Efficacy of personal protective equipment against coronavirus transmission by dental handpieces

Background. This in vitro study evaluated the efficacy of personal protective equipment (PPE) and highvolume evacuation (HVE) against human coronavirus (HCoV) 229E spreading by a standard dental procedure. Methods. Phantoms for both patient and operator were used to recreate a dental setting inside a custombuilt class III cabinet-like chamber. The patient’s phantom mouth was inoculated with an HCoV-229E suspension having viral load similar to SARS-CoV-2 asymptomatic subjects. The dental procedure was performed using an air-turbine and HVE for 10 seconds. The efficacy of surgical masks, FFP2/N95 and FFP3 respirators, and face shields was tested using quantitative real-time PCR. Results. The wide surface on which the inoculum was spread caused low contamination. Over the masks and respirators’ external surfaces when a face shield was not worn, viral loads ranged 1.2 to 1.4 log10 mean gene copies/cm2 . When the shield was on, viral loads dropped below detection limit (<0.317 log10 gene copies/cm2 ) for all PPEs. On the operator’s forehead, viral loads were 0.6 to 0.8 log10 gene copies/cm2 . Inside the operator’s mouth, viral loads were under the detection limit using any PPE, with or without the shield. HVE did not significantly change viral loads. Conclusions. All PPE combinations significantly reduced viral loads in the operator’s mouth below the detection limit, but HVE did not decrease viral contamination. Practical implications. While extreme caution is suggested when removing and disposing of PPEs to avoid self-contamination, the combination of PPE and face shield drastically decreases the risk of human coronavirus transmission during aerosol-generating dental procedures.