Combinations of bacterial species in endodontic infections

Aim This study was undertaken to investigate combinations of bacteria found in root-canal infections of teeth with periapical bone destruction without clinical signs and symptoms. Methodology Endodontic samples from 58 root canals were cultured anaerobically and microorganisms were counted and identified. Eighty-one combinations of microorganisms were found and tested for a symbiotic relationship using the Fisher's exact test and Odds ratio calculation. Results All samples contained microorganisms with a median CFU mL(-1) of 8 x 10(4) per sample. Strict anaerobic species accounted for 87% of the microflora. The most prevalent bacteria were Prevotella intermedia , Peptostreptococcus micros and Actinomyces odontolyticus , present in 33, 29 and 19%, respectively, of the cultured canals. A significant relationship (P < 0.05) and an Odds ratio >2 were found between P. intermedia and P. micros , P. intermedia and P. oralis, A. odontolyticus and P. micros , Bifidobacterium spp. and Veillonella spp. Conclusions These results indicate that endodontic pathogens do not occur at random but are found in specific combinations.