Tooth #9 (upper left central) had root canal treatment. A draining sinus tract is traced by GP cone to the apex, and the patient has pain on biting. What is the most likely diagnosis?

Correct answer: C. Pulp necrosis with chronic apical abscess

• A. ❌ Acute apical abscess presents with rapid swelling and severe acute pain — not a chronic, intermittent sinus tract.
• B. ❌ This tooth has already had RCT — pulpitis diagnoses are irrelevant for a previously treated tooth.
• C. ✅ Correct. Previously RCT tooth + chronically draining sinus tract traced to apex + pain on biting = FAILED RCT with CHRONIC APICAL ABSCESS. The intermittent, chronically draining sinus tract is the hallmark.
• D. ❌ Same reasoning — a previously treated non-vital tooth cannot have pulpitis.