Comparison of Antimicrobial Activity of Fluoride Varnishes Against Streptococcus mutans and Lactobacillus acidophilus: An In Vitro Study

Background: Topical fluoride products such as varnishes prevent dental caries by limiting demineralization and antibacterial properties. The structural and metabolic characteristics of cariogenic microorganisms are different from each other. Also, the formulation properties, concentration, and release behavior of fluoride vary in different varnishes. Objectives: In this study, we investigated the antibacterial effects of three types of common fluoride varnishes against two cariogenic bacteria of Streptococcus mutans (S.M.) and Lactobacillus acidophilus (L.A.). Methods: In this in vitro study, antibacterial effects of MI varnish [containing calcium phosphopeptide-amorphous calcium phosphate (CPP-ACP)], Polimo (containing xylitol), and FluoroDose varnishes were evaluated using disc diffusion method via measuring the diameter of the inhibition zone. The antibiotics of erythromycin and ampicillin were used as the positive control of the test. Analysis of variance (ANOVA) and post hoc tests were applied to compare the mean of non-growth zone diameter in the studied groups. Data were analyzed by SPSS 16. The statistical significance level was determined as P-value 0.05. Results: The antibacterial effect of each varnish was optimal against both bacteria. In comparison, the mean diameter of the inhibition zone inMIvarnish was significantly (P-value=0.019) higher than PolimoandFluoroDose brandsonS.M.; however, this difference was not statistically significant for L.A. Furthermore, Polimo and FluoroDose varnishes showed similar antimicrobial effects against these bacteria. Conclusions: The use of these varnishes seems to be suitable for preventing tooth decay. MI varnish is preferable because of its higher antibacterial properties.