Predicting the configuration of a C-shaped canal system from panoramic radiographs

Objective. To characterize the presentation of C-shaped canals in mandibular molars on dental panoramic radiographs. Study design. The sample consisted of 290 patients who had undergone both panoramic dental radiography and computed tomography (CT). Initially the presence of mandibular molars with C-shaped canals was identified on this sample by the use CT. This was used as a ground radiographic truth. Then 3 investigators independently classified the mandibular molars according to their 6 root morphologies on panoramic dental radiographs. The sensitivities, specificities, positive predictive values (PPV), and negative predictive values (NPV) of characteristic findings on panoramic radiographs were calculated. Results. A C-shaped canal was identified in 90 (29%) of 311 mandibular molars. The most common morphology of C-shaped canal molars was 2 separate conical roots (52%); trabecular patterns were relatively common between the roots. In contrast, the most common morphology of molars without C-shaped canals was 2 separate roots that were either divergent or parallel (85%). Conclusion. Panoramic radiography is a good surveying modality to detect C-shaped canals and can be used to determine whether further examination is required before endodontic treatment. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:e37-e41)