Endodontics · patient case question
Why did the patient feel sharp pain during instrumentation of a tooth diagnosed as necrotic?
Patient case: The Tooth That Jumped Mid-Treatment
Patient: 39-year-old male
Chief Complaint: Referred for root canal treatment of tooth #14. He reports no symptoms at all.
Background: Large restoration placed years ago. Routine radiograph revealed an apical lesion.
Medications: None
Vital Signs: BP 122/76 mmHg · HR 72 bpm · RR 16 · T 98.4°F
Findings: Tooth #14 is asymptomatic and does not respond to cold, with a well-defined apical radiolucency. Under local anaesthesia the canals are being negotiated when the patient suddenly jumps in pain as a file advances. Later in the appointment, after instrumentation, one canal bleeds persistently on irrigation.
Show answer and explanation
Correct answer: A. Vital, inflamed pulp tissue remains in one of the canals
- A. CORRECT. Pulp necrosis is frequently PARTIAL. A multi-rooted tooth can have a necrotic pulp in one canal — producing the negative cold response and the apical lesion — while another canal, most often the palatal or the second mesiobuccal, still contains VITAL, INFLAMED tissue. That tissue is exquisitely sensitive, and the file contacting it produces exactly this sudden sharp pain. The correct response is supplemental anaesthesia: intraligamentary or, most reliably, INTRAPULPAL injection directly into the responsive canal.
- B. A separated instrument is a mechanical complication. Broken metal in a canal does not itself cause pain — there is no nerve to stimulate if the tissue is necrotic.
- C. Apical perforation would cause pain on exceeding the apex — but the tooth is necrotic, and the periapical tissue is anaesthetised by the block. It also would not explain the persistent bleeding later.
- D. If the block had failed entirely, the patient would have been uncomfortable from the moment of access, not at one specific point in one canal.
Note: ⚑ FLAG. The recall keyed 'broken file'. A separated file causes no pain. The finding that the tooth is asymptomatic yet has an apical lesion, combined with sudden pain on instrumentation, points squarely to residual vital tissue. Pulp testing gives a single answer for a tooth with several canals — that is its limitation.