In vitro effect of fluoride-free mouthwashes on Streptococcus mutans biofilm

Objective: To evaluate the efficacy of commercially available, fluoride-free mouthwashes sold in Indianapolis, IN, on Streptococcus mutans biofilm. Materials and methods : Eighty-one different mouthwashes were purchased in Indianapolis, IN. A 24-hour culture of S. mutans UA159 was treated with the mouthwashes in three dilutions (1:3, 1:6, and 1:12), prepared in Tryptic Soy broth supplemented with 1% sucrose. The minimum inhibitory concentrations (MIC), planktonic, and biofilm growth were evaluated. In addition, the growth for minimum bactericidal concentration (MBC) was evaluated using five μL and incubated on blood agar. For the analysis of the results, the mouthwashes were separated into six groups according to their active ingredients (cetylpyridinium chloride/CPC, n=25; essential oils/EO n=10; whitening/W, n=12; Plant extracts, n=15; zinc chloride/ZC, n=3; others/O, n=16). ANOVA followed by the Tukey test was performed (p=0.05). Results: Regarding MIC, planktonic, and biofilm growth of S. mutans , there was a significant decrease for the W and CPC groups. The EO and W groups had more inhibition on S. mutans biofilm compared to the CPC group. For ZC, PE, and O groups, there were different effects within the same group, presenting a large variability. Conclusion: The mouthwashes demonstrated some effect on S. mutans biofilm, especially in the 1:3 dilution. W and CPC groups had a more significant effect on S. mutans biofilm. Clinical relevance: S. mutans is an important bacterium in dental caries and periodontal diseases. Our study showed that non-fluoridated mouthwashes affect the initial stages of biofilm formation.