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 739 records · Page 41Linked to original sources

PubMed1994

Pathophysiology of hemimasticatory spasm.

Two patients aged 21 and 50 years presented with facial hemiatrophy and unilateral spasms of the masticatory muscles. Masticatory muscle biopsy showed normal findings in both patients and facial skin biopsy specimens only showed atrophy, although morphoea (localised facial scleroderma) had been diagnosed nine years previously in the second patient. The involuntary movements consisted of brief twitches and prolonged contractions clinically and electromyographically similar to those of hemifacial spasm and cramps. The jaw jerk and the silent periods were absent in the affected muscles. Direct stimulation of the muscle nerve and transcranial stimulation of the trigeminal root demonstrated slowing of conduction and after-activity due to autoexcitation. Observations in other reported cases and these two patients suggest that hemimasticatory spasm is produced by ectopic activity secondary to focal demyelination of the trigeminal motor nerve fibres. The proposed cause of the neuropathy is focal damage to the masticatory nerves caused by compression, possibly resulting from the deep tissue changes that occur in facial hemiatrophy.

Adolescent↗

PubMed2002

Task-related electromyographic spectral changes in the human masseter and temporalis muscles.

The masticatory muscles differ in their fiber type composition. It can therefore be expected that their electromyographic (EMG) power spectra will differ during the performance of different bite force tasks. In the present study, surface EMG activity was picked up from the masseter and from the anterior and posterior temporalis muscles of nine adult subjects. At a bite force level as low as 25 N, the mean power frequency (MPF) values of the posterior temporalis were significantly lower than those of the masseter and anterior temporalis. The MPF values of the masseter muscles decreased with an increase of bite force magnitude, whereas the MPF values of the anterior and posterior temporalis did not change significantly. The MPF values were significantly influenced by the direction of bite force. The observed changes of MPF are possibly related to the recruitment of different fiber types, and support the concept that the masticatory muscles behave heterogeneously.

Adult↗

PubMed1987

Enzyme-histochemical differences in fibre-type between the human major and minor zygomatic and the first dorsal interosseus muscles.

Human masticatory muscles, innervated by the trigeminal nerve, differ in fibre-type composition from limb and trunk muscles, but the anterior and the posterior belly of the human digastric muscle, innervated by the trigeminal and facial nerves, respectively, do not. The major and minor zygomatic muscles from adult males, which originate from the second branchial arch and are supplied by the facial nerve, were analysed enzyme-histochemically and compared with the first dorsal interosseus hand muscle, which has spinal innervation and, like the masticatory and facial muscles, a large cortical representation. Both zygomatic muscles had a marked predominance of type II fibres, the minor one having the largest proportion (89.1 per cent) ever reported in human skeletal muscle. Besides type I, IIA, IIB, and a few type IIC fibres, there was a large group with an ATPase reaction at pH 4.6, between that of type IIA and type IIB, and termed IIAB. This fibre-type profile may reflect a special isomyosin composition. Type I and II fibres were of about equal diameter, corresponding to that of type I fibres in the masticatory muscles. Individual and intra-muscular variability in fibre size and shape was considerable. The unusually high frequency of type II fibres in the zygomatic muscles suggest that they have fast-contraction properties and relatively large motor units, and therefore are poorly adapted to finely-graded movements. The absence of muscle spindles supports this view. The hand muscle had a chequer-board pattern of type I, IIA and IIB fibres, similar to that of large limb and trunk muscles, with no difference between its two heads.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗

PubMed1979

Occurrence and distribution of muscle spindles in masticatory and suprahyoid muscles of the rat.

The occurrence and distribution of muscle spindles was studied in histochemically and conventionally stained serial cross sections of 6-week-old and adult rat masticatory and suprahyoid muscles. Spindles were present in moderate to large numbers in jaw closers, but they were absent in jaw openers and two of four muscles of an accessory suprahyoid group. In jaw closers, 67% or more of the total spindle population was concentrated relatively distant from the temporomandibular joint, in muscle portions which contained large numbers of extrafusal fibers reacting strongly for oxidative enzymes. Because of their location, spindles in these portions should be stretched more and, subsequently, should respond with a greater afferent discharge at any given muscle length than spindles situated nearer to the joint. Spindles in jaw closers, especially the medial pterygoid and deep masseter, often occurred in clusters and complex forms near the terminal branching of intramuscular nerve trunks. No such concentrations were seen in the two muscles of the accessory suprahyoid group that had spindles. The association in jaw closers of spindles with extrafusal fibers high in oxidative enzyme activity is consistent with the view that spindles are the sensory component of a reflex system that recruits these fibers for finely-graded contractions in response to small internal length-changes of the muscle (Botterman et al., '78); however, in jaw openers and two muscles of the accessory suprahyoid group, the absence of spindles, coupled with the presence of large populations of extrafusal fibers high in oxidative enzyme activity, is not easily reconciled with this concept.

Animals↗

PubMed1994

Forces applied during laryngoscopy in children. Are volatile anaesthetics essential for suxamethonium induced muscle rigidity?

Increased masticatory muscle tone after administration of suxamethonium has been demonstrated in children when combined with volatile anaesthetics. Whether volatiles are a prerequisite for this phenomenon is not known. In this study upper airway muscle tone, including the tone of the masticatory muscles, was determined in 54 children (age range 2-15 years), anaesthetized with propofol, fentanyl and nitrous oxide and avoiding any use of volatiles. The children were either relaxed with suxamethonium (n = 26) or vecuronium (n = 28). The forces applied during laryngoscopy were used to quantify upper airway muscle tone and were significantly greater in the suxamethonium group than in the vecuronium group: maximally applied force was 25 N versus 21 N (P = 0.008), and mean applied force was 16 N versus 13 N (P = 0.006), respectively. The results of this study indicate that upper airway muscle tone increases after administration of suxamethonium in children independent of the presence of volatile anaesthetics. Moreover, increased muscle tone had no effect on the difficulty of laryngoscopy or the intubation conditions. Increased masseter muscle rigidity after suxamethonium could be due to the very unique characteristics of this muscle.

Adolescent↗

PubMed2002

The significance of saliva during sleep and the relevance of oromotor movements.

Saliva is an essential component of the oroesophageal milieu and allows for normal speech, taste, mastication, food bolus formation and swallowing. Saliva has important functions in protecting the hard and soft tissues of the oral cavity from acids and pathogenic microbes. A large number of people suffer either subjective or objective alterations in quantity and/or quality of their saliva that may be secondary to disease, medications, medical treatments or emotional events. Sleep-related xerostomia is a sensation of dry mouth associated with a report of either mouth and/or throat discomfort that induces awakenings for water intake. The prevalence of self-reported dry mouth complaint during sleep (associated with awakening and water intake) in a Canadian survey was estimated at 23%. The biological significance of decreased saliva during sleep is unknown and it is unclear how the oral cavity compensates for this period of relative dryness. The amount of saliva produced is greatest during the waking hours of the day and diminishes dramatically during sleep and may represent another process in the human body that displays a circadian rhythmicity. Salivary secretion during wakefulness is, in part, associated with oromotor activity involving the masticatory muscles. Rhythmic masticatory muscle activity and swallowing are non-disruptive events that occur during normal sleep. We hypothesize herein that lubrication from saliva is necessary during sleep to protect tissue integrity and health of oroesophageal structures.

Bruxism↗

PubMed1988

The effects of pain from the mandibular joint and muscles on masticatory motor behaviour in man.

Habitual chewing of a coherent bolus was studied in 12 dentate subjects with painful mandibular-joint disorders and 12 healthy, dentate controls. Bilateral electromyograms of jaw elevators, and jaw movement, were recorded for three complete masticatory sequences. Computer analysis was used to classify chewing movements as continuous or discontinuous. Root-mean-square (r.m.s.), myoelectric signal amplitudes were computed for each of four jaw elevators. Although discontinuous chewing cycles were significantly more frequent in painful function (p = 0.001), they also occurred in pain-free function, a finding which reduces their diagnostic significance. During painless and painful function, r.m.s. activities did not differ statistically when elevators acted as agonists on both the dominant and non-dominant chewing side (p greater than 0.1). When used as antagonists, such as during jaw opening, the elevators had greater mean peak activities during painful than painless function (p = 0.0001). Variability in maximum gape was greater during painful than painless function (p = 0.001), but peak maximum gapes in complete masticatory sequences were not affected by pain, and neither were minimum interocclusal gapes. More frequent reshaping and repositioning of the bolus in the presence of pain could explain these differences between painful and pain-free function.

Electromyography↗

PubMed1998

Oro-facial muscles: internal structure, function and ageing.

Structure and function are reviewed in the masticatory muscles and in the muscles of the lower face and tongue. The enormous strength of jaw closure is in large part due to the pinnated arrangement of the muscle fibres in the masseter. This muscle, like other masticatory muscles, is unusual in that the cell bodies of the muscle spindle afferents lie in the brain stem rather than in an external ganglion; spindles are absent in the lower facial muscles. Although few data are available, the numbers of motor units in the masticatory muscles, and probably in the lower facial muscles also, appear to be much greater than in limb muscles. The motor units in the facial and tongue muscles are largely composed of histochemical type II ('fast-twitch') fibres, but in the masticatory muscles there are substantial numbers of fibres intermediate between type I ('slow twitch') and type II, and fibre type grouping is present. In comparison with limb muscles, there is little information on ageing changes in oro-facial muscles. The masticatory muscles do, however, show some atrophy and loss of X-ray density, while motor unit twitches are prolonged. Strength is reduced in the tongue and masticatory muscles. It is known that limb muscle properties are largely governed by their innervation, both through the pattern and amount of impulse activity, and the delivery of trophic messengers; the situation for oro-facial muscles is unclear. The structural and functional differences between the two types of muscle indicate the need for conducting ageing studies on the oro-facial muscles, rather than relying on extrapolations from limb muscles.

Aged↗

PubMed2005

Oral parafunctions and positive clinical examination findings.

STATEMENT OF PROBLEM: Oral parafunctional activity can be fatigued and painful masticatory muscles and/or pain in the temporomandibular joints. There is controversial discussion in the literature as to what role parafunctional activity plays in the multi-causal pathologic process. PURPOSE: The purpose of this study was to determine any association between the level of parafunctional habits versus the level of mandibular dysfunction and to test the hypothesis that TMD/bruxer patients have significantly increased muscle tension and joint pain. MATERIAL AND METHODS: There were 307 subjects (140 males und 167 females) selected for this investigation. 299 subjects were examined regarding any relationships between clenching and the incidence of muscle sensitivity. The age of subjects ranged from 20 to 54 years old, with a mean age of 35.4. 114 subjects had at least one sign of temporomandibular disorders (tenderness/pain on palpation of the joints or muscles, TMJ sounds, pain or deviation during maximum mouth opening (active/passive). RESULTS: 81 subjects admitted to clenching, while 218 said they did not. Among the "non-clenchers", 68.8% had no sensitive muscles, 31.2% indicated sensitive masticatory muscles. Those who clenched their teeth were distributed as follows: 53.1% were diagnosed with bilateral masticatory muscle sensitivity, 46.9% showed no such indications. The two groups were not homogeneously divided, with regard to pain/discomfort (p = 0.001; Fisher's precision test). CONCLUSION: This study found a statistically solid relationship between the incidence of "clenching" and muscle palpation findings, as well as between sensitivity in the mandibular joints from lateral and to cranial and dorsal with positive muscle palpation findings. The agreement between sensitivity of the masticatory musculature and the mandibular joint demonstrates that intensive clenching can predominantly lead to pathologic phenomena in the muscles or joints.

Adult↗

PubMed1988

Pain in the sternocleidomastoid muscle and occlusal interferences.

The EMG of the sternocleidomastoid muscle and the masticatory muscles during function has been observed in relation to opposing occlusal contacts. The purpose was to investigate the possible developmental mechanism of pain which can occur in the muscles. Six subjects with normal function and ten patients were studied. EMG activities of temporal, masseter, sternocleidomastoid (insertion) and sternocleidomastoid (middle) were recorded by surface and needle electrodes. EMG activity was recorded from the insertion of the sternocleidomastoid during activity of the masticatory muscles in tapping, clenching, and mastication. On the other hand little activity was registered from the middle of the sternocleidomastoid. The amplitude of the EMG of SCM-I increased as the occlusal force increased. During chewing the sternocleidomastoid muscle was functioning more actively on the working side than on the non-working side. On the patients, EMG activities of the muscles were of low amplitude and low frequency with no synchronization with the chewing movement, suggesting hyperactivity of the muscle.

Adult↗

PubMed1992

Application and validation of a three-dimensional mathematical model of the human masticatory system in vivo.

A previously described three-dimensional mathematical model of the human masticatory system, predicting maximum possible bite forces in all directions and the recruitment patterns of the masticatory muscles necessary to generate these forces, was validated in in vivo experiments. The morphological input parameters to the model for individual subjects were collected using MRI scanning of the jaw system. Experimental measurements included recording of maximum voluntary bite force (magnitude and direction) and surface EMG from the temporalis and masseter muscles. For bite forces with an angle of 0, 10 and 20 degrees relative to the normal to the occlusal plane the predicted maximum possible bite forces were between 0.9 and 1.2 times the measured ones and the average ratio of measured to predicted maximum bite force was close to unity. The average measured and predicted muscle recruitment patterns showed no striking differences. Nevertheless, some systematic differences, dependent on the bite force direction, were found between the predicted and the measured maximum possible bite forces. In a second series of simulations the influence of the direction of the joint reaction forces on these errors was studied. The results suggest that they were caused primarily by an improper determination of the joint force directions.

Adult↗

PubMed1997

Electric versus magnetic transcranial stimulation of the trigeminal system in healthy subjects. Clinical applications in gnathology.

This investigation is focused on the analysis of the masseter responses evoked by means of magnetic and electric stimulation of the cortex and root of the trigeminal system of 20 healthy subjects. Moreover, in order to determine jaw elevation in centric occlusion, the analysis also focused on the motor response of the trigeminal bilateral roots evoked simultaneously using two stimulators. The masseter responses show a high level of symmetry in both latency and amplitude. The difference between the hinge axis in natural centric occlusion (CO) and in centric relation (CR) as determined by electric and magnetic transcranial stimulation is lesser than 2.5 mm. This is due to two main factors: (i) the response is evoked from the trigeminal motor neural pool involving all the masticatory muscles and hence simulating the natural 'muscular coactivation'; (ii) there is no manual manipulation to guide the jaw into the centric relation (CR). This method could be of some help for diagnosis in patients suffering from TMJ dysfunction who have lost stereognostic control over the jaw and display obvious signs of deviation during closure of the mandible.

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↗

PubMed1991

Causes and signs of temporomandibular joint pain and dysfunction: an electromyographical investigation.

The spontaneous muscular activity of the masseter and two non-masticatory muscles, and their activity under conditions of noise and flickering light, were recorded in 30 patients with mandibular dysfunction, and in 25 control subjects. The mood of the subjects during the investigation, and the possible presence of emotional disturbances was evaluated by means of questionnaires. The enhanced muscular activity of the masseter muscle differentiated patients from the control group, although it does not constitute a pathognomic sign. Unilaterality of complaints, and dysfunctions of differing intensity were not reflected in differential EMG findings. One-fifth of the patients exhibited neck muscle activity occurring simultaneously with the masseter activity. The effect of the applied stimuli on the muscular activity was not homogeneous, leading to activation in some cases and inhibition in others. Symptoms of anxiety could be observed in seven TMJ patients. Anxious patients showed higher levels of muscular activity and emotional irritability during the experiment than non-anxious patients.

Action Potentials↗

PubMed1989

[Electromyographic evaluation of muscular tension in dysfunctional subjects in relation to normal subjects].

Electromyography has been used to analyse the myoelectric activity of the masticatory muscles in 130 dysfunctional patients in comparison with normal subjects. Of the muscles examined, those presenting greater basal tension were also identified. Myoelectric activity proved greater, at postural values, in dysfunctional patients; by contrast, subjects without craniomandibular symptomatology presented normally low initial values. As for the analysis of the muscular group presenting greater tension, analysis of the results did not produce statistically significant percentages pointing to the prevalence of one muscular group over another.

Adolescent↗

PubMed1979

[Experimental study of oral hyperactivity caused by mental stress, in particular by aggression].

18 patients without stomatognathic symptoms were examined by three psychological tests (Foto-Hand test, Freiburg personal inventory, and Giessen Test). Aggression had had the strongest effect upon masticatory muscles. Various other effects were studied, like ECG, respiration, pulse, tremor, skin resistance, masseter, biceps and triceps. Because of the visible effect upon the stomatognathic system it is plausible that disease in this organic system is to be expected at an early stage.

Aggression↗

PubMed1983

Modulation of the masseteric reflex by gastric vagal afferents.

Several investigations have shown that the vagal nerve can affect the reflex responses of the masticatory muscles acting at level either of trigeminal motoneurons or of the mesencephalic trigeminal nucleus (MTN). The present experiments have been devoted to establish the origin of the vagal afferent fibres involved in modulating the masseteric reflex. In particular, the gastric vagal afferents were taken into consideration and selective stimulations of such fibres were performed in rabbit. Conditioning electrical stimulation of truncus vagalis ventralis (TVV) reduced the excitability of the MTN cells as shown by a decrease of the antidromic response recorded from the semilunar ganglion and elicited by MTN single-shock electrical stimulation. Sympathetic and cardiovascular influences were not involved in these responses. Mechanical stimulation of gastric receptors, by means of gastric distension, clearly diminished the amplitude of twitch tension of masseteric reflex and inhibited the discharge frequency of proprioceptive MTN units. The effect was phasic and depended upon the velocity of distension. Thus the sensory volleys originating from rapid adapting receptors reach the brain stem through vagal afferents and by means of a polysynaptic connection inhibits the masseteric reflex at level of MTN cells.

Animals↗

PubMed1988

Expression of fiber type specific proteins during ontogeny of canine temporalis muscle.

The canine masticatory muscles contain a unique adult fiber type composition and different contractile protein isoforms than do adult limb muscles. To determine when these characteristic proteins are expressed during development, samples from canine temporalis (masticatory) and pectineus (limb) muscles were compared between 55 days gestation and 60 days postpartum by histochemical, biochemical, and immunocytochemical analysis. At 55 days gestation and 3 days postpartum, both muscles contained identical histochemical type 2C fibers, native myosin isozymes, and myosin light and heavy chains. By 14 days postpartum, fiber-type expression in these muscles diverged, with resultant formation of type 1 and type 2M fibers in the temporalis muscle and type 1 and 2A fibers in the pectineus muscle. The distinctive myosin isoforms, light chains, and heavy chain of the temporalis muscle were also expressed 2 weeks postpartum. Based on the methods used in this study, we conclude that (1) the temporalis muscle develops from embryonic fibers that initially contain a myosin indistinguishable from embryonic limb muscle fibers, suggesting they have a common precursor, and (2) the myosin light chains and heavy chain unique to the temporalis muscle are initially expressed 2 weeks postpartum.

Animals↗