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PubMed1986

The amplitude distribution of electromyographic activity of masticatory muscles during unilateral chewing.

The amplitude probability distribution function (APDF) of electromyographic activity was used to describe the variation in relative masticatory force in the superficial masseter muscle and the anterior temporal muscle during unilateral chewing. The masticatory force, predicted from an isometric reference contraction, increased significantly in both muscles when chewing an almond compared to chewing half a stick of gum. Analysis of the distribution levels of contraction showed that the significant differences in relative masticatory forces were found for high levels of contraction. The individual variations were large when masticatory force between the muscles was compared. Maximal loading of the masseter muscle and the anterior temporal muscle exceeded 100% of the reference voluntary contraction in six females out of nine, mainly during chewing of an almond. The results indicated that APDF can be useful for analysing chewing when estimations of relative masticatory force and a measure of the distribution of different levels of contractions are desirable.

Adult↗

PubMed1989

[Cuspid protection and muscular reaction].

In an epidemiological study we found bilateral cuspid guidance in only 4, and unilateral cuspid guidance in 3 patients out of 247 patients examined. This suggest that cuspid guidance is a rare form of articulation. In the experimental part of this study the electric activity of the masseter and anterior temporal muscles was measured during empty mastication before and after the canines were treated with build-ups in a patient group with muscular and TMJ problems and matched against the results obtained in a control group of 10 healthy probands. Apart from the mean muscle activity also the path of excursion was recorded. Both values were combined in activity/path diagrams providing information on the muscular response to different forms of occlusion. Existing balancing contacts in mediotrusion, for instance, may produce high activities. With cuspid build-ups allowing correct cuspid guidance the patients with muscular and TMJ problems were symptom-free after just three days. After approx. one year the patients and the probands were recalled for a follow-up check. These and other results are discussed.

Cuspid↗

PubMed1984

[Physiological parameters of masseter and temporal reflexes in man].

This study is carried out in global electromyography, on man. The reflex activity of masseter and anterior temporal muscles is induced by a mechanical shock on the chin. The measures of the latency time duration and the silent period duration, are read in milliseconds on an oscilloscope screen. The average values of the latency time are/7.8 ms on the masseter muscle and 10 ms on the temporal muscle. The variability on this parameter, essentially neurological, according to the examined muscle, can be attributed to the diversity of the reflex passages. The average values of the duration of the silent period are of 36 ms on the masseter muscle and of 44 ms on the temporal muscle. This discrepancy is significant, and can be explained only by the specific functions of each of these two examined muscles. On the other hand, the high variability of the silent period duration, the same muscle, and in the same experiment, can be related to the strength of contraction exerted by the subject.

Electromyography↗

PubMed2000

Influence on myoelectric discharges of anteroposterior displacement of the mandibular position near the tapping point.

The purpose of this study was to examine the influence that the anteroposterior mandibular displacement near the tapping point exerts on the myoelectric activity of masseter and temporal muscles at a specific occluding force and to clarify the possibility of judging the mandibular position by measuring the amount of myoelectric discharge. Eight dentulous subjects were selected for the study. Surface electrodes were placed over the anterior, middle and posterior regions of the masseter muscle and over the anterior, middle and posterior bundles of the temporal muscle. Independently of the measurement region, the changes in the masseter and temporal muscle myoelectric activity which accompanied the anteroposterior mandibular displacement, were low. Moreover, when the mandible was displaced anteroposteriorly, the total amount of the myoelectrical discharge from all the recorded places, as well as the amounts of myoelectrical discharge over the middle part of the masseter muscle and the anterior bundle of the temporal muscle reached their lowest values in those mandibular positions which included the tapping point in less than half of the subjects. Therefore, this study indicates that the possibility of judging anteroposterior mandibular displacement by masseter and temporal muscle electromyography is quite low.

Adult↗

PubMed2002

Slug is a novel downstream target of MyoD. Temporal profiling in muscle regeneration.

Temporal expression profiling was utilized to define transcriptional regulatory pathways in vivo in a mouse muscle regeneration model. Potential downstream targets of MyoD were identified by temporal expression, promoter data base mining, and gel shift assays; Slug and calpain 6 were identified as novel MyoD targets. Slug, a member of the snail/slug family of zinc finger transcriptional repressors critical for mesoderm/ectoderm development, was further shown to be a downstream target by using promoter/reporter constructs and demonstration of defective muscle regeneration in Slug null mice.

Animals↗

PubMed2003

Expanded polytetrafluoroethylene membrane for prevention of adhesions in patients undergoing external decompression and subsequent cranioplasty.

Cranioplasty performed after external decompression for brain swelling may be difficult because of the development of adhesions between the temporal muscle and the dura. Membranes composed of expanded polytetrafluoroethylene (ePTFE) were inserted at external decompression to prevent such adhesions. The ePTFE membranes were placed suturelessly between the temporal muscle and the dura, covering the proximal portion of the temporal muscle at the sphenoidal ridge and the dural suture line. In addition, part of the membrane was placed directly below the skin incision to allow easy visualization at subsequent cranioplasty in 10 patients. Cranioplasty was performed 38 to 126 days (mean 63.9 days) after external decompression. No adhesions were observed, either between the ePTFE membranes and the dura, or between the membranes and the temporal muscle. No temporal muscle and dural injuries occurred during cranioplasty, and no patient showed signs of infection. Mean operating time was 71.0 minutes and mean blood loss was 75.2 ml. Sutureless insertion of ePTFE membranes at external decompression increases the ease and safety of subsequent cranioplasty, decreases operating time and blood loss, and avoids injury to the temporal muscle and dura.

Adult↗

PubMed1993

Gain and threshold of the jaw-jerk reflex in man during isometric contraction.

The control of mandibular posture has been related to the activity of the anterior temporal muscles, whereas the masseter muscles have been viewed mainly as force producers. However, these groups of muscles, especially in the deep layers, are highly endowed with muscle spindles, so that a difference in function should imply a difference in the reflex sensitivity. By studying the jaw-jerk reflex by means of bipolar surface electromyogram, the reflex sensitivity was determined from relationships between reflex amplitude and jaw displacement from both groups of muscles in eight subjects. At a constant level of background muscle activity, and hence with a constant excitability of the alpha motoneurons, the reflex sensitivity can be determined from these relationships in terms of gain and threshold. In order to account for differences in thickness of the soft tissues overlying the various muscles studied, the reflex amplitude was normalized with respect to the level of maximal voluntary contraction (MVC). In experiments where the inter-electrode distance was 18 mm over both groups of muscles, the reflex gain of the anterior temporal muscles was larger than that of the masseter muscles (P < 0.05). The threshold value did not differ significantly from zero for either group of muscles. Normalization of the reflex amplitude with respect to MVC can be carried out correctly only if the reflexly activated muscle fibres are distributed uniformly within the muscle. In order to gain an insight into this distribution, control experiments were performed with three subjects in which the inter-electrode distance was varied, thus influencing the depth in the muscle from which active muscle fibres were recorded. The reflex gain of the masseter muscle with an inter-electrode distance of 22 mm, which records from deeper layers of the muscle as well as superficial ones, was larger than with a distance of 11 mm (P < 0.01-0.10 in the various subjects). No such differences were found for the anterior temporal muscle. It was concluded that the afferents of the spindles in the jaw-elevator muscles do not project uniformly upon the motoneurons, but involve mainly fibres in the deeper layers of the muscle. The difference in gain found between the masseter and the anterior temporal muscles with the same inter-electrode distance of 18 mm is likely to be due to a larger distance of the reflexly activated muscle fibres in the masseter muscle with respect to the electrodes rather than to a difference in reflex sensitivity between the muscles.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed2002

Electromyographic activity of the jaw-closing muscles during jaw opening--comparison of cases of masseter muscle contracture and TMJ closed lock.

Contracture of jaw-closing muscles is one of the causes of limitations of jaw opening. In contracture patients who have no history of trauma or infection, it is not easy to distinguish contracture from temporomandibular joint (TMJ) closed lock (TCL). The purpose of this study was to clarify whether there is any difference between electromyographic (EMG) activities of jaw muscles during jaw opening in patients with TCL and patients with masseter muscle contracture (MMC). The MMC-patient group consisted of one male and 11 females with no history of trauma or infection. The TCL-patient group consisted of one male and 11 females. Ten of the MMC patients showed certain types of EMG activities in masseter muscles (and eight in temporal muscles) during jaw opening. However, particular EMG activities were not observed in most of the TCL patients. The integral values in masseter muscles and in temporal muscles at the maximum opening position were significantly higher in the MMC-patient group than those in the TCL-patient group. These findings demonstrate that the EMG pattern of MMC patients without a history of trauma or infection is different from that of TCL patients. Therefore, EMG analysis of jaw-closing muscles during jaw opening is expected to be useful for differential diagnosis between MMC and TCL.

Adolescent↗

PubMed1993

Morphological classification of the masticatory muscles in dogs based on their innervation.

The masticatory muscles and their innervations in dogs are classified, from deep to superficial layers, as follows: 1) medial pterygoid muscle and medial pterygoid nerve, 2) lateral pterygoid muscle and lateral pterygoid nerve, 3) anterior deep part of temporal muscle and anterior deep temporal nerve, 4) posterior deep part of temporal muscle and posterior deep temporal nerve, 5) superficial part of temporal muscle and superficial temporal nerve, the only branch of the temporal nerve which passes out from the infratemporal fossa, 6) zygomaticomandibular part of masseter muscle, which is thought to belong to the masseter muscle, and masseter nerve, 7) deep layer of masseter muscle and masseter nerve, 8) superficial layer of masseter muscle and masseter nerve.

Animals↗

PubMed1991

[Influences of balancing-side interference on jaw function].

The influences of experimental balancing-side interference on the jaw function were investigated on 6 subjects. A specially designed onlay was fabricated for the lower second molar, which acted as an artificial balancing-side interference in the lateral mandibular position. The subjects were asked to do maximum clenching, lateral gliding and gum chewing with and without the device. Electromyographic activity of the masseter and the anterior and posterior temporal muscles were measured and the related mandibular movement was simultaneously recorded during these tasks. Introduction of the experimental interference caused alteration in the muscle activity as follows: 1. When the subjects exerted maximum clenching efforts in the lateral mandibular position, the ratio of the temporal muscle activity on the working-side to the balancing-side decreased, while that of the masseter muscle remained unchanged. 2. There was a tendency for the activity in the working-side posterior temporal muscle to increase during gliding from intercuspation. The ratio of the temporal muscle activity on the working-side to the balancing-side decreased during gliding into intercuspation. 3. Prolongation of the occlusal phase associated with the increase of the muscle activity was observed during gum chewing on the side opposite to the interference. It was suggested that the balancing-side interference might provoke a specific muscle activity in the temporal muscles during parafunctional clenching or grinding.

Adult↗

PubMed1995

EMG differences between weak and strong myogenous CMD patients and healthy controls.

Electromyographic and clinical characteristics of 42 myogenous craniomandibular disorder (CMD) patients were related to 40 healthy control subjects. Surface EMG recordings were obtained from the masseter and the temporal muscles. The clinical examination included active maximum mouth opening, endfeel distance, active laterotrusion and lateral endfeel distance, dental abrasion, the presence of a lateral slide (RCP-ICP) and the amount of static pain. Orthopantomographic X-rays were available from 32 CMD patients for measuring the condylar and ramus asymmetry. Compared to the control group lower masseter and temporal EMG amplitudes were found for myogenous CMD patients (P < 0.001). When the activity of the temporal muscle was compared with the activity of the masseter muscle, the CMD patients showed proportionally higher temporal muscle activities than the controls (P < 0.05, 50% clenching level). CMD patients also showed smaller mandibular excursions, larger endfeel distances and more dental abrasion than controls. The temporal muscle asymmetries showed significant negative correlations with the ramus asymmetries. The lower and upper quartile of the distribution of the mean masseter EMG amplitudes were used to distinguish weak and strong muscles in patients and controls. Weak patients showed proportionally high temporal muscle activities, larger masseter and temporal muscle asymmetries, and larger endfeel distances compared to strong CMD patients. These differences were not found between weak and strong controls. In conclusion, it can be said that the electromyographic and clinical findings of the myogenous CMD patients suggest a functional difference between weak and strong patients and indicate the need for more individually designed treatment modalities for functional muscle and joint CMD problems.

Adolescent↗

PubMed1988

Response patterns of craniomandibular muscles with and without alterations in sensory feedback.

1. Surface EMG recordings were made bilaterally from the anterior part of the temporal muscle, superficial masseter muscle, and the suprahyoid complex of muscles while tracking mandibular incisor movement in three planes. This was done in 20 normal subjects with 16 different responses. Some responses involved clenching whereas other responses occurred with actual mandibular movement. 2. Each muscle demonstrated a probability of recruitment dependent on the response that correlated with the intensity of recruitment. The higher the probability of recruitment, the greater the intensity of muscle activity. 3. The anterior temporal muscle demonstrated no statistically significant difference in any of the responses between the left and right muscles. The masseter muscle also demonstrated bilateral symmetry. 4. The anterior part of the temporal muscle was recruited in more than 60% of its trials (60% to 100%) in ipsilateral laterotrusion, retrusion, fast vertical raising, clenching on the ipsilateral or intercuspal position, and mastication. The temporal muscle was recruited in less than 60% of its trials in contralateral and incisor clenching, and less than 30% in contralateral laterotrusion, protrusion, and opening. 5. The superficial masseter muscle was recruited in more than 60% of its trials in protrusion, vertical raising, all clenches, and mastication. The masseter muscle was recruited less than 60% in retrusion, ipsilateral laterotrusion, and opening. 6. The suprahyoid group of muscles was recruited in more than 60% of its trials in protrusion, opening, and mastication. This group of muscles was recruited less than 60% of the time in clenching, lateral movements, and rapid vertical raising of the mandible. 7. Applying a maxillary splint to seven subjects significantly decreased the recruitment of the anterior temporal and masseter muscles during mastication. The splint also modified the use of the masseter muscle during protrusion so that it was less active, but increased its recruitment during contralateral clenching. The suprahyoid muscle group was unaffected by the maxillary splint. 8. These data support the concept that movement of the mandible from the intercuspal or rest position develops a coactivation pattern that will excite or inhibit a given muscle regardless of whether clenching with occlusal contacts or no occlusal contact is involved. 9. The data also demonstrate that the maxillary splint can alter the use of the jaw elevator muscles, predominantly in mastication.

Adult↗

PubMed1985

Regression analysis of electromyographic activity of masticatory muscles versus bite force.

Electromyographic (EMG) activity of the superficial masseter and the anterior temporal muscles versus the bite force was studied in 10 young women. They were fully dentate and had no dysfunction of the stomatognathic system. The descending part of the trapezius muscle was also chosen for EMG registration. The average bite force between the first molars was 396 N (Newton). Steeper slopes for the EMG versus force regression curve at high contraction levels than at low contraction levels for the superficial masseter muscle may indicate that this muscle has a recruitment pattern that differs from that of the anterior temporal muscle. In the case of the anterior temporal muscle there was no difference between the slopes for the EMG-force regression at low and high contraction levels. There was significantly increased activity in the descending part of the trapezius muscle mainly during high bite force levels in half the subjects.

Adult↗

PubMed2002

[Lengthening temporalis myoplasty].

Use of the temporal muscle to raise the lips is a very old technique. In 1934, Gillies folded the temporal muscle over the zygoma to the lip subcutaneously. In 1952, MacLaughlin proposed to attach the temporal muscle tendon to the lips. With this aponeurotic relay there is a risk of lengthening and necrosis, the main cause of long-term failure. Taking inspiration from Maclaughlin, lengthening myoplasty lowers the temporal muscle as a whole descending the tendon to the lip, thus obtaining lengthening from the posterior part.

Adult↗

PubMed1989

[Electromyographic study of masticatory dysfunction in patients with unilateral cleft lip and palate and reversed occlusion].

UNLABELLED: Masticatory dysfunction in patients with unilateral cleft lip and palate was studied on the basis of electromyograms of the masticatory muscles. The purpose of the study was to elucidate the origin of the dysfunction by means of comparisons among electromyograms of masticatory muscles in cases of normal occlusion, reversed occlusion and reversed occlusion caused by unilateral cleft lip and palate. Subjects were 10 cases of normal occlusion (10y2m-11y10m), 10 cases of reversed occlusion (7y2m-11y2m) and 20 cases of unilateral cleft lip and palate (8y0m-14y3m). In each subject, electromyograms of the masseter and anterior venters of the temporal muscles at the isometric-contraction phase were recorded by means of the surface-electrode method with mandible loads of 1-5 kg. The electromyograms were analyzed quantitatively by means of an electromyographic device called a Turn Counter. Relations between loads and amplitude as well as numbers of turns were examined. At the same time maximum masticatory pressure and occlusal contact points were measured and then examined in comparison with electromyographic findings. RESULTS: 1. Correlation coefficients between loads and amplitudes as well as numbers of turns decreased among the groups in this order: normal occlusion, reversed occlusion and cleft-caused reversed occlusion. Significant differences were observed between the normal-occlusive group and the reversed and cleft-caused reversed-occlusive groups. 2. No. difference was observed between the normal-occlusive and reversed-occlusive groups in terms of correlation coefficients between total sums of amplitudes and turns of the 4 masseter muscles (right and left masseters and anterior venters of the temporal muscles) and loads. Correlation coefficients in the cleft group were significantly smaller than those in the other 2 groups. 3. Because of great differences in regression coefficient among individuals, no synergic contraction pattern of the 4 mastication muscles (right and left masseter and temporal muscles) could be specified. 4. The A/T ratio of masseters in the cleft group was significantly smaller than those in the normal- and reversed-occlusive groups. 5. Under maximum load, the activity ratio of the 4 masseter and temporal muscles was 1:1 in the normal- and reversed-occlusive groups, whereas temporal-muscle activity predominated over masseter-muscle activity in the cleft group. 6. Maximum masticatory pressure decreased in the order: normal-occlusive, reversed-occlusive, and cleft caused occlusive. No correlation with electromyographic findings was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Child↗

PubMed1983

[Reflex activity of the elevator muscles of the human mandible: electromyographic study].

In this study of global electromyography, of the masseter and anterior temporal muscles of man, the stimulus used was the mechanical percussion of the chin, the results being recorded on an oscilloscope. The twenty-two subjects used presented no sign of pathology after clinical examination. On the same subject, for one given muscle, the reflex was identically reproduced. The latency time was a very constant parameter; 7,8 ms for the masseter muscle and 10 ms for the temporal muscle. These values are not significantly different from one another. They are compared to those obtained by other authors. On the other hand, the reflex response of the anterior temporal muscle can present a particular pattern comparable with that of the trigemino-facial reflex.

Adolescent↗

PubMed1998

Electromyographic activity of the jaw-closing muscles before and after unilateral coronoidectomy performed on a patient with coronoid hyperplasia: a case study.

There have been few reports analyzing the activity of the jaw-closing muscles after coronoidectomy performed on a patient with coronoid hyperplasia. This paper presents a case study using electromyograms (EMGs) to evaluate the effects of unilateral coronoidectomy on the activity of masseter and temporal muscles. The patient was a 25-year-old male whose maximal range of jaw opening was 24 mm. After coronoidectomy of the left region, the range improved to 43 mm. EMGs were recorded in the center of the masseter muscles and the anterior part of the temporal muscles during gum chewing. Preoperatively, no abnormal EMG activity was observed. Eight months after surgery, increase in the ratio of the bilateral temporal muscle activity and a decrease in the ratio of the right masseter muscle activity were observed, and the proportion of activity of jaw closing muscles was out of the normal range. Eighteen months after surgery, there was slight return to the preoperative EMG activity. It was concluded that unilateral coronoidectomy could result in EMG changes of masseter and temporal muscles with a gradual return.

Adult↗

PubMed2003

An electromyographic evaluation of the bilateral symmetry and nature of masticatory muscle activity in jaw deformity patients during normal daily activities.

This study was designed to investigate the nature of masticatory muscle activity and the balance in the bilateral symmetry of the masticatory muscle activity in jaw deformity patients. Fifteen patients (19.9 +/- 5.3 years) with lateral shift of the mandible caused by transverse craniofacial deformity and 15 controls (28.6 +/- 1.9 years) were used as the subjects in this study. Surface electromyographic (EMG) activities were recorded from the bilateral masseter and anterior temporal muscles during daytime (142 min, including mealtime) and sleep (142 min). The averaged rectified EMG values were normalized with reference to the EMG amplitude induced by a 98-N bite force. Bilateral symmetry of masseter and anterior temporal muscle activities was examined using an asymmetry index (AI) for both the controls and the patients. The normalized activities of the masseter and anterior temporal muscles during normal daily activities were lower in patients than in the controls. Asymmetry indices in patients were significantly greater during usual daytime activities and sleep for the anterior temporal muscle and significantly smaller during sleep for the masseter muscle as compared with the controls. The results show that masticatory muscle activity is lower in these jaw deformity patients in association with more prominent asymmetry of anterior temporal muscle activity than in the controls. It is suggested that these findings are highly relevant to occlusal interference and instability because of malocclusion and lateral mandibular deviation.

Adult↗