IAN Injury During Endodontics — ORE Part 1 MCQ
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Correct answer: D — Apical extrusion of filling material into the mental canal
**A is correct.** New numbness of the lower lip and chin immediately after obturation of a mandibular second premolar localises to the mental/inferior alveolar sensory pathway. This tooth may lie close to the mental foramen or anterior mandibular canal. Apical overextension of sealer or other root-filling material can enter this space and injure the nerve through direct mechanical pressure and chemical irritation. This precise presentation has been reported following treatment of a mandibular second premolar. **B** is possible after an inferior alveolar block but would be temporally related to the injection, not specifically to obturation. **C** is less likely to cause an immediate, well-localised sensory deficit and is not the characteristic endodontic mechanism. **D** would more typically cause mucocutaneous symptoms rather than unilateral mental nerve numbness. **E** would require substantial trauma and would have additional clinical signs.
Reference: Scarano A, Di Carlo F, Quaranta A, Piattelli A. Injury of the inferior alveolar nerve after overfilling of the root canal with endodontic cement: a case report. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology. 2007. https://pubmed.ncbi.nlm.nih.gov/17577544/