Aim: The aim of this study was to determine the frequency of C-shaped canals in mandibular second molars in a population in Saudi Arabia and to establish a classification for the most common configurations.
Methodology: One hundred and fifty-one mandibular second molars scheduled for root-canal treatment were examined over a 1-year period. The C-shaped canals were detected by radiographic and clinical examination. Teeth with C-shaped canal systems were categorized by using a modification of the classification of Melton.
Results: Of the 151 molars, 16 (10.6%) exhibited C-shaped canals. Five molars were classified as category I, and three were considered category II. The remaining eight cases were classified as category III, with two in subdivision I, two in subdivision II, and the remaining four in subdivision IIL.
Conclusions: The C-shaped canals in mandibular second molars vary considerably in their anatomical configuration with the result that debridement, obturation, and restoration may be difficult.