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.
The COVID-19 pandemic has had a devastating impact on society, claiming over six million lives since its first detection in December 2019.1 Despite such adversity, health care practitioners continue to dutifully serve those in need. Given the role of the oral cavity in the pathogenicity and transmission of SARS-CoV-2 and routine exposure to aerosol generating procedures, dental care professionals are at great risk of contracting the disease. Alongside stringent handwashing and the use of level 3 personal protective equipment, the American Dental Association also advocated the use of pre-procedural mouth rinses to reduce oral SARS-CoV-2 viral load.2
Although their use is now supported by systematic reviews,3,4,5 the recommendations of mouth rinsing prior to routine dental procedures were largely based on laboratory findings, with little empirical evidence available at the time. These mouth rinses were shown to be effective in reducing oral viral load, but the significance of this in preventing disease transmission during dental procedures was unknown. As such, the authors of this paper set out to investigate the ability of pre-procedural rinses to suppress oral viral load over a clinically meaningful period of time.
Thirty-three eligible COVID-19 patients were recruited from the Augusta University Medical Centre drive-through testing facility (Georgia, USA) for a prospective trial investigating the effectiveness of 0.12% chlorhexidine gluconate, Listerine (McNeil-PPC Inc., USA), 1% povidone-iodine and 1.5% hydrogen peroxide-based mouth rinses in reducing oral SARS-CoV-2 viral load compared to rinsing with water. Unstimulated whole saliva samples were collected by participants under remote supervision a few days after testing positive. Samples were collected before, immediately after, one hour and two hours after rinsing for two minutes with a randomly allocated, coded mouth rinse. Real-time reverse transcription polymerise chain reaction was then used to determine oral viral load at each timepoint via nucleocapsid and ORF1ab gene markers.
Despite past recommendations of using 1% povidone-iodine and 1.5% hydrogen peroxide pre-procedural mouth rinses, this study suggested their protective effects were short-lived at best. The abundance of the nucleocapsid gene marker for all interventions was significantly lower than the control immediately after rinsing. However, only Listerine was capable of significantly reducing both nucleocapsid and ORF1ab gene marker abundance when compared to water. The protective effect of Listerine was also sustained across the two-hour follow-up period.
The authors of this study encourage the findings to be interpreted with caution. Difficulties in participant recruitment, retention and sample collection left this study underpowered and biased towards the effectiveness of Listerine. Whilst no mouth rinses showed any significant difference in oral viral load across time points, the study highlights the need for further investigation into the ability of pre-procedural mouth rinses to prevent COVID-19 transmission.
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Moosavi M-S, Aminishakib P, Ansari M. Antiviral mouthwashes: possible benefit for COVID-19 with evidence-based approach. J Oral Microbiol 2020; 12: 1794363.
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Daly, J. 'The dentist will see you now...'. Br Dent J 234, 810 (2023). https://doi.org/10.1038/s41415-023-5977-4