Surface electromyography (EMG)is a series of tests to more specifically delineate and define hypertonic musculature in the compromised TMJ patient. These series of tests are necessary to differentially diagnose between intra-capsular interference (mensical or otherwise) and extra-capsular interference (influence of the surrounding hypertonic muscular matrix) so as to determine the predominant dysfunctions. Surface electrodes are placed over the muscles which in turn send impulses to the recording instrument. Defining the etiology of the TMJ patient's predominate neuromuscular dysfunctions will preclude misdirected palliative treatment regimens.
Surface electromyography utilizes eight channels monitoring the right and left posterior temporalis muscles, right and left anterior temporalis muscles, right and left masseters, and right and left anterior digastric muscles. A clinical hands-on muscle palpation examination is not able to quantify and objectively record muscle hypertonicity with out subjective intervention.
Muscles of the face and jaw can be recorded to determine hyperactive muscle activity and/or resting muscle activity. A strained jaw position can affect muscle activity. The objective is to determine the optimal resting jaw position at physiologic rest that harmonizes with resting EMG levels.
Hyperactive/Strained Muscles
Calm/Rested Muscles
- There is a broad body of literature that supports the physiologic basis for using surface EMG as an aid in assessment of muscle function/dysfunction. (38 + studies support this ending with Lynn et al, 1992).
- There is substantial evidence based upon controlled studies that confirm that surface EMG is reliable and reproducible. (18 studies ending with Dean et al., 1992).
- 87 studies verifying the use, safety, and efficacy of EMG to monitor masticatory muscle function/ dysfunction.
In summary, based on well controlled empirical and clinical studies that have been conducted in several universities over the past three decades throughout the world, there is unequivocal evidence to strongly support the use of EMG for the evaluation and diagnosis of temporomandibular disorders. - Robert Jankelson, D.D.S.