key: cord-0945344-fbqqf00i
authors: Guo, Yongwen; Jing, Yan; Wang, Yunshi; To, Aileen; Du, Shufang; Wang, Liuzheng; Bai, Ding
title: Controls of SARS-CoV-2 transmission in orthodontic practice
date: 2020-06-05
journal: Am J Orthod Dentofacial Orthop
DOI: 10.1016/j.ajodo.2020.05.006
sha: 8136adecd91e14cc148a3efcc9bed1af0934044c
doc_id: 945344
cord_uid: fbqqf00i

ABSTRACT The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has attracted worldwide concerns because of its high person-to-person infectivity and lethality, and it was labeled as a pandemic as the rapid increase of confirmed cases in most areas around the world became evident. The SARS-CoV-2 is mainly transmitted through respiratory droplets and close contact. There are also evidences of transmission through aerosols and digestive tracts. Since orthodontic treatment involves large population who need routine return-visits, it was significantly affected and suspended because of the COVID-19 pandemic and the shutdown of the dental clinics and hospitals. Although the spread of COVID-19 has been effectively controlled in China and many areas have gradually resumed work and classes, orthodontic participants are still under high risks of SARS-CoV-2 infection. This is due to the asymptomatic carriers of SARS-CoV-2 or patients in the incubation period may cause the cross infection between orthodontic practitioners and patients. The close proximity between the practitioners and the patients, and the generation of droplets and aerosols that contain saliva and blood during treatment further increase the risks of transmission. In this review, we summarized the preventive strategies for controls of SARS-CoV-2 transmission to protect both staffs and patients during the orthodontic practice.

Since its emergence in December 2019, the coronavirus disease 2019 has spread rapidly and is now a global pandemic. The pathogen causing COVID-19 was initially named 2019-novel coronavirus (2019-nCoV), and then officially named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A public health emergency of international concern over this disease has been announced by the World Health Organization (WHO) since 30th January 2020 1 . Due to the particularity of the dental treatment procedures, the risk of SARS-CoV-2 transmission between dental practitioners and patients could be high 2 . Thus, all the routine dental practices were suspended after the outbreak of COVID-19 in many areas around the world, and only emergency services were provided. 3 As the COVID-19 has been effectively controlled in China and some other areas, dental clinics and hospitals are gradually resuming regular services. However, the prevention and the control of SARS-CoV-2 transmission during dental practice are still serious and challenging. The most critical reason is that that asymptomatic patients and patients in their incubation period are also carriers of SARS-CoV-2 and have the ability to be infectious. 4 It is difficult to identify and quarantine these patients in time, which can result in the SARS-CoV-2 transmission in the population. What's more, the close contact between dental staffs and patients as well as the droplets and aerosols generated during treatment containing saliva and blood further increase the risk of SARS-CoV-2 transmission in dental practice 5 . In addition, due to the previous suspension, many orthodontists are currently under heavy workload to reschedule the accumulated return-visit patients whose treatments were significantly affected and postponed. A study from Jordan found that although most Jordanian dentists were aware of COVID-19 symptoms, mode of transmission, infection control and measures in dental clinic, they had limited knowledge of the extra precautionary measures that are essential to protect the dental staffs and other patients from SARS-CoV-2 infection. 6 Thus, the standard control measures in our previous daily orthodontic work may not be enough to prevent the transmission of SARS-CoV-2 and protect both practitioners and patients from the COVID-19.

Effective control protocols during orthodontic practice are urgently needed. 7

The most common manifestations of the COVID-19 infected patients are fever and dry cough. Some have fatigue, diarrhea and other digestive tract symptoms. Severe patients can rapidly progress to acute respiratory distress syndrome, septic shock, metabolic acidosis, coagulation dysfunction and multiple organ failure. 8 Most patients who underwent chest computed tomography (CT) showed bilateral pneumonia with ground-glass opacity and bilateral patchy shadows. 9 However, some patients who are SARS-CoV-2 carriers could be asymptomatic. 4 Patients in the incubation period could also do not show the above typical symptoms. The incubation period of COVID-19 has been estimated at 3 to 14 days with an average of 5 to 6 days, 10,11 but there is also evidence that it could be as long as 24 days. 12 Studies have reported that majority of patients (50-80%) were considered asymptomatic at the early phase of infection but released large amounts of SARS-CoV-2, which were infectious and posed enormous challenges for controlling the spread of COVID-19. 13, 14 

The SARS-CoV-2 has been found the evidence of rapid person-to-person transmission and susceptible to different age groups in clinical epidemiology studies. 11 The virus is mainly transmitted by respiratory droplets form talking, coughing or sneezing, and direct or indirect contact with nasal, oral, and eye mucous. 15 It has been reported that SARS-CoV-2 was widely distributed on floors, computer mice, trash cans, sickbed handrails, and in air 4 meters away from patients in hospital wards. 16 Another study also found that SARS-CoV-2 could remain viable and infectious on different types of environmental surfaces for a few hours or up to several days. 17 The contact with these contaminated surfaces would largely increase the risk of transmission. More importantly, studies have indicated that aerosol transmission of SARS-CoV-2 is plausible, since the virus in aerosols can stay viable and infectious for about 3 hours. [17] [18] [19] In addition, a growing number of clinical evidence reminds us that digestive system may also serve as an alternative route of infection as SARS-CoV-2 could be detected from the stool specimen of the confirmed patient. 20,21 SARS-CoV-2 could also be detected in the self-collected saliva of most infected patients even not in nasopharyngeal aspirate, suggesting the possibility of salivary gland infection and possible transmission. 22, 23 Another study also suggested that ACE2 (angiotensin-converting enzyme II)-expressing cells in oral mucosa, especially in epithelial cells of tongue, might provide possible routes of entry for the SARS-CoV-2, which indicates that the oral cavity is a potentially high risk route for SARS-CoV-2 infectious susceptibility. 24

During the orthodontic practice, the patients' mouth and nose are in close proximity with orthodontists and assisting staffs for long periods. The communication, coughing, or sneezing during the practice can easily bring out the respiratory droplets. Direct contact with saliva or blood of the infected patients during orthodontic procedures within the mouth include photographing, impression taking, oral scanning, bracket and attachment bonding or removal, archwire changing, anchorage screw implantation, and so on. Indirect contact with contaminated dental settings and environmental surfaces will also increase risk for the virus transmission.

The use of orthodontic tools and materials, including pliers, power chains, and adhesives which are usually not individually packaged or disposable, will increase the risk of cross infection. Also, the use of high-speed handpieces and high-pressure 3-way syringes during bracket or attachment bonding and removal will generate a large number of saliva or blood-mixed droplets and aerosols which could remain suspended in the air for long periods before they settle on environmental surfaces or enter the respiratory tract. 5, 25 In addition, fecaloral routes may also be a potential transmission route during orthodontic procedures, especially the self-operation by patients, such as the placement and removal of the clear aligners, elastics and other removable appliances. Thus, the major transmission routes of SARS-CoV-2 in orthodontic practice are respiratory droplets, direct or indirect contact, saliva or blood-mixed aerosols and the digestive tract. Effective control strategies to prevent the transmission of SARS-CoV-2 through these routes are needed. 7

Although vaccines are the most effective strategy for preventing infectious disease, research groups around the world are accelerating the development of COVID-19 vaccines using various approaches, but there are still no vaccines available for COVID-19 currently. 26, 27 Therefore, it is critical to take infection prevention and 

Strengthen the organization and management of the clinic or hospital, make systematic plans and procedures for the prevention and control of COVID-19, and carry out training to all staffs including cleaners and security personnel to make sure everyone is aware.

Pay close attention to the changes of the pandemic situation and adjust the control strategies according to the management requirements of the national and local health administrative institutions.

Strictly perform the procedures of patient evaluation and pre-examination and triage before orthodontic practice to achieve early detection, early reporting and early isolation for COVID-19 suspected or infected patients.

Manage only orthodontic emergencies in areas where COVID-19 spreads, non-emergency orthodontic practices should be postponed. 32, 33 After the effective control of COVID-19 in the area, first-visit or return-visit patients should be carefully scheduled and avoid the aggregation of patients and their companies.

Reinforce the hand hygiene, use personal protective equipment, and take disinfection measures for dental settings, tools and medical wastes to avoid iatrogenic infection.

Reduce the use of high-speed dental handpieces and high-pressure 3-way syringes during the practice, while increasing the use of saliva ejectors with high volume to minimize the environment pollution by droplets and aerosols.

Before entering the dental clinics or hospitals, each patient should be evaluated at the entrance whether they are suspected cases of COVID-19. To date, the National Health Commission of the People's Republic of China has released the 7th edition of the Guideline for the Diagnosis and Treatment of COVID-19. According to the guideline, first, the temperature of each patient should be taken using contact-free forehead thermometers. Then, a questionnaire should be used to screen the suspected patients take different actions according to the triage of the patients as shown in the flow chart of Figure 1 . Notably, staffs responsible for temperature measurements and questionnaire should take protective measures as recommended in Table 1 .

What's more, a safety distance of at least 6 feet or 2 meters between people should be maintained while completing the questionnaire or in the waiting area in case that they spray droplets from their nose or mouth which may contain virus when someone coughs, sneezes, or speaks. 34, 35 In addition, patients are also suggested to wear face masks during the pre-examination and triage procedures as well as the waiting for treatment. 34

Strict hand hygiene is a simple and effective way to cut off the spread of the virus. To reinforce the compliance of hand washing, a two-before and three-after hand hygiene guideline is proposed. Specifically, the two-before is to wash hands before patient examination and before treatment procedures, the three-after is to wash hands after touching the patient, after touching the surroundings and equipment without disinfection and after touching the oral mucosa, blood, body fluid, and so on. Also, orthodontic staffs should avoid touching their own eyes, mouth and nose. 7 Hand hygiene should be also applied before eating as well as before and after using the bathroom to avoid the fecal-oral transmission. 21

Since droplets, contact, and aerosols are the major transmission routes of SARS-CoV-2 during orthodontic practice, barrier-protection equipment is strongly recommended for all orthodontic staffs. The protective measures include wearing disposable working cap, disposable surgical mask, working clothes, protective goggles or face shield, disposable latex gloves or nitrile gloves, and disposable isolation clothing as well as waterproof boot covers. The protective levels and equipment for different applications are recommended in Table 1 . Notably, the orthodontist and the assistant working in close proximity to the patient are recommended the highest level of protection to wear the hooded medical isolation clothing that cover the body as much as possible, especially during the use of high-speed handpieces and high-pressure 3-way syringes. In addition, it is recommended to wear two layers of latex or nitrile gloves during long practice procedures. It is critical to pay special attention to the operation of the tools, especially sharp instruments. In case of inadvertent laceration, it would increase the risk of infection as the virus can enter the punctured skin directly and cause the infection.

To avoid indirect contact with contaminated protective equipment, the order of wear and removal is critical 

During the epidemic period of the COVID-19, it is recommended to manage only orthodontic emergencies to prevent further harm, such as brackets debonding, archwire/ligature wire deformation or shifting, oral mucosa irritations, and anchorage implants loosening. [37] [38] [39] Nevertheless, orthodontists or assistants should evaluate the emergencies before allowing the patients to come to the office by requesting photos or videos from the patients. If the emergency could be managed at home by remote instructions to the patients over the phone or other communication tools, such as WeChat and WhatApps, it is unnecessary for them to come to the office. 33 First-visit and non-emergency return-visit patients are suggested to schedule after the COVID-19 epidemic is effectively controlled in the area. The recommendations to prevent the transmission of SARS-CoV-2 during the main orthodontic procedures were summarized as below.

Preprocedural mouthrinse with antimicrobial agents is beneficial to reduce the salivary load of oral microbes.

The commonly used chlorhexidine for mouthrinse has not been proven to be effective to disinfect SARS-CoV-2. However, 0.5%-1% povidone iodine solution is recommended as it has been reported to be able to disinfect SARS-CoV-1 and SARS-CoV-2. 40, 41 Since SARS-CoV-2 is vulnerable to oxidation, mouthrinse containing oxidative agents such as 1% hydrogen peroxide is also recommended 7,41 . The patients should be instructed to swish the mouth rinse for 2-3min and spit gently into a disposable cup. Saliva ejectors with low or high volume should be used to eject the gargle immediately to reduce the generation of droplets.

Photographic records of the facial and dental images could be taken in a separated unit. For patients with high throat sensitivity, the reflector should not be placed too deep in the mouth which may otherwise cause irritation, nausea, and vomiting leading to the generation of droplets. 42 Photographers should strictly implement the principle of "one patient one use and one disinfection" for auxiliary equipment such as retractors and reflectors.

Although the intraoral X-ray examination is the most commonly used radiographic technique in dental practice; however, it can stimulate saliva secretion, gagging and coughing. 42 The direct contact to the saliva during examination would also increase the risk of infection transmission. Therefore, extraoral radiographies, such as panoramic radiography and cone beam computed tomography (CBCT) are more appropriate alternatives during the epidemic period of COVID-19. 2

Before taking the dental impression, patients should be informed of potential risks of nausea and gagging in advance. Patients should also be instructed to inhale through the nose and exhale out the mouth. When taking the impression, the patient should wear a waterproof towel on the chest and hold a disposable cup in case of saliva splashing or nausea and vomiting caused by throat irritation from the alginate or silicone rubber materials. It is important to avoid contamination of the devices used in mixing the alginate material by putting it on a tray. After solidification and taking out of the impression, wash the saliva or blood on the surface gently with slow running water to prevent splashing and then disinfect the impressions. Alginate and silicone rubber impressions should be disinfected by immersing in 1000mg/L chlorine containing disinfectants for 15-30 min before they are casted or sent to the factories. 43, 44 

Patients who need clear aligner orthodontic treatment and other customized appliances can obtain digital dental models through oral scanning. This may also help to reduce cross infection possibilities when compared to traditional methods of alginate or silicone rubber impressions during the storage and delivery.

During the scanning, the staff should avoid inducing the pharyngeal reflex of the patient by gentle operation when scanning the molar regions. In order to avoid aerosol in the air caused by using 3-way syringe to dry the tooth surfaces during the scanning, cotton rolls could be alternatively used to wipe the patient's tooth surfaces and keep the mouth dry by using saliva ejectors. Use the touch pad of the scanning bar to control and avoid the use of the touch screen which may not be effectively disinfected due to its special screen characteristics.

After scanning, the handle of the scanner should be sprayed and wiped with 75% alcohol. The intraoral head of the scanner should be "one patient, one use and one disinfection".

For the first-visit patients, after the initial examinations and records have been taken, it is recommended to make the next appointment for return-visit on a separate day to communicate with the patients about treatment alternatives. The purpose of this is to reduce the staying time that patients are in the clinic or hospital and to avoid the potential risk of cross infection caused by the aggregation of patients.

During the treatment of the return-visit patients, especially the first-time bonding or the final removal of the appliances, the orthodontist and the assistant will be working in close proximity to the patient for an extended period. During bonding or removal of the brackets, trimming of the attachments, interproximal reduction, and so on, the staff should reduce the use of high-speed handpieces and high-pressure 3-way syringes. Low-speed handpieces or the manual devices are alternatives that can be used to reduce the formation of droplets and aerosols. If high-speed handpieces are necessary to use, anti-retraction handpiece with specially designed anti-retractive valves or other anti-reflux designs are recommended. These alternative designs have a greater reduction in the backflow of oral microbes into the waterlines of the handpiece and dental unit as compared with the handpiece without anti-retraction function. 45 Nevertheless, the use of high-speed handpieces and high-pressure 3-way syringes in the patient's mouth could easily splash the saliva or blood to form aerosols.

Therefore, in addition to the Level III personal protective measures (Table 1) , the use of high-volume saliva ejectors and the four-handed or six-handed cooperation technique should be adopted to prevent cross infection as well as to improve working efficiency. What's more, a plasma air sterilizer should be turned on continuously for air disinfection, especially during the procedures related to the use of high-speed handpieces and high-pressure 3-way syringes, and the windows of the room should be open to allow natural ventilation.

The principle of "one room one patient one disinfection" should also be followed.

Individually packaged archwires are recommended to use in the fixed orthodontic treatment to avoid cross infection. When the archwires need to be adjusted during the orthodontic treatment, such as the bending of three orders or the adding of the curve, spray and wipe the archwire with 75% alcohol after it is removed from the mouth. During bending, two layers of gloves are suggested to wear in case of glove tear or potential skin laceration from the archwires.

Removable appliances, including clear aligners, are directly in contact with the saliva and the oral mucosa making them potential transmission media of SARS-CoV-2. Appliances should be washed and sprayed with 75% alcohol or 1000mg/L chlorine containing disinfectants before the adjustment. Care should be taken to avoid pharyngeal reflex during wear and removal.

After the completion of one patient, disinfection of dental settings and related surfaces should be done before treatment of the next patient. The saliva ejector tubes should be flushed with at least 150ml 1000mg/L chlorine containing disinfectant. The spittoon area should also be flushed and cleaned with 1000mg/L chlorine containing disinfectant. The handpieces and 3-way syringes should be run to discharge water for 30 seconds which will help to flush out patient materials that may have entered the waterlines. The dental chair should be sprayed with 75% alcohol and completely wiped and disinfected with 1000mg/L chlorine containing disinfectant. After disinfection, the possible touching areas of the dental setting by the orthodontist and the assistant during the treatment should be covered with new antifouling membrane. An interval of 3-5 min is recommended between two consecutive patients to allow for optimal disinfection.

Many aspects of orthodontic treatment require the cooperation of patients, such as the wearing and removal of the clear aligners, retainers, functional appliances, rubber band elastics and so on. Orthodontic staffs should inform the patients to incorporate proper hand hygiene before and after self-operation as well as before and after meals and defecation. Instruct the patients to use the six-step hand washing method to avoid the transmission of virus by contact and potential fecal-oral routes. In addition, patients who wear removable appliances should be instructed to keep the appliances stored in containers after removal rather than out on open surfaces to prevent the possible transmission of SARS-CoV-2.

After the practice, the reusable orthodontic instruments, such as pliers, should be pretreated, cleaned, alcohol should also be used to spray and disinfect and then allowed to dry before preservation for future use.

The medical waste generated by the treatment of patients should be stored in the specially made medical waste bags then transported and disposed in accordance with the management requirements for medical waste.

Since airborne infection is one of the major concerns in orthodontic practice, the disinfection and purification of the air is of great importance to prevent the spread of the COVID-19 and other microbes. Plasma air sterilizers can be left continuously running for air disinfection in an environment with human activity, especially in the working area and the waiting area. In addition, the ultraviolet light should be turned on after treatment or lunch break for environmental surface disinfection for 30-60 min, twice a day. If the ultraviolet light is not available, spray and wipe the surfaces, such as floor, desk and chair, with 1000mg/L chlorine containing disinfectant every 2-3 hours. Also, the natural ventilation is a simple and effective way of air purification. Under air circulation, the microbial colonies can be significantly reduced by 77.3% -79.3% within the first 30 minutes, and up to 96.4%-99.5% within 75 minutes. 46

It is recommended to follow up with patients digitally through photos or video calls using the phone or other communication tools, such as WeChat and WhatApps, to not only monitor the orthodontic progress, but also to minimize the repeated patient contact and ensure patient safety in case of orthodontic emergencies. 33, 47 It was reported that during the COVID-19 epidemic period, 90% of the public dental hospitals in China provided dental consultations online, 3 which could also be helpful to relieve the patient anxiety caused by the suspension of the return-visit.

Although the COVID-19 is currently under effective control in China and many areas are gradually resuming normal activities, the increase in population mobility and the rising cases worldwide also pose great challenges for the prevention and control of COVID-19. Since there may still be asymptomatic patients or patients in the incubation period after resumption of regular activities and a large number of orthodontic patients from a wide spread distribution in need of orthodontic return-visits, all procedures related to the orthodontic practice should be strictly performed with preventive measures to control the potential transmission of SARS-CoV-2. The control strategies include, but not limit to, pre-examination and triage of patients, hand hygiene, personal protective measures, mouthrinse, reducing the use of high-speed handpieces while increasing the use of high volume saliva ejectors during bracket or attachment bonding and removal, disinfection during archwire changing/bending and removable appliance adjustment, disinfection of dental settings between patients, instructions to patients, management of reusable items and medical wastes, air and environment disinfection, and digital patient follow-up. We must constantly bear in mind that the threat of infection is not visible which poses a challenge on the orthodontic practice thus effective control measures should be taken to prevent the transmission of SARS-CoV-2 and protect both practitioners and patients from the COVID-19. 

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Recommended the strategies for controls of SARS-CoV-2 transmission in orthodontic practice

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