Which muscle is most affected (most active/hypertrophied and sore) in bruxism?

Correct answer: C. Masseter

• A. The lateral pterygoid mainly protrudes the mandible and opens/depresses it; it is not the chief clenching muscle, though it can be involved in TMD.
• B. The mylohyoid forms the floor of the mouth and elevates the tongue/hyoid, not a clenching muscle.
• C. Correct. The masseter is the primary powerful jaw-closing (elevator) muscle and is the muscle most heavily loaded, hypertrophied, and tender in bruxism/clenching.
• D. The buccinator is a muscle of facial expression that keeps food on the occlusal table; it is not a power closer.