LITERATURE REVIEW SUPPORTS
Surface electromyography has long been the "gold standard" for monitoring muscle activity of masticatory muscle at REST and in FUNCTION. The value of surface EMG is best expressed by C.J.DeLuca, Professor of Biomedical Engineering and Research and Professor of Neurology at Boston University, "Surface EMG utilizes sensing electrodes placed on the skin, which allows the clinician to directly and accurately monitor muscle activity. This is far more accurate procedure than conventional manual palpation or touch which can provide only gross assessments of muscle activity." 1988. W.D.McCall also states "... there is general agreement among both clinicians and investigators that masticatory muscle activity is increased in symptomatic patients as compared with normal subjects. Electromyography is the principal tool used to investigate such differences." (The Musculature. A Textbook of Occlusion, Quintessence, 1988).
Many investigators have confirmed the safety, efficacy and value of surface electromyography for assessing RESTING and FUNCTIONAL status of muscle. 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. (Moyer, 1949; Lippold, 1952; Perry, 1954; Bigland and Lippold, 1954; Jarabak, 1956; Perry, 1957; Porrit, 1960; Grossman, 1961; Moss and Greenfield, 1965; Moller, 1976; Mitani et al., 1972; Moss and Chalmers, 1974; Moller, 1975; Yemm, 1976; Milner-Brown and Stein, 1975; Pruim et al., 1978; Bakke et al., 1980 Riise et al., 1982; Sheikholeslam et al., 1982; Sheikholeslam et al., 1983 Riise et al., 1984; Algren et al., 1985; Kyslinski et al., 1985; Sherman, 1985; Goldensohn, 1986; Hermans et al., 1986; Kydd et al., 1986; Sheikholeslam et al., 1986; Balciunas et al., 1987, Burdette and Gale, 1987; Wood, 1987; Crain and Clemons, 1988; Chong-Shan and Hui-yun, 1989; Christensen, 1989; Koole et al.; Neil etal., 1989; Van Eijen et al., 1990; Jankelson, 1992; Lynn et al, 1992).
The following list below is a partial list of the large body of supportive evidence documenting the use and efficacy of electromyography as applied in clinical dentistry.
There are numerous studies that support the physiologic basis for using quantitative electromyography in the diagnosis of temporomandibular and occlusal disorders (Moyers, 1949; Perry, 1954; Jarabak, 1956; Perry, 1957; Porritt, 1960; Grossman, 1961; Moller, 1966; Yemm, 1976; Bakke et al., 1980; Riise et al,, 1982; Sheikholeslam et al., 1983; Riise et al., 1984; Kydd et al., 1986).
There is evidence, based on controlled studies that used extensive statistical tests, that surface electromyography is reliable and reporducible (Goldensohn, 1966; Lloyd, 1971; Mitani and Yamashita, 1978; Riise, 1983; Hermens et al., 1986; Burdette adn Gale, 1987).
Controlled studies that used extensive statistical tests show that there is a strong relationship between EMG and muscular force (Lippold, 1952; Bigland et al., 1954; Molin, 1972; Milner-Brown, 1975; Pruim, 1978).
Several studies have quantitatively investigated the EMG during postural activity of the mandible and during maximal bite in the intercuspal position. The EMG values for the temporal and masseteric muscles have been quantitatively investigated in these studdies for control subjects without functional disorders and for patients with functional disorders. (Lous et al., 1970; Moller et., 1971; Sheikholeslam et al., 1980; Sheikholeslam et al., 1982; Moller et al., 1982; Cram and Engstrom, 1986). Thsese studies replicated the results that quantified statistically significant differences between the normal population and the patient population. The slight variability among these studies was due to the type of EMG instrumentation used in each study (i.e. range of filter frequency).
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.)
Controlled studies that used extenisve statistical tests conclude that postural activity of temporalis and masseter muscles are significantly higher in patients with functional disorders of the masticatory system thncontrols without such disorders (Moller, 1966; Lous et al., 1970; Moller et al., 1971; Sheikholeslam et al., 1982; Pantaleo et al., 1983; Geraris et al., 1989.)
Clinical studies investigating Electromyography of temporal and masseteric muscles concluded that EMG was effective in the diagnosis of Myofacial Pain Disorders (Sheikholeslam et al., 1986; Pantaleo et al., 1983; Cooper et al., 1986; Moller, 1969; Hlekimo et al., 1975; Mylinski et al., 1985; Riise et al., 1982; Sheikholeslam et al., 1983; Riise et al., 1984.) These studies further validate the basis for the use of EMG in clinical dentistry. The patients examined in the above studies exhibited high levels of EMG postural activity and weak EMG activity during maximal bite in the intercuspal position. Occlusal therapy resulted insignificant improvement in symptoms and pain , and the successfully treated patiens had significantly lower postural activity and significantly improved and symmetrical maximal bite activity.
In summary, based on well controlled empirical and clincal studies that have been conducted in several universities over the past three decades thoughout the world, there is unequivocal evidence to strongly support the use of EMG for the evaluation and diagnosis of temporomandibular joint and occlusal disorders.
The following list below is a partial list of the large body of supportive evidence documenting the use and efficacy of ultra low frequency TENS (Transcutaneous Electro-Neural Stimulation).
The medical literature is clear and unequivocal - low frequency T.E.N.S. (0.5 - 10 Hz) is both safe and efficacious for muscle relaxation and pain control. It is also clear that low frequency T.E.N.S. has a high degree of specificity when utilized for craniofacial pain (Andersson, 1979; Eriksson et al., 1984; Chapman et al., 1979; Andersson et al., 1977; Andersson and Holmgren, 1975; Sjolund et al., 1982; Phero, 1987; Lasagna et al., 1986; Thomas, 1986; Pantaleo et al., 1983; Wessberg and Dinham, 1977; Konchak et al., 1988).
Evoked response while using wire EMG electrodes
Choi and Mitani at Osaka Dental University in 1973 applied the Myomonitor to 15 subjects and monitored the evoked response using wire EMG electrodes. The study concluded "The evoked EMG was recorded from the anterior portion of the temporal, the masseter, the anterior ventral of the digastric, and obicularis oris and the buccinator muscles...The Myo-monitor pulse stimulates the nerve trunks of the fifth and seventh cranial nerves at the superior mandibular notch percutaneously and it appeared to have afferent and efferent effects."
Myo-monitor Stimulus is Transmitted Neurally
Using accepted intensity-duration methodology Jankelson, et al., 1975 demonstrated that the chronaxy values for Myo-monitor generated curves were well below those for direct muscle stimulation. Further verification of neural mediation resulted from the study of Williamson and Marchall, 1986 using succinylcholine. The study concluded "Succinuylcholine acts by competing with acetylcholine at the myoneural end plate and, therefore, no neurally stimulated muscle contraction under such conditions is by direct depolarization of the muscle itself. With the Myo-monitor evoking electrical impluses, there was no muscle contraction in either instance. This information would support the conclusion that they Myo-monitor stimulus is transmitted neurally."
Multiple Site Monitoring
Fujii 1977 at the University of Osaka used multiple site monitoring to distinguish M wave and H wave response. Using multiple anatomically separate recording sites the study concluded "Two kinds of response were obtained with latencies of about 2.0 msec. and about 6.0 msec. respectively. The former was assumed to be a direct potential (M wave) and the latter a monosynaptic reflex potential (H wave)." The use of recording sites anatomically distant from the input stimuli is essential for valid conclusions using this methodology. In a 1988 study of Myo-monitor stimulation, Dao, Feine and Lund for unexplained reasons placed the recording needle proximate to the electrode stimuli site.
Stimulation is Neurally Mediated
McMillan et al., 1987 at the University of Hong Kong concluded that "Contraction of muscles of the upper and lower eyelids, the lateral aspect of the nose and the upper lip indicates stimulation of the facial nerve, in particular its zygomatic and buccal branches. The results of our anatomic investigation indicate that this effect is produced by the stimulation of the branches of the upper division of the facial nerve as they pass in a more or less direct anterior course over the preauricular region. These branches will then be directly beneath a surface electrode placed according to the standard protocol. Propagation of the Myo-monitor stimulus along branches from the buccal anastomotic loops of the nerve would ensure contraction of muscles of the upper lip and angles of the mouth...This observation supports electromyographic evidence and results of intensity duration tests that indicate muscle contraction resulting from Myo-monitor stimulation is neurally mediated."
Latency and Conduction Velocity of Peripheral Motor Nerves
Goodgold and Eberstein examined eight individual investigative studies and found that normal distal latency and conduction velocity of peripheral motor nerves ranged from 2.1 to 5.6 msec. and 44.8 to 67.9 msec., respectively. They concluded that the latency to the obicularis oris which is innervated by the facial nerve in response to stimulation at the angle of the jaw, averages 2.5 to 3.0 msec. Basmajian summarized the results of six studies conducted by separate authors on peripheral nerve conduction velocity and found a range of conduction velocity between 37 and 73 meters/sec. Assuming the distance between the stimulation electrode and the wire recording electrode was approximately 2 cm, it should have taken .27 to .54 msec. for the pulse to travel this distance if the muscles were stimulated directly. This time interval is much less than the 1.85 to 4.4 msec. measured in the Dao study. This suggests the pulse must have traveled a much longer distance. A neurally mediated pulse would have: 1) .5 msec. charching the dermal capacitance, 2)neural conduction time of .7 msec. assuming a neural conduction pathway of 4 cm and conduction velocity of 55 meters/sec. which is the average of Basmajian's review, 3) residual latency (delay at the myoneural junction) of .6 msec., 4) intermuscular delay of approximately .4 msec. depending upon electrode placement. Adding the sum of these phenomena we find the latency of 1.8 to 4.04 msec. as measured by Dao, et al. is well within the rage of neurally mediated response, despite their electrode placement.
The following list below is a partial list of the large body of supportive evidence documenting the use and efficacy of Mandibular Tracking in the Diagnosis and Treatment of TMD/ MSD.
Progress in the field of mandibular tracking was limited by the capability of available instrumentation. As early as 1931 Hildebrand used cinematography of a moving reflective point to track mandibular movement (Hildebrand, G.Y. 1931). Cineflourography was used by Klatsky in 1941 (Klatsky, 1941) and was followed by Kurth's use of stroboscopic photography in 1942 (Kurth, 1942). Mechanical tracking has also been used by several investigators throughout the history of mandibular tracking in dentistry (Boswell, 1951). The interference of mechanical tracking devices with normal mandibular function was a common problem. The first use of electronic recording techniques to record occurrence and duration of occlusal contacts during mastication was reported in 1953 (5). Brewer and Hudson later used miniaturized make or break switches to study tooth contact (Brewer et. al., 1961). Adams and Cannon developed instrumentation to trace actual movement patterns of the mandible during functional and parafunctional movements (Adams et. al, 1964, Cannon et. al., 1964).
In 1975 Jankelson defined the requirements and criteria for a mandibular tracking system that would provide reliable quantitative and reproducible data. The criteria are:
1. The relationship of the mandible to the maxilla must be determined in three dimensions.Belser and Hannam demonstrated that an early model Myo-tronics Kinesiograph was capable of recording incisal point movement to within .3 mm anywhere within the envelope of chewing (Belser et. al., 1985). The same authors have used this instrumentation in other scientific studies, demonstrating their confidence in the capability and accuracy of this modality (Belser et. al., 1986).
Today's Mandibular Kinesiograph is a computerized electronic measuring device that can track mandibular movement with .1 mm plus or minus accuracy in three simultaneous planes as well as precisely measuring opening and closing velocity.
The value of this measurement capability to the clinical dentist responsible for establishing a predicatable and accurate occlusal position diagnostically and therapeutically is self evident. The ability to record, measure and capture and desired occlusal position transcends occlusal philosophy.
The value of coreelative data utilizing the MKG was emphasized in an AADR 1983 report by Bigelow, Slagle, and Chase, Department of Oral and Maxillofacial Surgery, University of Tennessee, entitled "Evaluation of Internal Derangement of TMJ with Mandibular Kinesiograph/Arthrography" (Bigelow et. al., 1983). The report stated:
"Arthography has established the increasing frequency of internal derangement of the TMJ. Jankelson et al have developed the Mandibular Kinesiograph (MKG) to characterize abnormalities of the TMJ. This study demonstrates a positive correlation between patients with stages of internal derangements and diagnostic MKG tracings. 20 patients were examined in this study. Historical, physical and radiographic criteria were used to diagnose patients with internal derangement of the TMJ. Arthrography was then performed to evaluate the extent of abnormalities. Patients were grouped according to the presence of clicks on opening, closing or both. Also on arthrography findings: normal, anterior dislocation with reduction, or anterior dislocation without reduction. Velocity tracing of the MKG were compared concerning characteristic and morphologic patterns. The velocity tracings were classified according to the irregularities in the opening and closing velocities. Correlations occur between velocity tracings and the arthrogram presentation of internal derangement which resulted in reduction or nonreduction during jaw excursions. Patients with arthrographic diagnosis of internal derangement without reduction demonstrated MKG tracings of impaired vertical opening deviation toward the affected side and characteristic irregularities in the velocity tracing. Patients with reduction showed only deviation to the affected side. MKG evaluation appears to be a reliable means to diagnose internal derangement of the TMJ."