Allogeneic Mesenchymal Stromal Cells Transplantation Induces Arrest of External Apical Inflammatory Resorption in a Mature Nonvital Traumatized Tooth

Introduction Mesenchymal stromal cells (MSCs) have been proposed for tissue regeneration based on their paracrine and immunomodulatory effects. Based on these features, MSCs may regulate inflammation and tissue repair. This case report assessed whether allogeneic bone marrow MSCs (BM-MSCs) can arrest external apical inflammatory resorption (EAIR) in a mature, nonvital traumatized tooth. Methods A healthy 14-year-old male with intermittent edema and a sinus tract associated with tooth #9 was referred for endodontic evaluation. Radiographically, tooth #9 showed EAIR with a vertical/diagonal mesial pattern and a 3-mm periapical lesion with widened periodontal ligament space. The root canal was cleaned and shaped; calcium hydroxide was used as interappointment medication, and cryopreserved allogeneic BM-MSCs were thawed, expanded, incorporated into preclotted platelet-rich plasma, and implanted into the pulp cavity. The cervical third was sealed with bioceramic cement and composite. Results Cryopreserved BM-MSCs retained fibroblast-like morphology, expressed CD73/CD90/CD105, and showed osteogenic, adipogenic, and chondrogenic differentiation. A BM-MSC/PRP clot was transplanted without complications or adverse events. At 3 months, radiographs showed reduction of the periapical radiolucency with initial bone formation and positive cold and electric pulp test responses. Between 12 and 24 months, reappearance of lamina dura, remodeling of the resorbed surface, and complete radiographic healing with arrest of EAIR were observed. At 48 months, tooth #9 was asymptomatic, responsive to cold and electric pulp test, and showed normal periapical architecture and mineralized tissue within the canal with an apical constriction. Conclusions BM-MSC transplantation may arrest EAIR and promote pulp-like and periapical tissue regeneration.