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At least 325 records · Page 18Linked to original sources
PubMed1998

Cold pressor stimulus temperature and resting masseter muscle haemodynamics in normal humans.

Cold pressor stimulation reportedly increases sympathetic nerve activity in human skeletal muscles. This study examined the effect of cold pressor stimulation on the resting haemodynamics of the right masseter muscle in normal individuals, using near-infrared spectroscopy. Nine healthy non-smoking males with no history of chronic muscle pain or vascular headaches participated. Their right hand was immersed in a water bath (4, 10, 15 degrees C) for exactly 1 min. Each trial lasted 7 min (1 min before, 1 min during, 5 min after stimulation) and a strictly random order was utilized for the three test temperatures and the mock trial. Masseter muscle haemoglobin concentration and oxygen saturation, as well as heart rate and blood pressure, were continuously recorded in each trial. After completing the four trials, each participant produced and sustained a 30-s maximum voluntary clench in the intercuspal position. Data across the four trials were baseline-corrected and then magnitude-normalized to the individual's highest absolute haemoglobin and oxygen signal during the 30-s maximal clenching effort. Haemoglobin and oxygen saturation increased progressively during cold pressor stimulation as the water temperature decreased (Hb, p < 0.0001; O2, p = 0.0327); very little effect was seen during the mock trial. Heart rate and blood pressure also increased progressively during the stimulation as the temperature decreased (heart rate, p = 0.0013; systolic blood pressure, p = 0.0042; diastolic blood pressure, p = 0.0156). These data suggest that cold pressor, stimulation induces a strong increase in intramuscular blood volume which appears to be due to both a local vasodilative response and increased cardiac output.

Adult↗
PubMed1994

Ultrasonographic evaluation of inflammatory changes in the masseter muscle.

The ultrasonographic images of 32 patients with inflammatory change in the masseteric region were investigated to clarify the characteristic findings and to evaluate the utility of ultrasonography. Inflamed masseter muscles frequently demonstrated reduction of echo intensity and complete or partial absence of hyperechoic bands. The mean thickness of the masseter muscle on the unaffected side was 8.6 mm, whereas that on the affected side was 12.9 mm. Nine of 10 patients with heterogeneous hypoechoic area, but only 1 of 10 patients with homogeneous hypoechoic area, had received surgical treatment before ultrasonographic examination.

Abscess↗
PubMed1990

[Evoked phonomyography of the human masseter muscle].

Sounds obtained in normal man by electric stimulation of masseter muscle have been analyzed both in the domain of time and frequency. Data thus obtained have been compared with those obtained by the same technique in vastus lateralis and soleus muscles. Results suggest the feasibility of sound analysis in dentistry diagnosis.

Amplifiers, Electronic↗
PubMed1985

Ultrastructural changes of neuromuscular receptor organs in the masseter muscles following unilateral transection of the rat infraorbital nerve.

Definite ultrastructural changes of the neuromuscular receptor organs were demonstrated in the young and adult rat masseter muscles either on the operated or unoperated side following the unilateral transection of the infraorbital nerve. The grade of the degeneration was intensive but quite similar in having no relation to the age of the rat when the operation was performed, while it increased drastically with time after the operation. On this base, it may be suggested that the sensory input coming from the various kinds of sensory receptors in the snout field do rather affect bilaterally the minor reflexive movements of the jaw. In other words, it can be said that the minor reflexive movements of the jaw might have been controlled by the sensory inputs coming from the snout sensory receptor organs. The definitely degenerated changes of the neuromuscular receptor organs in the masseter muscles should be regarded as disuse atrophy following the interception of the snout sensory input.

Animals↗
PubMed1993

Bone growth and periosteal migration control masseter muscle orientation in pigs (Sus scrofa).

During growth the muscles of mastication alter their lines of action. Research on long bones indicates that the apparent migration of muscle attachments is due to the movement of the periosteum relative to the underlying bone. To assess whether the pig masseter muscle follows the periosteum during growth, implants of titanium granules in a gelatin matrix were placed simultaneously in various parts of the masseter muscle and its periosteal and bony attachments. Growth movements of these tissues were followed radiographically for 2 months. Granule position was verified histologically. Periosteal movement was the dominant growth process at the insertion of the masseter. All implants migrated caudally relative to the mandible. However, a strong position effect was seen dorsoventrally: implants placed high in the ascending ramus migrated dorsally as well as caudally; low implants migrated only caudally. This differential migration, ascribed to the influence of the condyle, accounts for the increasing horizontal orientation of dorsal fibers. A similar differential was seen along the rostrocaudal axis of the ramus. In contrast to the insertion, the origin of the masseter from the zygomatic arch shows no periosteal movement. Rather, the entire bone-muscle complex becomes displaced by sutural growth, leading to increasing vertical orientation of the masseter. Thus two different aspects of skull growth are responsible for the change in muscle anatomy.

Animals↗
PubMed1995

Reduction of masseter muscle activity in bottle-fed babies.

Our previous studies suggested that there are significant differences in the growth of the jaw and in muscle activity between breast- and bottle-fed infants. To confirm these differences quantitatively, myoelectric activities of the masseter muscles of bottle-fed babies were studied. Twelve bottle-fed babies, as well as 12 breast-fed babies as a control group, were examined electromyographically during bottle or breast feeds. The duration time of sucking bursts, interval time, cycle time, 0-to-peak amplitude, integrated amplitude of bursts, and integrated amplitude/duration time were measured and the number of bursts over 30 microV was counted. All differences of means were significant by t-test. The masseter muscle activity in bottle-fed babies is significantly reduced. Our results are contrary to previous papers in which almost the same sucking actions in both breast and bottle feeding were reported. The reason why previous researchers thought that the sucking patterns in breast- and bottle-fed babies are essentially the same is considered, and the implications of the differences for dental health are discussed.

Bottle Feeding↗
PubMedDate not supplied

Dimensions and geometry of the temporomandibular joint and masseter muscles.

The bio-engineering team presents its suggestion of a method for the measurement of the temporomandibular joint and masseter muscles in order to determine the parameters necessary for exact sciences and indispensable for unified and objective cognitive studies. Ten formalin-fixed human cadavers served for the studies. The preparations were prepared by the modified method of anatomical procedure. Linear and angular measurements of temporomandibular joint and masseter muscles were carried out with the use of the three-dimensional Cartesian system of OXYZ coordinates in relation to frontal, sagittal and horizontal planes. The physiological cross-sections of the masseter, temporal, lateral and medial pterygoid muscles were also determined. The collected data make it possible to develop a mathematical three-dimensioned model of the osseo-articulo-muscular system of the mastication organ.

Cephalometry↗
PubMed1983

Influence of experimental interfering occlusal contacts on the activity of the anterior temporal and masseter muscles during submaximal and maximal bite in the intercuspal position.

The effects of an intercuspal occlusal interference on the pattern of activity of the anterior temporal and masseter muscles during submaximal and maximal bite, were studied in eleven volunteers with complete, natural dentitions. The results show that, during maximal and submaximal bite an occlusal interference (about 0.5 mm) in the intercuspal position is able to disturb the almost symmetric pattern of muscular activity in the anterior temporal and masseter muscles. Further, the level of muscular activity during maximal bite decreased significantly in all muscles studied. In some subjects, the decrease of muscular activity could still be observed one week after insertion of the interfering contact. After eliminating the interference, the muscular co-ordination pattern improved and the level of muscular activity increased significantly.

Adult↗
PubMed2002

EMG activity of the masseter muscle in implant supported overdenture wearers during chewing of hard and soft food.

The influence of texture of food on the surface electromyographic (EMG) activity of the masseter muscle was investigated in a sample of mandibular implant overdenture wearers. Six experienced denture wearers (mean age 57.8 years) with mandibular overdentures supported by two implants, consented to participate in this study. Fresh raw carrots and peeled apples of similar size and weight were chosen as representing hard and soft food, respectively. The findings were in line with those earlier reported in dentate subjects and complete denture wearers in that harder foods require higher chewing rates, higher EMG activity and higher relative contraction times, accompanied by shorter cycle durations. It was also concluded that rehabilitation with implant retained mandibular dentures may result in more regular chewing patterns with higher electrical activity of the masseter muscles, thus providing improved chewing function and comfort.

Dental Implants↗
PubMed1988

Skin surface temperature over the temporomandibular joint and masseter muscle in patients with craniomandibular disorder.

Skin surface temperature was measured over the temporomandibular joint (TMJ) and over the origin of the superficial portion of the masseter muscle in 59 patients with craniomandibular disorder of different character. Forty patients suffered from disorder of muscular origin, 11 from non-specific arthritis and 8 from symptomatic osteoarthrosis. The degree of mandibular dysfunction was estimated by the clinical dysfunction score and index. The temperature was measured by a thermistor applied to the skin. The clinical dysfunction score of the patients varied between 1 and 25 units. Eleven patients had a clinical dysfunction index of I, 22 had II and 26 had III. The temperature over the TMJ varied between 31.3 degrees C and 36.7 degrees C, and over the masseter muscle between 31.1 degrees C and 35.5 degrees C. The patients with unilateral tenderness to palpation of the TMJ and who were diagnosed to have TMJ arthritis had a higher skin surface temperature over the symptomatic than non-symptomatic joint. It was concluded that tenderness to palpation of the TMJ in patients with TMJ arthritis is associated with raised skin surface temperature over the joint.

Adolescent↗
PubMed1983

The masseter muscle: the silent period and its clinical implications.

Standardized solenoid chin taps were delivered downward and upward as parallel as possible to the fibers of the superficial part of the masseter muscle and backward at a right angle to this direction. Each one of the 10 healthy subjects received 10 taps in each direction during isometric masseter muscle activity (clenching the teeth). Taps in all three directions evoked the classic jaw jerk response, M1, a short latency (mean, 8.3 msec) excitation followed by an SP (mean latency, 15.9 msec; mean duration, 42.6 msec). The SP duration varied considerably not only between subjects but also within individuals. Forty-nine percent of the SPs were divided into two parts by an EMG peak, M2, with mean latency 42 msec and mean amplitude 78 microV. Sometimes this peak marked the end of the SP. The SP duration has been claimed to be of diagnostic significance because it is longer in patients with mandibular dysfunction. It is concluded that the large variations of the parameter found in this as well as in other studies make it impossible to establish criteria for a healthy or pathologic SP duration. A carefully obtained history and thorough clinical examination are probably more reliable means to establish a correct diagnosis.

Adult↗
PubMed1992

[Provocable tumor of the cheek as a manifestation of so-called "infiltrating lipoma" of the masseter muscle].

We report on a 29-year-old male patient, who presented at our outpatient clinic with a 6-year history of progressive swelling of the right cheek. Contraction of the masseter muscle increased the swelling. MR-Imaging revealed a tumor measuring 2 x 3 cm, which was located within the masseter muscle. The histological diagnosis was infiltrating lipoma, which to our knowledge has not been described in this area before. This particular type of lipoma is extremely rare in the head and neck. The diagnostic and therapeutic management of infiltrating lipoma is discussed, and guidelines for adequate follow-up suggested. In addition, the authors review other sites of this tumor and describe its histological characteristics and differential diagnosis.

Adult↗
PubMed1991

Masseter muscle spasm in children: implications of continuing the triggering anesthetic.

This retrospective study was undertaken to examine the management and outcome of children who developed isolated masseter muscle spasm (MMS) after the administration of intravenous succinylcholine during anesthetic induction. The inhalation anesthetics used for induction were continued in all of these cases. The medical records of 68 patients (male/female ratio, 1.7:1), identified from approximately 42,000 anesthetics given during the period 1980-1989, were reviewed. Fifty-seven children (2.3-12 yr old) were diagnosed as having isolated MMS, i.e., MMS without spasm of other muscles; 11 experienced generalized rigidity in combination with MMS. Anesthetic and postoperative management of these two groups differed. The overall incidence of MMS was 0.3% of inhalation anesthetics during which succinylcholine was given. Intraoperative arrhythmias occurred in 33% of the patients who developed isolated MMS and more frequently in older children. Most children experienced some degree of hypercarbia and/or metabolic acidosis, but the significance of these abnormalities in the spontaneously ventilating, fasting child is unknown. Serum creatine kinase levels when measured 18-24 h postoperatively were elevated in all but one child (n = 45). There was no long-term morbidity and no mortality. We conclude that failure of the masseter muscles to relax after succinylcholine is not uncommon in children. Based on our experience, and accepting that MMS may be part of the clinical spectrum of malignant hyperthermia, we believe that anesthesia can be continued safely in cases of isolated MMS when careful monitoring accompanies diagnostic evaluation. This differs from the current practice of discontinuing the anesthetic or switching to a nontriggering anesthetic technique.

Anesthesia, Inhalation↗
PubMed1998

Effects of a soft diet and hypothyroidism on the oxidative capacity of the masseter muscle fibers of the young Japanese field vole Microtus montebelli.

Effects of a soft diet (reduction in mastication activity: an exogenous factor) and hypothyroidism (endogenous factors) on the oxidative capacity of the masseter muscles in the young Japanese field vole Microtus montebelli, consisting only of fast-twitch oxidative (FO) fibers in the adult vole, was investigated histochemically and electron microscopically. Oxidative enzyme activity and mitochondrial development in the muscle fibers were not affected by a soft diet, while they were suppressed by doses of propylthiouracil (PTU) (hypothyroidism). Thus, it was suggested that acquisition of the sustained contraction ability in the masseter muscles of the young vole is induced by the endogenous factors rather than the exogenous factor.

Animals↗
PubMedDate not supplied

Characterization of rabbit masseter muscle fibers.

Myosins of histochemically distinguishable single fibers of rabbit masseter muscle--type 1, 2A, 2B, and slow fibers--have been characterized by gel electrophoresis under dissociating (sodium dodecyl sulfate) and nondissociating (inorganic pyrophosphate) conditions, and by analysis of peptide maps of the heavy chains following limited proteolytic degradation. Type 2B fibers contain more LC3 homodimer than type 2A fibers; peptide maps of their heavy chain are different although the two myosins comigrate on pyrophosphate gel electrophoresis. Slow fiber myosin migrates more slowly than fast myosin and has a distinct peptide map. Differences were also found among fibers of the same histochemical type but originating in different muscles. In adductor magnus 2B myosin the LC1 + LC3 heterodimer band is the strongest, while in masseter 2B myosin the heterodimer is the weakest. Statistical considerations suggest that in masseter there is a mechanism preferentially forming the homodimers. More work is needed to determine the mechanism by which phenotypical differences occur among various fiber types in the same muscle and between corresponding fiber types in different muscles.

Adenosine Triphosphatases↗
PubMed1996

A monoclonal anticarbohydrate antibody detecting superfast myosin in the masseter muscle.

Superfast-contracting muscle fibres (II M) were identified by ATPase staining and after incubation with an antiserum raised against myosin type II M and with an antibody raised against the Galalpha1-3Galbeta1-4GlcNAc structure. II M fibres were present in masseter muscles from cat, dog and Macaca fascicularis but not in limb muscles from the same animals and not in masseter muscles from rat, pig, cow or man. Electrophoresis and staining of blots from myosin preparations showed that the anticarbohydrate antibody detected myosin heavy chains from cat masseter but not myosin heavy chains from cat biceps. The alpha-galactose specific lectin Griffonia simplicifolia isolectin B4 (GS I B4) did not stain muscle fibres or myosin heavy chains. Therefore, the epitope on myosin heavy chains defined by the anticarbohydrate antibody is presumably not Galalpha1-3Galbeta1-4GlcNAc although the antibody staining was strongly inhibited after absorption by 10mM of this trisaccharide. Antibody staining of the muscle fibres was totally inhibited by adding 10mM p-nitrophenyl beta-D-glucuronide to the incubation medium. The results thus imply that an anticarbohydrate antibody distinctively detects a carbohydrate epitope specific for myosin in superfast contracting muscle fibres from jaw-closing muscles and confirm that this epitope is not present in other muscle fibre types. This appears to be the first report on differentiated glycosylation among myosin isoforms.

Animals↗
PubMed1993

Effect of soft diet and aging on rat masseter muscle and its motoneuron.

To determine the effect of a soft diet and aging on the masticatory motor unit, we investigated the morphologic and metabolic properties of the superficial masseter muscle and its motoneurons in rats. Twenty rats were divided into four groups of five rats: rats fed a hard diet until 4 months after birth (hard, young), rats fed a soft diet until 4 months after birth (soft, young), rats fed a hard diet until 22 months after birth (hard, old), and rats fed a soft diet until 22 months after birth (soft, old). The diameter of the fast-twitch oxidative glycolytic muscle fiber was significantly smaller in the soft than the hard, and in the old than the young groups. The glycolytic enzyme (phosphofructokinase) activity of the muscle was significantly weaker in the old than the young group. There was no significant difference in soma diameter of the motoneurons between the soft and hard group, while the diameter was significantly larger in the old than in the young group. There was no significant difference in NADH-diaphorase activity of the motoneurons between the soft and hard group, while significantly less activity was demonstrated in the old than in the young group. The reduction in motor unit activity caused by the soft diet is considered to influence the morphologic and metabolic properties in the superficial masseter muscle but not in its motoneurons. The reduction in the oxidative enzyme activity of motoneurons with aging may occur regardless of the reduction in motor unit activity.

Aging↗
PubMed1999

Morphologic and biochemical changes of the masseter muscles induced by occlusal wear: studies in a rat model.

Occlusal alterations may result in changes in the functional performance of masticatory muscles. In this study, we set up an experimental model in rats to examine whether masticatory muscle abnormalities occur after a malocclusion is induced. Rats underwent unilateral amputation of the molar cusps to simulate an occlusal wear situation. The masseter muscles ipsilateral and contralateral to the amputated molars were excised at different experimental times. Sham-operated rats were used as controls. The tissue samples were studied by light and electron microscopy and morphometry. Tissue calcium content, a biochemical index of muscle injury, was also determined. The results show that occlusal dysfunction leads to microvessel constriction and clear-cut morphologic damage of muscular fibers and blood capillary endothelium, as well as to elevation of tissue calcium content, in the ipsilateral masseter muscle. These changes are likely related to muscle fatigue and ischemia. The early signs of injury do not involve the entire muscle but are mostly restricted to tissue areas rich in type I (slow) muscle fibers, which are characterized by a predominantly aerobic metabolism. The muscle damage becomes more extended and severe with time. On the other hand, the contralateral muscles show only slight alterations which are reversible with time, possibly due to an adaptive response.

Analysis of Variance↗