Anatomy & Histology · patient case question
Which muscle is most affected in bruxism?
Patient case: Patient with a history of hepatitis C
Patient: 48-year-old man.
Chief complaint: Worn-down back teeth and jaw soreness in the mornings.
History: Hepatitis C diagnosed eight years ago, currently under hepatology follow-up. Reports morning jaw fatigue and has been told he grinds his teeth.
Findings: Generalized attrition with flattened cusps. Hypertrophy of the masticatory musculature bilaterally. No mucosal lesions.
Show answer and explanation
Correct answer: A. Masseter
- A. CORRECT. The MASSETER is the most powerful elevator and takes the greatest load in clenching and grinding. Chronic parafunction produces masseteric hypertrophy, tenderness on palpation at the angle of the mandible, and the characteristic morning jaw fatigue this patient describes. The temporalis is the second most involved.
- B. The buccinator is a muscle of facial expression that keeps the bolus between the teeth. It does not generate closing force.
- C. The digastric is a depressor, active in opening rather than clenching.
- D. The lateral pterygoid protrudes and depresses the mandible and is often tender in TMD, but it is not the principal force generator in bruxism.
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