EMG Activity Of Masseter Muscles Research Articles

EMG-CHARACTERISTICS OF MASTICATORY MUSCLES IN SUBJECTS WITH BRUXISM

Today, bruxism is a fairly common phenomenon. Bruxism is often defined as the parafunctional activity of the masticatory and facial muscles. Parafunction is called increased inappropriate activity, tension or even spasm of the masticatory and facial muscles, as well as the muscles of the tongue. However, the peculiarity of the work of masticatory muscles during the day in patients with signs of bruxism remains insufficiently studied.
 The aim of our study was to determine the features of EMG-activity of masticatory muscles in patients with bruxism.
 Materials and methods of research. We performed a clinical examination and superficial electromyography (EMG) of the masticatory muscles in 13 subjects aged 25 to 43 years. There were 7 women (53.8%), 6 men (46.2%). All examined subjects were somatically healthy, had no bad habits and defects of the dental arches. The mean age of the subjects was 32.5 ± 5.4 years. In the sample of patients, there were clinical signs of bruxism such as pathological abrasion of the hard tissues of the teeth; point dentin exposure; cracks in tooth enamel; hyperesthesia; pain or feeling of tension and discomfort in the masticatory muscles. All patients were performed superficial electromyography of the anterior temporal and masseter muscles using a 4-channel computerized electromyograph, according to the recommendations by Ferrario V., Sforza C. Electrical biopotentials of masticatory muscles were registered in tests lasting 10 s each: maximum bilateral teeth clenching, clenching of teeth on the left side; clenching of teeth on the right side. The data obtained during the EMG were processed using Synapsis software from Neurotech. We analyzed the indicators of maximum amplitude, mean amplitude (μV) of each muscle in every test. For objective evaluation of the results, we performed electromyography of masticatory muscles of 15 subjects comparable in age and sex without clinical signs of bruxism (control group, mean age was 33.4 ± 6.1 years).
 Research results. We determined the characteristics of EMG-activity of masticatory muscles in the control group in the test of bilateral maximum teeth clenching: symmetrical activity of masseter and temporal muscles on the left and right sides (p> 0.05), the value of maximum amplitude of contractions did not exceed 1200 μV. It was found higher EMG-activity of the masseter and temporal muscles on a working side, compared to a balancing one in the test of unilateral teeth clenching, that was statistically confirmed (p<0,05).
 In patients with bruxism, the EMG-activity of the masticatory muscles differed from the control group. Thus, the maximum amplitude of muscle contractions in all tests was significantly higher (p <0.05) among people with bruxism. EMG-activity of masseter muscles in the majority of cases (10 subjects – 76.9%) was greater than the temporal. In tests of unilateral teeth clenching, the EMG-activity of the temporal and masseter muscles was slightly higher on the working side, but the difference with the indicators on the balancing side was not statistically confirmed (p> 0.05). We found the peculiarity of the EMG-activity of the masticatory muscles in subjects with bruxism: the presence of pathological rhythmic peaks of activity in the resting phase. Differences in the indicators of EMG-activity between the subjects with bruxism and control group were evaluated using analyses of Student’s paired t-test. The hypotheses were verified at the level of significance p<0,05.
 Conclusions. Bruxism is a complex problem of the whole human body, characterized by neuromuscular activity. In our study, some features of EMG-activity of masticatory muscles were studied and established. Patients with clinical signs of bruxism had significantly higher values of maximum, mean amplitude, which are 2.3-3.5 times higher than normal. In most cases, the EMG-activity of the masseter muscles was higher than the temporal. Presence of pathological rhythmic peaks of activity in the resting phase was found. In the future, it is planned to study individual changes in EMG-activity of masticatory muscles in patients with bruxism at different stages of total dental rehabilitation.

EMG Activity of Masseter Muscles in the Elderly According to Rheological Properties of Solid Food.

ObjectiveTo assess the impact of aging on masticatory muscle function according to changes in hardness of solid food.MethodsEach of fifteen healthy elderly and young people were selected. Subjects were asked to consume cooked rice, which was processed using the guidelines of the Universal Design Foods concept for elderly people (Japan Care Food Conference 2012). The properties of each cooked rice were categorized as grade 1, 2, 3 and 4 (5×103, 2×104, 5×104, and 5×105 N/m2) respectively. Surface electromyography (sEMG) was used to measure masseter activity from food ingestion to swallowing of test foods. The raw data was normalized by the ratio of sEMG activity to maximal voluntary contraction and compared among subjects. The data was divided according to each sequence of mastication and then calculated within the parameters of EMG activities.ResultsIntraoral tongue pressure was significantly higher in the young than in the elderly (p<0.05). Maximal value of average amplitude of the sequence in whole mastication showed significant positive correlation with hardness of food in both young and elderly groups (p<0.05). In a comparisons between groups, the maximal value of average amplitude of the sequence in whole mastication and peak amplitude in whole mastication showed that mastication in the elderly requires a higher percentage of maximal muscle activity than in the young, even with soft foods (p<0.05).ConclusionsEMG data of the masseter can provide valuable information to aid in the selection of foods according to hardness for the elderly. The results also support the necessity of specialized food preparation or products for the elderly.

Changes in soft tissue profile and electromyographic activity after activator treatment

Abstract Background To date, few studies have correlated the changes in muscle activity and specific soft tissue variables in adolescents with malocclusions. Objective To determine associations between the soft tissue profile and electromyographic activities in temporalis, masseter and orbicularis oris muscles in children with Class II division 1 malocclusions treated with activators. Methods For this prospective study, 25 subjects with Class II division 1 malocclusions were randomly assigned to either a Treatment group (N = 15) or a Control group (N = 10). The mean skeletal ages of the subjects in the Treatment and Control groups were 11.3 ± 1.1 and 11.0 ± 1.3 years, respectively. The subjects in the Treatment group were treated with activators and the subjects in the Control group were untreated. Lateral cephalometric radiographs and EMG recordings of the anterior temporalis and masseter muscles during clenching, chewing and swallowing and the orbicularis oris muscle during whistling were obtained at the start of the study and 12 months later. Changes in the soft tissue profile were correlated with changes in the EMG activities in anterior temporalis, superficial masseter and orbicularis oris muscles. Results The upper lip to E line distance (UL-E) decreased more in the Treatment group than the Control group (p &lt; 0.05) and the H angle decreased in the Treatment group, but increased in the Control group (p &lt; 0.01). The EMG activities of temporalis and masseter muscles increased significantly in both groups. All between-group EMG differences were statistically significant with the exception of the activities in the temporalis and masseter muscles during swallowing. In the Treatment group, a significant positive correlation (r = .57) was found between the changes in UL-E and anterior temporalis activity during swallowing, and significant negative correlations were observed between the EMG activity of masseter muscle during swallowing and changes in LL-E (r = -.54), OLp-UL (r = -.55) and OLp-LL (r = -.67). Conclusions Activator therapy is accompanied by changes in the lips and temporalis and masseter activities during swallowing.

What Causes Muscle Atonia in REM?

What Causes Muscle Atonia in REM?

Electromyographic analysis of bruxism in a patient with Rett syndrome

Rett syndrome (RTT) was neurological disorder which affects usually female. They have severe autism, loss of purposeful use hand, weight loss and epilepsy. Previous dental reports suggested that RTT patient frequently have bruxism, and they recommended biteplate therapy for tooth protection from bruxism. However, we did not find any physiological approach of bruxism in patient with RTT. Here we first report of bruxism status of RTT by using EMG analysis, biteplate therapy, and make evidence of it. The masseter muscle EMG activity was statistically significant reduced after template therapy. This data was scientifically evidence that template therapy was useful tool for protect form tooth wear caused bruxism with RTT patient.

Velocity-dependent EMG activity of masseter and sternocleidomastoideus muscles during a ballistic arm thrusting movement

Two experiments were conducted to investigate the functional relationship between the general somatic motor function and the oral motor function. In Experiment 1, we analyzed the relationship between the amount of masseter muscle (MSS) activity and the velocity of a ballistic, ‘karate-do’ arm thrusting movement (ThrMov). ThrMov velocity was measured from video images taken with a high-speed CCD camera at a frequency of 500Hz. EMGs of MSS and sternocleidomastoideus (SCM) muscles as well as other related muscles were recorded simultaneously with video images in 6 varsity ‘karate-do’ athletes. Pearson’s correlation coefficients were calculated between EMG amplitude and movement velocity. EMG activity of MSS as well as the other muscles increased as a function of ThrMov velocity in all participants, as evidenced by highly significant (p<.01) correlation coefficients, ranging from .64 to .87 (mean: .75). MSS EMG activity attained during ThrMovs performed at maximum velocity ranged between 14.6% and 113.8% of this muscle’s MVC (45.7±39.3% MVC, mean±SD). SCM was also strongly active and closely associated with MSS. Besides changes in amount of EMG activity, it was further found that R-MSS EMG onset progressively shifted to the earlier phase of the ThrMov as ThrMov velocity increased. EMG onset time of R-MSS as well as R- and L-SCMs was negatively correlated with ThrMov velocity; when performed at maximum velocity MSS activation preceded the start of ThrMov by more than 100ms, whereas MSS was recruited last at ∼150ms after the start of ThrMov when performed at moderate speed (∼50% of maximum). In Experiment 2, the effects of head movement relative to the trunk on R-MSS and SCMs EMG activity were tested in both gazing and sidelong glancing conditions. A much smaller head rotation relative to the trunk was necessary during the ThrMov in the sidelong glancing condition compared to the gazing condition. R-MSS EMG activity was affected significantly by the difference between these conditions and decreased by 5.2% MVC in the sidelong glancing condition compared to the gazing condition. In association with the change in requirement for head movement between those conditions, EMG balance between the bilateral SCMs changed substantially. Finally, marked muscle activity during ThrMov was found in the MSS that was not directly involved in performing this movement, indicating a form of ‘remote facilitation’.

Modulation of masseter exteroceptive suppression by non-nociceptive upper limb afferent activation in humans.

The effects induced by non-noxious electrical stimulation of upper limb nerves on exteroceptive suppression (ES) of masseter muscle EMG activity were studied in 15 healthy subjects. EMG activity of masseter muscles was recorded bilaterally and great care was taken to minimise the activation of afferents other than the stimulated ones. Masseter ES was elicited by applying a non-noxious electrical stimulus to the skin above the mental nerve (Mt) of one side, during a voluntary contraction of masseter muscles at a prescribed steady clenching level. Onset and offset latencies and duration of early and late components of masseter ES (ES1 and ES2, respectively) were evaluated in control conditions and compared to those obtained when a non-noxious electrical stimulation was delivered separately to Med or Rad or simultaneously to both nerves (Med-Rad) of one side. Upper limb nerve stimulation could be simultaneous or it could precede or follow Mt stimulation by various time intervals. In control conditions, ES1 latency onset and duration values (mean +/- SD) were 11.3+/-2.9 ms and 16.9+/-2.1 ms, respectively, and ES2 latency onset and duration values were 44.5+/-6.0 ms and 28.6+/-11.1 ms, respectively. No significant differences were observed which were related to the side being recorded. Two types of effects, opposite in nature, were shown on masseter ES, depending on the time intervals between Mt and upper limb nerve stimulation. The first effect, which was facilitatory, consisted of a significant increase in ES1 and ES2 duration. A maximal increase in ES1 duration (134-155% compared to control value) occurred when upper limb nerve stimulation preceded that of Mt by 18-30 ms. Maximal ES2 lengthening (115-145%) was observed when upper limb nerve stimulation followed that of the Mt by 10 ms. The second effect was inhibitory and affected only ES2, which appeared completely eliminated when Med stimulation preceded that of Mt by 40-80 ms. By contrast, ES1 was never suppressed at any interstimulus interval. These data might reflect the different action of the central outflow, following the upper limb-induced effects, on the different neuronal circuits mediating ES1 and ES2.

Non-nociceptive upper limb afferents modulate masseter muscle EMG activity in man.

Recent electrophysiological data obtained in anaesthetized rats evidenced jaw muscle excitatory responses to the electrical stimulation of type II limb somatosensory afferents. In the present work, we describe an inhibitory reflex evoked in human masseter muscles by stimulation of non-nociceptive fibres travelling in the median and radial nerves (MED and RAD, respectively). Eighteen healthy volunteers participated in the study. Subjects were seated on a comfortable chair, with the complex head-mandible-neck-trunk and the limbs securely fixed to the chair. Attempts were made to minimize possible interferences due to the activation of afferents other than the stimulated ones. The subjects were instructed to contract masseter muscles at a submaximal level and to maintain a stable level of muscle contraction during all trials. EMG voluntary activity was recorded from both masseter muscles by means of coaxial needle electrodes before and after the electrical stimulation of MED and/or RAD at intensities below pain threshold. In all subjects, MED stimulation induced bilaterally a marked depression of masseter EMG activity, which occurred at a latency of 23.6 +/- 2.1 ms and lasted 27.8 +/- 6.6 ms. RAD stimulation also induced a marked reduction in masseter EMG activity, but this effect was clearly observed in 9 out of 18 subjects, and it showed latency (30.2 +/- 7.5 ms) and duration (44.9 +/- 5.4 ms) significantly longer in comparison with the MED-induced effect. All subjects exhibited the inhibitory period in masseter EMG following the simultaneous stimulation of both nerves; this one appeared at a latency not significantly different (25.3 +/- 5.9 ms) and lasted much more (37.4 +/ - 8.2 ms) than EMG depression evoked by MED stimulation. The duration of masseter muscle inhibition, induced by MED and/or RAD stimulation, was inversely related to the level of EMG activity, while latency was not related to it. Significant increases in the inhibitory period duration were also observed by increasing stimulus intensity, within a subthreshold range for the activation of nociceptive fibres. In all cases, the inhibitory period was followed by a later excitatory rebound activity, whose latency and duration depended on the duration of the preceding EMG inhibition and on the background level of masseter activation. In conclusion, results evidenced that the activation of arm somatosensory fibres modulates masseter muscle activity in normal man. This might lead to a coordination between limb and masticatory muscle activity, which is required in several complex motor acts.

Masseter muscle activity during vestibular stimulation in man.

Experimental data report that vestibular afferents affect trigeminal system activity. The aim of this work was to evaluate whether static vestibular stimulation affects the excitability of trigeminal motoneurons in man. In order to assess this, voluntary EMG activity of masseter muscles as well as duration and latency of the early and late components of EMG exteroceptive silent period were evaluated while keeping the subject in vertical position and during 20 degrees static tilt. The experiments were performed on ten adult subjects with no orofacial, neurologic and otologic disorders. Each subject sat on a chair, which kept the complex head-jaw-neck-trunk and the limbs securely fixed, in order to minimize any interference due to the activation of somatosensory and proprioceptive afferents from these districts. The subjects were instructed to contract masseter muscles at 25% of their maximum bite force and the isometric force monitoring was used as visual feedback. Exteroceptive silent period (ESP) of masseter EMG was elicited by electrically stimulating the inferior inter-incisal gum. Results showed that static vestibular stimulation induced asymmetrical responses on voluntary masseter muscle activity, which was reduced to 70.3 +/- 16.1% (mean +/- S.D.) of the control value during ipsilateral tilt and increased to 128.8 +/- 13.0% during contralateral tilt. The duration of the early (ESP1) and late (ESP2) silent periods was also affected: during ipsilateral tilt ESP1 and ESP2 duration increased to 130.0 +/- 3.5% and to 122.1 +/- 2.1% of control, respectively; during contralateral tilt it was reduced to 76.8 +/- 1.2% and to 83.0 +/- 1.7% of control, respectively. On the contrary, changes in latencies were not significant. These data evidenced an asymmetrical effect exerted on trigeminal motor activity by static tilt. Since the influence of all receptors which could be activated by static tilt, except that arising from the macular ones, was minimized in this study, it is likely that the observed effects, induced by static tilt on masseter muscle activity, were of macular origin.

Effects of a prepulse stimulus on the masseteric inhibitory reflex in humans

We investigated the effects of a weak cutaneous stimulus applied to the digital nerves (prepulse) on the masseter inhibitory reflex (MIR) to electrical stimulation of the mental nerve in nine healthy volunteers. The prepulse stimulus, which had no direct effect on the masseter muscle EMG activity, induced a significant decrement in the area of the second phase of the MIR at interstimulus intervals between 50 and 100 ms. The percentage reduction induced on the inhibitory phase of the MIR was not different from that induced by the same prepulse on the late excitatory phase (R2) of the orbicularis oculi muscle to supraorbital nerve electrical stimulation during voluntary contraction. The effects observed during contraction were significantly less marked than those observed in the blink reflex at rest. We conclude that prepulse inhibition occurs in various brainstem reflexes, is similarly active on excitatory and inhibitory responses, and is reduced during voluntary activation.

Effect of occlusal splints on the electromyographic activities of masseter muscles during maximum clenching in patients with myofascial pain-dysfunction syndrome

Integrated EMG activities of masseter muscles during maximum voluntary isometric contraction with and without full-arch maxillary stabilization splints were observed in patients with MPD syndrome having occlusal interferences and in healthy subjects having no occlusal interferences. The masseter muscle activity was more significantly reduced in patients with MPD syndrome during maximum clenching with splints than in those patients without splints. In healthy subjects, such a significant difference could not be observed with and without splints. This finding suggests that the elimination of the occlusal interferences by means of occlusal splints could reduce the degree of sensory information from the periodontal receptors during nocturnal clenching or grinding. This could result in a decrease in masseter muscle activity giving rise to muscular relaxation.