Endodontic re-treatment of the mandibular first molar with six root canals: A case report.

Root canal anatomy of the mandibular first molar typically encompasses 3-4 canals. However, mandibular first molars may contain >4 root canals, emphasizing the need for heightened diligence among clinicians when conducting root canal therapy (RCT) on these teeth. Within the present case report, a 40-year-old Chinese female patient presented to The Third People's Hospital of Chengdu (Chengdu, China) in November 2023 with masticatory pain for 2 months in the lower right posterior region, after previous therapy at the People's Hospital of Wenjiang District (Sichuan, China) in July 2008. Examination using angulated radiographs and magnification instruments demonstrated six root canal systems in the mandibular first molar. Root canal re-treatment was performed and follow-up at 6 and 24 months was conducted following sealer extrusion. The patient was asymptomatic with decreased periapical radiolucency and area of extruded sealer. The present report highlights the importance of exploration and meticulous interpretation of canal morphology in the absence of advanced imaging techniques, also underscoring the efficient management of intricate root canal anatomy by conventional methods. By documenting this rare six-canal structure, the present report augments anatomical knowledge of mandibular first molars and reminds clinicians to anticipate unexpected variations during RCT.