Comparative evaluation of the antimicrobial activity of three tea extracts against chlorhexidine, chlorine dioxide, and cariogenic bacteria: An in vitro study

Abstract Background: Tea derived from Camellia sinensis contains several bioactive compounds with documented antimicrobial potential. Differences in the degree of fermentation among green, black, and oolong tea may influence their antimicrobial efficacy against cariogenic microorganisms. Aim: To compare and evaluate the anticariogenic activity of aqueous and ethanol extracts of green tea, black tea, and oolong tea with 0.2% chlorhexidine and 0.1% chlorine dioxide against Streptococcus mutans, Streptococcus oralis , and Lactobacillus acidophilus . Materials and Methods: About 50 μL of aqueous and ethanol tea extracts, along with chlorhexidine and chlorine dioxide, were inoculated into wells prepared on agar plates smeared with the test microorganisms. Plates were incubated at 37°C for 24 h, after which the diameter of the zone of inhibition was measured. Statistical analysis was performed using the one-way ANOVA followed by Tukey’s post hoc test. Results: Aqueous oolong tea extract demonstrated the highest antimicrobial activity against all three microorganisms, followed by chlorhexidine, green tea, black tea, and chlorine dioxide. Ethanol extracts showed comparatively lower antimicrobial activity; however, oolong tea remained the most effective. The differences between aqueous and ethanol extracts were statistically significant ( P < 0.05). Conclusion: Aqueous tea extracts exhibited superior antimicrobial activity compared to ethanol extracts. Oolong tea showed greater anticariogenic potential than chlorhexidine, suggesting its possible role as a natural adjunct in caries prevention.