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.

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The effects of trehalulose, a structural isomer of sucrose, and a syrup (TP syrup) rich in trehalulose and palatinose on caries development were examined in specific pathogen-free Sprague-Dawley rats. Streptococcus mutans MT8148R and Streptococcus sobrinus 6715 fermented the syrup which resulted in acid production, while both strains were found not to utilize trehalulose. Furthermore, trehalulose did not serve as a substrate for glucosyltransferases of these mutans streptococci to synthesize water-insoluble glucan, and it inhibited the sucrose-dependent adherence of mutans streptococci to a glass surface. Although trehalulose induced no significant dental caries in specific pathogen-free rats infected with either MT8148R or 6715, TP syrup was found to induce significant but low dental caries. Furthermore, replacement of the dietary sucrose content with trehalulose resulted in a significant reduction of caries development in rats infected with strain 6715.

The caries inhibitory activity of GOS-sugar (panose-and maltose-rich sugar mixture) was examined and compared with that of sucrose, maltose, or glucose in in vitro and in vivo experiments. Streptococcus mutans MT8148R (serotype c) and Streptococcus sobrinus 6715 (g) did ferment GOS-sugar and produce acid in a similar way as with maltose and glucose. However, GOS-sugar could not be a substrate for the glucosyltransferases (GTases) of these mutans streptococci to synthesize the water-insoluble glucan. Also, it significantly inhibited not only the synthesis of waterinsoluble glucan from sucrose by the crude GTases but also the sucrose-dependent adherence of these cells to a glass surface. In particular, adherence of growing cells of 6715 was markedly inhibited by the presence of GOS-sugar. GOS-sugar was found to induce significant but minimal dental caries in SPF rats infected with either MT8148R or 6715. Furthermore, the replacement of half of the dietary sucrose content with GOS-sugar resulted in a significant reduction of caries development in rats infected with strain 6715.