Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Masseter Muscle”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,315 records · Page 73Linked to original sources
PubMed1985

Recovery of jaw muscle function following injection of a myotoxic agent (lidocaine-epinephrine).

Intramuscular injection of 2% lidocaine hydrochloride with epinephrine (1:100,000) bilaterally into the masseter muscles of growing rats resulted in a 30% to 40% decrease in maximal stimulated bite force at 3 days following injection. By 6 days postinjection, bite force had begun to increase, but significant differences from control bite force levels were still present 15 days postinjection. By 25 days postinjection, recovery to control values was complete. These data are consistent with previously documented fiber destruction and subsequent regeneration following exposure to this and other local anesthetic agents. It is suggested that local myotoxic effects produced by the administration of such drugs may result in a transient functional deficit in the injected muscle(s) that may persist for up to 2 weeks.

Animals↗
PubMed1998

[Botulinum toxin type A treatment of cosmetically disturbing masseteric hypertrophy].

Two patients, a woman aged 21 and a man aged 29, with asymmetrical swellings of both mandibular angles and a painful, heavy sensation in the masticatory muscles (and in the woman also round the maxillary joint), were diagnosed as having hypertrophy of the masseter muscles. Both had the habit of jaw clenching and tooth grinding. Treatment consisted not of the traditional surgical debulking which also allows correction of overdeveloped osseous mandibular angles, but of injections with botulinum toxin type A. Injection of 40-60 IU (product: Botox) per muscle was followed by some atrophy; cosmetically satisfactory results were achieved after repetition of the treatment a few months later. Reduction of muscle volume was confirmed by a quantitative volumetric assessment of MRI scans. In the female patient, the pain also abated.

Adult↗
PubMed2007

Influence of human jaw movement on cerebral blood flow.

Temporal changes in cerebral blood flow induced by jaw movement have yet to be investigated. To assess the influence of pattern and intensity of muscle contraction during jaw movement on task-induced change in cerebral blood flow, we performed bilateral transcranial Doppler ultrasound examination during clenching, gum chewing, and tooth tapping in healthy volunteers. A random-effects model analysis revealed a significant increase in middle cerebral artery blood flow velocity during clenching (high muscle activity) and gum chewing (moderate muscle activity), compared with the preceding rest period; however, such an increase was not detected during tooth tapping (low muscle activity). Cerebral blood flow was greater on the working side during the intensive isometric contraction of the masseter muscle in clenching. These results suggest that task-induced change in cerebral blood flow during jaw movement is influenced by the change in peripheral circulation evoked by muscle contraction.

Adult↗
PubMed1995

Functional masticatory evaluation in hemifacial microsomia.

The features of hemifacial microsomia with unilateral condylar hypoplasia in a 9-year-old female patient were analysed in a multidisciplinary fashion. Cephalometric roentgenograms revealed malformation of the mandible, with the right condylar process being smaller than the left. In addition, the right maxillary alveolar process was underdeveloped. Closed view radiography with oblique lateral transcranial projection (by modified Schüller's method) of the temporomandibular joint revealed an anterior dislocation of the condyle on the unaffected side. Computed tomography (CT) of the masticatory muscles demonstrated that the medial pterygoid muscle on the affected side, unlike the other muscles, was larger than that on the unaffected side. The surface electromyographic activities of the temporal and masseter muscles and reduction of the maximum bite force on the affected side during clenching corresponded with the CT findings. The hypertrophy of the medial pterygoid muscle on the affected side was considered likely to be a compensatory adjustment to keep the mandible centred. A three-dimensional study of the movement of the mandible revealed that the condyle on the affected side moved vertically and that the rotational centre was located antero-inferior to the condylar process during maximum jaw opening and closing movements. These findings suggested lack of articular guidance. Moreover, the unaffected condylar process showed considerable backward movement during retrusion and ipsilateral excursion of the mandible. The mandibular head on the unaffected side showed obvious protraction during all jaw movements, which might have induced the overgrowth of the condylar head on the unaffected side in this growing child.

Alveolar Process↗
PubMed2003

Stroke-induced trismus in a pediatric patient: long-term resolution with botulinum toxin A.

We present a case of prolonged resolution of stroke-induced trismus after botulinum toxin A treatment in a 9 1/2-yr-old boy. The patient had an idiopathic right posterior fossa hemorrhage with resultant spastic quadriparesis, ataxia, dysarthria, and dysphagia. He developed right-sided trismus with only fair response to stretch. Several months after discharge, the patient had worsening trismus with an interincisal distance of only 0.4-0.7 cm and difficulty with oral hygiene and eating. The patient was treated with botulinum toxin A to the masseter muscles with minimal response. Four months later, he received botulinum toxin A to the bilateral masseter and temporalis muscles and to the right medial and lateral pterygoid muscles, with more improvement. His third and last botulinum toxin A treatment was to the bilateral masseter, temporalis, lateral, and medial pterygoid muscles in larger doses. He had an excellent response, maintaining an interincisal distance of 2.5 cm 1 yr later, with significant improvement in speaking and chewing.

Botulinum Toxins, Type A↗
PubMed1992

A new procedure for assessment of proprioception.

A new method for the assessment of proprioception was developed and tested with 40 healthy subjects on two facial muscles (i.e., masseter and zygomatic muscles). The experiment was repeated after 3 1/2 months. In our study, proprioception was studied with respect to sensations arising from the muscle spindles and tendon organs. Therefore, myesthesia was investigated, which was assessed by the correspondence between a voluntary muscle contraction and its immediate replication. Good perception was defined by a small integral of differences, standardized by duration and intensity of the contraction, and its replication. Results show that this measure is independent of the characteristics of muscle activation. In concordance with our hypothesis, myesthesia was superior in a muscle richly supplied with muscle spindles and afferent fibers (i.e., masseter muscle), to that for a muscle less prepared for afferent information processing (i.e., zygomatus major).

Adult↗
PubMed1998

Electromyographic investigation of masticatory muscles in unilateral cleft lip and palate patients with anterior crossbite.

OBJECTIVE: To evaluate the characteristics of masticatory muscle activity in operated unilateral cleft lip and palate (UCLP) patients with anterior crossbite compared with normal individuals. SUBJECTS: Sixteen male and 13 female Chinese patients with UCLP and anterior crossbite. Fifteen male and 13 female Chinese individuals without cleft abnormalities served as a control group. DESIGN: Electromyographic activity of the masseter muscles and anterior temporalis muscles was recorded bilaterally in different mandibular positions using bipolar surface electrodes. RESULTS: Compared to noncleft controls, patients with UCLP demonstrated (1) higher activation levels of masseter and temporalis muscles in the rest position, (2) lower potential function of masseter and temporalis, (3) inharmonious activity of the masticatory muscles during mandibular border movement, (4) a higher asymmetry index of the masseter and temporalis muscles, and (5) longer silent periods of the two muscles. CONCLUSIONS: The function of masticatory muscles is different in patients with UCLP with anterior crossbite. Muscle function should be considered when evaluating cleft patients for orthodontic treatment and orthognathic surgery.

Action Potentials↗
PubMed1986

Correlations between the cross-sectional area of the jaw muscles and craniofacial size and shape.

In adult human subjects, the correlations were determined between the cross-sectional areas of the jaw muscles (measured in CT scans) and a number of facial angles and dimensions (measured from lateral radiographs). Multivariate statistical analysis of the skeletal variables in a group of 50 subjects led to the recognition of six independent factors determining facial shape, i.e., cranial base length, lower facial height, cranial base flexure and prognathism, facial width, mandibular length, and upper facial height. In 29 of these subjects, the cross-sectional areas of the jaw muscles were determined, and correlations between these areas and the scores on the above-mentioned factors were calculated. It appeared that the cross-sectional areas of temporalis and masseter muscles correlated positively with facial width, whereas the areas of masseter and both pterygoid muscles did so with mandibular length. It has been shown experimentally that a decrease in jaw muscle size in various animals likewise has an effect on facial width and mandibular length. Our results therefore support the hypothesis that in man too the jaw muscles affect facial growth and partly determine the final facial dimensions. They also hint that the role of each muscle is different.

Adult↗
PubMed2002

Capsaicin-induced muscle pain alters the excitability of the human jaw-stretch reflex.

The pathophysiology of painful temporomandibular disorders is not fully understood, but evidence suggests that muscle pain modulates motor function in characteristic ways. This study tested the hypothesis that activation of nociceptive muscle afferent fibers would be linked to an increased excitability of the human jaw-stretch reflex and whether this process would be sensitive to length and velocity of the stretch. Capsaicin (10 micro g) was injected into the masseter muscle to induce pain in 11 healthy volunteers. Short-latency reflex responses were evoked in the masseter and temporalis muscles by a stretch device with different velocities and displacements before, during, and after the pain. The normalized reflex amplitude increased with an increase in velocity at a given displacement, but remained constant with different displacements at a given velocity. The normalized reflex amplitude was significantly higher during pain, but only at faster stretches in the painful muscle. Increased sensitivity of the fusimotor system during acute muscle pain could be one likely mechanism to explain the findings.

Adult↗
PubMed1990

Structure and function of masticatory muscles in a case of muscular dystrophy.

Histologic examination of muscle biopsies and functional examination comprising electromyography and force measurements in a 19-yr-old boy with muscular dystrophy showed different wasting patterns of mandibular elevator and depressor muscles. Pronounced histopathologic changes were present in the masseter muscle, whereas pathologic findings in the anterior digastric muscle were limited to increased number of cells in slightly enlarged interfiber connective tissue. The masticatory pattern was distorted, and strength of mandibular elevator muscles was less than one third of the norm, whereas depressor strength corresponded more to reference values. This difference of muscular wasting might be caused by protective enzymes in the digastric muscle and/or functionally induced damage of the masseter. As affection from muscular dystrophy may vary greatly between the masticatory muscles, structural and functional examination should be used routinely to clarify prognosis before initiation of treatment procedures.

Adult↗
PubMed2003

Association of orofacial muscle activity and movement during changes in speech rate and intensity.

Understanding how orofacial muscle activity and movement covary across changes in speech rate and intensity has implications for the neural control of speech production and the use of clinical procedures that manipulate speech prosody. The present study involved a correlation analysis relating average lower-lip and jaw-muscle activity to lip and jaw movement distance, speed, and duration. Recordings were obtained on orofacial movement, muscle activity, and the acoustic signal in 3 normal speakers as they repeated a simple test utterance with targeted speech rates varying from 60% to 160% of their habitual rate and at targeted vocal intensities of -6 dB and +6 dB relative to their habitual intensity. Surface electromyographic (EMG) recordings were obtained with electrodes positioned to sample primarily the mentalis, depressor labii inferior, anterior belly of the digastric, and masseter muscles. Two-dimensional displacements of the lower lip and jaw in the midsagittal plane were recorded with an electromagnetic system. All participants produced linear changes in percent utterance duration relative to the auditory targets for speech rate variation. Intensity variations ranged from -10 dB to +8 dB. Average EMG levels for all 4 muscles were well correlated with specific parameters of movement. Across the intensity conditions, EMG level was positively correlated with movement speed and distance in all participants. Across the rate conditions, EMG level was negatively correlated with movement duration in all participants, while greater interparticipant variability was noted for correlations relating EMG to speed and distance. For intensity control, it is suggested that converging neural input to orofacial motoneurons varies monotonically with movement distance and speed. In contrast, rate control appears to be more strongly related to the temporal characteristics of neural input than activation level.

Acoustic Stimulation↗
PubMed1998

Mechanical hyperesthesia of human facial skin induced by tonic painful stimulation of jaw muscles.

The function of the somatosensory system in patients with painful temporomandibular disorders is still a matter of discussion. We wished to determine cutaneous sensitivity to innocuous mechanical stimuli in the orofacial region before, during (3 and 12 min) and after standardized experimental jaw-muscle pain. Twelve healthy subjects were exposed to tonic infusion of hypertonic (5%) and isotonic (0.9%) saline into the masseter muscle. All subjects experienced moderate pain with hypertonic saline, and the area of self-reported pain increased significantly from 3 min after infusion start to 12 min after infusion start (mean +/- SEM: 115+/-49%; P < 0.05). The psychophysical ratings of punctate von Frey hair stimulation were significantly increased 12 min after start of hypertonic saline infusion as compared to baseline and post-baseline ratings at the site of infusion (50+/-10%; P < 0.05) and at two adjacent facial sites (18+/-7%, 37+/-9%; P < 0.05). In contrast, isotonic saline infusion was associated with a significant decrease in ratings at post-baseline as compared to baseline ratings. The psychophysical ratings of a stroking cotton swab stimulation were not significantly affected by infusion of saline. These results in a human model of jaw-muscle pain are comparable to animal studies demonstrating increased size of cutaneous receptive fields and increased responsiveness of brain stem neurons to cutaneous mechanical stimuli. Similar hyperexcitability changes may be part of the pathophysiological mechanisms involved in painful temporomandibular disorders.

Adult↗
PubMed2006

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 approximately 150ms after the start of ThrMov when performed at moderate speed ( approximately 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'.

Adult↗
PubMed1994

Masseter and temporalis surface electromyography in patients wearing complete dentures comparing anterior and posterior occlusal concepts--a pilot study.

The activity of jaw elevator muscles (masseter and anterior temporal muscle) was studied by surface electromyography in 17 patients wearing complete dentures with anterior-canine guidance. Baseline electromyography was recorded with the dentures and compared to recordings obtained with two different splints adapted to the upper denture, one providing anterior guidance leading to immediate disclusion of the posterior teeth during any jaw movement, the other providing posterior guidance buccally on the working side and lingually on the non-working side (bilaterally balanced occlusion). Recordings were obtained during a sequence of different jaw movements: postural position, maximal tooth contact in intercuspal position, protrusive movement of the mandible (under tooth contact) and during lateral excursions, also carried out under tooth contact. Muscle activity was not significantly different as recorded with dentures only versus with the splints providing anterior guidance. However, a significant increase in activity was observed with bilaterally balanced occlusion. The results of this study in edentulous people are similar to those found in patients with natural teeth.

Aged↗
PubMed1998

Electromyographic study of the temporal, masseter and suprahyoid muscles in the mandibular rest position.

The temporal muscles (anterior position), and the masseter and suprahyoid muscles were studied electromyographically in 15 subjects with ages ranging from 18 to 35 years, showing normal occlusion (Class I of angle), complete dentition and no dysfunction of the stomatognathic system. The volunteers sat comfortably in a chair, keeping the Frankfurt plane parallel to the floor; the muscles were analysed in the mandibular resting position through a number of stages: with minimum exteroceptive stimuli, relaxation with soft music, abolition of the intrabuccal negative pressure through a plastic tube, stress provoked by an electronic game, disocclusion of posterior teeth using the occlusal splint and finally withdrawal of this device. The electromyographic results were analysed statistically. The samples, were analysed for all of the frequencies of motor units, in a 1-min period. It was found that there were statistically significant difference between the relaxation stages as compared with the withdrawal of negative intraoral pressure and mainly with the stress phase, being this only on the suprahyoid muscles, with 5% significance.

Adolescent↗
PubMed1997

Serotonergic neurons in the caudal raphe nuclei discharge in association with activity of masticatory muscles.

There is a dense serotonergic projection from nucleus raphe pallidus and nucleus raphe obscurus to the trigeminal motors nucleus and serotonin exerts a strong facilitatory action on the trigeminal motoneurons. Some serotonergic neurons in these caudal raphe nuclei increase their discharged during feeding. The objective of the present study was to investigate the possibility that the activity of these serotonergic neurons is related to activity of masticatory muscles. Cats were implanted with microelectrodes and gross electrodes. Caudal raphe single neuron activity, electrocorticographic activity, and splenius, digastric and masseter electromyographic activities were recorded during active behaviors (feeding and grooming), during quiet waking and during sleep. Seven presumed serotonergic neurons were identified. These neurons showed a long duration action potential (> 2.0 msec) and discharged slowly (2-7 Hz) and very regularly (interspike interval coefficient of variation < 0.3) during quiet waking. The activity of these neurons decreased remarkably during fast wave sleep (78-100%). Six of these neurons showed tonic changes in their activity positively related to digastric and/or masseter muscles activity but not to splenius muscle activity during waking. These data are consistent with the hypothesis that serotonergic neurons in the caudal raphe nuclei play an important role in the control of jaw movements.

Animals↗
PubMed1993

Intramuscular hemangiomas of the masseter and sternomastoid muscles.

Two cases of hemangiomas involving the masseter and sternomastoid muscle are added to the English literature. Our limited experience with these cases confirms that preoperative diagnosis and planning can be difficult. Recurrences of tumors are related to incomplete excisions although their further treatments in the final analysis depend on the adjacent structures affected. Careful individualization of treatment is therefore a necessity. Embolization is not sufficient therapy if not followed by surgery.

Adult↗
PubMed1998

The role of gingival mechanoreceptors in the reflex control of human jaw-closing muscles.

Electromyographic (EMG) experiments were undertaken to investigate the jaw reflexes evoked by activation of gingival receptors in 12 humans. EMG recordings were made from an active masseter muscle whilst ramp-plateau mechanical stimuli were applied to the gingiva. Stimuli with a constant rate of rise (0.2 N/msec) and a variable plateau force (up to 2 N), evoked a complex set of short- and long-latency inhibitory and excitatory responses. These occurred as a sequence of inhibition-excitation-inhibition-excitation, although not all of these elements were seen on every occasion. The median thresholds of these four responses ranged from 0.5 to 1 N but overall there were no significant differences between them (p > 0.05, Friedman's ANOVA). In other experiments, the same reflexes were recorded in response to application to the gingiva of 1 N ramp-plateau stimuli (5 msec rise time) and 1 N tap stimuli applied to the adjacent tooth. The application of a local anaesthetic agent to the stimulated gingiva produced reductions in the mean magnitude of almost all the responses but these were significant (p < 0.05; ANOVA) only for the long-latency inhibitions evoked by ramping the gingiva and the long-latency excitations evoked by either stimulus. It is concluded that mechanoreceptors in the gingiva can mediate long-latency inhibitory and excitatory jaw reflexes, and that these receptors may also contribute to long-latency reflexes evoked by tapping teeth. The scarcity of effects of gingival anaesthesia on the short-latency reflexes may be due to such responses being mediated by receptors deeper in the periodontium.

Adult↗