Dominant prevalence of types I and IV in healthy Japanese children.

Background/purpose: is a major causative agent of chronic periodontitis, whilst circumstances for acquisition of the bacterium remain to be elucidated. To examine prevalence of the bacterium harboring distinct types in dental plaque of children, we established PCR procedures that are applicable for specimens with limited amounts. By this method, all six types including type I and Ib were directly identified, and prevalence of types and their frequency of guardian-child transmission in Japanese children were assessed.