During root canal therapy you have completed cleaning and shaping. While irrigating, the patient suddenly experiences sharp pain and the canal bleeds. The most likely explanation is:

Correct answer: A. A sodium hypochlorite (irrigation) accident

• A. Correct. Sudden pain and bleeding during irrigation after instrumentation suggests irrigant extrusion through the apex (a hypochlorite accident).
• B. A normal canal should not produce sudden pain and bleeding at this stage.
• C. Instrument separation occurs during filing, not during passive irrigation.
• D. A 'hot tooth' is an anesthesia problem before access, not this scenario.