National Physical Therapy Examination (NPTE) Practice Exam

Which muscle strengthening is most effective for increasing mouth opening in a patient with temporomandibular joint dysfunction?

1. Medial pterygoid

2. Lateral pterygoid

3. Temporalis

4. Masseter

The correct answer is: Lateral pterygoid

The lateral pterygoid muscle is the primary muscle involved in mouth opening and plays a critical role in the function of the temporomandibular joint (TMJ). Strengthening the lateral pterygoid can help improve the ability to depress the mandible (the lower jaw) which is essential for mouth opening. This muscle is unique among the muscles of mastication because it not only assists in opening the mouth but also facilitates the sliding and forward movement of the jaw, which is especially important in activities like chewing and speaking. In contrast, the other muscles listed have different functions related to jaw movement. The medial pterygoid primarily assists with jaw elevation and closing the mouth, and while it stabilizes the jaw, it does not directly facilitate mouth opening. The temporalis muscle predominantly functions to elevate and retract the mandible, contributing to closing the mouth. The masseter is mainly responsible for jaw closure and elevating the mandible. Therefore, strengthening the lateral pterygoid is the most effective approach for increasing mouth opening in patients experiencing TMJ dysfunction.