Tooth resorption results from injuries to or irritation of the periodontal ligament and/or pulp. It may arise as a sequalae of traumatic luxation injuries, orthodontic tooth movement, or chronic infections of the pulp or periodontal structures. In extensive traumatic injuries, healing does not take place by the adjacent vital cells and the bone can establish a contact with the root surface, making the tooth an essential part of the bone remodelling system. This phenomenon is termed as dento-alveolar ankylosis. Resorption can occur without any further stimulation and this activity involves osteoclastic resorption dependent on parathyroid-hormone-generated resorption and bacterial invasion. Such teeth elicit a high metallic sound on percussion; on continuous resorptive attacks, the teeth become infra-occluded. Successful management of resorption cannot always be a predicted. However, an experimental approach to manage the initial stage of inflammatory response is to decrease the formation of clastic cells, and to induce repair of damaged root surfaces by cementoblasts. The purpose of this case report wass to review this entity, to discuss factors that influence the occurrence of resorption, and to describe appropriate treatment. A case of external replacement resorption is presented, illustrating previous root canal therapy. After a meticulous diagnosis, a stringent treatment plan was executed. A nonsurgical endodontic therapy was performed with the use of calcium hydroxide as an intracanal medicament. 2% chlorhexidine was used as a final irrigant. A 3-months followup radiograph revealed adequate control of replacement resorption and the tooth was obturated. Subsequent followup showed a perceptible halt in the dento-alveolar ankylosis.