Association of Canal Continuity and Branching Patterns on Orthopantomography with Complex Anatomy Detected by Cone-Beam Computed Tomography in Mandibular Premolars

Early radiographic identification of morphological variations may help reduce the risk of treatment failure. This retrospective study investigated the associations between canal continuity and branching patterns observed on digital orthopantomographs (OPTs) of mandibular premolars and complex canal (CC) configurations, C-shaped canals, and radicular grooves (RGs) identified on cone-beam computed tomography (CBCT) images of the corresponding teeth. A total of 1381 mandibular premolars were classified on OPT into two main categories: Group 1, based on canal continuity and interruption patterns, and Group 2, based on canal or root branching features. Group 1 (A–D) was categorized according to the level of canal interruption, whereas Group 2 (A–C) was classified by root and canal branching characteristics. Group 1A (apical third interruption) was most prevalent (82.33%), followed by Group 1B (middle third interruption, 14.63%). Compared with Group 1A, all other groups showed significantly higher prevalence of CCs, C-shaped canals, and RGs (p < 0.001). Canal interruption in the middle or coronal third and canal or root branching patterns on OPT were associated with more complex morphological findings on CBCT. These OPT patterns may serve as radiographic warning signs and support individualized consideration of CBCT when conventional assessment remains inconclusive.