Microbiologic analysis of teeth with failed endodontic treatment and the outcome of conservative re-treatment

Objective, The purposes of this study were to determine what microbial flora were present in teeth after failed root canal therapy and to establish the outcome of conservative re-treatment. Study design. Fifty-four root-filled teeth with persisting periapical lesions were selected for re-treatment. After removal of the root filling, canals were sampled by means of advanced microbiologic techniques, The teeth were then re-treated and followed for up to 5 years. Results. The microbial flora was mainly single species of predominantly gram-positive organisms. The isolates most commonly recovered were bacteria of the species Enterococcus faecalis. The overall success rate of re-treatment was 74%. Conclusions. The microbial flora in canals after failed endodontic therapy differed markedly from the flora in untreated teeth. infection at the time of root filling and size of the periapical lesion were factors that had a negative influence on the prognosis. Three of Four endodontic failures were successfully managed by re-treatment.