Virucidal Activity of Different Mouthwashes Using a Novel Biochemical Assay

Background: Saliva of patients with COVID-19 has a high SARS-CoV-2 viral load. The risk of spreading the virus is not insignificant, and procedures for reducing viral loads in the oral cavity have been proposed. Little research to date has been performed on the effect of mouthwashes on the SARS-CoV-2 virus, and some of their mechanisms of action remain unknown.

Methods: SARS-CoV-2 positive nasopharyngeal swabs measured by RT-PCR were used for virucidal activity in a 1:1 ratio, with an incubation time of 1 min. The solutions used in this study were: iodopovidone (8 mg); * D-limonene, a terpene extracted from citrus peels (0.3%); ^† cetylpyridinium chloride (0.1%) (CPC); ^‡ chlorhexidine gluconate (10%) (CHX); ^§ a CPC (0.12%) and CHX (0.05%) containing formula; ** a formula containing essential oils; ^†† a CPC containing formula (0.07%); ^‡‡ a D-limonene (0.2%) and CPC (0.05%) containing formula; ^§§ a solution containing sodium fluoride (0.05%) and CPC (0.075%); *** a solution containing CHX (0.12%) and; ^††† a CHX (0.2%) containing formula. ^‡‡‡ As a control reaction, saline solution or excipient solution (water, glycerin, citric acid, colorant, sodium citrate) was used.

Conclusion: Within the limitations of this study, we can conclude that a mouthwash containing both D-limonene and CPC reduced the virucidal activity in about 6 logs (>99.999% reduction). Hence, establishing a clinical protocol for dentists is suggested, where all patients to be treated rinse pre-operatively with a mouthwash containing both D-limonene and CPC to reduce the likelihood of infection with SARS-CoV-2 for dentists. This is a relatively inexpensive way to reduce viral transmission of SARS-CoV-2 from infected individuals within the community. It is also a simple way to decrease infections from asymptomatic and pre-symptomatic patients.