Inhibitory effects of oolong tea extract on caries-inducing properties of mutans streptococci

The inhibitory effects of oolong tea extract (OTE) on the caries-inducing p roperties of mutans streptococci were examined in vitro. OTE reduced the ra te of acid production by mutans streptococci accompanied with the retardati on of growth rate of mutans streptococci, while the action by chromatograph ically isolated oolong tea polyphenol (OTF6) was weak. On the other hand, b oth oolong tea products decreased cell surface hydrophobicity of almost all the oral streptococci examined in the present study, and also induced cell ular aggregation of Streptococcus mutans, Streptococcus oralis, Streptococc us sanguis or Streptococcus gordonii, In these reactions, OTF6 showed a mor e pronounced activity than OTE, Furthermore, the oolong tea products inhibi ted the adherence of mutans streptococci to saliva-coated hydroxyapatite, T hese results suggest that OTF6 may inhibit bacterial adherence to the tooth surfaces by reducing the hydrophobicity of mutans streptococci, and OTE ma y inhibit caries-inducing activity of mutans streptococci by reducing the r ate of acid production.