Simulation of the spatiotemporal distribution of emitted droplets during air-powder-polishing and ultrasonic scaling

The dispersion characteristics of droplets during ultrasonic scaling and air-powder-polishing have not been clearly revealed. In this study, the Computational Fluid Dynamics (CFD) simulation method was used to investigate the spatiotemporal distribution characteristics of droplets using both the original method and the simplified method. In the original method, incisors and side teeth in the maxillary and mandibular were selected as emission positions for droplets. Emission angles and directions were based on experimental results. The simplified method involved a fixed emission position at the center of the mouth, with droplets emitted vertically upward at a coneshaped angle of 30 degrees. The results (original method) showed that during short duration air-powderpolishing (6 min), deposition was the primary outcome of droplets at the end of air-powderpolishing (80.7 %), followed by suspension (11.7 %) and escape (7.6 %). During the long duration ultrasonic scaling (30 min), similar distribution characteristics were observed compared to air-powder polishing. The main difference was a slightly lower cumulative suspension fraction at the stopping ultrasonic scaling and a slightly higher cumulative deposition fraction, with comparable durations of Fallow time (FT) being 31 and 32 min respectively. Regardless of whether it was air-powder-polishing or ultrasonic scaling, the simplified method increased medical workers' risk for inhaling emitted droplets by 1.2 times, compared to the original method. This study not only enhances understanding of the spatiotemporal distribution of droplets during dental treatments but also contributes to developing control measures for mitigating risks in dental clinics.