Assessment of periradicular microbiota by DNA-DNA hybridization

In the present study the "checkerboard" DNA-DNA hybridization technique was used to identify bacteria in periapical endodontic lesions of asymptomatic teeth. Thirty-four patients with root-filled teeth and apical periodontiti s were divided into two groups, each containing 17 patients. In Group 1, a marginal incision was performed during surgery to expose the lesion, and in Group 2, a submarginal incision was applied. The gingiva and mucosa were s wabbed with an 0.2% chlorhexidine gluconate solution prior to surgery. Bact erial DNA was identified in all samples from the two groups using 40 differ ent whole genomic probes. The mean number (+/-SD) of species detected was 3 3.7+/-3.3 in Group 1 and 21.3+/-6.3 in Group 2 (P<0.001). The majority of t he probedetected bacteria were present in more lesions from Group1 than fro m Group 2. The differences were most notable for Campylobacter gracilis, Po rphyromonas endodontalis, Propionibacterium acnes, Capnocytophaga gingivali s, Fusobacterium nucleatum ssp. nucleatum, Fusobacterium nucleatum ssp. pol ymorphum, Prevotella intermedin, Treponema denticola, Streptococcus constel latus and Actinomyces naeslundii I. Bacterial species such as Actinobacillu s actinomycetemcomitans and Bacteroides forsythus were detected in more tha n 60% of the lesions from both groups. Also, 1;1 endodontalis was abundant in periapical tissue. The data supported the idea that following a marginal incision, bacteria from the periodontal pocket might reach the underlying tissues by surgeon-released bacteremia. The study provided solid evidence t hat bacteria invade the periapical tissue of asymptomatic teeth with apical periodontitis. The detection of much more bacteria with the "checkerboard" DNA-DNA hybridization method than has previously been recovered by anaerob ic culture indicated that the endodontic land periodontal) microfloras shou ld be redefined using molecular methods.