Oral Mouthrinses and Reduction in Salivary SARS-CoV-2

During the COVID-19 pandemic, dental students and dental professionals have implemented a number of precautionary measures with the objective of reducing the risk of transmission. One such measure is the increased use of pre-procedural rinsing.

Certain pre-procedural rinses have been shown to reduce microbial load in the oral cavity, and by extension the load present in spatter and aerosols generated during dental procedures. SARS-CoV-2, the pathogen that causes COVID-19, is also transmitted largely via aerosols, and to a much lesser extent by droplets.

Based on this knowledge, it was theorized that pre-procedural rinsing may reduce salivary loads of SARS-CoV-2 and thereby the risk of transmission from COVID-19-positive patients. Many dental professionals adopted pre-procedural rinsing as standard for every patient, and now data is emerging that is supportive of this precautionary measure.

New research on pre-procedural rinsing and SARS-CoV-2

SARS-CoV-2 has been detected in the saliva, gingival crevicular fluid, oral mucosal cells and salivary glands of infected patients, suggesting that the oral cavity acts as a reservoir for the virus. A 2021 pilot study investigated the efficacy of mouthrinses in reducing the salivary viral load of SARS-CoV-2. The following solutions were used as rinses in the study:

• Distilled water (placebo)

• 0.075% cetylpyridinium chloride and 0.28% zinc lactate solution (CPC + Zn)

• 1.5% hydrogen peroxide solution (HP)

• 0.12% chlorhexidine gluconate solution (CHX)

• 1.5% hydrogen peroxide solution followed immediately by a 0.12% chlorhexidine solution (HP + CHX).

Researchers found that immediately after rinsing, the CPC + Zn mouthrinse produced a >20-fold reduction in viral load compared to baseline, and the HP rinse resulted in a >15-fold reduction. At 30 minutes, both still showed a significant reduction in viral load. By 60 minutes, the CPC + Zn group had maintained a modest 2.6-fold reduction, while for the HP rinse the viral load had returned almost to baseline levels. The CHX rinse, in comparison, showed a modest and significant >2-fold reduction in viral load immediately after rinsing. However, the reduction had increased to 6.2-fold by 30 minutes. At 60 minutes, CHX maintained a 4.2-fold reduction, higher than the 2.6-fold reduction shown by the CPC + Zn rinse at the same time point.

Sequential use of HP + CHX did not show a significant reduction in viral load immediately after rinsing, and HP alone had achieved a much larger reduction at this time point. It is thought that subsequent use of CHX immediately after using the HP rinse, resulted in the HP being rinsed away from the oral cavity before it could have a measurable effect.

Previous findings in practice

Up until now, there has been little scientific data supporting pre-procedural rinsing as a measure to reduce viral loads of SARS-CoV-2 specifically. Its precautionary use during the pandemic was based on what we already knew about the effects of pre-procedural rinsing on other pathogens. For example:

• CHX, as found in Colgate PerioGard, has been shown to reduce the intra-oral load of certain aerobic and anaerobic bacteria in the oral cavity.

• CPC, as found in Colgate Total 12 HR Pro-Shield Mouthwash, has been shown to reduce intra-oral bacterial loads, to kill 99.9% of bacteria on contact and to help reduce aerosolized oral bacteria when used as a pre-procedural rinse.

• HP, as found in Colgate Peroxyl, is an oxidative agent and has been shown to reduce bioburden when performing procedures.

Conclusions

The findings of this pilot study showed that use of pre-procedural rinses had a significant and measurable – albeit transient -- effect on salivary viral loads of SARS-CoV-2. While the pilot study does have some limitations, such as its small sample size, and more research is needed, this study is supportive of pre-procedural rinsing with the objective of reducing salivary viral load during procedures in these challenging times.