Antibacterial Effect of Xanthorrhizol Mixed in Experimental Fluoride Varnish

Objectives: Fluoride varnish is known to be effective to prevent dental caries. Xanthorrhizol that is reported to have superior antibacterial effect against oral bacteria, especially S. mutans, was added into experimental fluoride varnish. It was aimed to develop a new fluoride varnish with antibacterial activity against S. mutans.
Methods: Experimental rosin-based fluoride varnish that contains 5 wt% NaF were fabricated. Agar diffusion test was conducted with experimental fluoride varnish itself, 1 mM xanthorrhizol, and experimental fluoride varnish+xanthorrhizol against S. mutans. Minimum inhibitory concentration (MIC) and minimal bacterial concentration (MBC) of xanthorrhizol and fluoride varnish+xanthorrhizol were also measured. Statistical analysis was done using ANOVA and Duncan’s multiple range test at α=0.05 (SPSS 12.0).

Results: In agar diffusion test, antibacterial effect of experimental fluoride varnish itself (14.69±0.57 mm) was significantly higher than 1 mM xanthorrhizol (9.83±0.69 mm) (P <0.05). Experimental fluoride varnish+xanthorrhizol (22.42±1.32 mm) showed significantly higher antibacterial activity than fluoride varnish itself and even positive control (18.07±0.06 mm) (P <0.05). The MIC of xanthorrhizol was lower (0.000875 mM) than that of xanthorrhizol+fluoride varnish (0.031 mM). The MBC of xanthorrhizol was lower (0.0035 mM) than that of xanthorrhizol+fluoride varnish (0.062 mM).
Conclusions: Xanthorrhizol mixed in experimental fluoride varnish showed synergy effect on antibacterial activity against S. mutans. This study suggests that xanthorrhizol can be used with fluoride varnish successfully to prevent dental caries.