STUDY ON A METHOD FOR MAPPING THE DISTRIBUTION PATTERN OF CARIOGENIC BACTERIA WITHIN DENTAL PLAQUE in vivo USING REAL-TIME PCR

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(1)A new method was developed to map the distribution of cariogenic oral streptococci, S.mutans and S.sobrinus, from the outermost to the innermost plaque. The distribution patterns of fractions positive for S.mutans and S. sobrinus varied among the subjects, with a tendency for frequent detection of both species in the outer to middle layers of dental plaque. There were no plaque fractions in which only S.sobrinus was found. This method could be useful to map the distribution of cariogenic microorganisms and to estimate the bacterial ecology for oral biofilm.(2)The antimicrobial effect of SnF_2 gel treatment on dental plaque in vivo was evaluated, using this new method which detects presence of cariogenic streptococci. The results showed that frequencies of layer containing 」 mutans and S.sobrinus were 80% and 37% before, and 94% and 79% after the treatment, respectively, indicating that, contrary to our expectations. the treatment made their habitat in plaque significantly wider.(3)Bacterial density within plaque was analyzed by a quantitative real-time PCR to assess the antimicrobial effect of SnF_2 gel treatment on dental plaque. The density before the treatment peaked close to the outer surface, promptly deceasing towards the interior. However, post treatment levels significantly increased, showing 1010^2 times higher in the outer regions and 10^2-10^3 times higher in the inner regions. Plaque volumes demonstrated a tendency to reduce after the treatment. The results suggested that the application of SnF_2 gel may indeed increase the porosity of plaque, creating a larger habitat for bacteria particularly in deeper regions.