Surgical Management of a Separated Instrument and Radicular Cyst: A Nine-Month Cone Beam Computed Tomography (CBCT) Follow-up

Large periapical lesions complicated by fractured instruments present a significant endodontic challenge. When such teeth serve as abutments in a fixed partial denture (FPD), orthograde retreatment may be impractical. Surgical endodontics, aided by bioactive and regenerative materials, can offer a predictable, conservative alternative. This case report highlights a middle-aged patient who presented with dull pain and intermittent pus discharge in relation to tooth #21, previously root canal treated and restored under an 8-unit FPD (teeth #15-23). Cone-beam computed tomography (CBCT) revealed a periapical lesion (measuring 13.7 × 12.8 × 14.8 mm) with labial cortical discontinuity and a 4.7-mm separated apical fragment. Because post removal and prosthesis dismantling were neither feasible nor cost-effective, a surgical approach using a Luebke-Oschenbein limited-thickness mucoperiosteal flap was adopted. The procedure included cyst enucleation, instrument retrieval, apicoectomy with ultrasonic retropreparation, retro-sealing with Biodentine, and guided bone regeneration with advanced platelet-rich fibrin (APRF) and allograft. CBCT follow-up at six months and nine months showed progressive bone fill and graft consolidation. In conclusion, in prosthetically constrained cases, microsurgical endodontic management using bioactive and regenerative materials can predictably resolve pathology while preserving existing restorations.