Transcutaneous Electrical Nerve Stimulation (TENS) Performed with the Myo-monitor Induced Relaxation and Relief of Pain

Pantaleo, T.,M.D., Prayer-Galletti, F. M.D., Ph.D., Pini-Prato, g., M.D., and Prayer-Galletti, S.,M.D.: "An electromyographic study in patients with myofacial pain-Dysfunction syndrome". Bull. Group. int. Rech.sc Stomat. et Odont. Vol. 26, pp. 167-179, 1983.

Summary:
An electromypgraphic (EMG) study of ipsilateral masseter and temporalis muscles was undertaken in healthy volunteers and in patients with MPD syndrome, with the aim of getting further insight into the pathophysiology of this disease.  Unlike controls, patients had abnormal MKG features and displayed involuntary sustained EMG activity at rest, chiefly in the temporalis muscles.

Transcutaneous electrical nerve stimulation (TENS) performed with the Myo-monitor induced relaxation and relief of pain: these effects were however reversed by voluntary mouth closures.

The correction of occlusal position by acrylic splints was able to induce  persistent reduction or a suppression of the abnormal EMG activity at rest and a good relief of pain: moreover, after the corretion, higher levels of EMG activity were found during maximal  biting in the intercuspal position.
Mechanisms underlying these effects were discussed and in particular it was suggested that abnormal afferenct activity from periodontium and jaw muscles may contribute to the establishment of sustained contraction leading to muscular pain, which in turn may cause reflex muscle activity in vicious circles. 

The Myo-monitor and the myo-facial pain dysfunction syndrome

Wessberg GA., Dinham, Richard: "The Myo-monitor and the myo-facial pain dysfunction syndrome".  Journal of the Hawaii Dental Association.  vol. 10, No. 2, Aug. 1977.

Summary:
Thirty patients presented symptoms with the Myo-facial Pain Dysfunction Syndrome.  All of these patients received Myo-monitor oriented therapy and nearly all of them professed some initial relief or total remission of their symptoms during the short time  span of this study,

The data presented is based largely on clinical observations and patient response to comparison of their symptoms before and after treatment.  Symptoms evaluated were generally related to muscle tenderness and mandibular mobility.
Conclusion:
Due to clinical observations and patient response in this investigation, it is concluded that:

1. The centric occlusion position is seldom coincident with the myo-centric position of occlusion in patients who exhibit symptoms associated with Myofacial Pain Dysfunction Syndrome.
2. A Myo-monitor generated occlusal position affords some relief if not complete remission of symptoms in 90% of cases treated.
3. Long-term follow-up studies are necessary to evalutate the success of treatment.

Freeway Space Measurement Using Mandibular Kinesiograph & EMG Before and After TENS

Konchak PA, Thomas NR, Lanigan DT, Devon RM: "Freeway Space Measurement Using Mandibular Kinesiograph & EMG Before and After TENS". Angle Orthodontist. October 1988.

Department of Community and Pediatric Dentistry, College of Dentistry, University of Saskatchewan, Saskatoon, Canada.

Abstract

This investigation expands on a previous pilot study of the effects of TENS on the resting position of the mandible. The tendency is for an increase in freeway space, but the variability of results makes individual evaluation essential.

PMID: 3264667 [PubMed - indexed for MEDLINE]

TENS Adjunct in the Management of Myofascial Pain-dysfunction

Wessberg GA, Carroll WL, Dinham R, Wolford LM: "Transcutaneous electrical stimulation as an adjunct in the management of myofascial pain-dysfunction syndrome". J Prosthetc Dent. 1981 Mar;45(3):307-14.

Abstract

Twenty-one patients, 14 women and seven men, presenting with symptoms of the MPD syndrome, were treated with a regimen based on a neuromuscular theory of occlusion involving TES. Evaluation of treatment results shows 95% success immediately after therapy and an 86% success 1 year after therapy. No effort was made to establish a personality profile on the patients nor to incorporate active psychotherapy in treatment.

Electromyography Tension and FrequencySpectrum Analysis Before and After TENS

Bazzotti L:Electromyography tension and frequency spectrum analysis at rest of some masticatory muscles, before and after TENS. Electromyogr Clin Neurophysiol. 997 Sep;37(6):365-78.

University of Liège, D.U. of Stomatology (Nancy).

Abstract:

On a population of 52 subjects surface electromyographic recordings were performed of 13.5 sec. of duration before and after ULF (Ultra Low Frequency)-TENS relaxing procedure, while they were holding their mandible at rest. For each recording the average of tension (IEMG) and the median of frequency was calculated. To compute the median of frequencies a Fast Fourier Transformer (FFT) was applied. In order to compare modifications induced by the 45' ULF-TENS relaxing procedure, so that the influence of ULF-TENS could be well isolated from any influence due simply to the time passing between one recording and another, three recordings were performed at different times: the first at time 0', the second at time 0' + 20', and only the third after TENS, time 0' + 20' + 45'. The results of the study permit us to draw the following conclusions: 1. it is confirmed that ULF-TENS can decrease muscle IEMG; 2. the study of the IEMG and frequency of the electromyographic signal at rest can be carried out starting from a window whose size and position in the 13.5 sec. of recording is arbitrary; 3. there is no connection between IEMG and frequency: in other words, at rest, there is no necessary correspondence between high or low IEMG and a high or low frequency values; 4. on application of the neurodiagnostic test of ULF-TENS, the IEMG of the electromyographic signal decreases, while the frequency of the signal remains unchanged. These last two observations permit us to hypothesize that the IEMG and the frequency of the electromyographic signal reflect some different and independent characteristics of the electrical activity of the muscle at rest.

Short-term and Long-term Effects of TENS

Eble OS, Jonas Ie, Kappert HF: "Transcutaneous electrical nerve stimulation (TENS): its short-term and long-term effects on the masticatory muscles." J Orofac Orthop. 2000;61(2):100-11.

Department of Orthodontics, University of Freiburg/Br., Germany. eble@zmk2.ukl.uni-freiburg.de

Abstract

In an electromyographic study on subjects with no functional disturbances of the masticatory muscles, the duration of the post-therapeutic effects of transcutaneous electrical nerve stimulation (= TENS) on the superficial masseter and anterior temporal muscle was analyzed. The myoelectric signals were registered from 20 healthy volunteers in 3 different mandibular positions. The recordings were performed before a 20-minute TENS application with the J-4 Myomonitor and continued with a sequence of follow-up registrations with increasing interval to the initial stimulation. The EMG signals underwent computer-aided analysis and were evaluated by determining the integrated values as a parameter of muscle activity, and after Fourier transformation by 7 describing parameters of the power spectrum (e.g. mean power frequency = MPF). A detailed analysis of variance of all data was used to investigate significant changes of the parameters during the observation period. Muscular response to TENS includes a decrease in muscular activity (= reduction in integrated EMG signals) and a shift in the power spectrum to higher frequencies (increase in MPF). These changes were statistically highly significant for both analyzed muscles and for all different mandibular exercises. As these reactions to TENS are contrary to muscle fatigue, the results can be interpreted as indicating that this type of therapy stimulates a change in the biochemical and physiological muscular conditions, which leads to muscle relaxation. Electromyographically, the post-therapeutic effect lasted for 2 hours in case of normal masticatory muscle activity but for more than 7 hours in case of low muscular loading. The alterations of the integrated EMG values were more persistent than those of the parameters of the power spectrum.