Presumed Idiopathic Replacement Resorption in a Permanent First Molar in a Child With Multiple Tooth Agenesis: A Case Report.

Replacement resorption is a rare pathological condition in permanent teeth, characterized by progressive substitution of root dentin with bone tissue, typically following traumatic injuries. This case report presents an unusual occurrence of replacement resorption in the mesial root of the mandibular right first permanent molar (46) in an eight-year-old boy with no documented history of trauma, associated with non-syndromic agenesis of multiple permanent teeth (15, 34, 35, 44, 45). Despite the reserved long-term prognosis, conservative endodontic management was pursued due to the significant tooth agenesis. This case highlights the importance of advanced imaging in diagnosis, the challenges of managing replacement resorption, and the potential for successful conservative treatment when appropriate protocols are followed.