Antimicrobial and Synergistic Effects of Garlic and Cinnamon Extract Compared with Fluoride Varnish on Oral Lactobacillus acidophilus and Streptococcus mutans in Laboratory Conditions

Background and purpose: Garlic and cinnamon extracts, like fluoride varnish, play a role in caries control due to their antimicrobial effect and controlling demineralization. This analytical laboratory study was conducted in 2021 to investigate the antimicrobial effect of garlic and cinnamon extracts compared with fluoride varnish in controlling the infection of oral Lactobacillus acidophilus and Streptococcus mutans. Materials and methods: The disk diffusion, minimum inhibitory concentration and the minimum bactericidal concentration tests were used to check the antimicrobial effect. Ampicillin and Erythromycin discs were used for positive control and sterile physiological serum was used for negative control. Data were analyzed using analysis of variance (ANOVA) and Bonferroni post hoc test. Results: In disk diffusion test, cinnamon along with fluoride varnish (10.0±1.0mm) caused a significant increase in the diameter of the growth inhibition halo of L. acidophilus (P<0.001), However, the largest growth inhibition halo diameters in L. acidophilus and S. mutans were associated with garlic-cinnamon-varnish (12.0±1.58mm) and fluoride varnish (9.0±0.71mm), respectively. In both strains, the antimicrobial effect of garlic extract was significantly lower than other compounds (P<0.001). The most inhibitory and bactericidal effects were associated with fluoride varnish seen in S. mutans. Conclusion: According to this study, cinnamon and fluoride varnish has a synergistic antimicrobial effect against L. acidophilus in laboratory conditions. Also, cinnamon extract due to similar effects to fluoride varnish, can be useful as an alternative agent in controlling and preventing dental caries.