Objectives: To study the effect of green tea extract on the hydroxyapatite bound glucosyltransferase activities and the dental plaque deposition. Methods: Green tea was extracted by ethanol, oven-dried and dissolved in ethanol to the tested concentrations. Glucosyltransferase from Streptococcus mutans ATCC 25175 was partially purified by ammonium sulfate, bound to saliva-coated hydroxyapatite and assayed using sucrose [glucose-14C] as a substrate. Various concentrations of green tea extract were tested for the effect on the enzyme activity. Tea extract, 0.05%, was chosen to prepare the mouthrinse for 9 subjects recruited from the third year dental students who are healthy and have at least 24 teeth. The subjects were asked to refrain from tooth brushing and tea and coffee drinking. On the first day, 10% of green tea extract was applied onto the teeth for 5 minutes and rinsed out. The subjects rinsed 100 ml of 0.05% green tea extract 9 times a day for 4 days, then plaque index (Quigley and Hein) was evaluated on the last day. For the control group, the subjects rinsed 100 ml of 0.2% ethanol instead. The washout period was at least 1 week. Wilcoxon signed-rank test was used to test the plaque index data. Results: It was found that glucosyltransferase activity was inhibited by green tea extract in dose dependence manner. The concentrations of 0.05% could inhibit about 40% glucosyltransferase activity and significantly reduced the deposition of plaque (p<0.05). Conclusion: Green tea extract could significantly inhibit the glucosyltransferase activity and plaque deposition.

(Dental Research Fund # 5/2003, Faculty of Dentistry, Chulalongkorn University)

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