The prevalence and distribution of intrabony defects in dry mandibles.

One hundred mandibles of South African Negroes were examined for the presence of intrabony defects, and the distance between the cemento-enamel junction and alveolar bone crest was measured along the buccal and lingual surface of roots associated with interdental craters. Two-hundred thirty-one intrabony defects were detected (4.1% of the possible occurrences). There were 51 craters, 19 of which were associated with the distal surfaces of the second molars. Most craters (84.3%) had higher lingual than buccal walls. Seventy-one defects (35.8%) were one-walled pockets, 98 defects (49.6%) were two-walled pockets and 30 (15%) were three-walled pockets. Twenty-eight one-walled pockets (39.4%) formed hemisepta against interproximal root surfaces. Mesial surfaces of canines were the most commonly involved with hemisepta. There was an increase in the frequency of intrabony pockets from the anterior to the posterior zones of the mandibles. Interproximal root surfaces were by far more commonly associated with defects than buccal or lingual surfaces.