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Results for “Masticatory Muscles”

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At least 379 records · Page 21Linked to original sources
PubMed2002

Juvenile parameningeal rhabdomyosarcoma in a dog causing unilateral denervation atrophy of masticatory muscles.

A 23-month-old, male, Labrador retriever dog with a history of slowly progressive right-sided atrophy of the masticatory muscles was submitted for necropsy. A highly invasive neoplasm which destroyed adjacent soft tissues including the right trigeminal nerve was found in the right side of the cranial cavity. Metastases to the liver were also present. Microscopical features of the neoplasm were compatible with those of rhabdomyosarcoma, embryonal type. This diagnosis was confirmed by immunohistochemical demonstration of desmin and muscle actin within tumour cells. In human patients, rhabdomyosarcoma is the most common soft tissue sarcoma of childhood and adolescence. Parameningeal rhabdomyosarcomas are well-known topographic variants that are often non-amenable to complete surgical resection and therefore carry a more guarded prognosis. Juvenile parameningeal rhabdomyosarcoma resulting in denervation atrophy of the muscles of mastication has not been reported previously in dogs. Rhabdomyosarcoma should be included in the differential diagnosis of neoplastic conditions in the head and neck region of juvenile dogs presented with cranial nerve palsies or other neurological deficits suggestive of meningeal or central nervous system invasion.

Actins↗
PubMed1990

[Changes in the muscle fiber conduction velocity (MFCV) due to the masticatory muscle development. 1. Preliminary study in adults].

The purpose of this study was to investigate the methods involved in observing the muscle fiber conduction velocity (MFCV) both in the masseter muscle and the m. biceps brachii in healthy persons. Three adults were the subjects in this study, none of whom had any gnathofacial dysfunction. The EMG activities were recorded from the m. biceps brachii with the arm bent at right angles and the masseter muscle in the intercuspal position, in both muscles during 50% of maximum voluntary isometric contraction on the habitual side. Three types of surface electrodes were used. Type 1. the disc type electrodes array arranged straight, Type 2. the disc type electrodes array arranged independently, Type 3. the strip type surface electrodes array arranged straight. The EMG activities preamplified at three conditions of time constant, e.g., 0.003, 0.01, 0.03 sec on m. biceps brachii were analyzed through a personal computer system and a FFT analyser. The conduction velocity was calculated by the cross-correlation method. The results obtained in this study were as follows: 1) No differences in the MFCV between the time constant were noticed. 2) The electrode array arranged straight was effective in the measurement of the MFCV in adults and in particular the strip type series electrodes array arranged straight was the most effective to measure the MFCV in the masseter muscle. 3) The average MFCV of the m. biceps brachii and the masseter muscle were 4.13 +/- 0.29 m/sec and 14.28 +/- 1.21 m/sec respectively.

Adult↗
PubMed1997

Stress-induced changes in the functional electromyographic activity of the masticatory muscles.

The present study was undertaken to assess the effect of a non-experimental emotional stress situation on the functional electromyographic (EMG) activity of the masticatory muscles. The material comprised 15 dental students without signs and symptoms of disorders from the temporomandibular system. The activity of the masseter and anterior temporalis muscles was recorded bilaterally by means of surface EMG. The subjective degree of helplessness of the subjects was assessed and related to the EMG activity response, to assess a possible interrelation. The EMG activity during the stress situation was significantly greater than for the non-stress situation. This shift in EMG activity was seen for all the muscles and all the functions analyzed. No significant gender differences were found. When the subjective degree of helplessness is taken into consideration, women showed significantly higher ratings than male subjects. The Helplessness Scale ratings correlated with the changes in EMG activity.

Adult↗
PubMed2005

Analysis of masticatory muscle condition using the 4-dimensional muscle model for a patient with square mandible.

The present study was conducted to ascertain characteristics of mandibular movements in patients with SQM, observe the kinetics of masticatory muscles using a four-dimensional (4D) muscle model, and kinetically investigate the etiology of Square Mandible (SQM). As results, 1, In the maximum opening position, location of the condyle was beyond the articular tubercle for volunteer, but within the mandibular fossa for SQM patient. 2, While the temporal muscle of volunteer was markedly expanded, that of SQM patient was not. 3, In both volunteer and SQM during left lateral excursion, the right mandibular condyle moved to a position slightly before the lowest point of the articular tubercle. The 4D muscle model showed that the cause of limited mouth opening in SQM patient was insufficient expansion of the temporal muscle, and not dysfunction of the opening muscles. Insufficient expansion of the temporal muscle stresses the masseter muscle and leads to hypertrophy of the masseter muscle and hyperplasia of the mandibular angle, resulting in the unique facial configuration.

Adult↗
PubMed1998

Two-dimensional configuration of the myoneural junctions of human masticatory muscle detected with matrix electrode.

Motor unit action potentials (MUAPs) propagate bidirectionally from the myoneural junction along the muscle fibre. The propagation of excitation within single motor units can be detected during sustained isometric contraction using a surface electrode array. Electromyographic (EMG) signals from an adjacent pair of contacts along the muscle fibres show a very similar wave form with a time shift. In the present study, EMG signals of the masseter and the temporal muscles were obtained from two male adults during clenching in the intercuspal position using the multichannel surface electrode with 17 x 11 contacts. The two-dimensional location of the myoneural junction for each column from the source of the propagation was estimated. Each of the myoneural junctions was located in the lower portion of the masseter muscle and in the upper portion of the temporal muscle. However, the junction was distributed within 10 mm along the muscle fibres at different contraction levels in each muscle. This noninvasive technique of multiple surface electrodes enabled us to add to knowledge of the anatomical structure of the masticatory muscles examined.

Action Potentials↗
PubMed2005

Activity of masticatory muscles in subjects with different orofacial pain conditions.

The existence of a pathophysiological link between tonic muscle activity and chronic muscle pain is still being debated. The purpose of this retrospective, controlled study was to evaluate the electromyographic (EMG) activity of masticatory muscles in subjects with different orofacial pain conditions. The temporal and masseter EMG activity at rest and the masseteric reflex were recorded in two groups of patients with either myofascial pain (n=33) or neuropathic pain (n=20), one group of non-pain patients with disc derangement disorders (n=27) and one control group of healthy, asymptomatic subjects (n=32). The EMG activities of both muscles at rest were significantly higher in the pain patient groups compared to the asymptomatic control group. There was no significant difference between the disc derangement disorder group and the control group. The masseteric reflex amplitude was reduced in all patient groups when compared with the control group. In pain patient groups, the increased EMG activity at rest and the reduction of the masseteric reflex amplitude were equally distributed in the pain and non-pain sides. In addition, subjects presenting with bilateral pain showed higher EMG activity at rest than those with unilateral pain. These results suggested that the modulation of muscle activity was not the direct consequence of a peripheral nociceptive mechanism and seemed to indicate that a central mechanism was at work. The contrast between the increased EMG activity at rest and the reduction of the masseteric reflex amplitude may reflect modulations of motoneurones that differed in tonic versus phasic conditions in chronic pain patients.

Adolescent↗
PubMed1996

[Mesencephalic trigeminal nucleus neurons innervate both the masticatory muscles and the periodontal ligaments: a fluorescent double-labeling study in rats].

The mesencephalic trigeminal nucleus (Vme) neurons are primary sensory neurons transmitting orofacial proprioceptive sensation. The neurons innervating the periodontal ligaments and the masticatory muscles are intermingled with each other in the caudal part of the Vme. After fluorescent tracers, propridium iodide and bisbenzimide were applied to the inferior alveolar nerve and the masseter nerve on the same side of the rat, and a doubled-labeled neurons were observed in ipilateral Vme, mainly in the caudal part, and a few in the middle, rostral part. This reflects simultaneous innervation of both the periodontal ligaments and the masseter spindles by collaterals of peripheral process of single Vme neurons.

Animals↗
PubMed1997

Study of jaw movement and masticatory muscle activity during unilateral chewing with and without balancing side molar contacts.

This research evaluated the relationship between balancing side molar contacts and chewing patterns measured with a jaw movement analyser and multi-channel electromyography (EMG) of the masticatory muscles. Nine healthy subjects with relatively normal occlusions participated in the experiment and were divided into those with balancing side molar contacts and those without. The block gum chewing task was performed on each side of the mouth for 10 s. The results showed more asymmetrical levels of jaw closing muscle activity during unilateral chewing in the group with balancing side molar contacts when compared with the group without these contacts.

Adult↗
PubMed1990

[Study on the relation for physical properties of masticatory jelly and masticatory muscle activity].

To measure the masticatory force used for everyday foods it is desirable to base the measurements on one mouthful of food. However, one mouthful of food changes in size and hardness. The purpose of this study is to establish a formula for estimating a correlation between the amount and force of mastication, active potentials and their integrated values, and the concerned material's size and hardness no matter they are same or unified. It is possible to measure the amount of mastication for normal foods without recording electromyographically. The effective method for recording the hardness of the jelly is the application of needle plunger. The thickness divided by the hardness and multiplying the value with the volume of the material, an estimated formula is thereby established to correlate with the integrated values of mastication.

Bite Force↗
PubMed1989

Interrater reliability in masticatory muscle palpation.

Muscle palpation is an important procedure in screening for TM disorders and assessing results of treatment outcome studies, but interpretation of response may be subjective and vulnerable to examiner bias. Masticatory muscle palpation scoring was evaluated with respect to interrater agreement on 31 myofascial pain-dysfunction patients participating in a medication study. Two clinicians independently palpated the temporomandibular joints, muscles of mastication, and related head and neck musculature on three different occasions over the 6-week period of the study. Standardization of palpation technique and initial protocol for interpretation of subject response were discussed prior to the first examination. Further clarification and reinforcement of examination methodology and scoring were carried out prior to the second examination, 1 week later. Another 5 weeks passed, with no further standardization, before the third and last examination. A behaviorally anchored scoring system (0 to 3) was used to rate response to palpation. Results indicate that two investigators can achieve a fair degree of reliability when carefully standardized, further interrater standardization can result in higher reliability, and reliability can be maintained over at least a 5-week period of time.

Humans↗