Extensive external localized idiopathic root resorption – An unusual case report

External root resorption of permanent teeth is a multifactorial process. This article presents an unusual case of localized idiopathic extensive external root resorption involving the whole mesial root of the right mandibular first molar in a 42-year-old female patient. No significant systemic, dental, or familial findings could be identified as a possible cause. The cause of the resorption remained unclear. The tooth was managed by nonsurgical endodontic treatment using mineral trioxide aggregate to seal resorbed canals. A 5-year follow-up revealed satisfactory results clinically and radiographically with mobility within physiological limits.