[Quantitative analysis of the structural organization of muscle tissue in unilateral hypertrophy of the masticatory muscle].
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Adult↗
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Effects of 5 days of repeated submaximal clenching on masticatory muscle pain and tenderness: an experimental study.
The hypothesis of this short-term study was that repeated episodes of clenching at submaximal bite force levels can induce a progressive increase in pain and tenderness in masticatory muscles. On each day for 5 consecutive days, 10 women clenched on a bite force transducer for 15 minutes at 25% of their maximal bite force. The development of pain, tenderness, and unpleasantness in the masticatory muscles was evaluated with use of 10-cm visual analog scales (VAS) and the McGill Pain Questionnaire (MPQ). Pain detection thresholds (PDT) and pain tolerance thresholds (PTT) to percutaneous pressure stimuli were measured in the masseter and anterior temporalis muscles. Maximal voluntary bite force to brief clenches were assessed. The results showed moderate levels of pain (mean +/- SE; 5.3 +/- 1.0), tenderness (5.2 +/- 1.0), unpleasantness (5.8 +/- 0.8), and MPQ scores (16.4 +/- 4.9) immediately after the submaximal clenching task on the first day. The following days, the clenching tasks did not increase these scores; in contrast, there were significant decreases on day 5 in both pain intensity (-49.8% +/- 14.6%), tenderness (-46.1% +/- 14.2%), unpleasantness (-50.4% +/- 8.5%), and MPQ scores (-45.8% +/- 13.3%) (P < .05) when compared to day 1. The clenching procedure failed to induce a progressive increase in pain and tenderness in the masticatory muscles during 5 days. None of the evaluated parameters from this study suggested the start of a vicious cycle.
Adult↗
Deep thermometry of temporomandibular joint and masticatory muscle regions.
A study was designed to measure noninvasively the deep temperature of the temporomandibular joint (TMJ) region and corresponding regions of the masticatory muscles at rest. With a transcutaneous probe, the deep thermometry of the right and left anterior (Ta) and the posterior portion (Tp) of the temporal muscles, the mid-portion of the superficial belly of the masseter muscles (Mm), and the TMJ regions were measured. In 20 normal male subjects, the deep temperature of the Ta region (mean 36.342 degrees C), the Tp region (mean 36.345 degrees C), and the TMJ region (mean 36.06 degrees C) was higher than that of the Mm region (mean 35.897 degrees C) at rest. In addition, no differences in the deep temperature were observed between the right and left Ta, Tp, Mm, and TMJ regions at rest. All of the normal subjects showed differences between the right and left TMJ region of less than 0.3 degrees C. In 10 patients with craniomandibular disorders, however, eight patients showed differences of more than 0.3 degrees C between the asymptomatic and asymptomatic TMJ region. Because of high sensitivity and specificity, the deep thermometry measurements can provide useful non-invasive information.
Adolescent↗
[A method for performing stimulation electromyography of the masticatory muscles in man].
A principal block scheme of an apparatus complex is suggested and a method for examination of masticatory muscle function is described. The method is based on electrostimulation of masticatory nerve followed by registration and analysis of the masticatory muscle action evoked potentials. The block scheme of the apparatus complex includes a universal electrostimulator ESU-2. Examinations of 30 healthy volunteers and 30 patients with unilateral fractures of the mandible helped define the major parameters of stimulation electromyography. The patients were treated by splints applied on the teeth with fixation on both jaws. By day 28 of the investigation the M-response amplitude dropped more than twofold and its length by 1.5 times as against the mean parameters in health.
Action Potentials↗
Canonical correlations between masticatory muscle orientation and dentoskeletal morphology in children.
In order to identify associations between the orientation of the superficial masseter and temporalis muscles and dentoskeletal morphology in a sample of fifty-five children with various malocclusions, eight muscle-orientation variables (relative to the occlusal plane) and twenty-three dentoskeletal variables were evaluated from lateral head films. The thirty-one measurements were reduced to six muscle-orientation and sixteen dentoskeletal variables by a principal component analysis. Three canonical correlations were identified between the muscle orientation and dentoskeletal variable groups at the 0.05 level of significance and canonical loadings were determined for each set of variables. The first canonical correlation (r1 = 0.931) represents a growth-related correlation factor between the masticatory muscle insertion positions relative to the occlusal plane and the dimensional and positional changes of craniofacial structures during growth. The second canonical correlation (r2 = 0.846) may account for an operational artifact in the geometric measurement process, and the third canonical correlation (r3 = 0.813) suggests an association between superficial masseter muscle orientation relative to the occlusal plane and mandibular form. This report confirms the usefulness of multivariate statistical methods to extract latent associations between muscle orientation and craniofacial morphology; the results obtained suggest a contribution from the geometric orientation of the masticatory muscles to the development and maintenance of the dentoskeletal system.
Adolescent↗
[A histomorphologic and enzyme histochemical study of masticatory muscles affected by distraction osteogenesis of mandible].
OBJECTIVE: The purpose of this study was to study the masticatory muscles affected by distraction osteogenesis of the mandible. METHODS: The distraction osteogenesis (DO) was applied to distract the left mandible of 6 mongrel dogs that were divided into three experimental groups. After different distraction phase and consolidation phase, the masseter and the digastric muscle were taken out. The specimens were stained using hematoxylin/eosin and enzyme histochemistry. Afterwards, the specimens were observed with a light microscope to study the morphologic changes of the muscles. The contents of enzyme in the different groups were measured by VIDAS. RESULTS: The masseter showed consequently atrophy, but the digastric muscle showed a progress of histomorphologic reconstruction, including atrophy and hypertrophy. The changes of the contents of enzyme and histomorphology were identical in the masticatory muscles. CONCLUSION: The digastric muscle parallel to the vector of mandibular distraction adapts the distraction by the way of atrophy, regeneration and hypertrophy. And the contents of enzyme appear to decrease at the beginning, increase afterwards, and return to the normal level finally. But the masseter perpendicular to the vector of mandibular distraction shows consequent atrophy, and the contents of enzyme consequently decrease, which means the metabolism decrease.
Adenosine Triphosphatases↗
Histochemical studies of the masseter, the temporal and small zygomaticomandibular, and the temporomandibular masticatory muscles from aged male and female humans. Fiber types and myosin isoforms.
The purpose of this study was to investigate the histology of two small masticatory muscles from females and males of more than 70 years of age. By using immuno- and enzyme histochemistry the muscles were characterized by their fiber types and myosin heavy chain pattern. The observations were compared with similar studies of the masseter and temporalis muscles. Previously the two small muscles have been described based solely upon their gross anatomy. One muscle originates from the anterior, deep surface of the temporal fascia and inserts in the temporal tendon: the temporo-mandibular muscle (TM). The other muscle originates from the upper part of the temporal surface of the frontal process of the zygomatic bone and the adjacent part of the frontal bone and inserts in the temporal tendon: the zygomaticomandibular muscle (ZM). In the masseter, TM, and ZM, most of the autopsy samples contained an abundant number of fibers containing neonatal myosin heavy chains while in the temporal muscle specimens, such fibers were sparse and scattered. Electrophoresis followed by immuno-staining of Western blots supported the histochemical findings. There was no obvious correspondence between fiber typing based upon ATPase activity and the neonatal myosin heavy chain content in the muscle fibers. Neither did the fibers show accordance in their content of adult slow and fast myosin heavy chains and in their content of neonatal myosin heavy chain.
Aged↗
Heterogeneous distribution of myosin in human masticatory muscle fibres as shown by immunocytochemistry.
On the basis of enzymic properties, different fibre types can be distinguished in human skeletal muscle (type I fibres and type II fibres with subtypes) and there is a correlation between fibre types and the occurrence of slow and fast myosin. In human masticatory muscles, fibres with ATPase activity at pH 9.4, intermediate between that of type I (low activity) and type II (high activity), are frequent. On cryostat-sectioned material, highly specific antibodies against fast myosin, slow myosin and slow light chains were applied. The myosin composition of human masticatory muscles was very heterogeneous, in contrast to that in limb muscles, with various proportions of slow and fast myosins, heavy as well as light chains. Type I fibres contained slow myosin only and type II mainly fast myosin, ATPase IM and type IIC fibres contained a mixture of slow and fast myosins in variable amounts. The findings conform with physiological evidence of a continuum of contraction times for motor units in the human masticatory muscles and suggests that these muscles are highly adapted to the special and complicated functions of the stomatognathic system.
Adenosine Triphosphatases↗
Masticatory muscle myositis.
This report examines a case of masticatory muscle myositis in a dog. Inflammatory disorders can affect the muscles of mastication. Two types of inflammatory myopathies have been described. The histopathology and immunochemical features of this case suggest an immune mediated basis for this disorder. The diagnosis and treatment are described for this immune mediated inflammatory myositis.
Animals↗
[Otorhinolaryngologic aspects of chronic inflammations of the masticatory muscles].
Chronic and usually odontogenic inflammations of the masticatory muscles may be, due to anatomical conditions and inconspicuous inflammatory symptomatology, difficult to differentiate from tumours in this region. The differential diagnosis of both affections is based on the clinical course, sialography and CT examination which along with modern ATB treatment significantly modify hitherto used surgical therapy.
Adult↗
Mandibular rest position and electrical activity of the masticatory muscles.
STATEMENT OF PROBLEM: The determination of a correct vertical dimension of occlusion is a critical procedure in clinical dentistry. PURPOSE: The objectives of this study were to analyze the relation between mandibular rest position and electrical activity of masticatory muscles and to compare clinical and electromyographic rest position in subjects with different vertical facial morphologic features. MATERIAL AND METHODS: Clinical rest position and electromyographic rest position were investigated in 40 subjects. Electromyographic rest position ranged from 0.4 to 12.7 mm (average 7.7 +/- 2.7 mm). Clinical rest position ranged from 0.1 to 4.4 mm (average 1.4 +/- 1.1 mm). The average difference between electromyographic rest position and clinical rest position was 6.3 +/- 2.5 mm (range 0.3 to 10.3 mm). Sixteen subjects were selected according to the Frankfort mandibular plane angle and separated in two groups having a mandibular plane angle > or = 28 degrees. RESULTS: Rest position was significantly greater (p < 0.05) in the low-angle group (2 +/- 1.3 mm) than in the high angle group (0.8 +/- 0.8 mm). Electromyographic rest position did not differ between subjects with different facial morphologic features (8.1 +/- 1.7 mm low-angle group; 7.6 +/- 4.1 mm high angle group). By varying the vertical dimension millimeter by millimeter, masseter and anterior temporal electromyographic activity demonstrated a considerable decrease over an interocclusal distance of 3 to 4 mm. Further mandibular opening up to 18 mm corresponded to small changes in postural activity. CONCLUSION: This study suggests that a jaw posture with a few millimeters of interocclusal distance involves a great reduction of masticatory muscle activity.
Adult↗
Importance of coronoidotomy and masticatory muscle myotomy in surgical release of trismus caused by submucous fibrosis.
Thirty patients with trismus resulting from betel nut chewing-induced oral submucous fibrosis were treated with either fibrotic tissue release only (group I) or fibrotic tissue release in combination with masticatory muscle myotomy and coronoidotomy (group II). The latter procedures were only performed in patients whose intraoperative interincisal distance remained less than 35 mm immediately after submucous fibrous tissue release. There were eight and 22 patients in groups I and II, respectively. In group I patients, the average intraoperative interincisal distance improved from 19.5 mm to 42 mm. In group II patients, the average intraoperative interincisal distance improved from 13.5 mm to 27 mm after fibrotic tissue release and further improved to 40 mm after masticatory muscle myotomy and coronoidotomy. At an average follow-up of 22.1 months (range, 7 to 70 months), the group I and II patients had an average interincisal distance of 41.5 mm (range, 35 to 50 mm) and 32.9 mm (range, 20 to 42 mm), respectively. These results demonstrate the efficacy of submucous fibrotic tissue release in treating trismus resulting from betel nut chewing-induced submucous fibrosis and confirm the role of additional masticatory muscle and coronoidotomy in treating its severe forms.
Adult↗
Influence of the sagittal advancement of mandibulae on myofibrillar ATPase activity and myosin heavy chain content in the masticatory muscles of pigs.
Endurance muscle stress leads to polymorphic expression of myosin heavy chains (MyHC). Histochemical and electrophoretic analyses were performed on different masticatory muscles (masseter, temporal, geniohyoid and medial pterygoid) of 10 weeks old pigs after 28 days of chronic sagittal advancement of the mandibulae. The differentiation between fiber types was investigated histochemically with the myofibrillar ATPase (mATPase) method and by immunohistochemistry. Expression of different MyHC isoforms was also assessed by means of immunoblotting with monoclonal antibodies. The results of both methods were compared. Chronic sagittal advancement of the mandibulae led to an increase in the cross-sectional area of type I fibers and type I MyHC in the anterior part of the masseter, the distal part of the temporal and the medial pterygoid muscle. In the present study, clear differentiation between type I and type II muscle fibers in all histological analyses was possible. However, mATPase classification of subtypes of type II fibers may lead to misinterpretations. Additionally, a direct correlation between the type I MyHC concentration and the type I fibers was seen in enzyme histochemical and immunohistochemical staining. The defined cross section of fibers is important for the histological investigation in small muscles. The immunoblot method seems to be more sensitive and less subjective for measurement of muscle changes. It can be concluded that the immunoblot method used for measuring the MyHC content is a valid alternative for fiber typing in small muscles as it is less time-consuming and more sensitive than qualitative histochemistry.
Adenosine Triphosphatases↗
[Masticatory muscles. Part VIII. Reflexes in the masticatory system].
A reflex is an involuntary response on a specific nerve stimulus. Several types of receptors are present in the masticatory system which can be involved in reflex activity. A short mechanical tap on an incisor, for example, evokes a specific pattern of several so-called exteroceptive reflexes in the electromyographic (EMG) activity of jaw-closing muscles, which includes periods with decreased activity (inhibitory reflex) as well as increased activity (excitatory reflex). In this case, periodontal mechanoreceptors are detecting the stimulus. The second type of reflex that is dealt with is the jaw-jerk reflex as an example of a proprioceptive reflex. A transient increase in length of a jaw-closing muscle, detected by length sensors (muscle spindles), evokes an excitatory reflex in the EMG. Dependent on the motor task, the amplitude of both reflexes is modified. The various reflex mechanisms play an important role in normal physiological functions such as posture control and chewing.
Electromyography↗
Malocclusion and masticatory muscle activity: a comparison of four types of malocclusion.
Electromyographic activities of the temporalis and masseter muscles during mastication were measured in patients who visited this clinic for orthodontic treatment of progenia. The results obtained were compared with those previously obtained in patients with other types of malocclusion and relationships between types of malocclusion and activities of the masticatory muscles were examined. Several interesting results were obtained, including: 1) the muscle activities were significantly higher in patients with deep bite than in patients with any other types of malocclusion and 2) inefficient mastication patterns, evidenced by higher temporalis muscle activities on the balancing side than on the working side, were most frequently observed in patients with edge bite. These results indicate that the clinical evaluation of masticatory muscle activities may be useful in improving orthodontic treatment and in determining a proper retention period after the treatment. The results also suggest that orthodontic treatment should include some type of dynamic myofunctional therapy in addition to the correction of static structural abnormalities.
Child↗
Human masticatory muscle activity and jaw position under experimental stress.
The purpose of the present study was to determine whether stress induced a consistent pattern of increased electromyographic (EMG) activity in different masticatory muscles, and whether stress produced changes in jaw position. Thirty-five dental students at Taipei Medical College volunteered for this study. Mental arithmetic was used to create a stress condition and relaxation instruction was used to help relax the subjects. Subjects were asked to evaluate the stress they felt under each experimental condition with a visual analogue scale (VAS). Surface electrodes were used to monitor the EMG activities of the right masseter, right posterior temporalis and suprahyoid muscles. A kinesiograph was used to observe the jaw position. Data collected before mental arithmetic or relaxation monitored the baseline level. The VAS means were significantly increased during the stress condition and significantly decreased following relaxation, compared with the baseline. There was also a significant increase in EMG activity of all three muscles during mental arithmetic compared with baseline; different patterns of increased EMG activity were noticed in the three muscles under a continuous stress condition. Under stress, the incidence of tooth contact at intercuspal position was also increased.
Adult↗
Volume changes in human masticatory muscles between jaw closing and opening.
Most jaw muscles are complex, multipennate with multiple components. The morphologic heterogeneity of masticatory muscles reflects their functions. We hypothesized that the volume of masticatory muscles changes between jaw closing and opening, and that there is a difference in the volume change among the muscles. Magnetic resonance images of the entire head were obtained in ten normal young adult subjects before and after maximum jaw opening. The volume changes of the masseter, medial, and lateral pterygoid muscles were measured. Only slight changes were seen in the masseter and medial pterygoid muscles. The lateral pterygoid muscle, however, significantly decreased its volume during jaw opening. The results provide normative values of muscle volume in living subjects, and suggest that the volume changes differ among jaw muscles.
Adult↗
Effects of a functional appliance on masticatory muscles of young adults suffering from muscle-related temporomandibular disorders.
The aim of this study was to investigate the effects of an original orthodontic functional appliance [function generating bite for deep bite correction (FGB-D)] on masticatory muscle activity in subjects suffering from muscle-related temporomandibular disorders (TMD). Electromyographic (EMG) analysis was performed on 33 young adults (nine men, 24 women) to evaluate the contractile symmetry of the right and left masseter and anterior temporalis muscles. The subjects were divided into three groups: a muscle-related TMD group requiring orthodontic treatment for deep bite correction (three men, eight women) and treated with FGB-D; a muscle-related TMD group not requiring orthodontic treatment (three men, eight women) and treated with a Michigan occlusal splint; and a TMD-free group (three men, eight women) as a control group. Records were made by surface EMG of maximum voluntary teeth clenching, with and without the functional appliance or occlusal splint in place, before and after 12 months of therapy. A torque index was derived from the surface EMG recordings to estimate lateral displacement of the mandible. The results show that the FGB-D corrects the torque index and thus the lateral displacement of the mandible.
Adult↗