Interindividual differences in caries potential of the salivary microbiome after mouthwash exposure

Prevention and treatment of dental caries is often achieved by fluoride mouthwashes. The most common forms of fluoride are Stannous fluoride (SnF2), amine fluoride (AmF) and sodium fluoride (NaF), each with differing activities against oral bacteria. Additionally, differences in oral microbiome between individuals are linked to differences in response to treatment and the phenotype of the microbiome can provide information on this response. Flow cytometry can successfully track microbial phenotypic heterogeneity and may prove useful for capturing the response to treatment. In this study, we compared the effect of three fluoride-containing mouthwashes, Elmex Anti Caries (AmF/NaF), Listerine Anticaries (NaF) and Meridol (AmF/SnF2), on the salivary microbiome and assessed their anticaries potential. Furthermore, we investigated if the flow cytometric fingerprint could be used to capture the response to treatment. Saliva samples of different donors were treated with the mouthwashes and the intact salivary community composition was assessed using 16S rRNA gene amplicon sequencing. Treated saliva samples were incubated in sucrose-rich medium to assess the organic acid production of the remaining microbiota. Moreover, flow cytometric fingerprints of the intact microbial population were used to track the response to treatment and to train a random forest classifier predicting the most suitable mouthwash for the donor. We found a mouthwash-dependent shift in the salivary microbiome composition and found different anticaries potential of the mouthwashes. Meridol affected more bacterial taxa and had the best overall anticaries potential, followed by Elmex. Finally, the response to treatment could be captured in the flow cytometric fingerprint of the initial intact salivary microbiota and a random forest classifier predicting the most suitable mouthwash for the donor was successfully trained.