Hypotension of musculus pterigoideus externus is associated with which malocclusion?

• A. distal occlusion
• B. open occlusion
• C. mesial occlusion
• D. unilateral displacement of the lower jaw

Answer: (A)

The main idea here is how the lateral pterygoid muscle controls mandible position. This muscle helps protrude the mandible and translate the condyle forward, while also stabilizing the articular disc during movement. When its tone is reduced (hypotonia), its ability to move the condyle anteriorly and maintain proper disc position is diminished. The mandible then tends to sit in a more retruded position relative to the upper jaw, leading to a distal occlusion (Class II) where the lower molars are behind the uppers. Other patterns don’t follow directly from generalized weakness of this muscle: unilateral displacement implies an asymmetric shift, mesial occlusion would mean the mandible sits forward (Class III), and open bite is a vertical discrepancy—not a primary outcome of reduced lateral pterygoid tone.