[Effect of tea polyphenol on the demineralization and remineralization of enamel in vitro].

OBJECTIVE: To investigate the effect of tea polyphenol (TP) on the mineralization behaviour of enamel in two sterile, in vitro systems. METHODS: In the demineralization study, sound enamel sections were pH-cycled. Treatments were 2000 mg/L TP, 200 mg/L TP, 2000 mg/L TP + 100 mg/L fluoride, 100 mg/L fluoride, and deionized water. In the remineralization study, surface-softened enamel was used and pH-cycled as above. Test treatments were 2000 mg/L TP, 2000 mg/L TP + 250 mg/L fluoride, 250 mg/L fluoride, and deionized water. The acidic buffers were retained for calcium analysis. The enamel was analysed before and after pH-cycling by microhardness. RESULTS: In the demineralization study, the calcium depletion rates(CDR) were (0.43 +/- 0.05), (0.49 +/- 0.006), (0.21 +/- 0.02), (0.21 +/- 0.03) and (0.50 +/- 0.11) microgram/(mm2.h) respectively. The Knoop hardness values(KHV) percent reduction were 94.19 +/- 3.50, 96.62 +/- 0.63, 74.74 +/- 4.09, 77.79 +/- 3.11 and 97.32 +/- 4.03 respectively. There were no significant differences within either the TP-only groups or the fluoride groups, but the fluoride groups were significantly more efficacious than the TP-only groups (P < 0.05). In the remineralization study, the KHV percent increase were -11.96 +/- 10.1, -21.32 +/- 11.3, -49.52 +/- 24.6 and -4.24 +/- 8.51 respectively. Notably more remineralization was observed in the fluoride group. There were no significant differences between the other groups (P > 0.05). CONCLUSION: The data of this in vitro study suggest that TP has no effect on de/remineralization of enamel blocks and there is no synergetic action of TP and fluoride in a sterile system. This finding supports the proposition that tea polyphenols exert an anti-caries effect via an anti-microbial mode-of-action.