Aerosol dynamics in dental clinics: Effects of ventilation mode on the mitigation of airborne diseases transmission

Abstract

Dental operations inherently involve a high risk of airborne cross-infection among medical staff and patients due to the exposure of respiratory secretions, which contain pathogenic microorganisms and typically spread in the form of aerosols. In order to contribute to the understanding of aerosol dynamics during dental operation and efficiently mitigate their dispersion and deposition through appropriate ventilation, 3D numerical simulations and full-scale experimental measurements were performed in this study. The indoor airflow distribution and dynamic aerosol behaviors observed under three optimized ventilation schemes (Scenario I-III) were compared with those observed under the current ventilation system. Qualitative analysis was performed together with quantitative examination using the air age, air change efficiency, contaminant removal effectiveness, and deposition ratio. It is demonstrated that the ventilation currently in use is unable to effectively discharge aerosols, resulting in most of them depositing on surfaces routinely accessed by dental workers. The pronounced air mixing effect induced by the design of Scenario I facilitates the rapid dispersion of aerosols throughout the clinic, impeding the efficient removal via the outlet. Moreover, the effective elimination of indoor aerosols is only attainable by implementing high ventilation rates in Scenario II. The Scenario III exhibits better overall performance, as evidenced by the successful discharge of approximately 69.8% of injected aerosols with limited deposition on indoor surfaces under ACH = 6h^-1, and further enhanced performance is observed at higher ACHs for contaminant removal. The prevailing ventilation design in dental clinics, which primarily focuses on maintaining a desirable temperature and relative humidity, often overlooks the necessity of proper ventilation for reducing the exposure risk of occupants. This study provides solid evidence for the upgrading or reconstruction of ventilation systems in dental clinics, aiming to promote a safe and healthy treatment environment.

Keywords: Aerosol dynamics; Aerosols; Dental clinic; Public health; Ventilation.