Prevalence and Anatomical Characteristics of C-Shaped Canals in Mandibular Molars in Chile: A Nationwide Multicentre Cross-Sectional Study.

This retrospective multicentre cross-sectional study aimed to determine the prevalence and characteristics of C-shaped canals in Chilean mandibular molars using cone-beam computed tomography (CBCT) and to assess associations with demographic and geographic variables. A total of 5660 mandibular molars from CBCT scans obtained from imaging centres across different regions of Chile were analysed. External root morphology was categorized according to root fusion, and C-shaped canals were classified using Fan's classification at five axial levels. The prevalence of C-shaped canals was 9.88%, with most cases occurring in mandibular second molars (93.92%) and bilateral occurrence observed in 53.87% of affected individuals. Their distribution differed significantly across geographic regions (p = 0.002). Regression analysis accounting for within-patient clustering showed that female sex was significantly associated with their presence (OR = 1.74), whereas age showed no significant association. All C-shaped canals showed root fusion. These findings provide population-specific data for improving diagnostic accuracy and endodontic treatment planning.