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 What
is Electromyography?
One of the diagnostic tools used in identifying and analysing
TMJ dysfunctions is electromyography, which is a cousin of
the electrocardiogram. As the electrocardiogram measures the
muscular activity of dysfunctions of the heart muscle, electromyography
measures the activity and dysfunction of head and neck muscles.
This information is important in treatment planning and for
documentation purposes.
How does it work?
EMG equipment evaluates muscle tension through sensors that
are placed over the head (see picture). This valuable information
tells the practitioner if the problem is ascending up the
spinal cord from below the neck or the problem is descending.
This is very important in correcting posture problems that
are either the origin or the effect of the temporomandibular
disorder. Swallowing and bite problems are identified so that
they can be treated. 
In Support of the Efficacy of EMG
Surface electromyography has been used by researchers (120
studies) and clinicians (2000+ in the U.S.) for over twenty
years. It is the only quantitative method to measure and document
the severity, progression, and treatment of muscle dysfunction
in the craniomandibular patient.
Over forty dental schools world-wide have produced over
120 studies - all validating two central facts regarding muscle
activity:
- Patients with craniomandibular dysfunction have distinctly
different patterns of muscle activity (at rest, in clench,
while chewing, and while speaking) than the asymptomatic
"normal" subject. So EMG clearly confirms and quantifies
the presence and severity of this muscle dysfunction.
- Successful treatment reduces the irregularity and severity
of muscle dysfunction. So comparison of post-treatment muscle
activity with pre-treatment muscle activity baseline documents
treatment efficacy.
Annotated Bibliography in Support
of Electromyography
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American Academy of Creniomandibular
Disorders - Guidelines for Evaluation, Diagnosis and Management
Quintessence Publishing, 1990 |
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Continuous muscle constraction,
measured by increased electromyogram activity, even at
rest, is an important diagnostic criteria of spasm. And
postural hypertonicity of the muscles is a diagnostic
criteria for myofascial pain. |
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Burdette, B.H., Gale, E.N.:
The Effects of Treatment of Masticatory Muscle Activity
and Mandibular Posture in Myofascial Pain-Dysfunction
Patients. J Dent Res 1988 67:1126-1130. |
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Pre-treatment EMG values of
both masseteric and anterial temporal areas were significantly
higher for the MPD group than for the control group, while
a lowering of tonic resting EMG activity alone does not
appear to be sufficient to ensure successful therapy for
MPD pain. |
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Burgess, JA., Sommers, E.E.,
Truelove, E.L., Dworkin, S.F.: Short-Term Effect of Two
Therapeutic Methods on Myofascial Pain and Dysfunction
of the Masticatory System. J ProsthetDent 1988:60:606-610.
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EMG was used to evaluate the
effect of muscle chilling with ethyl chloride and intervention
through reflexive inhibition. In general, EMG levels were
observed to decrease for treatment subjects. |
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Chaco, J. : Electromyography
of the Masseter Muscles in Costen's Syndrome. J Oral Med
1973;28:45-46. |
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Electromyographic (EMG) recordings
were taken on myofascial pain patients before and after
administration of diazapan. The administration of the
drug resulted in normal EMG recordings and relief of pain.
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Chong-Shan, S. : Proportionality
of Mean Voltage of Masseter Muscle to Maximum Bite Force
Applied for Diagnosing Temporomandibular Joint Disturbance
Syndrome. J ProsthetDent 1989:62;682-684. |
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Using electromyography, maximum
bite force was evaluated in TMD patients and controls.
Results indicate masticatory muscles of patients of TM
dysfunction are in a state of hyperactivity andtension.
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Clark,
G.T, Beemsterboer, P.L., Solberg, WK., Rugh, J:D.: Nocturnal
Electromyographic Evaluation of Myofascial Pain Dysfunction in Patients
Undergoing Occlusal Splint Therapy. J Am Dent Assoc 1981, 99:607-611.
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Level
of nocturnal masseter activity was evaluated in patients with
myofascial pain and controls. A significant positive correlation was
demonstrated between EMG level and symptom severity. There was also
significant positive correlation between EMG level, tooth wear, and
severity of symptoms. |
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Clark,
G.T, Seligman, D.A., Solberg, W:K., Pullinger, A.G.: Guidelinesfor the
Examination and Diagnosis of Temporomandibular Disorders. J
Craniomandib Disord Facial Oral Pain 19893:7-14.
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True
muscle spasm can be differentiated from protective splinting and
trismus by clinical inspection and electromyographic verification of
sustained involuntary muscle contraction at rest. |
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Cooper,
B.C., Cooper, D.L., and Lucente, F.E. Electromyographyof Masticatory
Muscles in Craniomandibular Disorders. Laryngoscope 101 , February,
1991.
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In
641 craniomandibular patients, hyperactive resting EMG levels were
significantly reduced through transcutaneous electrical neural
stimulation therapy. And after occlusal repositioning with an orthotic
appliance, the EMG showed an increase in maximum muscle activity
function and in coordination of muscle groups during mandibular
movement. Thus, clinical electromyographical studies are an important
aid in the treatment or craniomandibular disorders. |
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Dahlstrom,
L., Carlsson, S.G., Gale, E.N., Jansson, TG.: Stress-Induced Muscular
Activity in Mandibular Dysfunction: Effects of Biofeedback Training. J
Behav Med 1985 8:191-200.
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Initially
recorded EMG activity of the temporal muscle in the rest position was
correlated with signs of dysfunction. Compared to previously studied
healthy subjects, the patients had lower EMG activity in the recorded
muscles during maximal biting. |
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Dahlstrom,
L. : Electromyographic Studies of Craniomandibular Disorders: A Review
of the Literature. JOral Rehabil 1989,.16: 1-20.
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The
studies of basic EMG activity consistently show an increased rest
activity in investigated muscles, masseter and temporal, when recorded
in groups of patients with CMD symptomatic at the time of examination.
The average level of activity during maximum biting seems to be less in
patients compared to healthy subjects and certain findings may be
interpreted as muscle fatigue. The frequency, intensity, and/or
duration of masticatory muscle activity appeared defmitely to be
greater in symptomatic patients than in health controls. |
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Dohrmann,
R.J, Laskin, D.M: An Evaluation ofElectromyographic Biofeedback in the
Treatment of Myofascial Pain-Dvsfunction. J Am Dent Assoc 1978:
96:656-662.
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In
patients treated (or not treated) with EMG biofeedback, there were
significantly higher mean EMG levels than for a control group. Those
receiving biofeedback were able to reduce their masseter EMG levels
significantly, with concurrent reduction of symptoms. |
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Fuchs, P. : The Muscular Activity of the Chewing Apparatus During Night Sleep. J Oral Rehab 1975:2,35.
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Investigated
masticatory muscle activity using EMG during sleep. Dysfunctional
patients had higher muscular activity during sleep than healthy
persons. |
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Garret, N., et.al. : Effects of Denture Modification on Muscle Effort Across Masticatory Strokes. IADR Abstract 1691, 1991.
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EMG
was used to assess chewing efficiency after improvements in occlusion
and fit of existing poorly fitting dentures or insertion of new
dentures. There was a reduction in masseter muscle effort and an
improvement in masticatory function validated by EMG following denture
improvement. |
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Gervais,
R., Fitzsimmons G. W, Thomas, NoR.: Masseter and Temporalis
Electromyographic Activity in Asymptomatic, Subclinical, and
Temporomandibular Joint Dysfunction Patients. Journal of
Craniomandibular Practice 1989,.7:52-57.
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Resting
EMG levels were obtained fro asymptomatic, subclinical, and patient
significantly higher EMG activity than the asymptomatic or subclinical
groups. Temporalis was found to be a cite of greatest EMG activity more
frequently than the masseter. These fmdings strengthen diagnostic and
assessment procedures and criteria. EMG resting levels were determined
for patients and controls for frontalis, temporalis, and masseter
muscles. For each muscle, EMG activity was significantly higher for the
MPD group than for controls. |
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Isberg-Holm,
A., Widmalm, S.-E., & Ivarsson, R.: Clinical, Radiographic, and
Electromyographic Study of Patients with Internal Derangements of the
Temporomandibular Joint. Am JOrthod 1985,.88:453-460.
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Together
with clinical and radiographic examination, EMG recordings of the
masseter and temporalis muscles were obtained in patients with anterior
disk displacement and healthy subjects. In the patient group, EMG
activity occurred when the condyle slid over the disk. It was concluded
that masticatory muscle activity could be provoked by disk displacement
which ceased when the disk position was normalized on mouth opening. |
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Kohno,
S., Bando, E., Tanaka, B., Tabata, T:: Estimation from Masticatory
Muscle Activity, in Kawamura, Y, Dubner, R. (eds),. Oral-Facial Sensory
and Motor Functions, Chicago, Quintessence Publ Co., 1981, pp. 133-41.
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The
study evaluated the data relationship between jaw position and the
function of jaw muscles. The conclusion was that the occlusal positions
of the mandible on any subject can be estimated with high accuracy
solely from the activity of the masticatory muscles, utilizing EMG
patterns. |
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Lous,1.,
Sheikholeslam, A., Moiler, E.: Postural Activity in Subjects with
Functional Disorders of the Chewing Apparatus. Scand J Dent Res
1970;78:404-410.
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Patients
with functional disorders of the temporomandibular joint and the
muscles of mastication were compared with controls to assess activity
in the temporal and masseter muscles using EMG. On the average, the
level of postural activity in the patient was significantly higher than
the control group. |
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Manns,
A. Miralles, R. Guerrero, F. : The Changes in Electrical Activity of
the Postural Muscles of the Mandible Upon Varying the Vertical
Dimension. J Prosthet Dent 1981 ;45:438-455.
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Masseteric
EMG activity was monitored to assess the influence of splints with
varying vertical dimension in patients with mandibular dysfunction. A
significant reduction of masseter EMG activity in patients with thicker
splints was noted. |
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Mercuri,
L.G., Olson, R.E., Laskin, D.M: The Specificity of Response to
Experimental Stress in Patients with Myofascial Pain Dysfunction
Syndrome. J Dent Res 1979 58: 1866-1871.
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Electromyographic
studies measuring localized muscle tension in facial pain patients
support an association between increased EMG activity and muscle pain. |
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Miller,
A.J, Nielsen, I.L. : Neuromuscular Compensation in Subjects with
Craniomandibular Disorders. EMG of Jaw Reflexes in Man, 1989, Leuven
University Press.
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Subjects
with muscle pain and tenderness demonstrate five neuromuscular
characteristics of the jaw closing muscles as determined by EMG studies
with 1) increased postural activity of the jaw closing muscles; 2) less
electromyographic activity during maximal contraction such as during
clenching; 3) increased duration of masticatory discharge; 4) increased
masseter muscle activity during night bruxism; and 5) spastic discharge
of the ipsolateral temporalis muscles when a subject attempts to move
the jaw over the disk without reduction. |
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Myslinski,
N.R., Buxbaum, .fD., and Parenie, F..f: The Use of Electromyography to
Quantify Muscle Pain. Meth and Find Expd Clin Pharmacol, 1985:
7(10):551-556.
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This
study was designed to determine feasibility ofusing EMG to quantify
muscle pain in patients suffering from chronic myofascial paint
dysfunction. Measurements of perceived pain and EMG frequency and
amplitude were recorded before and after standard analgesic therapy.
The highest correlation between EMG recordings and subjective pain
ratings were demonstrated in the resting mode. A significant
relationship exists between the change in perceived pain and the EMG
levels. |
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Naeije,
M, Hansson, TL. : Electromyographic Screening of Myogenous and
Arthrogenous TMJ Dysfunction Patients. JOraIRehabiI1986,.13:433-41
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The
TMJ dysfunction pain of 40 patients was evaluated to be of a myogenous
origin or arthrogenous. Patients were asked to clench. Surface
electromyograms were taken of their masseters and anterior temporalis.
Statistically significant differences between two.patient groups were
found in EMG amplitude. |
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Nakamura,
1:, Inoue, 1:, Ishigaki, S., Maruyama, 1:: The Effect of Vertical
Dimension Change on Mandibular Movements and Muscle Activity. Int J
Pros 1988,.1: 297 -301.
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Significant
changes were observed in the EMG activity of the masseter and digastric
muscles in some ten subjects as the vertical dimension of occlusion was
altered using three different acrylic resin occlusal devices. |
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Nielsen,
I.L., McNeill, C., Danzig, w:, Goldman, S., Levy, J, and Miller, A.J:
Adaptation of Craniofacial Muscles in Subjects with Craniomandibular
Disorders. Am JOrthod Dentofac Orthop, January 1990, p.20-34.
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Surface
EMG recordings were taken on 43 subjects with pain in the
craniomandibular muscles and 17 controls. The results show that the
subjects with muscle pain use their anterior temporalis muscles with
less frequency and with less intensity in several responses than normal
subjects. Bilateral activity demonstrates that subjects with muscle
pain have a more severe asymmetrical recruitment of these muscles than
the more symmetrical recruitment seen in normal subjects. Muscle pain
clearly altered the recruitment of their jaw muscles, supporting the
concept that the neuromuscular system is altered in patients with
craniomandibular disorders. |
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Pasero, F., et.al. Clinical Signs ofTMJ Arthritis and Masseteric Maximal EMG Recording. IADR Abstract 516, 1991.
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EMG
activity was compared for subjects exhibiting mild, moderate, severe or
no arthropathy. A significant decrease in maximal clenching activity,
demonstrated through EMG, was demonstrated in patients with severe
arthropathy. Severe clinical signs ofTMJ arthritis are associated with
the decrease in jaw closing muscles performance. Hypo function is a
constant electromyographic sign of TMJ arthritis at advanced stages. |
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Ramjjord. S.P. : Bruxism: A Clinical and Electromyographic Study. J Amer Dent Assoc 1961a:62:21-44.
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Investigated
the relationship between occlusal disharmony, bruxism and pain in
stomatognathic system under various functional conditions. Increased
activity was initially commonly recorded from posterior temporalis
muscle at rest. During swallowing all patients exhibited a disturbed
EMG pattern. After occlusal adjustment normal muscle activity and
complete relief of symptoms were attained in all patients. |
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Sheikholeslam,
A., MoIler, E., Lous, I. : Postural and Maximal Activity in Elevators
of Mandible Before and After Treatment of Functional Disorders. Scand J
Dent Res 1982: 90: 37-46.
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In
a longitudinal study, clinical data on pain, tenderness, and EMG
recordings of postural, maximal activity recorded before and after
treatment in 37 patients. Forty-three dental students served as
controls. Treatment was followed bya decrease in pain, tenderness and
EMG postural activity. Duration of the right and left temporalis
muscles also became more uniform. |
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Shiga, H., et al: Change in EMG Power Spectra during Clenching in CMD Patients. IADRAbstract 1971.1991.
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EMG
power spectra has been widely used to study function of masticatory
muscles. In this research the use ofEMG spectral analysis to diagnose
craniomandibular disorders was explored. Mean EMG frequency of the
patient group was significantly larger than the normal group. The
authors suggest that EMG power spectra can be used as a tool in
differential diagnosis of CMD. |
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Trott,
P.H., Goss, A.N. : Physiotherapy and Diagnosis and Treatment of
Myofascial Pain Dysfunction Syndrome. IntJOral Surg 1978,.7: 360-5.
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Cold
stretching and reflexive inhibition therapy used in combination with
other therapeutic modalities reduced muscle tension evident in reduced
levels of electromyographic (EMG) activity . |
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VanBoxtel,
A., Goudswaard; P., Janssen, K.: Absolute and Proportional Resting EMG
Levels in Muscle Contraction and Migraine Headache Patients,
Headache.1983:23:215-222.
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In
this study, resting EMG levels were measured for frontalis and
temporalis muscles in patients suffering from muscle contraction,
headaches, migraine, or mixed muscle contractions/migraine headache.
Significantly higher levels were found in the headache groups. Resting
EMG levels were expressed as a percentage of EMG level during maximal
contraction. And headache patients generally showed lower maximal EMG
levels than control subjects. |
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