Inhibitory effects on Streptococcus mutans of antibacterial agents mixed with experimental fluoride varnish

We investigated the inhibitory effect of antibacterial agents mixed with experimental fluoride varnish (EFV) on Streptococcus mutans. The antibacterial agents used were (1 and 10) mM of xanthorrhizol, bakuchiol, bavachalcone, isobavachromene, and bavachromene. Agar diffusion tests were performed on S. mutans (1.1×10¹⁰ CFU/mL), using antibacterial agents without and with EFV. Bavachalcone showed the highest inhibition zone without and with EFV at both (1 and 10) mM (p<0.05). All EFV with antibacterial agents showed greater inhibition and semi-inhibition zones than EFV alone (p<0.05). The cell viability of each antibacterial agent was not significantly different from the vehicle controls (p>0.05), except xanthorrhizol and bakuchiol at 1 mM. All antibacterial agents were effective, while antibacterial agents with EFV co-formulations were more effective than EFV alone. Bavachalcone was the most effective agent against S. mutans, indicating its potential usefulness with fluoride varnish in preventing dental caries.