Myofascial pain and dysfunction (:-‘1PO)is the most common cause of masticatory pain and limited function for which patients seek dental consultation and treatment.The source of the pain and dysfunction is muscular, with masticatory muscles developing tenderness and pain as a result of abnormal muscular function or hyperactivity. This abnormal muscular function is frequently but not a’ways .associated with daytime” clenching or nocturnal bruxism. ‘Ihe cause of MPO is controversial, although it isgenerally considered to be multifactorial.? One of the
mo~ commonly accepted causes of MPO is bruxism secondary to stress and anxiety, with occlusion being a modifying or aggravating factor. MPO may also occur secondaryto internal joint problems, such as disk displacement
disorders or degenerative joint disease (OJO).Patients with MPO generally complain of diffuse, poorly localized/ preauricular pain that may also involve other muscles of mastication, such as the temporalis and medial pterygoid muscles. In patients with nocturnal bruxism, the pain is frequently more severe in the morning.Patients generally describe decreased jaw opening with pain during functions such as chewing. Headaches, usually bitemporal in location, may also be associated with these symptoms. Because of the role of stress, thepain is often more severe during periods of tension and Examination of the patient reveals diffuse tenderness of the masticatory muscles. The’fMJs are frequently nontender
to palpation. In isolated MPO, joint noises are usually not present. However, as mentioned previously, \OIPOmay be associated with a variety of other joint problems that may produce other T~f] signs and symptoms. The range of mandibular movement in MPO patients may be decreased and is associated with deviation of the mandible toward the affected side. The teeth frequently have wear facets. However, the absence of such facets
does not eliminate bruxism as a cause of the problem. Radiographs of the T}.!js are usually normal. Some patients haw evidence of degenerative changes, such as altered surface contours, erosion, or ost eophytes. These
changes, however, may be secondary to or unassociated with the MPO problem.