Abstract
A man in his mid-50s with stage III periodontitis underwent a structured, multiphase treatment. Following the initial therapy that achieved periodontal stability (evidenced by improved clinical parameters), orthodontic treatment with strategic extractions was performed. Unexpectedly, a severe endoperiodontal lesion subsequently developed in the left maxillary canine. Cone-beam CT confirmed extensive circumferential bone resorption. After endodontic therapy, periodontal regenerative therapy using enamel matrix derivative and bovine bone graft was performed. Six months post-surgery, the probing pocket depth improved from 6 mm to 3 mm, with no bleeding on probing, and radiographs showed improved radiopacity. A 2.5-year follow-up demonstrated a stable periodontal condition. This case underscores that late-stage complications can arise even with thorough evidence-based therapy. This highlights the importance of proactive monitoring and demonstrates the potential for successful regeneration of severe bone defects.