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.