Natural Compound-based Varnishes as Inhibitors of Cariogenic Biofilms

Objectives: In order to characterize a novel therapy for caries control, this study aimed to explore the anti-biofilm effect of experimental varnishes containing natural compounds.
Methods: Mono species biofilms of Streptococcus mutans, Lactobacillus acidophilus and Lactobacillus casei were grown in specific medium supplemented with 1% sucrose. Each mono culture were subjected to the following treatments: 1) 1.5% tt-farnesol + quercetin + theobromine; 2) 4.5% tt-farnesol + quercetin + theobromine and, 3) control without compound. The 0.2% chlorexidine digluconate was used as control of the experiment. The ability of varnishes to affect 24-h biofilm cell concentration and cell viability was checked by counting of the colony-forming units (CFU/mg of biofilm) and confocal laser scanning microscopy (CLSM), respectively. Group effects were compared with one-way ANOVA followed by a post hoc Tukey test (p<0.05).

Results: Both experimental varnishes completely inhibited the S. mutans biofilm formation after 24 h of exposure (CFU=0; p<0.05); whereas no significant decrease in the cells was observed for control varnish. The L. acidophilus was found to be susceptible to treatments as well, demonstrating a 3-log10 (CFU) statistically significant decrease in their viability after 24 h of exposure when compared to control (p<0.05; ANOVA/Tukey). The varnish 2 displayed the strongest activity against L. casei, with around 6-log reduction, when compared to varnish 1 (4-log) and control (p<0.05). CLSM images of the S. mutans, L. acidophilus and L. casei treated with experimental varnishes 1 and 2 confirmed that most of the cariogenic bacteria were dead in relation to the controls.
Conclusions: Natural compound-based varnishes are potential therapies for the inhibition of cariogenic biofilm formation.