Efficacy of propolis fluoride and nano silver fluoride for inhibition of streptococcus mutans and enterococcus faecalis biofilm formation

Objective: The objective of this study is to investigate the potency of propolis fluoride (PPF) and nano silver fluoride (NSF) as fluoride-based varnishes for inhibiting Streptococcus mutans and Enterococcus faecalis biofilm formation. In this study, both varnishes were compared to silver diamine fluoride (SDF) varnish, the gold standard for anticariogenic agents. Methods: The suspensions of S. mutans and E. faecalis were cultured and then plated into 96 - well plates and combined with SDF (38%), NSF (3.16, 3.66, and 4.16%), or PPF (3, 6, and 10%). E. faecalis was incubated in an anaerobic environment for 24 h, and the same protocol was used for S. mutans. The amount of biofilm inhibition was evaluated by optical density measurements at 570 nm using a microplate reader. Data were analyzed using one-way ANOVA. Results: The minimum inhibitory concentration (MIC) of PPF for S. mutans was 3%, and minimum bactericidal concentration (MBC) was 10%. The MIC of PPF for E. faecalis was at 6%, but no MBC was established. The MIC of NSF for S. mutans was 3.16%, and the MBC was 4.16%. The MIC of NSF for E. faecalis was 3.16%, while the MBC was 4.16%. Biofilm formation was inhibited dose-dependently by both NSF and PPF. Conclusion: NSF and PPF fluoride-based varnishes show clear antibacterial effects that are comparable to those obtained with SDF fluoride-based varnish.