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PubMed1999

Electromyographic examination of jaw muscles in relation to symptoms and occlusion of patients with temporomandibular joint disorders.

Clinical/occlusal scores and jaw-muscle EMGs were recorded in 24 TMD symptomatic (group S) and 20 normal (group N) subjects to evaluate the significance of EMG parameters and their clinical associations. Results indicated: (1) integrated EMG activity (IEMG) was larger at the rest position (RP) in anterior temporalis (Ta) but smaller at maximal voluntary clenching (MVC) in masseter (Ma) and Ta, and the ratios of IEMG at 70%MVC to the corresponding bite force (70%BF) were greater in group S; (2) mean power frequency (MPF) were almost the same in both groups but its shift was more rapid in group S; (3) silent period duration (SPD) was longer in group S; (4) asymmetry indices for SPD and silent period latency (SPL) were larger in group S; (5) muscle pain was associated negatively with IEMG at MVC and 70%BF but positively with IEMGs at RP and 70%MVC, and impaired jaw movements were associated negatively with the above EMG values; (6) muscle pain was positively associated with SPD in Ma, while joint pain and sound showed positive and negative associations with SPD, respectively; (7) associations between occlusion and EMG parameters were found more in group N. These findings verify: (1) jaw elevators in TMD may have hyper-tonic activities and a weak functional efficiency; (2) jaw muscles in TMD may become easily fatigued following a functional effort, and less relaxed following a muscle twitch; (3) the severity of pain could not be reflected in EMG activities, but impaired jaw movement may increase tonic activity and decrease functional effort; (4) TMD symptoms may alter the functional adaptation of jaw-muscle activities and occlusion.

Adaptation, Physiological↗
PubMed2002

Hormone-dependent fluctuations of pressure pain threshold and tactile threshold of the temporalis and masseter muscle.

In order to better objectify reported pain and disturbed sensation, psychophysical parameters as pressure pain threshold (PPT) and tactile threshold (TT) have been introduced in pain research. The present study evaluated fluctuations of these parameters, obtained using an algometer (PPT) and von Frey hairs (TT), in relation to fluctuations in female reproductive hormones. Ten students not using oral contraceptives and eight students using oral contraceptives participated in the study. In addition, seven male students served as a control group. During two menstrual cycles, the PPT and TT of the masseter and temporalis muscles, as well as from the hand, were obtained twice per week. At the end of the study the values were evaluated in relation to the different phases of the menstrual cycle, by means of a linear mixed model. The TT appeared very reproducible within subjects and did not fluctuate over time. Scores on the left temporalis muscle appeared significantly higher than that on the right side. In all subjects the PPT tended to be higher on the left side, while in students using oral contraceptives, the PPT values of the temporalis muscle were significantly higher in the menstrual phase, and lower in the follicular phase. A significant correlation between the PPT of the temporalis muscle and the TT of the overlying skin was observed.

Adult↗
PubMed2003

Effect of scanning level and muscle condition on ultrasonographic cross-sectional measurements of the anterior masseter muscle.

With the disadvantage of computed tomography showing cumulative biological effects and magnetic resonance imaging posing a problem in clinical availability and cost, several authors described the technique of ultrasonography to measure non-invasively local cross-sectional dimensions (LCSDs) of masseter muscle sites. However only few studies addressed the issue of 'technique-related factors for intra- and inter-observer reliability' to gain more consistent testing and diagnosis. The purpose of the present study was to determine (1) whether the scanning level and/or the muscle condition may affect LCSD measurements and (2) whether measurements made at identical levels may be reproducible. The study included 35 subjects with signs and symptoms of temporomandibular disorders. Bilateral ultrasonographic investigation was performed with a linear (B-scan) 7.5 Mhz small-part transducer to register LCSDs of the anterior masseter muscle on three different levels. Scans were made on the relaxed and contracted muscle. Measurements were made in two sessions with a time interval of at least 5 min. Data were analysed for reproducibility by using the intra-class correlation coefficient (ICC) and the method error (ME). Scanning level and muscle condition had a significant effect on muscle measurements (P = 0.000). There was no difference in LCSD between the right and left muscle (P = 0.531). Measurements recorded at a given site were consistent across the testing sessions (P = 0.058). The scanning level with highest reproducibility was halfway between the origin and insertion (ICC = 0.92; ME = 6.2%). The data suggest that ultrasonography is a reliable method for measuring LSCDs of the anterior masseter muscle.

Adult↗
PubMed2003

Effects of the antigravitary modification of the myotension of asset (MAGMA) therapy on myogenic cranio-cervical-mandibular dysfunction: a longitudinal surface electromyography analysis.

This study was aimed at evaluating the effects of a novel physiotherapy machine called MAGMA (AntiGravitary Modification of the Myotensions of Asset) on postural and masticatory muscles of subjects with myogenic cranio-cervical-mandibular dysfunction (CMD), by using surface electromyography (sEMG). Fifteen subjects, nine males and six females (mean age 27.6 years), with CMD were included in the study. The bilaterally monitored muscles were: masseter, anterior and posterior temporalis, digastric, posterior cervical, sternocleidomastoid, and upper and lower trapezius. All muscles were monitored at rest, with a second record of maximal voluntary clenching (MVC) for both the masseter and anterior temporalis. Patients were subjected to MAGMA therapy for one session/week of 30 min over ten weeks. The surface EMG activity was recorded twice, at the baseline and at the end of the therapy. After MAGMA therapy, the sEMG activity at rest of the monitored muscles was significantly better when compared to the baseline; the only exception was the anterior and posterior temporalis muscles which did not improve. On the contrary, with the MVC, all the monitored muscles (masseter and anterior temporalis) significantly improved their sEMG activity. Although more investigations are needed, these results indicate that the use of such antigravitary therapy can provide a tool for resolving myogenic CMD.

Adult↗
PubMed1989

The silent period in the masseter and the anterior temporalis muscles in adult patients with mild or moderate mandibular dysfunction symptoms.

The electromyographical silent period in the masseter and the anterior temporalis muscles during tooth tapping and jaw jerk were studied in patients with fairly mild temporomandibular joint dysfunction symptoms. The length of the silent periods in the patient group did not differ generally from that in a control group. During tooth tapping, however, patients with distinct muscular disorders had shorter silent period duration (7.7 ms) than patients with other symptoms or when compared with control subjects (10.5 and 11.3 ms, respectively). The duration returned to normal after correction of the muscular disorders. This finding suggests that the duration of the silent period is affected by the muscle condition. Patients with obvious muscular disorders of mild to moderate magnitude, thus, may show a shorter silent period duration during tooth tapping.

Adult↗
PubMed1994

Masticatory electromyographic activity in healthy young adults and myogenous craniomandibular disorder patients.

UNLABELLED: The electromyographic (EMG) activity of the masseter and the anterior temporalis muscles were compared between 60 healthy controls and 61 myogenous craniomandibular disorder (CMD) patients. Subjects were asked to clench at 10% and at 50% of their maximum voluntary clenching level. The effects of CMD, age and gender were statistically analysed with the use of the analysis of covariance. The correlations between EMG asymmetries and the lateral slide from the retruded contact position to the intercuspal position and the asymmetry in the number of post-canine tooth contacts between the left and the right side were investigated. The CMD patients showed lower masseter EMG activities than the controls, whereas the anterior temporalis EMG activity was not different between the two groups. The activity index, relating the anterior temporalis EMG activity to the activity of the masseter muscles, confirmed the presence of a relatively high temporalis activity in the CMD group. No significant differences were found in the EMG asymmetries between the controls and the CMD patients. Males showed higher masticatory EMG activities than females. These gender effects were significant for the anterior temporalis at the 10% and 50% level and for the masseter muscle at the 10% level. The anterior temporalis EMG activity declined with age. No age related effects were observed in the masseter EMG. The lateral slide was larger and more prevalent in the CMD group. A significant correlation between the lateral slide and the anterior temporalis EMG was found for the CMD group at the 10% level. No correlation was found between the EMG asymmetry and the asymmetries in post-canine tooth contacts. IN CONCLUSION: significant CMD, age and gender effects were observed in the masticatory EMG activities of a group of myogenous CMD patients and a control group.

Adolescent↗
PubMed1996

Patterns of jaw muscle activity during voluntary chewing.

Mastication is controlled by central rhythm and burst generators, but whether this control is similar under automatic and voluntary chewing is not clear. Our first aim was to determine whether increased chewing frequency led to a proportional decrease in both the burst duration (the time of muscle activity) and the interburst interval (time of inactivity) of each muscle or to a minimal decrease in the burst duration and a substantial decrease in the interburst interval. Our second aim was to determine whether these two manifestations of control differed between the opening and closing muscles. Electromyograms from digastric, medial pterygoid, masseter and anterior temporalis muscles were obtained during gum chewing by five subjects at four frequencies. A nearly fourfold decrease in total cycle duration (TCD) with increased chewing frequencies was accompanied by minimal changes in burst duration in the digastric muscle but proportional changes in the jaw closing muscles. The onset latency of the digastric muscle as a percentage of TCD decreased and became negative (i.e. occurred before opening started) as the TCD decreased. The onset latencies of the jaw closing muscles remained roughly 10-20% of the TCD for the three lower chewing frequencies. Control of the opening muscle appears to differ from control of the closing muscles.

Chewing Gum↗
PubMed2006

Effect of texture of plastic and elastic model foods on the parameters of mastication.

Mastication is continually modified throughout the chewing sequence in response to the texture of the food. The aim of this work was to compare the effects of an increase in hardness of two model food types, presenting either elastic or plastic rheological properties, on mastication. Each model food type consisted of four products of different hardness. Sensory testing experiments conducted with one group of 14 subjects showed significant perceived differences between products in terms of their increasing hardness. Fifteen other volunteers were asked to chew three replicates of each elastic and plastic product during two sessions. EMGs of masseter and temporalis muscles were recorded simultaneously with jaw movement during chewing. Numerous variables were analyzed from these masticatory recordings. Multiple linear regression analyses were used to assess the respective effects of food hardness and rheological properties on variables characterizing either the whole masticatory sequence or different stages of the sequence. Muscle activities were significantly affected by an increase in hardness regardless of the food type, whereas the shape of the cycles depended on the rheological properties. The masticatory frequency was affected by hardness at the initial stage of the sequence but overall frequency adaptation was better explained by a change in rheological behavior, with plastic products being chewed at a slower frequency. A dual hypothesis was proposed, implicating first a cortical-brain stem preprogrammed mechanism to adapt the shape of the jaw movements to the rheological properties of the food, and second, a brain stem mechanism with mainly sensory feedback from the mouth to adapt muscle force to the food hardness.

Adaptation, Physiological↗
PubMed1986

Histomorphometry of masticatory muscles in the muscular dystrophic mouse.

Cross sections of normal and dystrophic digastric, masseter and temporalis muscles from 7-week-old mice were studied by histomorphological and histomorphometrical methods in the light microscope. The histomorphological part of the study revealed marked differences in morphology between normal and dystrophic muscles. Mutual differences between the dystrophic muscles were also observed. Comparisons of the parameters chosen for the histomorphometrical part of the study, i.e., cell size and number of centrally positioned nuclei in a given number of fibers, revealed that the digastric muscle seems to be the least affected and the masseter muscle the most affected by the disease.

Animals↗
PubMed2006

The effect of disclusion time reduction on maximal clench muscle activity levels.

Simultaneous recording of excursive function and muscle activity on 62 MPDS patients demonstrated that reducing prolonged disclusion time (1.4 seconds per excursion) to short disclusion time (0.41 seconds per excursion) created a therapeutic effect such that within one month's time following treatment, there was an observed increase in the maximal clenching capacity of the masseter and temporalis muscles. This clinical treatment effect appears to be the result of decreased ischemia in these same muscles resultant from minimizing the time posterior teeth compress their periodontal ligament mechanoreceptors as these teeth are engaged and disengaged during excursive function.

Analysis of Variance↗
PubMed2004

Rehabilitation of partially edentulous patient with loss of vertical dimension.

A case of rehabilitation of an edentulous patient with loss of vertical dimension is presented here. This patient presents with a Class III dental and skeletal malocclusion with an anterior cross-bite. The objective of this case report is to demonstrate that an accurate assessment of vertical dimension is necessary for good rehabilitation. The original vertical dimension was determined by a series of tests including, kinesiographic, electromyographic and transcutaneous electronic neural stimulation (TENS). Subsequently, the lost vertical dimension was re-established orthodontically. These examinations revealed a general hypertonicity of masticatory muscles due to the lost vertical dimension. Additionally, radiographs of the temporomandibular joint showed anteriorly displaced condyles. Following the completion of orthodontic treatment osseointegrated implants were placed to restore the dental arches.

Adult↗
PubMedDate not supplied

Randomized controlled clinical trial for verifying the effect of silicone-based resilient denture liner on the masticatory function of complete denture wearers.

PURPOSE: The purpose of this study was to investigate whether application of permanent silicone-based resilient denture liner (SR) to mandibular complete dentures significantly improves patients' masticatory ability compared to conventional heat-activated acrylic resin (AR). MATERIALS AND METHODS: Twenty-eight edentulous patients were randomly placed into 1 of 2 crossover groups (AR-SR/SR-AR) by using a random permuted block within strata method. The AR-SR group received AR denture treatments followed by SR denture treatments. The SR-AR group received treatments in the reverse sequence. The outcomes were classified by matiscatory performance, mandibular movement, electromyographic activity, and maximum occlusal force. RESULTS: No significant differences were observed in any of the baseline characteristic measurements between groups. SR denture wearers exhibited significantly higher masticatory performance than AR denture wearers. SR denture wearers exhibited a longer early-stage occluding period than AR denture wearers. There were no differences in electromyographic activity between the AR and SR groups. There were no significant differences in maximum occlusal force between the AR and SR groups. CONCLUSION: This study showed that the application of SR to mandibular complete dentures resulted in significant improvements to the patients' masticatory ability compared to AR.

Acrylic Resins↗
PubMed1996

Is quantitative electromyography reliable?

The reliability of quantitative electromyography (EMG) of the masticatory muscles was investigated in 14 subjects without any signs or symptoms of temporomandibular disorders. Integrated EMG activity from the anterior temporalis and masseter muscles was recorded bilaterally by means of bipolar surface electrodes during chewing and biting activities. In the first experiment, the influence of electrode relocation was investigated. No influence of electrode relocation on the recorded EMG signal could be detected. In a second experiment, three sessions of EMG recordings during five different chewing and biting activities were performed in the morning (I); 1 hour later without intermediate removal of the electrodes (II); and in the afternoon, using new electrodes (III). The method errors for different time intervals (I-II and I-III errors) for each muscle and each function were calculated. Depending on the time interval between the EMG recordings, the muscles considered, and the function performed, the individual errors ranged from 5% to 63%. The method error increased significantly (P < .05 to P < .01) with the time interval between recordings. The error for the masseter (mean 27.2%) was higher than for the temporalis (mean 20.0%). The largest function error was found during maximal biting in intercuspal position (mean 23.1%). Based on the findings, quantitative electromyography of the masticatory muscles seems to have a limited value in diagnostics and in the evaluation of individual treatment results.

Adolescent↗
PubMedDate not supplied

Dietary consistency and craniofacial development related to masticatory function in minipigs.

Since the 1890s oral biological researchers have been interested in the idea that strenuous mastication of unprocessed food will stimulate proper oral-facial growth and occlusal relationships. Conversely, lack of such function due to consumption of refined food is one hypothesis among many for the etiology of malocclusion in industrialized humans. Adequately controlled experimental testing of the idea has been limited to rats. To investigate the "disuse" theory in a larger-bodied and more occlusally relevant animal model, we raised four Yucatan minipigs from weaning on hard diet (HD) and another four on softened but equivalent diet (SD). The animals were monitored for eight months, sacrificed, and then occlusal and osteometric data collected. Variations due to dietary regime are pervasive and not due to caries, periodontitis, or attrition differences. Whereas HD body weight is 10% greater than SD, the deep masseter is 25% greater, with similar disproportion in superficial masseter and temporalis weight. Facial prognathism, arch narrowness, tooth crowding/maleruption and posterior cranial tapering are markedly different in the two groups. A curious posterior torsional difference in the mandibular rami, as well as broadness and flatness of the mandibular symphysis, also occur in SD. We performed a Q-mode principal coordinates analysis of the 19 logged variables for the specimens, bootstrapping the variable list, to demonstrate a statistically significant (P < .01) overall pattern of dramatic differences. Having controlled other celebrated orthodontic etiologies (genetic background, respiratory mode, infectious degeneration and interproximal attrition), these results support the proposition that dietary consistency relates directly to human craniofacial growth.

Animals↗