# Control of Viral Aerosol Dispersion During Simulated Dental Procedures

## TL;DR

This study shows that combining high-volume evacuation and air-cleaning systems is most effective at reducing virus spread during dental procedures.

## Contribution

The study provides the first comprehensive assessment of viral aerosol mitigation in dental procedures using combined HVE and ACS.

## Key findings

- ACS plus HVE reduced viral spread more than either method alone, especially at distant locations.
- Viral load in large aerosols was 93% lower with combined HVE and ACS compared to control.
- RT-qPCR showed over 80% reduction in viral detection with combined HVE and ACS.

## Abstract

Although air-cleaning systems (ACS) and high-volume evacuation (HVE) have been shown to reduce dental bioaerosols, few works have looked at viruses. This study aimed to assess the effects of HVE and ACS on dispersion of aerosolised particles and airborne viruses in a simulation model of dental bioaerosols using a detailed and comprehensive sampling approach and different tracer molecules.

MS2 bacteriophage and fluorescein solution were used as viral or dispersion tracers, respectively. These were added independently to the instrument irrigation system and aerosolised during dental procedures. Aerosol mitigation condition groups were ACS, HVE, ACS plus HVE, and No mitigation (control). Aerosols were collected via settlement onto sterile filter papers and agar plates. In addition, a 6-stage Andersen cascade impactor was used for viral air sampling. Fluorescent particles were analysed using ImageJ software, and bacteriophage was quantified using plaque assays and reverse transcription quantitative polymerase chain reaction (RT-qPCR).

HVE combined with ACS produced the highest reduction in viral spread among the three aerosol-generating procedures (AGPs). This reduction was evident both in the number of fluorescent particles and that of viruses. The effect was more pronounced at the farthest sites. By plaque assay, viral loads in the largest-sized aerosols (>7.0 μm) from air samples were 93% lower in the ACS plus HVE group compared with control, and the load in the smallest aerosols (0.65-1.1 μm) was reduced by 84% (P < .05). By RT-qPCR, the ACS plus HVE group also reduced viral detection in air samples (>80%) more than ACS or HVE alone compared with the control group (P < .05). In ACS or HVE condition, viral RNA was detected even in the absence of infectious virus detected by plaque assay for anterior versus posterior procedures and in the farthest positions.

A synergistic effect was obtained in the reduction of aerosolised particles and viruses from surfaces and air samples when HVE was combined with ACS.

Using a comprehensive and depth assessment, this study found that the combination of high-volume evacuation and air-cleaning systems was the most effective measure in mitigating virus dispersion during aerosol-generating dental procedures, translated into lower required waiting (fallow) times between patients’ appointments for dental care depending on the type of AGP conducted. The more aerosols are produced during an AGP, the longer it takes to prevent cross-contamination among dental staff and patients. In addition, our findings support the use of HVE, face shields, and well-fitting masks in dental procedures, not only during pandemics but also in everyday practice.