Mental Nerve Injury RCT — ORE Part 1 MCQ

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ModerateEndodonticsMental Nerve Injury RCTORE Part 1

A patient develops persistent numbness of the right lower lip immediately after root canal treatment of the right mandibular second premolar. At review 3 weeks later, the numbness is unchanged. What is the most likely cause?

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Correct answer: D — Apical extrusion causing mental nerve injury

Explanation lettering: E = shown as A · C = shown as B · D = shown as C · A = shown as D · B = shown as E

A is correct. The mental nerve supplies sensation to the lower lip and lies close to the apices of mandibular premolars. Immediate, persistent lower-lip numbness after treatment of a lower second premolar is therefore most consistent with iatrogenic injury from material, irrigant or instrumentation extending beyond the apex and affecting the mental nerve or its continuation from the inferior alveolar nerve. Sealer extrusion during root-canal treatment of a lower second premolar has been reported to produce complete lower-lip anaesthesia. B is implausible because local anaesthetic effects are transient, not unchanged at 3 weeks. C would more usually cause local or systemic hypersensitivity features rather than isolated unilateral sensory loss. D may cause short-lived discomfort or pressure but does not best explain persistent, anatomically localised paraesthesia. E is inappropriate when there is a clear procedural onset and neuroanatomically coherent distribution.

Reference: Dastoori A, et al. Piezosurgical management of sealer extrusion-associated mental nerve anaesthesia: A case report. Australian Endodontic Journal. 2018. https://pubmed.ncbi.nlm.nih.gov/30338599/