Diagnostic value of computed tomography in re-treatment of root fillings in maxillary molars

Aim To compare the diagnostic information and radiation dose between intraoral radiography and computed tomography (CT) in re-treatment decision making concerning root fillings in maxillary molars. Methodology Thirty-nine root-filled maxillary molars with suspected apical periodontitis were examined with two intraoral periapical radiographs and CT. Presence of periapical lesion/s per tooth and root were analysed for both techniques. In addition, in the CT images, the number of root canals, erosion, or perforation of cortical bone plates, and the distance between palatal root and cortical bone plates were evaluated. Radiation dose for CT was registered and calculated; and that of periapical radiographs used as reported previously (Ekestubbe et al. 2004). Results Periapical radiographs revealed periapical lesions in 33 teeth compared with 38 on CT images. A lesion of any root was detected more often with CT. The mesiobuccal root had two root canals in 30 teeth of which 27 of the MB2 canals were not filled, and 22 roots with an unfilled canal were associated a periapical lesion. Distances to palatal root, from the buccal and palatal cortex were measured in CT and varied between 5.0-12.0 mm and 0-4.0 mm, respectively. Based on the radiographic information, a variety of treatment alternatives were suggested. Mean effective dose of periapical radiographs was 0.02 mSv and that of CT 0.055 mSv. Conclusions Computed tomography may give important information in re-treatment decision when considering root fillings in maxillary molars. The radiation dose should be considered individually.