Relationships between jaw pain and jaw muscle contraction level: underlying factors and treatment effectiveness.

EMG representations of jaw muscle contraction levels were measured in dental patients with TMJ problems in addition to history and physical evidence of bruxing and clenching, TMJ problems alone, bruxing and clenching, and no pain. Patients with TMJ problems plus bruxing/clenching had EMG levels similar to those with clenching and bruxing problems alone. These levels were far higher than those in the groups with similarly low TMJ problems alone and with no pain. The pain groups were normal for anxiety level and life stress. Although a third of the patients produced a conversion V pattern on the MMPI, no effect was seen on treatment effectiveness. All but a few of the mixed TMJ problem/bruxism/clenching patients and of the bruxism/clenching patients showed considerable reduction in pain through use of treatment oriented toward muscle tension awareness and relaxation. The group with TMJ problems and normal masseter muscle tension made little progress.