A study both to measure and to visualize the scattering of fine particles generated during dental treatment

There is an urgent need to examine the risk of infection from aerosols generated during dental treatment and to review infection control. However, existing research on aerosol particles associated with dental treatment is by no means sufficient, and little research has been done on the details of aerosol particle generation in the clinical environment, the mechanisms, and patterns of distribution in open and closed spaces, the time they are suspended in the air, the amount and size of particles present. Therefore, to minimize the influence of background particles, laser beams, a high-sensitivity camera, and a particle counter were used in a large super-clean laboratory (SCL) to investigate the dynamics of aerosols generated during dental micromotor operation. The large number of aerosol particles generated by the use of the micro-engine rose rapidly within 30 seconds and were suspended in the room atmosphere. Within a 100 cm radius of the user, the scattering peaked at about 90 seconds. The particles were further diffused into the room with the passage of time, reaching a maximum at 210 seconds and gradually decreasing thereafter, confirming that the 4 x 4 m room had returned to equilibrium. The experiment was conducted under sealed conditions in the SCL without the use of any suction device inside or outside the oral cavity. Although the conditions did not faithfully reproduce the actual conditions in a dental clinic, we were able to obtain groundbreaking results that demonstrated for the first time the scattering of fine particles, eliminating various possible complications in the background. At present, our knowledge of the infectivity of COVID-19 from patients' oral cavity and saliva is still insufficient, and further studies and information are needed.