Effect of Antibacterial Agents in Fluoride Varnish Against Streptococcus mutans

Objectives: Antibacterial activities of fluoride varnish against microorganism related to dental caries can be increased by incorporation of antibacterial agents. The purpose of this study was to investigate the antibacterial effect of natural antibacterial agents with and without fluoride varnish against Streptococcus mutans (S. mutans).
Methods: Experimental fluoride varnish (EFV) that contains 5 wt % NaF was fabricated. The following five antibacterial agents were tested: 1 mM and 10 mM of Xanthorrhizol (XAN), Bakuchiol (BAK), Bavachalcone (BCO), Isobavachromene (ISO), and Bavachromene (BME). Agar diffusion test, MIC, MBC and MTT test were conducted on antibacterial agents with and without EFV. Using 1.1 × 10¹⁰ CFU/ml of S. mutans, MIC and MBC were evaluated. Statistical analysis was done with ANOVA and Duncan’s multiple range test at α=0.05.
Results: In agar diffusion test, both 1 mM and 10 mM BCO showed the highest antibacterial effect in both conditions without EFV and with EFV among the experimental groups (P<0.05). Without EFV, the MIC of BAK, BCO, and ISO was the lowest (0.015 mM), and the MBC of BAK was the lowest (0.031 mM). With EFV, the MIC (0.031 mM) and MBC (0.062 mM) of BAK was the lowest, respectively. In MTT test, 1 mM BME and XAN showed the highest cell viability without EFV, while 1 mM BME showed the highest cell viability with EFV (P<0.05).
Conclusions: BCO with and without EFV showed the most effective antibacterial effect in agar diffusion test. BAK with and without EFV showed the most effective MIC and MBC. This study suggest that BCO and BAK have a possibility to be used with fluoride varnish to develop an antibacterial fluoride varnish.