Effectiveness of respiratory protective equipment in reducing inhalation and contact exposure risks of dental workers during ultrasonic scaling

The high-concentration droplets produced from ultrasonic scaling treatments may carry many pathogens. The close contact between dental workers and patients significantly amplifies their exposure risk to these droplets. Although various types of respiratory protective equipment (RPE) are utilized by dental workers during treatments, their effectiveness in reducing the risks associated with inhalation and contact exposure remains uncertain. In this study, computational fluid dynamics technology was employed to investigate the impact of RPE type, surgery duration, air changes per hour (ACH), and air distribution on the risks related to inhalation and deposition exposure. The results revealed that wearing masks considerably reduced the risk of inhalation exposure for dental workers, with a decrease in inhalation fractions from 25.3 ppm (without RPE) to 1.3–4.5 ppm (with RPE). Combining blue surgical masks and face shields decreased the risk of inhalation fraction by 5% compared to wearing no RPE. Notably, there was over 60% of spray droplets landed on the patient's head; however, only approximately 5%, 6%, 8%, and 3% were deposited on the patient's body, doctor's body, floor, and dental chair, respectively. Increasing ventilation from 3 to 9 ACH decreased dental workers' inhalation fraction by 9.8 ppm. Type III (with the inlet and outlet at opposite walls) decreased the suspension fraction by 4.3% compared with Type II (with the inlet and outlet at the same wall) while achieving a near-zero inhalation fraction of dental workers. These findings offer valuable insights for mitigating cross-infection risks between dental workers and patients in dental clinics.