key: cord-0751178-gc1wwcpo authors: Jamal, Mohamed; Shah, Maanas; Almarzooqi, Sameeha Husain; Aber, Hend; Khawaja, Summayah; El Abed, Rashid; Alkhatib, Zuhair; Samaranayake, Lakshman Perera title: Overview of transnational recommendations for COVID‐19 transmission control in dental care settings date: 2020-06-03 journal: Oral Dis DOI: 10.1111/odi.13431 sha: bb236704c337301e7bed4aaf178da85c12629495 doc_id: 751178 cord_uid: gc1wwcpo On 11 March 2020, the World Health Organization (WHO) declared the coronavirus disease (COVID‐19) caused by severe acute respiratory syndrome coronavirus (SARS‐CoV‐2) as a pandemic. Until an effective treatment or a vaccine is developed, the current recommendations are to contain the disease, and control its transmission. It is now clear that the primary mode of SARS‐CoV‐2 transmission is aerosol/droplet spread, and by contacting virus‐contaminated surfaces acting as fomites (inanimate vectors). Furthermore, recent data indicate that the live virus particles are present in saliva, and, more alarmingly, asymptomatic individuals may transmit the infection. By virtue of the nature of the practice of dentistry where intrinsically, a high volume of aerosols is produced, as well as the close proximity of dentists and patients during treatment, dentists and allied health staff are considered the highest risk health professional group for acquiring SARS‐CoV‐2 during patient management. Therefore, several organizations and specialty associations have proposed guidelines and recommendations for limiting the transmission of SARS‐COV‐2 from carriers to dentists and vice versa. This paper aims to provide a review of these guidelines, and concludes with a brief look at how the practice of dentistry may be impacted by COVID‐19, in the post‐pandemic era. Bureau of Labour Statistics of the USA (Gamio, 2020) . This is likely to be due to the nature of their work that entails aerosol production, and working at very close proximity to their patients during dental treatment. Hence, a number of dental associations and societies have now promulgated several protocols to provide guidance on managing dental practices during the pandemic. This paper provides a brief overview of the etiopathology, transmission routes and symptomatology of the disease followed by a critical commentary of the various transmission control guidelines. COVID-19 is caused by SARS-CoV-2 which belongs to the family of Coronaviridae (Figures 1 and 2) . Coronaviruses can be divided into four genera: alpha, beta, gamma and delta coronaviruses. Alpha and beta genera mostly infect mammals, while the gamma and delta mostly infect birds. There are six different alpha and beta variants of coronaviruses that infect humans, four of them (alpha HCoV-229E and HCoV-NL63, and beta HCoV-HKU1 and HCoV-OC43) usually cause mild symptoms similar to the common cold, while two of the beta coronaviruses can cause severe respiratory illnesses that can be fatal, such as the severe acute respiratory syndrome coronavirus (SARS-CoV) and the Middle East respiratory syndrome coronavirus (MERS-CoV; Ashour, Elkhatib, Rahman, & Elshabrawy, 2020; Guo et al., 2020) . Indeed, recent genome sequencing and phylogenetic analyses of SARS-CoV-2 have shown its close resemblance to SARS-CoV (about 79%) and MERS-CoV (about 50%; Lu, Zhao, et al., 2020; Zhou et al., 2020) . Furthermore, Zhou et al. (2020) have demonstrated the high degree of similarity in receptor-binding domain (RBD) of SARS-CoV, and SARS-CoV-2 and both appear to target angiotensin-converting enzyme 2 (ACE2) of human cell walls. SARS-CoV-2 uses ACE2 as a portal of entry into host cells, thus, all cells expressing ACE2 are susceptible to infection (Hoffmann et al., 2020; Zhou et al., 2020) . Therefore, several authors suggest that knowing the expression pattern of ACE2 in different organs and tissues is critical to determine the routes of entry of SARS-CoV2, and also to understand the pathogenesis of COVID-19 disease (Hoffmann et al., 2020; Wan, Shang, Graham, Baric, & Li, 2020; Zhang, Penninger, Li, Zhong, & Slutsky, 2020) . There are several organs and tissues that express ACE2, such as the lung, heart, kidney, small and large intestine, arterial and venous endothelium, oral mucosa and salivary glands (Cano et al., 2019; Hamming et al., 2004; Liu et al., 2011; Xu et al., 2020; Zhang et al., 2020) . Interestingly, a recent study used bulk RNA sequencing data extracted from oral tissues and showed a high degree of expression of ACE2 in oral tissues, such as epithelial cells of the tongue and the oral mucosa . Another study by Lin and colleagues used single-cell sequencing data and found that ACE2 and FURIN (an enzyme that facilitates cellular entry of SARS-CoV-2) are expressed on the oral mucosa. They confirmed these results by performing immunostaining which showed high expression of these markers on the epithelial cells of tongue, lips buccal mucosa, palate and gingivae . These studies suggest that the oral cavity is a possible route of entry for SARS-CoV-2 . The clinical manifestations of COVID-19 range from early, prodromal asymptomatic cases to severe pneumonia with multiple organ failure. The most common symptoms are fever, cough, sore throat, fatigue, myalgia, headache, shortness of breath and in some cases diarrhoea. Chest computed tomographic (CT) scans might show patchy shadows and ground glass opacity in the lung (Epidemiology Working Group for NCIP Epidemic Response, Chinese Center for Disease Control, & Prevention, 2020; Guan et al., 2020; Wang, Hu, et al., 2020; Zhu et al., 2020 Guan et al., 2020; Wang, Hu, et al., 2020; Wu & McGoogan, 2020; Zhu et al., 2020) . This initial observation is now confirmed by data from multiple countries where the disease is prevalent. In terms of the oral manifestations of the disease, there appear to be very few recognized thus far. However, recent studies have shown that loss of taste (ageusia) or taste alteration (dysgeusia/ amblygeustia) is common in COVID-19. Recently, Chen et al. (2020) conducted a survey of COVID-19 patients, to evaluate the most common oral manifestations of the disease, and noted that more than half of their patients suffered from dysgeusia/amblygeustia. The aetiopathology of this condition may be related to the fact that the cells of the salivary gland and tongue are potential targets for SARS-CoV-2, due to expression of ACE2. The most commonly reported routes of SARS-CoV-2 transmission are inhalation of respiratory droplets or aerosols from the infected individuals that may occur within one metre radius of the index case, or through direct inoculation of virus-infested particles by touching surfaces contaminated with infested respiratory droplets (fomite transmission via an inanimate vector; Guan et al., 2020; Li et al., 2020; Liu et al., 2020; Yu, Zhu, Zhang, & Han, 2020) . For instance, it has been reported that SARS-CoV-2 can stay viable up to 24 hr on cardboard, and up to 72 hr on plastic or stainless steel surfaces (van Doremalen et al., 2020) . Opinions vary as to the degree and extent of the airborne mode of SARS-CoV-2 transmission. There is direct and indirect evidence to indicate that aerosols with a particle size of <5 µm can be entrained in air and carried over distances of up to 1 m (Samaranayake, 2018) . One recent study has reported the survival of SARS-CoV-2 up to 3 hr in aerosol particles, supporting the likelihood of airborne transmission (van Doremalen et al., 2020) . However, another study reported the absence of SARS-CoV-2 in air samples collected from an actual clinical environment where symptomatic patients were admitted (Ong et al., 2020) . Therefore, more studies are required to provide confirmatory evidence of airborne transmission of SARS-CoV-2 in both clinical as well as non-clinical settings (World Health Organization, 2020c). Nevertheless, in clinical settings, as in dental clinics, where a large volume of aerosol is produced, airborne infection transmission is likely, and hence dentists and allied dental staff need to consider extra airborne and droplet precautions during the pandemic (World Health Organization, 2020c). Furthermore, SARS-CoV-2 has been detected in saliva of infected individuals (To, Tsang, Leung, et al., 2020; To, Tsang, Yip, et al., 2020) . As explained earlier, this can be attributed to the expression of ACE2 in salivary glands (Cano et al., 2019; Hamming et al., 2004; Liu et al., 2011) . This is another significant factor that needs attention in dental practice, as aerosols generated during dental procedures are highly likely to be mixed with patients' virus-contaminated saliva . On the other hand, this provides an excellent opportunity to explore a non-invasive mode of sample collection for SARS-CoV-2, as an alternative to the commonly used nasopharyngeal swab (Sabino-Silva, Jardim, & Siqueira, 2020; To, Tsang, Leung, et al., 2020) . are also contaminated with SARS-CoV-2 (Xiao et al., 2020) . These Non-pneumonia and mild pneumonia 80.9% Severe Dyspnoea, respiratory frequency ≥ 30/min, blood oxygen saturation ≤ 93%, partial pressure of arterial oxygen to fraction of inspired oxygen ratio < 300, and/or lung infiltrates > 50% within 24-48 hr 13.8% Respiratory failure, septic shock, and/or multiple organ dysfunction or failure 4.7% findings, together with the fact that ACE2 is expressed in the gastrointestinal tract (Hamming et al., 2004) Guan et al., 2020) , tend to imply that faecal-oral transmission route of SARS-CoV-2 is plausible. As mentioned, there is a high likelihood of SARS-CoV-2 transmission in the dental care settings due to the dual risk of high aerosol generating procedures in dentistry, plus the saliva-borne SARS-CoV-2 in both symptomatic and asymptomatic individuals. Hence, several dental societies/associations have provided guidelines to control transmission of SARS-CoV-2 in dental practice. The response of dental associations to curb the clinic-associated nosocomial transmission of SARS-CoV-2 has been varied. Some associations have recommended complete close-down of dental practices (British Dental Association, 2020), whilst the others have suggested restricting dental treatment to only addressing emergencies and reducing the number of routine dental check-ups and follow-up appointments (American Dental Association, 2020b). These guidelines, summarized in Table 2 , and described in detail below, include postponing elective dental treatment, developing new screening protocols, disease assessment through telecommunication and special additional precautions particularly during aerosol generating dental procedures. Due to the alarming surge in the number of infected individuals, the American Dental Association (ADA) recommended (on 16 March 2020) to address only dental emergencies and to postpone all elective dental procedures (American Dental Association, 2020a). In addition, ADA and other dental societies have also published road maps for identifying dental emergencies in each of the dental specialties (American dental Association, 2020c; Scotish Dental Clinical Effectiveness Programme, 2020). A list of such common dental emergencies encountered that demands the patient to visit the dental clinic in the midst of the ongoing outbreak of COVID-19 is provided in Table 3 . Virtual/telecommunication technologies are currently available to aid dental professionals to perform initial screening of patients, and identify emergencies. Such technology, in addition to taking a dental history, photographs and videos, will assist the clinician to reach a preliminary diagnosis. In regard to dental emergencies, initial management can be commenced over tele-communication using However, if the patient says "yes" to any of the aforementioned questions, and requires emergency dental treatment, CDC has recommended immediate patient referral to a facility properly equipped to manage potentially exposed or confirmed COVID-19 patients (American Centers Of Disease Control & Prevention, 2020). This is critical as most of the dental practices are not designed or equipped to provide the necessary droplet transmission control environment, such as an isolation room with negative pressure, and high-efficiency particulate air (HEPA) filter systems (American Centers Of Disease Control & Prevention, 2020). As discussed, inhalation of virus-laden aerosols is a major mode of SARS-CoV-2 transmission (Bentley, Burkhart, & Crawford, 1994; Nejatidanesh, Khosravi, Goroohi, Badrian, & Savabi, 2013) . Additionally, transmission of the virus has also been attributed to infectious droplets contaminating the conjunctival epithelium of the eyes (Lu, Liu, & Jia, 2020) . Hence, PPE must be worn, to provide an effective and efficient barrier against the aerosol-generated TA B L E 3 List of commonly encountered dental emergencies that require urgent dental care Cracked, fractured, loose or displaced tooth fragments and restorations a,b Ill-fitting or loose dentures a,b Trauma from fractured or displaced orthodontic appliances a,b Dento-alveolar injuries a,b Avulsed, displaced or fractured teeth a,b hazards from the operative site. These include protective eyewear, a face mask and a shield, a disposable working cap, appropriate gloves, gowns and impermeable shoe covers (Lu, Zhao, et al., 2020) . If, for an unavoidable reason the dentist has to perform aerosol generating procedures, then a particulate respirator that is at least as protective as a National Institute for Occupational Safety and Piece 2 (EU FFP2), or equivalent has to be used (Kohn et al., 2003) together with high volume suction. As intraoral radiographs might induce gag reflex, increase saliva se- It has been reported that the use of pre-operative antimicrobial mouth rinse reduces the microbial count in the oral cavity and aerosols generated during dental procedures (Ather et al., 2020; Eggers, Koburger-Janssen, Eickmann, & Zorn, 2018; Kariwa, Fujii, & Takashima, 2004; Mani, Srikanthan, Selvaraj, Menaka, & Parangimalai Diwakar, 2020; Meng et al., 2020; Peng et al., 2020) . (Ather et al., 2020) . It is clear that the hydrogen peroxide and iodine are the most recommended mouth rinses in this context. Since the virus load in human saliva is relatively high, a preprocedural mouth rinse alone may not eliminate this hazard. Hence, additional measures, such as the use of a dental rubber dam, are necessary (Spagnuolo, De Vito, Rengo, & Tatullo, 2020) . For instance, it has been reported that rubber dam isolation can reduce airborne particles by up to 70%, within a 3-foot diameter of the operational field Samaranayake, Reid, & Evans, 1989) . Therefore, Samaranayake et al., 1989) . In conclusion, therefore, it is highly advisable to use dental rubber dam, high volume saliva ejectors and four-handed dental assistance in the immediate post-pandemic era to eliminate SARS-CoV-2 transmission risk posed by both symptomatic and asymptomatic patients. As noted, the practice of dentistry involves the use of rotary dental/surgical instruments, which create a high volume of aerosols that could contain mixture of water, saliva, blood, microorganisms and other debris. Such instrumentation includes triplex syringe (3:1 syringe), high-and low-speed handpieces, ultrasonic scalers, air abrasion devices and intra-oral sandblasters (American Centers Of Disease Control & Prevention, 2020). The NZDA along with other associations have advised to avoid using these equipments as much as possible, and stressed the use of hand instrumentation, as well as low-speed handpieces without water spray to obviate dental aerosols. If the use of aerosol generating equipment is unavoidable, then the use of high volume saliva ejectors is recommended in addition to the other precautions mentioned above (Ather et al., 2020; New Zealand Dental Association, 2020b) . Furthermore, the use of a handpiece with an anti-retraction valve or other anti-reflux design is recommended during the pandemic and post-pandemic period . The guidelines also emphasized on the use of disposable instruments whenever possible. It is unlikely that symptomatic and acute COVID-19 patients attend the dental clinic. However, if they do so due to a dental emergency, it is recommended to refer the patient to a facility equipped with airborne infection isolation rooms (AIIRs). This extra precaution is due to the potential of airborne transmission through aerosols. AIIRs are single-patient rooms at negative pressure relative to the surrounding areas, and with a minimum of six air changes per hour. These clinics should have integrated HEPA filters in the air-conditioning system to filter any contaminated air prior to recirculation (American Centers Of Disease Control & Prevention, 2020). Further, furniture and equipment in the room should be minimal and those essential for the operating procedure only should be present. Rooms should be always closed, and entry/exit should be minimized. Furthermore, in addition to previously discussed transmission control precautions, all dentists and allied staff should use N95 or higher-level respirators (Kohn et al., 2003; Peng et al., 2020) . American Dental Association, 2020b). There is little doubt that the practice of routine dentistry will be irrevocably affected by the COVID-19 pandemic, at least in the shorter term, until a successful antiviral agent or a vaccine is found for the causative agent. Although at this stage it is difficult to extrapolate the "new reality" of post-pandemic dentistry, as the disease is still evolving in a majority of affected countries, there are some projec- Coronavirus infection, a decade later, and thankfully, they never developed into pandemics, and the regional epidemics burnt out fairly swiftly (Samaranayake & Peiris, 2004 In terms of post-pandemic infection control in the dental clinic environment, it is imperative to maintain a very high degree of suspicion by all dental personnel whilst strictly adopting the standard infection control precautions. Fortunately, the latter appears to be the norm in most, if not all, dental practices, and hence additional precautions appear to be unnecessary for routine patients. All dental personnel must maintain vigilance for any individuals entering the clinical premises with symptoms of acute respiratory infections (e.g. cough, cold, sneezing etc). Further, it may be highly desirable to record the temperature of each patient immediately after entering the premises, and before the patient enters the patient waiting area. For instance, this could be performed by a trained receptionist using a non-contact thermometer gun. Additionally, the patient history questionnaire should include recent travel abroad, as the COVID-19 pandemic may be smouldering in some parts of the world for the foreseeable future. As diarrhoea is also a relatively common in COVID-19, a recent or current history of this symptom may also have to be included in the questionnaire (Wang, Fang, et al., 2020) The foregoing is a provisional and a rather brief account of the plausible, key features of post-pandemic patient management. Definitive recommendations and guidelines on this subject should be developed by local and regional health authorities and are beyond the remit of this article. Many researchers and scientists, the world over, are working on potential drugs, and vaccines to manage COVID-19. Repurposed drugs are being either experimentally used or planned for the management of the condition, and these include the anti-retroviral drugs lopinavir and ritonavir successfully used to manage HIV disease, anti-malarial drug hydroxychloroquine and the antibiotic azithromycin Rosa & Santos, 2020) . There is also a current Australian trial of the BCG (Bacille Calmette Guerin vaccine which contains attenuated Mycobacterium bovis bacilli) for the condition (Miller et al., 2020) . Other possible products in the pipe-line include massive screening of millions of compounds using in silico research for their ability to destroy the SARS-CoV-2. As these are all in the early experimental stages and human trials are still ongoing, conclusive data are yet unavailable. Although a promise of a quick cure for the disease using the above approaches appears to be waning, several vaccines are under various developmental stages in many countries and should be available within the next 18 months or so, after appropriate human trials. There are recent, promising reports of patients showing improvement when they are administered hyperimmune sera (containing antibodies to SARS-CoV2) from recovered COVID-19 patients (Cunningham, Goh, & Koh, 2020) . This implies that the vaccination for preventing COVID-19 is the most promising approach to obviate a recurrence of the pandemic. If this was the case, then mass vaccination for COVID-19 could be the future, a situation akin to the annual vaccination required to prevent seasonal influenza amongst susceptible population cohorts, including dental care workers. Predictably then, one could foresee, the COVID-19 vaccine to be the next new addition to the armamentarium of recommended vaccinations for all dental health careworkers. Since the announcement of COVID-19 as a pandemic and the reported transmission risk to dental professionals, several dental societies, the world over, have published guidelines for transmission control and management of dental emergencies during the current pandemic. In this review, we summarize and outline the common themes and principles that emerge from these recommendations. There is universal concurrence on directives such as postponing elective dental treatment, developing appropriate screening protocols through telecommunication, applying special additional, droplet precautions when treating patients with dental emergencies, and sequestrated treatment of infected or suspect patients in specially fitted suites with negative pressure. We also discuss the recommended equipment and settings for clinics that can receive confirmed COVID-19 patients. Finally, we briefly outline the practice of dentistry in the post-pandemic era, and potential developments in antiviral drugs and vaccines that may be used in future to manage COVID-19. It should, however, be noted that due to the highly fluid, dynamic and the evolving nature of the pandemic, and the unfolding natural history of the disease process, the foregoing recommendations are likely to change and all dental personnel should constantly keep abreast of the new developments and pronouncements on infection control in dentistry, issued by the local and regional health authorities. The authors declare that they have no conflict of interest. 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