Myofascial pain dysfunction syndrome (MPDS) is primarily caused by muscle overuse and strain. Bruxism, which involves repetitive clenching or grinding of teeth, leads to prolonged muscle contraction and fatigue in the masticatory muscles. This results in the formation of trigger points, causing pain and dysfunction characteristic of MPDS. Unlike other conditions, bruxism directly affects the muscles and fascia, making it a key precipitating factor.

Reference: Contemporary Oral and Maxillofacial Surgery, James R. Hupp, 6th Edition.