This study was carried out to investigate the relationship between tensed mandibular positions, muscle tenderness and EMG activity, respectively, and between range of motion of the neck and sternocleidomastoid muscle tenderness. Under stressful
conditions, most of people take several types of behavioral patterns. Two of them observed frequently are clenching of teeth and grasping of fist. Prolonged clenching or grasping should increase electromvographic activity of associated muscle,
especially muscles of mastication and neck muscles and will cause hyperfunction, dysfunction and muscle pain. So it is necessary to relate EMG activity with muscle pain.
The author performed routine clinical examination in 47 patients with Temporomandibular Disorders, especially for presence or absence of muscle tenderness, Mandibular rest position was used as a baseline reference position and two more position
in
which
EMG activity was taken were rest position with grasping of fist and teeth cleching position. BioEMG of Biopak(r) system(Bioresearch Inc, USA) was used for measuring of integrated EMG in masseter, anterior temporalis, anterioir belly of diagastric
muscle
and sternocleidomastoid muscle. To measure of the range of neck motion, CROM(r)(Cervical-Range-of Motion, USA) was used.
@ES The obtained results were as follows :
@EN 1. EMG activity of all muscles except in masseter was higher in grasping of fist than those in rest position and there were significant correlation in EMG activity between the two position except in anterior belly of digastric muscle.
2. When comparing EMG activity between tender and non-tender muscle, all examined muscles did not show any significant difference, From this data, we could conclude that EMG activity was gencrally not changed with tenderness, of couse, it might
be
dependent with degree of musclr tenderness.
3. Number of tender points in examined muscles was also not significantly different between in patients with masticatory muscle disorders and in patients with internal derangement.
4. Cervical posture and range of motion of the neck was not differed significantly between in patients with and in patients without tenderness of sternocleidomastoid muscle.
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