A bacteriological and histological evaluation of 58 periapical lesions.

Periapical tissue from 58 cases requiring periapical surgery was examined histologically and cultured for the presence of microbes. Twenty-nine had a possible oral cavity communication and 29 did not. Approximately one-half of each biopsy was submitted for culture while the other portion was examined histologically. Cultures were positive for the presence of bacteria in 51 of 58 cases while bacteria were seen histologically in only 8 of 58 cases. A total of 50 different species of bacteria were isolated from the 58 cultures of periapical tissue. Of 133 isolates, 87 were strict anaerobes, 37 were facultative anaerobes, and 9 were aerobes. Bacteroides species were found in 17 cultures, always with additional bacteria. Seventeen of 58 biopsies contained foreign particulate matter thought to be root canal sealer. Bacteria were found in periapical granulomas, radicular cysts, and a periapical abscess. According to our data, bacteria, foreign material, missed canals, vertical root fractures, and periodontal disease may all contribute to the chronic, non-healing periradicular lesion.