Suppress the aerosol generation from the air turbine handpiece in dental clinics

The COVID-19 pandemic imposes a severe challenge to the health care providers and patients in dental clinics as the dental procedures produce abundant airborne materials. Although dental practices use a multi-layered protective procedure to reduce the potential danger from dental aerosols, it is still beneficial to suppress the aerosol generation from the origin as much as possible. Reducing the aerosol generation (especially the droplets of smaller diameters) from the very beginning will ease the burden on all subsequent layers of protection. In this work, we first provide a relatively complete picture of the structure of the spray produced by the air turbine handpiece. We found that the spray consists of two domains: one is the canopy shaped centrifugal zone and the other is a dense ballistic spray core. The droplets from the centrifugal zone are much smaller than those of the spray core and, hence, are more prone to stay in the air. The location of the centrifugal zone also makes it more challenging to be contained by the mouth or rubber dam. To suppress the atomization of the centrifugal zone, we used the food-additive carboxymethylcellulose sodium (CMC-Na) water solutions of different concentrations. The data show that the viscoelastic property of the 0.5 wt. % CMC-Na water solution can effectively suppress the aerosol generation of the centrifugal zone.