Sten Persson

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.

Catalase inhibitiob by sulfide and hydrogen peroxide-induced mutagenicity in Salmonella typhimurium strain TA102

The lethal and mutagenic effects of hydrogen peroxide were studied in exponentially growing cultures of Salmonella typhimurium strain TA102. Exposure of the cultures to non-lethal levels of sodium sulfide significantly increased the lethality and mutagenicity of hydrogen peroxide. The catalase activity was decreased in cells exposed to sodium sulfide, but there were no changes in the cellular levels of superoxide dismutase, glutathione reductase, or NADPH-dependent alkyl hydroperoxide reductase. Hydrogen peroxide-induced mutagenesis and killing of S. typhimurium strain TA102 in the presence of sulfide may in part be explained by an inactivation of catalase by sulfide.