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Endodontics · patient case question

Tooth #18 requires both crown lengthening and root canal treatment. Which should be performed first?

Patient case: Generalized Caries and a Throbbing Lower Left

Patient: 41-year-old male

Chief Complaint: “The bottom left throbs for twenty minutes every time I drink anything cold.”

Background: No dental care in 6 years. Drinks four sweetened sodas daily. Healthy, no medications, no allergies. Smokes occasionally at social events only.

Medications: None

Vital Signs: BP 122/78 mmHg · HR 74 bpm · RR 16 · T 98.4°F

Findings: Generalized caries. Tooth #19: deep distal caries, exaggerated and lingering response to cold lasting 20 seconds, no percussion tenderness, no periapical radiolucency. Tooth #18: subgingival distal caries with a narrow vertical bony defect on the distal; would require both crown lengthening and root canal treatment to restore. A full mouth radiographic series shows dark bands running across the premolar film.

  1. Crown lengthening
  2. Root canal treatment
  3. Neither — extract the tooth
  4. Both at the same appointment as the definitive crown preparation
Show answer and explanation

Correct answer: B. Root canal treatment

  • A. Incorrect. Performing surgery first risks committing to bone removal on a tooth that may prove non-negotiable or non-restorable, after which the surgery was pointless and the bone is gone.
  • B. Correct. Endodontic treatment comes first for several converging reasons: it confirms that the canal system can be negotiated and that the tooth is worth retaining before committing to surgery, it eliminates the source of infection, and it allows the final margin position to be planned against a known restorative outcome. A provisional restoration can then be placed while the surgical site matures.
  • C. Incorrect. The stem states the tooth is restorable with these two procedures. Extraction discards a restorable tooth.
  • D. Incorrect. Crown lengthening requires 8 to 12 weeks of healing before final margin placement, since the gingival margin continues to mature during that period. Definitive preparation at the surgical appointment leads to margin discrepancies.

Note: Flagged as context-dependent. Root canal treatment first is the standard sequence and the expected board answer. The genuine exception is when subgingival caries makes rubber dam isolation impossible — in that situation, crown lengthening or at minimum caries excavation with a build-up must precede endodontic access to permit an adequate seal.

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