NaOCl Accident — MFDS Part 1 MCQ

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ModerateRestorative PrinciplesNaOCl AccidentMFDS Part 1

During root canal treatment of a maxillary premolar, a patient develops sudden severe burning pain immediately after irrigation with sodium hypochlorite. There is bleeding through the canal followed by rapidly increasing unilateral facial swelling and ecchymosis. There is no urticaria, wheeze or hypotension. What is the most likely diagnosis?

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Correct answer: C — Sodium hypochlorite accident

The correct answer is **A, sodium hypochlorite accident**. It is a chemical tissue injury caused by inadvertent extrusion of sodium hypochlorite beyond the root canal into the periradicular tissues. The discriminating features are sudden severe pain during irrigation, bleeding through the canal, and rapidly developing swelling and ecchymosis. Subcutaneous emphysema produces swelling with palpable crepitus, usually after pressurised air exposure. An acute apical abscess does not ordinarily arise immediately during irrigation or cause rapid ecchymosis. A cervicofacial haematoma may cause bruising but does not explain the characteristic burning pain and canal bleeding following hypochlorite use. Anaphylaxis would be suggested by urticaria, bronchospasm, airway oedema or hypotension rather than this local chemical-injury pattern.

Reference: British Endodontic Society. A Guide to Good Endodontic Practice, Chapter 9: Management of a sodium hypochlorite accident. First edition, September 2022. https://www.rcseng.ac.uk/-/media/FDS/The-British-Endodontic-Society-guide-to-Good-Endodontic-Practice.pdf