The paper presents a case report of a 52-year-old female patient who was admitted to the clinic with pain in tooth 47, which had previously undergone endodontic treatment at another dental office. Radiographic examination revealed inadequate primary root canal therapy, including insufficient preparation and obturation of the mesial root canals, as well as a periapical radiolucency. During retreatment planning, the possibility of anatomic variations typical of mandibular second molars–specifically the presence of type C canals–was taken into consideration. This article highlights the diagnostic and technical challenges associated with retreating a tooth that presents with a complex and atypical root canal morphology.

Key words: C-shaped canals, endodontic retreatment, complications.