Muscles of mandibular opening — ORE Part 1 MCQ

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ModerateApplied Dental SciencesMuscles of mandibular openingORE Part 1

A patient with temporomandibular dysfunction has pain on wide opening and deviation during opening. The clinician explains the muscles responsible for depression of the mandible during active opening, alongside gravity and suprahyoid activity. What is the correct anatomical/physiological explanation?

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Correct answer: D — Lateral pterygoid assists translation of the condyle during mandibular opening

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

The lateral pterygoid (specifically the inferior head) is the principal muscle driving mandibular depression and condylar translation during jaw opening. Working synergistically with gravity and the suprahyoid muscles (digastric, mylohyoid, geniohyoid), it produces the anterior-inferior translation of the condylar heads characteristic of wide opening (>20–25 mm). Option A is incorrect: the masseter is a jaw closer (elevator), not opener. Option B is wrong: temporalis retrudes and elevates the jaw, not protrudes during opening. Option D and E are implausible: buccinator and orbicularis oris are facial muscles with no direct TMJ role. The combination of pain on wide opening and deviation in this patient reflects dysfunction in precisely this lateral pterygoid-driven translation mechanism.

Reference: Electromyographic activity of the human lateral pterygoid muscle during contralateral and protrusive jaw movements. PubMed (10217518); Assembly for treatment providing non-invasive controlled positioning and movement of a patient's jaw. US Patent (11903868); The lateral pterygoid muscle: anatomical, physiological and clinical considerations. PubMed (1844052). https://pubmed.ncbi.nlm.nih.gov/10217518/