LAUSR

The spreading of SARS-CoV-2 disease by infected, asymptomatic subjects is one of the greatest concerns in controlling the pandemic (Gandhi et al., 2020), especially in the dental setting, where the aerosol generated by dental handpieces (Harrel & Molinari, 2004) that contaminates virtually any dental operatory surface (Ionescu et al., 2020) may substantially increase the risk of SARS-CoV-2 airborne transmission (Ge et al., 2020). In the struggle to reduce the risk of such infection by dental aerosols and spatter, two non-mutually exclusive strategies have been proposed: enhancing protection through personal protective equipment (PPE) (Herron et al., 2020) and mitigating aerosol spreading, for instance using high-volume evacuator (HVE) (Ravenel et al., 2020) and adding antiviral agents to the cooling spray of dental handpieces. We designed a study to evaluate in vitro the protective efficacy of different types of PPEs, and the efficiency of a hydrogen peroxide-based spray in reducing a coronavirus viral load, similar to that of asymptomatic patients, dispersed during a conventional dental procedure. Into a class III cabinet-like, pressure-tight, custom-built chamber, dental practice was reproduced using phantom heads for both patient and operator, and a routine procedure using aerosol-generating air turbine was performed (Figure 1). An artificial saliva solution containing 6.03 ± 0.04 log10 gene copies/ml of coronavirus 229E (the amount of viral load of an asymptomatic person) (Han et al., 2020) was inserted into a patient-simulating phantom dummy, before operating the air turbine with the air spray for 10 s. The operator phantom was equipped with different types of PPE on several consecutive runs, including surgical masks, N95/ FFP2 and FFP3 respirators, and face shields, while a vacuum pump simulated the operator's breathing. The influence of HVE and the addition of 0.5 vol% H2O2 to the handpiece's water intake in mitigating viral loads were also tested. After performing the dental procedure, the viral presence on the operator was assessed on its forehead, on masks’ and respirators' outer surface, and inside the mouth of the phantom (Table 1).