Retraction of the mandible is produced by which combination of muscles?

• A. Posterior fibers of temporalis, deep part of masseter, geniohyoid, digastric
• B. Anterior fibers of temporalis, superficial masseter
• C. Lateral pterygoid and medial pterygoid
• D. Mylohyoid and geniohyoid

Answer: (A)

Retraction of the mandible is a backward movement of the jaw toward the skull, achieved by muscles whose fibers pull the mandible posteriorly. The primary retractors are the posterior fibers of the temporalis and the deep portion of the masseter; their lines of pull draw the mandible back along the articular eminence. The geniohyoid and the digastric can assist in retrusion, especially when the hyoid apparatus is fixed, because their attachment to the mandible allows them to pull the jaw backward toward the fixed hyoid or skull. In contrast, lateral pterygoid mainly protrudes the mandible, while the mylohyoid and other depressors are involved in opening, not retracting. This combination best accounts for mandibular retrusion by providing the direct posterior pull plus an aiding role from the hyoid-associated muscles.