Which muscle is primarily responsible for causing the maxilla to become retruded?

The medial pterygoid muscle plays a critical role in the movement and positioning of the maxilla. Its primary function is to elevate the mandible and contribute to protrusive and side-to-side movements of the jaw. When considering the action of retruding the maxilla, one must understand that the medial pterygoid exerts a significant force on the mandible during contraction. By pulling the mandible upward and slightly backward, it can cause a relative retrusion of the maxilla due to the relationship between the two structures during mastication.

The lateral pterygoid primarily assists in protruding the mandible and is responsible for depression and lateral movements, which does not lead to maxillary retrusion. The temporalis muscle primarily elevates and retracts the mandible, but its main function is not to directly affect the position of the maxilla. Similarly, the masseter primarily elevates the mandible and does not contribute significantly to maxillary retrusion. Thus, the medial pterygoid is the muscle most directly linked to this action.