Characteristics of Aerosols Generated from an Ultrasonic Scaling Device and Prevention of Diffusion by Intra- and Extraoral Suction Devices

: Aerosol infection is one of the routes of transmission of the new coronavirus (COVID-19), which continues to rage around the world. Aerosols generated by ultrasonic scalers, which are fre-quently used in periodontal treatment, are of concern as a source of cross-infection, but the characteristics of the aerosols are not clear. The purpose of this study was to investigate the characteristics of aerosols generated by ultrasonic scalers through fluid engineering studies using a particulate visualization system, and to evaluate the effectiveness of intra- and extraoral suction devices in preventing aerosol diffusion through simulated clinical studies using water-sensitive test papers and particle counters. From the fluid engineering study, the average particle size of the aerosol generated by the ultrasonic scaler was found to be about 40 μ m, and the droplet velocity to be 3 m/s. A clinical study using water-sensitive test papers revealed the effect of the orientation of the ultrasonic scaler on the direction of aerosol dis-persal. In addition, analysis using a particle counter showed that the amount of aerosol with a particle size of 1-10 μ m dispersed decreased with the distance, and it was confirmed that the amount of aerosol decreased significantly with the use of intra-oral vacuum suction. These results suggest that the risk of cross-infection via aerosols can be suppressed by appropriate use of a suction device for aerosols of vari-ous particle sizes generated by ultrasonic scalers.