PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Masticatory Muscles”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 1,009 records · Page 56Linked to original sources
PubMed1978

A study of sensory projection from jaw muscles to the cerebral cortex in the rat.

The sensory projection from jaw muscles to the cerebral cortex have been studied in rats by electrophysiological and histochemical methods. Electrical stimulation of individual masticatory muscles elicited bilateral responses in the cortical areas 8, 10, 2, and 2a. The following pathway was postulated to mediate these cortical responses; impulses of muscle origin are conducted in turn to the trigeminal mesencephalic tract nucleus (TMT), the contralateral thalamic nucleus ventralis posteromedialis (VPM), the cerebral cortex and finally to the other cerebral cortex which is ipsilateral to the side of stimulation. The ipsilateral cortical response appeared about 5 msec later than the contralateral one and was abolished by sectioning the corpus callosum. By stimulating the cerebral cortex antidromically, the conduction time to the VPM was found to be as long as 6 msec. The conduction from the TMT to the contralateral VPM consumed a period of more than 10 msec. It was presumed to be multisynaptic, being based on the finding that horseradish peroxidase injected into the VPM could not be recovered in the contralateral TMT.

Afferent Pathways↗
PubMed1999

Cold pressor stimulation effect on hemodynamic changes following sustained isometric contraction in human jaw-closure muscles.

It is postulated that an altered adrenergic response pattern may be associated with chronic muscle pain states. To evaluate this hypothesis, one must fully understand the effect of an adrenergic activation on masticatory muscle blood flow under various conditions. This study evaluated the effect of a 12 degrees C cold pressor stimulation (a mild adrenergic activator), applied to the hand-forearm area, on intramuscular hemodynamics in the human masseter and temporalis muscles following a sustained isometric contraction. We assessed hemodynamics by measuring intramuscular hemoglobin concentration repeatedly, using a non-invasive near-infrared spectroscopy device. Measurements were taken before, during, and after a 30-second sustained 50% maximum voluntary contraction task. Fourteen healthy subjects, seven males and seven females, with no history of muscle pain in the masticatory system participated in this study. This protocol was repeated three times, but in the second trial, the cold pressor stimulation was applied to the subject during and for 5 min after the sustained contraction task. Repeated-measure analysis of variance performed on these data revealed that the peak hemoglobin concentration levels in the post-contraction recovery period were significantly reduced (between 13 and 14%) with cold pressor stimulation, both in the masseter (p < 0.001) and in the temporalis (p < 0.001) muscles. The results suggest that cold pressor stimulation produced a reduced intramuscular vasodilative response in these muscles during the immediate post-contraction period. One explanation for these results is that altering the local chemical environment of the muscle affects the adrenergic response pattern typically induced by a cold pressor stimulation.

Adult↗
PubMed2003

Myosin heavy chain isoforms of the murine masseter muscle during pre- and post-natal development.

Masticatory muscles that are derived from the branchial arches express different compositions of myosin heavy chain (MHC) isoforms during the transitional phase from suckling to mastication. To clarify the developmental changes of murine masseter muscle, the composition of MHC isoforms was examined using immunohistochemical staining and competitive reverse transcription PCR. We found that MHC1 was expressed transiently in the pre and post-natal stages. In the compositional change of isoforms, the embryonic type MHCp was expressed consistently, whereas the adult isoforms increased with the developmental process. In particular, a significant change was observed between embryonic days 14 and 16, a stage when murine facial development is conspicuous. This suggests that the development of murine masseter muscle is closely associated with facial development.

Aging↗
PubMed2004

[Bruxism--a function of the masticatory organ to cope with stress].

Bruxism is generally defined as a parafunctional clenching and grinding action between the upper and lower teeth. During this activity, extremely strong forces can be applied for time periods exceeding those of functional mastication. These biomechanical loads create many dental problems, such as abfractions, hypersensitivity, periodontal distraction, and temporo-mandibular dysfunction. Researchers studying Bruxism have long discussed psychic stress and emotional tension. It has also been indicated that an aggressive biting is associated with a significant attenuation of the stress-induced increase of nor-adrenalin turnover in the brain, of the striatal DOPAC contents and with the prevention of stomach ulcer formation in experimental animals. The concept of stress management based on the psychological background of Bruxism and the benefits attributable to masticatory muscle activity in attenuating stress-related symptoms such as stomach ulcer. The clenching and bruxing function of the masticatory organ is an emergency exit during periods of psychic overloading. Therefore, occlusion of the masticatory organ contributes significantly to an individual's ability to manage stress. Bruxism in proper dentition can be recognized as a valid system prophylaxis for all stress related diseases.

Adaptation, Psychological↗
PubMed1983

Muscles of the masticatory apparatus in two genera of hyraces (Procavia and Heterohyrax).

Subungulate hyraces are similar to the condition assumed to have characterized primitive ungulates and subungulates by virtue of their small body size, relatively unspecialized cranial and postcranial anatomy, and primitive type of lophodont dentition. The muscles of mastication of Procavia habesssinica and Heterohyrax brucei are here compared with those of other mammals, both with ungulates, as an example of more specialized mammals, and with opossums, as an example of more generalized mammals, to determine aspects of hyrax myology that represent the retention of a condition primitive for herbivorous mammals. The masticatory muscles of hyraces retain the primitive ungulate/subungulate condition in the large, complexly subdivided temporalis, and in the enlarged, pinnated, bilayered medial pterygoid. The medial pterygoid originates from the pterygoid hamulus, a condition that may also be primitive for this assemblage. The large complex superficial masseter is derived compared with the condition in ruminant artiodactyls, but may represent the condition primitive for perissodactyls. The architectural modifications of this muscle in hyraces may represent adaptations to allow a wide gape threat display. Hyraces possess a posterior belly of the digastric alone, paralleling the condition in some perissodactyls. They possess a large and complexly subdivided styloglossus, which may be a shared derived character of subungulates. Hyraces are unique among ungulates and subungulates in the extreme reduction of the anterior hyoid cornua, and may be unique among mammals in the development of paired lingual processes from the ceratohyal ossifications.

Animals↗
PubMed1983

Daily variations in occlusal contacts.

In this study the location and severity of occlusal contacts in the morning and evening on 3 separate days were recorded for 10 women. Biofeedback therapy was used after evening recordings to encourage muscle relaxation. The findings suggest that occlusion and occlusal contacts change throughout the day and depend on the physical state of the masticatory muscles and the mental state of the patient. Although this conclusion is understandable, its effects on the philosophies of occlusal rehabilitation are questionable. Further studies are needed to evaluate the significance of the contact variations in occlusal restorations placed at different times.

Adolescent↗
PubMed1989

[Frequency spectra of EMG activities and mastication muscular development].

The purpose of this study was to investigate the change of frequency components of EMG (electromyograph) signals obtained from masticatory muscles in term of the development from deciduous mixed and permanent dentition using FFT (Fast Fourie Transform) algolism. A total of one hundred and fourty subjects who had no oral dysfunction were subjected. The subjects were divided into four groups: deciduous dentition (designated as G1), early mixed dentition (designated as G2), late mixed dentition (as G3) and permanent dentition (as G4). EMG signals were taken from the right masseter and temporal muscles using bipolar surface electrodes during tooth tapping, clenching in the intercupsal position and maximum biting and EMG were recorded on magnetic tape (FM data recorder). Three parameters on the surface EMGs were chosen for the measuring points such as 1) frequency range, 2) frequency of maximum peak (peak frequency), 3) strength of maximum peak (peak magnitude). The results obtained in the present studies were summarized as follows; 1) In the frequency range, temporalis showed a higher range than masseter muscle among every group and it decreased with the dentitional development. 2) As to the peak frequency and peak magnitude, the clenching has higher frequency than tooth tapping and maximum biting, and the those differences between each group were clarified with the development. 3) Cross-powerspectrum showed that the main frequency harmonized into high frequency at every movement, while the strength of the harmony maintained a high frequency and increased with the development of the muscles. As aforementioned, EMG spectra may also reflect on to muscle activities associated with dentitional development.

Dentition, Mixed↗
PubMed2001

Electromyographic evidence of reduced muscle activity when ULF-TENS is applied to the Vth and VIIth cranial nerves.

The object of this study was to determine if the resting muscle activity of TMD patients with measured hyperactivity (EMGave > 2.0 microvolts) could be reduced by the application of ULF-TENS (Ultra-Low-Frequency-Transcutaneous Electrical Neural Stimulation) [(BioTENS) BioResearch, Inc. Milwaukee, WI]. Twenty-nine patients with resting muscle hyperactivity and ten without resting muscle hyperactivity were selected from a series of 124 consecutively diagnosed TMD patients. Electromyographic records were taken bilaterally (with the mandible at rest) from the superficial masseter, anterior temporalis, anterior digastric, and posterior temporalis muscles before and after the application of ULF-TENS. The EMG data were averaged. For the 85 muscles that were found initially to exceed the usual cutoff of 2.0 microvolts, means and standard deviations were calculated. The "before TENS" levels were: mean = 3.353 +/- 1.44227 and the "after TENS" values were: mean = 1.844 +/- 0.92421. Using a student t-test, we found the difference between the before and after levels significant (p < .0005). Additionally, means and standard deviations were calculated for each muscle (Ta, Mm, etc.) separately and also found to be significantly different (before Vs after TENS). In these "hyperactive" patients, the nonhyperactive muscles were also pooled, the means calculated before (mean = 1.21 +/- 0.456) and after (mean = 1.00 +/- 0.345) TENS and found to be significantly different (p < 0.01). For the ten patients exhibiting no muscle exceeding the 2.0 microvolt cutoff (mean = 1.08 +/- 0.415), no significant change (in levels) was observed after ULF-TENS (mean = 0.96 +/- 0.359; p > 0.88); however, when we calculated the "paired difference," we found a significant reduction, albeit very slight, in these patients' muscles, too. We conclude that ULF-TENS has an activity-reducing effect on the resting EMG levels of both hyperactive and relaxed muscles. It also appears that while the > 2.0 microvolt cutoff is useful for identifying patients that are hyperactive at rest, it does not identify complete relaxation of masticatory muscles.

Adult↗
PubMed1987

Sensory and motor integration during mandibular function.

The subject of pain is intimately related to that of mandibular function. It is now clear that certain types of temporomandibular disorders, particularly myofascial pain dysfunction, result, in part, from rhythmic muscle activity produced by parafunctional oral habits such as diurnal or nocturnal bruxism. Furthermore, in addition to phasic hyperactivity, evidence also suggests that masticatory muscles of patients with MPD are tonically hyperactive. The pain associated with such hyperactive musculature prompts many patients to seek professional help. This article provides an updated historical review of one important aspect of mandibular function and gives insight into the general "state of the art."

Animals↗
PubMed1990

Prevalence of signs and symptoms of craniomandibular disorders in tinnitus patients.

One hundred two tinnitus patients were examined to determine the prevalence of signs and symptoms of CMD. The examination comprised determination of the anamnestic and clinical dysfunction indices according to Helkimo; assessment of the dentition, occlusal factors, and signs of parafunctions; and accomplishment of a tension test. Patients also answered a questionnaire concerning the presence and frequency of CMD symptoms and headaches, as well as influence on tinnitus by mandibular movements, by pressure applied to the TMJ, or by dental therapy. Frequent headaches and fatigue/tenderness in jaw muscles were more prevalent in tinnitus patients than in epidemiologic samples, as was the prevalence of clinical findings of pain on palpation of masticatory muscles, impaired mandibular mobility, and signs of parafunctions. About one-third of the patients reported influence on tinnitus by mandibular movements and/or pressure applied to the TMJs. A theoretic model of causal connections between tinnitus and signs and symptoms of CMD in some tinnitus patients is suggested.

Adolescent↗
PubMed1990

Enzymes of transmitter and energy metabolism in rat middle ear and extraocular muscles.

To further investigate the peculiar characteristics of the middle ear and extraocular muscles, compared to the extensively studied skeletal muscles of the limbs, activities of enzymes of transmitter and energy metabolism were measured in homogenates of these muscles from albino and pigmented rats. These activities were compared to those for a masticatory muscle and for three hindlimb muscles chosen for their preponderance of either slow oxidative, fast glycolytic, or fast oxidative glycolytic fibers. Activities of the neuromuscular transmitter enzymes choline acetyltransferase and acetylcholinesterase were relatively very high in the extraocular and middle ear muscles. The activity of malate dehydrogenase, an enzyme of oxidative energy metabolism, was as high in the extraocular, masticatory and stapedius muscles as in the oxidative hindlimb muscles, but was lower in tensor tympani. The activity of lactate dehydrogenase, an enzyme of glycolytic energy metabolism, was remarkably low in both middle ear muscles. The results are consistent with high innervation density in the extraocular and middle ear muscles, and highly oxidative metabolism in the extraocular and stapedius muscles. Metabolic differences between the stapedius and tensor tympani suggest a relatively more active role for the former in the function of the rat middle ear.

Animals↗
PubMed2001

Prediction of demand for treatment of temporomandibular disorders.

Baseline (BL) data on signs and symptoms characteristic of temporomandibular disorders (TMDs) were analysed in 67 young non-patients participating as controls in a clinical trial. Data on the incidence of demand for treatment of TMD were collected during the 4-year follow-up period, and, by means of a mailed questionnaire, during an additional 2 years. The variables analysed included palpation and auscultation of the joints, palpation of the muscles of mastication, experience of joint sounds, of pain on jaw movements, of ear symptoms, awareness of a clenching habit, and frequency of headache. A present-absent dichotomy was applied throughout. Palpation tenderness of masticatory muscles was significantly (P=0.02) more often present at BL in those who subsequently requested treatment than in those who did not. The same was true of the combination of palpatory tenderness and clenching habit (P=0.007), whereas the clenching habit alone failed to show a significant difference (P=0.06). However, the predictive values remained too low to be clinically useful, with a possible exception of the negative predictive value of muscle tenderness. The findings indicate that the variables conventionally used to describe the functional status of the masticatory system are at best of modest value in the estimation of individual risk of TMD in healthy young subjects.

Adolescent↗
PubMed1999

Motor coordination in a multi-muscle system as revealed by principal components analysis of electromyographic variation.

The variation in electromyographic output of twelve trigeminal muscles of the rabbit was studied to test the hypothesis that they are under the control of a small number of independent neural factors. Jaw muscle electromyograms (EMGs) of eight animals were recorded in 95 chewing sequences, each consisting of 40-75 chewing cycles. The within-sequence correlations of the EMG burst amplitudes (integrated per cycle) and burst onsets were calculated between the muscles. The correlation matrix was subjected to a principal components analysis. This method aims at describing the variation in EMG amplitude and timing by means of the smallest possible set of newly defined variables, or principal components. Of the variation in EMG amplitude values of the twelve muscles, 75-90% could be accounted for by only three principal components. Each principal component was characterized by a group of muscles with high mutual positive correlations; they had zero correlation with other principal components. The first component represents the jaw closers: most of the bilateral masseter and the medial pterygoid muscles. The second represents the openers: the bilateral digastric and lateral pterygoid muscles. This demonstrates the tight control of both the jaw openers and closers, each by a single neural factor; these two factors are independent of one another. They most likely originate from the specific inputs from primary afferents to the opener and closer motoneurons. Unexpectedly, a third independent principal component appeared to control the closing activity of the non-chewing side, posterior deep masseter muscle. It was hypothesized that this muscle acts independently of the other closers to disengage the teeth and resets the jaw for a new chewing cycle. Principal components analysis of variation in timing of EMG onset revealed a grouping of all masticatory muscles in a single cluster, independent of EMG amplitude. This supports the hypothesis that timing and amplitude of masticatory EMG patterns are controlled independently.

Animals↗
PubMed2005

Fatigue and damage to the masseter muscle by prolonged low-frequency stimulation in the rat.

This study aimed to examine peripheral fatigue and the resultant damage to the masseter muscle due to prolonged low-frequency stimulation. Thirty male rats were divided into S1, S2, S4, Dantr and Sham groups. The left masseters were used as experimental muscles. A pair of stimulation electrodes was placed on the left masseter. A stimulating session included rectangular electric pulses of 18 Hz (5 mA, approximately 18 V, 0.7 ms) for 2 h with a 3 min rest period between sessions. One session was given to the S1 group, two sessions to the S2 group and four sessions to the S4 group. Four sessions were given to the Dantr group with administration of dantrolene to determine any artifacts of the electrical current. No electric stimulation was given to both side masseters in the Sham group or to the control (right) masseters in the other groups. In each session, jaw-closing force increased to a peak within 1 min and attenuated to the steady force. The peak force decreased as the session advanced in each group. Both side masseters were dissected after the stimulations and examined histologically. The experimental masseter was significantly heavier than that of the controls in the S1, S2 and S4 groups, and the muscle fibres showed irregularity of size and shape with enlargement of interstitial space and infiltration of mononuclear cells into the fibres. However, no such histological change was observed in the Dantr and Sham groups. It was confirmed that fatigue and damage to muscle fibres could be induced in masticatory muscles by prolonged low-frequency stimulation.

Animals↗
PubMed2006

Pathophysiology of the Eustachian tube--relevant new aspects for the head and neck surgeon.

OBJECTIVES: The impact of cranio-maxillofacial procedures upon Eustachian tube function is still largely unknown. The aim of this presentation is to depict new aspects of Eustachian tube function and to demonstrate its importance to cranio-maxillofacial surgery. METHODS: Two different groups of patients were examined both clinically and by MRI of the Eustachian tube region. One of these groups comprised 15 adult patients with a history of cleft palate; another consisted of 32 patients with a history of a so-called patulous Eustachian tube. RESULTS: Clinical and MRI-findings revealed that the problem of persistent chronic middle ear disease with cleft palate patients depends crucially on the integrity of the pterygoid hamulus and of the tensor veli palatini muscle after cleft palate repair. The masticatory muscles on the other hand also play an important role in Eustachian tube function in non-cleft patients. CONCLUSION: The maxillofacial surgeon should be aware that he holds a key position for preventing as well as treating Eustachian tube pathophysiology.

Adolescent↗
PubMed2003

[Use of botulinum toxin type A in neuro-ORL].

Dystonia is the result of abnormal contractions of muscles, which may disturb activities between agonist and antagonist muscles. Since synchronization of laryngeal and masticatory muscles is highly necessary to allow opening and closure of the larynx or the mouth, expression of dystonia is especially exhibited. Focal laryngeal dystonia may disturb phonation, but also breathing or swallowing, which may be difficult to identify. In ORL, the botulinum toxin is used to treat focal dystonias, especially laryngeal (spamodic dysphonia being predominant) and oromandibular dystonias. Beside these indications, intracutaneous injections of botulinum toxin may be helpful in Frey's syndrome in patients with gustatory sweating; injections in the upper esophageal sphincter are also performed in cricopharyngeal dysphagia although this indication is mainly controversial.

Botulinum Toxins, Type A↗