The Impact of Fluoride Varnish Application on the Supragingival Plaque Microbiome in Preschoolers: A Dynamic Study

Fluoride varnish application is used in many studies as a minimally invasive technique to prevent caries. Notably, oral microorganisms play a crucial role in the incidence and progression of tooth caries. However, the effect of fluoride varnish application on the dynamic microbial alterations that occur in dental plaques remains unclear. In this study, we investigated the impact of fluoride varnish application on the supragingival microbial composition and structure in preschoolers. We enrolled 27 preschoolers and collected supragingival plaque samples from the same sites at multiple time points: baseline (0 h, F0 group), 24 h (F1 group), 1 month (F2 group), 3 months (F3 group), and 6 months (F4 group). To unravel the changes in microbial composition and structure after fluoride varnish application, all specimens underwent high-throughput sequencing of the 16 S rRNA gene. The Shannon and Simpson indices showed no significant differences across groups (P > 0.05). Principal co-ordinates analysis (PCoA) revealed significant differences in microbial community structures across all time points (P < 0.001, R² = 0.44), with F0 and F1 groups showing similarity. Significant variations in bacterial composition were observed among eight strains, including Neisseria mucosa and Corynebacterium matruchotii (P < 0.05). This study found that Duraphat fluoride varnish application effectively modifies the composition and structural characteristics of supragingival plaque in preschoolers, enhancing anti-caries properties.