| OBJECTIVE: To investigate the effect of tea pigments on inhibiting the growth and acid production of mutans streptococci, morphological changes of S. mutans, and caries incidence of rats infected with Streptococcus sobrinus 6715.METHODS:Experiment One: Two strains of mutans streptococci, S. mutans Ingbritt and S. sobrinus 6715, were cultured in tryptic soy broth (TSB) medium containing 1% glucose. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of tea pigments containing 20%, 40% or 60% theaflavins and tea polyphenols containing 90% catechins for S. mutans were measured by twofold serial dilution. After S. mutans were cultured in TSB medium or in TSB medium with MIC of tea pigments of 40% theaflavins or tea polyphenols of 90% catechins at 37°C for 24 h, the pH values of the bacterial suspension were measured, respectively. After S. mutans were cultured in TSB medium or in TSB medium containing the half concentration of MIC of tea pigments of 40% theaflavins or tea polyphenols of 90% catechins at 37℃ for 24 h, they were centrifugated and washed three times by physiological saline. After S. mutans were fixed, dyed and embedded, the bacterial morphology were observed by transmission electronic microscope (TEM).Experiment Two: Thirty-six 21-day-old Sprague-Dawley (SD) rats were devidedrandomly into three groups (12 rats per group), fed with diet containing tetracycline (4 mg/g) and sterilized water containing penicillin G (4000 U/ml) for 3 consecutive days (from 21 to 23 days of age). All rats were inoculated with S. sobrinus 6715 once a day for 5 consecutive days (from 24 to 28 days of age), and fed with Caries-inducing diet 2000. Tea pigments containing 40% therflavins at the MIC concentration were given to wash the mouths of rats in group A once a day up to rat age of 89 days. After 20-second mouth wash, the rats were fasted for 30 minutes. The mouths of rats in group B were washed with tea polyphenols containing 90% catechins at the MIC concentration in the same way, while the mouths of rats in group C were washed with sterilized distilled water in the above-mentioned way. After all rats were raised to 89 days old, they were sacrificed for scoring caries of 12 molar teeth of each rat by Keyes' method. The data collected were analyzed with t tests and nonparametric tests in SPSS 11.5 version. RESULTS:Experiment One: Tea pigments of 40% theaflavins had the better inhibitory effect on the growth of S. mutans than tea pigments of 20% or 60% theaflavins, however, tea pigments (40%) had the similar inhibitory effect on the growth of S. mutans to the tea polyphenols of 90% catechins, with MIC and MBC of both being 2.5 mg/ml and 5.0 nag/ml respectively. Tea pigments (40%) and tea polyphenols (90%) could reduce acid production by S. mutans significantly (.PO.05). TEM findings revealed that tea pigments (40%) caused the vacuolar degeneration of cytoplasm of S. mutans, while tea polyphenols (90%) led to the destruction of cell membranes and abnormal shape of S. mutans.Experiment Two: Both tea pigment (40%) and tea polyphenols (90%) significantly reduced the incidence of enamel caries (E) and slight dentinal caries (Ds) of molar teeth of rats (PO.05), compared with the control group. However, moderate dentinal caries (Dm) occurred only in the control group, and no extensive dentinal caries (Dx)was found in all three groups.CONCLUSION: Tea pigments inhibited the growth and acid production of S. mutans by a synergistic action of the theaflavins with the other ingredients of tea pigments, and caused the vacuolar degeneration of cytoplasm of S. mutans. Tea pigments could reduce the incidence and severity of caries of SD rats. This study suggests that tea pigment may be used as a mouthrinse for caries prevention. |
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