Biomed, WU 500 lUTHERM REGIONAL LIBRAR / f ACjUT ' G 000 005 649 9 THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES s^^y V iisrsTRUCTioisrs FOR MOUNTING iSfifiSiai. If ^ CHEOPLASTIC PROCESS. BALTIMORE: PRINTED BY JOHN W. WOODS 1867. sou l^^7 INSTRUCTIONS FOR THOSE MOUNTING TEETH CHEOPLASTIC PROCESS For a fall upper, loioer or double set- — Take the im- pression as usual, in wax or plaster ; plaster being generally preferred, from its greater accuracy, and of course to be preferred for this process, as the superior fit results from the metal giving the exact counterpart of the impression/ ^Surround the impression as high as its margin, with softened putty, or any plastic substance, as clay or dough, {puttyhQiYig the best, and easily procured, from its greater cleanliness, the facility with which it is kept in constant readiness for use by oiling and beat- 1. For deep palates, raise the centre of the impression cup with wax, some using before introducing it a spatula to cover the roof of the mouth with plaster. Salt should be used in plaster to quicken the set. Sulphate of potash is said to be better for this purpose as free from taste. It s^^ould be mixed thin, stirred until it begins to thicken and used expeditiously. In four or five minutes it will be hard. 2. The impression, if of plaster, should have the chamber or central cavity cut at this time and well varnished so as to afford an easy delivery of the cast to be made from it. If of wax, the chamber cut with a sharp blade suitable for this purpose and slightly warmed, thus any form of cavity is easily given and shaped as required with sharp or even acute edges, or rounded as the operator requires. ing, when it acquires a dryness, then kept covered by water, a small quantity can be used for months, with- out loss or objection,) it should be so surrounded as to allow the placing of a tiyi rim, as represented in the following cut. Great care should be taken to use a ring that will surround the impression fully a \ of an inch and at least 1 in. or 1^ in. behind the termination of ridge as represented, this is to allow of a partition sur- face for the two parts of the matrices to divide upon, and the enlargement behind the ridge to afford depth for gate as well as for articulating surface needed in taking the bite of the mouth. Cut 1 represents the impression of the mouth ; fig. 3, surrounded with putty ; fig. 2, as high as the margin, with a tin rim ; fig. 1, lightly imbedded, so placed as to allow of }4, to 14 in. around and 13^ in. behind the impression; fig. 4 shows the chamber or air cavity previously cut. nen The impression should now be oiled, as well as all surfaces exposed inside of the ring, which is now pre- pared to receive the plaster and spar, generally used in equal jDarts by weight, well mixed and made about as liquid as cream, with pure water, when it should be poured and kept stirred into the impression with a camel's-hair pencil or feather until it has began to set, then filled to the depth of | of an inch. If properly stirred, it will come away from the impression with a perfectly smooth surface, free from all bubbles or wanting parts by confinement of air, which of course is a great necessity. When hard, remove the ring and putty and carefully separate the cast from the impression, which need not necessarily be sacrificed, but in cases of very projecting alveolus, the impres- sion should be cut through until th6 color of the var- nish is reached, at those points where the ridge binds in the impression, then by gently tapping the part cut, it will break off in such a manner as to be read- ily replaced, and thus permit any number of casts to be taken from the same impression. The air cavity can now, if necessary, be somewhat altered by trim- ming, and made perfectly smooth. This cavity should always be made previous to obtaining the composition cast, but when omitted can be formed by placing a flattened plate of wax with the size and form of the desired chamber cut from it, the thickness of the wax representing the depth of the air cavity ; press the wax down carefully upon the cast, the chamber being placed in its proper position, then moisten the sur- face of the cast within the wax and pour a sufficient amount of the plaster and spar to fill the space ; when sufficiently hardened, warm the wax and remove it, leaving, if carefully done, a good substitute for a chamber formed in the impression. Casts made of the foregoing are not as hard, when ordinarily formed, as when made of plaster only, but sufficiently so for all purposes, and when hardened by the use of 'Fuch's soluble glass, possess a much great- er density and strength than can ever be required. I have made many sets of teeth by this means, upon the same model and left them still good. To form the pattern of plate, at the same time afford means for obtaining the articulation or bite of the mouth, a material must be used that permits an accurate adaptation, and at the same time not re- quiring iDressure to obtain this accuracy, otherwise the perfection of the whole process would be impeded, this is fully accomplished by using wax rolled into sheets ^^^ inch thick, and sufficiently large as to cover the required surface of cast, (Cut 2,) the cast is first protected by modeling down upon it a plate of tin Fig. 2. foil, such as is used by druggists, with the finger as- 1. This is made by fusing 15 parts pulverized silex or pure sand, 10 parts of carb potashes, 1 part of pulverized charcoal, well mixed and thoroughly vitrified in a white Hessian crucible, previously washed with good clay and luted. The glass is then taken from the crucible, cleansed and pulverized, the impurities must now be dissolved out by cold water, and when thoroughly washed may be dis- solved in hot water. In using, it must be diluted in small quantities and brushed over the surface of the cast. Some use carb. potash 70 parts, carb. soda 54 parts, silex 152, Cut 2 is the thickness of wax plate used, and is made by rolling wax, that is not cold but just free from coldness, upon a smooth board and wooden roller, bathed in lukeioarm water. Worked at this temperature it becomes tough. sisted by a hard roll of soft leather, (Cut 3,) the Cut 3. sheet wax is then carefully modeled down upon the tin foil plate, and neatly trimmed to the size and ex- tension of the metal plate, (Cut 4,) for all upper sets Cut 4. form a second tin foil plate upon the wax and then place a rim of wax for the impression of the lower teeth as in old processes ; this rim must be carefully Cut 3. Are made of lightly rolled chamois leather, used for shading in draw- ing and are called dubbs. The large size is made more blunt than the figure for pressing the foil and wax plate down upon the cast. The smaller for pressing the strips of wax between the teeth upon the outside, both prove very servicea- ble. Can be had at drug stores generally. Cut 4. Shows the wax plate, letter D covering the tin, with the chamber B, raised above the composition cast, which gives the thickness required in this cast. 6 trimmed to the desired length and fulhiess. To stiffen the plate, warm a small ball of wax until it has become soft and pliant, then press it with care all over the surface of the upper tin plate inside the rim, cool it in water forming a plate that the most difficult articulation can be taken with never failing certainty, (Cuts 5 and 6.) Taking it from the Cut 5. mouth it is placed upon the cast, (a fac simile,) two or three small holes are now formed upon the part extending one and a half in. behind the plate for articulating surface ; putty is built around the out- side and a little above the rim of wax carrying the impression of the lower teeth, and continued back behind the cast so as to surround the surface wherein the holes have been made, the whole surface within the putty is oiled and carefully filled with plaster. Cut 5. A is the cast with the holes to fix the cast about to be taken. D the pjate of tin foil and wax covered with tin, B the chamber, and C the rim of wax trim- med to take the impression of the lower teeth which are imperfectly represented. When hardened, the putty is removed, the plaster model of lower teeth is carefully separated from the composition cast, wax rim cut off, wax stiffener and Cut 6. upper tin plate both removed together, when you have the wax pattern plate ready to receive the teeth as represented in Cut 7. It would be well to place upon the foil plate before fitting the wax, one or two narrow strips of foil over the prominent ridges of the alveolus, so that in ad- justing the teeth the proper space may not be de- creased from under them, which is almost unavoida- ble where the alveolar border is sharp or pointed. The several layers of foil will prevent this space be- tween the base of the teeth and the cast, being so much lessened as would exclude the metal flowing at such points. Without this care a beginner will Cot 6. Is the same, only stiflfened before placing in the mouth by the softened wax, E. be liable to press the wax from under the teeth so much as to produce holes in the plate at such points, as well as the want of metal forming the pins through the teeth, lateral grooves, or dovetails, as the case may be. Cut 7. The process for obtaining the articulation in a dou- ble set is much the same as in all methods ; the plates are made as before described, a tin foil plate mod- eled upon both casts followed by the wax plate, which is' again covered by foil (to protect it from in- jury, by the adhesion of the subsequent wax placed upon it and to admit of its being easily removed,) rims of wax are neatly trimmed and modeled upon these plates, which must now be strengthened by strips of wax or better as before described, that is filling inside the rim, softened wax so as to cover the whole plate which is protected as remarked by the foil from injuring the wax plate beneath. Cut 7. A cast j D wax plate ready to receive the teeth; E is the plaster model of lower teeth and articulated to the composition cast by means of the projecting surface having small holes for dowel pins to enter, which are made in the plaster cast as described. 9 To strengthen the lower plate, if the rim of wax is not sufficient, take a narrow strip of any metal which may be bent into the desired circle, so as to fit along the inside of the plate as low down as con- venient, it is then covered over and miited to the foil plate by warm or melted wa:^, so that this metal rim must be bent before position of plate can be disturbed. If the outside of the plate be broad, it should be stiffened by making the rim of wax cover it. The plates are placed in the mouth and the rims of wax are altered, if need be, to rep- resent the proper length of the desired teeth and made to close so as their whole surfaces strike even- ly at the same time. The patient should be made to close the mouth with a careless rapidity, the ope- rator can thus see the true position, and marking the wax rims by lines crossing at various points, com- me7ici7ig icitJi the median line. The plates can be re- moved from the mouth separately and placed to- gether as in the mouth with certainty, firmly held in this adjusted position by melted wax ; place the upper plate upon its cast, with the under one thus attached ; fill in with putty the space presenting in- side the plates back to the articulating surface form- ed in the upper cast, and as high up as the inner edge of the lower plate, then with the aid of the tin rim placed around the upper cast, but placed so as to extend a little above the outside edge of lower plate, then all unnecessary spaces filled with putty, the whole surface oiled, or washed with thick soap water and plaster poured in, which forms with the addi- tion of but one cast, the correct articulation for a 10 double set. Of course the usual processes can be used if preferred, as wholly of two plaster casts, or with the hinged metal articulator. After harden- ing and sejDarating, remove the rims of wax and stifFeners as before described, leaving the wax plates ready for the adjustment of the teeth. It would be well to add, as recommended in former book of instruction, a strip of soft wax to the rims used in getting bite of the mouth, or impression of lower teeth, so that the rims, or the lower teeth, may im- Cur 8. Cut. 9. Cut 8. A represents a plaster articulating model, with the wax rims too long in front, requiring to be cut down so as their whole surfaces should touch ; A and B, the upper and under halves ; a, the edges of wax plate ; b, the plate with wax rims resting upon them. The two first models represent the rims as they may be in the mouth. Cut 9. The same, with wax rims adjusted, median line marked to centre the teeth. 11 bed themselves freely. It is hardly necessary to be more explicit upon this point, as every operator is fully sensible of the necessity of accuracy, the objects and means being the same in all cases alike. Cut 10. In fitting the teeth to the plate, they require in a large majority of cases, only lateral grinding, which must be accurate ; the metal in flowing, forming their beds or base, so that they need not be touched at these points, except when the prominences of ridge make them too long, when they may be readily cut down, preserving only the outer or gum surface perfect. When blocks are used for this process, they require the joints to be well fitted on both sides of the gum, as represented, to prevent the metal flowing into these joints, and exposing this carelessness. There is no fear of chipping or spawling of the teeth, nor of their altering their positions so much to be dreaded in sol- dering ; precisely as they are placed and worked, so will they result. As each tooth is ground sufficiently to accommodate its neighbor, it should be held in its position by a small quantity of melted wax, run under its base, from the point of the knife or shaping tool, Cut 10. Wax rims removed and teeth ground and modeled, ready to try in the mouth, when they are taken from these models and placed upon the cast for upper matrix. 12 Cdt. 11. care being observed not to use too much, so as to form a lump ; hold the tooth firmly with as little wax as possible ; after all are ground and fitted, take a narrow strip of plate wax and pass around the inside of the teeth, its width being indicated by the length Cut 12. of crowns from the plate ; then with the small leather dub or small brush, press the wax carefully in be- tween the neck of the teeth, cutting off all superfluous wax and finishing up as smoothly as possible ; a nar- row strip is now carried around the outside, placed Cut 12, exhibits the teeth ground or fitted to the plate and rims of wax placed around them, smoothed with the brushes or instruments, and polished with the blow-pipe ; A, cast showing the plate of teeth fitted closely down upon it, and the small holes by which the articulating plaster cast is held in its proper place; B, chamber; D, wax plate; F, the strips of wax added, and fitted smoothly around the teeth. This represents the piece ready to receive the tin rim to make the upper flask. 13 on the groove in the gum, (if gum teeth are used,) made for this purpose, and resting on the wax plate ; a Uttle melted wax holds this strip all round, and the warm knife smooths it partially down; when plain teeth are used, the strip should run up upon the crowns, and be gently pressed in between the teeth ; the wax thus left upon the teeth should be cut in small circles from off their surfaces, leaving little points of wax in between the teeth, this enables the operator to model it around them in a beautiful manner ; when the wax is made as smooth as possible in and around the teeth, a small blow-pipe and spirit lamp are used, and by short, gentle puffs, the wax is made to flow, presenting a beautifully polished surface. Upon this depends all the labor of finishing ; for, after a little practice, when properly done, it is a work of no moment. Cut 13. At this stage it is best to try the teeth in the mouth, as any oversight or omission can be certainly and safely corrected without any danger to the piece, giving the greatest advantage of the process, and one Cut 13. A is the cast; D, wax plate, and teeth mounted ; F, colored strip of wax modeled around the teeth. 14 Cut 14. that is iiivaluable to the artist in this business. When satisfied upon all points, it should be taken from the mouth and placed at once upon the cast ; the plate care- fully pressed down at every point with the brushes ; Cut No. 14. The close adapta- tion of the wax plate is ab- solutely necessary for expe- dition of finish, and can be done perfectly, with the greatest ease, by these little implements. If it is done well, the plate needs no sup- port ; if not so done, it must be supported in its position by tying a thread over the molars and around the cast. The tin rim, by which the cast was made, is now placed around. Cut 15, projecting some distance above the teeth, the surface of the cast inside the rim and out- side of the wax plate should be freely oiled or painted with the strong soap water, to make it part freely, aud the upper flask or matrix poured little by little carefully in, of the same composition as the other, Cut 14 are brushes which can be used with much advantage; the largest is very soft hair, used for pressing down the wax plate upon the cast before making upper matrix, and will not deface the polish of the wax plate. The smaller ones are intended to smooth the wax between the teeth and at such other points as the knife or instruments cannot be used without defacing the Wax. I 15 covering the teeth to the depth of | inch, excluding all air-bubbles and securing the absolute filling of the spaces around and between the teeth, by the aid of the camel's-hair pencil or feather, with which it should be kept stirred until it begins to set. When hard, remove the rim and tap the part first made gently until the two parts loosen, when they may be separated. Cut 16. The gate should always be cut from the part containing the teeth and plate, and done when removed, before wax plate is taken out, to prevent small pieces falling in, &c. The wax plate and as much of the wax as possible, used in building around the teeth, should now be removed, for although the Cut 15 shows the plate ready for upper matrix, with the tin rim, fig. 1, fig. 5 being the point of separation. The plate has been pressed closely down upon cast; A, composition cast ; B, chamber ; D,wax plate; F, the added strip of colored wax used to build around the teeth. 16 Cut 16. flask will absorb it, yet the melted and absorbed wax softens and weakens the (composition, inducing a rough and strained condition of plate in pouring, for the metal shouhl always l>e poured fast and freely into the mould, vents cut as re})resentcd at the highest point, or last run. To obtain a smooth surface, and to aid the metal in flowing, it is well to hold the surfaces over a gas-light or candle flame, until tliey are covered with the carbonaceous matter from the smoke ; a slight coat is suflicient. After all the wax is removed, gate and vents cut, the two parts of the mould should be jdaced together and (irmly bound with iron wire, passing around at least twice and then twisted down tight ; then carefully lute the surface of joint with the ])l;ister and spar from one vent to the other, as well as tiie under surface of impression cast to assist it in retaining its strength. The piece is now placed in a bake oven of a stove or range, or any vessel in Cut 10 iH tlie iiintrix niado over pinto and teeth with one-half removed of the wax, HhowiiifT the position of tlie teeth. A, cast or matrix ; U, gate cut for nie- tnl to bo poured in, with vent on either side ; C, remaining half of plate ; H, chamber. I 17 which a good bread baking heat can be obtained/'^ and exposed to this heat for at least three liouns oi- longer, if possible, to be made thoroughly dry. The motal should be melted and made hot, until of a light l)hit3 color ; the cast hotter than can be held or lifted with the hand, should be placed in an upriglit posi- tion, the metal poured rapidly in, and should never bubble, as this is certiiin evidence of moisture, but should remain ^lotionless. The vents should be filled from the flow, and in this event, the piece will always prove perfect. Indeed, with suitable preen u- tion, failure will never occur ; the great necessity Ijcing to have your flasks pcrfcdh/ dry iind the Qiu/a./ hot. When cold, the part (containing the teetli should be cut oiTfrom around them, and thus easily icnioved, exposing the plate upon the cast, at which time any rc[)airs can be made by the use of the solders Nos. 1 and 2, but with care this can never occur ; when it happens, it is expeditiously repaired by the use of muriate of zincas a flux.f Carved Blocks for this process secures a beautifid piece of work, attended oidy by one of the usual ob- jections to this kind of teeth, that is, when they are broken by accident or otherwise, a new block must * Tlie lioat should be as unifoiiii a8 possible, and may ranj^o belw\, but never allowed to come in contact with a red hot Huiface or (lame, in an unwise ellort to expedite the drying. This would, drive oil' tlio water of crystallization and induce cracks, warpage or too great softnesH, and produce leakage of hot metal when poured. Should this ever happen, the point of leakage must bo again lutod and poured as soon as possible again ; with caro it never occurs. i-This is made by dissolving pure zinc in muriatic acid until it can take up no more of the metal. This llux improves by ago, and should not bo used, if possible to avoid, before throe months. 18 be carved, which fails in almost every instance to prove a fac simile of the former piece ; blocks momited in this way, however, can only break by unwarrantable use of them, as the permanent support given to every portion of their base produces a strength* in them not attained by any other method. Having had many workmen calling themselves superior artists, numerous sets of block teeth accumulated, formerly useless, or serviceable only as specimens of different styles of teeth, indeed made so that no former process could mount them, but by this new method they have all been mounted in practical cases, and are now being worn in the mouth. They were mostly made in one solid block, and certainly presented the most beautiful appearance, the only ob- jection being, that if accident should break them, they could not well be replaced. But the blocks now moulded are preferable substitutes for many reasons, their great beauty, strength, cheapness, expedition of mounting, and the fact of obtaining at any time a perfect fac simile of such as may be broken, will justly entitle them to universal favor. Partial /Sets and Single Teeth are mounted with still greater success and comparatively a much less propor- tionate time than whole sets, and in such- cases as would present insurmountable obstacles to swaged plates, such as a single tooth or a partial set for low- er jaw ; indeed, to the expert in this process, it mat- ters not how the case presents itself, his success will be greater than ever experienced before. The articulation of one or more teeth should be done in the mouth, after grinding and fitting the tooth or teeth 19 to the cast and the piece stiffened as described ; when adjusted to the cast, the plaster teeth on the cast should be carefully cut off and surface made smooth, so as to allow an easy separation of the two parts. The other manipulations are the same as described for full sets.. As gilding is not recommended, the attachments of clasps need not be described as they could not be used without, nor will the subject of gilding be treated of Repairing. — Cut out the broken part and file away the metal freely, fit in a tooth and build around it wax, as you desire the metal to be ; make a gate by rolling a piece of wax, round or oval shaped, and taper- ing from \ in. to fe, fix the small end to the largest surface of wax which has been built around the tooth ; from the opposite highest point, make a vent of wax ■§■ in., and have it so placed as to stand upon a level with the gate ; place a tin rim around the plate and fill in with composition carefully as before : when hard, remove as much of the wax forming the gate and vent as possible, and place the piece to dry with a less heat than will melt the metal ; when thor- oughly dry pour the metal in and allow it to cool, and it is ready for dressing. All alterations are most expeditiously done, and in such a reliable man- ner as to leave no trace behind of such changes, by simply adding wax to the plate as the desired alter- ations require, involve the whole in composition after forming a gate and vent as described, drying and pouring. With this simple process any desired repair or alteration can be made with beauty and 20 certainty. It is very important that the operator should keep in mind that he is modeUng an exact representation of the piece he is making for the mouth, and that the shghtest imperfection will be faithfully copied, as the metal is capable of giving the very finest possible line, and that it is possible for him to execute the whole of his work in this model state, so that when the piece is cast he has only to dress it up with sandpaper and burnisher. Everything will depend upon the entire absence of moisture, and the proper heat of the metal, repre- sented by its turning a light blue color. After the piece is cool, the gate and vent should be cut off with spring saw and dressed down with scrapers, emery paper or any instruments the operator may prefer, and finally polished or burnished as other pieces ; emery, fine pumice stone or spar used with water and finally dry, answers best.* A great advantage will be found in resetting old icorh upon a base of this metal, particularly plates for the lower jaw, which, from the absorption of the alveolus, cease to be worn with comfort, or where fruitless attempts have followed the insertion of blocks or continuous gum, or even single gum or plain teeth upon other metals. Take the impression of the jaw, and proceed as described in obtaining the articulation, after which, prepare the rejected piece by cutting off the plate as close to the lower part of the backings of the block or single teeth as possible, allowing them to remain united and retaining their * Some use a metal flask in order to prevent accidents, &c., but with care it never becomes a necessity, nor is the use of such to be commended. 21 positions with each other, then place them firmly upon the wax plate and cover the backings with wax so as to envelop all the old metal, place a very nar- row strip of wax around the outside, then smooth all down with the knife and blow pipe, of course having articulated them correctly. With continuous GUM set, cut all the platina off and place upon the wax plate, (according to the requirements of the bite taken,) mould a delicate strip all around the edge of the gum so as to sUgldhj imbed the set, proceed as mentioned for upper flask — drying, pouring, &c. This process will consume, to an expert workman, an incredible short time, and secure a useful set of teeth in all cases, besides yielding him in the ex- change of metals alone, a handsome profit. Solder, No. 1. — In j)i'eparing it for use, should be melted, and whilst hot pressed flat between two smooth surfaces. The desired thickness regulated by the ex- pedition used. No. 2 — Is rolled as any other solder. This latter one is available for many purposes, such as uniting any other two metals, holding them with great strength. Soldering is most readily done by either of the solders prepared for this work. No. 1 is a very brit- tle metal, and not as pure as that constituting the plate, but flows at a temperature less than one-half of its melting point, that is about 180° F. It should be used as sparingly as possible, by fitting in pieces of the plate metal in all places to be repaired, so that a small amount of solder may be used simply to unite the two parts. Pieces generally can be held in the hand whilst using No. 1, and the place to be repaired should 22 be gradually heated to melting of the solder by the small blow-pipe used in polishing the surface of wax plates, and used very much in the same manner, that is, by gentle puffs, until it flows suitably, which it will do in all cases. No. 2 is a very elastic and strong solder, but requires a much higher heat to fuse it and much greater care to prevent melting the plate, as its flowing occurs a few degrees below the melt- ing point. of the plate, still the expert will find no difficulty in its use. Teeth should never be soldered in repairing, but always poured, from the fact that in soldering, the metal can never be made to hold to the tooth or to the metal pins, but requires the pressure of a body of melted metal to force it in and around the points of attachment of the tooth. This must not be lost sight of, for a tooth which has been repaired by sol- dering is always a doubtful fixture, owing to the great inclination of the metal when liquid to run to metal, thus drawing away from the tooth, whilst a repair which has been made by pouring can always be reliable. BJoio-pipe. — This should be very small, so that it is by considerable pressure that the air should be made to pass through it, otherwise you endanger your wax plate in polishing, as well as your metal plate in sol- dering, by throwing too much heat in places, or cov- ering too large a surface, or by the heated air striking points where it is not wanted. Gating. — Always secure a good size gate in length and thickness. If the plate to be poured is very thin, see that the gate extends into the plate some distance, 23 by cutting out from its surface a small plate groove, extending, say half way over the chamber, which will give an increased thickness of the plate at this point, which can be easily cut away after pouring. Venting should be well secured by presenting a free opening upon both sides of the gate, so that air and gas may pass out without obstruction. Polishing Wax Plate. — This should be done with great care so that the wax shall not run over the teeth, or in any spot where the metal is not required, as it is sometimes tedious and even difficult to cut it away from between the teeth or their joints. If the blow-pipe used has a very small aperture and the heat thrown on gradually, until the surface becomes smooth, little trouble will be experienced. EXPLANATION OF PLATE, Fig. 1. Sectional view of nest of 4 rings, — 3, 3J4, 33^, 3% inches in diameter, and 2 inches deep. A flange is formed where the rings open, and is held together by a tin clamp, 6 ; the position of the impression is shown at a. Figs. II, III. — Sectional views of upper and lower jaw: b, gate for receiving metal, with branches, e e, for lower cast: c c, vents for escape of air : made always at the point which will be highest, when the matrix is in position for pouring : d d, notches cut before pouring the second half of matrix, to keep the two halves in right position. Fig. IV. Vertical section of matrix through (<,) central incisor: p, space for plate: 6, gate : I, luting. Fig. V. Completed, view of the same, ready for the oven, bound with wire, w le w, and luted, 112 2, from one air vent, c, round the entire matrix, over the line of junction, to the other air vent, c ; the joint is beveled oft" to receive part of the luting, which also passes out- side of the binding wires. Fig. VI. Moulding tool — 1, front view; 2, side view ; 3, section across centre. One end, a, pointed, to work between the teeth, the other shaped as 6 or c, both points curved, as shown in side view. Instrument 6 inches long, made of untempered steel, the centre faced with wood. Fig. VII. Oven to dry moulds. A circular tin, o, 6 inches in diameter, 7 inches deep, sup- ported on three feet, e e, 2 inches, high ; d, movable cover, with central opening : b, per- forated sheet iron shelf, 4 inches from top of oven, with smaller circle of sheet iron, (not perforated,) suspended 1 inch below, to break the direct heat of spirit lamp. In bottom of oven is an opening 2 inches in diameter, to receive spout, m, of lamp, I : or where gas is used, one of Shaw's heaters. Fig. VIII. Sectional views, showing the attachment of the plate to the teeth. 1, block section, showing ofl'set on the inside and outside of the base, and hole running into, but not necessarily through the block. The block carver should avoid making these holes parallel. 2, gum tooth with ofiset at top of gum, hole through the tooth (where the tooth is of suffi- cient size to admit it, ) and notches across the back. 3, plain tooth, dovetailed at the base and notches across back, aad if large enough, with hole partially or entirely through the axis. 4, a, top, and b, side view of a clasp, showing the dovetail, by which it is fastened into the plate; the melted metal should flow on both sides of this tongue, the retention being a me- chanical one, as in the case of the teeth, and not a soldered union. Fig. IX. 1, vertical section of pivot tooth. 2, cross section, showing the notches ground in the sides of the tooth. Fig. X. 1, vertical section of the ordinary plate tooth, with very narrow platina strip, sol- dered (with silver solder,) to pins ; 2, back view; 3, cross section of same. In cases requiring shoulder teeth, the shoulder is very readily formed of metal in either the pivot or the plate tooth. Fig. XI. Scrapers for dressing plates after casting. 1, convex and cuts towards the hand, 2, concave and cuts /row the hand. 3, end view of 1 and 2. The oval shape of these ihstru- ments gives the advantage of several degrees of curvature in the same instrument. They are both very easily sharpened. Fig. XII. 1, cross section of six front gum teeth, designed to show the dovetail form of the metal between the teeth, connecting with the continuous backing. If the teeth touch back and front, as at a, the metal between forms a pin, and has less strength than the dovetail. 2, cross section of a block in which dovetail grooves in the base are made instead of holes run- ning into the block. Either method of attachment, combined with the offset inside and out, is secure. Los Angeles This book is DUE on the last date stamped below. ll» Ytmrk "■ymm h'i'M I ^h% m ipy-U *{. WJ -IS b Vii ?,■ 41