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PubMed1986

Correlation between histochemistry and muscle activity of jaw muscles in cats.

Studies on limb muscles of mammals indicate that the pattern of electromyographic (EMG) activity reflects the histochemical profile of the muscle. This relationship suggests that EMG activity may permit a prediction of certain morphological characteristics of the muscle being studied. In this study numerical descriptors of EMG activity of the masticatory muscles of cats are correlated with the distribution of fiber types, as well as with fiber and fascicle areas, to test the extent to which EMG can be used to predict regional morphology. The results show that the level of EMG activity and its duration have a significant positive correlation with the percentage of slow- and fast-twitch fatigue-resistant fibers and a significant negative correlation with the percentage of fast-twitch fatigable fibers and the ratio of fast-twitch fatigable to fast-twitch fatigue-resistant, plus slow fibers. No correlation was found between activity and fiber cross-sectional area; the descriptors showing significant correlation vary with the hardness of the food. Thus the level of EMG activity and its duration seemingly do provide an indicator of the relative difference in fiber distribution among muscles in a species.

Adenosine Triphosphatases↗
PubMed1989

Proportionality of mean voltage of masseter muscle to maximum bite force applied for diagnosing temporomandibular joint disturbance syndrome.

Maximum bite force in the region of the right first maxillary molar and the corresponding mean voltage of the right masseter muscle of 29 patients suffering from temporomandibular joint dysfunction and 27 healthy controls were measured. In contrast with the controls, the maximum bite force of the patients was smaller (p less than 0.01), the mean voltage was nearly equal (p greater than 0.05), and the proportionality of the mean voltage to the maximum bite force of the patients was greater (p less than 0.01). These results tend to indicate that the masticatory muscles of patients with temporomandibular joint dysfunction are in a state of hyperactivity and tension. The proportionality method suggested in this article is more convenient and easier to apply than previously proposed methods that measure the slope of voltage/tension curves. It may, therefore, have clinical value in the diagnosis of patients with temporomandibular joint disorders.

Adolescent↗
PubMed1996

Facial structure and functional findings in patients with progressive muscular dystrophy (Duchenne).

The investigation of 15 patients who have a progressive muscular dystrophy of the Duchenne type (PMD) shows the affection of various groups of muscles of the stomatognathic system, studied by means of electromyography and mechanical force measurements. We observed the following deviations in patients with PMD; transversal overdevelopment and sagittal shortening of the dental arch; reduction of overbite and overjet; sagittal underdevelopment of the cranial, maxillary and mandibular base; retrusion of incisors; concave profile; increase in bizygomatic width; and a difference in time between the attack on the musculi orbicularis oris and that on masticatory muscles. In our study, the activity of the jaw muscles diminished 2 years earlier compared with the perioral muscles. This, and also the enlargement of the hypotonic tongue, causes a transversal expansion of skull and dental arches. This expansion was strongly pronounced in the lower jaw; we invariably observed a posterior crossbite. In contrast to the transversal overdevelopment, we observed a sagittal underdevelopment of skeletal and dental parameters, as well as a retrusion of the incisors. The results of surface electromyography showed the affection of the masseter muscle in patients who had PMD. By means of the Fast-Fourier transformation, we observed a displacement of the median frequency as compared with the lower frequency range.

Adolescent↗
PubMed1990

Craniofacial alterations following electrolytic lesions of the trigeminal motor nucleus in actively growing rats.

The objective of this study was to define further the role of the trigeminal motor nucleus (TMNu) in the postnatal ontogeny of the mammalian craniofacial skeleton. To that end, 42 male Sprague-Dawley rats underwent stereotaxic surgery at 40 days of age; 21 received small electrolytic lesions to their left-side TMNu (lesioned group) while 21 had TMNu stimulation with no actual electrolytic lesion produced (sham group). Seven rats from each group were killed at 28, 56, and 84 days postoperative to analyze trigeminal motoneuron (TMNe) count, masticatory muscle weight, and osteological growth vector data. At all three time periods, lesioned animals showed significant differences 1) between the surgery and nonsurgery sides, and 2) from sham animals. However, sham animals also demonstrated significant between-side differences for medial pterygoid muscle weight (56 days), mandibular height (28 and 56 days), and mandibular length data (84 days); these data suggested that even relatively slight damage to TMNe can create morphological changes within the craniofacial complex. Snout deviation in a lesioned rat towards the opposite side from all other lesioned animals was correlated with unique damage to its pontine reticular formation; this suggested that the observed morphological alterations of the craniofacial complex may have been due not only to TMNu damage, but also to changed expressions of the masticatory central pattern generator (CPG). Morphological alterations of the craniofacial skeleton resulting from lesions to the TMNu were likely due to changed neuromuscular activity patterns of the masticatory muscles and their biomechanical effects upon bone.

Animals↗
PubMed2000

[Impaired occlusion is the main etiological factor in the occurrence of temporomandibular joint dysfunction].

A homogeneous group of 104 subjects aged 21-34 years was examined. Forty-nine (47%) subjects (study group) presented with symptoms of abnormalities of the masticatory muscles and temporomandibular joint, 58 subjects (53%) without such symptoms were controls. Clinical examination was carried out with evaluation of occlusion, Angle's [correction of Engle's] class, and analysis of dental contacts in the oral cavity in different types of occlusion. Disorders of occlusion were detected in 31% of controls and in 73% patients in the study group. Disorders of occlusion correlated with the number of symptoms of temporomandibular joint dysfunction. The detected super-contacts of teeth are the main etiological factors leading first to discoordination of the masticatory muscles and then to functional disorders of the temporomandibular joint.

Adult↗
PubMed2006

Orofacial muscle pain: new advances in concept and therapy.

This manuscript focuses on chronic myogenous pains affecting the masticatory muscles. The differentiation of myogenous masticatory pain into subcategories is proposed by separating myogenous pains according to their location and anatomic extent. Focal myalgia, regional myalgia, myofascial pain, and fibromyalgia are classified based on specific historical and clinical examination criteria. The probable mechanisms underlying chronic myogenous pains and trigger points phenomena are discussed. Treatment options of the myogenous masticatory pain conditions including physical medicine modalities, as well as several types of pharmacologic agents, are presented.

Chronic Disease↗
PubMedDate not supplied

Traumatic stressors and post-traumatic stress disorder symptoms in headache patients.

OBJECTIVE: The aim of this study was to assess the prevalence of significant traumatic stressors and post-traumatic stress disorder (PTSD) symptoms in a headache population. BACKGROUND: Several recent publications have emphasized the relationship between life stressors and/or daily hassles and recurrent headaches. However, little is known about the prevalence and impact of major traumatic stressors in patients with recurrent headaches. METHODS: Eighty patients with either migraine or tension-type headache completed a PTSD checklist. Data were compared with those from patients with chronic masticatory muscle pain of similar intensity and duration. RESULTS: Almost 64% of the headache patients reported one or more major traumatic stressors. This percentage was not significantly different from that of the comparison group, and fell within the broad range reported for exposure to traumatic stressors in epidemiologic studies with nonpatient populations. One out of 6 patients in the total headache sample, and 1 out of 4 of those reporting a traumatic stressor, reported symptoms suggestive of current PTSD. The prevalence of current PTSD-like symptomatology reported by the headache patients was comparable to that of the comparison group of the present study, but higher than that reported for the general population in the available literature printed in English. Traumatic stressors most often reported were not related to direct physical trauma, but rather associated with loss or serious illness of a loved one. CONCLUSION: Exposure to traumatic events in patients with a primary diagnosis of recurrent headaches is similar to that reported for chronic masticatory muscle pain patients or nonpatient populations. However, symptoms consistent with a diagnosis of current PTSD appear to be more frequent in patients with recurrent headaches than reported in the scientific literature printed in English for nonpatient populations. Screening for PTSD symptomatology is recommended as part of the routine clinical evaluation of headache.

Adult↗
PubMed1990

Enzyme-histochemical and morphological characteristics of muscle fibre types in the human buccinator and orbicularis oris.

Human masticatory muscles, originating from the first branchial arch and innervated by the trigeminal nerve, have a fibre composition distinct from that of limb and trunk muscles. The zygomatic muscles, originating from the second branchial arch and innervated by the facial nerve, differ in fibre composition from either the masticatory or the limb and trunk muscles. To elucidate further the structural basis for function, and the influence of embryological origin and innervation on oro-facial muscles, the buccinator and orbicularis oris muscles, which originate from the second branchial arch and are innervated by the facial nerve, were investigated. Like the masticatory and zygomatic muscles, they have a large representation in the cerebral cortex. Both muscles were composed of type I, type IIA and a few type IIC fibres of about equal diameter. However, the type I fibres had a different myofibrillar ATPase reaction from those in masticatory, zygomatic, limb and trunk muscles; this was a moderate to strong staining at pH 9.4, indicating a special isomyosin composition. Whereas the buccinator was composed of 53% type I fibres, the orbicularis oris had a 71% predominance of type II fibres. In both muscles, the mean fibre diameter and its marked intramuscular variability were similar to earlier findings in the zygomatic muscles. No muscle spindles were found. The large number of type I fibres in the buccinator implies a capacity for endurance during continuous work at relatively low levels of force. The predominance of type II fibres in the orbicularis oris indicates that it is built up of fast-twitch motor units, related to properties such as rapid acceleration and high speed during intermittent oro-facial movements. The similarities and differences in fibre-type composition between the facial, masticatory and limb muscles imply that specific functional demands are of greater importance for muscle differentiation than embryological origin and nerve supply.

Acetylcholinesterase↗
PubMed1983

Size and shape of the mandibular condyle in primates.

The relationships between the size of the articular surface of the mandibular condyle and masticatory muscle size, tooth size, diet, and biomechanical variables associated with mastication were studied by taking 12 measurements on skulls of 253 adult female anthropoid primates, including three to ten specimens from each of 32 species. In regressions of condylar length, width, or area against body weight, logarithmic transformations substantially improve the fit of the equations compared with untransformed data. There is a strong relationship between condylar measurements and body weight, with all correlations being .94 or higher. The slopes of the allometric regressions of length, width, and area of the condylar head indicate slight positive allometry with body size. Folivorous primates have smaller condyles than frugivorous primates, and colobines have smaller condyles than cebids, cercopithecines, or hominoids. When colobines are eliminated, the differences between frugivores and folivores are not significant. However, the two species with the relatively largest condyles are Pongo pygmaeus and Cercocebus torquatus, suggesting that there may be a relationship between unusually large condylar dimensions and the ability to crack hard nuts between the teeth. Cranial features having strong positive correlations with condylar dimensions include facial prognathism, maxillary incisor size, maxillary postcanine area, mandibular ramus breadth, and temporal fossa area. These data are interpreted as indicating that relatively large condyles are associated with relatively large masticatory muscles, relatively inefficient mandibular biomechanics, and a large dentition. These relationships support the growing evidence that the temporomandibular joint is a stress-bearing joint in normal function.

Animals↗
PubMed1994

Functional influence on sutural growth. A morphometric study in the anterior facial skeleton of the growing rat.

The aim of this study was to quantify the sutural response in the various parts of the rat's upper frontal viscerocranium and study the possible effects caused by reduced masticatory muscle function. Twenty growing male albino rats were randomly divided into two equal groups: one group (Hard Diet group) received the ordinary diet in a hard pellets form, while the other (Soft Diet group) a soft diet. The experimental period started just before the rats' pubertal growth spurt (28 days old) and its duration was 28 days. After death, the heads of the animals were taken for preparation of undecalcified frontal sections, 100 microns thick. Contact microradiographs of six representative homologous sections, for every animal in both groups, were prepared. The mean width, length, height, and interdigitation ratio of the internasal, naso-premaxillary, and interpremaxillary sutures, as well as the orientation of the bony surfaces of the naso-premaxillary suture were quantified on the contact microradiographs using the IBAS automatic image analysis system. The width of the sutural space was found to be significantly greater in the Hard Diet group than in the Soft Diet group in all the sutures studied (P < 0.01). No differences in the interdigitation of the sutures were found between the two groups, except in the internasal suture in the middle part of the snout, where the Hard Diet group exhibited increased interdigitations. The bony surfaces of the naso-premaxillary suture were significantly more parallelly-orientated in the animals with reduced masticatory muscle function (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1989

Innervation pattern in jaw muscles of various mammalian chewing types.

The intramuscular nerve branches of the masticatory muscles were investigated in different mammalian species such as Canis familiaris, Capreolus capreolus, Capra hircus africans, Bos primigenius forma taurus, Myocastor coypus MOLINA 1782, Sus scrofa domestica, Pan troglodytes, Homo sapiens. The ramifications of the nerves form a specific pattern that is adapted to the specialised muscle structures in all mammalian chewing type. The innervation pattern is fully consistent with the infrastructures of the muscles which are already fixed at birth. Differences between the ramification pattern in comparable muscles in different chewing types are only minor, not fundamental.

Animals↗
PubMed1990

[The effect of the local anesthesia to the posterior ramus of the mandible in patients with temporomandibular joint problems].

Some clinicians in North America use anesthetic injections to differentiate the symptoms such as pain and stiffness in the facial area and neck in patients with TMJ problems. However, the effects and area which is influenced have not been studied. The purpose of this study was to study procedures and changes following administration of local anesthesia to the posterior ramus of the mandible. Twenty four patients with TMJ problems were used in this study. 0.5ml of 2% Lidocaine (epirenamine included) was injected into the most painful site upon palpation. The pain upon palpation test (following Krogh-Poulsen's method) was compared before and after 50 minutes. Results of this experiment were: 1) decrease of pain upon palpation was found not only in the site. In many cases subjective pain in the head and neck area was also reduced. 2) A significant reduction was found in the pain upon palpation test in the neck area. A highly significant reduction was seen in the Sterunoclydmastoid muscle only in the injected side. In the masticatory muscles. Also, reduction of pain upon palpation was seen in both lateral, medial pterygoid and digastric muscles in the injected side. 3) Contra side lateral pterygoid muscle and trapezius muscle also registered decreased pain upon palpation. 4) The mean values for the injected site were 5.7mm (S.D. 5.9) below the earlobe and the mean depth from the skin surface to the bony surface were 16.6 mm (S.D. 2.7mm). 5) The peak of the subjective effect were seen in one group in 20 minute later injection (early type) and in the 2nd group the peak were seen after 40 minutes (slowly type). 6) We did not experienced any paralysis of the facial nerve in this study.

Diagnosis, Differential↗
PubMed1981

Parameters of open-close-clench cycles in children.

The results of this study indicate that the latency and silent periods of OCC cycles do not vary among groups representing distinct dentitional stages. The mean latency period durations obtained from the OCC cycles of the subjects in this study ranged from 16.6 to 19.5 msec and demonstrated the smallest SD of all parameters measured. The mean silent period durations ranged from 11.6 to 15.4 msec. Since the neurophysiologic responses do not vary, the reflex elicited by tooth contact in OCC cycles is not based on tooth form or quantity. The results further indicate that, with the exception of the latency period of the anterior temporal muscles, the activities of the right and left components of the masticatory muscles examined are significantly correlated to each other during OCC cycles. This suggests a role for the anterior temporal muscle in bringing about adjustments of the masticatory system in the intercuspal position.

Adolescent↗
PubMed2005

Preliminary rapport on head posture and muscle activity in subjects with class I and II.

Forward head posture may cause alterations in the stomatognathic system, including changes in the muscle activity of the masticatory muscles and dental occlusion alterations. Considering the need for further understanding of the relationship between the stomatognathic system and the cervical region, the purpose of this study was to analyse the head posture and the electromyographic (EMG) activity of the anterior portion of temporal and masseter muscles bilaterally among bruxist's subjects with different dental occlusion classifications using the Angle method. The study consisted of 20 female volunteers, between the ages of 17 and 27 years. They were separated into two groups (class I and class II occlusions) according to a dentist-performed evaluation. An assessment of forward head posture was conducted using a photographic technique (angular calculus) combined with a clinical analysis. In the EMG analyses, active differential surface electrodes (Ag) were utilized and were placed bilaterally on the belly of masseter and temporal muscles, perpendicular to the muscles fibres. The EMG signal recorded during bilateral isotonic mastication, was presented using the Root Mean Square and was processed by Matlab software. The results indicated that the EMG responses of temporal and masseter muscles tend to be modified by occlusion alteration class II. Subjects with class II occlusion tended to present more occurrence of forward head posture with alterations in the muscle activity pattern between masseter and temporal muscles.

Adolescent↗
PubMed1986

Focal dystonia of the jaw and the differential diagnosis of unilateral jaw and masticatory spasm.

The clinical features, differential diagnosis and treatment of unilateral spasms of the jaw and masticatory muscles are discussed and illustrated by eight cases of unilateral jaw spasms of various aetiologies. These include focal dystonia of the jaw, hemimasticatory spasm with and without facial hemiatrophy, paroxysmal events in multiple sclerosis and tetany. Attention is particularly drawn to four cases of unilateral dystonia of the jaw which has not been described before.

Adult↗
PubMed1996

[A clinical and physiological evaluation of masticatory center in shortened arch].

The aim of this study was to evaluate the influence of occlusal deficit by loss of bilateral posterior molars in masticatory habituation and how to improve by RPD, investigating the location center of occlusal load (by Prescale Fuji Film Co.) and in its amount, in connection with masticatory muscle activities by analyzing EMG. EMG measurements of masticatory masculature at maximal clenching with pressure indicator, were induced at intercuspal position, confirming by MKG. As controls, seven complete dentate adults were referred, the five mandibular and maxillary bilateral molar-edentate cases each of five were investigated. The results were as follows: i) The location of the center of the occlusal load in dentate mouth was about the midline of the maxillar first molar. ii) In the loss of bilateral molars, the center of the occlusal load was in the first premolar area. iii) By prosthodontic treatments the center of the occlusal load was changed to the second premolar area. iv) These results indicated that the prosthodontic treatment was estimated in physiological imperfection of recovery as yet dentate mouth.

Aged↗
PubMedDate not supplied

Myosin heavy chain 2B isoform is expressed in specialized eye muscles but not in trunk and limb muscles of cattle.

Myosin heavy chain isoforms (MHC) of adult skeletal muscles are codified by four genes named: slow, or type 1, and fast types 2A, 2X and 2B. The slow, 2A and 2X isoforms have been found expressed in all mammalian species studied so far whereas there is a large inter-species variability in the expression of MHC-2B. In this study histochemistry (m-ATPase), immunohistochemistry with the use of specific monoclonal antibodies and RT-PCR were combined together to assess whether the MHC-2B gene is expressed in bovine muscles. ATPase staining and RT-PCR experiments showed that three MHC isoforms (1, 2A, 2X) were expressed in trunk and limb muscles. Slow or type 1 expression was confirmed using a specific antibody (BA-F8) whereas the detection of fast MHC isoforms were validate by means of BF-35 antibody although not by the SC-71 antibody. MHC-2B was absent in limb and trunk muscles, but was present in specialized eye muscles (rectus lateralis and retractor bulbi) as consistently showed by RT-PCR and reactivity with a specific antibody (BF-F3). Interestingly, a cardiac isoform, MHC-a-cardiac was found to be expressed not only in extraocular muscles but also in masticatory muscles as masseter.

Animals↗