Biomimetic rehabilitation of a structurally compromised endodontically treated tooth using deep margin elevation and polyethylene fiber–reinforced post and core: a case report

Background: Restoration of structurally compromised endodontically treated teeth with extensive coronal destruction and subgingival margins remains a significant restorative challenge. Contemporary biomimetic restorative approaches emphasize preservation of the remaining tooth structure through adhesive reinforcement strategies that improve biomechanical performance while minimizing additional radicular dentin removal. Case presentation: This case report describes the biomimetic rehabilitation of a previously root canal-treated maxillary canine with severe coronal destruction and subgingival palatal and proximal margins. Following laser gingivectomy and margin exposure, complete caries excavation was performed using caries detector dye guidance, followed by immediate dentin sealing using Prime & Bond NT (Dentsply DeTrey GmbH, Konstanz, Germany). Deep margin elevation was carried out using the doughnut technique with SDR Flow + Flowable Composite (Dentsply Sirona, Charlotte, NC, USA). Conservative post-space preparation was subsequently performed, and a polyethylene fiber-reinforced post and composite core buildup were completed using dual-cure resin cement under adhesive protocol. Definitive rehabilitation was achieved using a monolithic zirconia crown fabricated from Cercon XT zirconia (Dentsply Sirona, Bensheim, Germany), conditioned according to the APC (air-particle abrasion, primer application, and composite resin cementation) protocol prior to adhesive cementation. Outcome: Clinical and radiographic follow-up at one month demonstrated satisfactory esthetic and functional rehabilitation with healthy periodontal response, satisfactory marginal adaptation, and absence of clinical symptoms. Conclusion: Within the limitations of a single case report and short-term follow-up, polyethylene fiber-reinforced post and core systems combined with adhesive biomimetic restorative protocols such as immediate dentin sealing and deep margin elevation may represent a conservative treatment option for rehabilitation of structurally compromised endodontically treated teeth with compromised ferrule and subgingival defects.