- lems encountered with TADs prove to be more of a nuisance than anything else. SUMMARY The relatively new introduction of temporary skeletal anchorage to the orthodontic world opens up an entirely new era of biomechanics. Natu- rally, because of the invasive nature of this treatment modality, clinicians may hesitate to introduce TADs into their routine practice. Fortunately, there seem to be few case reports in the literature of complications caused by the placement and use of these devices. In the coming years, additional case reports and randomized clinical studies will likely demonstrate that the benefits of TADs far outweigh the potential risks, thus allowing the orthodontist to expand the scope of treatment options for all patients. REFERENCES Adell R, Lekholm U, Brânemark PI. Surgical procedures. In: Brănemark PI, Zarb GA, Albreksson T, eds. Tissue Integrated Prostheses: Osseo- integration in Clinical Dentistry. Chicago, Quintessence Publishing CO. Inc. 1985:211-232. 240 Cope and Graham Ågren E, Arwill T. 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World J Orthod 2002:3:109-116. Bolla E, Muratore F, Carano A, Bowman SJ. Evaluation of maxillary mo- lar distalization with the distal jet: A comparison with other contem- porary methods. Angle Orthod 2002;72:481-494. Borah GL, Ashmead D. The fate of teeth transfixed by osteosynthesis screws. Plast Reconstr Surg 1996;97:726-729. Brănemark P-I, Adell R, Breine U, Hansson BO, Lindstrom J, Ohlsson A. Intra-Osseous anchorage of dental prostheses. I: Experimental studies. Scand J Plast Reconstr Surg 1969;3:81–100. - Cheng SJ, Tseng IY, Lee JJ, Kok S-H. A prospective study of the risk factors associated with failure of mini-implants used for orthodontic anchorage. Int J Oral Maxillofac Implants 2004;19:100-106. Chung K, Kim S-H, Kook Y. C-Orthodontic microimplant for distaliza- tion of mandibular dentition in Class III correction. Angle Orthod 2004;75:119-128. Costa A, Pasta G, Bergamaschi G. Intraoral hard and soft tissue depths for temporary anchorage devices. Semin Orthod 2005; 11:10-15. Costa A, Raffaini M, Melsen B. Miniscrews as orthodontic anchorage: A preliminary report. Int J Adult Orthod Orthognath Surg 1998;13: 201–209. 241 Potential TAD Complications Costich E, Youngblood P. Walden J. A study of the effect of high speed rotary instruments on bone repair in dogs. Oral Surg Oral Med Oral Path 1964; 17:563-571. Daimaruya T, Nagasaka H, Umemori M., Sugawara J, Mitani H. The in- fluence of first molar intrusion on the inferior alveolar neurovascular bundle and root using the skeletal anchorage system in dogs. Angle Orthod 2001;71:60-70. Daimaruya T, Takahashi I, Nagasaka H, Umemori M., Sugawara J, Mi- tani H. Effects of maxillary molar intrusion on the nasal floor and tooth root using the skeletal anchorage system in dogs. Angle Orthod 2003;73:158-166. Dalstra M, Cattaneo PM, Melsen B. Load transfer of miniscrews for orth- odontic anchorage. Orthod 2004;1:53-62. Eriksson R, Albreksson T. Heat caused by drilling cortical bone: Tempera- ture measured in vivo in patients and animals. Acta Odontol Scand 1984:55:629–631. Eriksson R, Albreksson T. Temperature threshold level for heat-induced bone tissue injury: A vital-microscope study in the rabbit. J Prosthet Dent 1983:50:101-107. Erverdi N, Keles A, Nanda R. The use of skeletal anchorage in openbite treatment: A cephalometric evaluation. Angle Orthod 2004;74:381- 390. Erverdi N, Tosun T, Keles A. A new anchorage site for the treatment of an- terior open bite: Zygomatic anchorage – Case report. World J Orthod 2002:3:147-153. Fabbronni G, Aabed S, Mizen K, Starr DG. Transalveolar screws and the incidence of dental damage: A prospective study. Int J Oral Maxillofac Surg 2004:33:442-446. Fleszar T, Knowles J, Morrison E, Burgett FG, Nissle RR, Ramfjord SP. Tooth mobility and periodontal therapy. J Clin Periodontol 1980;6: 495–505. Goldberg M. Control and prevention of infection in the surgical patient. In: Topazian RG, Goldberg MH, Hupp JR, eds. Oral and Maxillofa- cial Infections. Philadelphia, WB Saunders, 2002:468–483. Heidemann W. Gerlach KL, Grobel KH, Kollner HG. Drill free screws: A new form of osteosynthesis. J Craniomaxillofac Surg 1998:26:163– 168. Heidemann W, Terheyden H, Gerlach KL. Analysis of the osseous/metal interface of drill free screws and self-tapping screws. J Craniomaxil- lofac Surg 2001:29:69–74. 242 Cope and Graham Hong R-K, Heo J-M, Ha Y-K. Lever-arm and mini-implant system for an- terior torque control during retraction in lingual orthodontic treatment. Angle Orthod 2004;75:129-141. Jacobs C, Pope M, Berry J, Hoagland F. A study of the bone machining process: Orthogonal cutting. J Biomech 1974;7:131-136. Kleinedler S. The American Heritage(R) Stedman s Medical Dictionary. Boston, Houghton Mifflin Co., 2002. Lavelle C, Wedgewood D. Effect of internal irrigation on frictional heat generated from bone drilling. J Oral Surg 1980:38:499-503. Liou EJ, Pai BCJ, Lin JC. Do miniscrews remain stationary under orth- odontic forces? Am J Orthod Dentofacial Orthop 2004;126:42-47. Lundskog J. Heat and bone tissue: An experimental investigation of the thermal properties of bone tissue and threshold level for thermal in- jury. Scand J Plast Reconstr Surg 1972;6:5-75. Miller G. WordNet (computer program). Version 2.0. Princeton, Princeton University, 2003. Miyakawa S, Koyama I, Inoue M, Mishima K, Sugahara T, Takano-Yama- moto T. Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage. Am J Orthod Den- tofacial Orthop 2003;124:373-378. Nunamaker DM, Perren SM. Force measurements in screw fixation. J Bio- mech 1976;9:669-675. Park HS, Lee SK, Kwon OW. Group distal movement of teeth using mi- croscrew implant anchorage. Angle Orthod 2005;75:510-517. Peterson L. Principals of surgical and antimicrobial infection manage- ment. In: Topazian RG, Goldberg MH, Hupp JR, eds. Oral and Maxil- lofacial Infections. Philadelphia, WB Saunders, 2002:99. Pontoriero R, Tonelli M, Carnevale G, Mombelli A, Nyman SR, Lang NP. Experimentally induced peri-mucositis: A clinical study in humans. Clin Oral Implants Res 1994;5:254-259. Phillips JH, Rahn BA. Comparison of compression and torque measure- ments of self-tapping and pre-tapped screws. Plast Reconstr Surg 1989;83:447-456. Poggio PM, Incorvati C, Velo S, Carano A. Safe zones: A guide for minis- crew positioning in the maxillary and mandibular arch. Angle Orthod 2006;76:191-197. Schnelle MA, Beck FM, Jaynes RM, Huja S. A radiographic evaluation of the availability of bone for placement of miniscrews. Angle Orthod 2004;74:830-835. 243 Potential TAD Complications Schow S. Odontogenic diseases of the maxillary sinus. In: Peterson L, Ellis E III, Hupp J, Tucker MR, eds. Contemporary Oral and Maxil- lofacial Surgery. St Louis, Mosby-Year Book, 1993:465-482. Sugawara J, Baik U, Umemori M., Takahashi I, Nagasaka H, Kawamura H, Mitani H. Treatment and post-treatment dentoalveolar changes fol- lowing intrusion of mandibular molars with application of a skeletal anchorage system (SAS) for open bite correction. Int J Adult Orthod Orthognath Surg 2002; 17:243-253. Sugawara J, Nishimura M. Mini bone plates: The skeletal anchorage sys- tem. Semin Orthod 2005; 11:47-56. Thompson H. Effect of drilling into bone. J Oral Surg. 1958; 16:22-30. Tsukiboshi M, Asai Y, Nakagawa K, Ichinokawa H, Sanada H. Wound healing in transplantation and replantation. In: Tsukiboshi M, ed. Au- totransplantation of Teeth. Tokyo, Quintessence, 2001:21-56. Wiggins K, Malkin S. Drilling of bone. J Biomech. 1976;9:553–559. Yacker M, Klein M. The effect of irrigation on osteotomy depth and bur diameter. Int J Oral Maxillofac Implants 1996; 11:634-638. 244 SURGICAL RECOVERY AND PATIENT COST ASSOCIATED WITH TEMPORARY SKELETAL ANCHORAGE TREATMENT OF OPEN BITE Jon W. Silcox Jesse Donald Arbon J.F. Camilla Tulloch The use of temporary skeletal anchorage is an evolving clinical technique that has an intriguing potential to facilitate the treatment of “difficult to manage” malocclusions. In the past, malocclusions such as open bite could be definitively treated only by orthognathic surgical correction. The effectiveness and stability of open-bite treatment using a LeFort osteoto- my has been well documented (Bailey et al., 1994; Swinnen et al., 2001). Multiple reports of open-bite closure with the use of screw or mini-plate anchorage now have been published (Sherwood et al., 2002; Sugawara et al., 2002; Park et al., 2004). The purpose of this investigation is not to Validate the success or effectiveness of open-bite treatment using skeletal anchorage, but to compare this type of treatment to the current standard approach of treatment (maxillary osteotomy) in terms of recovery and cost. If temporary skeletal anchorage proves to be as effective and stable as maxillary osteotomy for posterior intrusion, the clinical implications will be significant, as both practitioners and patients then will have a less invasive and less cost restrictive treatment option. - Planning treatment for patients with anterior open bite resulting from vertical discrepancy of the posterior maxillary and/or mandibular units can be complex. Variations in the rate and amount of growth in both the maxillary complex and the mandibular condyles influence ver- tical development. While it is sometimes possible to identify specific etiologic factors, in many instances neither the causes nor the full extent of the deformity are apparent in the preadolescent patient. Unfortunately, the severity of the condition frequently increases with continued verti- cal growth into early adulthood (Schudy, 1965; Isaacson et al., 1977). The most common morphological pattern seen in open-bite patients is increased vertical development of the posterior maxillary dentoalveolar unit, resulting in an increased mandibular plane angle and an increased anterior lower facial height (Schudy, 1965; Sassouni, 1969; Frost et al., 1980; Proffit and Fields, 1993). Not surprisingly, therefore, clinicians 245 Temporary Skeletal Anchorage have long felt that the primary area to which treatment should be direct- ed is the posterior maxilla (Schudy, 1965; Creekmore, 1967; Frost et al., 1980). Treatment options for patients with open bite must be related not only to the location and the extent of the deformity, but also to the pa- tient’s age. A number of non-surgical approaches have been described, but these usually require high levels of patient compliance and must gener- ally be continued over an extended period of time until vertical growth is complete (Nielsen, 1991; Rinchuse, 1994; Woodside and Aronson, 1997). Even then, the long-term stability of orthodontic correction of open bite has been disappointing, with a high percentage of patients experiencing significant relapse, which generally is associated with a continued increase in posterior maxillary height and downward and backward rotation of the mandible (Burford and Noar, 2003). These changes, particularly when coupled with relapse of extruded incisors, can lead to significant relapse and bite-opening (Lopez-Gavito et al., 1985). The lack of stability of orthodontic correction of open bite led to the development of surgical techniques for treatment, including the con- temporary approach of a LeFort I down fracture and superior position- ing of the maxilla following removal of bone from the lateral wall of the nose and nasal septum (Bell and McBride, 1977). The maxilla may be positioned superiorly as one piece or in multiple segments. In so doing, the face height decreases, the mandible rotates upward and forward, and the open bite is closed. Although longitudinal studies have shown that surprising amounts of change occur beyond the one-year post-treatment period, relapse of the open bite appears to be unlikely for the majority of these patients (Proffit et al., 2000). Five-year follow-up studies identi- fied approximately 30% of surgically treated patients as having continued downward movement of the maxilla and downward and backward rota- tion of the mandible very similar to the pattern of growth that produced the long-face/open-bite condition initially (Bailey et al., 1994). Despite this tendency for continued skeletal change, in the long term the overbite is as likely to increase as it is to decrease, presumably because of contin- ued compensatory eruption of the incisors (Proffit et al., 2000). Although traditionally reported as a less stable procedure (Epker and Fish, 1977), open bites also may be closed using a mandibular sagittal split osteotomy and upward rotation of the distal segment of the mandible. The introduc- tion of rigid fixation has reportedly increased the stability of this surgi– cal approach, but the long term success currently is not well documented (Joondeph and Bloomquist, 2004). 246 Silcox et al. The first reported use of temporary, implantable devices as skeletal anchorage for tooth movement was in 1945. Vitallium screws were placed in the mandibular rami of dogs to retract canine teeth without disturb- ing the position of the molars (Gainsforth and Higley, 1945). Although tooth movement was limited due to the loosening of the implants, this work set the stage for further development of temporary skeletal anchor- age devices (TSAD) in orthodontics. Relatively recent clinical advances again have increased interest in temporary skeletal anchorage devices that do not move significantly when subjected to orthodontic forces and that allow tooth movement that is not traditionally achieved. The ability to acquire absolute anchorage from implanted devices rather than teeth them- selves—devices that require little patient compliance and that can be used as readily in adults as in adolescents—has changed the options for orth- odontic treatment. Currently there are several types of temporary skeletal anchorage devices in use. Palatal implants and onplants, which are placed in the denser and thicker bone of the palate in prepared sites under the mucosa, are uncovered and loaded after osseointegration occurs and frequently must be removed using a trephine. Mini- or microscrews, analogous to oral surgery fixation screws, are placed by penetrating the attached muco- sal tissue and generally are loaded within four weeks of placement. These small titanium screws generally do not become osseointegrated and can be removed easily without surgery, although some clinicians feel that mini- or microscrew implants become osseointegrated if allowed to heal submu- cosally for three months prior to surgical uncovering and loading (Kano- mi, 1997). Miniplates, which are modifications of the traditional fixation plates used in orthognathic surgery, usually are placed in the Zygomatic buttress and require a surgical mucoperiosteal flap for both placement and removal. They have an extension arm that exits the mucosa to allow at- tachment of orthodontic appliances. Miniplates generally are considered to be mechanically retained and usually do not become extensively osseo- integrated over the relatively short time they are in place. Case reports and experimental animal model data have demon- strated the potential of temporary anchorage devices’ ability to provide absolute anchorage for posterior tooth intrusion in the treatment of open bite, thereby providing an attractive alternative to surgical correction (Umemori et al., 1999; Sherwood et al., 2002; Erverdi et al., 2006). To date, there are only anecdotal reports on the stability of open-bite correc- tion using temporary skeletal anchorage devices (Sugawara et al., 2002); 247 Temporary Skeletal Anchorage there are no long-term reports on physiologic adaptation to this type of treatment. Preliminary reports on patient perception of the use of miniplates only now are appearing in the literature; they suggest that there is broad patient acceptability with little associated morbidity. A prospective study of 97 consecutive patients treated with miniplates (Cornelis et al., in press) reported that: (1) the principal adverse outcome was swelling of the cheeks, which generally persisted for about five days following the Surgery; (2) greater than 50% of the patients reported no pain associated with anchor placement or removal; (3) 100% found miniplates to be more tolerable than headgear; and (4) more than 50% reported that their experience with dental ex- tractions was worse than their experience with miniplates. Miniscrews have been used to provide anchorage for posterior tooth intrusion, but they present a placement challenge vis-a-vis creating an effective force application while remaining clear of tooth roots and not becoming submerged under the unattached oral mucosa. However, there are problems with miniscrew use including screw fracture (Buchter et al., 2006), loosening under loading (Liou et al., 2004), and impinge- ment on roots either at the time of placement or during treatment (Park et al., 2003). Management of an open bite with miniscrews requires care- ful initial placement and may involve repositioning the devices to allow the intended tooth movements without contacting tooth roots. Miniplates placed at a distance from tooth roots offer the advantage of reduced risk of root impingement and are associated with a lower failure rate than minis- crews (Buchter et al., 2006). The introduction of any new technology or technique should be accompanied by systematic evaluation not only of the effectiveness of the new treatment method, but also its associated morbidity and side effects. Such comparisons should be made against current practices or the best available alternative treatment, which in this case is a LeFort I osteotomy. Recovery from orthognathic surgery can vary markedly, but certain morbidities seem to predominate post-surgically such as pain, swelling, bruising and bleeding, restriction of oral function, reduction in a feeling of well-being, limitation of social and work/school related ac- tivities, and nerve damage or altered sensation (Neal and Kiyak, 1991; Dickerson et al., 1993; Williams et al., 2004; Phillips et al., 2006). 248 Silcox et al. Some of the same sequelae also are experienced by patients following surgical placement of TSADs. Information on the degree to which pa- tients might expect to experience such sequelae following treatment for open bite, either by LeFort I osteotomy or TSAD placement, is important if patients are to make a reasonably informed decision about alternative treatment options. In addition, each treatment option carries with it time and financial costs, all of which must be considered as part of the treatment decision. This is especially important considering the difficulty or inabil- ity some patients have in obtaining insurance coverage for orthognathic Surgical procedures. SURGICAL EXPERIENCE AND RECOVERY Orthognathic surgery patients at the University of North Carolina (UNC) complete a series of recovery diaries consisting of daily question- naires with 20 questions designed to assess the patients’ perception of re- covery in four main areas: general activity, oral function, pain, and other symptoms encountered shortly after surgery. Patients complete these daily questionnaires for three months following surgery. Identical ques- tionnaires were given to a group of orthodontic patients who were treated with bilateral miniplate anchors secured to the zygomatic buttress. These TSAD patients completed the daily health diaries for 14 consecutive days beginning the day after surgical placement of the miniplates and on the 21st day after placement. To compare the surgical experience of open-bite patients treated with maxillary osteotomy and patients treated with miniplates, two groups of patients were identified. The first consisted of patients who were treat- ed by LeFort I osteotomy and who completed the recovery diaries (13 females and 8 males). These patients were treated in the same hospital setting, but by three different oral surgeons. The mean age of this group at the time of surgery was 26.2 years with a range of 17.4 to 39.7 years. Twelve patients had one-segment surgical superior repositioning of the maxilla, four had a two-segment surgery, and five required three-segment Surgery. No other surgical procedures were performed. The TSAD group consisted of 20 patients (13 females and 7 males) treated in the Orthodontic Department at the School of Dentist- ry at UNC who also completed the recovery diaries. These patients all underwent bilateral mucoperiosteal flap surgery for placement of tempo- rary skeletal anchors with fixation to the zygomatic buttress. In addition, one patient had two mandibular miniscrews placed and one patient re- ceived bilateral mandibular bone anchors at the time of zygomatic anchor 249 Temporary Skeletal Anchorage placement. The mean age of this group at the time of TSAD placement was 23.4 years, with a range of 10.6 to 44.4 years. Bollard anchors (Sur- gitec, Bruges, Belgium) were used exclusively, with two or three fixation screws in each anchor determined by the local bone morphology. All pa- tients were treated under conscious sedation. The procedures were com- pleted in an outpatient setting at the UNC School of Dentistry Department of Oral Surgery by seven different surgeons. Miniplates were loaded ap- proximately three weeks after surgery. Patient responses to the questions in the sections of the question- naire addressing general activity, oral function and symptoms such as swelling and bruising were scored on a scale of one (no trouble) to five (lots of trouble); responses to the questions in the sections addressing dis- comfort and pain were scored on a scale of one (no discomfort) to seven (worst discomfort imaginable). For questions that used the scale of one to five, substantial interference was defined as a four or five response. For questions that used the scale of one to seven, substantial interference was defined as a response offive to seven. Comparisons of substantial interfer- ence were made from questionnaires completed on days one through 14 and on day 21. Median-day-to-recovery was interpreted as the first day when 50% of the respondents reported little or no problem (a response of one or two). For calculations of median-day-to-recovery, questionnaires from days 1 to 90 were used for the osteotomy group and questionnaires from days 1 to 14 and day 21 were used for the TSAD group. In each of Figures 1, 2 and 3, the percent of patients who reported substantial inter- ference in each category is plotted by day (upper figure) and the distribu- tion of median-day-to-recovery is shown in quartiles (lower figure) for both the osteotomy and the TSAD groups. General Activity The responses in the area of general activity were considerably different between the maxillary osteotomy group and the TSAD group, but both groups reported substantial interference due to the surgical procedure in their routine, social and recreational activities (Fig. 1). More than 50% of the patients in the maxillary osteotomy group were not able to resume their daily routine for nearly a week following surgery. However, less than 10% of the patients in the skeletal anchorage group reported substantial interference in their daily routine, and this interference only lasted from post-Surgery day one to post-Surgery day four. 250 Silcox et al. Substantial Interference in General Activity | Days ---E--- Regular Routine - - - - Social Life —A- Recreation Time to Recovery in General Activity 75th 9% 60 - H Median 25th 96 50 - 40 - 30 - # 20 – o Fl E. Regular Routine Social Life Recreation [] Skeletal Anchorage (SA) Maxillary Osteotomy (MO) Figure 1. Top: Percent of respondents in the skeletal anchor- age (SA) and the maxillary osteotomy groups (MO) who re- ported substantial interference (a response of 4 or 5) in three areas of general activity. Bottom: Descriptive statistics for days to recovery (a response of 1 or 2) in general activity for both groups. 251 Temporary Skeletal Anchorage Oral Function All respondents in both groups reported substantial interference with normal chewing and most reported some difficulty eating and open- ing their mouth immediately following the surgical procedure. More than 60% of the osteotomy group reported substantial interference in eating over the entire 21 days recorded and more than 70% of the group also ex- perienced considerable difficulty chewing throughout the time period. A minority of the skeletal anchorage group reported substantial interference in eating and chewing that persisted for only five days or less following the surgical event (Fig. 2). In the areas of eating, chewing and opening, the median-day-to-recovery for the maxillary osteotomy group was at least six times greater than that of the TSAD group (Fig. 2). Pain and other Symptoms Patients in both groups reported substantial pain and swelling re- lated to their respective surgical procedures. Nearly 5% of respondents in the maxillary osteotomy group reported that they experienced substantial pain over the 21 days following surgery, while no patients in the TSAD group reported substantial pain beyond day seven. Patients in the oste- otomy group reported substantial problems with bleeding, while no pa- tients in the skeletal anchorage group reported any such problems. At some point after surgery, the majority of both groups reported substantial swelling (Fig. 3), but this generally subsided prior to day four in the TSAD group and day 12 in the osteotomy group (Fig. 3). COSTS ASSOCIATED WITH SURGERY In comparing treatment options for open-bite correction, it is im- portant to consider the difference in costs to patients both in time and money. Due to the relative novelty of using temporary skeletal anchorage devices in orthodontics, little data have been published that document the cost in time or money of using such devices. The cost involved in or- thognathic surgical treatment, on the other hand, has been examined more extensively. Although most available data are related to the increase in hospital charges associated with orthognathic surgery (Lombardo et al., 1994), there are some published data that quantify the costs of surgical- orthodontic treatment (Dolan and White, 1996; Kumar et al., 2006). Even though surgical costs vary according to demographics and provider, it is clear that surgical correction of open bite often constitutes the most costly orthognathic treatment (Panula et al., 2002). 252 Silcox et al. Substantial Interference in Oral Function 100- 1 sº. 80 - K--. - ``....... MO - - G--... - - *- "------...T * - - # - *- - “E. --> .º. 60– * - -- * - - - - ºv) - * -. 's R. “n E º $2 º ſl. i i i 7 14 21 Days ---E--- Opening -- *-- Eating —A— Chewing Time to Recovery in Oral Function 60 - 75th 96 - Hº 25th.9% 40 - 30 — # 10 – - E. E! | | T. Eating Chewing Opening [] Skeletal Anchorage (SA) [] Maxillary Osteotomy (Mo) Figure 2. Top: Percent of respondents in the skeletal anchor- age (SA) and the maxillary osteotomy groups (MO) who re- ported substantial interference (a response of 4 or 5) in the three designated components of oral function. Bottom: De- Scriptive statistics for days to recovery (response of 1 or 2) in the three components of oral function for both groups. 253 Temporary Skeletal Anchorage Substantial Interference in Other Symptoms | Days ---E--- Bleeding —A– Swelling - -- Pain Time to Recovery in Oral Function 60 - 75th 96 - - H Median - 25th9% 50 - 40 - 30 — # 20 - 10 – E- E. E. 0 Eating Chewing Opening [] Skeletal Anchorage (SA) Maxillary Osteotomy (MO) Figure 3. Top: Percent of respondents in the skeletal anchor- age and maxillary Osteotomy groups who reported Substantial interference in bleeding (a response of 4 or 5), swelling (a re- sponse of 4 or 5) and pain (a response of 5 to 7). Bottom: De- scriptive statistics for days to recovery (a response of 1 or 2) in swelling, bleeding and pain for both groups. 254 Silcox et al. Data were obtained from the records of two consecutively-treated patient groups at the UNC Department of Orthodontics. Group I consisted of seven patients who received a maxillary LeFort I osteotomy in one, two, or three segments with no other surgical procedure. All patients were treated as in-patients in a hospital setting. Group II consisted of ten pa- tients treated with bilateral zygomatic modified miniplates (TSAD) as part of their orthodontic treatment plan. All patients were treated in an out-pa- tient clinical setting. Accounting records, billing statements and surgical notes were collected from the UNC Hospital and the School of Dentistry for each subject. Patient costs associated with radiographs, surgeon and anesthesiologist fees, anesthesia/sedation services, operating room servic- es, hardware (fixation plates/screws), recovery room and private hospital room Services, lab/pathology services, and the pharmacy were recorded. Patient time associated with pre-operative clinic visits, time in the operat- ing and recovery rooms, overnight hospital stays, postoperative visits, and placement or removal of hardware also was recorded. Median patient cost and time were calculated. When all variables were considered, the median total Surgical cost Was approximately 12 times higher than the median total cost Sustained by the group treated with skeletal anchorage ($23,071 and $1,925, respective- ly). A summary of the patient costs associated with maxillary osteotomy and temporary skeletal anchorage is given in Table 1. The median patient time associated with a maxillary Osteotomy procedure was again found to be nearly 12 times greater than that required for the temporary skeletal anchorage group (36.1 hours and 3.00 hours, respectively). The data are summarized in Table 2. Table 1. Patient-incurred surgical costs associated with open-bite correction us- ing maxillary LeFort osteotomy and miniplate temporary skeletal anchorage. Maxillary Osteotomy (n=7) TSAD (n=10) Median Range Median Range Pre-Op Radiographs $364 $364 - $610 $241 $123 - $241 Surgeon's Fee* $6500 $4250 - $6700 $1040 $960 - $1040 Anesthesiologist Fee $800 $800 - $800 $0 $0 Anesthesia/Sedation $2,439 $1643 - $2.472 $315 $315 - $630 Operating Room Services $6,236 $5289 - $7654 $0 $0 Hardware (fixation plates/screws) $4,975 $3497 - $8695 $352 $248 - $456 Recovery Room $771 $743 - $825 $0 $0 Private Room $900 $0 - $1800 $0 $0 Lab/Path $121 $99 - $184 $0 $0 Pharmacy $1,241 $1104 - 1980 $61 $0 - $115 Total Surgical Cost $23,071 $21,508 - $25,897 $1,925 $1551 - $2492 *Surgical placement and removal included in TSAD figures. 255 Temporary Skeletal Anchorage Table 2. Patient hours associated with surgery for open-bite correction using maxillary LeFort I osteotomy and mini-plate temporary skeletal anchorage. Maxillary Osteotomy (n=7) TSAD (n=10) Median (hrs) Range Median (hrs) Range Pre-Op Consults 0.6 0.5 - 1 0.5 0.5 - 0.5 Post-Op Consults 2.4 2.0 - 2.5 0.5 0.5 - 0.5 Total Surgical Suite/OR Time 4.5 2.5 - 5.5 1.0 1.0 - 1.0 TSAD Surgical Removal N/A N/A 1.0 1.0 - 1.0 Recovery Room 1.5 1.5 - 2.5 0.0 Private Room (overnight stays) 24.0 0 - 48 0.0 --~~ Total Time Assoc w/Sx (hours) 33.2 10 - 57 hours 3.0 3.0 For many patients, the cost and recovery time associated with or- thognathic procedures are serious considerations. The patient in Figure 4 was referred for treatment with a maxillary LeFort osteotomy for her chief complaint of TMD secondary to an open bite. Before initiating treatment, the patient discussed the surgical procedure and recovery period with an- other patient who had experienced a maxillary LeFort osteotomy. She made the decision to undergo the then novel approach of treatment using zygomatic temporary skeletal anchorage to intrude the posterior teeth and close the open bite rather than the initially proposed orthognathic surgi- cal treatment approach. Bilateral zygomatic miniplates were placed and maintained for approximately 22 months. Intrusion of the posterior teeth primarily was achieved using elastic thread attached from the anchor to the upper archwire after bonding only upper canine to second molar bi- laterally. A transpalatal arch placed on the upper first molars was used to resist facial tipping of the posterior teeth. Only after a proper overbite was achieved were the maxillary incisors and lower teeth bonded for final de- tailing. Total treatment time was 26 months and the patient was reported to be very satisfied with her decision not to undergo orthognathic Surgery. Final photos taken on the day of debonding are shown in Figure 5, as are the one-year retention records. Both the patient and doctor were pleased overall with the outcome, and the occlusion has remained stable with no return of TMD symptoms. Structural treatment results are illustrated in Figure 6 with the superimposition of the initial and one year post-treat- ment cephalometric tracings. In all areas investigated, the cost, treatment time and recovery difficulties associated with surgery for open-bite correction were con- siderably greater for the maxillary osteotomy group than for the skeletal anchorage group. Although recovery data associated with surgical re- moval of temporary skeletal anchorage were not included, it has been Our 256 Silcox et al. Figure 4. Pretreatment records of a 27-year-old female with anterior open bite. Zygomatic miniplates were used to intrude the posterior teeth. Total treatment time was 26 months. Figure 5. Top: Day of appliance removal; proper overbite was achieved. Bottom: One-year retention records; overbite has remained closed. experience that the recovery and sequelae associated with removal are considerably milder than that of TSAD placement. These data do not imply that temporary skeletal anchorage is suit- able treatment for all open-bite patients. Each patient must be evaluated individually to determine what the best mode of treatment is. Although clinical trials and long-term follow-up studies of open-bite patients treated With TSADs currently are lacking in the literature, they will be required to ensure predictability, quality and stability of this type of treatment. If the treatment of open bite with temporary skeletal anchorage is shown to be as effective and stable as maxillary osteotomy, many patients may benefit from this less costly, less invasive, and less debilitating approach. 257 Temporary Skeletal Anchorage - - - - Initial - 1-year Post-Treatment Figure 6: Superimposition of initial and one-year post-treat- ment cephalometric tracings shows intrusion of maxillary mo- lars with a counter-clockwise rotation of the mandible. REFERENCES Bailey LJ, Phillips C, Proffit WR, Turvey TA, Stability following superior repositioning of the maxilla by LeFort I osteotomy: Five-year follow- up. Int J Adult Orthodon Orthognath Surg 1994;9:163–173. 258 Silcox et al. Bell WH, McBride KL. Correction of the long face syndrome by LeFort I osteotomy. A report on some new technical modifications and treat- ment results. Oral Surg Oral Med Oral Path 1977:44:493-520. Buchter A, Wiechmann D, Gaertner C, Hendrik M, Vogeler M, Weismann HP, Piffko J, Meyer U. 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The rotation of the mandible resulting from growth: Its impli- cations in orthodontic treatment. Angle Orthod 1965:35:36-50. Sherwood KH, Burch JG, Thompson WJ. Closing anterior open bites by intruding molars with titanium miniplate anchorage. Am J Orthod Dentofacial Orthop 2002; 122:593-600. Sugawara J, Baik UB, Umemori M., Takahashi I, Nagasaka H, Kawamura H, Mitani H. Treatment and post-treatment dentoalveolar changes fol- lowing intrusion of mandibular molars with application of a skeletal anchorage system (SAS) for open bite correction. Int J Adult Orthodon Orthognath Surg 2002; 17:243-253. Swinnen K, Politis C, Willems G, De Bruyne I, Fieuws S, Heidbuchel K, Van Erum R, Verdonck A, Carels C. Skeletal and dentoalveolar stability after surgical-orthodontic treatment of anterior open bite: A retrospective study. Eur J Orthod 2001:23:547-557. Umemori M., Sugawara J, Mitani H, Nagasaka H, Kawamura H. Skeletal anchorage system for open-bite correction. Am J Orthod Dentofacial Orthop 1999; 115:166-174. Williams RW, Travess HC, Williams AC. Patients’ experiences after un- dergoing orthognathic surgery at NHS hospitals in the south west of England. Br J Oral Maxillofac Surg 2004:42:419–431. Woodside D, Aronson L. Progressive increase in lower anterior face height and the use of posterior occlusal bite-blocks in this management. In: Graber L, ed. Orthodontics: State of the Art, Essence of the Science. St. Louis, Mosby, 1997. 261 TREATMENT OF THE CANTED OCCLUSAL PLANE George Anka Duane Grummons Canted occlusal plane treatment has long been a challenge for orthodon- tists. Successful treatment can improve oral function, self-esteem and general quality of life for patients. The recent development of temporary anchorage devices (TADs) offers the possibility of achieving such im- provements by producing better symmetry without surgery. The applica- tion of this technique and its attendant devices is the topic of this chapter. This preliminary report of a method that further refines current techniques for the correction of occlusal plane discrepancies includes discussions of both the concept of treatment in growing and nongrowing patients and actual case histories (Caruso and Rungcharasseung, 2004; Devincenzo, 2006a,b). Facial asymmetry, including a tilted cant of the occlusal plane, is common in orthodontic patients. It is important, therefore, to diagnose facial asymmetry and then integrate its correction into routine orthodon- tic treatment, if possible. In order to provide our patients with the best facial form and morphology, we first must understand the etiology of an individual patient’s skeletal pattern; for example, does the patient have a dolichofacial or brachyfacial pattern? We also must understand the degree of difficulty of specific treatment regimens. In the past, we seldom have questioned whether a brachyfacial skeletal pattern could be modified to become less brachyfacial or whether the vertical growth direction in a pa- tient with a dolichofacial skeletal pattern could be decreased by the time adulthood is reached. The inclusion of the TAD in orthodontic treatment protocols can improve the capability of treating these conditions resulting in enhanced oral function, optimal facial symmetry and better orthodontic treatment results. The TAD is a device that temporarily is fixed to bone for the purpose of enhancing orthodontic anchorage to allow the clinician to control tooth movement in three dimensions (Carano et al., 2005) and that subsequently is removed after use. In this chapter we will look pri- marily at how the TAD can control and influence vertical tooth move- ment as it relates to treatment of the canted occlusal plane, i.e., how it 263 Canted Occlusal Plane enables the clinician to control vertical growth in such a way as to influ- ence the height of the alveolar process through alveolar modification. To correct facial asymmetries in adult patients, the treatment of choice typically is surgery. However, because it appears that nonsurgical treatment of facial asymmetry is most successful in patients who are still growing, we believe that this new technique will be most useful for these patients (McNamara and Brudon, 2001; Grummons and Ricketts, 2004). The clinical use of this technique has just begun; therefore, we need longitudinal studies to prove its long-term stability and value. How- ever, the present clinical findings are promising. This technique provides a practical approach to detecting and modifying occlusal plane cant asym- metry. By first using the frontal analysis of Grummons and Ricketts to de- fine the specific region or quadrant that contains the problem and compar- ing the results of this analysis to our clinical evaluation, we can correctly choose the region to be effectively treated. Currently in young patients, asymmetry is treated using a fixed bite plate to increase the vertical dimension and to relieve interferences that can be best cleared with fluoride releasing ionomer composites. These posterior composite bite lifters can be placed either on the maxillary or mandibular posterior teeth and are described as “turbo” (Grummons, 2006) or anterior fixed bite plates (Anka, 2004). This technique is not related to the TAD and will not be described in further detail in this paper. In the non-growing patient, the strategy and focus includes all four quadrants of the posterior alveolar bone in order to correct the asymmetry with less effect or burden on the temporomandibular joints. The most im- portant factor in determining where the TAD should be implanted is the amount of interradicular space available. EXAMINATION AND EVALUATION OF OCCLUSAL PLANE ASYMMETRY Evaluation of facial asymmetry is performed using the Ricketts and Grummons frontal cephalometric analyses method (Fig. 1; Grummons and Rickets, 2004; Ricketts and Grummons, 2004; Grummons, 2006). This method compares right and left facial components to determine facial asymmetry. The patient is seated with the interpupillary plane horizontal to the floor. The use of dental floss on the midface is a simple way to create a vertical line relating the upper facial third at the crista galli (Cg) area and soft-tissue nasion (Na) region at the surface of the skin between the eye- 264 Anka and Grummons brows to the inferior part of the nose (subnasale) that represents the an- terior nasal spine (ANS) point. This reference line helps the clinician de- termine whether there is any mandibular shift or midline deviation of the maxillary teeth relative to the facial midline or the mandibular dental mid- line. A frontal clear “T” template also is a good tool for determining which facial component is deviated (Grummons and Ricketts, 2004). Facial asymmetry involves both the horizontal and vertical aspects of the face; therefore, vertical and horizontal measurements are made so that the clinician can compare both the vertical and horizontal quadrants of the face. The results of such measurements can be compared to patient photographs and frontal cephalometric findings. The lateral aspects of asymmetry may affect the vertical asymmetry and vice versa, Such as in a posterior unilateral crossbite. In this kind of case, the lateral transverse as- pect should be corrected to effectively help correct the vertical problem. Figure 1. Grummons simplified frontal analysis. 265 Canted Occlusal Plane Model Analysis The accuracy of patient casts mounted on an articulator depends on the location of the porions. When the porions are not symmetrical, the anterior-posterior and vertical positionings are affected. Therefore, the facebow transfer and the mounted models may not represent the true Frankfort Plane as an area that is normal and to which other landmarks should be compared. However, models do permit good observation of in- terarch interferences, spacial relationships between the upper and lower teeth, and relationships that can be reproduced outside of the mouth. Centric relations and centric occlusal differences influence the treatment plan. A unilateral crossbite of the posterior region will tip the occlusal plane on one side. A removable bite plate can be used to estimate how the mandible will posture and relocate and what its optimal position at rest will be. A fixed posterior bite plate can be used instead of a remov- able appliance (Fig. 2; Anka, 2004) while also correcting the transverse problem (Grummons, 2001a,b). Correcting the vertical alveolar height with the TAD is the next step. It is advisable to reduce the fixed bite plate gradually as the alveolar bone is corrected and the asymmetry is lessened. In addition, it is useful to know the width of the mandibular molars when planning treatment such as uprighting mandibular molars. It is advisable to make the mandibular arch the target arch (Grummons and Ricketts, 2004), as the width of the maxilla then can be adjusted to the width of the mandible. The transverse problem definitely affects the vertical problem; therefore, arch width and asymmetric relationships should be examined carefully. An anterior fixed bite plate can be used to continue monitoring the centric relationship as well as to correct overjet and overbite (Figs. 3 and 4). Radiography Measurements taken from both lateral and frontal cephalograms are necessary when diagnosing facial asymmetry. These data, combined with clinical evaluation recordings, will determine the treatment plan. The panoramic radiograph is a simple radiograph containing information about the ramus, condyle, and relationships between the upper and lower teeth (when taken in ICP). The overall condition of the nasal floor and its relation to the teeth, especially the posterior teeth, is important as the TAD could penetrate the nasal cavity in an inferior portion of the maxil- lary sinus. While this not a contraindication for treatment using the TAD, avoidance of such an incident is important because it could cause chronic sinusitis or cause chronic sinusitis to become acute. The panoramic radi- 266 Anka and Grummons ograph shows the interradicular space available, necessary information when choosing the TAD placement. Knowing the location of all first mo- lars and canines is very important as it allows comparison of the original and post-treatment locations. We have chosen to use the reference Na-ANS (midsagittal plane) as described earlier. The line that extends to the lower border of the man- dible provides information about the location of Menton (ME). We first determine the starting location from the maxillary jugal processes, JR to JL. We then analyze its location relative to a line perpendicular to the Na-ANS line and determine whether it is tilted. The area of JR-JL is not influenced by the method described in this chapter, but it is important to know whether there is a problem in this region initially. Next we analyze the maxillary occlusal plane. This is the area that treatment will influence significantly. Our method can decrease or increase the vertical height of the adjacent alveolar bone, with a maximum of 3 mm impaction potential, and 1 to 2 mm possible in extrusion. Mandibular occlusal plane maneuvering is less effective com- pared to that of the maxillae. TAD placement is restricted to the lower buccal side of the attached gingivae, the vertical dimension of which is limited. At present, we are able to intrude the lower occlusal plane (< 2 mm) less than the upper. However, intrusion of up to 3 mm for the lower molars can be accomplished effectively and with relative ease using a skeletal anchorage device (SAS), which is a mini-plate type of TAD, with a relapse of 25% (Sugawara and Baik, 2002). With this limitation in mind, we must choose a realistic treatment plan based on our observations of the problem areas. The importance of frontal cephalometrics has been explained by Ricketts and other researchers (Hilgers, 1988; McNamara and Brudon, 2001). In spite of this, little has been done with the information available from frontal cephalometrics. Lateral cephalograms have been the more popular choice, possibly because clinical applications for frontal cephalo- metrics were limited. With the emergence of the TAD in clinical practice, however, the use of frontal cephalometrics should become more wide- Spread. MECHANICS RELATED TO MANAGEMENT OF THE CANTED OCCLUSAL PLANE IN THE MAXILLA: TRANSPALATAL ARCH PLUS HOOKS The transpalatal arch (TPA) plus hooks is very effective in con- trolling the sagittal direction of molars and premolars and the mesial- 267 Canted Occlusal Plane distal and/or intrusion-extrusion molar movements (Kyung et al., 2003; Lin et al., 2006; Park, 2006). The transpalatal arch consists of a lingual arch and a transpalatal bar the design of which is specific to treatment requirements for the posterior teeth. Figure 2 demonstrates distalization of molars combined with slight intrusion, a typical Class II, division I ap- plication. The hooks were attached on the cervical area of the lingual arch, and the TADs were placed in the lingual alveolar process about 10 mm below the margin of the cervical gingival line of interradicular bone. This area was chosen as the safest area for TAD placement because the dis- tance between the root of the second premolar and the lingual root of the first molar provided the most space. This location allowed for the needed distalization of molars without requiring reimplantation and reduced the possibility of collision between the TAD and the roots during tooth move- ment. Extrusion and intrusion requirements determine the location of the hooks and the direction of force from the elastic chains. The hooks can be placed anywhere on the vertical portion of the transpalatal wire. The higher the hooks are placed on the palate, the more extrusive is the force; the opposite creates an intrusive force. The direction of the elastic chain provides a combination of distalization and intrusion or distalization and extrusion. Figure 2. A TPA-plus-hooks configuration. The posterior fixed bite plate, made from blue glass ionomer cement, is used to determine centric relation in a patient with a mandibular shift. The bite plate lessens the interference with the movement of the posterior teeth and prevents cuspal abrasion during treatment. 268 Anka and Grummons Optimal location of the TAD is 3 to 4 mm from the gingival cervi- cal line up to about a 12 mm distance. This distance varies from case to case and is based on the amount of bone within the alveolar process, which can be determined with either a panoramic or simple dental X-ray film. There is no doubt, however, that 3D CT imaging provides much better data. The midpalatal area is the most superior area that can be used when simple intrusion is the primary objective, as this involves a direct force from the palatal alveolar location to the first molar or to a point in front of the molar on the lingual aspect (Fig. 2). A final consideration is that the gingiva in the palatal region is better attached than in the buccal regions. Thus, the success rate is greater when implantation occurs in the palate. It is, therefore, the preferred site for implantation (Kyung et al., 2003; Park, 2006; Youn, 2006). On the left side of the TAD, an elastic chain is attached to the lin- gual arch in front of the first molar and a second elastic chain is attached to the transpalatal bar. These mechanics provide intrusion and distalization of the left molar. On the right side, only the distalization effect is desired. Extrusion of both molars can be done with attachment to the omega loop area of the transpalatal bar, as seen in Figure 3. Figure 3. The anterior fixed bite plate is placed on the lingual side of the central incisors. Both intrusion and distalization Oc- cur on the left side, while only distalization occurs on the right side. Figure 4 shows the attachment of both TADs on the palatal al- Veolar side to the omega loop of the transpalatal bar, the result of which is the extrusion of the molars with some distalization. For pure extrusion 269 Canted Occlusal Plane of the molars, the TPA can be constructed with finger springs soldered to the band of the first molar and simply connected to the TAD to extrude the molar (Fig. 5). In the case seen in Figure 5, extrusion of the left and/or right molars can be controlled easily to adjust to the specific requirements needed to correct the occlusal plane asymmetry. - Figure 5. Pure extrusion of the posterior molars by means of finger springs. 270 Anka and Grummons Asymmetry in the anterior region can be handled easily on the buccal side. Such intrusion of the anterior region requires placement of a TAD on the buccal area of the incisors, canine or premolar area, depending on the degree to which the occlusal plane is canted, on the Smile dynamics, on the extent of gingival exposure, etc. Figure 6 illustrates intrusion of the four maxillary incisors, with the forces applied on the right and left sides precisely controlled. Intrusion force should not exceed 200 g per side for the four incisors, because intrusion movement will compress the periodontal membrane in, which lessens the capillary blood supply that may cause the teeth to be prone to root resorption. Unilateral intrusion can be provided by engaging on one side only, but for effectiveness the placement of the TAD should be in a more anterior region such as between the canine and lateral. The extrusion of the one area can be achieved either with a finger spring (Figs. 4 and 14) or with an extension finger open-coil spring, which works for mesializa- tion, distalization and/or extrusion, as seen in Figure 7. In Figure 7, the extension compressed open-coil spring is made of a 0.028 round wire and has a coil spring that can be activated to propel and extrude the canine as the spring elongates. The results are extrusion and mesialization of the right canine and adjacent teeth. Figure 6. Intrusion of the four incisors with slight distaliza- tion. 271 Canted Occlusal Plane Figure 7. An open-coil finger spring works for extrusion and mesialization of the canine in a lateral open bite case. MAXILLARY EXPANSION The transverse problem is related closely to the vertical problem (Hilgers, 1988; Grummons and Ricketts, 2004; Park, 2005). Maxillary ex- pansion can be generated by: 1. placing a Hyrax rapid expansion device on the maxillary first molars on both sides of the maxillary alveolar process; 2. placing a TAD directly on both sides of the alveolar re- gions and producing no tooth-borne anchorage; or 3. using a combination of the two methods, i.e., one side having tooth-borne anchorage and the other side having alveolar bone anchorage. The option of choice is based necessarily on where we need to expand. For example, to have less tip effect on the maxillary molar and directly expand the upper alveolar region, the preferred method with the TAD is seen in Figures 8 through 10. When unilateral expansion is desired as in a poste- rior crossbite on one side, the preferred method is to have TAD anchorage 272 Anka and Grummons on the non-crossbite side and on the crossbite side to have the appliance connected directly to the teeth, as seen in Figures 11 and 12. * * , it a Figure 8. Two TADs are placed on each side of the alveolar pal- atal process, on which the Hyrax with two caps is cemented. Figure 9. The patient seen in Figure 8 before bone-borne ex- pansion occurs. 273 Canted Occlusal Plane Figure 10. The result of bone-borne expansion. Note the correc- tion of the cross bite with no effect on the teeth. Figure 11. The unilateral Hyrax expander. After the patient has worn a bite plate for two to three weeks, the clinician must decide whether to use removable or fixed bite lifters (com- posites). We use the latter most often in our office, i.e., palatal alveolar expansion with a Hyrax-type expansion system. Rapid expansion usually is our choice; it requires only one or two turns per day to obtain treatment 274 Anka and Grummons objectives, including transverse overcorrection (20–30%), and it provides optimal stability. wº - Figure 12. Intraoral view of the one-sided Hyrax expander. MANDIBULAR INTRUSION In non-growing patients for whom adaptation of the condylar pro- CeSS and TMJ components is limited, it is necessary that the mandibular posterior teeth and alveolar height follow the same pattern of movement as their maxillary counterparts on the same side. For example, if treatment includes extrusion of the posterior maxilla, it also must include intrusion On the same side of the mandible (Bae and Kyung, 2006). The intrusion technique in the mandible has been demonstrated by Sugawara and co-workers, with the plate type the most successful (Suga- Wara and Baik, 2002). However, it is limited with the use of the screw type TAD since we only can work in the unattached gingival area. However, improvement in this area will come soon so that we can achieve intrusion effectively in the posterior region of the mandible. With the screw-type TAD, we also can achieve success (Carano et al., 2005; Bae et al., 2006; Lin, 2006). Figure 13 shows an elastic attached to the TAD between the premolar and the molar. The recommended force is less than 200 g. A lin- gual arch is necessary to prevent tipping of the posterior teeth. 275 Canted Occlusal Plane -- Figure 13. Intrusion of the posterior teeth with a triangle elastic attached directly to the TAD. MANDIBULAR EXTRUSION We have adopted the technique of extrusion in the mandible as advocated by Park (personal communication; Fig. 14). Both intrusion and extrusion of the mandibular posterior teeth require a lingual arch to sta- bilize the posterior teeth and prevent their tipping toward the direction from which the force is applied. The extrusion force should be about 200 g in order to withstand the bite force when extruding a group of posterior teeth. MIDLINE ASYMMETRY Asymmetry influencing the midline can be a challenge when cor- recting a canted occlusal plane in that the misfit of even one tooth to its op- posite will affect the entire occlusal table and the two arches even if they function well. Cuspal interferences often will affect the lower jaw posture and the TMJ condylar position. This situation also affects the complete articulation and masticatory system of the patient. Midline correction is simpler if there is space available such as that provided in an extraction treatment plan. However, nonextraction patients (with the exception of third molar extractions) are increasing in number, and it is more difficult to correct midline asymmetry in these cases. The TAD can be helpful in resolving clinical anchorage problems, enabling molar distalization to become a routine procedure. 276 Anka and Grummons Figure 14. Extrusion of the posterior teeth using a finger spring. An asymmetrical midline can be due to a canted occlusal prob- lem. It also can be caused by treatment efforts to correct a canted occlusal table. As the arch of the teeth moves, the midline moves as well, creating an asymmetry of the midlines that probably was not asymmetric initially (Fig. 15). This phenomenon happens because the effect of our mechan- ics is limited to the alveolar bone area and not the basal bone itself. The Center of resistance on the maxilla is on the mid-palate or above (the sinus itself); we must strive to correct the occlusal plane in combination with lateral movement of the entire maxilla to the right side in this example. In addition, there are some treatment choices, although very limited ones, that can be used on the lower to compensate (note the midline correction of the mandible). Figure 15. Before (left) and after (right) treatment to correct the canted Occlusal plane. Note the change in midline symmetry. 277 Canted Occlusal Plane Correcting the midline asymmetry includes the movement of all teeth within the arch from one side to the other (Youn, 2006). It may involve correcting one arch or both arches. The choice depends on the clinical examination of the patient and the results of the frontal analysis. Maxillary midline correction is easier than correction of the mandibular midline. The reason for this is that the maxillary palatal bone provides a large area in which to place TAD devices and attachments. MAXILLARY MIDLINE CORRECTION The maxillary midline as well as the mandibular midline will have to move distally on one side and mesially on the other side as we relocate the whole dentition in one direction. This unidirectional movement can be achieved with indirect force applications. A simple method for applying such a force is the use of a hook soldered onto the band of a molar; usually the first molar is preferred (Figs. 16 and 17). This can be accomplished on the palatal side or the buccal side, depending on the placement of the TAD itself. Palatal placement allows more range of movement and requires less frequent or no reimplantation. Although buccal placement is more popu- lar at present, as the teeth move toward the TAD, collision between the teeth approaching the TAD can cause damage to the periodontal mem- brane and even the cementum itself, the result of which potentially could be ankylosis. Most of the time, this will not cause fatal harm to the tooth if recognized early. In the premolar area and anterior regions (incisors), buccal placement still is the location of choice. Patients generally are more comfortable having a TAD placed in the buccal side rather than in the anterior maxillary lingual side area. Speech disturbance and irritation of the tongue are the main reasons to avoid placement in this area. The least objectionable and most accepted placement is in the palatal alveolar bone area. Placement in the upper retromolar pad is a good choice, although the risk of TAD fracture during screw removal must be considered. The con- sequences of such problems are less when TAD placement is in the palatal alveolar bone compared to placement in other areas of the palate. The simplest design for distalization includes an extended arm. The length of the arm can be adjusted to the requirement of the elastic to be used for the power source (Fig. 18). This method is effective for short distance movement, but for longer distances, rotation to the lingual side can occur unless the main archwire is close to a full slot size wire. The 278 Anka and Grummons other technique that can be effective is the use of a transpalatal bar and hooks, which will maintain the width of the molars as movement occurs. In the anterior region an auxiliary open-coil spring may be needed to pro- vide a distalization force (Fig. 19), which enhances the movement on the anterior buccal region, to the left in this case. Figure 16. When extended arms are used to distalize the mo- lars, a different amount of force can be applied to each side. Figure 17. Unidirectional movement: the left side of the arch will move distally and the right side will move mesially. 279 Canted Occlusal Plane Figure 18. Left: An extended arm of 0.036” stainless steel wire soldered to the molar band. Right: A palatal side extended arm on a dental cast. Figure 19. Left. This patient was treated with an open-coil finger spring with a 016 x 016 rectangular wire. Right: Patient at the end of treatment. MANDIBULAR MIDLINE CORRECTION In the mandible, the TAD is placed on the buccal area only be- cause lingual placement would irritate the tongue for most patients. Use of the extended arm is the most frequently used and the simplest device compared to other devices (Fig. 20A). The open-coil finger spring is high- ly adaptable to the curvature of the arch, but it needs modification on the main archwire to keep the device from flaring to the buccal side and irritat- ing the lower lip (Fig. 20B). Mesialization of molars in the mandible follows the same design as that used in the maxilla, i.e., with hooks soldered on the molars and con- nected to a TAD that is placed on the buccal alveolar bone, which usually located between the canine and premolar or between the second and first premolar (Fig. 200). Case 1 Case 1 involved a 13-year, 8-month-old female patient whose chief complaint was upper crowding. An intraoral examination showed 280 Anka and Grummons that the primary problem was the upper left lateral incisor that was in lingual version and other dental compensations. The mandible has shifted to the left; interferences of the upper left lateral against the lower incisors have lead to asymmetric mandibular body growth. Difficulty in chewing has also affected the maxilla as seen in Figure 21. The anteroposterior or frontal cephalogram tracing is shown on Figure 22. The frontal facial pho- tographs are seen in Figure 23. Figure 20. A: The extended arm was soldered to the first molar band. B: The Open-coil finger spring is used to correct midline. C. A hook was soldered to the buccal side of the first molar and connected with an elastic to the TAD. Figure 21. Case I initial intraoral photographs. Left. Frontal view. Right: Maxillary occlusal view. 281 Canted Occlusal Plane Figure 22. Case 1 initial frontal cephalogram. Figure 23. Case 1 initial facial frontal photographs. Treatment was comprised of fixed appliances; primary expan- sion with upper and lower archwires eliminated the crowding and interfer- ences. This expansion produced a slight bimaxillary protrusion and the need to retract the upper and lower arches using a TAD while controlling 282 Anka and Grummons Figure 25. Intrusion of the left molars from the buccal side. the maxillary occlusal plane with the TPA plus hooks (Fig. 24), with the left buccal side slightly intruded (Fig. 25). The patient was 16.3 years of age at the end of treatment. Ex- pansion and transverse appliance therapy (Grummons and Ricketts, 2004) improved the cant of occlusion significantly and optimized oral function for chewing, all of which resulted in a more aesthetically pleasing facial appearance (Figs. 26 to 28). 283 Canted Occlusal Plane Figure 26. Case 1 photographs taken at the end offixed-appliance treatment. Figure 27. Case 1 end-of-treatment frontal cephalogram. 284 Anka and Grummons Figure 28. Case 1 end-of-treatment frontal facial photographs. Case 2 The patient seen here is a 12-year-old male with a follicular cyst of the maxillary right second premolar area, a deviated midline and canted Occlusal plane and severe anterior crowding (Fig. 29). The masticatory function of the anterior and posterior teeth was poor due to transposition of the upper canine and lateral incisor (Fig. 30), with the occlusal plane tilted, the right side of the occlusal table is lower than the left side (Fig. 31). Treatment was initiated to remove the cyst and close the extraction site by moving the upper right posterior quadrant mesially and anteriorly. It is difficult to move molars anteriorly, especially when the occlusal plane is canted. For this purpose, an open-coil spring was designed to prevent further canting of the occlusal plane. Its use did not correct the occlusal plane cant completely because it was used only on one side (Fig. 32). Me- sialization of the molars was achieved with hooks welded onto the bands of the molars, as shown in Figure 33. 285 Canted Occlusal Plane Figure 29. Panoramic radiograph for Case 2. The follicular cyst was caused by the right second premolars. Figure 30. Initial frontal intraoral photograph (left) and occlusal view (right) for Case 2. * * - - Figure 31. Initial frontal cephalograph (left) and frontal facial photograph (right) for Case 2. 286 Anka and Grummons A skeletal anchorage system (SAS) was used to reinforce anchor- age. A TAD was placed between the upper right canine and first premolar to act with the finger coil-spring device as the main extrusion force. This treatment approach closed the tilted occlusal area of the right side, cor- rected the midline, and aligned the premolar and molar teeth mesially. A TAD was implanted on the palatal alveolar side to prevent rotation. Figure 32 illustrates the design of the molar hooks and Figure 33 illustrates the banded intraoral design. Treatment results are shown in Figures 34 to 36. Figure 32. The extension open-coil spring was tied to the TAD to ex- trude the the upper right canine and the surrounding teeth. Figure 33. The design of the hooks attached to the molar bands to mesialize the molars. Auxiliaries on the dental cast (left) and inside the mouth (right). Figure 34. Case 2 end-of-treatment intraoral photographs. 287 Canted Occlusal Plane Figure 35. Case 2 end-of-treatment panoramic radiograph. Figure 36. End-of-treatment frontal cephalogram and frontal facial pho- tograph for Case 2. Closure of the extraction sites is seen on the panoramic X-rays. The long distance movement of the molars eliminated the need for pros- thetic replacement since the space was closed. The molars have a Class II relationship and the third molar is becoming positioned occlusally. The fixed appliances were removed because the patient was concerned about the length of the treatment procedure and desired to be finished with fixed appliances. Case 3 The patient in Case 3 is a 16.2-year-old female with TMD symp- toms including reciprocal clicking on her right side; mandibular devia- tion to her right side upon opening and closing of the jaw; limited open- ing to 30 mm; masticatory muscles that were painful to palpation, espe- cially on the left and right lateral and medial pterygoid muscles. MRI 288 Anka and Grummons revealed an anterior disc displacement of the right condyle (Fig. 37). She underwent TMD splint therapy for one month, with fair-to-good results in dysfunction resolution. It is more difficult to correct the occlusal plane in the non-grow- ing patient. The occlusal plane can be corrected by influencing both upper and lower quadrants on one side, though most of the time we have to deal with all four quadrants simultaneously. The patient’s right molar was so carious that preservation of the tooth was difficult. Her dentist asked if we could move the second molar in such a way as to replace it. The AP (fron- tal cephalogram) and the pretreatment facial and intraoral photographs are shown in Figures 38 and 39. The patient had a Class I molar relationship with a Class III ten- dency on both sides. Cuspal interference on both second molars was caused by the upper second molar lingual cusps interfering during lateral excur- Sion. Treatment began with extraction of both upper second premolars. The lower right first molar and the lower left second premolar also were removed. A fixed bite plate was added on the upper first molar occlusal table to reduce interference and align the second molars (Fig. 40). Jº |Cºº - Il-2:00(&D º - - (-47.8.0.0. º lombined Aºy W:01.1% WL: 45.1% Fºllº MIL, Figure 37. MRI of the anterior disc displacement seen in Case 3. 289 Canted Occlusal Plane Figure 38. Initial frontal cephalogram and facial photograph for Case 3. Figure 39. Case 3 initial intraoral frontal and maxillary and mandibular oc- clusal view photographs. Treatment was continued with intrusion of the upper right quad- rant and extrusion of the lower right quadrant (Fig. 41). The location of the four TADs is seen in the panoramic view (Fig. 42). It was recom- 290 Anka and Grummons Figure 40. Case 3 extraction of the right first molar and left second premolar after fixed appliances (left). Extraction of both upper second premolars and placement of a bite plate on the upper first molars (right). Figure 41. Intrusion in the right quadrant (left) and extrusion in the left quadrant (right). Figure 42. Panoramic radiograph of Case 3 patient taken during treat- ment shows TAD placements. mended that the upper right third molar be extracted although the patient Was reluctant to have it removed. 291 Canted Occlusal Plane Figure 43. Case 3 frontal cephalogram and facial photograph taken during treat- ment after the occlusal cant was corrected. Figure 44. Intraoral occlusal photographs of the maxilla (left) and mandible (right) taken after the occlusal cant was corrected. Treatment resulted in the correction of the occlusal plane asym- metry to a large degree. The opening and closing movements of the jaw improved and showed no limitation. Clicking still was present, but there was no pain and no ongoing muscle tenderness. This patient will finish her treatment very soon (Figs. 43 and 44). CONCLUSIONS The application of indirect force when using TADs is a valuable treatment approach to correcting asymmetrical occlusal surfaces as it 292 Anka and Grummons allows the control and direction of the forces needed in three dimensions. We advocate using such devices as hooks, lingual arches plus hooks, ex- tension arms, and finger open-coil springs in concert with TADs as part of this new technique. Used together, these devices and TADs can help the clinician control the teeth and their occlusal plane as demonstrated in Cases 1, 2 and 3. A frontal cephalometric evaluation is a valuable tool in judging the level of difficulty in treating a specific canted occlusal plane and projecting the effectiveness of a given treatment plan. A treatment plan then can be established and applied to the canted occlusion to cor- rect the asymmetry and normalize function despite some dentoalveolar compensations. The AP Grummons simplified frontal analysis system used with TAD technology can quantify and locate the deviation and indicate in which direction the treatment should be directed to best improve the asym- metries. This new technique provides anchorage that was difficult to sup- ply in the past such as that needed to treat asymmetric vertical dimension discrepancies. However, screw-type TAD implantation to the attached gingival area of the alveolar bone has a relatively high failure rate when used in the mixed dentition of young patients, considering the rapid cell turnover that takes place (Roberts, 2000). At present, this treatment is lim- ited to patients who have a full dentition from first molar to contralateral first molar. The potential TAD patient should have completed the transi- tion from mixed to permanent dentition. The best result are achieved by using the frontal cephalogram combined with clinical observations to define the problem; by thoroughly evaluating the treatment options made available by using these new TAD techniques; and by understanding the treatment limitations. All of these factors will help produce a positive treatment outcome, i.e., the best pos- sible facial balance and symmetry, the result of which is a more attractive face and functional occlusion. REFERENCES Anka G. The management of noncompliance of Class II, division 1 ex- traction cases with jumping appliance forces DPR: A suggestion of the use of Gurin lock and anterior fixed bite plate. Orthodontia 2004; 1: 122–133. Bae S, Kyung H. Mandibular molar intrusion with miniscrew anchorage. J Clin Orthod 2006:40: 107-108. 293 Canted Occlusal Plane Carano A, Velo S, Leone P, Siciliani G. Clinical applications of the mini- screw anchorage system. J Clin Orthod 2005:39:9-24. Caruso J, Rungcharasseung K. A Practical Guide to the Use of Mini- screw Anchorage. Coeur D’Alene, 2006. Devincenzo J. A new non-surgical approach for treatment of extreme doli- chocephalic malocclusions. Part 1: Appliance design and mechano- therapy. J Clin Orthod 2006a:XL:161-169. Devincenzo J. A new non-surgical approach for treatment of extreme doli- chocephalic malocclusions. Part 2: Case selection and management. J Clin Orthod 2006b;XL:250-260. Grummons D. Nonextraction emphasis: Space gaining efficiencies. Part I: World J Orthod 2001a:2:21-32. Grummons D. Nonextraction emphasis: Space gaining efficiencies. Part II: World J Orthod 2001b;2:177-189. Grummons D. Frontal facial asymmetry information. Presented at the Am Assoc Orthod meeting, Las Vegas, May 2006. Grummons D, Ricketts R. Frontal cephalometrics: Practical applications. Part 2. World J Orthod 2004:99-119. Hilgers J. Bioprogressive simplified. J Clin Orthod 1988:12:48-69. Kyung S, Hong S, Park Y. Distalization of maxillary molars with midpala- tal miniscrew. J Clin Orthod 2003; 1:22-26. Lin J, Liou E, Yeh C. Intrusion of overerupted maxillary molars with mini- screw anchorage. J Clin Orthod 2006;XL:378-383. McNamara JA Jr, Brudon WL. Orthodontics and Dentofacial Orthope- dics. Ann Arbor, Needham Press, 2001. Park H. A miniscrew-assisted transpalatal arch for use in lingual orthodon- tics. J Clin Orthod 2006; XL:12-16. Park YC. Use of intrusion auxiliaries on the maxilla and extrusion auxilia- ries on the mandible to rectify occlusal plane canting and consequent correction of facial asymmetry. Korea Association of Orthodontics Meeting, November 2-3, 2005. Seoul, Korea. Personal communica- tion. Ricketts RM, Grummons D. Frontal cephalometrics: Practical applica- tions, Part 1. World J Orthod 2004;4:297-316. Roberts WE. Orthodontic anchorage with osseointegrated implants: Bone physiology, metabolism, and biomechanics. In: Higuchi KW, ed, Othodontic Application of Osseointegrated Implants. Illinois, Quin- tessence 2000:161-190. Sugawara J, Baik UB. Treatment and post-treatment dental alveolar changes following intrusion of mandibular molars with application 294 Anka and Grummons of a skeletal anchorage system (SAS) for open bite correction. Int J Adult Orthodont Orthognath Surg 2002; 17:243-253. Youn S. Midline correction with miniscrew anchorage and lingual appli- ance. J Clin Orthod 2006:40:314–322. 295 MICROIMPLANTS: LITTLE PARTNERS FOR BIG CHALLENGES Alfredo Alvarez Since the time of Angle, we have been learning and teaching students how to provide patients with as close to perfect results as possible. If we think about today’s beauty standards, perfect teeth are a must. So we focus on the perfect occlusion or in the current vernacular, a “10.” Adolescent patients who have had no previous orthodontic treat- ment and who have no history of skeletal or biomechanical limitations fulfill all of the requirements for idealistic treatment goals. For these pa- tients, we clinicians expect to obtain perfect treatment outcomes. But what about all of the patients who do not fit into the “perfect” category? In our daily practices, we often face a big gap between the results that we would like to obtain and those that we can obtain. Clinicians have believed that treatment for patients who have undergone orthodontic treatment that has failed, who present with complicated biomechanical and/or skeletal chal- lenges or who have poor dental histories must include surgery or goals that settle for less than perfect results. Anchorage limitation is a common factor in almost all of the scenarios described above. The application of microimplants, therefore, could be the key to finding treatment protocols that will achieve the perfect occlusion or a “10” for these patients. Clinicians will not have to struggle to achieve an occlusion that is only a “5” or “6.” MAXILLARY DISTALIZATION Upper molar distalization comes and goes from time to time. There have been various non-compliance devices used for distalizing up- per molars. What is true, however, is that intraoral anchorage can lead to mesial tipping of the anchor teeth if it is not applied properly (Fig. 1). Figure 2 illustrates a very simple distalization technique used on a patient who had undergone previous orthodontic treatment. Using one microimplant as anchorage, a nickel titanium open coil spring and a slid- ing hook, the ligature pulls the sliding hook toward the spring in order to apply distal forces to the molar. After a slight overcorrection, the spaces created were used to obtain a canine Class I occlusion and upper midline correction, which was the main objective of this re-treatment. 297 Microimplants: Partners for Challenges Figure 1. Notice the mesial tipping of the anchorage teeth. This is an extreme mesial tipping case, but for each mm of distalization, there is about 0.5 mm of mesial drift. Figure 2. Simple biomechanics were used to obtain a Class I occlusion in this re-treatment case. 298 Alvarez The next case is a typical “second hand” or re-treatment case. This female patient (M.D.) presented with a severe gummy Smile, four miss- ing bicuspids, a Class II occlusal relationship, and a bowing (i.e., a deep curve of Spee with incisal and canine retroclination) effect (Figs. 3-6). The patient did not want pictures taken at the beginning of treatment, so no pretreatment facial pictures are presented here. Figure 3. The arrow points to a color change that shows where the lip rested. The patient had a very noticeable gummy Smile. Figure 4. The patient had a full canine Class II occlusion with canine crown distal tipping and poor oral hygiene. Figure 5. Notice how close the canines and second premolar crowns are opposing a big gap between roots. 299 Microimplants: Partners for Challenges | Figure 6. Although there are many measurements that are important, the most important ones for this patient are the sagittal and vertical po- sitions of upper and lower incisors, i.e., upper incisor to the A-Po line, upper incisor to the A line, upper incisor exposure, and lower incisor extrusion. After convincing myself of the capabilities of microimplants for distalizing one or two molars, as seen in the previous case, I felt confident enough to try another approach. In this case I preferred to align and level prior to distalization (Fig. 7). 300 Alvarez Figure 7. NiTi 0.016”; upper archwire (0.022” slot); NiTi 0.018” reverse curve loop archwire. Once the aligning and leveling stage was completed and the full- size stainless steel archwire with crimpable hooks was in place, two mi- Croimplants were inserted between the second premolars and first molars, but closer to the molars. This procedure was performed in order to distal- ize the entire maxillary dentition from second molar to second molar at the Same time (Figs. 8-11). Figure. 8. Microimplants (Dentos SH 1413-06) were placed between the Second premolars and first molars with a 0.019 x 0.025” stainless steel ac- centuated curve of Spee upper archwire. The same size archwire was used in the lower arch with a reverse curve. 301 Microimplants: Partners for Challenges Figure 9. Note the small amount of composite resin placed over the mi- croimplant head. The resin keeps the spring from slipping and protects the patient’s soft tissue. Figure 10. The microimplants seem to move toward the second premolar because of the distal movement of the entire dentition. Figure 12. Patient M.D. at the end of treat- ment. She has a satisfactory tooth display. a slightly gummy Smile, which is reasonable at her age and her profile shows relaxed lips closing with no effort. 302 Alvarez Figure 11. The curve of the upper archwire improved the vertical dimension. As can be seen in the above figures, the treatment plan worked Well. There was en masse distal movement of the canines and molars, and the microimplant head appears to have moved toward the second pre- molar. In addition, there was improvement in the vertical plane of space due to an accentuated curve placed in the upper archwire that helped with torque control and intrusion. Placing this type of curve in the archwire usually burns a lot of anchorage, but this is not a problem when microim- plant screws are used. Figures 12 through 14 show the patient at the end of treatment. She has a nice smile and a beautiful tooth display. Good anterior guidance on the right side resulted in a Class I occlusion. The result on the left side is not perfect, but it is satisfactory, and the canine guidance worked nicely. The patient’s smile has improved greatly and seems less gummy, and her gingiva appears to be healthy. 303 Microimplants: Partners for Challenges Figure 13. There is a perfect Class I occlusion on right side and a less than perfect occlusion on the left side. Coincident midlines and nice archwire shape are visible in the occlusal views. Figure 14. This photograph with superimposed tracing shows the improvement in the measurements related to the mandibular and max- illary incisors at the end of treat- ment. Upper incisor to A-Po: 3.4 mm/26" Upper incisor to the A line: 0.5 mm Upper incisor exposure: 6 mm Lower incisor extrusion: 2.4 mm This case shows that the entire upper dentition can be moved dis- tally at the same time. It should be noted that the amount of distalization was small and the screws were about to come into contact with the second premolar roots. If the desired movement is larger, it may be necessary to remove the screws and place them distally. Miniplates might be even bet- ter for producing larger movements. The next case is another re-treatment case. The male patient (J.D.) presented with his four premolars extracted and, as with patient 304 Alvarez M.D., with the canines in a full Class II relationship. Absolute anchorage is a must in this case as well, but that is not all. Looking at the front intra- oral picture, a slight occlusal plane canting is noticeable. Figure 15. The microimplants (Dentos SH 1312-07) were placed at very dif- ferent heights in the upper dentition. The slight occlusal plane canting can be seen in the bottom image. The upper archwire was a 0.019° x 0.025” stainless steel wire with crimpable hooks. The lower archwire was the same size. Combining different types of pulls was the best solution for work- ing in both the vertical and sagittal planes of space at the same time. There Was no archwire bending, only biomechanics and absolute anchorage. In the sequence of photographs show in Figures 16 and 17, good retrusion is Seen with no anchorage loss. The canines are reaching a Class I occlusion. Meanwhile, and with no additional effort, the occlusal plane is being lev- eled (Figs. 18 and 19). Figure 16. The canines are moving toward a Class I occlusion, but the molars are still Class II. The lower arch is being leveled prior to beginning molar me- sial movement. 305 Microimplants: Partners for Challenges Figure 17. The canines are now in a Class I relationship and the molars are almost there, all of which was achieved with absolute anchorage in the upper arch and molar mesialization in the lower arch. Figure 18. At the end of treatment, the midlines are coincident, the lower connection zone between centrals is straight, and the occlusal plane is no longer is canted. 306 Alvarez CHANGING THE VERTICAL PLACEMENT OF THE MICROIMPLANT BILATERALLY For a better understanding of the biomechanical effects of chang- ing the vertical placement of the microimplant bilaterally, a brief explana- tion is presented. As forces are applied away from the center of resistance (CR), a rotational moment is created around the center of rotation. Thus, if the microimplant is placed in a higher vertical position than the usual 6 mm gingival to the archwire, two moments are created. The first moment is created around CR of the anterior teeth and the other moment is created around the CR of the posterior teeth (there are actually two moments, i.e., One on each side, but the drawing shows only one side). Because both mo- ments act in opposite directions, they produce subtractive forces. The moment formula is defined as M = force x distance, so if the force vector passes closer to the anterior CR than to the posterior CR, the posterior moment is larger and prevails over the anterior moment. This re- Sults in a system that closes extraction sites with a bite opening component and that has a tendency to change the occlusal plane inclination (Fig. 20). Figure 20. When the Nº. force vector passes closer *º \\ to the posterior CR than W tº ºn to the anterior CR, the N posterior moment is larger ſº Nº. rººk than the anterior moment. H/ \tº º The arrows represent the two moments. The larger the arrow, the greater the moment. Figure 19. These final images show that pa- tent J.D. has a leveled occlusal plane and Similar torques on both sides. - - 307 Microimplants: Partners for Challenges If the microimplant is placed approximately 6 mm above the arch- wire, the force vector passes at about the same distance from both centers of resistance and the moments oppose and neutralize each other. This sys- tem delivers neutral forces in the vertical plane of space (Fig. 21). ºil. Figure 21. When the force Wº. WLºº N vector passes at the same N - iſºlº distance from both CRS, ºm the moments oppose and Fºl. neutralize each other. If the microimplant is placed closer to the archwire (i.e., less than 6 mm above the archwire), the moments act in the same direction and the forces are additive rather than subtractive. Orthodontically, this means that the bite closes and the occlusal plane rises in the posterior region and low- ers on the anterior side (Fig. 22). BILATERAL HEIGHT CHANGE AND TORQUE CONTROL Patient N.W. was brachyfacial and had a biprotrusive low angle, which presented an interesting challenge (Figs. 23 and 24). The need here was not just to retrude the anterior teeth, but also to intrude them and maintain torque as much as possible. N.W.’s profile needed a change, but losing too much torque could be worse esthetically. 308 Alvarez N tººl ſº -º-, [T || hºuſ: Figure 22. When moments act in the same direction, the occlusal plane angle changes only if full fixed appliances are used. Figure 23. The frontal view shows that patient N.W. which is confirmed in both lateral views. The molars and canines are in a Class II relationship with canine overjet. has a deep overbite, 309 Microimplants: Partners for Challenges 16 Figure 24. The most impor- tant measurements are inter- 15 incisal angle (97°), lower in- cisor to APo (7.3 mm), lower facial height (41°) and lip protrusion (2 mm). 14 By using microimplants as anchorage, a large retrusion of the an- terior teeth can be obtained, but since the forces are applied away from the center of resistance, maintaining vertical control is a problem (Fig. 25A). To increase vertical control, the microimplant position can be raised as explained earlier. Torque control is another critical aspect of space closure. Chang- ing the length of the hooks and making the force vector pass along the center of resistance is the key (Fig. 25B). If the force vector passes along the center of resistance, anterior teeth can be retruded and their inclination maintained. Figure 25. A: Typical explanation of a moment created by applying forces away from the CR. B. Different colors signify different actions: red arrows and hook represent torque loss, orange arrows and hook represent torque maintained and yellow arrows and hook represent torque gain. 310 Alvarez Patient N.W. presented with a very deep overbite and a Class II relationship. Because he was biprotrusive, the lower anterior teeth had to be retruded first. As torque loss was necessary, retrusion was achieved us- ing a smaller than full-size archwire (Fig. 26). Both microimplants were placed as high as possible, and two long, crimpable hooks were used to gain more torque control (Fig. 27). The archwire had a slight curve-ac- centuated curve of Spee. Figure 26. Intraoral views of space closure mechanics in the mandibular dental arch. Figure 27. High pull, high hooks were used for torque control. Day one (left) and three months later (right). Notice the overbite correction that has been achieved during this period of retrusion. In Figure 28, the overbite correction is even greater, and the Class | relationship is evidence of the success of the retrusion. 3 || Microimplants: Partners for Challenges Figure 28. Continuation of space closure in both arches. At the end of treatment, this patient had a satisfactory molar and canine Class I relationship. Both the canine overjet and the overbite have been corrected (Fig. 29). Figure 29. At the end of treatment, midlines are aligned and the canines have the same torque on both sides. Lateral views show a Class I relation- ship. Notice that the microimplants, which still are in place, are positioned so high in the vestibules that they cannot be seen in a frontal view. With such a great amount of retrusion, we expected a significant change in the patient’s profile. Our expectations were met and confirmed by the lateral facial view (Fig. 30). Superimposing tracings on both the 312 Alvarez beginning and ending profile photographs show that there was a maximal retrusion, a gentle intrusion, and a little torque loss (Fig. 31). When com- paring the initial and final photos, it is evident that there was no favorable growth, just significant orthodontic movement. Figure 30. A balanced profile with correct upper and lower lip curvature. The upper lip shows 2 mm of lip sulcus, which is very difficult to main- tain when retruding. Figure 31. Comparison of measurements taken at the beginning and at the end of treatment. The interincisal angle changed from 97° to 128°. The lower incisor to A-Po distance changed from 7.3 to 0.3 mm. The lower facial height remained 41°. 3.13 Microimplants: Partners for Challenges Note this state-of-the-art tip; the type of variable crimpable hook seen in Figure 32 can be used to vary the type of pull during treatment, if needed. Figure 32. A variable crimpable hook. POOR DENTAL HISTORY Dental histories often contain biomechanical limitations like the one in patient S.S.’s history. This female patient wanted to replace her missing teeth with two implants in her lower jaw, but due to the vertical drift of the upper molars, there was no room for the crowns (Fig. 33). In this case, which was the first patient that I treated with microimplant an- chorage, two microimplants were placed on the buccal side and one on the palatal side initially to intrude the first molar (Fig. 34). A bonded tube was used rather than a band to provide less interproximal friction and to avoid biologic width invasion. Figure 33. Note the edentulous space between the second premolar and third molar and the vertical drift of the upper first and second molars. 3.14 Alvarez Figure 34. Two microimplants placed on the buccal side (Dentos ATx1311. 106) and one placed on the palatal side (Dentos ATP1311-110). After two and a half months, a positive change was seen, which included the intrusion of the second premolar (Fig. 35). What happened Was that the first molar's height of contour was below that of the second premolar, and the molar intrusion delivered intrusive forces on the premo- lar. Figure 35. Note the premolar intrusion. Once overcorrection was achieved, the elastic forces were discon- tinued and the first molar was tied to the microimplants and used as verti- cal anchorage for intruding the second molar. On the buccal side an arch- Wire was used, and “old–fashioned” cantilever mechanics that were sim- ple, predictable, and effective were used on the palatal side (Figs, 36–37). 315 Microimplants: Partners for Challenges Figure 36. Notice how close the molar tube came to the screws now tied with a ligature wire. On the palatal side, cantilever mechanics were preferred rather than an archwire because the force application would be better. Figure 37. First and second molars have been intruded. In the palatal view, notice the marginal ridges leveling. The objective of getting this patient’s upper teeth in the same plane was achieved. Once her temporary crowns were in place over the lower implants, the ligature wire was cut and the overcorrected upper molars drifted a little to reach the plane of occlusion (Fig. 38). Figure 38. The upper molars occluding with the lower temporary crowns. The occlusal plane has been corrected. In the first microimplant cases, too many microimplants were used. Today, both first and second molars are intruded at the same time with just two screws (Fig. 39). If by chance, there is a need for two mi- croimplants on the buccal or palatal side, using NiTi spring forces is much better than using elastic forces. This can be done by taking a regular NiTi spring and making it into two short springs (Fig. 40). 316 Alvarez Figure 39. The drawing in this figure shows the ideal placement and activation of microimplants for intruding both molars at the same time. Figure 40. A regular NiTi spring becomes two short springs. BIO-LIMITATIONS, CANTED OCCLUSAL PLANE In this next case, in which the patient presented with a severely Canted occlusal plane, microimplant anchorage proved to be a great ad- Vancement in treatment. Until the development of this type of anchorage, the choice of treatment for these types of cases was surgery or clinical 317 Microimplants: Partners for Challenges crown lengthening, root canal and crowns. It must be difficult for a patient to choose either of these approaches. Similar to patient S.S. discussed earlier, this patient also wanted to replace lower missing teeth and the upper teeth were invading the vertical dimension of the supposed crowns. Two microimplants were inserted on the right side in order to intrude the entire right side to level the occlusal plane. Figure 41 shows a dramatic improvement. The first photograph was taken at the beginning of treatment, the second photograph was taken three months later, and the third was taken after five months of treatment. Not only can the difference be seen by looking at the reference lines, it also can be seen by looking at the distance from the upper archwire to the microimplant head. Figure 42 shows a leveled occlusal plane, and Figure 43 shows change in appearance from the beginning to the end of treat- ment. Figure 41. There was significant improvement with a little flaring due to intrusive forces applied buccally to the CR. 3|8 Alvarez Figure 43. The facial improvement, with similar torque canines and no buc- cal corridors. The minor flaring on the right side is matched by the left tooth positions. Special care must be taken to avoid torque loss when pulling only from the buccal side. If maintaining torque is a goal, an additional micro- implant can be placed on the palatal side. Another possibility would be to use a palatal bar or bonded lower premolar brackets to deliver negative torque. However, almost every canted occlusal plane case shows torque loss that can be treated with a single microimplant if it is located above the deepest point of the curve formed by the archwire. The case shown in Fig- ure 44 is a good example of this. The deepest point of the archwire curve Was located around the canine, so the microimplant was placed distal to the canine, which produced a good result. Figure 44. The deepest point of the archwire curve indicates the best location for the micro- implant. Figure 42. The occlusal plane has been leveled. However, this patient’s dental his- tory limits treatment goals such as aligning the midlines and bringing the canines into a Class I relationship. - - 3.19 Microimplants: Partners for Challenges SKELETAL LIMITATIONS Correcting an open bite is one of the greatest challenges in ortho- dontics. This next patient (Fig. 45) was treated in the orthodontic post- graduate training program at the University of El Salvador (USAL), Bue- nos Aires, by Dr. G. Tonso, a former student. He had a long face and an inverted Smile arc, and his tongue is visible in his smile photographs. The overall aesthetics of his face was not bad, and he was satisfied with his appearance. 320 Alvarez The intraoral images (Fig. 46) show a “six-to-six” open bite with moderate upper and lower crowding. This malocclusion indicated that treatment should include a combined orthodontic/surgical treatment plan including the extraction of four premolars. However, the patient was reluc- tant to accept this treatment approach. Orthodontic treatment was started while he took some time to make up his mind. Figure 46. The maxillary and mandibular teeth were in contact only at the Second molars. There was a Class III component requiring autorotation. Crowding was moderate. Treatment was started as usual from flexible to stiff, toward the presurgical VTO (visual treatment objectives) goals. Some months later after returning from a summer vacation, this patient came back to our clin- ic and said that he was not going to have surgery, because he felt satisfied With the result shown in Figures 47 to 49. Seeking a counterclockwise rotation of the mandible, we con- Vinced him to stay in treatment and give microimplants a try. We placed three microimplants on each side, trying for a 1.5 to 2 mm molar intru- Sion. This case was one of the first cases in which we used microimplants, Which is the reason that we used so many screws. Figure 45. Facial esthetics were not bad for this patient, but the lower third of his face Was long relative to the rest of his face. The Inverted Smile arc resulted in a poor smile. - - 321 Microimplants: Partners for Challenges Figure 47. Notice the incisal edges of the lower anteriors with no physiological wear. Figure 48. The treatment plan was to intrude the first molar alone, followed by the second molar. In an extraction case, 1 mm of intrusion posteriorly translates into between 2 and 2.5 mm anteriorly. Figure 49. Two microimplants were placed on the palatal side. Bone physiology is not my expertise, but this patient responded in an unusual way. His teeth moved very quickly and, unfortunately, SO 322 Alvarez did his six microimplants. All of the microimplants became loose after approximately two years, but during that period, some molar intrusion was achieved, along with some bracket repositioning. The result was an encouraging edge-to-edge bite, so the decision was made to replace the original six microimplants with four longer and thicker microimplants (Fig. 50). Figure 50. A little more than an edge-to-edge relationship was achieved in ten weeks. The new set of four microimplants was placed higher than the original microimplants and with a different angle to avoid the original mi- croimplant perforations. The new set of screws supplied the anchorage needed to allow us to provide the finishing details of treatment. The results were far from perfect, but they were a lot better than we had expected that they would be. It was impossible to convince this patient to stay in treatment in order to improve these black triangles (Figs. 51 to 52), as he was taking a long trip and was happy with the results. His final facial photos show a nice smile with good tooth display (Fig. 53). He has a beautiful smile arc compared to the one he showed at the beginning of treatment. His profile is more balanced, the upper and lower lip sulcus replaced the stiffness that almost every open-bite patient shows. There was not, however, a large profile change. It is as important to know the limitations of microimplants as it is to know their capabilities. Microimplant therapy cannot replace a LeFort surgical procedure when One is necessary. 323 Microimplants: Partners for Challenges Figure 51. Some second order bends were made to improve the tooth dis- play (remember the inverted smile arc). The patient was instructed to wear elastics for occlusion settling. - Figure 52. Final intraoral images show a canine Class I occlusion and mid- line coincidence. Some black triangles are due to incisor shape (the lower) and bone loss on the lateral incisor (the upper). The overall results were good, with correct anterior and canine guidance. 324 Alvarez Figure 53. At the end of treatment, the patient has a nice smile with its cor- responding smile arc. The profile appears relaxed and balanced. - - 325 Microimplants: Partners for Challenges Once again, it is important to remember that the use of micro- implants is advancing day by day. Treatment strategies are changing and the quantity of microimplants needed per case is decreasing as our under- standing of their capabilities grows. Figure 54 shows a current approach for correcting an open bite. This treatment protocol uses only three microimplants: two on the buccal side and one on the midpalatal suture. The other great difference is that the intruding forces begin once a full-size archwire is in place. - Figure 54. A large open bite treated with three microimplants. The micro- implant placed between the right second premolar and the first molar was used also as anchorage to put an impacted canine. CONCLUSIONS There are lots of possibilities and developments yet to be discov- ered, but microimplant anchorage is a clinical advancement that could be compared to other innovations such as bonding or superelastic wires. Not only do microimplants provide the anchorage for treating some of our more difficult cases more easily, they also provide the chance to treat cases that cannot be treated with traditional Orthodontics. 326 THINKING OUTSIDE THE BOX WITH MINISCREWS S. Jay Bowman TAKING THE LEAP OF FAITH Around the time that temporary anchorage devices were first introduced in orthodontics, the concept of developing an associated miniscrew product was broached as a research and development undertaking for orthodontic manufacturers. The response: “Orthodontists will never get involved in placing screws in patient’s jaws and they will even be reluctant to refer pa- tients for these invasive services.” Although this assessment was spot-on for orthodontists at the turn of the 21" century, the situation has changed dramatically since then. The substantial advantages of using these de- vices seemingly have outweighed the perceived concerns for a growing number of clinicians. After referring patients for placement of more than 300 TADs, I “took the plunge” and have been inserting TADs ever since. It is important to note that this transition did not occur without significant prior investigation, continuing education, and a great deal of reasonable trepidation. Consequently, this document might be considered a “call-in” testimonial from the recently converted. A SPIKE IN THE ICE: A DIFFERENT “ANGLE” Attempts to insure that tooth regulation is predictable, efficient, and effective have focused historically on methods of stabilizing anchor- age for directional forces by pitting groups of teeth with larger root sur- face areas against those with presumably less resistance to movement (i.e., molars versus anterior teeth). Unfortunately, moving teeth with the best of intentions (and mechanics) is much like a “tug-of-war” tak- ing place on a sheet of ice, as teeth often seem to slip toward each other; losing anchorage to some unpredictable degree. The addition of tradi- tional “temporary anchorage devices” such as extraoral headgear, intra- oral holding arches and intermaxillary elastics, along with some elaborate strategies of “setting anchorage” (e.g., pushing roots into cortical plates, “tent-posting” or tipping-back groups of teeth) have been successful 327 Thinking Outside the Box enough to produce favorable results in most instances. Unfortunately, many of these methods also require a modicum of patient compliance, a commodity that is in short supply in our contemporary Society. It would seem reasonable that the addition of a temporary, but rigid, anchor (a “spike in the ice” placed to support one side of the tug-of- war), could enhance typical orthodontic mechanisms and facilitate more predictable and previously unimagined treatment possibilities. We’ve just seen the tip of the iceberg of this real paradigm shift in orthodontics. It is in this light that the argument for the adoption of miniscrew anchors begins. A SCREW BY ANY OTHER NAME What’s in a name (microscrews, micro-implants, miniscrews, pins, posts, anchors, orthoDADs)? To paraphrase the Bard, “a screw by any other name . . . .” seems applicable here as the important issue is what these anchorage devices are, not what they are named. But, in fact, what should we call them so that communication is clear? Arguments about nomenclature (naming rights?) were no longer just a matter of academic discourse once vested interests in proprietary terms and trademarks be- came involved. For the clinician, unambiguous explanations to prospec- tive patients and referring dentists are perhaps as important at this stage as scientific communication. Educating patients and referring dentists about these devices can be confusing or even misleading, especially when these devices most often are basically “small screws.” Temporary anchorage devices or TADs is a term originally coined by George Anka (Mah and Bergstrand, 2005). “TADs” also would seem- ingly encompass other temporarily employed anchorage methods such as headgear, elastics, fixed functionals, transpalatal and lingual arches, Nance buttons, osseointegrated implants, etc., along with the intended object of this nom de guerre. The typical type of device used as a non-Osseointe- grated anchorage device in orthodontics is simply a miniature screw (i.e., miniscrew), about the size of the screw most often used in the hinge joint of common eyeglasses (an item that most patients can easily relate to). Consequently, it might be more straightforward to tell the layperson that a “miniscrew” is used as a temporary post that is placed in the bone to sup- port specific, directional forces and that they enable more predictable and efficient tooth movement than previously possible in orthodontics. 328 Bowman DUE DILIGENCE So, you wish to get started with miniscrews. Aspiring to incor- porate miniscrews into a practice and actually doing it are two completely different things. The adoption process for the clinician appears to consist of the following steps: 1) due diligence or educating all clinicians, staff, and referral network personnel; 2) selecting an appropriate miniscrew system; 3) acquiring the necessary armamentarium; 4) planning treatment for TAD-supported mechanics; 5) educating patients so that there can be true informed consent; 6) prepping patients and preparing clinical procedures; 7) inserting implants; 8) applying biomechanics; and 9) following up post-operatively. Mark Twain wrote, “Training is everything. The peach was once a bitter almond; cauliflower is nothing but cabbage with a college educa- tion.” At first glance, inserting small screws into patients' jaws appears to be an intuitively simple procedure (who hasn’t had a screwdriver in their hands at one time or another?). However, there must be much more to it than just the type of “some-assembly-required” instruction pamphlets that typically accompany the construction of children’s toys or handy-craft home furnishings. Although our specialty’s literature has benefited from a plethora of publications, continuing education courses, and Symposia on TADs, the majority of our communications have consisted of anecdotal case reports or are proprietary in nature. As such, cautious skepticism is warranted. In spite of the increased access to our literature via the internet, a comprehensive literature search may yet be a daunting task for the inquisi- tive clinician. Some of the existing anecdotal materials on TADs have been organized and summarized in textbooks and instructional CD-ROMS and DVDs. Incorporated in these CDs and DVDs also are the results of the few research studies that have been carried out, along with some in- structions or demonstration videos for recommended use that are often “brand specific.” Referencing several sources of this type of background material (including this monograph) in combination with a few “hands- on” courses given by different manufacturers can provide at least more than one perspective upon which clinicians can build a foundation when preparing to incorporate miniscrews into their practices. 329 Thinking Outside the Box MULTITUDES OF MINISCREWS The Paradox of Choice Sophocles once advised, “Quick decisions are unsafe decisions.” So, how do you decide which miniscrew systems are best for your practice? Do you simply select the product demonstrated at the last C.E. course you attended, one that was used in a successful case report, or the one that your classmate recommended? There are so many screw-head designs, shaft diameters and lengths in the marketplace that the consumer can become paralyzed by the availability of choices (Schwartz, 2004). Can’t someone just tell me what to use? The clinician first must decide the type of applications that mini- screws primarily will be used for in his or her practice. For example, if direct anchorage is the goal, then miniscrew head designs that facilitate the simple attachment of elastic chain or coil springs are desirable. In contrast, mechanics that involve indirect anchorage may necessitate head designs that permit the application of sectional or continuous wires. In fact, a head design that could be adapted easily to either alternative might be more advantageous than maintaining an inventory of screws with mul- tiple head designs. Once a decision is made regarding the type of head design that is most desirable, the clinician would like to know if the screw is easy to place. In other words, what procedures are required prior to insertion (e.g., tissue punch, pilot holes) and how user-friendly are the devices that are used to actually drive the screws (e.g., drivers, torque wrenches, latch- handpiece attachments)? Finally, it would be nice to know the success rate of a particular screw design, information that should not be denied to clinicians because it is proprietary in nature. It is certain that the marketplace eventually will experience a “shakeout,” leaving only those miniscrews on the market that are preferred in terms of quality, price, survival rate, ease of use, vendor support, and range of clinical applicability — a kind of TAD “survival-of-the-fittest.” As a result of this forced evolution, manufacturers will start thinking more like orthodontists rather than carpenters or even oral surgeons. Until that time, however, clinicians will have to sort through the morass to find the products most appropriate for their patients. Perhaps clinical experience with more than one system would be advantageous at this early-adoption stage. Don’t forget that staff edu- cation also is extremely important, as the concept of sticking tiny bone screws near the roots of patients’ teeth is perhaps more disconcerting and 330 Bowman alien to them than to the orthodontist. If staff members can observe the insertion procedures involved in placing miniscrews personally, it will fa- cilitate the acceptance and adoption of this technology. ACQUIRING THE ARMAMENTARIUM Any avocation often has at its foundation the accumulation of equipment (even when the hobby itself is accumulation [collecting]). Pur- chasing a miniscrew system, with the associated equipment necessary for the insertion of the screws, seems to be an inexpensive and compelling decision. Unfortunately, there are other practice management, equipment, and economic considerations that should be contemplated before taking the plunge. Are panoramic radiographs sufficient or are periapical films or even CBCT scans necessary before and after insertion of TADs? What an- esthetics, analgesics, antimicrobials, sterilization equipment, and patient instruction materials are required? What are the time requirements for educating the staff and patients about not only the procedures for placing miniscrews, but also the equipment? Finally, what are the costs of screw auxiliaries and the time requirements for incorporating these new mechan- ics into routine daily practice? After carefully weighing all of these fac- tors, we must bring the most important aspect into focus – the patient’s needs. TAD-BASED TREATMENT PLANNING Academics Gianelly, Johnston, and Behrents prophesized that miniscrews would completely change orthodontics and that we actually would have to learn how to move teeth again. In effect, these orthodon- tic patriarchs were echoing the same prediction made by Creekmore and Eklund (1983) twenty years previous. Although the theoretical advan- tages of miniscrew anchorage are undeniable, there still is some debate about their acceptance (Kesling, 2005; Melsen, 2005; Sheridan, 2007). With the adaptation of TADs to our specialty, learning “tooth regulating biomechanics” has suddenly returned to the forefront of orthodontia. It is important to note, however, that miniscrews do not change our diagnoses, only our treatment plans (Bowman, 2006). For specific patients, the first question to ask is, “How will more predictable directional forces benefit them?” Examining case reports of similar clinical situations would be a formative step, but more back- ground knowledge is necessary. The present monograph, including the 331 Thinking Outside the Box references listed for each chapter, and other similar reference materials are an excellent starting point in this endeavor. After some preparatory education, at which point you have elected to sink that “spike in the ice” for your patient, where are you going to in- sert it to both ensure the best mechanical advantage and avoid vital struc- tures (i.e., roots, sinus, nerves, blood vessels); what are the so-called “safe zones” (Marti et al., 2004; Anka, 2006; Poggio et al., 2006)? What are the optimal forces necessary for implant placement and the accompany- ing biomechanics? Should screws be loaded immediately or left alone to permit some bone healing (Cornelis et al., 2007)? These are concerns ex- pressed in a recent systematic review by Cornelis and colleagues (2007). Pre-operative Records: Radiography Following a patient examination and review of potential contra- indications based on medical history (e.g., smoking, diabetes, etc.), di- agnostic records need to be evaluated to select a spot for the miniscrew. Is there adequate cortical bone thickness and density, especially in that primary stability of the implant is highly dependent upon these factors? Does a panoramic film provide accurate representation of root proximity to enable selection of an insertion site or is a CBCT required (Kim et al., 2007)? What about a preoperative periapical or bitewing film? Is a surgi- cal stint (Kim et al., 2007) or “wire” placement guide required (Caruso and Rungcharassaeng, 2007; Choi et al., 2007; Kravitz et al., 2007), and how accurate would either be considering that a wide variation in the in- sertion angle of a miniscrew is still in play? Other questions arise. Is an immediate post-operative radiograph required for any other reason than liability concerns? How accurately can miniscrew proximity to a root be determined either by a patient’s report of pain during insertion or by appearance on an immediate post-opera- tive radiograph, and if the miniscrew appears to be touching a root, does it need to be removed immediately and should antibiotics be prescribed? What if the miniscrew eventually touches a root during tooth movement? Liou and colleagues (2004) have demonstrated that miniscrews do provide stable anchorage, but they do not remain absolutely stationary; they may, in fact, extrude and/or tip. What if the screw happens to “tip” into a root during treatment? Unfortunately, these questions may be answered only with clini- cal experience, something we gain only after we need it. At the outset, it should be noted that the identification of a favorable location for a mini- 332 Bowman screw by means of a radiograph is no guarantee that this identification will translate clinically into an ideal implant placement. We must do the best we can, however. Safe Zones Are there some areas of the mouth that are “safer” for miniscrew placement? While the term “safe” refers to reduced risk of iatrogenic damage, it also refers to a lower loss rate potential as well. Poggio and colleagues (2006) used a series of tomographic images to describe the areas (posterior to the canines) where more thickness of cortical bone and interradicular space are available. In the maxilla, the largest amount of interradicular bone is found in the palatal alveolus between the first molar and second premolar and the least amount is found in the tuberosity. The most substantial amount of bone buccolingually is found between the first and second molars. In the mandible, the largest mesiodistal dimension is between the first and second premolars and the thickest bone is found again between the first and second molars and the least amount between the first premolar and canine. From a panoramic evaluation, Schnelle and co-workers (2004) re- ported that adequate bone stock typically is mesial to the maxillary first molars and mesial or distal to mandibular first molars. Unfortunately, the best locations often are found halfway down the roots in the unattached mucosa, so some compromise in vertical position may be required. Creating Space If unsure about the amount of interradicular space available for placing a miniscrew, hold off and “make some space;” compressed open- coil springs are useful for this. Many aspects of treatment can be initiated before adding TAD-supported mechanics. Too often orthodontists are in a hurry to just “put on the braces” and then “put in a screw.” At the start of treatment, brackets can be placed to affect some divergence of roots (Bowman and Carano, 2004) prior to inserting a miniscrew. After screw removal, these brackets can be repositioned for proper root paralleling. Screw Size What size screw should be used? The combination of available diameters and lengths is mind numbing. Kuroda and co-workers (2007) reported that 1.3 mm diameter/8 mm screws had a 90% success rate. 333 Thinking Outside the Box They also recommended that screw length should be selected on the basis of having 5 to 6 mm for bone support after taking into consideration the thickness of soft tissue. For example, a 10 mm screw would be selected if the soft tissue was 4 mm deep. Costa and colleagues (2005) described intraoral hard and soft tis- sue depths available for different regions of the mouth. Although there are locations where 10 mm miniscrews may be used (symphysis, retromolar, and palatal premaxillary regions), screws 6 to 8 mm long will serve for the majority of locations. Besides, stability depends more on screw diameter than screw length (Miyawaki et al., 2003; Berens et al., 2006). Photography: “X” Marks the Spot Intraoral photographs also are useful in TAD site selection as de- terminations of soft tissue quality and quantity cannot be made from radio- graphs or study models. Although self-drilling miniscrews can be inserted directly through mucosal tissue, a stab incision or tissue punch likely will be required when miniscrew placement occurs in the unattached mucosa to prevent the tissue from “winding-up” the threads. When screws are inserted in the buccal mucosa, the potential for subsequent tissue irritation and overgrowth can necessitate an incision or even excision of hypertro- phic tissue prior to the eventual removal of the TAD. As a result, it may be more practical to select implant sites within the confines of the attached gingiva whenever possible. Sketching prospective biomechanics directly on an extra print- out of the patient’s intraoral photos or on a treatment planning form with diagrams of the dental arches is extremely useful (Caruso and Rungcha- rassaeng, 2007). Drawing an “X-marks the spot” or placing an adhesive “dot” (%” Dot Label MR 404–16 Maco, ACCO Brands, Inc., Lincolnshire, IL) directly on the photograph where the miniscrew should be implanted (Fig. 1) are simple and practical references. These Alice S Restaurant type of “photos with circles and arrows and a paragraph on the back of each one” (Fig. 1) can be used in consultation with patients as procedural in- structions for staff, in communications with referring dentists, and perhaps most importantly, as a chair-side reminder at the time that the implants actually are placed. Simple line drawings help the orthodontist to frame the mecha- nism to be used for anchorage control. In addition, a whole new selec- tion of possible side effects that could arise from TAD-supported force systems may become more apparent during this exercise. For example, 334 Bowman Figure 1. Applying adhesive “dots” and drawing proposed mechanics on patient photographs assist in treatment planning and patient communication. An adult female with Class II mutilation malocclusion required the extraction of maxil- lary second premolars. Space closure and intrusion of a hyper-erupted molar Was accomplished using anchorage from two IMTEC miniscrews. Note: All of the maxillary spaces are closed and interproximal amalgam restorations are Visible between the first premolar and molar. When retracting anterior teeth along an archwire, the posterior teeth are also likely to be distalized. In addition, when protracting molars into an extraction site along a continuous archwire, this movement may cause flaring of the anterior teeth. Finally, comparing the photos of the cur- rent clinical situation with previously published case reports of similarly treated patients also is beneficial. Procedure Orders: Location, Location. Location Who should place miniscrews? Ninety-five percent of minis- Crew acolytes currently prefer to refer (Sheridan, 2007), but N.F.L. (not for long). Like many recent converts (Tracey, 2006), they likely will find that convenience, control, and cost are compelling factors to D.I.Y (do It yourself). If, however, the decision is made to refer the patient to a 335 Thinking Outside the Box periodontist or oral surgeon for placement of the TAD, a narrative descrip- tion of the exact desired position of the implant is critical. These instruc- tions should include details of the position of the miniscrew relative to the mucogingival junction and marginal gingival, the insertion angle rela- tive to the alveolar bone, and the orientation of the hole, slot, or bracket that may be featured in the head design of the screw. In addition, the instructions must describe whether the screw should be driven until the transmucosal collar touches bone or is partially embedded in the tissue and whether the head of the screw should be compressing, just touching, or slightly above the tissues? “Plan for the best, expect the worst, and be prepared to be surprised” – Denis Waitley. The advent of TAD-supported anchorage certainly has stimulated imagination, innovation, and creativity within our specialty. Biomechan- ics may be applied so effectively using TADs (e.g., a third molar could be potentially protracted into the first molar position or mandibular anterior teeth could be retracted right out of the alveolar ridge) that caution must be exercised. For example, translating, intruding or extruding a tooth over a substantial distance potentially could result in significant root, bone, or periodontal loss. PATIENT EDUCATION The time has come to present your well-planned, TAD-based treatment plan to the patient. The moment you mention that a pin, post, or screw will be placed in his or her jaw bone, the tone of the discussion changes. “The best-laid plans of mice and men often go awry,” is a quote adapted from Robert Burns that seems apropos for this occasion. A sim- ple discussion of the biomechanical advantages of miniscrews compared to the inherent risks and a description of the basic procedures required for placement should allay patient fears and permit them to provide in- formed consent for the procedure. The majority of patients quickly will realize the advantage of predictable and effective directional forces com- pared to the associated costs (i.e., some discomfort and possible risks). Both Kravitz and Kusnoto (2007) and Graham and Cope (2007) have provided excellent summaries of the risks and complications for orth- odontic miniscrews. Patient discussion also would benefit from a copy of a published report or photographs of another patient with similar treat- ment circumstances (Carano et al., 2005). However, showing patients 8” x 10” enlargements of miniscrews or exposing them to typodonts that are filled like pin-cushions with miniscrews can be very intimidating. A simple and unimposing alternative is the tomas demonstration model, a 336 Bowman Figure 2. A basic demonstration typodont with a single miniscrew (tomas dem- onstration model) is less imposing to patients than enlarged images of mini- Screws or even typodonts covered with multiple miniscrews, auxiliaries and braces. clear quadrant typodont with only one “pin” in place (tomas Demonstra- tion Model # 02-302-006-000, Dentaurum, Ispringen, Germany; Fig. 2). INFORMED CONSENT It is important for patients and the practice to have a copy of a signed form securing informed consent (see the Informed Consent form available from the AAO, as it includes a description of risks and limita- tions with TADs; Informed Consent, 2005). The patient discussion should include the possibility of premature loss and replacement, resolution of any inflammation or infection, potential for iatrogenic ankylosis, “nicked” roots, consequences of screw breakage – not an unlikely event (decision: to leave the broken portion [Holmes, 2006] or to perform surgical trephi- nation), damaged nerves or roots, or perforation of the maxillary sinus. Complications or allergic reactions from any anesthetics that may be used also must be considered. Finally, a combined pre- and post-operative in- Struction sheet (Fig. 3) can be prepared for patient and parental reference. This document also might include the rationale for selection of TAD-sup- port and the basic procedures that will be performed. In the current litigious environment, practitioners must confirm that their malpractice insurance policy covers the procedures involved in the use of TADs. For example, insurance from the American Association of Orthodontists Insurance Company (AAOIC, 2005) describes the fol- lowing limits of liability exclusion: This insurance does not apply: 1. To any injury resulting from the performance of any surgical procedure or surgical extraction or 337 Thinking Outside the Box the performance of a non-surgical extraction. This exclusion does not apply to: 5. The placement of microimplants that do not in- volve the reflection of a surgical flap. S. Jay Bowman, D.M.D., M.S.D. Kalamazoo Orthodontics P.C. 1314 West Milham Avenue, Portage, MI 49024 Office: 269-344-2466 Home: 269-372-7554 ORTHODONTIC ANCHORAGE DEVICES – MINI-IMPLANTS OR TADS Mini-implants or temporary anchorage devices (TADs) are simple, small screws that are placed in the jaws to facilitate tooth movements during orthodontics. Often this tooth movement occurs in a manner that could not be accomplished with only traditional orthodontic mechanisms, or would require alternative treatments (headgear, extractions, surgery, etc.), and longer, more complex treat- ment mechanics. The placement of a mini-implant is a brief, minimally-invasive process that has three parts: anesthesia, placement and attachment of orthodontic forces. Patients have reported minimal discomfort or problems with mini-implants, but their orthodontic treatments and results have been significantly enhanced; making TADs exceptionally helpful little tools. PRE-OPERATIVE INSTRUCTIONS To prepare for mini-implant (TAD) placement, we recommend that you take an over-the-counter analgesic (e.g., Ibuprofen or Motrin) about an hour prior to your appointment. We use a very strong topical anesthetic called TAC alternate gel. This material is simply swabbed with a cotton tip onto your gum tissue just in the location where your mini-implant will be placed. This gel will provide numbness to your gum tissue in about 5 minutes and lasts about 30 minutes. Remember, the miniscrew is very small, so the area to be numb does not have to be very large either (it is not like having a dental filling or extraction of a tooth). In some situations, we also may place a drop of anesthetic just under the gum tissue with a typical dental syringe and then the miniscrew will be placed into that same exact spot. We will swab the gum tissue with a disinfecting material before the sterile mini-implant is inserted. The entire process of actually placing each miniscrew typically takes about 2-3 minutes. During placement, you will feel pressure from the implant, but no pain is expected. POST-OPERATIVE INSTRUCTIONS We recommend that you take Ibuprofen, as needed, for any discomfort. Please rinse with a capful of Peridex (Chlorhexidine Gluconate) for 30 seconds, specifically in the area of the mini-implants, twice each day for one week. If you notice any gum-tissue swelling around the miniscrew, you may continue to rinse once each day to help reduce it. You must keep the mini-implant clean to avoid failure or loosening of the device. A soft bristle toothbrush or even a cotton swab (Q-tip) can be dipped into a capful of Peridex to massage debris, food and plaque away from the mini-implant along with regular oral hygiene. Avoid hard, chewy or sticky foods around the implant. The same list of foods to avoid with braces is applicable for mini-implants. Figure 3. TAD instruction sheet for pre- and post-operative reference. 338 Bowman A FEW LOOSE SCREWS Any discussion of miniscrews eventually gets around to the con- sideration of “premature loss.” Perhaps the most pervasive and frustrat- ing aspect of adopting miniscrew anchorage is the possibility of failed implants. Patients and parents must clearly understand that one or more Screws may need to be replaced one or more times during a course of treat- ment. If they also understand that these temporary devices should easily be removed at some point after their intended use is complete, the risk of premature loss becomes a bit more palatable. The failure of miniscrews most certainly is multi-factorial in na- ture. A partial list of possible causes includes systemic disease, soft tissue inflammation (poor hygiene, Smoking, gingival impingement), bone qual- ity and quantity (poor primary stability), poor technique (heat generation, “stripped” bone, implant contamination), thickness of mucosa, insufficient length of screw to support orthodontic forces, and root proximity. Many of these factors may be controlled to reduce the rate of failure (Graham and Cope, 2006). Most experts have reported that their failure rate de- creased with experience, implying that clinical technique may be a most important aspect. In 2004, Park, one of the primary innovators in the TAD revolu- tion, reported failure rates of 12.5% in the maxilla, 16.3% in the mandible, and 4.2% in the palate, but offered the encouragement that these rates would decrease as technique improved (experience). In fact, two years later, Park and colleagues (2006) reported a 91.6% success rate for 227 screws placed in 87 consecutive patients. Failures were directly attribut- able to “mobility, the right side of the jaw, the mandible, and inflamma- tion.” Sung and co-workers (2006) reported failure for 19 of 261 (7%) microimplants placed in the maxilla and 21 of 165 (13%) microimplants placed in the mandible. Kuroda and co-workers (2007) reported an 80% success rate for 216 miniscrews placed in 110 patients, also with a lower rate in the mandible than in the maxilla. They concluded that root prox- imity was the major risk factor for miniscrew failure, i.e., the closer the implant was to the root, the higher the failure rate. Berens and co-workers (2006) found a reduction in failure rate when using larger diameter im- plants in the buccal surface of the mandible and smaller diameter screws in the surface of the maxilla; a 23% initial failure rate (N=133) was re- duced to 5% (N=106) by selecting the appropriate diameter screw. In addition, Chen and co-workers (2006) described 90.2% success for 8 mm implants and 72.2% for 6 mm implants, with an 86% success rate in 339 Thinking Outside the Box the maxilla and an 81.3% success rate in the mandible. In other words, “size matters.” The miniscrew shaft must have a diameter wide enough to support the forces required for insertion, biomechanical loading and subsequent removal, yet it must be small enough to fit between the roots of adjacent teeth. It appears that titanium alloy screws that are narrower than 1.2 mm are more likely to fracture and that screws wider than 1.6 mm will have significantly reduced numbers of “safe zones” for placement between roots (Ludwig and Bowman, 2007). The plebeian miniscrew user might simplify their inventory by keeping only a selection of 1.4 to 2.0 mm di- ameter screws of three lengths, e.g., 6, 8, and 10 mm. To Load or Not to Load Luzi and colleagues (2007) discussed the results of a prospec- tive evaluation of 140 immediately-loaded screws that were inserted in 98 patients: 9.3% failed and 6.4% “partially failed” (minimal mobility — still may be used). Graham (2006) also suggested that a slightly mobile screw is not necessarily a failure and recommended “slightly tightening the [loose] screw one or two turns.” Mobility immediately after insertion indicates inadequate primary stability. Mobility that occurs later is likely to be the result of some type of ingrowth of the epithelium (if no tissue punch was used) and/or overloading the implant (Garfinkle, 2006). Curiously, Luzi and co-workers (2007) were the only group de- scribing a greater failure rate in the maxilla (12.2%) than in the mandible (8%). They also did not mention any concern for root proximity as a reason for loss. They concluded that immediate loading with light forces should not be considered a risk factor. For example, Kuroda and colleagues (2007) reported 90% success with immediately-loaded screws. But where is the fire? Why not wait a bit before loading the screws? If screws are loaded immediately, it is extremely important not to overcome their primary sta- bility with mechanics that produce too much force or inappropriate force direction. Failure typically occurs in the first few weeks after insertion which is the same time that healing is occurring. This is why patients must be educated beforehand to the fact that “sometimes a screw gets loose and that when this occurs, it must be removed and replaced in another site.” As an aside, so-called “rescue screws” (a larger diameter screw placed im- mediately in the same site as a failed one) may demonstrate some success, but inserting another screw into a location of active inflammation seems to make little theoretical sense. 340 Bowman Younger Patients The majority of patients seeking orthodontic treatment are adoles- cents. This begs the question, “Can miniscrews be used reliably for this patient population?” Anka (2006) has cautioned that the “cortical bone will not support a miniscrew for patients under the age of 15” and that treatment should perhaps be delayed until the second molars have fully erupted or else screws should be employed only if “limited tooth move- ment [is] undertaken.” In this regard, Garfinkle (2006) reported 80.5% success for miniscrews in a sample of 13 adolescents (average age 14 years, 10 months). Although the bone turnover rate is higher and bone density or cortical thickness may be somewhat less, it certainly appears that TAD anchorage may permit some modicum of success in the adoles- cent. However, a greater risk of loss is to be expected in younger patients, and this fact must be conveyed to prospective patients and their parents. Caruso (2007) recently described the average failure rate for orth- odontic residents at Loma Linda University who placed screws at about 14% compared to the 8% to 30% loss reported in the scientific literature. The issue of loss and its resolution must be discussed with patients prior to the initiating of treatment. Patients must be cautioned: “We win most of the time, but we lose a few. If we have a loose screw or completely lose one, we likely will need to replace it in order to continue treatment.” Although brackets, wires and appliances also break during orthodontic treatment, a lost screw is a bit more disconcerting for both patient and practitioner. CLINICAL PROCEDURES AND PATIENT PREPARATION The Cope Placement ProtocolTM (Cope and Herman, 2006), which lists the sequence of events that occurs when inserting miniscrews, plus Some friendly modifications are described below: Brush and rinse with Peridex Apply topical anesthesia (e.g., Oraqix or TAC 20% Alternate) Infiltrate anesthetic prin Locate implant site (e.g., impress tissue with periodontal probe or use a placement guide) Disinfect site with Betadine Measure soft tissue thickness (i.e., bone sounding with periodon- tal probe) Use tissue punch (especially in unattached gingiva) 341 Thinking Outside the Box Make bone surface indentation (No. 2 round bur) or pilot hole (1.1 mm drill) through cortical plate prin Insert implant and attach load In many instances, the tissue punch and pre-drilling may be omitted (e.g., when a self-drilling screw is placed within the attached gingiva of the maxilla). Preliminary Preparation At the appointment prior to miniscrew insertion, the procedures for the next visit are reviewed with the patient. Pre-operative instruc- tions (Fig. 3) and a prescription for 0.12% chlorhexidine gluconate (for post-operative use) are given to the patient. At the miniscrew insertion ap- pointment, the patient should brush, rinse thoroughly with water, and then rinse with 15 mL of 0.12% chlorhexidine gluconate to reduce the intraoral bacterial flora. At this point, the exact site selection is reviewed and can be con- firmed with radiographic evaluation of a placement guide or stint. Any last minute changes in the type, diameter or length of the miniscrew should be made prior to initiating anesthesia. Anesthetics Most miniscrews can be placed using a profound topical anesthetic without substantial patient discomfort (Fisher, 2006; Kravitz and Kusnoto, 2006). Miniscrew enthusiasts have recommended several topical alterna- tives. One of the most popular, available by prescribed pharmaceutical compounding, is TAC 20% Alternate topical anesthetic (20% lidocaine, 4% tetracaine and 2% phenylephrine; Professional Arts Pharmacy, Lafay- ette, LA). Original TAC (0.5% tetracaine, 1:2,000 adrenalin, 11.8% cocaine) anesthetic solutions were used primarily in dermatology and gynecology as alternatives to injectable xylocaine. Fortunately, research has shown that topicals without cocaine are just as effective (Schaffer, 1985; Bush, 2002). When compared to original TAC in an evaluation of pain manage- ment for repair of lacerations of 240 children, tetraphen (1% tetracaine; 5% phenylephrine), a non-cocaine alternative, demonstrated no signifi- cant difference in effectiveness for pain management (Smith et al., 1997). It would seem logical, then, that TAC 20% Alternate gel (with a higher dosage of tetracaine along with lidocaine) also would manage any pain associated with the small soft tissue wounds that accompany miniscrew insertion. 342 Bowman EMLA, another highly profound topical anesthetic cream (Astra- Zeneca, Wilmington, DE) is an eutectic mixture of 2.5% lidocaine and 2.5% prilocaine. It often is used for superficial surgery on skin and genital mucous membranes. An additional alternative is DepBlu (Steven’s Phar- macy, Costa Mesa, CA), a compound of 10% lidocaine, 10% prilocaine, and 4% tetracaine. One final possibility is Oraqix (2.5% lidocaine and 2.5% prilocaine; Dentsply Prof., York, PA), a gel that is delivered in a needle-free applicator and is designed to be placed directly into periodon- tal pockets during scaling. Any of the previous topicals can be consid- ered suitable for use when placing a miniscrew. Future comparison of the properties and performance of these various products certainly would provide clinically useful information for orthodontists who have adopted miniscrews and soft tissue lasers in their practices. Site Preparation and Anesthesia The soft tissue at the implant site should be dried with a 2’x 2" cotton gauze. About 1 gram (“a little dab will do ya”) of a topical gel or cream is applied directly to the soft tissue using a cotton swab applicator. The anesthetic is left in place for no longer than 2 to 4 minutes before thoroughly rinsing to avoid any soft tissue irritation or surface epithelial sloughing. These topicals typically provide a more than sufficient 30 min- utes of anesthetized patient working time. Isolation methods such as lip retractors (Bowman, 2004), cotton rolls and suction may be used to reduce site contamination and provide a clear working field. A povidone-iodine topical antiseptic (Betadine, Pu- rude Pharma, Stamford, CT) may be applied to the tissue as well. As mentioned previously, the exact insertion site can be located using a stent, a locator wire guide (Morea et al., 2005; Choi et al., 2007), or an “X-ray pin” (Forestadent, Pforzheim, Germany; Fig. 4). Another option is to use a periodontal probe. By impressing the side of the probe against the turgid periodontal tissue on the alveolar surface between the teeth in question, a vertical “hash mark” is produced. The probe then is rotated 90° and impressed again at the occlusogingival level of the tissue where the implant is to be inserted (“X marks the spot”). The probe is inserted through the soft tissue at the intersection of these two “marks,” down to the surface of the bone to measure the thickness of the tissue. If the patient reports feeling any significant pressure or pain from the probe, a subgingival injection and infiltration of anesthetic likely is required prior to implant placement. 343 Thinking Outside the Box Figure 4. A locator wire guide with a quick-cure acrylic occlusal rest (Ace Sur- gical MTAC ystem, American Orthodontics, Sheboygan, WI). The “X-ray pin.” is a sterile, disposable thumb tack (used much like a push pin on a wall map) that is inserted into the gingival tissue at the site selected for miniscrew place- ment. A radiograph is taken to note the location of the radiopaque analogue relative to the roots before the actual miniscrew is placed. Dental floss is tied around the pin as a safety measure in case the pin becomes dislodged when the radiograph is taken (photograph courtesy of Björn Ludwig). IMPLANT INSERTION The Needle, the Punch, the Stab, and the Drill For the majority of contemporary orthodontists, the last time that they picked up an anesthetic syringe or drilled into anything approximat- ing bone was at some date prior to their first day in orthodontic residency. It is for this reason that it was once predicted that orthodontists would not incorporate miniscrew anchorage into their practices to any significant degree. In fact, many practitioners have prided themselves on not owning a syringe or prescribing anything stronger than OTC analgesics for their orthodontic patients. Although the majority of miniscrews may be placed using only a topical anesthetic, it might be wise to have a dental syringe prepared for use as needed (e.g., 2% lidocaine with 1:100,000 epinephrine). This means that appropriate needle-capping techniques (e.g., one-handed 344 Bowman “scoop” or two-handed with an appropriate barrier), aspiration methods, and needle disposal protocol must be followed as well. If an implant is to be placed into the unattached mucosa, a stab incision with a scalpel or a biopsy or tissue punch is necessary to reduce the possibility that this tissue will twist and bunch around the threads of the screw, thereby resulting in substantial tearing of tissues. Kuroda and colleagues (2007) recently reported an 80% success rate for 116 minis- crews: 37 were placed using mucoperiosteal flap surgery and 79 were placed without the incision. Half of the patients who had no incision also reported no pain after the procedure. For most self-drilling screws insert- ed into the attached gingiva, a tissue punch is not required. On the other hand, if the tissue depth is substantial or a pilot hole is to be drilled into the cortical plate, the biopsy punch is a simple and beneficial step. Unfortunately, we can only guess as to the hardness of bone prior to inserting a miniscrew unless we have access to a CBCT scan to mea- sure Hounsfield units (HU). The force applied just to start a self-drilling miniscrew in dense bone can quickly exceed 20 Ncm and a broken screw may result. As a result, pre-drilling a 1 to 2 mm pilot hole, at least through the cortical plate, may be advantageous, even when using self-drilling screws, especially in the typically dense bone of the mandible (Fisher, 2006; Ludwig and Bowman, in press). Irrigation with sterile saline solu- tion in a monoject syringe helps to reduce over-heating bone during pilot- hole drilling. If the miniscrew or pilot drill slips or skips along the bone as the clinician is trying to insert it, the adjacent tissue could be torn. This is especially true when a pilot drill or self-drilling screw is inserted at an angle to the surface of alveolar bone (as most are). Concerns for breakage of the inherently weaker tip of the self-drilling miniscrew also increase if it first is inserted perpendicular to the alveolar bone and then the angle subsequently is changed as it is driven in further, so care must be taken. Therefore and at a minimum, it is helpful to drill a small indentation into the surface of the bone with a 9% round bur to provide a purchase point for the tip of either the pilot drill or a self-drilling screw. POST-OP FOLLOW-UP Post-operative instructions are provided to the patient and in- clude a recommendation for OTC analgesics and rinsing with 20 ml of Peridex three times per day for seven days. Peridex can also be applied directly to the tissues around the screws using a cotton swab or soft bris- tle brush. Kravitz and Kusnoto (2006) suggest that a miniscrew should 345 Thinking Outside the Box be covered with orthodontic wax to minimize tissue overgrowth and aph- thous ulceration. Oral hygiene is paramount and must be emphasized. APPLICATION OF BIOMECHANICS As miniscrews are adopted into daily clinical practice, the focus will change from implant site selection and placement protocol to the ap- plication of biomechanics. Can we say, “The sky’s the limit?” Some examples are provided below. The question “to load or not to load” has been discussed already. Screw insertion certainly damages the adjacent bone and soft tissues. It would seem intuitive that any application of forces should be very light until bone and tissue healing is complete. Besides and as stated earli- er, what is the rush? Although osseointegration, like that found with the treated surfaces of typical dental analogues, does not occur, this does not imply that there may not be some partial integration. The surface area of a miniscrew is smaller than its prosthetic precursor due to its smaller cir- cumference and the polished, untreated threads. In a study using rabbits as a model, Morais and colleagues (2007) concluded that mini-implants can be loaded immediately with no compromise in stability. After 12 weeks of healing, however, implants that were not immediately loaded demonstrat- ed a significant increase in removal torque requirements. We eventually may find, perhaps, that by permitting some degree of bone healing or re- modeling around the threads prior to loading, retention rates are increased. In other words, there is no harm in waiting a bit before adding biomechan- ics if there is any concern about primary stability. Conceivably, a small degree of intentional osseointegration could be beneficial. Perhaps, “treat- ing” the threads at the top of the screw that contact cortical bone may find its way into future miniscrew design. TAD APPLICATIONS The following case reports are merely a primer for the various orthodontic applications possible with TADs. Their presentation is in- tended to provoke thought and stimulate innovation as this rapidly evolv- ing field catches-on within our specialty. Cope stated at the 106" Annual Session of the American Association of Orthodontists that the introduc- tion of TADs is a true paradigm shift. The popular topics of today such as the avoidance of extraction, “slippery braces for smiley faces,” diode lasers, or CBCT scans do not appear, in the long-run, to “have the legs” that the innovation of miniscrews will have in improving daily patient 346 Bowman care. Miniscrews perhaps will rival the introduction of headgear, Baker anchorage (intermaxillary elastics), superelastic wire, pre-adjusted appli- ances, or direct bonding in our orthodontic annals. DEEP BITE Miniscrews got their start with Creekmore and Eklund’s (1983) description of intruding maxillary anterior teeth to reduce a deep overbite as an alternative to headgear. In the past, when discussing the use of head- gear with patients, those who were reluctant to wear a “night-brace” were facetiously teased with the absurd alternative of placing metal screws in their temporal bone that would be connected to the upper braces by rubber bands or springs as a headgear substitute. Although the proposed location of the screws is different today, the concept is the same. If given the choice, informed patients now might be inclined to opt for one or two TADs (with their attendant constant intrusive force) rather than a year or more of 12 to 14 hours/day wear of headgear appliance(s) (i.e., Tweed 10-2 anchorage preparation). In fact, as facial piercings have become more popular for young adults, the acceptance of miniscrews as a headgear alternative has also increased (Kim et al., 2007). To resolve a deep overbite, either the upper or lower incisors must be intruded and/or the posterior teeth extruded. Miniscrews can facilitate the biomechanics of either alternative. Maxillary incisors can be intruded to reduce a deep overbite, improve the Smile line or reduce gingival dis- play using direct anchorage from miniscrews placed between upper inci- sors. Intrusive force is applied directly from the TAD to the base archwire using elastic thread, chain, springs (Fig. 5), or even specially designed auxiliaries (TAD Bite Opener Auxiliary, American Orthodontics, Sheboy- gan WI; Fig. 6). As an alternative, miniscrews can be placed in the posterior max- illa and used to support an anterior intrusion arch (e.g., Ricketts’ utility arch) or sectional intrusion arms via indirect anchorage. The same types of mechanics can be applied to hyper-erupted mandibular anterior teeth or to both maxillary and mandibular incisors for patients who exhibit severe enamel wear (functional or dysfunctional [bruxism] attrition, especially if accelerated by acidic beverages, acid reflux or anorexia/bulimia) and who have a corresponding lack of clearance for restoration. In these instances, intruding incisors to produce a proper overbite/overjet also will provide the space necessary for prosthetic or esthetic restoration of these damaged teeth (Figs. 7 and 8). 347 Thinking Outside the Box Figure 5. An adolescent male with a deep overbite was reluctant to comply with the use of headgear and chose instead the insertion of an IMTEC TAD between the maxillary central incisors at the mucogingival junction. The TAD provided direct anchorage for adequate intrusion of anterior teeth, using an alastic module. This was accomplished in 12 months; complete treatment time was 21 months. Unfortunately, miniscrews that are placed between the incisor roots near the vestibule may be subject to soft tissue tension from a muscle frenum or the buccal mucosa may become irritated and eventually cover the implant. As a result, closed traction may be a better alternative in these locations (Kim et al., 2006). In these instances, a Monkey Hook (Ameri- can Orthodontics, Sheboygan, WI; Bowman and Carano, 2002) can be looped around the miniscrew when it is inserted. The other “hook” end will exit the Soft tissue to permit easier application of forces (Bowman, 2006; Fig. 8). So it appears that we can intrude incisors and molars, but can we take this a step further? Paik and colleagues (2003) demonstrated that maxillary vertical excess might be improved by differentially intruding the entire maxillary dentition, a procedure that was once thought only to be within the realm of the oral surgeon. ALTERING THE EXTRACTION DECISION The most divisive and persistent argument throughout the history of orthodontics has been whether or not to extract teeth (Angle, 1907; Case, 1911). For patients who present with some degree of crowding 348 Bowman Figure 6. As an alternative to a J-hook high-pull headgear, an IMTEC TAD was placed between the upper central incisors to provide indirect anchorage for a TAD-supported auxiliary (TAD Bite Opener, American Orthodontics) designed by the author. If a large or low midline frenum is present, a frenectomy (to in- clude the fibers between the incisors and extending posteriorly to the incisive papilla) also may be useful in retaining closure of the diastema. Adequate bite opening was achieved in nine months. 349 Thinking Outside the Box º - - º Figure 7. An adult female presented with decalcification and substantial enamel loss on the lingual surfaces of the maxillary anteriors and labial surfaces of the mandibular incisors. No restoration of these teeth could be accomplished without opening of the deep bite. Three TADs (ACE MTAC) were used as direct anchorage. Elastic chain attached from each TAD to the archwire pro- duced intrusive forces in both dental arches. Bite opening required 12 months. sal edges and lingual surfaces of the maxillary anterior teeth. Substantial bite opening was required to achieve adequate clearance for closure of diastemae and for subsequent restoration of these teeth. A fixed acrylic bite plane to as- sist in anterior bite opening was not tolerated by the patient. Three TADs (tomas pins) were inserted: one between the upper central incisors and one each between the right and left lower central and lateral incisors. Tissue 350 Bowman and/or protrusion, the question is not whether to extract, but when and which teeth (even if only third molars)? The instability of expansive treat- ments to avoid extraction has been examined repeatedly and reaffirmed (Little et al., 1990; O’Grady, 2003), yet we continue to [re-] introduce new ways of squeezing all teeth into dental arches, encroaching on the enveloping muscular equilibrium, and “filling” the face and smiles with teeth to over-flowing. All of this, in the hopes of avoiding the extraction of premolars, often insures the removal of third molars and the use of “permanent” retention, permanently. What is this Pecksniffian trade-off actually worth? p Expanding younger (with jackscrew appliances) or older (with “slippery” braces and wide wires) patients is not an insurance policy for better stability or esthetics (e.g., buccal corridors or profile). We seem easily enticed into buying magic braces, “truly” lighter wires or old appli- ances with new tricks (e.g., tissue-engineering expanders; Straight Talk, 2003), all with the promise of better treatments through avoidance of ex- traction. The hype is new, but patient biology hasn’t changed. Full Face or Bald Face Orthodontics? Many within our specialty profess that there is a tacit understand- ing that expansion of some design is required to correct nearly any Angle classification of malocclusion. Some would have patients believe that ex- pansion (ne: lack of extraction) is the only treatment that will produce the desired “full face” and Hollywood smile (Straight Talk, 2003; fullface- global.com, 2007; damonbraces.com, 2007). Yet, if we take a moment to evaluate the desired “look” within the faces of those who populate the runways and red carpets, we find that they may have full lips, but they also manifest “flatter” profiles — without the assistance of extraction ortho- dontics (e.g., Angelina Jolie, Paris Hilton, Gisele Bündchen, Milla Jovov- ich, Katie Holmes, Jessica Garner, Nick Lachey, Jessica Simpson, Prince William, Halle Berry, Anna Nicole Smith, Charlize Theron, and George Clooney). 24 ~ Figure 8 (Cont.) irritation warranted the addition of a Monkey Hook to the upper TAD to facilitate the application of elastic forces to intrude the maxillary incisors. A square sectional wire was inserted between the cross-slots of the mandibular tomas pins and was retained by a bead of light-cured adhesive applied over the wire. Elastic thread was tied around the sectional wire and also the base archwire to intrude the hyper-erupted mandibular incisors. Bite opening to permit restora- tion of the incisors was achieved in 14 months. 351 Thinking Outside the Box Bimaxillary protrusions certainly seem to be in the minority in these circles. In fact, those with the most popular “wide, Hollywood” smiles (Brad Pitt, Angelina Jolie, Farrah Fawcett, Cameron Diaz, George Clooney, and above all, Julia Roberts) also display the largest “negative spaces” (Bowman and Johnston, 2007). It would seem, then, all the more questionable to promote nonextraction treatments, especially the unstable expansive ones, with the intent of preventing “dark corridors.” This is especially true when smile esthetics for extraction and nonextraction treat- ments have been clearly shown to be equivalent (Boley, 2001; Bowman and Johnston, 2002; Gianelly, 2003; Kim and Gianelly, 2003; Munoz-Morente and Ferrer-Molina, 2004a,b) and when the common folk (the end-users of orthodontic services) are not particularly discerning or concerned (Roden- Johnson et al., 2005; McNamara et al., in press). Maximum Retraction The most obvious application for miniscrew anchorage is for those patients who present with both severe crowding and protrusion, as their treatment plan most often requires absolute anchorage and maximum retraction. When using traditional orthodontic mechanics in these situ- ations, crowding is resolved but anchorage may be lost before any sig- nificant change in protrusion can be achieved; e.g., the Class II crowded patient whose treatment includes extractions and whose discrepancy is resolved completely but whose molars remain Class II. All manner of anchorage support has been designed and attempted, with limited predict- ability, throughout our history (headgear, tip backs, setting anchorage, lin- gual and palatal arches, Nance holding arches, etc.). Patients exhibiting severe crowding and/or protrusion are the most obvious patients for whom TAD-supported differential forces in either or both arches may improve the predictability of traditional mechanics. Maintain Incisor/Lip Position Sometimes substantial space is required to resolve dental crowd- ing, but no change in incisor angulation or anteroposterior position of the anterior teeth is desired. In this scenario, miniscrews can provide anchor- age to predictably retract teeth just enough to eliminate the arch-length discrepancy. These screws then also can support subsequent protraction of the posterior teeth to close any residual spaces: no muss, no fuss. Un- fortunately, many of our detractors conveniently have forgotten that ortho- dontists can move teeth in both directions. 352 Bowman Extract Which Teeth? Can the advent of TAD-based mechanics make a difference in the selection of teeth for extraction? Occasionally, compromises are re- quired when teeth are selected for extraction. For instance, viable, “vir- gin” first premolars often have been sacrificed in deference to “canalled- cored-crowned” second premolars, especially in situations of maximum anchorage or severe space constraints. “Bombed-out” first molars have been maintained, while freshly erupted premolars were removed. Sec- ond premolars were extracted with the intent to limit anterior retraction or to facilitate posterior protraction. All of these decisions may need to be rethought in a world with miniscrew anchorage and efficiently applied directional forces. There should be no fear of extracting premolars if properly de- signed mechanics are at work (Bowman, 2006). If, however, retraction begins with no real objective or goal in mind, the consequences of ef- ficient TAD-based mechanics could be disastrous esthetically. It would seem that the use of the visual treatment object (VTO; Ricketts et al., 1982) should enjoy a renaissance in the age of miniscrews, as predictions of tooth movement now may be reasonably accurate and relevant for a change. The bottom line: miniscrew anchorage finally should eliminate the age-old concern of adverse facial changes due to extraction, as spaces can be closed predictability while maintaining or even enhancing specific incisor and lip position. Borderline Extraction There is no proof that there are any better alternatives for pro- ducing the amount of space that the extraction of premolars provides for patients who need it, i.e., those with crowding and/or protrusion. But, what about the borderline extraction case? Can the extraction decision be altered because of the availability of miniscrews? Some degree of dis- talen masse movement (i.e., bodily retraction) of both the maxillary and mandibular dentition has been reported (Park et al., 2004, 2005). Tak- en one step further, could minor crowding (3 to 4 mm) be resolved by simple TAD-based retraction without employing questionable two-phase bimaxillary expansion, interproximal reduction or extractions of pre- molars? Perhaps even the extraction of a mandibular incisor could be avoided in some instances. The limitations of available posterior space (e.g., third molar space), the effectiveness of this type of retraction, and the long-term stability of “backwards-pulling mechanics” are yet to be 353 Thinking Outside the Box explored. As a result, TAD-based bimaxillary retraction as a non-extrac- tion alternative should be approached with cautious optimism. Conservative Resolution of Crowding: Leeway Space Leeway space is “the differential in tooth widths between decidu- ous and permanent buccal teeth” (Nance, 1947; Adams, 1964). During the transition to a permanent dentition, this space unfortunately is lost due to mesial drift of the first permanent molars. If the leeway space can be maintained, Gianelly (2003) has suggested that crowding for at least 77% of patients who experience crowding but who possess favorable profiles may be resolved without expansion or extraction and that the result may be stable (Dugoni et al., 1995). Some clinicians have recommended us- ing a simple mandibular lingual arch or lip bumper to assist in Saving this space, but both are somewhat unpredictable (Dugoni et al., 1995; Turpin, 2000; Gianelly, 2003). Could the introduction of TAD-supported anchorage for the man- agement of the leeway space provide a more predictable and efficient method for resolving borderline crowding without carrying out extrac- tions, possibly unstable expansion, or lower incisor proclination in a sin- gle-phase of orthodontic treatment? Mixed dentition patients who pres- ent with leeway space that is adequate for resolving mandibular crowding may benefit from TAD-supported treatment. Treatment is initiated just prior to the exfoliation of the mandibu- lar second primary molars. Miniscrews are placed between the mandibu- lar first and second molars if adequate interradicular bone is available (Fig. 9). As the primary molars are lost or extracted, elastic or coil spring forces are applied directly from the TADs to retract the mandibular first premo- lars into the leeway space as the second premolars are erupting. TADS also could be tied to the molars as indirect anchorage for retraction forces applied from those molars to the premolars. If second molars are unerupted or the bone density is poor between the molars, an alternative implant site should be considered. Miniscrews can be placed between the mandibular lateral incisors and canines. A jig with a compressed open-coil spring can be constructed from each TAD to push the first premolars posteriorly into the leeway space (Fig. 10). As a fourth alternative, a supporting arm can be placed from each TAD to the first molars to provide indirect anchorage for retraction of the premolars (Fig. 11). After the resolution of the mandibular irregularity, the mandibu- lar TADs also can be used to counteract adverse reactive forces from any necessary Class II mechanics (e.g., Class II intermaxillary elastics, fixed functional appliances). 354 Bowman Figure 9. Just prior to the exfoliation of the mandibular second primary molars, two IMTEC TADs were placed between the mandibular first and second molars at the mucogingival junction. The TADs provided direct anchorage for the retrac- tion of the first premolars into the leeway space during the eruption of the second premolars. The TADs then were ligated to the anterior teeth to help resist any labial flaring. Resolution of mandibular crowding was achieved in a single-phase treatment of 11 months, without extraction or potentially unstable expansion. Figure 10. Compressed coil spring jigs, fabricated from 0.18° stainless steel, Were inserted through the heads of two IMTEC TADs. These jigs were used to push the mandibular premolars into the leeway space to resolve anterior crowd- ing. Lexan beads, used with Jasper Jumpers, served as stops to prevent the coil Spring from migrating up the bayonet bend. Forces were applied, via a couple. closer to the center of resistance in order to provide more bodily movement. Once the first premolars were distalized into the leeway space up to the erupting Second premolars, the jigs provided indirect anchorage for subsequent retraction of the remaining teeth; they also could be used to resist labial flaring if Class II mechanics (e.g., intermaxillary elastics or fixed functional) were needed. 355 Thinking Outside the Box Figure 11. Two Aarhus TADs were placed in the anterior mandibular alveolus for indirect anchorage support of the first molars. Sectional wires (.018" x 018”) extended from the TADs to the molars to maintain the leeway space as crowding was resolved. Secondary Use: Support for Class IIs Regrettably, all fixed functionals tend to produce adverse labial flaring of mandibular incisors (Ruf et al., 1998; Rothenberg et al., 2004). This may give way to either a detrimental effect in lip posture, a reduction in the amount of mandibular advancement that is possible, or inherent in- stability. AlQabandi and colleagues (1999) reported that 6° to 7° of lower incisor flaring occurs even when simply leveling the curve of Spee. As a consequence, many pre-adjusted appliance prescriptions feature lingual crown torque to counteract this effect (Bowman and Carano, 2004). It ap- pears that miniscrews used efficiently make use of leeway space also may be used to resist flaring or bodily labial movement of the lower incisors during traditional Class II mechanics. CLASS II MALOCCLUSION Next to crowding, Class II is the second most prevalent maloc- clusion presenting for orthodontic treatment. The resolution of Class II malocclusions involves pushing the maxilla or maxillary dentition posteri- orly and/or advancing the mandible. Miniscrew-supported anchorage can facilitate any of these alternatives. Class II: Maxillary En Masse Retraction Some degree of distal en masse movement of the dentition us- ing TAD-supported anchorage has been demonstrated for Class I nonex- traction patients (Park et al., 2004). Taking possible en masse movement a step further, what about the possibility of distally retracting the entire maxillary dentition far enough to correct a Class II relationship? 356 Bowman Jeon and colleagues (2006) published a case report of Class II nonextraction distal en masse retraction of the maxillary dentition. Park and his colleagues (Park and Kwon, 2004; Park et al., 2005) published both a case report and results for 13 patients for whom both maxillary and mandibular en masse retraction was accomplished, demonstrating a 90% miniscrew survival rate. In these situations, TADs were placed in the buccal alveolus between the roots of the molars and premolars for the expressed purpose of distalizing or en masse movement of the entire max- illary dentition into a Class I relationship (Figs. 12 and 13). Figure 12. An adolescent female with a Class II malocclusion, a congenitally- missing maxillary left lateral incisor, and significant maxillary midline deviation (ala Tom Cruise or Cary Grant) was treated with Class II distal en masse move- ment supported by direct anchorage from two KLS Martin TADs. A space- closer alastic module, elastic chain, and eventually a TAD-supported Jones jig Were used to produce a Class I molar and canine relationship on the left side. On the right side, direct support for distal en masse movement assisted correction of the midline. Opening of adequate space for future prosthetic replacement of the missing left lateral incisor using an open-coil spring was achieved in five months, but some overjet increase occurred. If the incisors simply had been tied to the TADs during distalization/space opening, the “roundtrip” for the incisors could have been avoided. It is important to be aware of the effect of reciprocal forces, as TADs may be used for dual purposes in orthodontic mechanics. 357 Thinking Outside the Box Figure 13. A sixteen-year-old female with a unilateral Class II relationship and associated midline deviation was treated using TAD-supported maxillary distal en masse retraction. One IMTEC TAD inserted between the first molar and second premolar (at the mucogingival junction) was used for direct anchorage. It would seem logical that the degree of retraction of the upper posterior teeth would be limited, especially when implants are inserted between roots. When queried about this concern, Park (speaking at the 106" Annual Session of the American Association of Orthodontists) stat- ed, “Mostly we don’t run into the roots . . . mostly.” In the popular sci- ence-fiction film, Aliens, the little girl, Newt, provided a warning that the creatures, “mostly come at night . . . mostly.” Neither statement instills substantial confidence. Therefore, if touching roots during the retraction process is a concern, we may need to look for an alternative. For example, if a particular patient needs more than simple distal rotation of a partially- Class II maxillary molar or more than just a distal “nudge” of 1 or 2 mm. separately pushing only the molars posteriorly as a first step (i.e., molar distalization), rather than en masse retraction, might be a consideration. 358 Bowman Class II: Molar Distalization Maxillary molar distalization has become a popular adjunct for Class II correction. Numerous gadgets have been introduced over the years, all designed to push maxillary molars back into a Class I relation- ship. Despite their popularity, most methods have some associated draw- backs that often include anchorage loss or dependency on unpredictable patient compliance. Reducing these two negative aspects lead directly to the incorporation of miniscrew anchorage in distalization mechanics (Kyung et al., 2003; Kinzinger et al., 2005; Chang et al., 2006). Anchorage Loss. One of the most documented and reliable devic- es for molar distalization has been the Distal Jet (Bolla et al., 2002; Fergu- son et al., 2005; Carano and Bowman, 2006). As the maxillary molars are pushed back with the Distal Jet, spaces tend to open anterior to the molars. Most of this space is due to the distal movement of the molars. Reciprocal forces directed to the premolars, which are included in the construction framework, resulted in 15% to 55% anchorage loss (Bolla et al., 2002). More anchorage loss and 10° of incisor flaring was noted when the Distal Jet was used during leveling with maxillary pre-adjusted brackets (Bolla et al., 2002; Ferguson et al., 2005). Consequently, there appeared to be no advantage to placing maxillary braces until distalization was finished (Bolla et al., 2002; Ferguson et al., 2005; Carano and Bowman, 2006). These clinical findings confirm the suggestion that there is no anchorage value to previously mobilized teeth (Melsen and Bosch, 1997). Improving anchorage support with TADs for either molar distalization or mandibular advancement (e.g., fixed functional) in correcting Class IIs helps to reduce the negative effects of each. . TAD-supported Distalization. Escobar and colleagues (2007) reported no anchorage loss with a TAD-supported Pendulum distalizer. However, the time required for molar correction (7.8 months) and the amount of molar tipping (11.3°) was not reduced (Bolla et al., 2002). Ön- cag and colleagues (2007) described the results of incorporating an osseo- integrated implant with a Pendulum, but they also found significant molar tipping and poorly-matched molar marginal ridge heights. Since implants were inserted through the Nance palatal button of the appliance, there was still a concern for soft tissue inflammation. In addition, if the implant would have failed prematurely, the entire device might have needed to be refabricated to permit implant replacement in a new site. Miniscrews have been placed in the anterior palate as part of the construction of the Distal Jet (Figs. 14 and 15) and other distalization 359 Thinking Outside the Box devices (Kyung et al., 2003; Gelgór et al., 2004; Kinzinger et al., 2005; Bowman, 2006; Chang et al., 2006; Kinzinger et al., 2006; Escobar et al., 2007; Öncag et al., 2007). Although there are no roots to contend with, the persistent and intermittent forces from the tongue could contribute to more frequent failure of the miniscrew. For these reasons, the TAD also can be placed posterior to the appliance and then tied to it with a stainless steel ligature wire (Bowman, 2006; Fig. 14). The stability of the screw can be tested easily in this configuration, and, if necessary, it can be removed easily and replaced without fabricating a new appliance (Bowman, 2006; Kinzinger et al., 2006). Inserting miniscrew implants between the maxillary first molar and second premolar or between the two premolars, either on the buccal or lingual (Fig. 14) of the alveolus, is another option (Bowman, 2006; Carano and Velo, 2007; Velo et al., 2007). After distalization has been achieved, the miniscrews will need to be removed and replaced in another location (e.g., between the first and second molar or just mesial to the distalized first molar) as the roots of the second premolars cannot be retracted past the original miniscrew position – much the same situation as described for screws placed in the buccal alveolus. A Better Alternative. Anka (2007) has suggested that a more fa- vorable TAD insertion point would be on the palatal side of the alveolus, between the maxillary first molars and second premolars (Fig. 16). Pog- gio and colleagues (2006) reported that this area had the largest amount of interradicular bone on either side of the maxillary alveolus. When the miniscrew is angled (30° to 45°) to the sloping surface of the alveolus, the cortical bone is from 1.7 H= 0.5 mm to 2.2 + 0.4 mm thick for adults, which is sufficient for miniscrew support (Deguchi et al., 2006). Sonis (2007) found a similar amount of cortical bone (about 1.7 mm) for adolescents; patients who would benefit most often from this type of Class II treatment (Fig. 17). Another advantage of this lingual site is that the palatal root of the maxillary second premolar often is angled buccally, away from the miniscrew. In addition, the palatal root of the first molar often is rotated posteriorly, providing substantial space between the roots of these two teeth. This may result in: 1) less potential for iatrogenic damage when inserting screws; 2) the ability to place a miniscrew more distal, closer to the palatal root, thus providing more space for premolar retraction be- fore a screw could be encountered; and 3) the second premolar root being more likely to miss the lingually-positioned miniscrew during distaliza- 360 Bowman Figure 14. Multiple versions of TAD-supported Distal Jet appliances (Gero Kinzinger and Stefano Velo contributed photographs). tion and subsequent retraction of the other teeth. In other words, the Screws may not need to be moved to a different position after distalization or when the remaining teeth are retracted. The design of the Distal Jet appliance (Horseshoe Jet, AOA Labo- ratories, Racine, WI) has been modified so that it completely relies on palatal TADs for anchorage (Bowman, 2006; Fig. 16). However, premo- lar support wires also may be incorporated to reduce the potential of tip- ping of the molars. Unfortunately, adding dental support from the pre- molars appears to contribute to anterior anchorage loss due to the inher- ent flexibility of the appliance construction (Fig. 16). Because there is more favorable bone, more attached gingiva and less likelihood of touch- ing a root at this palatal insertion point, there may be a lower incidence of TAD failure. Only a profound topical anesthetic (e.g., 20% TAC Al- ternate) may be required to place TADs in this location, although some patients might require a typical dental infiltration anesthetic. This is in Contrast to the often painful incisive foramen injection required when placing TADs in the anterior palate. Maino and colleagues (2006) also discussed the advantage of using miniscrews in this same lingual alveo- lar location, but their anchorage system required support from the first 361 Thinking Outside the Box Figure 15. Treatment was started for an adolescent male with a Class II, divi- sion 1 malocclusion and deep bite using a TAD-supported Distal Jet appliance. Two IMTECTADs placed in the anterior palate between the canines and lateral incisors were tied with stainless steel ligatures to a skeletonized Bowman modi- fication appliance (AOA Laboratories, Racine, WI). A “super-Class I,” over- corrected molar relationship resulted in seven months. Leveling, bite-opening, and a Class I relationship was achieved in 12 months. Only simple maxillary space closure remained. The TADs reduced the reciprocal anchorage loss that normally would be seen with the Distal Jet. premolars and forces were applied at the height of the crown of the molars, which could result in more tipping. The acrylic Nance button of the original Distal Jet has been elimi- nated for the Horseshoe Jet. Anchorage is derived from miniscrews tied to hooks on the horseshoe-shaped tracking wire using stainless steel liga- ture wire (Fig. 16). At the completion of distalization, the distal set Screw is locked onto the tracking wire to stop the process (Fig. 18). The open coil spring is not removed, as must be done when converting the original Distal Jet. However, if premolar supporting arms are used, they must be sectioned using a crosscut fissure or diamond bur (Fig. 18). In this manner, TAD-supported anchorage from the Horseshoe Jet is available during both molar distalization and subsequent retraction of the remaining maxillary teeth: one TAD-based appliance serves two purposes (Bowman, 2006). 362 Bowman - - - | - º - - - - - - Figure 16. The Horseshoe Jet is supported by two TADs inserted at an angle into the lingual slope of the maxillary alveolus and tied with stainless steel ligatures to hooks on the tracking wire. Since the root of the second premolar is angled buccally and the first molar has only one palatal root, there is less concern for iatrogenic damage to the roots when inserting the implants and during subse- quent retraction of the second premolar. During distalization, the mesial lock- ing collar also may be rotated and abutted against the distal of the TAD. Class II: Maxillary Extraction and Retraction If maxillary molars are in a solid Class II intercuspation and there is no desire to change that position, but there is substantial crowd- ing and protrusion, anchorage control is paramount for “camouflage treat- ment” involving the extraction of maxillary premolars. Considering the predictable directional forces that accompany TAD-anchorage, the pro- trusive Class II patient with a deficient mandible probably warrants the most careful assessment in terms of possible soft tissue change due to treatment. Three alternatives are possible: orthognathic surgery, molar distalization or extraction of upper premolars. Although the labial and nasolabial angles tend to open after incisor retraction, there is limited 363 Thinking Outside the Box Hiºdºſſi sºººººººº. º º jº º 'ºnd Premolar tº 21 ºº: ºmºsº Molar - Implant Locº º ººm with Best Access Figure 17. The lingual alveolus between the maxillary second premolar and first premolar is a favorable site for miniscrew insertion. There appears to be adequate cortical thickness and a large interradicular space (CBCT scan courtesy of Andrew Sonis). Figure 18. To begin distal molar movement with the Horseshoe Jet, the posterior hex screw is loosened A turn counterclockwise. The anterior activation collar is pushed back to compress the superelastic coil spring and the hex screw is locked onto the tracking wire. Only after a Class I molar relationship is achieved is the posterior hex screw locked down onto the tracking wire. The two locks help to prevent mesial movement of the molars. The premolar supporting wires are sectioned using a handpiece. Note: The superelastic coil springs do not have to be removed. The resulting TAD-based holding arch also provides anchorage for retraction of the other teeth. 364 Bowman predictability to this response (Ramos et al., 2005); in fact, these changes may not be seen categorically as negative (Bowman and Johnston, 2000). More detailed informed consent regarding the risk/benefit ratio for these treatment alternatives should be considered before embarking on any one of these three paths. Direct or indirect TAD anchorage support can be used for anterior retraction and overjet/overbite reduction. Specifically, en masse retraction and intrusion of the canines and incisors can be accomplished using TADs (Figs. 1 and 19). Once the canines are positioned into a Class I relation- ship, reciprocal space closure is initiated and can be supported by bracing the TADs with a sectional wire abutted against the canines to prevent any further anterior retraction. Figure 19. An adult female whose chief complaint was protrusion and lower crowding. Maxillary first premolars were extracted and two IMTECTADs were placed between the first molars and second premolars. The TADs were used as direct anchorage for intrusion and retraction of the entire anterior segment using sliding mechanics. A Class I canine relationship and favorable overjet had been achieved after 17 months, so reciprocal space closure was initiated and treat- ment was completed in 24 months. MAXIMUM ANCHORAGE The most obvious application for TADs is for patients with Se- Verely crowded and/or protruded dental arches (Costa et al., 1998). These type of miniscrew-supported mechanics specifically brought 365 Thinking Outside the Box Korean orthodontists (Park et al., 2001) to the forefront of the TAD revo- lution. Reducing bimaxillary protrusion and improving facial and dental esthetics with the extraction of premolars and retraction of anterior teeth can be enhanced significantly using TADs. Using TAD-supported, en masse retraction for all anterior teeth (canines and incisors), rather than first retracting canines, improves the efficiency of this type of treatment (Figs. 20 and 21). Park and Kwon (2004) described TAD-supported sliding mechanics for retraction; how- ever, “frictionless” closed-loop mechanics also can be adapted easily for direct or indirect miniscrew support (Bowman, 2006). Figure 20. An adolescent male with a Class II malocclusion and severe arch length discrepancy, deep bite, and midline deviation. Two KLS Martin TADs were placed between the maxillary first molars and second premolars to pro- vide direct anchorage for 1) resolution of anterior crowding and 2) differential management of the midline. ATAD-anchored overlay (or piggyback) wire was inserted into the headgear tube and then bent over the miniscrews. This wire featured gable bends for intrusion of the anterior teeth. The midline and over- bite were resolved in ten months, the TADs were removed at 19 months when all spaces were closed, and treatment was completed in 21 months. 366 Bowman Figure 21. An adolescent male with a Class III tendency and severe arch length discrepancy was treated with extraction of four first premolars. Two KLS Mar- tin TADs were inserted between the mandibular first molars and second pre- molars to provide direct anchorage for resolution of lower crowding and the midline, which was accomplished in 14 months. - TADs also may be used to support treatment with clear aligners like Invisalign. Intra-arch or interarch elastics can be applied from the TADs to notches cut in the aligners using a ligature cutter or to buttons attached to either the teeth or the aligners. Miniscrew anchorage assists With very mild en masse movements, support for space closure and, most importantly, by providing positive pressure for proper seating and tracking of the aligners (Fig. 22), especially when combined with active seating of the trays with Aligner Chewies (Glenroe Technologies, Bradenton, FL; Bowman, 2006). OPENBITE Anterior openbite is perhaps the most insidiously difficult mal- Occlusion to correct and retain. An openbite also can occasionally arise 367 Thinking Outside the Box Figure 22. Open extraction sites, crowding and deep overbite remained from past, incomplete orthodontic treatment for an adult female. Two IMTECTADs (with healing caps) were placed between the maxillary first molars and second premolars to provide indirect anchorage support for 1) space closure/retraction, 2) anterior intrusion and 3) proper tracking of Invisalign trays. “Class I” intra- maxillary elastics were attached from the TADs to “flaps” cut into each aligner tray. during treatment as an unanticipated and unwelcome guest. Resolution of an anterior openbite requires extrusion of anterior teeth and/or intrusion of posterior teeth. Can miniscrews facilitate the intrusion of posterior teeth or perhaps selective extrusion of either anterior or posterior teeth as well? Molar Intrusion Kravitz and colleagues (2007) reported that supra-erupted max- illary molars could be intruded 3 to 8 mm in 7.5 months (about 0.5 to 1.0 mm/month) using TAD-anchorage without loss of vitality, periodon- tal damage or root loss (Fig. 1). When intruding a hypererupted tooth, care must be taken to evaluate the level of the interproximal crestal bone (Park et al., 2003; Yao et al., 2004). If there has been periodontal loss around the tooth selected for intrusion, an angular crest will be pro- duced with the possible consequence of additional bone loss (Van- arsdall, 2007). On the other hand, if the periodontium has followed the hypereruption, the bone also will follow subsequent intrusion and produce a more level crestal bone height. Kanzaki and colleagues (2007) found that “pressure from the supra-alveolar fibers [using skeletal anchorage 368 Bowman system] . . . induced alveolar bone crest resorption and remodeling, and as a result, it prevented deepening of the gingival pocket.” Another concern when intruding a molar is that the length of the attached gingiva will be diminished. Although the gingival margin moves apically with the intruded molar, the mucogingival junction does not. As a result, case selection for intrusion should involve careful evaluation of the length of the attached gingival along with an examination of bone height. Intrusion to Rotate the “Great Planes" There have been several published case reports demonstrating openbite closure via molar intrusion with miniscrews (Kuroda et al., 2004; Lee et al., 2004; Park et al., 2004; Choi et al., 2007). Xun and colleagues (2007) also reported successful closure of openbite for 12 patients using similar mechanics. The molars were intruded using direct anchorage from miniscrews placed between the molars. It appears that about 0.7 mm of molar intrusion can be produced per month and 3° of mandibular autorota- tion typically accompanies each millimeter of molar intrusion. As a result, Some spontaneous closure of an anterior openbite typically occurs with intrusion of the posterior teeth (Fig. 23). “Rolling-out” or buccal crown tipping may result when mini- screws in the buccal surfaces of the alveolus are used to direct molar intru- sion. There are two alternatives to avoid this adverse side effect: 1) a pair of miniscrews, one on the buccal and one on the lingual, can be used for balanced intrusion; and 2) a transpalatal or lingual arch can be placed if screws are inserted only in the buccal alveolus of either the maxilla or the mandible, respectively. It does not appear that any special splints or bulky appliances need to be fabricated to achieve this simple intrusion. Unfortunately, Kuroda and colleagues (2007) have reported a 30% relapse for TAD-supported intrusion. This is similar to the relapse rate of other methods of openbite closure (both surgical and nonsurgical). Therefore, over-correction by 30% is recommended. Interestingly, actu- ally achieving over-correction is more predictable when using TADs. Beyond openbite closure, the management of the vertical dimen- Sion is an important and sometimes challenging aspect of orthodontic mechanics (Schudy, 1964; Chaffee, 2007; Vanarsdall, 2007). As a curi- ous aside, Mew (Straight Talk, 2003) has accused orthodontists of rou- tinely increasing the vertical dimension (rather than encouraging “for- ward facial development”), thereby, diminishing facial esthetics. In con- trast, it also has been recommended that we should increase the vertical 369 Thinking Outside the Box Figure 23. Class I bimaxillary protrusion with crowding and an anterior open bite necessitated the extraction of first premolars. Four KLS Martin TADs were placed at the mucogingival junction between all first and second molars. Elastic chain was stretched from the canines over the occlusal of the molar tubes on the first molars, and then apical to the TADs. This produced direct anchorage support for retraction and intrusion of the first molars. Significant anterior bite closure was achieved in three months, at which time the intrusive component of force was discontinued. dimension specifically for esthetic enhancement (www.sarverortho.com, 2007). Is either correct? Traditional Orthodontic mechanics have been used to at least main- tain or perhaps produce counterclockwise rotation of the occlusal plane to avoid “downward and backward” rotation of the mandible (Fig. 24). No matter the practitioner's intent (increasing or decreasing the vertical di- mension), improved and more predictable control for either alternative is possible using TAD support. Extrusion to Close Openbite In some instances, extrusion of anterior or posterior teeth may be required to close an openbite. To date there have been few devices de- signed to extrude teeth using forces that were directed apical to the oc- clusal plane to the teeth. Two such extrusive TAD-based auxiliaries, the propeller arm (Fig. 25) and the Ulysses spring (American Orthodontics. Sheboygan, WI; Fig. 26), were developed by Anka and Bowman (BOW- man, 2006). In some instances, a combination of miniscrew-supported 370 Bowman Figure 24. An adolescent female with a Class I malocclusion featuring severe crowding and an obtuse mandibular plane angle necessitating control of the ver- tical dimension. After the extraction of first premolars and placement of fixed appliances, the bite became “propped-open” as anticipated. Four KLS Martin TADs were placed between all first and second molars. Alastic modules were Stretched from the first molar tubes to the TADs to prevent molar eruption and reduce anchorage loss during resolution of anterior arch length discrepancy. Significant intrusion of the molars occurred by the end of three months resulting in a posterior openbite. - - posterior intrusion and anterior extrusion may be required to close an Openbite, improve the smile line or occlusal plane, or merely maintain the mandibular plane angle. UPRIGHTING OR PROTRACTION There are a number of uprighting and protraction mechanisms that are prevalent in contemporary orthodontics including those used for: uprighting molars, uprighting and intruding molars, uprighting and erupt- ing ectopic or impacted molars, and protracting while maintaining upright molars. If, in fact, we are protracting molars, how far can we go? For instance, can we eliminate the need for prosthetic replacement of missing premolars or molars using TAD anchorage? There certainly are ramifica- tions in terms of root resorption, amount of alveolar ridge, and periodontal Status of the tooth in question. Just because “we can” doesn’t mean that We always should. 3.71 Thinking Outside the Box Figure 25. Maxillary midline TAD placed after frenectomy. A short prototype propeller arm extrusion spring was used to close the openbite. Cosmetic bond- ing of the narrow lateral incisors was completed after orthodontics. - - - Figure 26. Ulysses spring auxiliary (American Orthodontics, Sheboygan, WI) was compressed between an IMTEC TAD to close a lateral open bite. The most obvious applications for TAD-supported uprighting of teeth are for instances of mutilation. For example, uprighting a second molar may be accomplished to permit the prosthetic replacement of a 372 Bowman missing first molar with a dental bridge or implant (Park et al., 2002; Giancotti et al., 2004; Gracco et al., 2007). Other related TAD-supported possibilities include: 1. protracting first molars through the sites of congenitally miss ing second premolars (Bowman, 2006; Fig. 27); 2. protracting second molars through the sites of previously ex- tracted first molars (Kyung et al., 2003; Fig. 28); 3. resolution of ectopic eruption by uprighting or protracting (e.g., impeded second molars; Fig. 29); 4. uprighting partially transposed teeth; and 5. protracting or uprighting anterior teeth to resolve an anterior crossbite, reduce an overjet or unilaterally correct a midline deviation (Fig. 30; Bowman, 2006). Figure 27. An adolescent male with congenitally missing mandibular second premolars. The mandibular molars were protracted using NiTi coil springs Supported by TADs placed in the buccal alveolus. The archwire was inserted through the eyelet of a superelastic coil spring that then was, in turn, hooked onto the lingual cleat of the molar. A stainless steel ligature also was placed through the eyelet and was used to stretch the coil spring mesially. Then the ligature was tied to the TAD to maintain the spring activation to provide coun- ter-rotational force. In this manner, no lingual TAD was required, yet there was balanced buccal and lingual protraction produced from a single TAD. 373 Thinking Outside the Box Figure 28. Mandibular first molars required extraction. Protraction of the sec- ond molars, while maintaining the incisor and lip position, was completed in 12 months after the insertion of two IMTEC TADs between the first and Second premolars. Care was taken to prevent mesial rotation and tipping. Molar up- righting arms were placed into the auxiliary tubes on the first molars to reduce molar tipping. Figure 29. An adolescent male with congenitally-missing left maxillary and mandibular first premolar and right mandibular second premolar. Ectopic erup- tion of the maxillary left canine had resulted in a retained primary canine. Two KLS Martin TADs were used for direct anchorage to protract the mandibular molars. A third TAD placed between the maxillary left central and lateral inci- sors served two purposes: 1) direct anchorage to protract the left canine, and 2) indirect anchorage to maintain the midline and support protraction of the left posterior teeth (the “Pushmi-Pullyu" concept). Direct or Indirect Protraction Protracting posterior teeth to close space without some degree of retraction of the anterior teeth always has been an orthodontic challenge. Attempts to maintain the anteroposterior position of the incisors have 374 Figure 30. Propeller arm TAD-based auxiliaries (American Orthodontics. She- boygan, WI). Short version can be used for extrusion and limited protraction. Long version is for protraction in either dental arch and can assist in correction of a midline discrepancy (photographs courtesy of George Anka). included: labial crown torque applied to the anterior teeth, uprighting Springs to push the crowns of canines mesially, torquing auxiliaries, and protraction facemasks. Miniscrews improve the predictability and, there- fore, the utility of protraction mechanics. As an example, molar protrac- tion can be supported by direct anchorage from a TAD placed between premolars, first premolar and canine, or canine and lateral incisors (Figs. 28–31). In these scenarios, there is no stress to anterior anchorage. As an alternative, indirect anchorage support can be derived by placing a vertical section of wire from a TAD (inserted into one of the aforementioned locations) through a crosstube (Dentaurum, Ispringen, Germany) on the base archwire. Protraction forces then are applied from the TAD-supported teeth to the posterior teeth in question. A third possi- bility is to place a “crossbar” supporting arm as direct anchorage to main- tain the midline and also to serve as indirect anchorage for protraction of the posterior teeth along the archwire (Fig. 29). In either director indirect alternatives, control of molar tipping (using power arms as a couple to ap- ply forces closer to the center of resistance: Figs. 28 and 31), reducing mo- lar rotation (using counter-rotational spring or chain from the lingual cleat or button on the molar; Fig. 27), and preventing molar extrusion (limited by the base archwire and forces of occlusion) are key aspects that require Careful planning. Protracting, advancing, or pushing anterior teeth forward is an- other orthodontic mechanism that also benefits substantially from mini- Screw anchorage. Anka and Bowman created a TAD-based protraction arm (“long” propeller arm, American Orthodontics, Sheboygan, WI: Fig. 30) to produce anteriorly directed forces to flare incisors, support protrac- tion of posterior teeth, and to assist in the resolution of midline devia- tions (asymmetries). The compressed coil spring from the propeller arm 375 Thinking Outside the Box Figure 31. One IMTECTAD was used simultaneously to (1) protract the molar into the site of a congenitally-missing second premolar and (2) push the man- dibular dentition to the left to correct the midline discrepancy (“Pushmi-Pullyu" mechanics). is supported by the miniscrew and directed to the base archwire, to a pow- er arm, or directly to specific teeth. Pushmi-Pullyu In some instances, the combination of posterior protraction and anterior advancement may be required. If a mandibular first molar or sec- ond premolar is missing, the anterior teeth may have collapsed lingually with a corresponding increased overjet or a midline deviation. Protraction of the molar along with concurrent uprighting (flaring) and advancement or decompensation of the anterior teeth may be required. One miniscrew may serve both purposes (Figs. 29 and 31). This dual mechanism has been dubbed the “Pushmi-Pullyu" method, named for Hugh Lofting's two- headed animal introduced in the 1948 novel, “The Story of Dr. Doolittle.” 376 Bowman CLASS III AND CROSSBITES Class III: Maxillary En Masse Protraction In milder versions of Class III malocclusions, some degree of maxillary protraction has been used for correction. Protraction facemasks, compressed coil springs (abutted against molars) to push upper anterior teeth labially, and Class III elastics have all been used in the past with varying degrees of success in resolving Class III malocclusions. Placing TADs between teeth in the mid-portion of the maxilla (on the lingual or buccal) can be used to provide direct anchorage to pull the entire dentition anteriorly. For example, protraction elastic forces can be applied from a transpalatal arch to miniscrew(s) inserted into the ante- rior palate (Figs. 32 and 33). As an alternative, screws can be placed in the palatal alveolus between the maxillary first molar and second pre- molar (described previously for molar distalization with the Horseshoe Jet). Elastic chain or coil springs then can be applied from the minis- crews to a transpalatal arch that is constructed from the distolingual line Figure 32. A 14-year-old male with a moderate Class III malocclusion. Elastic chain was connected from a transpalatal arch to two KLS Martin TADS inserted in the anterior palate adjacent to the midsagittal suture to produce maxillary mesial en masse protraction. One TAD failed when the TPA contacted it at six months. A favorable Class I canine and overjet relationship was produced with- Out a protraction facemask or Class III intermaxillary elastics. 377 Thinking Outside the Box - Figure 33. Adolescent female with Class III malocclusion. Three KLS Martin TADS were used to protract the maxillary dentition into a Class I relationship. angle of the first molars. Class III elastics or a protraction headgear may enhance either of these methods. - Another alternative method consists of first producing mesializa- tion of all teeth that are anterior to the molars. These forces are directed using propeller arms (American Orthodontics, Sheboygan, WI) from TADs between the molars or between molars and premolars. Once the desired incisal overjet/overbite has been achieved, the maxillary molars can be slipped forward using Class III elastics, reverse headgear, or indirect TAD anchorage applied to the anterior teeth (e.g., propeller arm). Certainly maxillary en masse protraction is limited by the anterior alveolus and the appropriate esthetic inclination of the maxillary incisors. When combined with some interproximal reduction of the mandibular an- terior teeth or even TAD-supported en masse mandibular retraction (See below), some mild underjet malocclusions may be resolved. Posterior crossbites also may benefit from miniscrews. In a re- cent tomographic evaluation of rapid maxillary expansion, the actual skeletal component was less than 2 mm or only about 50% of the to- tal amount of expansion produced (Tausche et al., 2007). If expansion forces could be supported only by the maxillary bone, perhaps less tip- 378 Bowman ping of teeth and more efficient expansion would result. One method of TAD-supported palatal expansion already has been described for trans- verse discrepancies (Podesser et al., 2007). Future appliance designs and methods are sure to follow. Class III. Mandibular En Masse Retraction If the maxillary dentition can be retracted as a whole unit to cor- rect some mild Class II malocclusions, can the mandibular dentition also be retracted to resolve some Class IIIs? Paik and colleagues (2006) report- ed on the nonextraction resolution of a Class III malocclusion by TAD- Supported en masse retraction of the mandibular dentition (Fig. 34). Taken a step further for patients with a bit more discrepancy, this mandibular retraction could be combined with TAD-based maxillary en masse pro- traction (discussed previously). Figure 34. An adult female's chief complaint was a maxillary midline diastema: however, labially-tipped mandibular incisors precluded anterior retraction to close the space. Two IMTEC TADs were placed posterior to the most distal teeth in the mandibular arch. Space consolidation, uprighting of mandibular anteriors, and mild distal en masse retraction of the entire mandibular dentition Was achieved by direct anchorage support from the TADS, Concurrent retrac- tion of maxillary incisors and elimination of the diastema required 11 months. 379 Thinking Outside the Box Sometimes the extraction of a single incisor is required to improve an underjet or end-on anterior occlusion. Considering that some degree of mandibular en masse TAD-supported retraction is possible, perhaps this method may be used to reduce the incidence of single incisor extraction. Class III. Mandibular Extraction and Retraction Much like the camouflage extraction approach for Class IIs, the extraction of mandibular premolars also has been a common alternative for patients who exhibit a significant underjet or anterior crossbite. This treatment sometimes is offered as an alternative to orthognathic surgery of the upper and/or lower jaw. The difference in esthetic results and the risks/benefits between these two treatment options (surgical vs. camou- flage) must be discussed as part of informed consent. Miniscrews can improve the predictability of the retraction of mandibular anterior teeth (Figs. 35 and 36). However, additional consid- eration must be given to how much retraction is really possible given the thin anterior alveolar ridge. Once canines are in a Class I relationship, reciprocal space closure (or slipping anchorage) is initiated (Figs. 35 and 36; Bowman, 2006). The same TAD-supported mechanics then would be employed to maintain the incisor position when protracting mandibular molars (see above). Figure 35. An adult female presented with an underjet and significant crowding. The extraction of mandibular premolars was selected to resolve both discrepan- cies. Superelastic springs were connected using Monkey Hooks to two IMTEC TADs. Reciprocal space closure began after a Class I canine was achieved at ten months. 380 Bowman Figure 36. The extraction of mandibular first premolars was selected as a camou- flage alternative to surgery. Two KLS Martin TADs were inserted between the mandibular first molars and second premolars. Anterior retraction to a Class I canine and positive overjet was achieved using direct anchorage with Superelastic coil springs and elastic chain. Treatment was completed in 23 months without Class III elastics. TADs improved the predictability of typical treatment mechan- 1CS. 381 Thinking Outside the Box SUMMARY The introduction of miniscrew anchorage in orthodontics has signaled the start of a significant paradigm shift. Traditional orthodon- tic mechanics and treatment options may be altered substantially in many situations when more effective, efficient, and predictable TAD-supported directional forces are used. 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The common appliances used for distalization require varying degrees of cooperation from the patient such as the cervical headgear (Kloehn, 1961; Hubbard et al., 1994; Melsen and Dalstra, 2003), remov- able appliances such as the Cetlin removable plate (Cetlin and Ten-Hoeve, 1983), intraoral appliances (that require some but not complete patient cooperation) such as the repelling magnet (Gianelly et al., 1989; Bond- emark and Kurol, 1992), the Jones jig (Jones and White, 1992), the distal jet (Ngantung et al., 2001; Bolla et al., 2002; Nishii et al., 2002), the pen- dulum (Hilgers, 1992; Ghosh and Nanda, 1996; Byloff and Darendeli- ler, 1997; Byloff et al., 1997; Bussick and McNamara, 2000; Chiu et al., 2005; Chaqués-Asensi and Kalra, 2001; Kinzinger et al., 2004, 2005), first class (Fortini et al., 2004), appliances with superelastic coils for distal tooth movement (Keles, 2001; Keles and Pamucku, 2002; Bondemark and Karlsson, 2005; Mavropoulos et al., 2005), etc. One of the most frequently described appliances for molar distal- ization is the pendulum (Hilgers 1992; Ghosh and Nanda, 1996; Byloff and Darendeliler, 1997; Bussick and McNamara, 2000; Chaqués-Asensi and Kalra, 2001; Chiu et al., 2005; Kinzinger et al., 2004, 2005). Clini- cians have reported that while the distal movement of the molars takes place with the pendulum appliance, an adverse reaction also occurs, i.e., mesialization of the premolars (1 to 2.5 mm) and labialization of the up- per incisors (1.7 to 5.1 degrees). Therefore, the space obtained is a re- sult of 55% to 70% distalization of the molars in the area of action (the 391 Bone-Supported Pendulum amount of maxillary molar distal movement) and of 45% to 30% mesial- ization of premolars and labialization of incisors in the area of reaction (changes in the position of maxillary premolars and anterior teeth). This latter effect can be interpreted as a loss of anchorage due to the fact that the pendulum appliance has a system of support that uses the premolars as anchorage. In order to eliminate the effects of adverse reactions in orthodon- tics, several systems of anchorage such as endosseous fixation have been designed (Creeckmore and Eklund, 1983; Roberts et al., 1984). Different types of endosseous palatal implants have been used to control adverse reactions during orthodontic treatment successfully (Giancotti et al., 2000; Bantleon et al., 2002; Giuliano et al., 2002; Karcher et al., 2002; Karaman et al., 2002; Keles et al., 2003; Gelgor et al., 2004; Carano et al., 2005; Kircelli et al., 2006; Oncag et al., 2007). These systems may present some limitations. • Additional laboratory procedures may be required. • Some devices cannot be loaded immediately following placement because (1) healing needs to take place as result of the invasive surgical intervention required to place the anchorage device or (2) because of the need to wait for Osseous integration to occur. • Finally, the removal of endosseous appliances sometimes requires additional surgical procedures. The use of fixation screws instead of titanium osteointegrated im- plants stems from the need to simplify the placement and removal of tem- porary anchorage devices, and to make the procedure less uncomfortable for the patient (Keles and Sayinsu, 2000; Smith and Gray, 2000; Tsoun et al., 2002; Kyung et al., 2003; Park and Kwon, 2004; Cope, 2005; Costa et al., 2005). At present, there are numerous clinical reports that describe the use and advantages of different types of screws used to correct complex malocclusions. Unfortunately, there are very few controlled studies that provide us with a good scientific foundation for the use of fixation screws (Keles et al., 2003; Gelgor et al., 2004; Carano et al., 2005; Kircelli et al., 2006; Escobar et al., in press) or for the use of implant-supported distal- izers such as the Graz implant-supported pendulum (Karcher et al., 2002), the bone screw anchorage for the pendulum (Chang et al., 2006), the Kir- celli bone-anchorage appliance (2006), the osteointegrated implants with pendulum springs (Oncag et al., 2007), and the skeletal anchorage system for distalizing molars (Sugawara et al., 2006; Escobar et al., in press). 392 Oberti et al. The aim of this cephalometric study was to evaluate the amount of maxillary molar distal movement (area of action) and the changes in the position of the maxillary premolars and anterior teeth (area of reaction) caused by the use of the pendulum appliance anchored with endosseous non-osteointegrated fixation screws in the palate. This technique has the advantage of being less invasive than techniques that require surgery for placement of anchorage devices. MATERIALS AND METHODS This was a clinical descriptive study with a sample of 20 consecu- tively treated patients (11 males and 9 females) whose average age was 13 + 2 years. At the beginning of treatment, the patients presented with a CS3 stage of cervical vertebral maturation, which corresponds to peak skeletal maturation (Baccetti et al., 2005). The criteria for inclusion in the study Were: • Class II malocclusion requiring non-extraction protocols includ- ing distalization of upper molars; • an absence of any other appliance in the upper arch during the distalization procedure; • a horizontal or neutral growth pattern; • an absence of dental anomalies or systemic diseases. Upon obtaining parental permission, patients were invited to participate in the study and then were asked to sign an informed consent form that described all of the procedures. This study was reviewed and ap- proved by the ethical committee of the Institute of Health Sciences CES, Medellin, Colombia. - The Hilgers pendulum design (Hilgers, 1992) was used with a double loop modification and no dental premolar support (Escobar et al., in press). A metallic bearing 1.9 mm in diameter was included in the an- terior part of the acrylic for radiographic reference. The bone-supported pendulum (BSP) was attached to the palate by two non-specific titanium SCTCWS. Surgical Procedure The BSP was placed in the anterior part of the palate in each pa- tient by the same operator using two endosseous fixation screws 2.0 mm in diameter and 11 mm long (MONDEAL North American, San Diego, California). The screws were placed using a modification of the tech- nique developed by Tsoun and colleagues (2002) for insertion of fixation 393 Bone-Supported Pendulum implants. The palatal region was anesthetized with Lidocaine at 2% with Epinephrine (1:80,000). Once the patient was anesthetized, the pendulum appliance was positioned against the palate, the location of the screws was marked on the acrylic, and perforations matching the markings were made in the acrylic. The diameter of the perforations made in the acrylic was a little larger than the diameter of the screws in order to ensure that there would be no resistance from the acrylic at the moment of insertion. Imme- diately thereafter, the pendulum appliance was placed against the palate, the soft tissue and the cortical plate were perforated with a drill maintain- ing abundant external irrigation with sterile saline solution, and the screws were inserted manually. Figure 1. Pretreatment extraoral and intraoral views. 394 Oberti et al. Once the BSP was positioned, the TMA springs were placed in the lingual sheaths of the first molars with an approximate force of 250g (as verified by a Dontrix dynamometer). Nonsteroidal analgesics were prescribed for the first day post BSP placement. Patients were taught to maintain good oral hygiene and asked to use a mouthwash regularly dur- ing orthodontic therapy. At every appointment, the soft tissue around the BSP was checked, and the springs were reactivated when necessary. Lateral cephalograms were taken immediately after placement of the BSP and at the end of the distalization movement. Distalization was continued until the Class II molar relationship was overcorrected clini- cally to a super Class I molar relationship. The BSP then was left in place as a retention appliance during the retraction of the premolars, which took approximately three months (Figs. 1-3). Figure 1. Continued. 395 Bone-Supported Pendulum Figure 3. Post-treatment extraoral and intraoral views. Radiographic Analysis The analysis of the lateral cephalograms included vertical, Sagit- tal and angular measurements of the position/inclination of the upper first molars, second premolars and incisors. The mandibular plane also was 396 Oberti et al. Figure 3. Continued. Figure 4. Cephalometric landmarks. evaluated, as were the positional changes of the appliance, which was ac- Complished by measuring the movement of the acrylic bearings (Fig. 4). 397 Bone-Supported Pendulum The inter-observer and intra-observer calibration was performed using the Interclass Correlation Coefficients to evaluate the amount of agreement among the researchers. Values above 0.984 indicated a high level of concordance. Statistical Analysis A descriptive statistical analysis of the results was carried out us- ing measurements of central tendency (the average and the median), mea- surements of dispersion (standard deviation), and the variation coefficient. A non-parametric test (Wilcoxon) was used for paired data in order to compare the degrees of inclination, mesial and distal displacement, and vertical changes of the upper molars, premolars and incisors before and af- ter the movement. Spearman’s correlation coefficient was used to establish the relationship, or lack thereof, between the inclination and the displace- ment of the upper molar at the completion of the distalization movement. RESULTS Average cephalometric values pre-distalization (T1) and post-dis- talization (T2) are seen in Table 1. The BSP was used for the distaliza- tion for an average of 7.3 months. Two patients were excluded because of tissue inflammation and screw failure. The BSP was removed manually without the need of anesthesia. Mild-to-moderate soft tissue irritation was detected on the palatal mucosa, but this condition was resolved in a few days by having the patient follow a good hygiene protocol. The average distalization for the upper molar was of 5.7 ± 2.2 mm (U6mp-Yaxis), which was statistically significant (p = 0.0002). The average inclination was 10.0 + 7.5° (U6-FH), which also was statistically significant (p < 0.01). The average distalization for the upper second premolar was 5.1 + 2.2 mm (U5-Yaxis, p = 0.0002) and the average for the distal inclination was 9.8 + 5.4° (U5-FH, p = 0.0006). The upper central incisor was retruded on average 0.6 + 1.2 mm (U1-Yaxis, p = 0.05), and had an average lingualization of 2.3 + 2.6° (U1- FH, p = 0.0003). The changes in the vertical measure of the molars, premolars and the incisors were not statistically significant. The mandibular plane rotated backward 1.39 + 1.2° (MP-FH) on average. This change was statistically significant with a value of p = 0.0032. 398 Oberti et al. Table 1. Dentoalveolar and skeletal effects of the BSP. T1 (Predistilization) | T2 (Postdistalization) | Differences P Mean SD CV | Mean SD CV Mean SD | Value "****| 37.8 49 13.0 | 32.1 52 163 || 57 22 || 0.0002 (mm) *** | 48.1 47 9.7 | 430 4.8 112 || 5.1 22 0.0002 (mm) "*** | 73.4 5.5 74 | 72.8 s. 7.1 | 0.6 12 || 0.0545 (mm) *" | 470 43 9.1 || 47.7 3.5 74 | .06 17 | 0.0112 (mm) p * | 45.2 3.8 84 || 454 33 73 || 02 2.1 || 0.1204 (mm) "*" | 48.6 42 8.6 || 48.9 3.8 7.9 | 103 1.4 0.6027 (mm) "*" | 329 44 84 54.1 3.5 6.5 ! -13 1.5 | 0.3590 (mm) tºm 75.0 3.0 4.0 || 65.0 7.5 11.5 || 10.0 7.6 || 0.0052 º 83.5 3.6 4.3 || 73.8 3.4 4.6 || 9.8 5.4 || 0.0006 º 109.3 9.2 8.4 || 106.9 8.6 8.0 || 2.3 2.6 || 0.0003 wºm 25.5 4.4 17.2 || 26.9 4.5 16.8 || -1.4 1.2 0.0032 The bearing, which was located in the anterior part of the BSP ap- pliance, was moved anteriorly 0.62 + 0.5 mm and vertically 0.42 + 0.34 mm, showing a slight change in position of the acrylic button. DISCUSSION The main reason for using a molar distalization system such as the BSP is to avoid incurring the adverse effects usually associated with this type of orthodontic treatment with pendulum appliances, i.e. the loss of anchorage generally expressed as mesial movement of the premolars and the labialization of the maxillary incisors (Ghosh and Nanda, 1996; Byloff and Darendeliler, 1997; Bussick and McNamara, 2000; Chaqués- Asensi and Kalra, 2001; Kinzinger et al., 2004, 2005; Chiu et al., 2005; Oncag et al., 2007). There now are several endosseous appliances that have been developed to provide total anchorage control during distaliza- tion. While the majority of the articles in the literature are reporting the results of clinical experiences and not the results of controlled studies 399 Bone-Supported Pendulum (Giuliano et al., 2002; Bantleon et al., 2002; Giancotti et al., 2000; Karch- er et al., 2002; Karaman et al., 2002; Gelgor et al., 2004; Keles et al., 2003; Carano et al., 2005; Kircelli et al., 2006), the systems described have proven to be efficient in controlling anchorage. However, these im- plant systems usually require invasive surgical procedures to place and remove the anchorage device and, in some cases, the devices cannot be loaded immediately (Roberts et al., 1984; Giuliano et al., 2002; Bantleon et al., 2002; Giancotti et al., 2000; Karcher et al., 2002; Karaman et al., 2002; Gelgor et al., 2004; Keles et al., 2003; Carano et al., 2005). The design of the endosseous anchorage system with the BSP discussed in this study provides anchorage against the forces reciprocal to the distalization movement and thus offers advantages not available with other anchorage systems such as the need for only minor invasive surgical procedures to place and remove the anchorage screws and the ability to immediately load the implant device. The results of treatment with the BSP were similar to those re- ported in studies on the tooth supported pendulum with regard to the distal movement of the upper molars (with a distalization rate of 0.7 mm per month), the molar inclination, and the changes in the mandibular plane (Ghosh and Nanda, 1996; Byloff and Darendeliler, 1997; Bussick and Mc- Namara, 2000; Chaqués-Asensi and Kalra, 2001; Kinzinger et al., 2004, 2005; Chiu et al., 2005; Oncag et al., 2007; Escobar et al., in press). How- ever, the BSP-induced changes in the position of the premolars and inci- sors were very different from those described in other studies (Kircelli et al., 2006; Oncag et al., 2007). These studies reported that using the BSP eliminated the reciprocal forces over the maxillary premolars anterior teeth, achieving the simultaneous effect of distalization of the premolars and molars and resolution of the anterior crowding, with some retraction and lingualization of the incisors. This translates ultimately into a decrease in total treatment time for comprehensive fixed appliance therapy. Another advantage of the bone supported system is that once the molar is distal- ized, the appliance can be used as a retention appliance during the initial phases of fixed appliance therapy, which eliminates the need for a Nance holding arch as anchorage for the molars, as proposed by Hilgers (1992). The mandibular plane rotated 1.4° in a posterior direction, which is similar to the value found in several pendulum studies (Ghosh and Nanda, 1996; Byloff and Darendeliler, 1997; Bussick and McNamara, 2000; Chaqués-Asensi and Kalra, 2001; Kinzinger et al., 2004, 2005; Chiu et al., 2005). Some researchers believe that the vertical changes in 400 Oberti et al. the mandible are produced by the wedge effect created by moving the mo- lar to a more posterior point (Ghosh and Nanda, 1996). Additionally, the inclination and rotation of the molar creates premature contact that creates a tendency to an anterior open bite. When the stability of the BSP appliance was evaluated, a small amount of movement in an upper-forward direction was found. This can be explained by the generation of movement produced as a reaction to the force of the springs located in the molars, which produces a fulcrum ef- fect on the screws, which causes the acrylic to slightly imbed against the palate. This is a consequence of the lack of osteointegration of the screws, the stability of which is based on a mechanical retention that is affected by the quality and thickness of the osseous cortical and the screw diameter (Kyung et al., 2003). CONCLUSIONS Treatment with the bone-supported pendulum (BSP) appliance proved to be a good method for distalization of the upper first molars in a Class II malocclusion. The present clinical study describes effects that are expected normally with this type of appliance such as the inclination of the molar and the posterior rotation of the mandibular plane. The use of endosseous screws proved to be an efficient anchorage method, thus allowing a decrease in treatment time due to the self correction of the anterior crowding and the spontaneous distal migration of the premolars. The use of the BSP appliance facilitated alignment, leveling and retraction processes in the final treatment phase with fixed appliances. 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Development of orthodontic micro-implants for intraoral anchorage, J Clin Orthod 2003:37:321–328. Mavropoulos A, Karamouzos A, Kiliaridis S, Papadopoulos A. Efficien- cy of noncompliance simultaneous first and second upper distaliza- tion: A three-dimensional tooth movement analysis. Angle Orthod 2005;75:532–539. Melsen B, Dalstra M. Distal molar movement with Kloehn headgear: Is it stable? Am J Orthod Dentofacial Orthop 2003;123:374-378. Ngantung V, Nanda RS, Bowman SJ. Post-treatment evaluation of the distal jet appliance. Am J Orthod Dentofacial Orthop 2001; 120:178- 185. Nishii Y, Hidenori K, Hideharu Y. Three-dimensional evaluation of the distal jet appliance. World J Orthod 2002;3:321-327. Oncag G, Seckin O, Dincer B, Arikan F. Osseointegrated implants with pendulum springs for maxillary molar distalization: A cephalometric study. Am J Orthod Dentofacial Orthop 2007;131:16-26. Park HS, Kwon TG. Sliding mechanics with microscrew implant anchor- age. Angle Orthod 2004;74:703–710. Roberts WE, Smith RK, Zilberman Y, Mozsary PG, Smith RS. Osseous adaptation to continuous loading of rigid endosseous implants. Am J Orthod Dentofacial Orthop 1984;86:95-111. Smith R, Gray J. Transitional implants for orthodontic anchorage. J Clin Orthod 2000:24:659-666. 404 Oberti et al. Sugawara J, Kanzaki R, Takahashi I, Nagasaka H, Nanda R. Distal move- ment of maxillary molars in nongrowing patients with the skeletal an- chorage system. Am J Orthod Dentofacial Orthop 2006;129:723-733. Tsoun T, Keles A, Everdi N. Method for the placement of palatal implants. World J Orthod 2002; 17:95–99. 405 THE BAYLOR EXPERIENCE WITH USING MINI-IMPLANTS FOR ORTHODONTIC ANCHORAGE: CLINICAL AND EXPERIMENTAL EVIDENCE P. Emile ROSSouw Peter H. Buschang Roberto Carrillo The purpose of this chapter is to provide both an insight into the litera- ture that stimulated mini-implant research and an overview of the experi- ence gained during previous and ongoing clinical and laboratory studies conducted on the use of mini-implants as orthodontic anchorage in the Department of Orthodontics at Baylor College of Dentistry, Texas A&M University System Health Science Center, Dallas, Texas. ANCHORAGE CONTROL IN ORTHODONTICS Anchorage control during orthodontic treatment undoubtedly is one of the most critical factors in determining the successful outcome of treatment. Historically, tooth movement has been limited by action/reac- tion forces because the primary means of anchorage were tooth borne. Moreover, Newton’s third law of motion dictates that there will be an equal and opposite reaction to every force applied during orthodontic tooth movement, making it difficult to eliminate unwanted tooth move- ment during treatment. Angle (1907) observed this limitation and noted appropriately that this lack of anchorage in an appliance can be consid- ered an “orthodontist’s nightmare.” Extraoral, intra-arch and inter-arch mechanics were developed to reinforce anchorage and facilitate a more favorable treatment outcome. Anchorage, or the resistance to unwanted tooth movement (Daskalogiannakis, 2000), is a biomechanical parameter that must be considered during the planning of all orthodontic treatment whether the need is to move the anterior teeth posteriorly or the posterior teeth anteriorly. Tweed (1936a,b) was exemplary in the use of the edgewise ap- pliance. He developed principles and a technique to follow in order to improve treatment outcome. Tweed’s philosophy for success included a Sound diagnosis, study of the problem, appropriate treatment goals and 407 The Baylor Experience preparation of proper anchorage. Discussion of anchorage was the theme at the various meetings and conferences at the time (Brodie, 1931); Vari- ous concepts of anchorage surfaced. Examples included the use of second permanent molars as a source of anchorage (Chuck, 1937), occipital an- chorage from a head cap and intermaxillary dental anchorage from Class II and III elastics (Thompson, 1940; Baker et al., 1972). The classic tip back bends for anchorage preparation described and used by Tweed were deemed stable (Tweed, 1936a,b). Tweed insisted that this intraoral anchor- age set up should be enhanced by occipital anchorage to be successful (Tweed, 1966). Anchorage problems often are described in contemporary ortho- dontics (Geron et al., 2003); however, as noted, it is not a new concept. Wright (1939) puts it very eloquently: Successful orthodontic management is dependent upon a defi- nite plan formulated from careful case analysis. Some failures are due to incorrect analysis. Others may be traced to inability to carry out a plan, but often they are the result of lost or insuf- ficient anchorage. Thus anchorage is one of the major problems in orthodontics and is worthy of careful study. In addition, Wright noted that anchorage was not available intraorally. Strang (1941) added that anchorage in the oral cavity must be described simply as “resistance to movement” and that stationary anchorage was a myth; extraoral occipital anchorage provided the advantage. An investiga- tion on the use of occipital anchorage in orthodontic treatment showed that the effectiveness of any orthodontic appliance depended on its anchorage control (Kresnoff, 1942). Moreover, the control of the anterior vertical di- mension depended on the proper selection of extraoral anchorage (Kuhn, 1968). The planning and selection of an appropriate anchorage regimen, as well as the anchorage device itself, are important. In addition, care- ful evaluation of force application must be considered, as anchorage con- servation is essential when closing space such as that which occurs fol- lowing extractions to correct a malocclusion. The classic study of Storey and Smith (1952) comes to mind. They described differential anchorage as an exchange between light and heavy forces, the choice of which de- pended on the tooth movement required; heavy force (400 to 600 gm) moved molar anchorage while the canine remained stationary and light force (150 to 200 gm), which was used during space closure, retracted the canine while the molar remained stationary. In reference to the previously 408 Rossouw et al. cited papers and data from present day knowledge of the biology of tooth movement, one realizes that even maximum anchorage, when using dental units as anchorage, results in the loss of at least one-third of the extraction space. To avoid these dental side effects, De Pauw and colleagues (1999) recommended the use of ankylosed teeth or intraoral implants as anchor- age. The importance of anchorage cannot be underestimated. Websters International Dictionary defines anchorage as “a secure hold sufficient to resist a heavy pull.” This implies a source of attachment that is absolutely stable and rigid. Therefore, we are confronted with the fact that there is no true intraoral anchor base available for orthodontic use, as also noted previously by Wright (1939). A systematic review of anchorage (Feld- mann and Bondemark, 2006) shows that three main anchorage situations existed: (1) anchorage of molars during space closure after premolar ex- tractions, (2) anchorage loss in the incisor or premolar region (or both) during distal movement of molars, and (3) skeletal anchorage supplied by implants, miniscrews, or similar techniques. However, only case reports and small case studies, albeit with promising results, were found regarding skeletal anchorage. The scientific evidence was too weak to evaluate the efficiency of the different anchorage systems used during space closure because a vast heterogeneity of the studies existed. Gainsforth and Higley (1945) were the first to report on the possi- bility of orthodontic anchorage in basal bone via an implant. Even though their results were largely unsuccessful, the notion of implant-derived an- chorage was established. The introduction of the concept of osseointegra- tion by Bränemark in 1965 (Brănemark, 1983) provided the means by which implant-assisted anchorage could impart infinite anchorage. The advent of the endosseous dental implant provided the first clinical appli- cation of an infinite anchorage system (absolute anchorage) that could achieve the latter goals. The extensive work of Bränemark (1983) and others (Welsh et al., 1971; Albrektsson et al., 1983; Linder et al., 1983) on Osseointegration or bone-implant contact demonstrated the mechanism by which a metal fixture could be integrated into bone without causing the body to reject it and be ready for use after a healing period of approxi- mately six months. The evolution and acceptance of Osseointegrated implants as a restorative alternative was commonplace by the early 1980s (Ohashia et al., 2006). Orthodontic applications of the endosseous implant have been evaluated and demonstrated to be effective for use under orthodon- tic type loads in several laboratory and clinical studies (Creekmore and 409 The Baylor Experience Eklund, 1983; Gray et al., 1983; Roberts et al., 1984, 1989, 1990; Odman et al., 1988; Smalley et al., 1988; Turley et al., 1988; Higuchi and Slack, 1991). As the profession became more comfortable using implant-assist- ed anchorage, it frequently became part of treatment planning. It soon was obvious that the conventional dental implant, even when miniaturized, re- quired more space than available in most instances. Examples of space restrictions included the limited space between roots and space in which only minimal vertical bone was available. This encouraged the devel- opment of numerous implant-derived anchorage adjuncts to orthodontic treatment such as the palatal implant, retromolar implant, onplant, zygoma ligature wires, skeletal anchorage systems, and because space often is lim- ited, the mini-implant (MI) or temporary anchorage device (TAD). Numerous case reports have discussed the biomechanical advan- tages of using a TAD as mini-implant anchorage (MIA; Costa et al., 1998; Lee et al., 2001; Nojima et al., 2001; Park et al., 2001, 2002; Bae et al., 2002; Chung et al., 2002; Paik et al., 2002; Kyung et al., 2003). Before the use of these mechanics becomes widespread, however, the potentials and limitations of MIs should be established by well-controlled clinical and laboratory studies. Anchorage resources, such as a headgear or face mask, require patient cooperation, which, if not forthcoming, may result in unpredict- able treatment outcomes. Therefore, orthodontists have been pursuing a strong and reliable device for anchorage control for many years. Ideally, the pursuit of intra-oral anchorage points that are immobile, biocompati- ble, easy to use and independent of patient compliance is the orthodontist’s goal. The quest for infinite anchorage (zero anchorage loss) began with an attempt to identify a method for anchorage independent of the dentition (Daskalogiannakis, 2000). ANCHORAGE AND ITS SIGNIFICANCE Undesirable tooth movement can occur when anchorage is not controlled. The most evident scenarios can be illustrated in a Class I bi- alveolar protrusive or Class II, division 1 malocclusion requiring extrac- tion therapy. In these situations, it often is desirable to maintain the pos- terior teeth in their pretreatment location (unmoved). The objective is to move the anterior teeth posteriorly into the extraction space in order to obtain the greatest amount of total profile or overjet reduction. Because the posterior teeth have a larger total root surface area than the anterior 410 Rossouw et al. teeth, they do not move forward to the extent that the anterior teeth move posteriorly during reciprocal closure. However, they do move forward to Some degree (Tweed, 1966), causing a loss of anchorage and a reduced to- tal amount of anterior retraction accomplished. In order to improve the fi- nal result, some type of anchorage aid typically must be used because once anchorage has been lost, it is very difficult to regain. The majority of an- chorage-enhancing mechanics requires patient compliance without which the mechanics will fail miserably or some sort of fixed and non-compliant correction device will be needed. This scenario is well illustrated in Figure 1 where the Class II relationship still exists following space closure due to the lack of patient cooperation. t Figure 1. This figure illustrates the results of patient noncompliance. Note the poor hygiene and the non-wearing of headgear and Class II elastics. Although the alignment of teeth is acceptable, the Class II, division 1 problem still is pres- ent after 31 months of treatment. The advent of implant-assisted anchorage has provided two fun- damental benefits. First, it eliminated the need for patient anchorage compliance. Second and more importantly, infinite anchorage allows 4|| The Baylor Experience teeth to be moved maximally in the desired direction without any adverse movement of other teeth. As mentioned previously, compliance is a necessity for many tra- ditional means of anchorage enhancing mechanics, such as headgear ap- plications. Unfortunately, it is impossible to predict the future compliance of the patient because it is a multifactorial phenomenon. Sinha and Nanda (2000) found that patient compliance was related to the duration of treat- ment and to the frequency and complexity of the task. Patient compliance also has been shown to be attributable directly to the pain experienced during treatment (Sergl et al., 1998). Egolf and colleagues (1990) found a negative correlation with pain (inconvenience and dysfunction) and posi- tive correlations with general health awareness (specific dental knowledge and personal oral embarrassment). Extraoral anchorage may be rejected prior to initiation of treatment by the patient for aesthetic concerns; ex- tended duration of treatment also may be an impediment to continuous cooperation (Wehrbein et al., 1996). Biomechanics would be simplified tremendously if intra-oral anchorage points were available that were im- mobile, biocompatible, easy to use and independent of patient compliance. The emphasis of contemporary orthodontics thus should be on prevention and management of anchorage applications that are not dependent on pa- tient compliance. As the profession realized the potential benefits of infinite anchor- age, there was a desire to use its advantages in more conventional cases in which no teeth were missing. ALTERNATIVE IMPLANT ANCHORAGE The obvious predicament in cases with no missing teeth is the lack of space required for the conventional dental implant (Block, 1996). This situation led to the development of the palatal (mid-sagittal) and retromo- lar endosseous implants. Unfortunately, in most cases these are not cost effective or practical (Costa et al., 1998; Melsen and Costa, 2000) as two complex surgical procedures are required for placement and removal. Ad- ditionally, laboratory and chair time are needed to deliver the attachment mechanisms, increasing the cost even more. Despite their limitations, the use of palatal implants is well established and there are suitable cases for such use. The aforementioned limitations of the palatal (mid-sagittal) im- plant led to the development of the Onplant. Onplants were purported to provide the benefits of the palatal implant with less extensive surgical procedures required. The thin disk design allowed the reduction of sur- 412 Rossouw et al. gical morbidity, but because there is no mechanical retention of the im- plant, it was solely dependent on integration with the underlying alveo- lar bone (Block and Hoffman, 1995). Sugawara (1999) used the skeletal anchorage system (SAS) to correct a severe anterior cross bite where no mandibular molars were present to serve as anchorage. Essentially, the SAS is a modification of a rigid miniplate and bone screw fixation, with a portion of the miniplate exposed to the oral cavity for attachment to the conventional orthodontic appliance. It primarily is used in the ramal and infrazygomatic regions, with its only limitation when placed in the region of the dentition being that it must be placed apical to the roots of the teeth (Umemori et al., 1999). Glatzmaier and co-workers (1996) reported on the biodegradable polyacitide orthodontic system (BIOS), which was developed to provide a stable, but temporary, implant for tooth movement. It had a biodegrad- able body into which a traditional metal abutment could be inserted. After the implant had served its purpose as anchorage, the abutment could be removed leaving the implant body to degrade naturally. Although the need for a second surgery was eliminated, the time period prior to degradation (9 to 12 months) limits its usefulness. Other limitations include its size, which limits the potential sites for use, and the loads it could withstand, which were considerably less than those possible with traditional implants (Glatzmaier et al., 1996). Zygoma ligature wires also have been suggested for infinite an- chorage (Costa et al., 1998). Their primary limitation is that they are site specific and may be maintained only for three to six months, which limits their usefulness. However, they may be loaded immediately. Freudentha- ler and colleagues (2001), in contrast, suggested the use of bone screws that provide bicortical anchorage. IDEAL CHARACTERISTICS FOR AN IMPLANT ANCHORAGE SYSTEM An optimal implant-derived orthodontic anchorage system: • is stable during use; • has small dimensions; • has minimal surgical morbidity; • is easy to place and remove; • allows simple and reliable attachment to the orthodon- tic appliance; • may be loaded immediately; 413 The Baylor Experience • is economical; • is not site-specific, but allows for a broad area of appli- cation; and • is able to withstand loads greater than clinically re- quired. Kanomi (1997) recognized the limitations of the endosseous implant. He introduced the first MSI used for orthodontic anchorage and stated that “a mini-implant for orthodontic anchorage should be small enough to place in any area of the alveolar bone, even in apical bone. The surgical pro- cedure should be easy enough for an orthodontist or general dentist to perform and minor enough for rapid healing. The implant should be easily removable after orthodontic traction.” NOMENCLATURE There presently is no consensus on the terminology used for the new small implants devised specifically for orthodontic application. Nu- merous terms have been used in the literature to describe these implants including micro-implant, micro-screw implant, miniature implant, mini- dental implant, miniscrew, bone screw, mini bone plate, and mini plate. Conventional dental implants are 3.5 to 5.5 mm in diameter and 11 to 21 mm long (Kanomi, 1997). These new temporary anchorage devices (TADs) are less than 3 mm in diameter and 11 mm long. Micro by defini- tion is one millionth (1 x 10°) of a specified unit making its use inappropri- ate for the purpose of description here. Although the definition of a screw (a cylindrical rod with incised threads having a slotted head so that it may be turned by a screwdriver) accurately describes the physical properties of these small implants, it does not convey the same meaning as the term implant does, because an implant is a device surgically embedded in living tissue. Mini by definition is something distinctively smaller than others in its class and because we are talking about implants, its use is more appro- priate than micro. Therefore the term mini-implant or miniscrew implant (MI) is appropriate for describing implants smaller than 3 mm in diameter and 11 mm long. DESIGN Various companies market mini-implants (AbsoAnchor(R), Den- taurum, HDC Co., IMTEC Corp., KLS Martin, Ormco, RMO, GAC, Stryker Leibinger and many more). The obvious common feature is the 414 Rossouw et al. size of the MI (smaller than 3 mm in diameter and 11 mm long). How- ever, there are subtle differences in the thread design, profile, composi- tion and head design that may affect the manner in which an MI is used. For example, the Spider Screw (HDC Co., Sarcedo, Italy) has an internal and external rectangular slot along with an internal round slot and may be placed with a sterile conventional screwdriver. The Ortho-Implant (IMTEC Corp., Ardmore, Oklahoma, USA) has a rounded head with a hexagonal base that requires a specialized driver for placement. Both the head and neck of the Ortho-Implant have a small aperture through which a ligature may be passed for attachment. The rounded head also permits the attachment of various accessories such as a soft tissue healing cap and transfer coping. The Baylor laboratory and clinical studies were executed using IMTEC miniscrew implants. SURGICAL PROCEDURE Essentially there are three procedures by which an MI may be placed: two-stage, single-stage and direct. All three methods may be ac- complished under local anesthesia by regional infiltration. Nerve blocks are not only unnecessary, but undesired. If a vital structure is hit dur- ing placement, the patient may be able to sense this complication, which would allow for an alternate placement and avoid any permanent negative Sequelae. In the two-stage surgical procedure, a surgical flap is reflected exposing the underlying periosteal bone. A slow-speed drill with an ap- propriate diameter bit (the bit diameter typically is smaller than the di- ameter of the MI) and copious irrigation used to drill a pilot hole. The irrigation and slow speed prevent the bone from overheating. The implant is inserted with the corresponding driver until it reaches its appropriate position and the flap is closed over the MI for a healing period. After the healing period, the MI is surgically re-exposed and is ready for orthodon- tic attachment. In a single-stage procedure, a slow speed drill with an appropri- ate diameter bit and copious irrigation is used to drill a pilot hole directly through the overlying soft tissue. In the Baylor studies, a 1.1 mm prepared pilot hole was used to accept the 1.8 mm diameter IMTEC miniscrew im- plant inserted with the corresponding driver until it reached its appropriate position. The MI then may be allowed a healing period or may be loaded immediately. 415 The Baylor Experience In the direct procedure, the MI is inserted directly into the bone by means of the driver without creating a pilot hole. Although this protocol is difficult technically, it offers two advantages. First, there is no heat generated that might increase the opportunity for integration. Second, and more importantly, it allows the clinician tactile sensation of the surgical site that could help minimize aberrant placement of the microimplant or root damage. Some of the Baylor studies used this type of IMTEC mini- screw implant with the same dimensions except with a sharp, pointed in- sertion end. Presently, research is being conducted at Baylor College of Den- tistry to discern differences among these implant techniques. However, clinicians always should evaluate their personal preference along with the manufacturer’s recommendations. LOCATIONS FOR USE As discussed previously, the primary limitation of traditional en- dosseous implants is site specificity due to their size. The reduced size of the MI allows for great versatility with respect to potential insertion sites. Obviously an MI may be placed in any potential site for an endosseous implant. Additional areas of possible use include the anterior nasal spine, infrazygomatic ridge, any portion of the maxillary or mandibular buccal cortical plate, the maxillary lingual cortical plate, the mandibular symphy- sis, and the retromolar region (Costa et al., 1998). Mommaerts (1998) quantified the average space available for an implant in the retromolar region. From a sample of CT scans taken of 20 patients (with a mean age of 27.4 years), he reported that: • the inner-outer cortex thickness anterior to the lingula was 7.2 mm; • the inner-outer cortex thickness at the level of the as- cending ramus was 10.8 mm; • the distance from the anterior surface of the ascend- ing ramus to the level of the oblique line was 15.2 mm; and • the thickness of the anterior cortex distal to the second molar was 2.9 mm. Thus, if a retromolar implant is too large for the site, there is more than adequate space available for an MI. Some of the aforementioned areas for intended use may require a surgical stent for placement because the margin of error for avoiding damage to vital structures is small during implant placement. An exam- 416 Rossouw et al. ple of such a procedure is described by Kitai and co-workers (2002) who illustrate a method for stent fabrication from a stereolithographic model. CONTEMPORARY STUDIES Fortunately, the rapid evolution of implant technology has led to the development of the MI specifically for orthodontic use. The three pri- mary advantages of MIs relative to traditional implants are: 1) smaller size (Deguchi et al., 2003), 2) simpler surgical procedure for placement and removal (Deguchi et al., 2003), and 3) less expense (Chen et al., 2004). Because the rapid development and apparent prevalent acceptance of MI has emerged only recently, few controlled studies have been published. However, there are numerous case reports advocating the biomechanical advantages of using MIs (Costa et al., 1998; Melsen and Costa, 2000; Lee et al., 2001; Nojima et al., 2001; Park et al., 2001, 2002, 2004, 2005; Bae et al., 2002; Chung et al., 2002; Paik et al., 2002; Kyung et al., 2003). More controlled studies are needed to investigate the biological and clini- cal effects of using such a system. Until recently, the classical implant literature has advocated a heal- ing period of three to six months prior to loading to allow for successful integration of the traditional dental implant. This notion was challenged by clinical accounts of obtaining integration with endosseous implants de- spite immediate loading (Salama et al., 1995, 1996; Bijlani and Lozada, 1996; Schnitman et al., 1996; Piattelli et al., 1997). Controlled animal studies of immediate loading have produced conflicting results. For ex- ample, Sagara and colleagues (1993) found a decreased bone contact area with immediately-loaded implants. In contrast, Piattelli and colleagues (1998) found increased bone contact area with immediately-loaded im- plants. When applying these findings to MI use, several factors should be considered. Although the forces experienced by MIs are smaller, the surface area of an MI also is significantly smaller in comparison to tra- ditional implants. It also is interesting to note that several studies on immediate loading with traditional implants advocate using implants at least 10 mm long (Lefkove and Beals, 1990; Buser et al., 1991; Tarnow et al., 1997; Horiuchi et al., 2000). However, due to anatomical con- siderations, most MI lengths used are less than 10 mm. All the Baylor studies used the IMTEC 6 or 8 mm MI. Some case reports have advo- cated immediate loading of MIs (Bae et al., 2002; Takono-Yamamoto et al., 2002; Maino et al., 2003). In the Baylor studies, both laboratory and clinical, the MIs were loaded immediately, although in the clinical studies 417 The Baylor Experience there was a minor delay due to appointment scheduling where the MIS were loaded within 3 days of placement. Only the control MIs were not loaded or, if they were loaded, the loading followed specific guidelines required for controls. It is inappropriate to extrapolate the results of prior investigations to this new apparatus without adequate evidence-based re- search. Implant surface type has been demonstrated to have a profound effect on Osseointegration. All MI surfaces presently manufactured are smooth, machine surfaced. The Baylor studies used smooth or machine- surfaced titanium alloy MIs. Schnitman and colleagues (1996) have shown that although smooth, machine-surfaced endosseous dental implants could be loaded immediately, their long-term success rate was reduced. Because the surface area of MIs is significantly smaller compared to that of conven- tional osseointegrated implants, it would seem to follow that the smooth, machine surface would be more detrimental when used for MIs. The re- ported success rates of MIs with light, continuous forces indicate that MI surface type is not a significant factor presently. However, the surface type may become a significant variable for success in the future, as orthopedic forces are applied to MIs. Two published studies have investigated the effect of delayed loading on MIs. Ohmae and colleagues (2001) considered the efficacy of the MI for orthodontic intrusion in the beagle dog. The sample consisted of three adult male dogs in which six MIs were placed apically (three buccal MIs and three lingual MIs) around the mandibular third premo- lars. One experimental MI was placed interradicularly on the buccal and lingual side. Control MIs were placed mesially and distally for each buc- cal and lingual surface. After a six-week healing period, the experimen- tal MIs were loaded with a 150g NiTi coil running from the buccal over the occlusal surface of the tooth and attached to the lingual experimental MI. Periapical radiographs were taken biweekly and tooth movement was measured. At the end of the 18-week loading period, the average intrusion was found to be 4.5 mm. Moreover, at the conclusion of the experiment, none of the experimental or control MIs displayed clinical mobility. Six of the 36 MIs then were removed easily with a screwdriver, indicating complete osseointegration of the MI may not be a problem when the MI is used for a short period. Histomorphometric findings revealed calcification of the loaded peri-implant bone to be slightly greater than or equal to that of the controls suggesting that the applied force of loading may stimulate more bone formation than when there is no applied force such as in un- loaded controls. 418 Rossouw et al. More recently Deguchi and colleagues (2003) evaluated the effect of clinically relevant (200g to 300g) discontinuous forces (elastomeric chain) on integration using 96 MIs (5 mm long x 1 mm in diameter) after each of three-, six- and twelve-week healing periods and compared the re- sults against matched, unloaded healing controls. During the initial three- week healing period, only three MIs failed. More importantly, none of the remaining MIs failed after force application. The results also showed that the mandibular MIs had significantly higher bone-implant contact than maxillary MIs. This would seem logical due to the higher amount of corti- cal bone in the mandible and is similar to the results suggested by Melsen and Costa (2000). The results also illustrated that as healing progressed, the bone naturally matured from woven to lamellar. Thus, early in the healing period, the bone implant contact and the bone volume/total volume were high and subsequently decreased. Deguchi and colleagues (2003) concluded that because none of the MIs loaded at three weeks failed, the MIS could have been loaded earlier. Melsen and Costa (2000) have published the only controlled study of immediate loading of MIs. They evaluated forces of 25g and 50g im- mediately loaded on 16 (8 mm long x 2 mm in diameter) MIs. Two of the MIs failed within the first month. Osseointegration was identified around twelve of the remaining 14 MIs. Histologic analysis showed that the de- gree of Osseointegration was dependent on time, but independent of force level and bone type. Although this study was the first to investigate true immediate loading, the forces used were roughly one-half to one-twelfth the force used in most clinical situations. In addition, the standard devia- tions of the degree of Osseointegration were extremely large, probably due to the small sample size. As mentioned previously, the surface area of the implant is an important factor for both physical stability and integration. A larger sur- face not only will result in more force dissipation, but also will enhance the opportunity for biological interaction with the body. Miyawaki and co-workers (2003) retrospectively investigated the success achieved fol- lowing the insertion of 134 titanium MIs of varying sizes in 51 patients. They recorded the factors associated with success of the MIs in the poste- rior region. Their study was the first to demonstrate that clinical integra- tion (stability) is dependent on the diameter of the implant. They noted that MIs greater than 1 mm in diameter were more successful than those with a diameter of 1 mm or less. However, there was no statistically sig- nificant difference in success for diameters between 1.5 mm and 2.3 mm. They also found that a higher mandibular plane angle (thin cortical bone) 419 The Baylor Experience and inflammation of the peri-implant tissue were associated with a higher failure rate. Interestingly, they found no relationship between when the MI was loaded, the amount of force applied (less than 2 N), or the type of bone (maxillary or mandibular) and the success, or lack thereof, of the MI. Cheng and colleagues (2004) assessed the risk factors associated with MI failure in a prospective clinical study. They evaluated 140 MIs (2 mm in diameter and lengths varying from 5 to 15 mm) in 44 patients (38 men and 6 women). Of the 140 MIs, 92 were freestanding and 48 were used with mini-plates (MIP). The distribution of the MIs was 104 in the posterior maxilla, 34 in the posterior mandible, one in the anterior maxilla and one in the anterior mandible. They estimated the force applied to be between 100g and 200g, but there was no standardized method of applica- tion (i.e., power-chain, coil spring or elastic thread), amount of force, or time of application. Overall survival rate was found to be 89% with no significant difference between the freestanding MIs and the MIPs. Sur- vival was defined as a stable MI or MIP with no peri-implant inflammation that still was able to withstand applied clinical load. Failures were related to location (posterior maxilla) and tissue type (inadequate keratinized gin- giva). These two factors may be related in the posterior mandible, an area that generally has less keratinized tissue. Cheng and colleagues pointed out that failure in the posterior mandible also may be a result of the bone overheating from the surgical procedure as it is denser in this region. They also hypothesized that infection predisposes MIs to failure because there was MI failure in five of the seven (71%) peri-implant areas that had in- fections. No significant effect was noted in the length of the implant with respect to failure. Two-thirds of the failures occurred prior to or within one month of loading. The use of the mini-implant is illustrated by the following case study (Figs. 2-7), which is part of a prospective research study currently being conducted at Baylor College of Dentistry. At the start of treatment (T1), the patient presented with: a convex profile with incompetent lips; a Class II molar relationship with protrusive incisors; a skeletal Class II relationship; a high mandibular plane angle; and a retrognathic mandibular position. Treatment was initiated by extracting four first premolars. Prior to placement of the MIs, a topical anesthesia (TAC-20 Topical: C-Li- docaine 20%; Tetracaine 4%; Phenylephrine 2%) was applied. IMTEC 420 Rossouw et al. Figure 2. A 14-year-old female patient with a typical Class II, division 1 bimax- illary protrusion malocclusion requiring maximum anchorage. (IMTEC Corp., Ardmore, Oklahoma, USA) miniscrew implants were placed between the maxillary second premolars and first molars for maxi- mum anchorage (Figs. 3-7). Placement position was determined using ra- diographs and a periodontal probe to identify the long axes of the adjacent teeth. 421 The Baylor Experience Figure 3. Initiation of treatment with a .018” Speed (Strite Ind., Cam- bridge, Ontario, Canada) self-ligation fixed appliance and a 1.8 mm x 8 mm miniscrew implant placed between the maxillary second premolar and the first molar. Figure 4. After 23 months of treatment and immediately prior to appli- ance removal. Note the lip profile improvement and Class I occlusion. 422 Rossouw et al. Figure 5. Occlusion. Figure 6. Post-treatment soft tissue and Class I occlusal goals have been achieved. Removable retainers are in place. 423 The Baylor Experience Figure 7. Superimposition of T1 and T2 cephalometric trac- ings. Note that the maxillary molars remained in position (in- finite or absolute anchorage) and that there is good mandibular anterior response. Differential eruption of the mandibular first molars has corrected the Class II malocclusion to a Class I, a similar action to that of a functional appliance. Figure 8. A comparison of the intraoral views showing the similarity between the animal model research design (left) and the patient treatment design (right). 424 Rossouw et al. An in vivo Baylor laboratory study (Owens 2004, Rossouw et al., 2006) provided guidance as to force application, to,oth movement and an- chorage stability – all essential research evidence that could be applied to the similar prospective clinical study being conducted (Fig. 8). The experimental animal (Beagle dogs) design followed a ran- domized split-mouth model. Unloaded controls supplemented the loaded MIs. Initially, all third premolars in the dogs were extracted surgically to facilitate future tooth movement. Anchorage entailed the placement of 1.8 mm x 6 mm MIS to be used with immediate as well as with delayed load- ing. Retraction forces were 25g and 50g (Fig. 9). —- Md-25-I – Md-50–I – MX-25–I – MX-25–D | 5 É 4 __ 5, 3 # , __ § .2 T -º- E 1 0 i I T i 40 60 80 100 120 140 Time (Days) Figure 9. Mean movement of the second premolars over the duration of the project (131 days). All groups, irrespective of loading time or force level, showed significant tooth movement (P<0.05). Md = mandible; Mx = max- illa; I = immediate loading; D = delayed loading. The success rate proved to be excellent. Only 1 of 56 MIS com- pletely failed within 21 days of placement and all partial failures (only three of 56) were clinically stable at the conclusion of the experimental period of 131 days. Moreover, no significant differences in failure (p s 0.05) were noted for the timing of load (immediate versus delayed), amount of force applied (25g or 50g), or location of teeth or mini-implants (maxilla or mandible). Measurement of the gingival pocket depths showed that initial soft tissue health exhibited gingivitis, but that gingival health quickly returned to normal through vigorous hygiene control throughout the project. 425 The Baylor Experience The prospective clinical trial conducted co-laterally with the ani- mal projects included subjects requiring extractions and maximum anchor- age, and all subjects were treated following the same protocol (Figs. 2, 10 and 33). All patients received two maxillary miniscrew implants between the maxillary first molar and second premolar/bicuspids (IMTEC 1.8 mm x 8 mm or IMTEC 1.8 mm x 6 mm). The following clinical case study is presented here in pursuit of evidence supporting miniscrew implant use. The 13-year, 11-month-old female patient presented with a convex profile (Figs. 10 and 11), procum- bent and everted lower lip, incompetent lips, Class II, division 1 maloc- clusion with irregularity of the teeth as well as proclined incisors, and mandibular space shortage of 7.3 mm. Figure 10. Thirteen-year, eleven-month-old female patient who had a Class II, protrusive lower soft tissue profile at the start of treatment. All subjects enrolled in the prospective trial received a soft tis- Sue visual treatment objective (VTO; Holdaway, 1983, 1984) to deter- mine clinical goals and anchorage requirements (Fig. 12). The appropriate yearly growth allowed was incorporated into the VTO when growth was a factor during the treatment interval. The VTO is constructed and fol- lowing soft tissue adjustment according to end-of-treatment objectives, the incisor positions are ideally position adhering to clinical cephalomet- 426 DENTAL RELATIONSHIPS Norm Measurement Overjet (mm) 5.8 2.5 * Interincisal Angle (U1-L1) (*) 108.6 130.0 *** IMPA (L1-MP) (*) 101.9 95.0 * SKELETAL / DENTAL U-Incisor Protrusion (U1-APo) (mm) 13.4 3.5 **** L1 Protrusion (L1-APo) (mm) 7.4 1.0 * L1 to A-Po (*) 34.2 22.0 *** MAXILLO-MANDIBULAR RELATIONSHIPS Convexity (A-NPo) (mm) 5.4 0.7 ** ANB (*) 5.7 1.6 ° CRANIOFACIAL RELATION FMA (MP-FH) (*) 33.1 23.9 ** Facial Axis-Ricketts (NaBa-PtCn)(*) 88.5 90.0 Facial Angle (FH-NPo) (*) 84.8 88.6 * DEEP SKELETAL STRUCTURE Lower Face Height (ANS-Xi-Pm)(*) 47.4 45.0 ESTHETIC Lower Lip to E-Plane (mm) 4.1 -2.0 *** SUMMARY ANALYSIS Class || Molar Relationship Skeletal Class II (ANB; A-NPo) Retrusive Mandible (Pg-N) Excessive Overjet Facial Pattern: Mild Vertical Figure 11. Cephalometric tracing and variables for patient seen in Figure 10 at the start of treatment. | § The Baylor Experience The space and thus the anchorage situation are determined accord- ing to the goals of the soft tissue VTO (Fig. 12). • Space shortage is 4.8 mm plus the space required to level the curve of Spee, which is 2.5 mm; the space shortage thus is 7.3 111111. • Repositioning of the Ll requires 3.0 mm. This increases the arch shortage X2 or 6 mm. • Complete space shortage equals 4.8 + 2.5 + 6.0 or 13.3 mm. • Eliminating the crowding by extracting the lower first bicuspids provides 15.3 mm of space. • The resultant space determining anchorage requirements is 15.3 - 13.3 or 2.0 mm total arch circumference. e Repositioning the lower first molars equals 2.0+2 or 1 mm. The lower first molars are allowed to be mesialized by 1 mm; more importantly, the upper first molars must be maintained using maximum anchorage to achieve a Class I occlusion efficiently. The general treatment plan was set as: 1. extraction of all first premolars; 2. maximum anchorage of maxillary first molars; and 3. use of 8 mm IMTEC miniscrew implants (Fig. 13). A radiographic evaluation of the availability of bone for place- ment of miniscrew implants (Fig. 14; Schnelle et al., 2004) showed that adequate bone exists in the interradicular space mesial to the maxillary first molars, more than halfway apically of the root length. Moreover, this was designated as a “safe zone” following a volumetric tomographic study by Poggio and colleagues (2006; NewTom SystemT) that provided a guide for miniscrew positioning in the maxillary and mandibular arch. A safe site buccally also was indicated in the interradicular space between the first molar and second premolar, 5 to 8 mm from the alveolar crest. Important aspects of implant placement include the following (Lundskog, 1972; Eriksson and Albrektsson, 1983; Albrektsson and Er- iksson, 1985; Heidemann et al., 1998, 2001; Dalstra et al., 2004; Cope, 2005): 1. A small pilot hole is preferred. Drill-free and non-drill-free MIs are available (IMTEC manufactures both). Drill-free MIs have a sharp end that may easily damage the root surface. Exercise caution during placement. 428 Rossouw et al. 2. Over-drilled pilot holes lead to inadequate primary stability. Handpiece stability is essential. 3. Make sure that there is enough bone available around an MI to provide adequate bone-to-implant contact. Cortical thickness is important; medullary bone is less important. 4. Minimize surgical trauma. Screw in MIs with precision. Avoid heat build-up during pilot hole drilling (> 47°C, > 1 min). 0.75mm Figure 12. Visual treatment objectives for the patient shown in Figure 10 (red = T2; black = T1). Note the growth adjustment, the clinical soft tissue and dental goals, and the molar anchor- age goals. 429 The Baylor Experience Figure 13. The IMTEC miniscrew implants are provided in sterile packages ready for clinical use. Figure 14. Radiographic images showing the position of the mini-implants of the patient shown in Figure 10, as cited in the literature (Schnelle et al., 2004; Poggio et al., 2006). During the progression of treatment, it was noted that one MI was migrating vertically, although adequate anchorage was still available (Figs. 15–17). Refer to previously noted data from the animal study. This was a sign of delayed mobility. Miniscrew implant drifting or migration previously has been reported by Liou and colleagues (2004). 430 Rossouw et al. - - - - Figure 15. Intraoral photographs taken at the beginning of active treatment of the patient shown in Figure 10. The patient has a .018” SPEED self-ligation ap- pliance that provides low friction, which is perfect for Class Isliding mechanics – an ideal combination when using MI anchorage. º, - The pull-out strength of a mini-implant is important when evalu- ating its long-term integrity (Huja et al., 2005). In order to attain more evi- dence on the use of an inclined MI, another laboratory study was initiated. The effect of MI orientation was evaluated in an in vitro study, the purpose of which was to assess implant stability and resistance to failure at the bone-implant interface (Pickard, 2004). Tensile and shear tests were com- pleted using cadaver mandibles dedicated to and approved for research purposes (Fig. 18; Table I). 43 | The Baylor Experience º Figure 16. Four-month progress intraoral photographs for Figure 10 patient. The MI provides indirect anchorage as well as direct anchorage as the “head- gear” component of force (forces range between 100 to 150g). Delayed mobility or movement of the MI during treatment could be prevented by: 1. reducing the initial load to the implant and thus preventing overloading: 2. reducing trauma as a result of habits, mastication, and tooth- brushing; and 3. informing the patient adequately as to preventative mea- SUTCS. 432 Rossouw et al. Figure 17. A panoramic view of Figure 10 patient shows the difference in the positions of the MIs, indicating a migrating MI. Direction of Force Implant Orientation ſº º º º º º º º º º º & º 45° to maximum stiffness 45° to minimum stiffness _________ ----------- 45° towards shear force 45° opposing shear force º º º º º º º º º º º º º º Shear – Minimum bone stiffness 90° 65 45° towards shear force 45° opposing shear force Figure 18. A compilation of images showing pull out/tensile tests and shear tests With various MI orientations (Pickard, 2004). *Note the values in Table I. 433 The Baylor Experience Table I. Descriptive statistics of maximum force at failure. Test Type Implant Orientation Maximum Force at Failure Mean S.D. Min Max (N) (N) (N) (N) 90° * 341.85 81.0 257.0 493.2 Pull-Out 45°- Maximum Stiffness 107.9 32.1 71.5 160,1 45°- Minimum Stiffness 141.4 57.0 92.8 250.8 Shear Test 90° 123.8 26.5 85.3 179.3 (Direction of Maximum 45°- Opposing Force 102.3 25.4 74.7 163.0 Bone Stiffness) 45°- Same as Force * 253.34 74.1 152.5 355.6 Shear Test 90° 138.1 34.6 88.5 174.0 (Direction of Minimum 45°- Opposing Force 87.5 27.2 62.2 123.6 Bone Stiffness) 45°- Same as Force * 264,16 21.0 230.2 278.3 * Denotes maximum force at failure significantly higher than other tests with p < 0.001 Management of delayed mobility or movement of the MI should include: : assessing mobility; eliminating etiology; reinforcing rigidity by a re-screw action of the MI; immobilizing the MI to prevent further vertical or horizontal “wiggling;” replacing an MI only if the sequence of action fails, it is pain- ful when force applied and/or gingivitis/peri-implantitis per- S1StS. The maintenance of MI anchorage prevented problems normally encountered during treatment using anchorage devices dependent on pa- tient compliance such as headgear (Fig. 1). Thus: 1. 2. 3. There were no compliance issues. There was no loss of anchorage. All extraction spaces were closed and a Class I occlusion was attained. 434 Rossouw et al. 4. Torque was controlled, especially for upper and lower inci- SOTS. 5. There was no unwanted extrusion of teeth. 6. There was no open rotation of the mandibular plane. Figure 19. A Correx gauge (Haag-Streit, Switzerland) can be used to ensure appropriate loading of the MI. Note that the ap- proximate 100g of force, as shown, is adequate for retracting the anterior segment. 435 The Baylor Experience - Figure 20. Twelve-month progress intraoral photographs of Figure 10 patient. A Class I posterior occlusion has been established and anterior retraction is progressing well. Note the migrated left implant. However, it still is providing indirect anchorage through the immobilization ligature. Class I and Class II elastic traction are maintained to ensure attainment of a complete Class I oc- clusion. 436 Rossouw et al. Figure 21. Seventeen-month progress tient. The consolidation phase has begun with full thickness stainless steel coor- dinated arch wires. The MIs have been removed. 437 The Baylor Experience Figure 22. One month post-treatment intraoral photographs of Figure 10 patient. Treatment time was 21 months. She has a healthy, functional, aesthetic and stable Class I occlusion. Figure 23. Soft tissue goals achieved matched Class I objectives for Figure 10 patient: a balanced soft tissue profile, harmonious relationships of the nose, lips and chin positions, competent lips and an aesthetic smile. 438 Rossouw et al. Figure 24. Comparison of T1 (left) and T2 (right) for Figure 10 patient. Note the correction of the Class II malocclusion to a Class I occlusion and the soft tissue profile normalization. Removal of MIS (Figs. 27–28) is an uneventful procedure. No lo- cal anesthesia is necessary and removal can be accomplished by unscrew- ing the MI with Weingart or Howe pliers. However, the most efficient unscrewing of an MI is achieved by using the IMTEC driver or a similar device appropriate for the implanted MI. A histomorphometric evaluation of MIS used as orthodontic an- chorage during tooth movement in the Beagle dog (Woods, 2007) showed no differences between the mesial and distal bone to implant contact re- gardless of 1) amount of load (25 or 50 gm) or 2) timing (immediate or delayed) of load. The medullary bone contribution to miniscrew implant stability appeared more important than anticipated or than was deduced from previ- Ously published material (Fig. 29). 439 The Baylor Experience º Figure 25. Superimposition of T1 (black) and T2 (green) ceph- alometric tracings. Note the molar anchorage, the Class I oc- clusion, the maxillary incisor retraction, the mandibular incisor uprighting, maintenance of vertical the dimension, the forward chin position and the soft profile normalization. 440 ROSSouw et al. Figure 26. Superimposition of T1 (black) and T2 (green) cepha- lometric tracings of individual evaluation areas. Note the absolute anchorage as well as the previously listed attained objectives. 441 The Baylor Experience control Experimental 442 Rossouw et al. Figure 29. A histomorphometric evaluation provided the percentage bone-to- implant contact. Evaluation occurred at three levels. The red zones indicate bone-to-implant contact. Note that the medullary bone contribution is excellent (Woods, 2007). The stability of these endosseous TADs allows clinicians numer- Ous treatment options not efficiently and consistently available in the past. Prevention of the eruption of teeth (Figs. 7, 26, 37) or the intrusion of single teeth or segments of teeth now is possible without significant re- active effects on neighboring teeth due to the stable anchorage provided by the miniscrew implants. The concern, however, is whether resorp- tion of roots during such intrusive movements is of significance. The *H Figure 28. Scanning electromicrograph of the experimental and control MIs. Osseointegration, as defined by Bränemark (1983), is possible. However, there is no indication of bone particle adherence. 443 The Baylor Experience effect of force on intrusion and root resorption using miniscrew implants as anchorage in Beagle dogs following a split-mouth repeated measures design (Carrillo et al., 2007) showed that significant (p → 0.05) amounts of intrusion (1.2 to 3.3 mm) of multi-radicular teeth can be obtained. Moreover, the miniscrew implant anchorage exposed to constant forces between 50 to 200g for 98 days had no significantly different effect on the amount of intrusion obtained. Importantly, root resorption, as measured radiographically, was related to the amount of tooth movement. The following clinical observations are important to the success of miniscrew implant application: 1. It is important to create interradicular space if adequate space is not present in this zone. This is achieved easily by root angulation or by using an open-coil spring between the selected teeth (Fig. 30). The MI is inserted after adequate space has been attained (Fig. 31). L - Figure 30. Creating space between the maxillary first molar and the second bicuspid using an open-coil spring. 444 Rossouw et al. Figure 31. After adequate space has been obtained, an MI is placed and set for anchorage application. 2. Soft tissue overgrowth is a possible side effect of MI, espe- cially if the vertical alveolar level is inadequate. The MI needs to be placed at the mucogingival junction or in the mucous membrane (non-keratinized tissue). Options to treat include: 1) using the MI as presented provided no complications occur such as continued gingivitis or, in more Severe conditions, bone loss; 2) inserting the MI at a more occlusal level (pursue keratinized tissue where possible); or 3) removing the overgrown tissue by Such means as laser therapy (Fig. 32). 3. Caution needs to be exercised when inserting the MI. Appro- priate protocol for assessing safe zones for MI placement must be followed (Schnelle et al., 2004; Poggio et al., 2006). In spite of such safety precau- tions, an MI can penetrate the root canal (Fig. 33) and endodontic treat- ment may be the end result. Research projects investigating such events of damage and healing are presently being completed at Baylor College of Dentistry. To consolidate the treatment possibility in the clinical application of MIS in maximum anchorage treatment situations, a final clinical case is presented (Figs. 34–37). 445 The Baylor Experience Figure 32. Treating a tissue overgrowth complication. Tissue can be removed with a soft tissue laser or the MI can be replaced at a site with more keratinized tissue. - Figure 33. An MI shown in the root canal with subse- quent endodontic treatment. 446 Rossouw et al. - -º- - - L - Figure 34. A 13-year-old male patient—a vertical grower with a full profile with lip strain and a Class I malocclusion. He was treated using maximum anchor- age. Note the severe crowding, the extractions of premolar teeth and skeletal anchorage. Retraction was initiated at the first appointment. º * - 447 The Baylor Experience Figure 35. Intraoral photographs of patient seen in Figure 34 taken after 17 months of active orthodontic treatment. Note the Class I occlusion, the sec- tioned lower arch and the up and down elastics (finishing elastics). Miniscrew implants provide an alternate to treatment requiring maximum anchorage that may be dependent on headgear application and, more importantly, relies on patient compliance in order to attain a success- ful outcome. Given the choice, patients choose, without hesitation, the MI route (Fig. 38). A survey of the patients treated with MIs at Baylor Col- lege of Dentistry provided the following interesting information: • Patients were concerned about the use of MIS prior to the start of their treatment. 448 Rossouw et al. • Patients anticipated that there would be pain associated with ap- plication of the MI. • Patients were surprised when they experienced no pain or irrita- tion with the insertion and use of the MI. • There were no complaints with respect to MI placement and use during the period of treatment. • Patients adapted within days to the MI. • Patients indicated that they would recommend treatment that used MIS to others. • A significant number of patients accepted treatment with MIS versus treatment with headgear appliances. Figure 36. Initiation of the post-treatment retention phase after 18 months Of active treatment. 449 The Baylor Experience gº Figure 37. Superimposition of T1 (black) and T2 (green) cephalo- metric tracings. Note: Anchorage control. Profile harmony has been attained and a normal interincisal angle established. Figure 38. A comparison of extraoral headgear appliances and the unobtru- sive intraoral MI. It is obvious why adolescent patients would choose the MI. 450 Rossouw et al. CONCLUSIONS The evidence provided through the Baylor College of Dentistry research indicates that miniscrew implants provide successful anchorage and concluded that: 1. MIS meet our skeletal anchorage goals. 2. Successful and consistent clinical results are possible with MI UlSC. 3. It appears that the MI failure rate (approximately 8.9% in the Baylor studies) declines as use of and experience with MIS increases. 4. Caution should be taken with the application of MIs to avoid iatrogenic trauma. 5. Use good clinical evaluations to determine the appropriate use of MIS. 6. Avoid inserting an MI just because it is available or inserting too many MIs due to following inadequate protocols. 7. 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Immediate loading of threaded implants at stage 1 surgery in edentulous arches: Ten consecutive case reports with 1 to 5 year data. Int J Oral Maxillofac Implants 1997;12:319- 324. - Thompson WM. Occipital anchorage. Angle Orthod 1940; 10:206-211. Turley PK, Kean C, Schnur J, Stefenac J, Gray J, Hennes J, Poon LC. Orthodontic force application to titanium endosseous implants. Angle Orthod 1988:58:151–162. Tweed CH. The application of the principles of the edgewise arch in the treatment of Class II, division 1: Part I. Angle Orthod 1936a;6:198- 208. Tweed CH. The application of the principles of the edgewise arch in the treatment of Class II, division 1: Part II. Angle Orthod 1936b;6:255- 257. Tweed CH. Clinical Orthodontics. Vol. 1-2. St. Louis, CV Mosby Co., 1966. 457 The Baylor Experience Umemori M., Sugawara J, Mitani H, Nagasaka H, Kawamura H. Skeletal anchorage system for open bite correction. Am J Orthod Dentofacial Orthop 1999; 115:166-174. Wehrbein H, Merz BR, Diedrich P, Glatzmaier J. The use of palatal im- plants for orthodontic anchorage. Clin Oral Implant Res 1996;7:410– 416. Welsh RP, Pilliar RM, MacNab I. Surgical implants: The role of sur- face porosity in fixation to bone and acrylic. J Bone Joint Surg Am 1971:53:963–977. Woods PW. A histomorphometric evaluation of mini-implants used as orthodontic anchorage during tooth movement in the beagle dog. Un- published Master’s Thesis, Department of Orthodontics, Baylor Col- lege of Dentistry, 2007. Wright CF. A consideration of the anchorage problem. Angle Orthod 1939;9:152-159. 458 WHAT WE DO KNOW AND WHAT WE DON'T KNOW ABOUT MICROSCREW IMPLANT ANCHORAGE METHODS Mani K. Prakash Anchor management protocols in orthodontic treatment modalities have always been an “Achilles heel.” Much time and effort have been spent on planning and meeting the taxing demands of their execution. However, a new era dawned in “anchorage paradigms” with the wider application of implants as temporary anchorage devices (TADs) in orthodontics. Abso- lute anchorage became a reality with TADs, which made a dream come true – near attainment of Nirvana in orthodontics. A TAD is a device that is temporarily fixed to bone for the pur- pose of enhancing orthodontic anchorage, either by supporting the teeth of the reactive unit or by obviating the need for the reactive unit altogether, and that subsequently is removed after use. Importantly, the incorpora- tion of TADs into orthodontic treatment made possible infinite anchorage, which is defined as zero anchorage loss (implants showing no movement) as a consequence of reaction forces. TADs can be located transosteally, subperiosteally, or endosteally; and they can be fixed to bone mechani- cally (cortically stabilized) or biochemically osseo-/osteointegrated. Cope (2005) classified TADs into two categories, which he further subdivided into types depending on application and usage (Fig. 1). Angle (1907) classified anchorage as: simple – anchor teeth are permitted to tip; reciprocal – reciprocal forces working equally; stationary – if the anchor teeth move, they do so in an upright and bodily manner (more resistant movement). Absolute stationary anchorage was not considered unattainable even then, but the available modalities were not capable of providing it. Many authors reported using conventional osseointegrated implants for intraoral anchorage as early as the mid-forties (Gainsforth and Higley, 1945; Linkow, 1969; Sherman, 1978; Roberts et al., 1994). 459 What Do We Know About Implant Anchorage? | Biocompatible Tabs - Osseointegration Mechanical Retention Dental Implant Palatal Fixation Fixation Onplant | Screws Wires - ! --- - Palatal Implant | ! | Fixation, Retromolar Screws w/ | | Mini Implant | *— screw. - Implants Figure 1. Classification of temporary anchorage devices (TADS) courtesy of Dr. J.B. Cope (2005). Creekmore and Eklund (1983) were the first to use metal screws for intrusion of incisors. The use of mechanically stabilized screws for an- chorage had to wait until the end of last decade to find its due place in the orthodontic paradigm. Umemori and colleagues (1999) reported the use of miniplates for anchorage for open bite correction. The contemporary miniscrew (Kanomi, 1997) and microscrew (Park et al., 2001) made their debut towards the end of the nineties. USE OF IMPLANT'S AS ANCHORS The endosseous (osseointegrated) implants were the first implants to be used for orthodontic anchorage (Fig. 2). These implants worked convincingly as orthodontic anchors, but their use was riddled with many shortcomings in terms of orthodontic applications. These implants had a mandatory need for edentulous space in which to be inserted, either in the arch or distal to it. Such edentulous spaces just were not available in routine orthodontic cases. An additional problem was the excessive waiting period (four to six months) in the midst of ongoing orthproblematic, these implants are very large, i.e., about 4mm or more,odontic therapy for the implants to integrate before they could be loaded, which the orthodontic care delivery could ill afford. Even more problematic, these implants are very large, i.e., about 4 mm or more, 460 Prakash Figure 2. Left: A drawing of an endosseous prosthodontic implant in place. Right: Radiograph of an osseointegrated implant. and required complicated surgical procedures for placement and subse- quent removal. Finally, treatment using these implants was costly. Non-osseointegrated screws that were mechanically stabilized cortical implants appeared to overcome these drawbacks. These implants generally were grouped as cortical screws, miniplates and mini- and mi- croscrews. The broad reference terms used in the literature indicate that Screws that are 2 mm wide or more are classified as miniscrews and those that are less than 2 mm wide are classified as microscrews. The miniplates pioneered by Sugawara (Sugawara and Sugawara, 1999) were fixed to the cortical bone with the help of two or more screws and were good anchors for retracting the entire arch. However, these mini- plates required a more invasive surgical approach than mini- or micro- SCreWS. The initial miniscrew systems came from HDC, Italy; Lomas- Mondeal, Taiwan; and Orlus, Korea (Fig. 3). Many clone-like systems followed. The original microscrew or microimplant anchorage system (MIA) was the AbsoAnchor(R) microimplant from Dentos Inc., Degau, Korea (Fig. 3) The AbsoAnchor(R) system has the added advantage of hav- ing screws with different heads, which allows them to be used for various applications depending on the mechanics (Fig. 4). 461 What Do We Know About Implant Anchorage? | º C | º | º : - : Figure 3. Left: Four types of miniscrews that are currently being used for orthodontic anchorage. Right: The Dentos AbsoAnchor(R) microscrew. BH-L W. - Figure 4. The Dentos Abso Anchor(R) microscrews with different heads for various applications. 4. 62 Prakash Typically, a mini- or microscrew has a cylindrical or tapered body with the required thread for insertion, a head with a grooved neck, and a keyhole through which to thread a ligature wire (Figs. 3-5). The narrowed neck is meant for hooking a spring or elastomerics for traction. The key- hole is an added feature that allows the fastening of these accessories. The screws have either a hex-shaped head or a groove in the top of the head, both of which fit drivers that turn the screw. These mini- and microscrews vary in length (5 to 14 mm) and body diameter (1.2 to 2.0 mm) depending on the applications. The diameter of the head is designed to be little larger (2.5 to 3.5 mm) than that of the body of the screw to stand away from the soft tissue. All of the screws have threads that are conventional or right handed (clockwise turns drive the screw in and counter-clockwise turns pull them out) for most applications. On odd occasions, unconventional or left-handed threaded screws (counter-clockwise turns drive the screws in and clockwise turns pull them out) are used to resist the counter-clock- wise rotary moment. Such moments could result as a reaction to delivered force, which can unscrew and unseat the implant (Fig. 4). ||| ||| || || || ||| | iſ ull Pilot Drills Engine Drivers Hand Drivers | | Figure 5. Different types of pilot drills, engine drivers and hand drivers used with the Dentos Abso Anchor(R) system. 463 What Do We Know About Implant Anchorage? These non-osseointegrated microscrews have the inherent advan- tage of being smaller, which allows them to be placed interradically (with- out the need for an edentulous space). Since they are stabilized cortically, which is mechanical and immediate, the screws can be loaded with no delay. Surgical placement of microscrews entails minimally invasive procedures; their removal is even simpler. More than 90% of screw place- ment is carried out with spray anesthesia. Infiltration is only needed in a negligible percentage of cases. Removal of these screws needs no anes- thesia whatsoever. These screws could easily stand up to 500 g of force without being unseated, and no orthodontic or orthopedic movement ever requires more force than that. And finally, these implants are cost-effec- tive. COMPOSITION OF MINI-/MICROSCREWS The osseointegrated dental implants/screws are composed of 99% titanium. The medical-grade titanium used for general body implants is classified as Grade I to IV. Commercially pure titanium (CP Ti) is used widely as implant material because of its suitable mechanical properties and excellent biocompatibility (Aparicio et al., 2003; Latysh et al., 2006). When CP Ti comes into contact with normal tissue fluids, it oxidizes to form an oxide coating that greatly reduces bio-corrosion, which is its most significant property in terms of its biocompatibility. However, CP Ti has a lower fatigue strength, which has been overcome in prosthetic and other orthopedic applications by using wider and thicker implants, i.e., 4 mm or thicker. In the case of non-osseointegrated mini-/microscrews, use of titanium Grades I to IV resulted in frequent failures as the screws were thinner. Hence the titanium alloy Ti-6Al–4V (Grade V) is the choice for orthodontic screws. This medical grade alloy consists of 90% titanium, 6% aluminum and 4% vanadium (Table I). Using this alloy increased the modulus of elasticity to six times that of bone, so that thinner and longer screws could be used without any risk of breaking (Morais et al., 2007). The alloy supports higher orthodontic loads even though the screws are thinner. LOCATIONS OF THE SCREWS In that the microscrew is small and thin, it is easy to place it vir- tually in any part of the alveolus for its needed mechanical stabilization. 464 Prakash Table I: Classification and composition of various medical grade titanium used for implants. Titanium Medical Grades Grade Grade Grade I | Grade II | Grade III Composition IV V Alloy N (Max.) 0.03 0.03 0.05 0.05 0.05 C (Max.) 0.10 0.10 0.10 0.10 0.08 H (Max.) 0.0125 0.0125 0.0125 0.0125 0.012 Fe (Max.) 0.20 0.30 0.30 0.50 0.25 O (Max.) 0.18 0.25 0.35 0.40 0.13 ſº 5.5 to Aluminum (%) º tºº [ _t * 6.50 i. 3.5 to Vanadium (%) {º ſºn tº ſº 4.5 Titanium (%) 99.5 99.4 99.2 99 89.5 Y.S.(MPa) 170 275 380 485 760 T.S.(MPa) 240 345 450 550 825 Elongation (%) 24 20 18 15 8 Therefore, placement is dictated by the biomechanical needs of any given movement. In the other words, it is entirely operator dependent. In con- Ventional mechanics, the usual site from which the force is delivered to effect the required tooth movement is almost always the molars, which are more or less fixed in their positions. In contrast, the clinician has the option of varying the location of the microscrews that are functioning as anchors in order to serve a given task more purposefully. Hence, care must be taken to modify the biomechanics to suit the varying positions of the anchor screws. The most commonly used sites for microscrews in the maxilla and mandible are listed below. Maxilla 1. Interradicular alveolar areas – between any teeth. The width of the buccal cortical bone on the entire maxillary alveolar process is lim- ited (3 to 4 mm), so longer screws are needed. Most frequently used sites depending on available space are: • between the second premolars and first permanent molars; • between the first and second permanent molars; 465 What Do We Know About Implant Anchorage? • between the two central incisors, which is particularly good for intrusion; or • any other site that suits the needs of applicable biomechanics. 2. The infrazygomatic region – zygomatic buttresses. Access to these areas requires fairly invasive surgery, with reflection of a flap. 3. Palatal areas where the thickness and quality of cortical bone is excellent. However, the overlying gingiva is thick and requires longer im- plants for better purchase in the bone. Commonly used sites are: • the mid-palatine raphe and its neighboring areas, which are good implant sites with predictable retention (Fig. 6); and • lingually between the teeth, areas that generally have good bone with no roots nearby. Care must be taken to avoid the palatine artery that runs about 6 to 8 mm lingually parallel to the lingual gum margins. 4. Retromolar areas, which are commonly used after the extractions of third molars. Figure 6. Mid-palatine areas are good retention implant sites. Mandible 1. Interradicular alveolar areas – between any teeth. The cortical bone on the buccal areas in the mandible is very dense and bulges out. The screws used are shorter, therefore, and the possibility of root contact is remote. Depending on the available space, the most frequently used sites aſ C. • between the second bicuspids and first permanent molars; • between the first and second permanent molars; 466 Prakash • between the two central incisors, which is especially good for intrusion; or • any other site that suits the needs of applicable biomechanics. 2. Retro molar areas, which are commonly used after the extractions of third molars. Interradicular Placements Easy insertion and continued retention of microscrews in inter- radicular sites are the keys to success of implant anchorage in orthodontic therapy. Placing the screws in these sites mitigates the need for invasive surgery and edentulous spaces like those with Osseointegrated implants. Since these implant sites are reasonably close to the arch wire plane, ap- plication of forces to move the teeth and control of the resultant counter forces are much easier. All screws preferably should be thin (1.3 to 1.5 mm) and tapered to prevent accidental root contact. Generally, the length of screws used in the maxilla should be 8 to 10 mm, depending on the application and the density of the cortical bone. Mandibular screws can be shorter (6 to 8 mm) because the bone is rather dense. SCREW ANGULATIONS The cortical bone at the buccal cortex extending from the canine to the second molar is rather thin (2 to 3 mm) in the maxilla. It makes sense to angulate the placement of screws in these interradicular areas to ensure that the screw does not touch the roots and to attain a better purchase of the screw in bone. The space between the roots is shaped like an inverted pyramid, the tip of which is closest to the neck of the adjacent teeth (about 2 mm). The space gradually increases in width to about 5 mm as the roots taper apically (Fig. 7). Placing screws at a 30 to 40 degree angle to the long axis of the teeth (with the tip of screw pointing apically) in the maxilla will keep the screws in the widest available space between the roots apically. It also is prudent to use thin (1.3 to 1.4 mm), tapered screws rather than thick, cylindrical ones (Fig. 8). In the mandible, however, the buccal cortex consists of dense bone and curves out more buccally from the gingival margins. Therefore, the screws can be shorter than those used in the maxilla and the angle reduced to 10 to 20 degrees with little risk of touching roots (Fig. 9). 467 What Do We Know About Implant Anchorage? Figure 7. Left: Interradicular space between the roots in the maxilla. Right: A miniscrew placed too close to the roots in spite of angulation due to its in- creased width. - Figure 8. Top: Interradicular inverted pyramidal area. Bottom: Tapered, thin microscrews duly angulated to keep them away from the roots. 468 Prakash Figure 9. Screws placed in the mandible can be inserted more parallel to the molar roots than screws placed in the maxilla. MICROSCREW DRIVING METHODS Self-Tapping and Self-Drilling Screws The actual insertion of screws into bone depends on the kind of Screws one chooses to use. There currently are two different types avail- able: the self-tapping screw and the self-drilling screw. The initial screws Were self tapping, but as technology has progressed, many manufacturers have switched to self-drilling screws. 469 What Do We Know About Implant Anchorage? The disadvantage of self-tapping screws is that they require the ad- ditional step of pre-drilling with a suitable drill (one that is 0.2 mm smaller than the width of the implant to be inserted) before insertion. Furthermore, it generally is believed that pre-drilling can cause bone necrosis if care is not taken to cool the site with ample circulating coolant. Self-drilling screws do not require pre-drilling. A 0.5 mm deep entry purchase point' with a 1 mm round bur is all that is needed to guide the implant without slipping during the process of insertion. The differences between the self- drilling and self-tapping screws are easily distinguished (Fig. 10). • The tips of self-tapping screws are blunt, rounded and smooth pyramidal, while the tips of the self-drilling screws are sharp, pointed and hooked more like the tip of a corkscrew. e The crests of the threads of self-drilling screws are razor sharp, thinner and pointed, as they must cutthrough the bony tissues, whereas the Self-tapping crests are blunt, thick and rounded. º - A Figure 10. A: Self-tapping screws with smooth, rounded ends. B: Self-drilling Screws with sharp and corkscrew-like tips. 470 Prakash INSERTION METHODS Direct Method With the direct method of insertion, the screws are inserted di- rectly without a ‘stab' incision. This method is used whenever insertion occurs in the attached gingivae. This method is used routinely in almost 70% of implant anchorage cases (Fig. 11). Figure 11. The dentoalveolar areas showing the ‘attached gin- giva (shaded area) and “unattached, free gingival area. Indirect Method The indirect insertion method requires a vertical ‘stab' incision of 2 to 5 mm that reflects a flap and exposes the bone in order to place the Screw. When the screws are placed in the unattached gingivae (including the infrazygomatic area), the incision keeps the soft tissue from becoming entangled with the burs and drills. THE SURGICAL PROCEDURE Anesthetic Methods The use of the conventional method of infiltration anesthesia was extended to the insertion of orthodontic microimplant screws. Many cli- nicians still are comfortable with the depth of anesthetization that it al- lows. In reality, however, orthodontic anchorage screw implantation does 471 What Do We Know About Implant Anchorage? not need that depth; in fact, it can cause problems during insertion. AC- cordingly, the quantity of anesthetic solution injected has been reduced to one fourth of the anesthetic cartridge per site to lighten the depth of anes- thetization. This works to some extent, but the drawbacks still remain. 1. The anesthetization is deep enough not only to desensitize the surface soft tissue, but also to deaden the roots completely. This depth of anesthetization proved to be the nemesis of interradicular placement of screws, which is one of the assets in the current modality. Any contact of the roots and the screw causes eventual failure of the screw due to the jig- gling action of the teeth during mastication. Root contact during insertion goes unnoticed because the patient cannot feel whether or not the screw and root touch due to the desensitization of the roots. 2. Apprehension due to ‘pin prick' psychosis often leads patients to refuse the entire implant option. Such issues led clinicians to try alternate anesthetic methods, the front runner of which was “spray” anesthesia. The 2% Lidocaine solution that is used routinely prior to pin prick infiltration proved to be totally ineffective. After experimenting with several strengths of Lidocaine, it became evident that a 15% Lidocaine solution provides sufficient anesthe- tization of the soft tissue and does not affect the roots or apices. The only down side is that it takes about five to seven minutes for this drug to kick in. A short burst of spray at the site will provide sufficient time (approxi- mately 20 to 30 minutes) for the clinician to finish the procedure. Any root contact during insertion of the implant will cause an instant pain response from the patient. All the clinician has to do is withdraw the screw a bit and direct it away from the offending roots. This seems to be the best available, built-in alarm system for preventing implant failure. To eliminate the waiting period of five to seven minutes, the clini- cian can apply a pre-anesthetic gel of 20% Benzocaine at the site before spraying the Lidocaine. Benzocaine is quick acting, but it only lasts for about five to six minutes, which is not enough time to complete the pro- cedure. Self-drilling With No Pre-drilling The actual steps for self-drilling with no pre-drilling are: 1. Swab the lower face externally with a suitable antiseptic solu- tion. 472 Prakash 2. Ask the patient to rinse thoroughly with Chlorhexidine for a minute or two. 3. Anesthetize the area with a 15% Lidocaine anesthetic spray and wait for five to seven minutes for the spray to take effect. Use infiltra- tion anesthesia if indicated, but make sure to use only one fourth of the cartridge per site. 4. Map the site of entry accurately by locating both the contact point with help of a perio-calibrated probe and the roots using finger pres- sure. True periapical radiographs are helpful; CT scans of the area can be even more helpful. Once the entry site is located, make sure to mark it with a fine indelible marker dye such as gentian violet to keep it visible throughout the entire procedure. 5. Make a registration point at the denoted entry point with the help of a 1 mm round bur fitted with a reduction handpiece with run- ning cold saline sprayed at the site (Fig. 12A). The ratio of reduction of the handpiece should be approximately 64:1, like that which is used in endodontic or surgical applications. This reduction handpiece reduces the speed from 40,000 rpm to about 500 rpm mechanically with a correspond- ing increase in torque. 6. Load the selected microscrew into the driver and insert it at the registration point. The direction of insertion is first horizontal and then angulated per the requirements of the site (Fig. 12B and 12C). This keeps the screw from slipping during insertion. The act of turning should be smooth alternating between turns and stops. There should be no “wobble” in the axis of the driver to ensure proper stability of implants. 7. The final rest position of the screw should be such that the curved funnel at the neck should be butting against bone. The head, neck and the hex of the screw should be away from the soft tissues (Fig. 12D). Additional Steps for Self-tapping with Pre-drilling There is an additional step for insertion of self-tapping screws that occurs after Step 5 listed above. This step consists of pre-drilling after making the registration point. Using the same reduction handpiece cited in Step 5 above, load a suitable pilot drill (0.2 mm thinner than the implant to be used) and drill with a slow, interrupted action to a depth that is about 2 to 3 mm shorter than the length of the selected implant cooling the site with copious amounts of saline (Fig. 13). Proceed with Steps 6 and 7 listed above. 473 What Do We Know About Implant Anchorage? a --- - - Figure 12. A: Making a registration point with a 1 mm round bur. B: Driving the screw in and angulating it as needed, with coolant sprayed on the site. C. Final tightening of the screw. D: Microscrew in situ. Figure 13. Angulated pre-drilling is added after mak- ing the registration point and before inserting the Screw when using the self-tapping method. 474 | Prakash For Step 5 in the case of free gingival entry, the clinician must make a vertical incision of 2 to 5 mm in length at the site and then separate the two edges of the flap to gain entry to make the registration point. REMOVAL OF MICROSCREWS Once treatment requirements have been fulfilled, the screw must be removed. Removal does not warrant any anesthesia as the bone in which it is lodged has no sensory fibers. Simply fit the driver to the screw and unscrew it. The healing process following removal usually is eventless. There are some instances in which the screw may need to be removed before treatment requirements are fulfilled. • If the screws come loose, the implant can be withdrawn a few millimeters and its direction changed to acquire additional purchase. No anesthesia is necessary as the screw has not been withdrawn from the mu- cous membrane. However, if the screw has come out of the mucous mem- brane, spray anesthesia is needed to gain new entry. • Occasionally a screw may interfere with easy movement of the teeth and must be repositioned. • In rare cases, gingival inflammation may necessitate screw re- moval. SOME CLINICAL CONSIDERATIONS Implant Fractures Fractures are not common if one is diligent. The usual causes of fractures are the need for excessive torsional force during insertion and an occasional unyielding and dense cortical bone. In such cases, it is wise to pre-drill before insertion, drill slowly in fits and starts and do not add excessive torque when turning against heavy resistance. In the unfortu- nate event of a screw fracturing, it is best to remove it immediately. This entails further digging around the broken implant to gain enough grip for removal. Gingival Impingement and Inflammation If the host tissue is not periodontally sound initially, the implant may lead to further swelling and complications. It is good practice to keep the site healthy before beginning treatment. Good, soft brushing and water irrigation of the site will keep it healthy. If the head of the screw ever gets submerged in the gingival tissue, Surgically exposing the screw 475 What Do We Know About Implant Anchorage? using anesthetic spray and covering the implant site with periodontal paste for several days will shrink the tissues. Loosening of the Screws The probable causes of screws coming loose on their own are: • Root Proximity. When an implant is close to or in contact with the root(s), most screws will loosen within 24 to 48 hours. In a small num- ber of cases, it could take longer. This is because of the hammock-like effect of the periodontal membrane. The easiest solution is to change the angle of the screw so that it does not come into contact with the root. • Cortical Bone Quality. It is not possible yet to predict precisely the quality of cortical bone. If the bone is not dense enough, the implant can fail at any time during the progress of mechanotherapy. In such cases, the clinician can try alternate sites and succeed, as the quality of cortical bone is not uniform. Injury to Other Anatomical Structures There is little chance of injuring other anatomical structures if care is exercised during the planning and insertion stages of implantation. Osseointegration Osseointegration definitely is not encouraged with orthodontic implants, e.g., surface coating, etc. However, if an implant is left in place long enough, partial or full integration may occur. If it appears necessary to do so, a few turns of the screw will break the bonds. COMMON APPLICATIONS FOR MICROIMPLANT ANCHORAGE METHODS Unlike conventional mechanics, microimplant anchorage makes all tooth movements easily possible without creating any effect on the molars. These movements include: • anteroposterior movements of a tooth or groups of teeth, • uprighting, distalizing and any form of mesial or distal move- ments of molars, • intrusion/extrusion of a single tooth or multiple groups of teeth, 476 Prakash • augmenting the existing dental anchorage capability by using the implants as a source of indirect anchorage, • acting as the sole source of anchorage for tooth movement. Microscrew Applications from a Clinical Standpoint Distalizing and Uprighting Molars. A 22-year-old female patient (Case 1), who had a history of previous, unsatisfactory orthodontic treat- ment, desired additional orthodontic treatment. She had a Class II maloc- clusion with a deep bite, increased overjet, and a convex facial pattern with a deficient chin (Fig. 14A). The maxillary first premolars and man- dibular first permanent molars had been extracted previously as a part of the earlier orthodontic treatment. She had an almost horizontal impaction of the mandibular left third molar which was locked under the left second molar (Fig. 14B). Treatment objectives included correcting all of the orthodontic deviations conventionally and using a single microscrew to distalize and sufficiently upright the impacted mandibular left third molar to align and bring it into a Class I occlusion. After aligning the maxillary arch, the impacted mandibular left third molar was bracketed suitably and an uprighting spring was attached to it. The mesial end of the spring was terminated at a bracket type (BH- L). A left-handed microscrew was inserted between the second premolars and the second molar to achieve some direct uprighting of the molar (Fig. 14C). After all of the lower teeth were bonded, the direct anchorage was converted into indirect anchorage to upright and distalize the left third molar. The molar uprighting spring was replaced with a rigid .016 x 022.” stainless steel wire, which had both of its ends curved into round hooks and which had been sand blasted for bonding. The distal end of the wire was bonded to the mesiobuccal surface of the second molar, and the mesial end to the neck of the microscrew, which now was shifted to a site between the premolars (Fig. 14D). This resulted in a temporarily ankylosed-like stabilization of the second molar. Any kind of mesial or vertical move- ment of the molar was prevented by fixation with the microscrew, mak- ing the molar an ideal anchor unit. An open-coil spring was compressed between the mandibular second and third molars, with the continuous arch wire threaded through their attachments (Fig. 14E). The open-coil spring distalized and uprighted the terminal molar significantly without produc- ing an effect on the anchored second molar or the anterior segment (Figs. 14F-H). 477 What Do We Know About Implant Anchorage? 478 G | H - Figure 14 (Cont.). C: Direct anchorage from the screw to the upright third molar using a spring. D: Indirect anchorage to stabilize the second molar with a piece of .016 x 022” wire bonded to the mesiobuccal surface of the second molar and the mesial end to the neck of the microscrew. E. An open-coil spring compressed between the two molars to distalize and up- right the third molar. F. The third molar uprighted and distalized significantly without any reaction on the anchor second molar. The microscrew was removed at this appointment. G. Pretreatment pan radiograph of the left buccal areas. H. Ra- diograph of the same area post-distalization and uprighting of the lower third molar. What Do We Know About Implant Anchorage? Mesialization and Uprighting Molars. A 13-year-old female pa- tient (Case 2) presented with a Class I molar occlusion, a deep bite, Severe crowding in both arches, maxillary canines blocked labially, a convex fa- cial pattern and incompetent lips (Fig. 15A). The mandibular right first molar was deeply carious with no hope of restoration (Fig. 15B). The treatment plan consisted of extraction therapy to correct all of the orthodontic deviations. Accordingly, the maxillary left and right first premolars and the mandibular left first premolar and right carious first permanent molar were removed. After 18 months of conventional fixed appliance therapy, all of the treatment objectives were met except for the correction of the position and inclination of the mandibular second molar (on the side of the extraction of the first permanent molar). This second molar was tipped considerably (crown mesially and root distally) caus- ing inadequate contact with the mandibular right second bicuspid. There was some residual space between these two teeth (Fig. 15F). At this point in treatment, a right-hand threaded bracket head microscrew was insert- ed between mandibular first and second premolars (Fig. 15C). A simple cantilever spring was designed to engage the molar tube distally and the bracket head of the screw mesially. This spring uprighted the second molar sufficiently. The molar tube then was offset increasingly (mesial end gin- givally) to obtain additional uprighting moments. The residual space was closed by using a closing loop at this site (Fig. 15D). The uprighting of the molar and root paralleling achieved was far superior to that achievable using conventional mechanics (Figs. 15E-G). Distalizing the Buccal Segments. A 20-year-old female (Case 3), who had undergone four first premolars extractions and orthodontic treatment eight years earlier, presented with significant relapse. She had a prominent nose, a moderately prominent chin, some flattening of the dentoalveolar region and incompetent lips (Fig. 16A). She had a Class II occlusion, a deep bite and dentoalveolar proclination of her maxillary teeth (Fig. 16B). Because additional extractions were not advisable taking into consideration the facial features, it was decided to extract both of the maxillary third molars and distalize all of the maxillary teeth to correct the anterior malocclusion (Fig. 16C). The case was suitably bonded/ banded with .018” MBT prescriptions and ceramic brackets that pro- 480 Prakash duced the needed initial alignment. Two microscrew implants (1.4 mm x 8 mm) then were inserted in the retromolar area about 5 mm distal to the maxillary second molars (Fig. 16D). Though access for insertion of these screws was achieved occlusally, the implants were placed as far buccally as possible to avoid any toe-in effect on the distal molars during traction. The distalization of the teeth was accomplished in segments. Initially the second and first molars and the second premolar were distalized together. A NiTi closed coil spring was stretched from the implants to the respective molar hooks (Fig. 16E). When sufficient space had been opened between the second premolar and the canines on either side, the distal segments were tied back to the implants. The anterior retractions then were effected from the distal segments (Figs. 16F–G). The buccal occlusion changed from a Class II to an ideal Class I occlusion (Figs. 16H-J). The post-treat- ment facial views of this patient show favorable and acceptable changes (Fig. 16K). The difficult, almost impossible movements were achieved easily with the help of microscrew implants. Maximum Retraction With No Anchorage Loss. An eleven-year- old girl (Case 4) was brought in for orthodontic treatment by her parents. She had a severe facial deformity due to excessive bidental-bialveolar prognathism that produced severe convexity of her face with short and incompetent lips, a deep bite, large teeth and increased overjet (Figs. 17A–B). The patient exhibited psychosocial symptoms related to her im- balanced facial appearance. The treatment plan consisted of four first premolar extraction therapy. However, considering the extent of the correction required, it was decided to augment conventional retraction mechanics by placing one mi- croscrew in each quadrant. The microscrews would provide the needed anchorage so that the molars would not be taxed in any way. This protocol would allow the entire extraction space to be used for maximum retrac- tion, thereby effecting considerable facial improvement with no conven- tional anchorage loss. After initial leveling, microscrews were inserted into each quad- rant between the first permanent molar and second premolar. With the im- plants providing direct anchorage, suitable forces were loaded from the implants to hooks on the archwire for retraction (Fig. 17C). A remarkable amount of retraction was achieved in a short time, resulting in a significant improvement in the patient’s appearance (Fig. 17D-H). 481 - | - - * , , Figure 15. A. Case 2 pretreatment intraoral views. B. Pan radiograph of the patient showing a deeply carious lower right first permanent molar. C. Molar uprighting spring engaging the microscrew inserted between the premolars. This spring up- righted and mesialized the molar. D. The remaining space was closed with the help of a closing loop in the archwire. : Figure 15 (Cont). E. Post treatment intraoral views showing the lower right second molar mesſalized and uprighted. F. Pan radiograph showing the mesially-tipped lower right second molar after the conventional fixed appliance treatment. G: Post- treatment pan showing good uprighting and mesialization of the lower right second molar with excellent root paralleling. : : C: Ceph and radiographs showing C supra-erupted maxillary third molars. clusal view of the study model of the maxilla showing the third molars. º º - - - - - . Figure 16 (Cont). E. Maxillary occlusal view showing microscrews inserted 5 mm distal to the second molars. A closed coil spring is attached from screw to first molar hook on both sides. The consolidate buccal segments show distalization. F. Distalization and opening of space between bicuspid and cuspid after three months of treatment. G. Post-treatment view. : Class I after three months of distalization. : improvement. Figure 16 (Cont.) J. Post-treatment intraoral buccal views. K. Post-treatment facial views showing good facial : What Do We Know About Implant Anchorage? | |- 8 SAAQA [eſpēj ļūQUūļeº IſºId + ºseO · F · LI QInãIJ 488 Figure 17 (Cont). C: Microscrews inserted between the first permanent molar and second premolars in all quadrants. Closed- coil springs stretched from the microscrews to hooks on the archwire to deliver the necessary forces directly. D: Post-treat- ment intraoral views showing maximum retraction of the anterior teeth. : F Figure T7 (Con1), E. Post-treatment facial views showing enormous facial changes. Pretreatment (F) and post-treatment (G) cephalograms showing favorable change. H. Superimposition of pre- and post-treatment cephalograms. (Continuous lines denote pretreatment and dotted lines denote post-treatment) - s Prakash CONCLUSIONS • The concept of absolute anchorage is a reality and easily achiev- able. • Retractions can be achieved en masse with easy sliding mechan- ics with no need for conventional anchor-enhancing methods. • Microimplant anchorage can be used with suitable biomechan- ics and can be adapted successfully to fit currently practiced mechano- therapy protocols. • All methods are intraoral and produce no untoward impact on molars, allowing the complete use of extraction spaces for retraction or crowding corrections in severe discrepancy cases. • Virtually any area in the alveolar skeleton is a potential anchor- age site that can be used to support and dissipate anchor forces remotely either directly from the microimplant (direct anchorage) or via stabilized molar or buccal segments (indirect anchorage). • There is a definite reduction in treatment time due to rapid and uninterrupted movements, with no loss of time due to misdemeanors in anchor protocol. • Conventionally perceived impossible movements now can be achieved with ease. • There is an increase in the scope of camouflage treatment op- tions available in the realms of surgical treatment. Issues that need further scrutiny include: • The probable reasons for microscrew failure are (1) root prox- imity to the inserted implant and (2) the variability of bone density at any given site, which is difficult to predict before insertion. • The amount of anterior tooth retraction supported by microim- plants typically is significantly greater that which can be achieved through Conventional orthodontic mechanics. Such retraction with implant sup- port can result in over-retraction at times, indicating a need to rethink the eXtraction decision in some patients. REFERENCES Aparicio C, Gil FJ, Fonseca C, Barbosa M, Planell JA. Corrosion behavior of commercially pure titanium shot blasted with different materials and sizes of shot particles for dental implant applications. Biomateri- als 2003:24:263-273. 491 What Do We Know About Implant Anchorage? Cope JB. Temporary anchorage devices in orthodontics: A paradigm shift. Semin Orthod 2005; 11:3-9. Creekmore TD, Eklund MK. The possibility of skeletal anchorage. J Clin Orthod 1983; 17:266-269. Gainsforth BL, Higley LB. A study of orthodontic anchorage possibilities in basal bone. Am J Orthod Oral Surg 1945:31:406-417. Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod 1997:31:763-767. Latysh V, Krallics G, Alexandrov I, Fodor A. Application of bulk nano- structured materials in medicine. Curr Appl Phys 2006;6:262-266. Linkow LI. The endosseous blade implant and its use in orthodontics. Int J Orthod 1969; 18:149-154. Morais LS, Serra GG, Andrade LR, Palermo EFA, Elias CN, Meyers M. Titanium alloy mini-implants for orthodontic anchorage. Immediate loading and metal ion release. Acta Biomaterialia 2007;3:331-339. Park HS, Bae SM, Kyung HM. Microimplant anchorage for treatment of skeletal Class I bialveolar protrusion. J Clin Orthod 2001;35:417- 422. Roberts WE, Nelson CL, Goodacre C.J. Rigid implant anchorage to close a mandibular first molar extraction site. J Clin Orthod 1994:28:693- 704. Sherman AJ. Bone reaction to orthodontic forces on vitreous carbon dental implants. Am J Othod 1978;74:79-87. - Sugawara, J. Dr. Junji Sugawara on the skeletal anchorage system (JCO interviews). J Clin Orthod 1999:33:689-696. Umemori M, Sugawara J, Mitani H, Nagasaka H, Kawamura H. Skeletal anchorage system for open bite correction. Am J Orthod Dentofacial Orthop 1999; 115:166-174. 492 THE EDGEWISE TEMPORARY ANCHORAGE DEVICE Terry R. Pracht During my thirty-five years of practice, many advances have occurred in Orthodontics: direct bonding instead of banding, preadjusted appliances, advances in orthognathic surgery, and high-tech archwires. All of these have made things better for me and for my patients. But nothing new has come along during my career that has allowed me to do so much more for my patients than temporary anchorage devices (TADs). And now there is a microimplant system that is totally compatible with edgewise ortho- dontics; a microimplant with tie wings and both a rectangular slot and tube; a microimplant you can use exactly as you would use a bracket on a tooth or a tube on a molar band. This system is the Quattro"M (Mondeal Medical Systems, Tuttlingen, Germany). It is available in either an 018” or an 022” slot prescription. Manufactured in Germany with the highest Strength medical grade titanium from the US, the Quattro System has pre- cise instrumentation making insertion predictable and easy. WHICH SYSTEM IS BEST? While there are a number of microimplants and orthodontic an- chorage systems available, the characteristics of the individual microim- plant matter: diameter, length, thread count and pitch. Science is showing us that smaller is not necessarily better. In fact, most microimplants used Will be either 1.5 mm or 2.0 mm in diameter for most applications. If the microimplant is much smaller, the risk of breakage increases dramati- cally. Because orthodontic microimplants do not osseointegrate, the key to retention seems to be the number of screw threads going into the cortical bone. Thus, thread count and thread depth are important. Screws gener- ally are getting shorter these days, although this could change as technol- Ogy allows us to predict which screw lengths will engage both buccal and lingual cortical plates accurately. The pitch of the thread is important as Well. Amazingly, after only one or two revolutions, the proprietary cutting tip of the Quattro engages the bone and the screw then pulls itself into the bone with virtually no pressure. 493 Edgewise Temporary Anchorage Device TO DRILL OR NOT TO DRILL'? Most of the time, the Quattro"M can be inserted using a “self-drill- ing” technique for which no pilot hole is required. Occasionally, a small pilot hole (just through the cortical plate) can be helpful. This is called a “self-tapping” technique. In exceptionally dense bone, which is found most commonly in the anterior and posterior mandible, the self-tapping technique may be required. In most other areas, the screws can be inserted using the self-drilling technique. There virtually is never a need for a Sur- gical flap, even in unattached mucosa or at the mucogingival junction. Screws commonly are used both in tooth-bearing areas and non- tooth-bearing areas. The most common areas are between the roots of the second premolars and first molar or in the infrazygomatic crest or man- dibular oblique ridge. However, they can be used successfully in many different areas. In my practice, the workhorse is the 1.5 mm diameter screw that is 7 mm in length. This is the screw we almost always place between the roots of the teeth. In most other areas, we use the 2 mm diameter ScreW that is 9 mm in length. In rare situations where the soft tissue is unusually thick, such as the palate or retromolar pad, the 11 mm length screw may be necessary to penetrate the tissue far enough to ensure that a sufficient number of threads engage the bone. ATRAUMATIC INSERTION PROTOCOL After trying numerous techniques, I have now developed what I call an “atraumatic insertion protocol.” We first have the patient rinse with a fairly concentrated solution of Listerine"M or Chlorhexidine". We then use a potent topical anesthetic called TAC. We wait three minutes for the TAC to take effect and then infiltrate near the apex of the tooth in the implant site with about one fourth of a carpule of Lidocaine without a vasoconstrictor. The injection ensures that the patient will feel absolutely nothing but that they will not be numb for a long period of time postop- eratively. There is no need for a long-acting anesthetic or for a block injection. We wait five more minutes and then literally “shove” the micro- implant through the soft tissue. Because the microimplant is sharp, it does all of the work for us. We have determined that this gives us the best clini- cal result with virtually no bleeding. There is no need to make an incision or to use a bur or tissue punch to penetrate the soft tissue. 494 Pracht We continue pushing firmly as we begin to turn the screw clock- wise. After about two revolutions, the screw pulls itself the rest of the way into the bone with virtually no pushing whatsoever. We continue turning the screw until the shoulder of the implant is near the surface of the soft tissue. We then remove the instrument and determine how close we are to the soft tissue. We continue to turn the screw until the shoulder is in contact with the tissue or there is very slight blanching of the tissue. We then make the final adjustments to align the slot and tube of the implant so that they are parallel or perpendicular to the archwire, depending on the application. POST-OPERATIVE MANAGEMENT Patients report little discomfort after the placement of the screws, which requires nothing more than their headache remedy of choice. Of course, we emphasize that excellent oral hygiene protocols with a soft brush must be followed. Clinicians may wish to place their patients on a warm salt water rinse for a day to two. I write a prescription for a 16 Oz bottle of Chlorhexidine" and have our patients rinse with it once- or twice-a-day until the bottle has been used completely. DIRECT VERSUS INDIRECT ANCHORAGE Most of the applications we have seen reported in the literature il- lustrate using the microimplants as a direct anchorage source, i.e., literally pulling directly on the microimplant to accomplish the desired treatment Outcomes. It is important not to lose sight of the possibility of using mi- Croimplants for indirect anchorage. Tying a tooth or a group of teeth you do not want moved to a microimplant (essentially ankylosing them) allows you to use more conventional mechanics to resolve common clinical situ- ations. A classic example would be “ankylosing” a mandibular first molar With a microimplant to use it as anchorage to upright an impacted second molar. THE POSSIBILITIES STILL ARE EVOLVING Other uses of TADs can address problems not addressed easily With traditional orthodontic mechanics, situations such as: • the patient has few or no posterior teeth that could be used as an anchorage Source, 495 Edgewise Temporary Anchorage Device • the patient has extruded or unopposed maxillary posterior teeth, • the patient has impacted second molars, • the patient has ectopic canines, especially in an open bite case in which ankylosis and/or keeping the occlusal plane level are COncerns, • the clinician wants to close spaces caused by missing molars or premolars. These are only a few of the challenging clinical situations we encounter everyday where the use of microimplants is becoming common. Even more exciting is the possibility of using microimplant an- chorage to level canted occlusal planes without orthognathic Surgery. We can correct an excessive gingival display (“gummy Smiles”) without Sur- gery. We can close spaces caused by missing molars or premolars in pa- tients who have concave facial profiles with no retraction of the anterior teeth by placing the forces apical to the center of resistance, thereby allow- ing protraction of posterior teeth “root first.” We can simulate the results attainable with orthognathic surgery without having the patient undergo surgery in some clinical situations. This helps with the ethical dilemma of “to treat or not to treat” patients who clearly need surgery, but who do not want or cannot afford surgery and request camouflage treatment as an al- ternative. Now there may be a “middle ground” in selected cases in which a non-surgical option may produce acceptable results. - Will microimplants eliminate the need for extractions or orthog- nathic surgery? The answer is no, but borderline orthognathic cases can become non-surgical cases and borderline extraction cases can become non-extraction cases. CAN THERE BE COMPLICATIONS''' There can be complications, of course, but there is little morbid: ity reported in the literature. The most common complication is a loose screw. However, the occurrence of a loose screw is thought to occur less than ten percent of the time and usually can be resolved by simply placing the next larger diameter screw back in the same hole — really no more inconvenient than a loose band or bracket. And with the new enhanced “shoulder” design, tissue overgrowth is rare, even when screws are placed in alveolar mucosa. 496 Pracht QUESTIONS THAT WE NEED TO ANSWER Are orthodontic microimplants here to stay? My answer definite- ly is yes. Will microimplants allow us to do things for our patients that we could not do before or that we could do, but now can do in a less invasive way? Once again, my answer definitely is yes. Will we be using microimplants in our orthodontic practices? My answer is probably, because the doctrine of informed consent requires us to advise our patients of all available treatment options including the op- tion of no treatment. g So, the only unanswered question is, “Will we be placing the mi- croimplants ourselves?” My answer to that question would be hopefully yes, because it is remarkably easy to do. 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