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 1,243 records · Page 69Linked to original sources

PubMed2006

Effect of controlled masticatory exercise on pain and muscle performance in myofascial pain patients: A pilot study.

The aim of this study was to test the hypothesis that strengthening masticatory muscles using a controlled chewing exercise protocol improves muscle function, as evaluated quantitatively by electromyogram, and reduces pain at rest and during function. The study included 20 patients diagnosed with myofascial pain according to the Research Diagnostic Criteria for Temporomandibular Disorders with low masseter volume increase during maximal clench. The exercise group (ten patients) was subjected to a controlled gum chewing exercise protocol for eight weeks: the control group (ten patients) received only support and encouragement. Patients were examined at the beginning and at the end of the experiment which included an electromyogram (EMG) to assess muscle performance, masticatory muscle tenderness to palpation, mouth opening range, subjective anamnestic indices to evaluate pain perception and pain relief, and chewing tests. The EMG showed that the masticatory muscle exercise did produce objective physiologic results. In the exercise group, a significant increase was found in the electric muscle activity of the masseters during maximal voluntary clench (p=0.007). The exercise group showed significant reduction in pain during rest, pain during the chewing test, and a disability score. At the end of the study, a difference between the two groups was shown in the Pain Relief Scale: significantly greater pain relief was found in the exercise group as compared to the control group (p=0.019). For all other clinical parameters, there was no difference between the two groups or interaction between time and treatment. The results of this study seem to be equivocal. Additional experiments on larger population groups with extended chewing protocols are necessary before a more substantial conclusion can be reached.

Adult↗

PubMed2004

Mental stress-induced physiological changes in the human masseter muscle.

The effect of a long mental stress on the hemodynamics of masticatory muscles has not been investigated to date. We hypothesized some hemodynamic and electromyographic changes in jaw-closure muscles related to sympathetic nervous system activity. While healthy adult female volunteers performed a two-hour mental stress task, electromyographic activity of the temporal and masseteric muscles was recorded, and hemodynamic changes of the masseter muscle were measured non-invasively. Autonomic function was assessed by heart rate spectral analysis. Integrated electromyographic activity of the temporalis muscle, but not the masseter muscle, showed an increase that coincided with the increase in sympathetic nervous activity. In the masseter muscle, despite little change in integrated electromyographic activity, notable changes were found in hemodynamic parameters. These results suggest that hemodynamics of jaw muscles is susceptible to mental stress, implying a potential role in the etiology of jaw muscle dysfunction associated with mental stress.

Adult↗

PubMed1990

Body posture and hand strength of patients with temporomandibular disorder.

The aim of this study was to observe the difference between patients of craniocervical muscle pain and nonpatients in head-neck posture, masticatory muscle activity, and the force exerted by the hand. Fifty-one patients and 28 nonpatients were observed. The electric activity of the masseter muscles was recorded when the subjects were doing pinching or grasping with the jaw in positions of rest, clenched, and clenched with gauze. Measurement of right and left tilting or extension and flexion of the head and neck was made from photographs of frontal and lateral views. It was found that the pinching and grasping force was much stronger in men than in women and in nonpatients than in patients with pain. The pinching and grasping force was more powerful with the teeth clenched. Clenching with gauze did not increase, but more often decreased the strength of the hand. The activity of the masseter muscle during clenching was about 10 to 26 times that of the resting activity. The activity decreased slightly when clenching with pinching or grasping. Patients were more likely to have a stretched neck with more extension of the head. Their masseter muscle activity and hand force were significantly weaker than that of the nonpatients.

Adult↗

PubMed2005

Comparative data on facial morphology and muscle thickness using ultrasonography.

The purpose of this investigation was to measure the thickness of the masseter, levator labii superioris, and zygomaticus major muscles; to examine the reproducibility of ultrasonographically measured muscle thickness; to evaluate the association between facial and masticatory muscle thickness and vertical facial pattern; and to test whether the variation in muscle thickness is related to the variation in the body mass index (BMI) of different individuals. The thickness of the masseter, levator labii superioris and zygomaticus major muscles was measured bilaterally by ultrasonography in 47 (23 females, 24 males) healthy, fully-dentate young adults who volunteered for the study. The measurements for each individual were performed twice for the masseter muscle: during relaxation and during maximal clenching. Standardized lateral cephalograms of the subjects were traced to determine their facial morphology. The data obtained from the lateral cephalograms were used to divide the subjects into three groups according to their vertical facial pattern: low angle (n = 14), high angle (n = 17) and normal (n = 16). In the low angle group, the mean masseter muscle thickness was 15.20 (+/- 1.90) mm under relaxed conditions and 16.31 (+/- 2.18) mm during maximal clenching. In the high angle group, the respective measurements were 13.29 (+/- 2.52) mm and 14.72 (+/- 2.63) mm. In the vertically normal group, they were 13.56 (+/- 1.95) mm and 14.57 (+/- 1.83) mm. There was no relationship between vertical growth of the face and the thickness of the investigated muscles of facial expression. Masseter muscle thickness was found to be significantly correlated to vertical facial pattern and BMI, showing that individuals with a thick masseter had a vertically shorter facial pattern, whereas the muscles of facial expression showed no relationship with vertical facial pattern.

Adult↗

PubMed2000

The relationship between dentofacial morphology and the isometric jaw-opening and closing muscle function as evaluated by electromyography.

The purpose of this study was to clarify the relationship between the dentofacial morphology and masticatory muscle function in both isometric jaw-opening and closing. The subjects consisted of 26 male adults without masticatory dysfunction. Electromyograms were obtained from the digastric and masseter muscles to evaluate their muscle activities. The sum energy, median frequency, and equilibrium index were calculated as parameters of the muscle activity. A correlation analysis was performed between the parameters for the muscle activity and the dentofacial morphology on lateral roentgenographic cephalograms. The sum energy in the jaw-closing muscle showed a significant relationship with the gonial angle, mandibular length, and facial height, but not in the jaw-opening muscle. A median frequency in the jaw-opening muscle showed a significant relationship with size and position of the mandible, and also that in the jaw-closing muscle with the mandibular plane angle, facial height, and mandibular body length. Furthermore, the equilibrium index of the median frequency was related to the facial height, mandibular length, and inclination of the mandibular incisor. In conclusion, the dentofacial morphology was found to be closely related to the muscle activity not only of the jaw-closing muscle but also of the jaw-opening muscle during isometric muscle contraction.

Adult↗

PubMed1998

Electromyographic analysis of oral habituation in rat pups.

Rat pups show decreases in mouthing activity in response to a series of repeated oral infusions of a diet. This decrease in mouthing activity has been termed "oral habituation" and these changes have been readily recorded with simple behavioral observations. Oral habituation appears to be a component of satiety in young rats. In the present study, to more specifically characterize changes in motor response topography during habituation in muscle groups used for mastication, mouthing activity was recorded by implanting fine wire electromyographic electrodes in the superficial masseter, anterior digastric, sternohyoideus, and genioglossus muscles of 12-day-old rat pups. During testing, pups received a series of brief oral infusions of a 10% sucrose diet delivered through an oral cannula. The results demonstrated that mouthing activity as observed and scored behaviorally was highly correlated with mouthing behavior recorded by EMG, with oral habituation distinctly emerging in both measures. In addition, the pattern of motor activity in the four masticatory muscles changed during the course of oral habituation. Within the minute following a single infusion, the cycle frequency, duration of activity, and relative onset time of activity in the four muscles changed. In addition, across the course of habituation, both cycle frequency and relative onset times of muscle activity changed. These results demonstrate the general reliability of behavioral observations of masticatory motor activity in young rats and provide further information on how the pattern of activity of muscles involved in the mouthing motor pattern is altered during the course of oral habituation.

Animals↗

PubMed1989

Modifications of masticatory behavior after trigeminal deafferentation in the rabbit.

Bilateral trigeminal deafferentation was performed in the rabbit in order to assess the role of orofacial inputs in regulation of the pattern of jaw movements during chewing. After bilateral combined section of the maxillary and inferior alveolar nerves, the animals did not eat food by themselves in the first postoperative week. However, they could chew and swallow when food was inserted into the mouth by an experimenter. The pattern of jaw movements and associated EMG activities of masticatory muscles during chewing were modulated remarkably by deafferentation. These modifications include 1) decrease in the horizontal excursions of the mandible at the power phase, 2) decrease in the maximum gape, 3) insufficient occlusion at the power phase (or increase in the minimum gape), 4) irregular patterns of jaw movements, 5) facilitation of the chewing rate, 6) increase in the number of chewing cycles in a masticatory sequence (the process from acceptance of food to swallowing), and 7) decrease in jaw-closing muscle activities. The findings indicate that deafferentation of the trigeminal sensory branches reduced masticatory force. On the other hand, no significant change was seen in the animals with disruption of cutaneous sensations of the face due to bilateral section of the infraorbital and mental nerves. Intraoral sensations rather than extraoral sensations may thus be important for regulation of masticatory force and jaw movements during chewing. Jaw movements during chewing were also analyzed in the animals with either bilateral ablation of the cortical masticatory area (CMA) or bilateral lesion of the ventral posteromedial nucleus (VPM) of the thalamus in order to examine whether profound effects of trigeminal deafferentation are produced via the transcortical loop. The animals with lesion of either the CMA or VPM demonstrated disturbances in feeding behavior, including the dropping of ingested food from the mouth, elongation of a masticatory process, reduction in the chewing efficiency, etc. However, the pattern of jaw movements during chewing were essentially similar to that in the preoperative period. These results do not necessarily deny a contribution of the CMA to regulation of jaw movements but suggest that the transcortical feedback loop via the CMA and thalamic VPM nucleus would not primarily be responsible for pattern formation of jaw movements during chewing in the rabbit. Probably, the sensory feedback via the transcortical loop may indirectly facilitate activities of the brain stem CPG, which facilitates the chewing rhythm or enables masticatory sequences to be conducted smoothly.

Afferent Pathways↗

PubMed1989

[Frequency analysis of the EMG power spectrum of the anterior temporal and masseter muscles in children and adults].

For the investigation of the functional change of the masticatory muscles along with growth and development, the frequency analysis of the EMG power spectrum was carried out. The subjects were 6 children (5 males and 1 female) with full deciduous dentition (Hellman's dental age IIA) aged 4.5 +/- 0.2 years and 6 adults (4 males and 2 females) with full permanent dentition aged 27.7 +/- 3.8 years. EMG signals were recorded bilaterally by means of bipolar silver surface electrodes from the anterior temporal and masseter muscles when the subjects were chewing chewing gum or performing maximum clenches in the intercuspal position. A fast Fourier transform (FFT) algorithm was used to obtain the power spectrum of the EMG signal. As the total power value from 62.5 to 1000 Hz was 100 per cent, the mean frequencies at 25, 50, 75 and 90 per cent of the cumulative power were calculated. The results were as follows: 1. The mean frequencies at each ratio of the cumulative power were age-dependent and EMG power spectrum patterns significantly shifted to lower frequencies in the muscles of the adults. 2. No statistically significant differences between the chewing and clenching, the anterior temporal and masseter muscle and the left and right side were observed in each group.

Adult↗

PubMed1997

Regulation of masticatory force during cortically induced rhythmic jaw movements in the anesthetized rabbit.

To examine the relationships between masticatory force, electromyogram (EMG) of masticatory muscles, and jaw movement pattern, we quantitatively evaluated the effects of changing hardness of a chewing substance on these three variables. Cortically induced rhythmic jaw movements of a crescent-shaped pattern were induced by electrical stimulation of the cerebral cortical masticatory area in the anesthetized rabbit. The axially directed masticatory force was recorded with a small force-displacement transducer mounted on the ground surface of the lower molars. EMGs were recorded from the masseter and digastric muscles simultaneously with jaw movements. Five test strips of polyurethane foam of different hardness were prepared and inserted between the upper molar and the transducer during the movements. The peak, impulse, and buildup speed of the masticatory force increased with strip hardness, whereas duration of the exerted force did not vary with strip hardness. The integrated activity and duration of the masseteric EMG bursts also increased with strip hardness. The integrated EMG activity of the digastric bursts was weakly related to strip hardness, whereas the duration was not. The minimum gape increased with strip hardness, but the maximum gape did not. The horizontal excursion of the jaw did not vary in a hardness-dependent manner, although it was greater in the cycles with strip application than in the cycles without strip application. Deprivation of periodontal sensation by cutting the nerves to the teeth reduced the buildup speed of the force, maximum gape, net gape, and horizontal jaw movements. The denervation also elongated the force duration and that of masseteric EMG bursts. However, the rate of the hardness-dependent changes in the above parameters did not alter after denervation. The latency of the masseteric EMG response to strip application was evaluated before and after denervation. In both conditions, it was > or = 6 ms in approximately 70% of the cycles and <6 ms in the remaining approximately 30%, which cannot be explained by a simple reflex mechanism. On the basis of the analysis of correlation coefficients, the masseteric integrated EMG seemed to be a good indicator of the peak and impulse of the masticatory force both before and after denervation. We conclude that periodontal afferents would be responsible for a quick buildup of masticatory force and that afferents other than those from periodontal tissue would contribute to the hardness-dependent change of masticatory force during cortically induced rhythmic jaw movements.

Animals↗

PubMed1998

Oxidative capacity of rat masseter muscle after implantation of thyrotropin-releasing hormone microspheres in proximity to trigeminal motoneurones.

Earlier work has shown that two important consequences of implanting thyrotropin-releasing hormone (TRH) microspheres near motoneurones within the trigeminal motor nucleus of actively growing rats are increased muscle mass and a darkening of the implant-side masticatory muscles. These phenomena have been associated with altered neuromuscular activity patterns and biomechanical forces that directly influence craniofacial growth and development. Now, whether the implantation of TRH microspheres in proximity to trigeminal motoneurones would affect the oxidative capacity of the implant-side masseter muscles was investigated. Cytochrome C oxidase (COX) assays were carried out for both implant- and non-implant-side masseters of TRH (n = 5) and blank microsphere (n = 6) Sprague-Dawley rats after stereotactic surgery at 35 days of age. Analyses of both groups at 14 days post-implantation revealed that the COX activity levels of implant-side masseters in TRH-implanted rats was significantly (P< or =0.05) greater than that of non-implant-side masseters; rats implanted with blank microsphere exhibited no significant difference between implant- and non-implant-side masseter COX activity levels. The stated null hypothesis was therefore rejected. These data suggest that TRH implants in proximity to trigeminal motoneurones effect increased oxidative capacity of the masseter muscle as measured by COX activity.

Animals↗

PubMed1996

Development of the motor endplates in the masseter muscle in the human fetus.

The development of the motor endplate (MEP) and the structure of the masseter muscle in the human fetus were examined by light and electron microscopy. At 12 weeks of gestation, the masseter muscle was composed mostly of irregularly-arranged myotubes. The number of muscle fibers increased while that of the myotubes decreases during development. After 28 weeks of gestation, the masseter muscle was composed only of muscle fibers, and these fibers rapidly increased in size in comparison with those prior to 28 weeks of gestation. The MEP appeared during the first 12 weeks of gestation, and were of an undeveloped simple type, with only one axon branch. After 20 weeks of gestation, MEPs were classified as complex or simple types in terms of the branching of the axons. The complex type of MEP was found in muscle fibers of large diameter, while the simple type was found in muscle fibers of small diameter. Schwann-like cells appeared at the surface of the MEP. After 28 weeks of gestation, only the complex type was found in the masseter muscle. These results suggest that, the development of the MEP is closely related to the development of muscle, and that the timing of the development of the masticatory muscles differs from that of other skeletal muscles, such as those in the trunk and limb.

Embryonic and Fetal Development↗

PubMed1990

Congenital myasthenia associated with facial malformations in Iraqi and Iranian Jews. A new genetic syndrome.

Fourteen Jewish patients from 10 families of either Iraqi or Iranian origin with congenital myasthenia had associated facial malformations which included an elongated face, mandibular prognathism with class III malocclusion and a high-arched palate. Other common features were muscle weakness restricted predominantly to ptosis, weakness of facial and masticatory muscles, and fatigable speech; mild and nonprogressive course; response to cholinesterase inhibitors; absence of antibodies to acetylcholine receptor; decremental response on repetitive stimulation at 3 Hz but no repetitive compound muscle action potential in response to a single nerve stimulus. This newly recognized form of congenital myasthenia with distinctive ethnic clustering and associated facial malformations is transmitted as an autosomal recessive disorder. The facial abnormalities may be secondary to the neuromuscular defect or may be primary and unrelated. Further studies are needed to elucidate the defect in neuromuscular transmission responsible for the pathogenesis of this syndrome.

Adolescent↗

PubMed1995

[Experimental investigation on mouse masseter by means of denervation].

Histochemical and electron microscopic observations were made on normal and denervated masseter muscles of mice to elucidate differences of characteristics between the masticatory muscles and other skeletal muscles. The three types of muscle fibers were classified by means of Succinic dehydrogensae (SDH) reaction. In masseter muscles of normal adult mice, the three types of fibers, that is, high SDH activity fibers, intermediate SDH activity fibers and low SDH activity fibers, were recognized. More oxidative fibers in the deep portion of masseter muscles were found than that in the superior portion, which suggest that each portion has its own functional role. It is generally believed that denervation gradually causes atrophy in skeletal muscles. On the other hand, denervated masseter muscles of mice clearly showed different reactions which had two phases. In the first phase right after denervation, many masseter muscle fibers were degenerated, necrosed and regenerated. A few weeks later, in the second phase, muscle fibers remained immature, denervation atrophy was occurred, and dense connective tissue was proliferated. The other side of nondenervated masseter muscle was not influenced by denervated ones.

Animals↗

PubMed1998

[Evaluation of the treatment effect for bruxism by using myomonitor and occlusal splint].

OBJECTIVE: To evaluate the treatment effect of bruxism by using myomonitor and occlusal splint therapy. METHODS: By using EMG, audiocontrolled recorder and myollectronic recording device to record and analyse the muscles functional state before and after treatment. RESULTS: Splint therapy was more effective than the myomonitor did, such as teeth grinding stopped in 12 cases to 1 case, grinding time decreased in 13 cases to 10 cases and no significant effect in 2 cases to 17 cases. SPD and V/T curve slope of muscles decreased. CONCLUSION: This indicates that the functional state of masticatory muscles got improved. Splint therapy is one of the effective treatment method for bruxism.

Adult↗

PubMedDate not supplied

[Oto-vestibular symptoms in patients with temporomandibular joint dysfunction. Electromyographic study].

The authors analyse the otovestibular symptoms (acoupheny, muffled hearing, vertigo, hypoacusia, otalgia) present among other symptoms of craniomandibular dysfunctions. A number of hypotheses have been advanced regarding the etiopathogenesis of these symptoms, but all stem from three theories. The first theory is based on the possibility of a mechanical transmission of force from the temporomandibular joint to the middle ear by the discomalleolar ligament. Another theory hypothesises the possible direct irritation by the condyl on the auriculotemporal nerve. The most widely credited etiopathogenetic theory, which is examined in this study, is that the hypertone of the tensor muscle of the tympanum and the tensor muscle of the velum palatinum, which are innervated like the masticatory muscles of the mandibular branch of the trigeminal nerve is the effect of these same muscles' hypertone. A group of 53 adult patients was selected to verify this theory. All patients were receiving treatment for dysfunctions of the temporomandibular articulation. Initial data were collected relating to the prevalence of each of the otovestibular symptoms studied; each patient then underwent computerised electromyographic analysis while the right and lefthand masseter and temporal muscles were resting. All tests were performed by the same operator. When analysing the results, patients were divided into two groups: one group contained those patients who had no symptoms relating to the ear, and the other contained patients with at least one symptom relating to the ear. Moreover, the group of symptomatic patients was divided into subgroups of patients with 1, 2, 3, and 4 of the symptoms studied. The mean electromyographical values for each muscle examined were then compared. The following results were obtained: 67.9% of subjects examined presented at least one otovestibular symptom; the symptom that was most frequently found was the feeling of muffled hearing (41.5%), followed by otalgia and vertigo; the prevalence of otalgia was much lower (7.5%). The most interesting finding emerged from a comparison between electromyographical values in patients suffering from otovestibular symptoms and the asymptomatic group. There was no significant difference in this series between this two groups, and the mean electromyographical value was higher in the group of asymptomatic patients.

Adult↗

PubMed2004

Electromyographic evaluation of masticatory function in denture wearers in related to existing occlusal support.

The aim of this study was to clarify the relationship between partially edentulous pattern and the masticatory function in removable partial denture wearers. Eighty eight removable partial denture wearers and 7 subjects with intact dentition volunteered for this study. Using the Eichner's index, all subjects were divided into 6 groups. Electromyographic (EMG) activities of the masticatory muscle were recorded during chewing a piece of raw carrot. The masticatory function was analyzed by using the variation coefficient (VC) of the time parameter of EMG interval recorded during mastication. The association of the VC with group classification based on Eichner's index was analyzed using analysis of covariance with gender and age as the covariates. The result of the analysis revealed that the VC was significantly associated with group classification and the patients in groups without posterior occlusal supports exhibited significantly higher VC values than those in groups with posterior occlusal supports. These findings suggested that the reduced function in patients without the posterior occlusal contacts was difficult to attain improved and satisfactory outcome with removable partial dentures and that there is a significant need for posterior occlusal support for the preservation of masticatory function.

Adult↗

PubMed2002

Coordination between the masticatory and tongue muscles as seen with different foods in consistency and in reflex activities during natural chewing.

To study the coordination between the masticatory and extrinsic tongue muscles during natural chewing, electromyographic activities in the digastric (Dig) as a jaw opener, the masseter (Mas) as a jaw closer, the genioglossus (Gg) as a tongue protruder, and the styloglossus (Sg) as a tongue retractor as well as jaw movement trajectories were recorded while rabbits chewed soft, hard, and very hard foods. The Dig and Gg were active in the jaw-opening phase (OP active group), and the Mas and Sg were active in the jaw-closing phase (CL active group). Food consistency affected differently on the duration of burst activities between the muscle groups, i.e. in the CL active group, the duration was longer for the harder food, while there was no difference in the duration of the OP active group among the foods. During hard food chewing in particular, we confirmed our recent findings that reflexly-induced short but large bursts of activity could be documented in the Dig during the jaw-closing phase. Similar short bursts were also documented in the Gg as with the Dig in this study. Inhibitory periods were often observed in the Mas with the Dig short burst and were also observed in the Sg along with the Gg short burst; however the inhibitory effect in the Sg was less pronounced. These findings suggest that: (1) both masticatory and extrinsic tongue muscles are active in a well-coordinated manner during stable chewing, but that (2) reflex effects on antagonistic muscles (i.e. Dig vs. Mas in the masticatory muscles, Gg vs. Sg in the tongue muscles) evoked by tooth contact during chewing may not be analogous between the two muscle groups.

Animal Feed↗

PubMed1991

A comparative study of mastication between complete denture wearers and dentate subjects.

A computer system was used for simultaneously collecting and processing mandibular movements and the myoelectric activities of the masticatory muscles of 15 dentate subjects and 11 complete denture wearers. The displacement, velocity, cycle of mandibular movements, and the muscular mean potentials were indices in observing mastication. A good complete denture should perform with physiologic characteristics, and restore masticatory function and oral health. The kinetic energy from the velocities of lateral and vertical directions can serve for the chewing and comminution of food, but lateral comminution may affect denture retention. The mean myoelectrical potentials of the mandibular elevator muscles of complete denture wearers tend to increase at the opening phase; however, the potentials decrease at the closing phase.

Adult↗