Localization and identification of root canal bacteria in clinically asymptomatic periapical pathosis.

Twenty-one teeth with clinically asymptomatic periapical pathosis (class 3) were extracted and the isolation, identification, and localization of bacteria in the root apex were examined. Mixtures involving several bacteria were isolated from more than 60% of the cases. Scanning electron microscopy revealed bacterial masses to be associated with the apical part of the root canal, but not with the area of apical foramen or on the surface of root apex. Our results indicate that the bacteria in class 3 cases may be derived from organisms which colonized before or during endodontic treatment, but not from anachoresis. The bacteria-positive cases of asymptomatic periapical pathosis have the potential to progress to symptomatic periapical pathosis.