Cultivable microbial flora associated with persistent periapical disease and coronal leakage after root canal treatment: a preliminary study

Aim To identify the cultivable bacterial flora in root filled teeth with persistent periapical lesions and to locate their distribution within the root canal system using an in vitro sampling protocol. Methodology Eight freshly extracted root filled teeth were collected from the Oral and Maxillo-facial Surgery Department, Eastman Dental Hospital. Seven teeth were associated with persistent apical periodontitis and also showed evidence of coronal leakage. Teeth were transferred to an anaerobic chamber immediately after careful extraction and sectioned transversely to give a crown (in all but one case) and two root segments (coronal and apical). Two samples were obtained from each segment, one from dentine and the other from the restoration or gutta-percha (GP) root filling (46 sites in total). The samples were dispersed, serially diluted and Cultured on blood agar and fastidious anaerobic agar (with 5%, defibrinated horse blood). The primary growth was subcultured to obtain pure isolates, which were identified by routine microbiological techniques and commercial enzyme tests. Results A total of 252 strains were isolated from all the teeth. Of all the isolates, the most prevalent bacteria were Gram-positive facultative anaerobes 189/252 (75%) with staphylococci (48/252, 19%), streptococci (44/252, 17%), enterococci (20/252, 8%) and Actinomyces species (20/252, 8%) being found in most of the teeth (6/8, 6/8, 5/8, 5/8 and 7/8, respectively). Of the obligate anaerobes (17%), peptostreptococci (7%) were also present in most teeth (7/8). A statistical association between bacterial flora and site (crown/ coronal/apical) or surface (dental/GP/restoration) could not be shown. Conclusions The predominant group of bacteria in root filled teeth with persistent apical periodontitis and coronal leakage was Gram-positive facultative anaerobes of which staphylococci followed by streptococci and enterococci were the most prevalent.