Surface Electromyography (sEMG) – Functional Clench

Right window – The same patient is able to show improvement muscle recruiting ability with the GNM orthotic and with cotton rolls used as a control.  This shows improved functional quality and no functional impairment.

  • A reduction in SEMG amplitude during a functional clench test is a clear indication of a physiologic impairment.
  • There is a linear relationship between the strength of a muscle and the amplitude of the integrated EMG.

Reference Literature:

  1. Liberson, WT.  Dondey, M., Asa. M.M.: Brief repeated isometric maximal exercises. Am J Phys. Med., 41:3, 1962.
  2. Soderberg GL, Cook TM. Electromyography in Biomechanics. Phys Ther. 1984; 64 1813-1820.

EMG Studies of Bite Force in Patients with Functional Disorders

  • There is evidence based on controlled studies that used extensive statistical test that maximal bite force and the electrical muscle activity during maximal bite in the intercuspal position are significantly weaker in patients with functional disorders of the masticatory system than controls without such disorders.


Molin, 1972; Helkimo et al., 1975; Randow et al., 1976; Sheikholeslam et al., 1980; Moller et al., 1982; Sheikholeslam et al., 1982; Kydd et al., 1986.

Occlusion is the ACT of closing.  One’s occlusion (bite) can be supportive toward functional health or it can be destructive toward physical functional impairment and dysfunction.  


“In a carefully controlled study of voluntary isometric biting forces at maximal and submaximal levels, Molin (1972) demonstrated that there were “progressively increasing force differences between the (control/healthy subjects and patients with mandibular pain dysfunction syndrome (MPD).  The joint study conducted at University of Karolinska and University of Gothenberg in Sweden concluded that “the patients generally produced only one half to two thirds of forces produced by the control subjects.”


Molin, C: Vertical isometric muscle forces of the mandible: A comparative study of subjects with and without mandifest mandibular pin dysfunction syndrome.  Acta Odont. Scan., 30:485-499, 1972.