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 1,243 records · Page 69Linked to original sources
PubMed1977

Kinematics of the tooth tapping movement.

Electrical activity in the masseter muscles and tooth contact vibrations were recorded simultaneously from subjects tapping their teeth slowly into maximal intercuspidation and again with maximal frequency. High speed cinephotography was also used with four of the ten subjects. Three main parts could be distinguished on the obtained graphical representation of the tooth tapping movement: tooth contact phase (TCP), opening phase (OP) and closing phase (CP). Tapping frequency was increased by decreasing the jaw opening degree and the durations of TCP, OP and CP. The jaw velocity immediately before tooth contact, which may be of significance for the reflex response, was however not increased. The average jaw speed was nevertheless increased from 10 to 15 cm/s since the turning from OP to CP was more abrupt in high than in low frequency tapping. The duration of electrical activity after tooth contact was significantly shorter at tapping with high than with low frequency. The teeth maintained contact without detectable rebound between each open-close cycle. The OP started about 100 ms after the cessation of electrical activity both at low and high tapping frequency. The time between end of electrical activity and the start of a new OP was supposed to be dependent upon the relaxation time of the masseter muscles.

Adult↗
PubMed2001

Excitability of the human trigeminal motoneuronal pool and interactions with other brainstem reflex pathways.

We studied the properties of motoneurones and Ia-motoneuronal connections in the human trigeminal system, and their functional interactions with other brainstem reflex pathways mediated by non-muscular (Abeta) afferents. With surface EMG recordings we tested the recovery cycles of the heteronymous H-reflex in the temporalis muscle and the homonymous silent period in the masseter muscle both elicited by stimulation of the masseteric nerve at the infratemporal fossa in nine healthy subjects. In four subjects single motor-unit responses were recorded from the temporalis muscle. In six subjects we also tested the effect of the stimulus to the mental nerve on the temporalis H-reflex and, conversely, the effect of Ia input (stimulus to the masseteric nerve) on the R1 component of the blink reflex in the orbicularis oculi muscle. The recovery cycle of the H-reflex showed a suppression peaking at the 5-20 ms interval; conversely the time course of the masseteric silent period was facilitated at comparable intervals. The inhibition of the test H-reflex was inversely related to the level of background voluntary contraction. Single motor units were unable to fire consistently in response to the test stimulus at intervals shorter than 50 ms. Mental nerve stimulation strongly depressed the H-reflex. The time course of this inhibition coincided with the EMG inhibition elicited by mental nerve stimulation during voluntary contraction. The trigeminal Ia input facilitated the R1 component of the blink reflex when the supraorbital test stimulation preceded the masseteric conditioning stimulation by 2 ms. We conclude that the time course of the recovery cycle of the heteronymous H-reflex in the temporalis muscle reflects the after-hyperpolarization potential (AHP) of trigeminal motoneurones, and that the Ia trigeminal input is integrated with other brainstem reflexes.

Adult↗
PubMed1995

Posterior bite raising effects on a primary anterior crossbite case.

Stainless steel crowns were cemented on the mandibular primary molars to make bite raising for an anterior reversed bite case. Chewing force and MKG were recorded before and after bite raising. Data from MKG revealed that co-ordination pattern of muscle activities after bite raising became higher in masseter muscles than those before anterior reversed bite was corrected easily without any incisal interferences by using this treatment method.

Bite Force↗
PubMed1993

Electromyographic activity of human masticatory muscles in normal young people. Statistical evaluation of reference values for clinical applications.

Electromyographic activity of anterior temporal and masseter muscles was measured in 92 young healthy men and women with sound dentitions during rest position, contact in centric occlusion and clench. Male and female mean potentials were similar except in clench, where males had higher electromyographic levels. Mean pooled electromyographic potentials were 1.9 microV (TA) and 1.4 microV (MM) during rest position, 6.5 microV (TA) and 2.8 microV (MM) during contact in centric occlusion. Mean maximum voluntary clench potentials were 181.9 microV (TA) and 216.2 microV (MM) in men, 161.7 microV (TA) and 156.8 microV (MM) in women. Examined muscles were more asymmetric at low electromyographic activity (rest and centric occlusion) with the temporal muscle less asymmetrical than the masseter. In females temporal muscle activity tended to dominate at every contraction level, while in males masseter activity was stronger in clench, and temporal activity in centric occlusion and in rest position.

Adult↗
PubMed1993

Fatigue and EMG changes in the masseter and temporalis muscles during sustained contractions.

Local muscle fatigue was investigated in the anterior temporal and masseter muscles during sustained isometric contractions. The volunteers' subjective perception of fatigue or pain was recorded at intervals during the sustained contractions, and this level was then compared to objective measures of fatigue. These objective measures included shift in median frequency of the power spectrum of the surface-detected EMG signal, and change in signal amplitude. The relationship was investigated while closing on a bite force meter placed between the second premolars and first molars unilaterally, and while simply clenching with the teeth together without the bite force meter. It was found that the subjective perception of fatigue, as measured on a visual analogue scale (VAS), had a nearly linear relationship with time, and that the relationship between the VAS score and median frequency shift was rather closer than the relationship with amplitude change.

Analysis of Variance↗
PubMed1989

The masseter inhibitory reflex is evoked by innocuous stimuli and mediated by A beta afferent fibres.

Mechanical or electrical stimulations in the area of the mouth evoke two phases of inhibition in the masseter muscle (early and late inhibitory reflex, also called masseter silent periods). The question whether the afferents of the human masseter inhibitory reflex are nociceptive or non-nociceptive has not yet been settled. We showed that an innocuous stimulus, such as a fine jet of saline directed to the lips of healthy humans, evokes an early and a late masseter inhibitory reflex, similar to those following electrical stimulation. We measured the efferent and afferent delay of the masseter early inhibitory reflex in patients submitted to intracranial stimulation of the motor and sensory trigeminal root, and found that the reflex afferents belong to the intermediately-fast conducting fibre group.

Afferent Pathways↗
PubMed2004

Functional properties of skinned rabbit skeletal and cardiac muscle preparations containing alpha-cardiac myosin heavy chain.

Contractile properties of skinned muscle fibres from the masseter muscle and strips of heart atrium muscle from rabbits, both containing the alpha-cardiac myosin heavy chain isoform (alpha-cardiac MHC), were investigated and compared with those of other skeletal muscle fibre types. The stretch-induced delayed force increase (stretch activation) was investigated on maximally Ca(2+)-activated skinned preparations as an index of the kinetic properties of the myosin heads of various MHC isoforms. Skeletal muscle fibres containing exclusively alpha-cardiac MHC (type alpha) and muscle strips of heart atrium showed specific kinetics of stretch activation intermediate between those of types IIA and I fibres. In agreement with available data the unloaded shortening velocity V(u) of type alpha fibres was also intermediate between that of types IIA and I fibres. Compared with skeletal muscle type alpha fibres, muscle strips of heart atrium exhibited significantly (P<0.001) faster kinetics of both stretch activation and V(u). We conclude that type alpha fibres have characteristic kinetic properties that fill the gap between the fast type II and the slow type I fibres, and the following order of velocity can be established: IIB>IID(X)>IIA>alpha>I.

Animals↗
PubMed1987

Muscle-fibre architecture of the rat medial pterygoid muscle.

The detailed fibre architecture of the rat medial pterygoid muscle, including the courses and attachment points of muscle fibres, was investigated histologically in 10 micron thick serial sections in the horizontal, coronal and parasagittal planes. Four extramuscular tendinous sheets (external aponeuroses) and four intramuscular tendinous sheets (internal aponeuroses) were found. Three of the internal aponeuroses were arranged parallel to the rostro-caudal axis; the other was oblique to the rostro-caudal axis. Muscle fibres were located between internal aponeuroses, between external aponeuroses, between internal and external aponeuroses, between an internal aponeurosis and the periosteum, and between an external aponeurosis and the periosteum. The courses of muscle fibres were divided into three main groups: vertical, rostro-caudal and medio-lateral. Eight compartments were distinguished. The multiple movement of the medial pterygoid muscle seemed to be due to this compartmentalization. These findings suggested that the rat medial pterygoid muscle, like the rat masseter muscle, is mainly composed of multipennate muscles and compartmentalized into many muscle-fibre bundles running in different directions.

Animals↗
PubMed1992

Basic fibroblast growth factor-like immunoreactivity in the trigeminal proprioceptive and motor systems.

Basic fibroblast growth factor (bFGF) isolated from the brain and pituitary, has been shown to induce cell divisions in a variety of cell types. It also acts as a potent stimulator of angiogenesis, and it is important in the survival of several types of cultured neurons. Despite considerable information on the functions of bFGF, there is incomplete knowledge about the ways in which it reaches remote tissues and its subcellular localization in the adult brain. Here we report our findings that a certain population of neurons with free ribosomes and rough endoplasmic reticulum immunoreactive for bFGF in the mesencephalic nucleus of the trigeminal nerve sends proprioceptive fibers to muscle spindles in the masseter muscle, and immunoreactive axons to the trigeminal motor nucleus to form synapses with the bFGF-containing motoneurons whose axons further constitute myoneural junctions in the periphery. Moreover, some bFGF neurons contain electron dense immunoreaction deposits in the euchromatin but not in the heterochromatin of the nucleus. These findings suggest that endogenous bFGF is transported within nerve processes and functions in mature neuronal circuits subserving the masseteric reflex arcs, and that bFGF is produced in free ribosomes and/or rough endoplasmic reticulum and is transported into the genetically active euchromatin as well.

Animals↗
PubMed1984

Recovery cycle of the masseter inhibitory reflex in man.

The masseter inhibitory reflex from stimulation of the mental nerve has been recorded electromyographically in 10 healthy subjects. The recovery cycle of the two silent periods interrupting the tonic contraction of the masseter muscles have been studied with the paired shock technique. There was a clear dissociation between the recovery of early and late inhibition, the latter being far more affected by a preceding impulse. It is concluded that the two silent periods are mediated by separate neural nets. The differences with the recovery curves of the two components of the blink reflex are discussed.

Adult↗
PubMed2001

Habituation of the early pain-specific respiratory response in sustained pain.

Neurokinin-1 receptor and mu-opioid receptor agonists affect respiratory rhythm when injected directly into the preBötzinger brainstem complex, which is the hypothesized site for respiratory rhythmogenesis in mammals (Science 286 (1999) 1566). Early stress-induced analgesia (SIA) is naloxone-insensitive and as such considered independent of the activation of the mu-opioid system. Prolonged application of electrical shocks, however, produces analgesia that is mediated by the mu-opioid system (Science 208 (1980) 623). Together these findings suggest that any early pain-specific increased respiration should be attenuated in the tonic state of pain. Ten healthy, pain-free female volunteer subjects participated in this experimental study involving deep acute and tonic pain. The experimental design included three conditions: (1) baseline; (2) pain; and (3) a placebo control stimulus. Experimental pain was induced by the infusion of hypertonic saline into the masseter muscle. Infusion of isotonic saline in the contralateral masseter was used as a control. Blinded subjects were randomly assigned to a particular sequential order of the experimental stages, i.e. hypertonic saline infusion preceded the isotonic saline infusion or vice versa. Respiration rate, mean peak inspiratory and expiratory flow rates, and the minute ventilation volume quantified breathing. Results indicate that effects on respiration were pain-specific and that the early effects on respiration were significantly attenuated in sustained pain. In the early stage of pain, all monitored variables (respiration rate, minute ventilation volume, and inspiratory and expiratory flow rates) were elevated to statistically significant degrees when compared to measurements taken at baseline or during control infusion. Only respiration rate continued to be significantly elevated in sustained pain. We concluded that rhythmogenic neurons in the preBötzinger brainstem complex appear as the likely target for pro-nociceptive and anti-nociceptive input, explaining both the observed initial facilitation and subsequent habituation of respiration in early and sustained pain.

Adult↗
PubMed1976

[2 cases with unusual lid-jaw co-movements].

General review of the literature makes it apparent that there exist various combinations of associated movements between cranial nerves. Most of them involve four of nerves, the oculomotor, the abducens, the facial, and the motor potion of the trigeminal nerve. We report two patients in whom left upper eyelids produced peculior up and down movements in accompany with mastication. The one was a 9-year-old female who had shown left eye-lid retraction since 3 months; the other, a 4-year-old male, had produced the synkinesis one year since. Either children showed contraction of left palpebral levators associated with volitional mouth opening, deviation of the mandible toward the right, and sucking. Their pupils were normal and their upper eye-lids showed no ptosis on the affected side. The EEG showed high voltage rhythmic slow waves in parieto-occipital areas bilaterally. Head injuries or hereditary defects not being recorded in their histories, their synkinesis is assumed to be congenital in orgin. Abnormal neural connections have been presumed to be affected in the course of the development between the trigeminal and the oculomotor nuclei within the midbrain. In triggering the synkinesis, however, stretched muscle-spindles of the masseter muscle most play an important role. After all, synchronizing lid-jaw co-movements as observed in our two children represent an unusual pattern of the Marcus Gunn phenomenon.

Child↗
PubMed2002

Correlation between facial patterns and function of the masticatory muscles in girls and women.

The relationship between maxillo-facial patterns and function of the masticatory muscles was evaluated using electromyography, in 16 women with functional normal occlusion and 16 girls with chronological normal occlusion half of them had the dolico facial pattern and the others had the brachyo facial pattern by Ricketts analysis. For the electromyography, loads of 1, 2, 3, 4, and 5 kg were applied to the mandible, and muscular activity waves were obtained from the masseter muscle and the anterior belly of the temporal muscle during isometric contraction by surface electrode induction. The median frequency value (MFV) in a frequency curve obtained by high-speed Fourier transform of the electromyographic waves was set to the evaluation index. The MFV at each applied load was higher in the adult brachyo facial pattern group than in the adult dolico facial pattern group in both the masseter and temporal muscles, whereas the differences in the MFV were slight in the child group at a 5% significance level. The child group showed approximately half the incidence of significant correlation coefficients in comparison with the adult group and a large standard deviation without marked differences in the facial patterns due to their individual differences in growth with a 5% significant level. The adult brachyo facial pattern group showed a high regression coefficient of the MFV in the masseter muscle according to the increase in the amount of the applied load. Although differences in the cooperative contraction patterns similar to those in the adult group were observed in both the child dolico and brachyo facial pattern groups, no marked significant differences were observed in the child group, who had large individual differences due to their immature growth.

Adolescent↗
PubMed1988

Head posture and hyo-mandibular function in man. A synchronized electromyographic and videofluorographic study of the open-close-clench cycle.

Synchronized electromyography and videofluorography (lateral projection) were used to investigate the influence of altered head posture on hyo-mandibular movements, suprahyoid muscle length, suprahyoid working angle, and timing of suprahyoid and masseter muscle activity. Twelve adult male subjects with normal dentofacial morphology were investigated during the open-close-clench cycle. Using upright head position (Frankfort horizontal) as reference, several statistically significant observations were made during forward flexion and backward extension of the head. The results indicate that head posture is a significant factor in studies of mandibular and hyoid bone movements, and masseter and suprahyoid muscle function.

Adult↗
PubMed1983

Rotation of synergistic activity during isometric jaw closing muscle contraction in man.

5 healthy subjects were studied during 10-15 min of isometric jaw elevator contraction above fatigue threshold level. Bite force was measured between upper and lower front teeth and electromyographic (EMG) activity recorded from the right temporal and masseter muscles. Of the two muscles only the masseter was active at the start of the test and usually during the whole test. When the test was repeated, however, great relief from the pain in the fatigued masseter was sometimes experienced and the temporalis took over the load. All subjects experienced this "switch" phenomenon after a varying number of tests, one of them already during his first test. The mechanism seemed to be completely out of voluntary control and showed facilitation at repeated tests.

Electromyography↗
PubMed1983

A method of bite force measurement in primates.

A bite force transducer consisting of two differential strain beams with four strain gages in a full bridge configuration was modified for measuring occlusal forces in rhesus monkeys. A procedure of muscle stimulation (20-50 V, 60 Hz, and 0.8 ms duration) produced maximal unilateral masticatory muscle contraction when stimulating electrodes were placed in the masseter muscle. Tests of this procedure revealed reproducible results and a potential for use in studies of the force of isometric contraction of the masticatory muscles in normal and experimentally altered macaques and other primates.

Animals↗
PubMed1984

Muscle transposition for facial reanimation. Indications and results.

The technique of transposing the temporalis and masseter muscles to reanimate the face following long-standing facial paralysis was introduced at the turn of the century. More recently it has been popularized by Rubin and Conley. The indications for performing this technique are outlined, and the results are analyzed.

Adolescent↗
PubMed2000

Functions of masseter and temporalis muscles in the control of temporomandibular joint loading--a static analysis using a two-dimensional rigid-body spring model.

Masticatory forces or bite forces applied to the teeth are known to generate a compressive force on the temporomandibular joint (TMJ). This intra-articular force is referred to as TMJ loading. TMJ loading is considered to be controlled to a certain extent by the stomatognathic system, so as not to exceed a certain limit. In order to clarify the control mechanism of the TMJ during biting, the controllability of TMJ loading through coordinated activities of the masticatory muscles has been numerically analyzed using a static two-dimensional jaw model. This model consists of a rigid-body model of the jaws and a spring model of the articular disk, which includes three dominant muscle force vectors representing the masseter, temporalis and lateral pterygoid muscles. The bite force vector is assumed to be applied solely at the first molar. Static equilibrium analyses suggest that coordinated activities of the masseter muscle and anterior portion of the temporalis muscle can minimize TMJ loading and concentrate the stress within the articular disk to the intermediate zone of the disk, and that the activity of the posterior portion of the temporalis muscle has the possibility of reducing TMJ loading.

Bite Force↗