Tehran University of Medical Sciences Journal of Craniomaxillofacial Research 2345-5489 13 1 2026 05 12 123 128 Saeed Asgary Iranian Centre for Endodontic Research, Research Institute of Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 2026 01 05 2026 03 09 Intentional replantation (IR) is traditionally considered a last-resort procedure for teeth with an otherwise hopeless prognosis. Although advances in biomaterials have improved clinical outcomes, long-term evidence in teeth with combined periodontal–endodontic lesions (CPEL) and severe mobility remains limited. This case report describes a 12-year outcome of IR in a mandibular molar with a large CPEL, Grade III mobility, and persistent infection despite previous root canal therapy (RCT). A 45-year-old female presented with persistent pain and a draining sinus tract associated with tooth #36 one month after an RCT performed elsewhere. Clinical examination revealed Grade III mobility, probing depths >6 mm, bleeding on probing, and Class III furcation involvement. Radiography showed extensive periradicular and furcal radiolucency (PAI = 5). After obtaining written informed consent, an IR was performed. Atraumatic extraction was followed by root-end resection, retro-preparation using Gates-Glidden burs, and placement of calcium-enriched mixture (CEM) cement as a root-end filling material. The tooth was replanted within 9 minutes. No splinting was used. At two weeks, the infection had resolved, and mobility decreased to Grade II. Complete radiographic healing was observed at 3 years (PAI = 1). Probing depths normalized (<3 mm), mobility resolved (Grade 0), and no root resorption or ankylosis occurred. Follow-ups at 4, 5, 6, and 12 years confirmed long-term stability. At 12 years, recurrent coronal caries was restored with an amalgam crown featuring intra-orifice barriers. Periapical health, periodontal architecture, and function remained intact. This 12-year follow-up demonstrates that, when executed with strict biological principles and biomaterial selection, IR can achieve long-lasting success even in teeth with multiple negative prognostic indicators. The result highlights CEM cement as a biocompatible, bioactive root-end filling material that may promote periradicular healing in compromised conditions.  Keywords: Intentional replantation; Calcium silicate; Periodontal-endodontic lesion; Apical periodontitis; Root-end filling; Mineral trioxide aggregate; Long-term outcome. https://jcr.tums.ac.ir/index.php/jcr/article/view/616 https://jcr.tums.ac.ir/index.php/jcr/article/download/616/488