Efficacy of personal protective equipment against coronavirus transmission via dental handpieces.

Background: This laboratory study was done to evaluate the efficacy of personal protective equipment (PPE) and high-volume evacuation (HVE) against the spread of human coronavirus type 229E (HCoV-229E) during a standard dental procedure.

Methods: Patient and operator manikins were used to recreate a dental setting inside a custom-built class III cabinet-like chamber. The mouth of the patient manikin was inoculated with an HCoV-229E suspension, the viral load of which was similar to that of asymptomatic people infected with severe acute respiratory syndrome coronavirus 2. The dental procedure was performed with an air turbine handpiece and HVE for 10 seconds. The efficacy of surgical masks, N95 (filtering facepiece class 2) and filtering facepiece class 3 respirators, and face shields was tested via quantitative real-time polymerase chain reaction.

Results: The wide surface on which the inoculum was spread caused low contamination. Over the external surfaces of masks and respirators, when a face shield was not worn, viral loads ranged from 1.2 through 1.4 log mean gene copies per cm. When the shield was worn, viral loads dropped below the detection limit (< 0.317 log gene copies/cm) for all PPE. On the operator's forehead, viral loads were 0.6 through 0.8 log gene copies/cm. Inside the operator manikin's mouth, viral loads were under the detection limit when 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 manikin's mouth to below the detection limit, but HVE did not decrease viral contamination.

Practical Implications: Although caution is suggested when removing and disposing of PPE to avoid self-contamination, the combination of PPE and face shields drastically decreases the risk of transmitting human coronavirus during aerosol-generating dental procedures.