This case report describes the endodontic treatment of a lower right second molar with a C-shaped root canal in a 49-year-old woman exhibiting severe loss of coronal structure. Clinical examination revealed a cavity with temporary filling on tooth 47, which tested negative to cold stimuli but was positive to percussion and bite tests. Cone beam computed tomography (CBCT) scan revealed a C-shaped canal morphology with associated periapical radiolucency, graded as CBCT-PAI score 4. The canal was classified as C3 subdivision III (Melton et al), C3 type II (Fan et al), and