Is there scientific evidence of the mouthwashes effectiveness in reducing viral load in Covid-19?: a systematic review

Background: The aim of this research is to verify whether there is evidence in the literature regarding the decrease in viral load present in saliva after using three types of mouthwashes. Material and Methods: Clinical and/or in vitro experimental studies that have used mouthwashes as a form of intervention to reduce the viral load in saliva were included. Combinations of words and appropriate truncations were adapted for each of the seven selected electronic bases including grey literature. Results: The selection of articles was carried out in two phases by two independent reviewers. After removing duplicate articles, 1245 references were maintained, and 2 articles were included in the Systematic Review. Both studies were performed in vitro and tested the virucidal action of the PVP-I solution for mouthwash at two different concentrations, 1% without dilution and 7% with 1:30 dilution, on the SARS-CoV and MERS-CoV viruses. Both showed a viral reduction of ≥ 99.99% with 15 s exposure. Conclusions: Based on the evidence currently available in the literature, PVP-I, at concentrations of 1 and 7%, appears to be the most effective mouthwash for reducing the viral load of COVID-19 present in human saliva. However, the guidelines for dental care refer to the use of hydrogen peroxide but there is insufficient scientific evidence to support this recommendation.