[Criteria for visual assessment of early periodontal disease on dental film. 1. Resorption of the crestal part of the alveolar bone].

A basic study was made to examine what extent of radiographic changes pertaining to early periodontal disease. The standardized radiography was used to assure geometrically identical radiographs. Artificial bone defects were produced by stages at the proximal bone crest using humane dry mandible. And as to when changes occurring in the bone on dental film can be recognized, visual assessment was made by the use of diagnostic accuracy curre and contrast measurement by means of microdensitometry. A study was also made as to whether the changes in the edge of the crestal cortical plate and the entire changes in the creastal part of the alveolar bone can be recognized by identiying them visually. The result showed that contrast of 0.03 was required to identify changes in the crestal part of the alveolar bone visually on dental film. However, it was difficult to discriminate the bony changes which occur in the edge of the crestal cortical plate from those on the lamina dura.