Nonsurgical endodontic retreatment of a mandibular first molar with five canals: 1-year follow-up.

Mandibular first molars have highly variable root canal morphology. According to previous studies, the occurrence of middle mesial canals ranges from 1% to 15%. In this case, nonsurgical endodontic retreatment of a mandibular first molar with a middle mesial canal is attempted. The authors describe the diagnosis and clinical management of a mandibular first molar with three mesial root canals, drawing particular attention to radiographic interpretation and access refinements.