In the present study, a similar questionnaire was administered to almost the same subjects to investigate COVID-19 transmission in dental practice during different infectious disease pandemics (1st -5th vs 6th -9th surge in Japan). The results of this survey showed that no nosocomial infections were observed in the dental clinics even when the number of COVID-19 patients increased explosively. The number of COVID-19 positive patients increased approximately 50-fold between the study periods that were compared. In addition, the results of this study also showed that the number of COVID-19 patients treated at dental clinics also increased approximately 2-fold (from 9 to 17), and the number of dental staff identified as concentrated contacts of COVID-19 patients increased approximately 3.5-fold (from 18 to 62). Although dental care restrictions were in place in the early stages of the spread of the infection, the rate of dental care restrictions also declined, as indicated by the results of this survey (61.2% in the 1st -5th surge vs. 37.7% in the 6th -8th surge). As mentioned above, even with the increased likelihood of contact with COVID-19 patients, no cases of infection during dental treatment have been observed.
The results of a previous study12 suggested that entrance screening (water-front measures), standard infection control measures such as contact infection control and standard PPE (masks, face shields, eye guards, gloves, gowns, and aprons), use of extraoral vacuums, and encouraged gargling would play an important role in infection control in dental practice. In the current survey results, these infection control measures were still being implemented at the same high rates as before. In addition, vaccination coverage was also high at approximately 80% in both study periods. These results suggest that the situation in which such infection control measures are implemented in dental practices is probably the reason why COVID-19 infections associated with dental treatment are virtually nonexistent.
During the period of this study, a total of 183 dentists reported that staff members, including dentists themselves, had been infected with COVID-19. The results of this study suggested that transmission occurred outside dental care, at home, at school, at office, or at other crowded indoor settings. In fact, in this survey, 15 indicated that there was COVID-19 transmission among clinical staff members outside dental care. The risk of viral transmission is high during unmasked communication13,14. Infection of medical staff affects the delivery of health care 15. At the time of this survey, 17.4% of dental clinics reported having to close their offices. In a pandemic of respiratory infections, the health of medical staff is important, as is attention to nosocomial infections.
As noted in our previous report, this survey has several limitations. First, this survey was conducted in a single prefecture in Japan. It is unclear whether similar results would be obtained in a larger national survey. Second, the overall response rate was 31.0%, which may indicate some degree of potential selection bias. Respondents may have been more concerned or worried about safety measures than non-respondents were. However, given the need for timely information and the rarity of medium to large surveys of COVID-19 measures in private dental practices, the data from this study may be useful to clinicians. Finally, because the survey was self-reported, there is a small possibility of misclassification by the individual practicing dentists who responded.
In conclusion, the results of this study indicate that even if COVID-19 infection were to spread and the number of infected patients were to increase approximately 50-fold in a short period of time, the likelihood of COVID-19 clusters occurring in dental practices is low if appropriate infection prevention measures are in place.