Mandibular premolar mental nerve distribution — ORE Part 1 MCQ

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ModerateApplied Dental SciencesMandibular premolar mental nerve distributionORE Part 1

After implant placement near the lower second premolar, a patient reports numbness of the lower lip and chin on the same side. Intra-oral soft-tissue sensation on the buccal gingiva anteriorly is altered. Tongue sensation is normal. What is the correct anatomical explanation for these findings?

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Correct answer: A — The mental nerve supplies sensation to the lower lip, chin and anterior buccal gingiva

Explanation lettering: C = shown as B · B = shown as C

The clinical triad of lower lip, chin, and anterior buccal gingiva numbness following lower premolar implant placement indicates mental nerve injury. The mental nerve (terminal sensory branch of the inferior alveolar nerve) has a distinct anatomical territory: extraorally it supplies the lower lip skin and chin; intraorally it supplies buccal gingiva of premolars and anterior teeth. This matches the patient's sensory loss pattern precisely. The preserved tongue sensation excludes lingual nerve injury (B). The lingual nerve supplies the anterior two-thirds of tongue, floor of mouth, and lingual gingiva—not lip or chin. The buccal nerve (C) innervates posterior buccal mucosa and molar gingiva, not anterior structures. The mylohyoid nerve (D) is primarily motor. The facial nerve (E) provides motor innervation to facial muscles and carries taste fibres, not tooth or soft-tissue sensation. Option A is the only anatomically complete and accurate explanation.

Reference: StatPearls, Anatomy, Head and Neck, Mental Nerve (PubMed PMID: 31536237; https://pubmed.ncbi.nlm.nih.gov/31536237/); corroborated by StatPearls Anatomy, Head and Neck, Lingual Nerve (PMID: 31536258).