Reliability of Dental X-ray Photography Compared with Micro-focus X-ray CT Imaging of Root Canal Morphology

Abstract

Dental X-ray photography is the most conventional and useful method for acquiring essential information on root canal morphology. However, due to restrictions on the direction of X-ray projection, traditional intraoral radiography cannot provide complete information on root canal morphology in situ. Recently, micro-focus X-ray computed tomography (CT) is considered useful for 3-D visualization of details of the pulp cavity. In order to evaluate the reliability of conventional dental X-ray photography compared with the results obtained by micro-focus X-ray CT imaging, we assessed the accuracy of conventional (orthoradial and eccentric projections) dental radiograms obtained from 14 extracted mandibular 1st molars in relation to micro-focus CT images of the same teeth. The results were as follows: (1) The number of root canals detected by conventional dental radiography was 75.0-87.5%, which was consistent with that shown in the CT images. Dental film images detected apical ramifications with low accuracy, while ramifications were clearly demonstrated by the CT images. (2) Orthoradial projection images of root bifurcation were 25.0-75.0% consistent with the CT images. With the eccentric projection technique, the consistency further decreased to 25.0-42.9%. (3) Orthoradial dental films detected denticles 4.5-10.7% consistent with the CT images. Eccentric-projection films showed overlapping images which decreased the consistency with the CT images. (4) The eccentric projection images provided more information than the orthoradial projection images, while showing a decrease in the consistency of the distal root canal (in particular, that containing denticles) with the 3D-CT imaging. The present 3D-CT imaging conducted on molars suggests that dental X-ray photography provides reasonable general information on root canals and bifurcations, but that it is difficult to identify details of the pulp cavity (in particular, that containing denticles) with a complex system of reticular root canal and apical ramifications.