Which muscle is primarily responsible for protruding the mandible?

Correct answer: D. Lateral pterygoid (bilateral action)

• A. Buccinator is a cheek muscle that compresses the cheek against the teeth; it has no role in mandibular protrusion.
• B. Medial pterygoid primarily elevates the mandible; it has a minor role in protrusion when bilateral.
• C. Temporalis is primarily an elevator and, with its posterior fibers, a retractor of the mandible — not a protractor.
• D. Correct. Bilateral contraction of the lateral pterygoid muscles protrudes (protracts) the mandible by pulling the condyles and discs anteriorly along the articular eminence.