[Confidence region of alveolar bone level on xeroradiography].

Dental radiographs can be important for examination, evaluation and diagnosis of periodontal disease, and they have been widely used by dentists. However, discrepancies between radiographs and existing clinical periodontal tissue have been found. The purpose of this study was to investigate the relationship between the existing alveolar bone level on a Xeroradiograph and the root surface area covered with a periodontal ligament. Alveolar bone blocks from human skulls (total 34 teeth) and 60 patients (total 165 teeth) were used for this study. Each human skull bone block was taken Xeroradiograph under three types of conditions. 165 teeth from patients with severe periodontal disease were taken Xeroradiograph by a parallel method. The following equation was used for measuring the teeth on the Xeroradiograph. alpha = Root area supporting the existing alveolar bone/Root area from periapical to C-E junction x 100 The root surface area of each of the teeth extracted from bone blocks and of the extracted teeth from patients were measured by the membrane technique and calculated as follows: beta = Root surface area covered with periodontal ligament/Root surface area x 100 There was no significant difference in equation alpha calculated on three types of Xeroradiographs in the human skull. Significant positive correlations between alpha and beta were obtained, and an empirical regression line was constructed to estimate the ratio of the root surface area covered with periodontal ligament from the existing alveolar bone level on the Xeroradiograph. The results suggest that the ratio of the area of periodontal ligament to the root surface area given by these methods provides useful data for examination, diagnosis and evaluation of periodontal disease.