Furcation involvement: comparison of dental radiographs and HR-CT-slices in human specimens.

In this in vitro study we compared dental radiographs and high resolution computed tomography (HR-CT) regarding identification and classification of the degree of horizontal and vertical furcation involvement. After removal of the soft tissue and metallic restorations of 18 dentate upper and lower jaws in the interradicular furcation region of 28 molars, bony defects of different dimensions were experimentally produced. The specimens were examined radiographically with standardized dental radiographs and 1.0 mm thick contiguous axial CT-scans. After identification of molars with artificial furcation involvement in the dental radiographs and axial CT-scans, the horizontal and vertical grades of furcation involvement were classified. Radiological identification and classification were compared with the macroscopic findings in the specimens. For quantitative histological-radiological comparison, corresponding microsections were prepared in the same plane as the axial CT-scans. In the dental radiographs the artificial furcation involvement in 6 of 28 (21%) molars was identified. In contrast, all 28 molars with involved furcations (100%) were identified in the axial CT-scans. The horizontal and vertical grades of furcation involvement were classified in the same way as the macroscopic findings, permitting comparison of histological sections and axial CT-scans. The HR-CT technique offers 3-dimensional assessment of the interradicular bone morphology in furcation involvement without overlying structures. The periradicular alveolar bone can be assessed on all sides of the roots. HR-CT scanning thus permits a high identification rate and classification of molars with involved furcations.