JAW MUSCLE PAIN AND ITS EFFECT ON GOTHIC ARCH TRACINGS

Perceived changes in occlusion and decreased range of motion are often expressed by patients with masticatory muscle pain. The adverse loadi ng of craniomandibular tissues that results from an inadequate maxillo mandibular relationship in combination with the coexisting dysfunction is widely regarded as the cause of pain. This study was designed to t est whether pain can cause significant changes in position of the mand ible and therefore form the basis for any perceived changes in the max illomandibular relationship. A second objective was to determine wheth er pain can cause changes in the mandibular range of motion. Five subj ects who rated pain intensity on a visual analog scale were used in a single-blind, randomized, repeated-measures study design. Tonic muscle pain was induced by infusion of 5% hypertonic saline solution into th e central portion of the superficial masseter muscle. Isotonic saline solution was used as a control, with subjects blinded to the type of s ubstance given. The effect of pain on the position of the apex of the gothic arch tracing, the direction of the lateral mandibular border mo vements, and the mandibular range of motion was studied in a horizonta l plane with minimal. occlusal separation. Pain significantly affected the position of the apex of the gothic arch tracing in anterior (F = 11.46, p = 0.03) and transverse (F = 35.0, p = 0.004) directions. Simi larly, pain affected the orientation of the mandibular lateral border movements (F = 12.44, p = 0.02) and their magnitude (F = 14.97, p = 0. 01). All pain-induced effects proved to be reversible. The observed ef fect of pain can explain the perceived change of bite that is frequent ly noted by patients with orofacial pain. This study provided evidence of an alternative causal relationship between pain and changes in occ lusal relationship and questions occlusal therapy as treatment, direct ed toward the elimination of the underlying cause in patients with mas ticatory muscle pain.