The first SAR-CoV-2 infected case was reported in Wuhan, China in December 2019 [1]. The number of patients rapidly increased. SAR-CoV-2 infection causes a respiratory disease that can lead to pneumonia and death. This disease was later named COVID-19. The World Health Organization declared COVID-19 a pandemic in March 2020 [2]. The pandemic presented a challenge for public health, the economy, and society. In August 2021, four SAR-CoV-2 variants are of concern; Alpha (B.1.1.7), Beta (B.1.351.2, B.1.352.3), Delta (B.1.617.2, AY.1, AY.2, AY.3), and Gamma (P.1, P.1.1, P.1.2) [3]. The major routes of SAR-CoV-2 transmission are respiratory droplets and contact transmission [4]. Dental personnel are at risk because many dental treatment procedures generate aerosols and droplets that may be contaminated with the virus [4].

The first SARS-CoV-2 positive case in Thailand was reported in January 2020. The first local infection was a taxi driver who was potentially infected from Chinese tourists [5]. Since then until now (August 2021), three waves of the COVID-19 outbreak have been reported. According to the COVID-19 dashboard by the Center for Systems Science and Engineering at Johns Hopkins University [6] and information from the Department of Disease Control, Ministry of Public Health, Thailand there have been 1,174,091 confirmed cases and 11,143 deaths as of August 29, 2021 [7]. Bangkok is the city with the highest number of reported cases in Thailand.

During the COVID-19 pandemic, the Faculty of Dentistry, Chulalongkorn University adjusted its dental services based on the control guidelines of the COVID-19 pandemic in Thailand. When the number COVID-19 cases rapidly increased, the Faculty limited dental treatment to patients requiring emergency or urgent care [8]. The protocol for preventing SARS-CoV-2 spread during dental treatment was strictly applied. The standard, contact, droplet, and airborne precautions were reconsidered and emphasized, which included patient screening, wearing appropriate personal protective equipment (PPE), strictly performing surface disinfection, limiting aerosol-generating procedures, effectively implementing local source control of dental aerosols, and improving the ventilation in our dental hospital [4, 9]. The preventive measures implemented by dental care providers are employed in our dental hospital. All personnel and individuals are required to wear a mask at all times in the hospital and public areas. Social distancing must be performed during all activities. Dental care providers who perform aerosol generating procedures must wear a cloth gown covered with a water-proof isolation gown, disposable hair cover, disposable shoe covers, N-95 mask, and face shield [10].

The percentage of asymptomatic cases in individuals testing positive for SARS-CoV-2 varies among studies [11–13]. A study of 565 evacuees from Wuhan demonstrated an asymptomatic ratio of 30.8% [11]. Notably, SARS-CoV-2 infected individuals can transmit the virus to others during the pre-symptomatic or asymptomatic periods [14].

The recommended patient screening protocol of measuring body temperature and risk history taking cannot effectively identify infected individuals, especially those without symptoms [10]. Ideally, pre-screening dental patients with a SARS-CoV-2 nasopharyngeal swab for real-time polymerase chain reaction or antigen rapid test was suggested, however, the expense might be prohibitive [15]. The use of a nasopharyngeal swab for real-time polymerase chain reaction test is impractical in some situations due to the high cost, such as when patients are required to frequently visit the dental clinic to continue their treatment. As of August 30, 2021, the Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand began requiring the SARS-CoV-2 antigen rapid test for patients requiring aerosol-generating procedures. In addition, the faculty encourages a routine use the SARS-CoV-2 antigen rapid test for screening dental care providers and dental hospital personnel. However, there are a few limitations to rapid antigen testing, e.g., false negative results due to the incubation period, the sensitivity and specificity of a particular test kit, and poor sample collection technique [16, 17]. Screening with rapid antigen testing would be beneficial to exclude asymptomatic SARS-CoV-2 infected individuals from receiving treatment at that time. However, this screening procedure is not mandatory in general dental treatment in Thailand because patients are not required to undergo a nasopharyngeal swab test prior to dental treatment. Thus, it is inevitable that dental hospitals/clinics will treat pre-symptomatic or asymptomatic COVID-19 patients. Similarly, dental personnel, i.e., dentists, dental hygienists, dental assistants, and receptionists, could also be infected without developing symptoms and perform their duties without knowing that they are infected. Although a daily screening protocol for dental staff and self-monitoring for signs and symptoms of SARS-CoV2 infection can be enacted, dental personnel with an asymptomatic SARS-CoV2 infection might still report for work. Once symptoms develop and an individual tests positive for SARS-CoV-2, the appropriate protocols to identify the exposure risks of any dental staff and patients that had come in close contact with that person should be promptly applied.

Procedure guidelines should explicitly classify the risk of closely contacted persons. Here, we describe our procedural guidelines to manage the situation after receiving a report of a SARS-CoV-2 infected dental personnel and/or patients after visiting the dental hospitals/clinics. Initially, a timeline investigation of the confirmed cases in the dental hospitals/clinics is conducted. Subsequently, the closely contacted individuals are identified and categorized according to their risk of exposure. These individuals must be notified and informed of the appropriate guidelines for preliminary self-care and monitoring. The potentially contaminated area where the indexed case was at has to be evaluated and properly disinfected. Importantly, the appropriate information should be effectively disseminated in the organization and public. The implementation of this procedural guideline in the Faculty of Dentistry, Chulalongkorn University is also described as a case study. The aim of the present case study was to share our procedures to prevent and monitor the SAR-CoV-2 spread in the dental hospital and this could be further applied and modified to surveil the potential transmission in other dental clinical setting.

The procedure guideline described in the present case study was modified from the general guideline of the Department of Disease Control of Thailand [18]. There is no other specific guideline for dental hospitals in Thailand. Hence, the effectiveness and benefit of these current procedures cannot be described in comparison to other procedures. However, based on our dental hospital experience, we effectively controlled and monitored the transmission in our hospital. There was no identified infection that occurred during dental treatment in our hospital and there was no uncontrolled SAR-CoV-2 spread in our clinical setting. In addition, our school hosted a public seminar to present our procedural guidelines for the Thai dental community to demonstrate them as a case study that can be further implemented in their dental practice.

In the present case study, there was no report of SAR-CoV-2 transmission from dental treatment procedures. This result may be due several factors. The school limited treatment to those requiring urgent or emergency treatment when there was a high rate of confirmed cases in Thailand. Furthermore, the school installed equipment to improve the ventilation and air disinfection in the dental clinic. Finally, wearing the appropriate PPE was strictly enforced and universal infection control and disinfection were routinely performed.

Our experience is similar to that found in other Asian counties. Two case reports from Singapore described that dental personnel who inadvertently performed aerosol-generating procedures (scaling and root canal treatment) on patients who had tested positive for COVID-19 did not become infected after exposure and quarantine [19]. A study from Hangzhou, China investigated the SARS-CoV-2 detection and serological IgG/IgM testing of 757 hospital staff (dentists, nurses, students, security guards, and cleaners) at the Affiliated Stomatology Hospital, Zhejijang University School of Medicine after reopening after the lockdown period [20]. This study reported that 49,007 patients visited the hospital and some of those underwent aerosol-generating procedures. Pre- and peri-operative COVID-19 preventive procedures for the dental setting were performed according to the situation described [20]. Their results demonstrated that none of the hospital staff tested positive after RT-qPCR as well as IgG and IgM testing [20]. However, it should be noted that the sensitivity and specificity of the testing methods could have generated false negatives, which could be confounding factors in this study [20]. Furthermore, there was no COVID-19 transmission found between patients and dental personnel after dental practice in Hong Kong resumed [21]. A retrospective study in Yichang, China reported that there were no confirmed cases of COVID-19 transmission due to dental procedures in the stomatology department that provided treatment while strictly adhering to cross-infection prevention protocols [22].

In contrast to the reports describing no COVID-19 transmission due to dental treatment, the Indonesian Medical Association reported that six dentists died from COVID-19. However, there were no details on how and where these dental personnel were infected [23, 24]. Therefore, an appropriate and structured study must be performed to confirm this finding. The continuous reevaluation of the procedure guidelines should be performed to implement them appropriately in the specific circumstances.

The present article described the procedures used in managing a report of SARS-CoV-2 infected dental personnel or patients at the Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand. With this developed procedure, we can identify potentially infected individuals and limit the spread in the dental treatment environment. This procedure could be further implemented in other dental clinics to identify and monitor the transmission risk among dental patients and personnel. During the COVID-19 pandemic in Thailand, the potential SAR-CoV-2 transmission from a patient to dental personnel or from dental personnel to a patient from dental treatment procedures was not reported in our school. We learned from the present study that effective and timely management for identifying potentially infected individuals is beneficial to control the spread and to monitor the contaminated person/area in the dental hospital. Aerosol-generating dental treatment procedures have a high risk of transmitting SAR-CoV-2 during dental treatment. However, strictly enforced universal infection control and disinfection can prevent transmission in the dental setting. Hence, these strict infection control procedures must be routinely performed. Improved ventilation and air disinfection in the dental clinic is also strongly recommended.

PP, RA, and TO contributed to design and draft the paper. All authors contributed to data extraction and analysis of the paper content and approved the final version for publication.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.