Effect of different types of tea on Streptococcus mutans: An in vitro study

CONTEXT: If tea can be shown to have an inhibitory effect on the growth of Streptococcus mutans there can be a basis for using it as an agent for reducing caries. AIMS: The aim of the study was to determine the effect of aqueous and organic extracts of three types of tea (green, oolong, and black tea) on the growth of S. mutans. SETTINGS AND DESIGN: In vitro study. MATERIAL AND METHODS: Qualitative and quantitative phytochemical analysis of the three types of tea was done. Organic extracts of methanol and ethanol and aqueous extracts (50% and 100%) of tea were prepared. Fifty microliters of these extracts were inoculated into wells prepared on Mueller-Hinton agar plates that had been previously smeared with S. mutans. The agar plates were incubated at 37΀C for 24 hours. A similar procedure was followed using 0.2% chlorhexidine, which served as the positive control. STATISTICAL ANALYSIS USED: Analysis of variance (ANOVA), post hoc Tukey test, Student's 't ' test (two-tailed, dependent), and Student's 't' test (two-tailed, independent) were used for analysis of the data. RESULTS: All the phytochemicals were found to be higher in oolong tea. Both aqueous and organic extracts of oolong tea showed greatest zones of inhibition, followed by green tea and black tea. Aqueous extracts of oolong and green tea showed greater zone of inhibition than chlorhexidine. All the three types of tea inhibited growth of S. mutans. The greatest inhibition was observed with aqueous extract of oolong tea. CONCLUSIONS: Oolong tea extracts (aqueous and organic) showed a greater inhibitory effect on the growth of S. mutans than the other tea extracts .