Inflammatory external root resorption (IERR) requires damage or loss of the protective layer and an inflammatory process in the unprotected root surface. Infection of the pulp space can occur after a serious injury and stimulate an inflammatory response. When the inflammatory stimulus is long-standing, the destructive phase will continue until the stimulation is removed.This article describes the use of cone-beam computed tomography scanning in the diagnosis and management of a perforating IERR in tooth #10 with a 17-month follow-up and histologic examination after extraction for orthodontic reasons.The histologic examination showed a cementum-like tissue interposed within the dentin defect. The cementum-like tissue was eosinophilic and irregular or poorly demarcated in some parts. Fibrous ligament tissue and no inflammatory response could be identified.Mineral trioxide aggregate was shown to be suitable for the treatment of perforating IERR, and this finding agrees with the results observed in different studies conducted with animals.