Electromyographic indices, orofacial myofunctional status and temporomandibular disorders severity: A correlation study.

De Felício CM, et al.: Electromyographic indices, orofacial myofunctional status and temporomandibular disorders severity: A correlation study. J Electromyogr Kinesiol. 2012.

Abstract

This study examined whether there is an association between surface electromyography (EMG) of masticatory muscles, orofacial myofunction status and temporomandibular disorder (TMD) severity scores. Forty-two women with TMD (mean 30 years, SD 8) and 18 healthy women (mean 26 years, SD 6) were examined. According to the Research Diagnostic Criteria for TMD (RDC/TMD), all patients had myogenous disorders plus disk displacements with reduction. Surface EMG of masseter and temporal muscles was performed during maximum teeth clenching either on cotton rolls or in intercuspal position. Standardized EMG indices were obtained. Validated protocols were used to determine the perception severity of TMD and to assess orofacial myofunctional status. TMD patients showed more asymmetry between right and left muscle pairs, and more unbalanced contractile activities of contralateral masseter and temporal muscles (p lesser than 0.05, t-test), worse orofacial myofunction status and higher TMD severity scores (p lesser than 0.05, Mann-Whitney test) than healthy subjects. Spearman coefficient revealed significant correlations between EMG indices, orofacial myofunctional status and TMD severity (p lesser than 0.05). In conclusion, these methods will provide useful information for TMD diagnosis and future therapeutic planning.

Clinical relevance of surface EMG of the masticatory muscles. (Part 1): Resting activity, maximal and submaximal voluntary contraction, symmetry of EMG activity.

Hugger S¹, Schindler HJ, Kordass B, Hugger A: Int J Comput Dent. 2012;15(4):297-314.

Based on a comprehensive computerized literature search supplemented by a specific manual search of the literature, the present review article focuses on concrete aspects of the application of surface electromyography (EMG) for evaluation of the masticatory muscles in general and of the masseter and anterior temporal muscles in particular, and presents the current base of knowledge on the clinical relevance of surface EMG in dental applications. In the first stage of the review, publications from the year 2000 or later reporting the results of controlled clinical trials (randomized as far as available) of patients with craniomandibular or temporomandibular disorders (TMD) were analyzed. 

Data from the selected publications were systematically compiled and divided into subject areas as follows: Resting activity, maximal and sub-maximal voluntary contraction, symmetry of EMG activity, and fatigue effects; EMG activity during mastication, factors (including pain) that affect EMG activity, and the impact of adjusting static and dynamic occlusal relationships; Effects of occlusal splints and other occlusal treatments. Surface electromyography is in principle a suitable tool for neuromuscular function analysis in the field of dentistry. 

If used according to the specific recommendations and in conjunction with a thorough and conscientious clinical history and physical examination, surface EMG measurements can provide objective, documentable, valid, and reproducible data on the functional condition of the masticatory muscles of an individual patient.

Conclusion : “Surface EMG measurements can provide objective, documentable, valid, and reproducible data on the functional condition of the masticatory muscles of an individual patient.”

Int J Comput Dent. 2013;16(1):37-58.

Surface EMG of the masticatory muscles (part 2): fatigue testing, mastication analysis and influence of different factors.

[Article in English, German]

Hugger S¹, Schindler HJ, Kordass B, Hugger A.

Abstract

The second part of this review of the literature on the clinical significance of surface electromyography (EMG) of the masticatory muscles systematically examines the results of clinical studies in patients with temporomandibular disorders (TMD), preferably randomized controlled trials, investigating relevant aspects of EMG activity during prolonged chewing activity (fatigue effects), during the mastication process, and under the influence of different factors. Studies on the influence of factors such as gender, age, tooth status, orofacial morphology and (acute) pain, the significance of different occlusal relationships during static and dynamic occlusion, and the impact of changes in static occlusion on EMG activity of the masticatory muscles were included in the review.

Bite force in patients with functional disturbances of the masticatory system

Helkimo, E., Carlsson, G.E., and Carmeli, Y.Bite force in patients with functional disturbances of the masticatory system.J. Oral Rehab. Vol. 2:397-406, 1975.

 In thirty patients treated because of dysfunction and thirty six control subjects bite force was registered before, during and after treatment. Repeated tests of bite force in the control group gave identical results. Bite force in the patient group was lower than the control group but increased with palliation of the symptoms during treatment.

Note: The finding of significant difference between bite force in patient and control groups is supplemental to the rationale for the EMG function test since integrated EMG and bite force are linear.

The effect of four jaw relations on electromyographic activity in human masticatory muscles

Hickman, David, M., Cramer, Richard, Stauber, William T. (1993) The effect of four jaw relations on electromyographic activity in human masticatory muscles. Archs Oral Biol 38:3, pp 261-264.

SUMMARY

Significant differences were found in the electromyographic (EMG) activation between the masseter and temporalis muscles for the leaf gauge (LG), manually manipulated (CR) and neuromuscular (NM) bite positions during maximal static clench. The LG position consistently demonstrated the lowest EMG activity, while the NM position displayed the highest degree of muscle activity. Similarly, the ratio of the masseter/temporalis EMG activity during maximal clench was lower for the LG and CR positions and highest for the NM position. These data indicate that the NM position produced the greatest total muscle recruitment, with more masseter involvement during maximal clench, and enabled the subjects to generate greater clenching forces in the NM position as compared to the LG and CR positions.

Analysis of maximal electromyographic activity of the masseter and anterior temporalis muscles in Myocentric and Habitual Centric in Temporomandibular Joint and Musculoskeletal Dysfunction

Jankelson, Robert (1990) Analysis of maximal electromyographic activity of the masseter and anterior temporalis muscles in Myocentric and Habitual Centric in Temporomandibular Joint and Musculoskeletal Dysfunction. Front. Oral Physiol., Karger, Basal, Vol. 7, pp 83-97

SUMMARY
A computer review of maximal bite integrated EMG values for 46 consecutive patients referred to a clinical practice for treatment of TMJ/MSD was analyzed for data correlation. The 46 patients included 37 females and 9 males. The average ages of the patients were 42 and 46 years, respectively, for females and males. The patients all displayed 3 or more of the standardized symptoms in the Kinnie-Funt TMJ profile [23]. Only those patients with EMG/CMS profiles indicating a positive rationale for orthosis therapy were selected. This meant that the patients had either an excess of 2.0 mm of freeway space, or had an anterior/posterior discrepancy between neuromuscular and habitual trajectory of closure that precluded selective grinding of the teeth.


(1) Analysis of 46 temporomandibular joint/musculoskeletal dysfunction patients showed masseter EMG activity significantly lower than anterior temporalis EMG activity during maximal bite to habitual occlusion. Since the masseter muscle is the primary force muscle, while the anterior temporalis is the primary posturing muscle, this appears to be a consistent finding in temporomandibular joint/musculoskeletal dysfunction patients with nonoptimal occlusion.
(2) The combined integrated EMG in the symptomatic temporomandibular joint/musculoskeletal dysfunction patient is significantly diminished when the patient maximally occludes in the habitual occlusion as opposed to the myocentric position. Restoration of the occlusion to a neuromuscular myocentric resulted in a 72.2% improvement in motor unit recruitment. The marked increase in motor unit recruitment and the significant reduction in the number of symptoms as reported by the patients in this study, suggests that the myocentric position is a more efficacious functional position for motor muscle recruitment than the existing habitual occlusion in the musculoskeletal dysfunction patient.
(3) The study supports previous studies showing reduced EMG activity during maximal bite in temporomandibular joint and musculoskeletal dysfunction patients. Therefore, integrated EMG of maximal function appears to be a reliable, quantitative modality to identify functional disorders of the masticatory system.
(4) Integrated EMG of maximal bite effort can be used as a quantitative means to monitor patient progress. There appears to be a significant correlation by the increase in maximal EMG activity of the masseter and anterior temporalis, and the reduction in the number of patient-reported symptoms.
(5) Providing a neuromuscular myocentric occlusal position for the temporomandibular joint/musculoskeletal dysfunction patients allowed markedly increased motor unit recruitment during maximal bite. The increase in function correspondingly resulted in concomitant reduction in the patient symptom index.
(6) Treatment to the myocentric position resulted in significantly more symmetrical recruitment of masseter and anterior temporalis motor units. The temporomandibular joint/musculoskeletal dysfunction patient appears to have a greater asymmetry of muscle function during maximal bite to the habitual occlusal position. Restoration of the temporomandibular joint/musculoskeletal patient to a neuromuscular myocentric position resulted in significant improvement of muscle recruitment and symmetry.

To conclude, this study of 46 consecutive clinical dysfunction patients confirmed the findings of Moller, Erikkson, Sheikholeslam, Ruse, Molin, Pruim, Jarabak, Kydd, Bigland, Lous, Prayer-Galletti, and Pantaleo and others in support of maximal bite EMG analysis for diagnosis and temporomandibular joint/musculoskeletal dysfunction.

The restoration of the dysfunctional patient to a neuromuscular myocentric occlusion results in significantly increased function and synergy of the anterior temporalis and masseter muscles.

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