[The electromyographic activity of the masticatory muscles during temporomandibular joint clicking]

16 patients with painless temporomandibular joint clicking were investigated electromyographically. EMGs were recorded during open-close movement from the superior and inferior heads of the lateral pterygoid muscle, the anterior belly of the digastric muscle and the temporal muscle. TMJ clicking was recorded with a microphone located over the TMJ simultaneously with EMG and incisal movement and velocity. 13 of 16 patients showed various changes in EMG patterns. 3 patients showed no changes in EMG patterns. Evidence that a hyperactive muscle induces TMJ clicking, was not observed. These results indicate that there may be many types of adaptation for TMJ clicking from the viewpoint of the various EMG findings of masticatory muscles. It is suggested that most of the electromyographic changes are not the cause of painless TMJ clicking but their result.