SEARCH · Search PubMed

Results for “MASTICATION”

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.

SourceResearch connectionFrom yearThrough year

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

At least 235 records · Page 13Linked to original sources

PubMed1995

Interocclusal splint designed to reduce tenderness in lateral pterygoid and other muscles of mastication.

When a patient has discomfort in the muscles of mastication, a palpation test of the lateral pterygoid muscles is positive, and a stress test is positive, the dental occlusion may be a partial cause. The resin splint described here is designed to permit interocclusal contact exclusively at the center of the arches. This device has been shown to reduce tenderness in the lateral pterygoid and other muscles of mastication quickly, usually in 5 to 10 minutes. The splint and its advantages and disadvantages are described.

Contraindications↗

PubMed2002

The muscles of mastication in the caspian seal (Phoca caspica).

The muscles of mastication and their related skull characters in the Caspian seal (Phoca caspica) were anatomically examined and compared with those of the Baikal (Phoca sibirica) and ringed (Phoca hispida) seals. A well-developed masseter muscle was observed in the Caspian seal, whereas the temporal muscle consisted of thin bundles. The skull of the Caspian seal possessed the same thin frontal bone and the dorso-ventrally developed zygomatic arch found in the Baikal seal that are required to install the enlarged eyeball into the orbit. The temporal bone was not robust, and the digastric muscle was well-developed in the ventral space of the auditory bulla. The present results suggest that the skull form of the Caspian seal has changed morphologically from its ringed seal-like ancestors, and suggest that the evolutionary strategy of the muscles of mastication in the Caspian seal is principally consistent with that of the Baikal seal.

Animals↗

PubMed2001

Oxidative state and histological changes in muscles of mastication after conditioning training.

Stress due to endurance training of striated muscles leads to adaptive changes in the distribution of muscle fiber types (i.e. ratio of type I and type II fibers). Moreover, severe training leads to tissue hypoxia and oxidative stress in muscles. In the current study, we examined the relationship between histological changes and oxidative state in muscles of mastication during the acute adaptation phase to a sustained muscle load. Six domestic pigs received build-ups on the molar teeth in order to induce a sustained load of the muscles of mastication for a duration of four weeks. Afterwards the masseter (M1, M2, M3), medial pterygoid (PM), temporal (TP1, TP2), and geniohyoid muscles (GH) were removed and the fiber type distribution was determined by enzyme histochemistry. Additionally, the tissue content of glutathione and lipid peroxidation (LPO) products were measured. The above treatment led to muscle fiber transformation of type II into type I (M1, M2, TP2, PM) and a decrease of the GSH content (M1, M2 and TP2). The changes in the GSH/GSSG ratio were in accordance with the changes in proportions of muscle fiber types, with the lowest GSH/GSSG ratios in the most stressed muscles of the treated animals. No significant changes in LPO products were found. The decrease of the GSH/GSSG ratio in the most stressed muscles indicates an increased intracellular oxidative stress, which may be caused by tissue hypoxia during the chronic phase of muscle adaptation.

Adaptation, Physiological↗

PubMed2005

Volumetric change of the muscles of mastication following resection of mandibular angles: a long-term follow-up.

Mandibular angle resection is an accepted procedure for the correction of square face appearance due to mandibular angle prominence. Long-term follow-up of the changes in volume that occurs in the muscles of mastication and osseous structures has been inadequate in the literature. In this study, 3-dimensional computed tomography data were used to extract the mandible, masseter, medial pterygoid, and lateral pterygoid muscles for assessment of the volumetric changes that took place after angle reduction in 7 patients (14 hemimandibles) with an average age of 24.9 years and a mean follow-up time of 4.5 years. All measurements were performed twice to assure accuracy, with a difference of 1.2 +/- 1.1% noted. The hemimandible volume was reduced by 12.6% immediately after the reduction procedure and 8.2% at final follow-up. Osseous regeneration was observed as thickening of the bone and partial regrowth of the angles. None of the 14 hemimandibles had a complete return of the preoperative angular shape. The volumetric changes that occurred in the muscles of mastication were inconsistent among the patients. The masseter muscle was reduced by 5.2%, the medial pterygoid muscle was reduced by 14.4%, and the lateral pterygoid muscle was increased by 5.7% at final follow-up. The medial pterygoid muscle change was more significant than that of the masseter muscle (P = 0.00361). The objective findings of this study were not in agreement with the conventional thought and clinical impression that the masseter muscle becomes atrophic after mandibular angle resection. Only a slight reduction occurred in some patients in the volume of the muscles, with some actually displaying a slight increase. The end result was a satisfactory esthetic outcome for the patients in the long term despite the minor changes in muscle volume and slight bony regeneration that occurred.

Adolescent↗

PubMed2004

MR features of masticatory muscles in adenoid cystic carcinoma involving the masticator space.

Adenoid cystic carcinoma (ACC) is known for its slow-growing but severely infiltrative nature with little tissue reaction. Although the masticatory muscles are often involved, their imaging features have not been well elucidated. We hereby report three patients with widespread ACC, which initially appeared with trismus and/or temporomandibular symptoms and involved the masticator space. Possible features of masticator space involvement are presented on magnetic resonance (MR) images. Masticatory muscle changes on MR images consisted of two aspects, namely, denervation changes and direct tumour invasion.

Adult↗

PubMed2000

Adaptation of the muscles of mastication to the flat skull feature in the polar bear (Ursus maritimus).

The muscles of mastication of the polar bear (Ursus maritimus) and those of the brown bear (U. arctos) were examined by anatomical approach. In addition, the examination of the skull was carried out in the polar bear, brown bear and giant panda (Ailuropoda melanoleuca). In the polar bear, the rostro-ventral part of the superficial layer of the M. masseter possessed the abundant fleshy portion folded in the rostral and lateral directions like an accordion. Moreover, the rostro-medial area of the superficial layer became hollow in the nuchal direction when the mouth was closed. The M. temporalis of the polar bear covered up the anterior border of the coronoid process of the mandible and occupied the almost entire area of the cranial surface. The M. pterygoideus medialis of the polar bear was inserted on the ventral border of the mandible and on the ventral part of the temporal bone more widely than that of the brown bear. As results of our measurements of the mandible, an effect of the leverage in the polar bear was the smallest in three species. In the polar bear, the skull was flat, and the space between zygomatic arch and ventral border of the mandible, occupied by the M. masseter was the narrowest. It is suggested that the muscles of mastication of the polar bear is adapted to the flat skull feature for supplementing the functions.

Animals↗

PubMed1991

Mortality of mastic asphalt workers.

This study was conducted to investigate the adverse health effects of exposure to bitumen fumes. A cohort of 679 mastic asphalt workers was followed from 1959 to 10 June 1986, during this period 169 deaths occurred. The overall standardized mortality ratio (SMR) was 163 (95% confidence interval (95% CI) 141-190), the SMR was 225 (95% CI 172-288) for cancer and 223 (95% CI 130-358) for external causes. Among persons aged 40 to 89 years, significant increases were seen for lung cancer (SMR 290, 95% CI 188-429), nonpulmonary cancer (SMR 200, 95% CI 141-276), and liver cirrhosis (SMR 467, 95% CI 188-962). Bronchitis, emphysema, and asthma also occurred in excess (SMR 207, 95% CI 95-393). In conclusion, the inhalation of bitumen fumes may have contributed to the elevated mortality from cancer and respiratory diseases among mastic asphalt workers.

Adolescent↗

PubMed1992

CT and MR imaging of primary tumors of the masticator space.

A retrospective study of CT and MR examinations in 14 patients with benign and malignant tumors originating in the masticator space is presented. At presentation, 12 patients revealed tumor extension to adjacent regions and spaces. Perineural tumor spread along trigeminal nerve branches to the cavernous sinus and orbits was combined with facial pain, and/or numbness, ophthalmoplegia, and exophthalmus. Detailed analysis of tumor growth and spread, enhancement and signal features at CT and MR imaging indicated the tumor histology was, with a few exceptions, nonspecific. More extensive growth and bone destruction was noted only among malignant tumors. MR imaging was found superior to CT in delineating tumor extension due to better soft tissue contrast resolution and multiplanar imaging. Posttreatment examinations were available in 11 patients and showed long-standing regional edema of the adjacent temporal lobe and masticator muscles in 4 out of 5 patients without clinical evidence of tumor. In 6 patients, CT and MR features were found almost unchanged with only small size differences after various forms of treatment.

Adolescent↗

PubMed2006

[Muscular power of masticating muscles and mandibular osteoporosis].

Whereas the most powerful stimuli for bone formation is supposed to be a stretching of muscles, Frost HM classified the effect of muscle on bone mineral density (BMD) into various types: 1. age-related loss of bone mineral density (BMD) is partly due to loss of muscular wasting, 2. the increase of BMD in obesity is due to the increase in muscular power to support the increased body weight and 3. the decrease of BMD in chronic wasting disease is partly due to the decrease in muscular power. Likewise, the decrease in BMD in mandibular alveolar bones will be partly due to the decrease in the power of masticating muscles, if such exists. A case report of mitochondrial encephalo-myopathy associated with impaired function of cranial nerves involving trigeminus nerves and impaired function of masticating muscles and dysphagia. This patient showed decrease in alveolar BMD and atrophy of mandibular.

Adult↗

PubMed1998

Surgical treatment of cancer extending from the retromolar fossa to the masticator space.

Cancer extending from the retromolar fossa to the masticator space with neck metastasis (T4N2M0, Stage IV) was surgically removed en bloc by maxillectomy using a mandibular swing technique. This approach allowed a wide surgical view and was useful as handling the external and internal pterygoid muscles and upper neck dissection could be combined. Though there have been several surgical approaches to the masticator space, in the case of tumors which are commonly malignant there, this approach is useful and satisfactory.

Carcinoma, Squamous Cell↗

PubMed1994

Jaw muscle function and wishboning of the mandible during mastication in macaques and baboons.

An analysis of in vivo bone strain indicates that the mandibular symphysis of macaques experiences lateral transverse bending or "wishboning" during the power stroke of mastication, and this loading regime results in relatively intense concentrations of stress along the lingual aspect of the symphysis (Hylander 1984, 1985). It has been hypothesized that peak wishboning of the macaque mandible, which probably occurs at the very end of the power stroke, that is, after the initial occurrence of maximum intercuspation, is associated with the late peak activity of the balancing-side deep masseter muscle coupled with the rapid decline in the activity of the balancing-side medial pterygoid and superficial masseter muscles (Hylander et al., 1987). The main purpose of this study is to do a detailed analysis of the electromyographic (EMG) activity of the deep and superficial masseter and medial pterygoid muscles so as to provide a better understanding of the external forces associated with wishboning. This was done by recording and analyzing EMG activity from the superficial masseter, deep masseter, and medial pterygoid muscles in macaques and baboons. EMG activity was recorded from bipolar fine-wire electrodes, and the data were quantified and analyzed using digital techniques. The EMG data clearly support our original observation that the balancing-side posterior deep masseter exhibits peak EMG activity relatively late in the power stroke at a time when activity is rapidly decreasing in the balancing-side medial pterygoid and superficial masseter muscles. Moreover, peak activity of the balancing-side deep masseter occurs at a time when the activity of the working-side deep and superficial masseter and medial pterygoid muscles are also decreasing. Thus, these data are consistent with the hypothesis that wishboning of the mandible is influenced significantly by the late occurrence of force from the balancing-side deep masseter. The EMG data also indicate that residual force from the relaxing superficial masseter may contribute significantly to wishboning. Finally, patterns of wishboning are not fully accounted for by our EMG analysis of the deep and superficial masseter and medial pterygoid muscles. This is probably because the lateral ptergyoids, which can either counter increased wishboning or actually cause reverse wishboning, were not included in our EMG analysis. The EMG data demonstrate that jaw-closing muscle recruitment patterns for macaques and baboons differ from those of humans. Nevertheless, in spite of these differences, it appears, based on previously published EMG data, that the human symphysis may also experience wishboning.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

Monosynaptic innervation of trigeminal motor neurones involved in mastication by neurones of the parvicellular reticular formation.

In order to determine whether neurones in the parvicellular reticular formation are in direct synaptic contact with motor neurones innervating masticatory muscles, a combined retrograde and anterograde transport study was carried out in the rat at both light and electron microscopic levels. The animals received injections of the retrograde tracers wheat germ agglutinin conjugated to horseradish peroxidase or cholera toxin B conjugated to horseradish peroxidase into the masticatory muscles and of the anterograde tracer biocytin into the ipsilateral parvicellular reticular formation. The trigeminal motor nucleus was then examined for both anterograde and retrograde labelling in the light and electron microscopes. Retrogradely labelled motor neurones were identified in the trigeminal motor nucleus. They were large and their locations within the nucleus depended on the muscle injected. In addition, terminals anterogradely labelled with the biocytin that was injected in the parvicellular reticular formation were identified throughout the motor nucleus. At the electron microscopic level, the retrogradely labelled cells were found to receive input both from distinct types of unlabelled terminals and from terminals that were anterogradely labelled from the parvicellular reticular formation. The labelled terminals comprised one of the four classes of afferent terminals, being 1-2 microns in diameter and densely packed with spherical vesicles. They formed mostly asymmetrical but also symmetrical synapses with the labelled perikarya and dendrites. Anterogradely labelled terminals were also observed to form both symmetrical and asymmetrical synaptic contacts with unlabelled structures in the motor nucleus. It is concluded that neurones in the parvicellular reticular formation form direct synaptic contact with motor neurones of masticatory muscles. This pathway may represent the anatomical substrate by which the reticular formation exerts at least part of its influence on mastication. Since the parvicellular reticular formation receives input from the substantia nigra pars reticulata, it is possible that this pathway represents a system whereby the basal ganglia directly influence orofacial movement.

Animals↗

PubMedDate not supplied

Claudication on mastication following bilateral external carotid ligation.

Ligation of both external carotid arteries to control epistaxis can produce a decrease in the blood supply of the muscles of mastication sufficient to cause pain typical of claudication while chewing. We report 3 cases of this complication. We advocate that this procedure be used only in special circumstances.

Adult↗

PubMedDate not supplied

Differential mastication kinematics of the rabbit in response to food and water: implications for conditioned movement.

Analysis of naturalistic chewing patterns may provide insight into mapping the neural substrates of jaw movement control systems, including their adaptive modification during the classically conditioned jaw movement (CJM) paradigm. Here, New Zealand White rabbits were administered food and water stimuli orally to evaluate the influence of stimulus consistency on masticatory pattern. Chewing patterns were recorded via video camera and movements were analyzed by computerized image analysis. The mandibular kinematics, specifically the extent of dorsal/ventral, medial/lateral, and rostral/caudal movement, were significantly larger in food-evoked than water-evoked chewing. Water-evoked chewing frequency, however, was significantly higher than that of food-evoked movements. In light of known cortical mastication modulatory centers, our findings implicate different neural substrates for the responses to food and water stimuli in the rabbit. A detailed delineation of jaw movement patterns and circuitry is essential to characterize the neural substrates of CJM.

Animals↗

PubMed2005

Identification of c-Fos immunoreactive brainstem neurons activated during fictive mastication in the rabbit.

In the present study we used the expression of the c-Fos-like protein as a "functional marker" to map populations of brainstem neurons involved in the generation of mastication. Experiments were conducted on urethane-anesthetized and paralyzed rabbits. In five animals (experimental group), rhythmical bouts of fictive masticatory-like motoneuron activity (cumulative duration 60-130 min) were induced by electrical stimulation of the left cortical "masticatory area" and recorded from the right digastric motoneuron pool. A control group of five animals (non-masticatory) were treated in the same way as the experimental animals with regard to surgical procedures, anesthesia, paralysis, and survival time. To detect the c-Fos-like protein, the animals were perfused, and the brainstems were cryosectioned and processed immunocytochemically. In the experimental group, the number of c-Fos-like immunoreactive neurons increased significantly in several brainstem areas. In rostral and lateral areas, increments occurred bilaterally in the borderzones surrounding the trigeminal motor nucleus (Regio h); the rostrodorsomedial half of the trigeminal main sensory nucleus; subnucleus oralis-gamma of the spinal trigeminal tract; nuclei reticularis parvocellularis pars alpha and nucleus reticularis pontis caudalis (RPc) pars alpha. Further caudally-enhanced labeling occurred bilaterally in nucleus reticularis parvocellularis and nucleus reticularis gigantocellularis (Rgc) including its pars-alpha. Our results provide a detailed anatomical record of neuronal populations that are correlated with the generation of the masticatory motor behavior.

Anesthesia↗

PubMed2004

Video evaluation for mastication validation in persons with Down's syndrome.

This article reports the second stage of a validation process. It investigates the discriminatory ability of three video indicators of mastication for a group of people with Down's syndrome, representing a target group with neurological disabilities. The variables were generated through video recordings of 11 adults with Down's syndrome and 12 healthy subjects eating four natural foods varying in hardness. The collected variables were masticatory time, number of masticatory cycles, and number of open masticatory cycles. The analytical approach attempts to test four hypotheses exploring the variations of the video indicators according to food hardness for both groups. It was demonstrated that masticatory time and the number of masticatory cycles have very strong, positive correlations and the number of open masticatory cycles has a fair, positive correlation with the food hardness rankings for both groups. Video evaluation of the test variables using real foods in people with Down's syndrome was found to be a valid means of evaluating aspects of their masticatory function.

Adult↗

PubMed1975

Muscles of mastication in small children: an electromyographic analysis.

The temporalis, masseter, and depressor muscles of fifteen normal children were studied electromyographically to determine their activities during the position of resting tonus, during various movements of the mandible, and during the act of swallowing. Analysis of our results led to the following conclusions: 1. Resting tonus of the mandible does not depend on neuromuscular activity in the three portions of the temporalis, masseter, and depressor muscle group; they were inactive bilaterally. 2. Opening of the jaw either slowly or maximally, and against resistance, is brought about by the contraction of the depressor muscle group. 3. Closing of the jaw quickly is brought about mainly by greater contraction of the masseter muscle, and slightly by contraction of the temporalis. 4. Closing the jaw quickly with occlusal contact of the teeth is effected by the temporalis and masseter muscles. 5. Protraction of the jaw is performed by contraction of the masseter muscles. The depressor muscle group contracts to maintain the slight depression followed by the protraction. 6. Swallowing saliva and water is accompanied by contractions of the depressor muscle group. 7. Incisor chewing of gum and peanuts mainly recruits marked contraction of the masseter muscle. Some slight-to-moderate activity is achieved by the temporalis. The depressor muscle group acts in antagonism with the elevator muscles. 8. Chewing gum on the right and left molar sides and normal mastication are effected by the contraction of the temporal and masseter muscles. The suprahyoid muscle group acts in antagonism with the elevator muscles. 9. Normal children with deciduous teeth have patterns that are similar to those of normal adults.

Child↗

PubMed1983

Methods for analysing the breakdown of food in human mastication.

A method is described for measuring the rate at which carrot particles are broken down in chewing. In 10 subjects, this rate declined progressively throughout mastication. This was analysed in terms of two variables: (a) the intra-oral selection of particles for fracture, (b) the size distribution of fractured pieces of those particles. When intra-oral selection was measured by different methods, it depended mainly upon particle size. The selection of small particles might depend on the number of chews taken after the food was placed in the mouth. The size distribution of fractured pieces was obtained from one chew on three different particle sizes. These distributions were partially described by two different equations whose characteristics suggest that carrot particles are subjected to only one breakage per chew and that the number of fragments formed per breakage is small. It is suggested that the cusps present on the post-canines were important in determining this breakage pattern, and that the dependence of selection on particle size was primarily responsible for the decline in the rate of breakdown with increasing numbers of chews.

Adult↗