Peer to Peer: Preprocedural Rinsing and Dental Aerosols

Aerosols generated during dental procedures result in increases in aerosolized bacteria, viruses and fungi during and following treatment — and these aerosols can travel significant distances from treatment sites.^1,2 While preprocedural rinsing is an off-label use, mouthrinses used to reduce bacterial loads in dental aerosols include chlorhexidine gluconate (CHX), cetylpyridinum chloride (CPC), essential oils (EO) and povidone-iodine (PVP-I). Preprocedural rinsing has recently been recommended with the objective of reducing viral loads with SARS-CoV-2 during the COVID-19 pandemic.    

Bacterial Load Reduction — A recent systematic review of 13 randomized controlled clinical trials concluded there was moderate evidence for the efficacy of CHX, CPC and EO in reducing bacterial loads in dental aerosols.² Studies measuring salivary bacterial levels lend support for prerinsing.^3,4 At bactericidal concentrations, CHX and CPC disrupt bacterial cell membranes, resulting in leakage of intracellular proteins and cell death. In general, the mechanism of action for EO is similar. The use of PVP-I releases free iodine, which disrupts cell membranes and oxidizes proteins and fatty acids, resulting in cell death.

Viral Aerosols and SARS-CoV-2 — Although SARS-CoV-2 is transmitted primarily through droplets and contact, aerosols represent an alternative mode of transmission.^5,6 High viral loads of SARS-CoV-2 have been found in saliva in infected individuals and in the oropharynx of asymptomatic individuals.^7,8 Recently, preprocedural rinsing with 1.5% hydrogen peroxide or 0.2% PVP-I was suggested for dental patients.⁵ Both are oxidizing agents, and SARS-CoV-2 is susceptible to oxidation (Figure 1). In other geographic areas, 1% hydrogen peroxide has been recommended, and 3% hydrogen peroxide rinses have been suggested in patients with early COVID-19 infection.^6,9 Hydroxyl free radicals are produced by hydrogen peroxide and in vitro are known to attack membrane lipids, genetic material (which contains nucleic acids), and other cell components.¹⁰ Hydrogen peroxide rinses have a history of safe use. In addition, PVP-I has demonstrated in vitro efficacy against SARS-CoV and MERS-CoV, and was recommended for use against MERS-CoV during the MERS epidemic.^7,11 Free iodine oxidizes cell components containing amino and nucleic acids and disrupts proteins.^7,11

Conclusions — Preprocedural rinsing has been recommended to help reduce transmission of pathogenic microorganisms. At this time, there is no evidence for the use of any preprocedural rinse against SARS-CoV-2.¹² However, biologic plausibility suggests hydrogen peroxide and PVP-I could be expected to be virucidal intraorally, and may reduce SARS-CoV-2 viral load in dental aerosols. More research is needed on preprocedural rinses, the minimal infectious dose for SARS-CoV-2, and a quantifiable risk of SARS-CoV-2 transmission from dental aerosols.

REFERENCES

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From Decisions in Dentistry. June 2020;6(6):8.