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At least 145 records · Page 8Linked to original sources
PubMed2003

Value of computed tomography findings in differentiating between intraosseous malignant tumors and osteomyelitis of the mandible affecting the masticator space.

OBJECTIVES: We sought to evaluate the diagnostic efficacy of computed tomography (CT) images in the differentiation between intraosseous malignant tumors and osteomyelitis spreading into the masticator space. STUDY DESIGN: A retrospective evaluation was carried out by using CT images from 12 patients with intraosseous malignant tumors and 9 patients with osteomyelitis involving the masticator space and accompanying mandibular bone destruction. The following CT observations are discussed: (1) bone destruction pattern subdivided into spotty, gross, or permeative; (2) cortical bone expansion; (3) diffuse osteosclerotic changes; (4) periosteal reaction; (5) masticator muscle involvement; (6) enlargement of the facial muscle; and (7) attenuation in the subcutaneous adipose tissue. RESULTS: The pattern of permeative bone destruction, cortical bone expansion, and the enlargement of both the masseter and medial pterygoid muscles were all observed in patients with malignant tumors. In contrast, diffuse sclerotic change and a periosteal reaction were significant observations in patients with osteomyelitis. CONCLUSION: The efficacy of CT in establishing a differential diagnosis of malignant tumors or osteomyelitis is supported by this study.

Adipose Tissue↗
PubMedDate not supplied

Masticator space abscess complicating removal of suspension wires: case report.

Masticator space abscesses have been reported more frequently in recent years. They are usually secondary to extractions of the first and second mandibular molar teeth. The use of antibiotics has changed the presentation and clinical course of these abscesses, masking the symptoms and resulting in secondary infection by resistant organisms. Therefore, selection of appropriate antibiotics is important, but surgical intervention remains the cornerstone of treatment. Suspension wires are being used widely in the treatment of midface fractures. These wires may extend from the zygomatic arch or frontal bone through the masticator space into the oral cavity to attach to arch bars. A case of masticator space abscess resulting from the removal of suspension wires is reported, and the relevant literature is reviewed. Suggestions are made for preventing and treating this complication.

Abscess↗
PubMed1989

MR imaging of muscles of mastication.

High-field MR imaging was used to study structural and physiologic alterations involving the muscles of mastication in 46 patients. Muscular abnormalities were often detected incidentally in conjunction with lesions of the CNS, cranial nerves, facial bones, and/or temporomandibular joint (TMJ). Specific pathologic alterations observed included anomalies of musculoskeletal development, muscle hypertrophy, atrophy (disuse and denervation), inflammatory disorders, injuries (including contusions, tears, and muscle rupture), posttraumatic musculoskeletal deformities, and reflex sympathetic dystrophy. Atrophy, fatty replacement, fibrosis, and contracture of selected muscles of mastication may accompany internal derangement of the TMJ in the absence of traumatic deformity. We conclude that MR is a highly accurate imaging method for detecting masticatory muscle disease. Nontraumatic anatomic and physiologic abnormalities of the muscles of mastication are uncommon disorders. Demonstrable muscle alterations frequently accompany fracture dislocations of the mandibular condyle neck and related facial bones onto which masticatory muscles attach.

Adolescent↗
PubMed2005

A case of soft tissue myoepithelial tumor arising in masticator space.

Soft tissue myoepithelial tumors of the head and neck region are very rare, and only one case of soft tissue myoepithelial tumor occurring in the masticator space has been reported in the world literature. A case of soft tissue myoepithelial tumor with benign histomorphology, but with an invasive growth pattern, occurred in the masticator space of a 46-year- old male patient. Magnetic resonance imaging of paranasal sinus/nasopharynx revealed a well-defined, lobulated heterogeneous mass with high signal intensity and dense calcification in the masticator space between the left mandible ramus and pterygoid process. Grossly, the tumor was a well- circumscribed ovoid solid mass and consisted of yellowish gray glistening firm tissue. Histologically, the tumor showed a multinodular growth pattern and consisted of epithelioid cells in chondromyxoid stroma and of spindle-shaped to ovoid cells in the hyaline stroma. The tumor cells appeared bland, and no mitosis or necrosis was found within the tumor. The tumor focally invaded to adhered bone tissue. Immunohistochemically, the tumor cells were diffusely positive for epithelial membrane antigen, smooth muscle actin, but negative for other epithelial markers. Ultrastructurally, the cytoplasm of the tumor cells contained sparse microfilaments and subplasmalemmal densities. Attenuated desmosomes were commonly seen between the tumor cells.

Humans↗
PubMed1999

Vomer as relevant factor in the mastication forces transmission system.

In the region of the posterior segment of bony palate and nasal cavities in both sides, the following three bones come together: the upper jaw, the palatal and the sphenoid bones. The perpendicular upper palate lamina laterally leans on the corpus of the upper jaw and on the wing process of the sphenoid bone. It is the posterior bony transmission system that has been selected as a separate study entity, which is otherwise a functionally inseparable part of the overall system of trajectories of mastication forces. It is a supporting element that begins at the dental alveolus of the wisdom tooth, ascends along the tuber maxillae and by the wing process of the sphenoid bone transmits the mastication load to the body of the sphenoid bone, i.e. into the mid-portion of the neurocranial base. By observing the characteristics of the vomer and measurement of distances between its morphological markings, or craniometric landmarks, together with its fitting into the harmonic analysis of face and head, the essential role of vomer has been established in regard to the trajectory system of mastication forces which has enabled us to create the basis for further biomechanical research of this phenomenon using photoelasticimetric procedures.

Bite Force↗
PubMed2000

Masticator space abnormalities associated with mandibular osteoradionecrosis: MR and CT findings in five patients.

BACKGROUND AND PURPOSE: Imaging of patients with a clinical diagnosis of mandibular osteoradionecrosis (ORN) is often performed to support that clinical suspicion, evaluate the extent of the disease, or exclude coexistent tumor recurrence. The purpose of our study was to describe the clinical, MR imaging, and CT features of five patients with mandibular ORN associated with prominent soft-tissue abnormality in the adjacent masticator muscles. METHODS: The MR and CT examinations of five patients with mandibular ORN associated with soft-tissue abnormalities in the adjacent masticator muscles were reviewed. All patients had received external beam radiotherapy for primary head and neck malignancies, with a total radiation dose range of 60 Gy to 69 Gy in 30 to 38 fractions. RESULTS: CT revealed the typical osseous findings of cortical disruption, trabecular disorganization, and fragmentation in all five patients. Abnormal diffuse enhancement of the adjacent masseter and pterygoid muscles was noted in all patients. Four patients had prominent mass-like thickening of these muscles adjacent to the osseous abnormality. Of the three patients who underwent MR imaging, all showed homogeneous abnormal T1 hypointensity, T2 hyperintensity, and intense enhancement of the bone marrow in the involved mandible. The masticator muscles adjacent to the osseous abnormality also showed abnormal T2 hyperintensity and intense diffuse enhancement on MR images. CONCLUSION: Mandibular ORN can be associated with prominent soft-tissue thickening and enhancement in the adjacent musculature. These changes can appear mass-like and are not related to tumor recurrence or metastatic disease.

Adolescent↗
PubMed2002

The masticator space infection.

The masticator space is an important suprahyoid tissue compartment. Infection of the masticator space can break through the fascia and involve the adjacent space. Severe complications including mediastinitis, pericarditis and death have been reported. The correct diagnosis and proper management are, therefore, crucial in order to reduce this complication. The authors reviewed 22 patients with masticator space infection between July 1996 and June 2001. All of the patients presented with trismus and 18 patients (81.8%) had a suspected dental cause of infection. Five patients had underlying disease; three were diabetic and two had human immunodeficiency virus (HIV) infection. High dosage intravenous antibiotics directed towards the causative microorganism were given to all of the patients. Fourteen patients underwent surgical drainage and surgical drain was positive in eleven patients (78.5%). Routine aerobic cultures were done on samples of the drained material. Bacteriology showed Streptococcus spp. the dominant microorganism in three patients, Pseudomonas spp. in one patient and no growth in ten patients. Blood culture grew Burholderia pseudomallei in one patient who responded to medical treatment. Three patients had post-operative complications but all recovered.

Adolescent↗
PubMed1997

Comparative functional morphology of mandibular forward movement during mastication of two murid rodents, Apodemus speciosus (Murinae) and Clethrionomys rufocanus (Arvicolinae).

The anatomy of the masticatory apparatus, the direction in which masticatory muscles act during mastication, and jaw muscle forces as estimated by muscle dry weight are compared between two murid rodents, the Japanese field mouse (Apodemus speciosus, subfamily Murinae) and the gray red-backed vole (Clethrionomys rufocanus; subfamily Arvicolinae). The occlusal forces exerted by the deep masseter and the anterior temporalis are large in C. rufocanus. Furthermore, in this species, the angle between the sagittal plane and the occlusal plane of the cheek teeth is larger than in A. speciosus. Therefore, a relatively large occlusal force can be generated in C. rufocanus. The estimated line of action of the anterior temporalis differs markedly between these two species. The functional significance of this difference is discussed relative to the adaptive dental characteristics for food processing, the forces required to masticate different types of food, and the forces that control mandibular forward movement.

Animals↗
PubMed1981

Medial pterygoid muscle activity during the closing and compressive phases of human mastication.

The lack of specific data correlating activity in the human medial pterygoid muscle with displacement of the jaw during mastication, and the hint of possible differences in function between certain mammalian species, prompted a study of unilateral mastication in six adult subjects. Muscle activity in the medial pterygoid, masseter, and anterior temporal muscles was recorded simultaneously with three-dimensional movement of an incisor point on the mandible. Signals from muscles and displacement transducer were sampled by a disc-based computer system programmed to analyze data averaged over 30 chewing cycles on each side and in some instances over 30 open-close and clench cycles. Patterns of medial pterygoid activity were consistent for the group as a whole, demonstrating activation of both muscles early in the closing cycle with strong ipsilateral muscle activity before and throughout the intercuspal phase of the cycle, reappearing in some subjects just before the end of intercuspation. Medial pterygoid activity mirrored masseter and anterior temporal activity only during certain phases of the closing cycle, suggesting that these muscles should be considered as being selectively coactivated with, rather than synergists of, the major elevators of the jaw. The muscles were active during horizontal components of movement of the incisor teeth in chewing, but were inactive during the open-close and clench task despite vigorous contraction of the masseter muscles. Overall, the observations complement previous reports of medial pterygoid muscle activity in humans. They also confirm, for these muscles at least, a general similarity between man and the little brown bat, a relationship hitherto suspected but unsubstantiated.

Electromyography↗
PubMed1989

Jaw movements and muscle activity during mastication in growing rabbits.

To investigate the biomechanical effects of juvenile growth changes in the rabbit masticatory apparatus a comparison was made of mastication in just-weaned and adult animals. Mandibular movements in two planes were registered by cineradiography. Masticatory muscle activity was recorded by fine-wire electromyography. The same pattern of unilateral mastication was present in the two ages. The most important changes in the jaw movements are 1) a decrease of jaw opening speed and chewing frequency and an increase in jaw opening time, 2) a decrease in maximum gape in soft food and an unaltered gape in small-particle hard food, and 3) an increase in lateral jaw excursion, mainly due to a more pronounced movement of the jaw to the balancing side (lingual phase). The contraction patterns were basically similar in the two ages. The higher chewing frequency in young animals was attained by a larger degree of overlap between opening and closing muscle activities. Young animals used relatively more EMG activity to chew hay, the hardest food. The changes in opening speed, gape, and chewing frequency are consistent with earlier predictions from the morphological changes, and so is the extra activity needed to chew hard food. The increase in lateral excursion was not predicted. It is suggested to be caused by cheek teeth wear, making possible smooth occlusal guidance of the jaw at the balancing side. Some of the changes in juvenile morphology can be viewed as adaptations to a changing diet.

Aging↗
PubMed1980

Quantitative assay of electromyograms during mastication in domestic cats (Felis catus).

Mastication has been studied by cinematography with synchronized electromyography (computer quantified and analyzed), while unanesthetized, freely feeding cats (Felis catus) were reducing equivalent-sized chunks of raw and cookded beef and cooked chicken. Cats reduce food on one side at a time, and their chewing cycles show horizontal and anteroposterior deflections. Food objects are shifted from side to side by lateral jerks of the head and movements of the tongue. During the opening phase, the lower jaw is rotated relatively straight downward, and the digastric muscles are active in bilateral symmetry. Near the end of opening, the head jerks upward, both zygomaticomandibulares start to fire, and opening acceleration of the mandible decreases. Closing starts with horizontal displacement of the mandibular canines toward the working side, accompanied by asymmetrical activities from the working side deep temporalis and the balancing side medial pterygoid, as well as a downward jerk of the head. As closing proceeds the mandibular canines remain near the working side and the working side zygomaticomandibularis and deep masseter are very active. Near the end of closing, the mandibular canine on the working side moves toward the midline, and adductors, digastrics, and lateral pterygoids of both sides are active. The adductors of the working side are generally more active than those of the balancing side. During a reduction sequence, the number and shape of the masticatory cycles, as well as movements of the head, during a reduction sequence are affected significantly by food type. As reduction proceeds, the duration of bite and the muscular activity (as characterized by number and amplitude of spikes) change significantly among muscles of the working and balancing sides. The adductors of the working side are generally most active when cats chew raw beef, less for cooked beef, and least for cooked chicken. In general, the adductor activity reflect food consistency, whereas that of the digastrics and lateral pterygoids reflects more the vertical and lateral displacements of the mandible. Statistical analysis documents that the methods of electrode insertion and test give repeatable results for particular sites in different animals. Thus, it should be possible to compare these results with those produced while other mammals are masticating.

Animals↗
PubMed1989

Patterns of activity of perioral facial muscles during mastication in man.

The activity of buccinator, orbicularis oris superior and inferior, quadratus and triangularis muscles was recorded by surface and needle electrodes during spontaneous unilateral mastication of small or large boluses. Their activity was compared with that of the masticatory muscles masseter and digastric, and with the vertical movement of the jaw. The facial muscles were active during mastication, displaying both tonic and phasic activity. Although the cyclic activity was broadly linked to lowering of the jaw, there was no strict time correspondence between the activity of the various facial muscles themselves, or between the activity of the facial muscles and the digastric. The timing and amplitude of facial muscle activity were affected by the duration of the masticatory cycle, the side on which chewing took place, the size of the bolus, and whether or not lip to lip contact was made.

Adult↗
PubMed1992

Coordination of mastication and swallowing.

The coordination of mastication, oral transport, and swallowing was examined during intake of solids and liquids in four normal subjects. Videofluorography (VFG) and electromyography (EMG) were recorded simultaneously while subjects consumed barium-impregnated foods. Intramuscular electrodes were inserted in the masseter, suprahyoid, and infrahyoid muscles. Ninety-four swallows were analyzed frame-by-frame for timing of bolus transport, swallowing, and phases of the masticatory gape cycle. Barium entered the pharynx a mean of 1.1 s (range -0.3 to 6.4 s) before swallow onset. This interval varied significantly among foods and was shortest for liquids. A bolus of food reached the valleculae prior to swallow onset in 37% of sequences, but most of the food was in the oral cavity at the onset of swallowing. Nearly all swallows started during the intercuspal (minimum gape) phase of the masticatory cycle. Selected sequences were analyzed further by computer, using an analog-to-digital convertor (for EMG) and frame grabber (for VFG). When subjects chewed solid food, there were loosley linked cycles of jaw and hyoid motion. A preswallow bolus of chewed food was transported from the oral cavity to the oropharynx by protraction (movement forward and upward) of the tongue and hyoid bone. The tongue compressed the food against the palate and squeezed a portion into the pharynx one or more cycles prior to swallowing. This protraction was produced by contraction of the geniohyoid and anterior digastric muscles, and occurred during the intercuspal (minimum gape) and opening phases of the masticatory cycle. The mechanism of preswallow transport was highly similar to the oral phase of swallowing. Alternation of jaw adductor and abductor activity during mastication provided a framework for integration of chewing, transport, and swallowing.

Adult↗
PubMed1997

Bilateral experimental muscle pain changes electromyographic activity of human jaw-closing muscles during mastication.

The effects of bilateral experimental muscle pain on human masticatory patterns were studied. Jaw movements and electromyographic (EMG) recordings of the jaw-closing muscles were divided into multiple single masticatory cycles and analyzed on a cycle-by-cycle basis. In ten men simultaneous bilateral injections of hypertonic saline (5%) into the masseter muscles caused strong pain (mean+/-SE: 7.5+/-0.4 on a 0-10 scale), significantly reduced EMG activity of jaw-closing muscles in the agonist phase, and significantly increased EMG activity in the antagonist phase. Nine of the subjects reported a sensation of less intense mastication during pain. Injections of isotonic saline (0.9%) did not cause pain or significant changes in masticatory patterns. The influence of higher brain centers on conscious human mastication can not be discarded but the observed phase-dependent modulation could be controlled by local neural circuits and/or a central pattern generator in the brain stem which are capable of integrating bilateral nociceptive afferent activity.

Adult↗
PubMed2006

Dental microwear in relation to changes in the direction of mastication during the evolution of Myodonta (Rodentia, Mammalia).

Observations of dental microwear are used to analyse the correlation between changes in molar tooth crown morphology and the direction of masticatory movement during the evolution of Myodonta (Rodentia, Mammalia). The studied sample includes 36 specimens representing both superfamilies of Myodonta (Muroidea and Dipodoidea) spanning 16 dipodoid and 9 muroid species. Microscopic scratches on occlusal surfaces resulting from contact between opposite teeth during mastication are analysed. Using these features, we determine the direction of masticatory movements. Microwear patterns display diverse orientations among Dipodoidea: oblique in Sicistinae, Euchoreutinae and Zapodinae, propalinal in Dipodinae and intermediary in Allactaginae. Similarly, Muroidea exhibit the following orientations: oblique in Cricetinae and propalinal in Arvicolinae, Cricetomyinae, Gerbillinae and Murinae. These various chewing types illustrate different evolutionary grades within the superfamilies. Acquisition of the antero-posterior masticatory movement in Dipodoidea is related to flattening of the molar occlusal surface. However, in some muroid subfamilies, this direction of mastication is associated with low-crowned and cuspidate molars (Cricetomyinae, Murinae).

Animals↗
PubMed1986

Jaw movements and patterns of mandibular bone strain during mastication in the monkey Macaca fascicularis.

Small amalgam fillings were placed in maxillary and mandibular second molar and canine teeth for cine-radiographic analysis. The rosette strain gauges were bonded bilaterally to mandibular cortical bone below the second or third molars. The monkeys were placed in a restraining chair that did not restrict normal head, neck or jaw movements; they were fed various foods and the bone-strain data recorded. Simultaneous jaw movements were recorded with cine-radiographic apparatus synchronized with the bone-strain recordings. During vigorous mastication, the transition between fast close and the power stroke was correlated with a sharp increase in masticatory force. In most instances, the jaws were maximally-loaded prior to maximum intercuspation, i.e. during the buccal phase (phase I) of occlusion. The macaques swallowed frequently throughout a chewing sequence and these swallows were intercalated into the chewing cycle toward the end of the power stroke. Such swallows had little effect on the magnitude or direction of peak principal strains during the power stroke. Bone-strain data suggested that unloading patterns during the power stroke of mastication were largely a function of the relaxation time of the jaw adductors. The period from 100 per cent peak strain to 50 per cent peak strain during unloading closely approximated to the half-relaxation time of the whole adductor jaw muscles.

Animals↗
PubMed1989

The relationship between masseter force and masseter electromyogram during mastication in the monkey Macaca fascicularis.

In five adult monkeys, electromyograms (EMGs) were recorded from bipolar surface electrodes positioned over the superficial masseter and from bipolar fine-wire electrodes within both the superficial and deep masseter. Relative masseter force was estimated by measuring surface bone strain from the lateral aspect of the zygomatic arch using rosette strain gauges. Multiple step-wise regression procedures demonstrated that peak values of the averaged masseter EMG could often explain a considerable amount of the variation of peak relative masseter force during mastication, i.e. r2 values ranged from 0.23 to 0.96 for the various single-electrode models and R2 values ranged from 0.78 to 0.96 for the various multiple-electrode models. The r2 values for relative masseter force and EMG data from the surface electrodes ranged from 0.69 to 0.96, and, on average, EMG data from surface electrodes provided somewhat more information about overall relative muscle force than data from fine-wire electrodes. The R2 values for a two-electrode model, consisting of data from surface electrodes over the superficial masseter and fine-wire electrodes in the posterior portion of the deep masseter, ranged from 0.78 to 0.95. The latency between the averaged surface EMG and relative muscle force was determined and the data indicated that the surface EMG usually preceded muscle force. This latency tended to decrease gradually throughout the entire power stroke of mastication. At peak values, the surface EMG preceded muscle force by about 22 ms. Towards the end of the power stroke, i.e. the 25% of peak values during unloading, muscle force may actually precede the average EMG.

Animals↗
PubMed1988

Phase-linked modulation of excitability of presynaptic terminals of low-threshold afferent fibers in the inferior alveolar nerve during cortically induced fictive mastication in the guinea pig.

Excitability of presynaptic terminals of low-threshold primary afferent fibers in the inferior alveolar nerve was tested in the trigeminal spinal nucleus of the ketamine-anesthetized, paralyzed guinea pig, by Wall's method. Fictive mastication was induced by repetitive stimulation of the cortical masticatory area, and was monitored by rhythmical burst activity in the jaw-opening anterior digastric motoneuron pool. The excitability was rhythmically modulated in a phase-linked manner during the masticatory cycle: it was decreased coincidentally with the digastric burst activity (jaw-opening phase) and increased during the middle and late periods of the interburst phase (jaw-closing phase) of the masticatory cycle. The results imply that presynaptic modulation of synaptic transmission of peripheral inputs from primary afferents to interneurons in the jaw-opening reflex pathway may contribute to the rhythmical modulation of the jaw-opening reflex evoked by innocuous stimulation of the intraoral structures during mastication; presynaptic inhibition contributing to the depression of the jaw-opening reflex during the jaw-closing phase and presynaptic facilitation to its enhancement during the jaw-opening phase.

Afferent Pathways↗