Background : Streptococcus mutans is a major cause of dental caries and tooth damage. The purpose of this study was to evaluate the effect of the Stevioside and Stevia rebaudiana leaf extracts on the growth of Streptococcus mutans. Materials and Methods: In this study, the aqueous and acetone extracts of Stevia rebaudiana were extracted by the maceration method, and methanol and ethanol extracts were prepared by a Soxhlet apparatus. Stevioside was purchased from Malaysia. The agar-well diffusion method was used to determine the antibacterial activity of Stevioside and Stevia extracts. Minimal Inhibitory Concentration (MIC) was determined by the microdilution method. The antibacterial effects of Stevioside and Stevia extracts together and in combination with Penicillin were compared through variance analysis. Results: The results indicated the inhibitory effects of methanol extracts at MIC= 25 mg/ml, ethanol extract at MIC=3.13 mg/ml, and acetone extract at MIC=1.56 mg/ml on growth of Streptococcus mutans. The aqueous extract of Stevia rebaudiana and Stevioside could not inhibit the growth of Streptococcus mutans. Conclusion: The alcoholic and acetone extracts of Stevia rebaudiana may be used as pharmaceuticals and preservatives in controlling the growth of Streptococcus mutans.

Keywords: Stevia rebaudiana, Stevioside, Streptococcus mutans, Antibacterial activity.

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