Reduction of SARS-CoV-2 salivary viral load with pre-procedural mouth rinses: a randomised, controlled, clinical trial. Br Dent J 2023; 234: 593-600

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Why did you decide to undertake this study?

When the COVID-19 pandemic hit in early 2020, the world as we knew it was upended, with no long-term solutions in sight. Gradually, people realised that sheltering was not sustainable, and we would have to learn to cope with the virus, as its elimination was nearly impossible. The dental community was particularly vulnerable because our very service is in faces and mouths, from which the virus spreads. We noted that providers were taking many precautions to protect themselves, from homemade PPE to cleansing rituals, but with little evidence to support their practices. Providers in our own community were using everything from bleach and peroxide to private concoctions as pre-procedural mouth rinses, but there was very little clinical literature on the effectiveness of mouth rinses in reducing oral viral load, virtually nothing specific to COVID-19, and sparse information on what performed best and for how long. We set out to study which of four commonly used mouth rinses performed best, if any, in reducing oral SARS-CoV-2 viral load, and for how long over clinically meaningful time points in participants with active SARS-CoV-2 infection. We encountered many hurdles given the nature of our study, including challenges in enrolment and with safety precautions.

Did any of the results surprise you?

To our surprise, while limited in study power, we found that Listerine, an alcohol-based mouthwash with oils including thymol, worked better and longer than other rinses including diluted betadine and hydrogen peroxide.

What do you think the next steps should be considering your findings?

Our findings provide additional evidence to support the use of mouth rinses, like hand-washing, in preventing the spread of infectious agents in the dental office, and we hope to enrol more patients in a larger trial to expand our clinical evidence.