Bacteriologic evaluation of the efficacy of mechanical root canal instrumentation in endodontic therapy

Abstract

– The presence of bacteria in 15 single-rooted teeth, with periapical lesions, was studied throughout a whole period of treatment. The root canals were irrigated with physiologic saline solution during instrumentation. No antibacterial solutions or dressigs were used. Bacteria were found in all irnitial specimens form the teeth (median numver of bacterial cell 4x10⁵; range 10²-10⁷) and the number of strains in the specimens ranged from 1 to 10.88% of the strains were anaerobic. The most commonly isolated species were: Peptostreptococcus micros, Peptostrcptococcus anacrobius, Fusobacterium nucleatum, Bacteroides oralis, Bacteroides melaninogenicus subsp. intermedius and Eubacterium alactolyticum. Mechanical instrumentation reduced the number of bacteria considerably. Specimens taken at the beginning of each appointment usually contained 10⁴-10⁶ bacterial cells and at the end 10²-10³fewer. Bacteria were eliminated from the root canals of eight teeth during the treatment. In seven root canals bacteria presisted despite treatment on five successive occasions. There was no evidence that specific microorganisms were implicated in these persistent infections. Teeth where the infection persisted despite being treated five times were those with a hig number of bacteria in the initial sample.