An extract of oolong tea (semifermented tea leaves of Camellia sinensis) and its chromatographically isolated polyphenolic compound was examined for in vitro inhibitory effects on glucosyltransferases (GTases) of mutans streptococci and on caries development in Sprague-Dawley rats infected with mutans streptococci. The samples showed no detectable effect on the growth of mutans streptococci. However, insoluble glucan synthesis from sucrose by the GTases of Streptococcus mutans MT8148R and Streptococcus sobrinus 6715 was markedly inhibited, as was sucrose-dependent cell adherence of these mutans streptococci. The administration of the oolong tea extract and the isolated polyphenol compound into diet 2000 and drinking water resulted in significant reductions in caries development and plaque accumulation in the rats infected with mutans streptococci. The active components in the oolong tea extract were presumptively identified as polymeric polyphenols which were specific for oolong tea leaves. These results indicate that the oolong tea polyphenolic compounds could be useful for controlling dental caries.

The inhibitory effect of oolong tea extract (OTE) containing polymerized polyphenols on plaque deposition was examined in 35 human volunteers. Thirty-five human volunteers, aged 18-29 years, who received extensive oral prophylactic procedures were requested to refrain from all oral hygiene procedures for 4 days, and to rinse their mouth with 0.5 mg/ml OTE solution in 0.2% ethanol before and after every intake of food and before sleeping at night. No restriction regarding meals was given during the test period, except to refrain from teas or coffee. Plaque deposition was evaluated after disclosing the teeth with Erythrocin at the termination of this experiment. The study was repeated 1 week after the first trial, but only 0.2% ethanol without OTE was used for mouthrinsing in the second trial. OTE was found to significantly inhibit plaque deposition in volunteers, although mouthrinsing with OTE solution had no significant effect on the number of mutans streptococci in unstimulated whole saliva.

Xerostomia is a serious side-effect of radiotherapy for head and neck cancer and often enhances caries activity. However, the relationship between caries induction and the IgA level in saliva in rats subjected to irradiation of the salivary glands is unclear. The effect of salivary gland irradiation on salivary function was examined in specific pathogen-free Sprague-Dawley rats infected with or without Streptococcus mutans MT8148R (serotype c). The flow rate of saliva and the protein concentration in saliva were significantly reduced in irradiated rats, regardless of infection of S. mutans. The caries activity was enhanced in these rats, and and irradiation level of 50 Gy significantly increased the caries score. However, longitudinal study indicated that the salivary concentration of IgA reactive with S. mutans whole cells maintained similar or significantly higher levels in irradiated rats, when compared with those of nonirradiated rats. In addition, there was no negative correlation between the caries score and the salivary concentration of IgA reactive with S. mutans. These findings suggest that the secreted IgA against S. mutans may not play a significant role in the caries induction of hyposalivated rats.

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The effects of hyposalivation on the induction of dental caries and the change in oral microflora were examined at weekly intervals in Sprague-Dawley