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PubMed1998

Myoelectric activity during unilateral chewing in healthy subjects: cycle duration and order of muscle activation.

STATEMENT OF PROBLEM: Craniomandibular disorders, unilateral mastication, and asymmetry of masticatory muscles appear to be related to each other. Thus, it is of interest to investigate masticatory muscle activity during unilateral mastication in healthy subjects. PURPOSE: This study monitored contractile activity of the right and left masticatory muscles during right- and left-side gum chewing. MATERIAL AND METHODS: Electromyographic techniques were used to determine chewing cycle duration and duration of contractile activity of the masticatory muscles (right and left masseter and anterior temporalis muscles) during unilateral chewing in 40 subjects without orofacial pain. The time-course of activation of the 4 muscles was also investigated. RESULTS: Electromyographic traces showed extensive interindividual variation. In both right- and left-side chewing tests, and regardless of whether the masseter or the temporalis muscles were considered, mean duration of the contraction phase did not differ significantly between the working and nonworking sides. The working side temporalis contracted first, whether alone or at the same time as the other muscles. CONCLUSIONS: In healthy subjects, no significant differences in masticatory muscle activity should be expected between either the right and left or the working and nonworking sides.

Adult↗
PubMed2005

Risk factors for headache, including TMD signs and symptoms, and their impact on quality of life. Results of the Study of Health in Pomerania (SHIP).

OBJECTIVE: The aim of this investigation was to evaluate the role of various signs and symptoms of temporomandibular disorders (TMD), among other potential risk factors, in developing frequent headache in a population-based sample of the cross-sectional epidemiologic Study of Health in Pomerania (SHIP). The impact of headache and of myogenous and arthrogenous signs of TMD on the quality of life of this sample was evaluated. METHOD AND MATERIALS: Medical history and dental and sociodemographic parameters of 4,255 subjects were checked for correlations with frequent headache using a multivariate logistic regression model. The quality of life of the headache sufferers was evaluated with a questionnaire on mental and physical health. RESULTS: Of the sample, 9% reported suffering from frequent headache. Significant values for the odds ratios for the whole sample were found for pain on palpation of the masticatory muscles; the anamnestic question on masticatory muscle pain; ear noises; lateral palpation pain of the temporomandibular joints (TMJ); several sleep disorders; psychosomatic complaints; and risk for women. Palpation pain of the muscles showed a dose/response effect. Subjects with a higher education level had a significantly reduced risk for developing frequent headache. Anamnestic questions for pain in the TMJ area, TMJ clicking, smoking, alcohol abuse, contraceptives, income, and chronic diseases did not correlate significantly with frequent headache. Subjects who reported frequent headache exhibited a significant reduction of physical and mental health scores. Pain upon muscle palpation showed significantly reduced scores on both scales for both genders. CONCLUSION: Within the limitations of this study, in addition to sensitive TMJs, mainly palpation-sensitive masticatory muscles showed a significant relation to the occurrence of frequent headache. Because of the number of tested covariates originally included in the model, this relation seems essential.

Adult↗
PubMed2003

Association between sleep bruxism, swallowing-related laryngeal movement, and sleep positions.

STUDY OBJECTIVE: To describe the relationships of sleep bruxism to swallowing and sleep positions. DESIGN: Controlled descriptive study. SETTING: Polysomnography and audio-video recordings were done in a hospital sleep laboratory. PARTICIPANTS: Nine patients with sleep bruxism and 7 normal subjects were matched for age and sex. INTERVENTIONS: n/a. MEASUREMENTS AND RESULTS: During sleep, patients with sleep bruxism showed a higher frequency of rhythmic masticatory muscle activity episodes (6.8 +/- 1.0 [SEM]/h) than did normals (0.5 +/- 0.1/h, p < 0.01). Swallowing-related laryngeal movements occurred more frequently in sleep of patients with sleep bruxism (6.8 +/- 0.8/h) than in normals (3.7 +/- 0.3/h, p < 0.01). In both groups, during sleep, close to 60% of rhythmic masticatory muscle activity episodes were associated with swallowing. In sleep bruxism patients, 68% of swallowing events occurred during rhythmic masticatory muscle activity episodes, while only 10% of swallowing events were associated with rhythmic masticatory muscle activity in normal subjects. Sleep bruxism patients and normals spent 95.5% and 87.3% of sleeping time in the supine and lateral decubitus positions, respectively. In both groups, up to 96% of rhythmic masticatory muscle activity and swallowing were observed in the supine and lateral decubitus position. In sleep bruxism patients, although sleeping time did not differ between the 2 sleeping body positions, 74% of rhythmic masticatory muscle activity and swallowing events were scored in the supine position compared to 23% in the lateral decubitus position. CONCLUSIONS: During sleep, rhythmic masticatory muscle activity is often associated with swallowing. In sleep bruxism patients, most of these oromotor events are observed in the supine position. The physiologic link between rhythmic masticatory muscle activity and swallowing and the clinical relevance of sleep position in sleep bruxism management need to be investigated.

Adult↗
PubMed2002

[Jaw muscle pain--its neurobiological basis].

The masticatory muscles show morphologic, histochemical, electrophysical, and functional features that differ from the other muscles of the body. At least two kinds of masticatory muscle pain should be distinguished: A local pain associated with peripheral mechanical overuse, and a pain associated with changes in the central nociceptive system. Biomechanical factors appear to be important for the first type of muscle pain. Since the typical reaction of a painful muscle consists of inhibition of its activity, traditional concepts that postulate the maintenance of the pain by chronic overuse of the whole muscle are not supported by the current literature. Instead, differential overuse of discrete intramuscular regions appear to provide a more plausible explanation. On the other hand, the possible relationships between functional and structural neuroplastic changes and the second form of chronic muscle pain (e.g., fibromyalgia) still remain speculative.

Facial Pain↗
PubMedDate not supplied

Correlation between various investigation methods of stomatognatic dysfunction.

The aim of this communication is to analyze the correlation between the stomatognathic and cervical muscular system testing, the analysis of tomography and the kinesiographic survey. The study has been done on 78 clinically healthy patients (24 males and 54 females) aged between 21 and 71, presenting various forms of stomatognathic system dysfunctions. The anamnesis comprised the Slavicek questionnaire as well. Within the complex clinical examination the classical clinical investigation of the masticatory muscles and the TMJ has been supplemented by masticatory muscles, cervical spine and shoulder girdle tests (AROM, PROM and resistive muscle tests). These tests have been correlated with the results of the 468 tomogram analyses and kinesiography surveys for test movements (780 traces) and for functional movements (156 records). The analysis of tomograms has shown the dimensional asymmetry of the articular elements and the asymmetry of the relationship between these elements in various position. These asymmetries are correlated to the alteration of the kinesiographic tracings. The variations of the articular gap and the P2 and P3 values are correlated in a very interesting way with the kinesiographic record but also with the symptoms of muscular dysfunction. The asymmetric condylar movements are reflected in the asymmetry of the muscular contractions, put into evidence through the insufficient response to AROM (78%), PROM (62%), resistive muscle tests (8%) for the masticatory muscles and cervical spine (22%). These results suggest the opportunity of extending the clinical examination at least in the cervical area.

Adult↗
PubMed2002

Electrophysiological analysis of rhythmic jaw movements in the freely moving mouse.

Although rhythmic jaw movement in feeding has been studied in mammals, such as rats, rabbits and monkeys, the cellular and molecular mechanisms underlying it are not well understood. Transgenic and gene-targeting technologies enable direct control of the genetic makeup of the mouse, and have led to the development of a new category of reagents that have the potential to elucidate the cellular and molecular mechanisms of neural networks. The present study attempts to characterize rhythmic jaw movements in the mouse and to demonstrate its relevance to rhythmic jaw movements found in higher mammals using newly developed jaw-tracking systems and electromyograms of the masticatory muscles. The masticatory sequence of the mouse during feeding was classified into two stages, incision and chewing. Small and rapid (8 Hz) open-close jaw movements were observed during incision, while large and slow (5 Hz) open-close jaw movements were observed during chewing. Integrated electromyograms of the masseteric and digastric muscles were larger during chewing than those observed during incision. Licking behavior was associated with regular (8 Hz), small open-close jaw movements with smaller masseteric activity than those observed during mastication. Grooming showed variable patterns of jaw movement and electromyograms depending on the grooming site. These results suggest that there are neuronal mechanisms producing different frequencies of rhythmic jaw movements in the mouse, and we conclude that the mouse is useful for understanding rhythmic jaw movements in higher mammals.

Animal Feed↗
PubMed1997

The role of bioelectronic instrumentation in the documentation and management of temporomandibular disorders.

Temporomandibular disorders (TMDs) can affect the form and function of the temporomandibular joint, masticatory muscles, and dental apparatus. Electronic measurement of mandibular movement and masticatory muscle function provides objective data that are defined by commonly accepted parameters in patients with TMDs; these data can then be used to design and monitor therapy and enhance treatment therapy. In this study, data on 3681 patients with TMD are presented, including electronic test data on 1182 treated patients with TMDs. Electronic jaw tracking was used to record mandibular movement and to compare the presenting and therapeutic dental occlusal positions. Electromyography was used to analyze the resting status of masticatory muscles and occlusal function at presentation and after therapeutic intervention. Transcutaneous electrical nerve stimulation therapy relaxed masticatory muscles and aided in the determination of a therapeutic occlusal position. The data show a positive correlation between the clinical symptoms of TMD and the presenting occlusion, accompanied by muscle activity. A strong positive correlation also appears to exist between a therapeutic change in the dental occlusion to a neuromuscularly healthy position with use of a precision orthotic appliance and the significant relief of symptoms within 1 month and at 3 months.

Adolescent↗
PubMed2005

[Computed tomographic examination of muscle volume, cross-section and density in patients with dysgnathia].

PURPOSE: The individual jaw position is determined by the masticatory muscle among other factors. Before surgical treatment of malocclusions, thorough evaluation of the muscles is required to estimate the relapse risk. MATERIALS AND METHODS: By means of computer tomography, lateral radiographs of the skull and denture models, the relationships between morphological parameters of the masticatory muscles and the jaw bone were analyzed. Furthermore, possible causes for the extent of the malocclusion are described. RESULTS: A patient group with deep overbite was found to have significantly higher muscle densities (measured in Hounsfield units [HU]) in the medial pterygoideus muscle (59.89 +/- 3.91 HU to 48.94 +/- 4.14 HU, p < 0.01), masseter muscle, and genioglossus muscle (p < 0.05) in comparison to open bite patients. Significant differences of the muscle cross-section were measured in the masseter muscle between patients with retroclined maxillary incisors and with an open bite (5.4 +/- 0.7 cm (2) to 3.8 +/- 0.4 cm (2), p < 0.05). CONCLUSION: The results show a correlation between different jaw positions and masticatory muscles. They also suggest that the function of each muscle may be different. Additional examinations of the muscle structures are required for verification of the influence of the masticatory muscles on facial morphology.

Bone Density↗
PubMed2003

The effect of occlusal alteration and masticatory imbalance on the cervical spine.

The characteristics of mandibular lateral displacement include lateral inclination of the occlusal plane and the differences between the right and left masticatory muscles. The aims of this investigation were to compare the mandibular stress distribution and displacement of the cervical spine using three-dimensional finite element models (3D FEM) to simulate masticatory movements and to clarify the association between morphological and functional characteristics and head posture. A symmetrical standard model was produced (model-A). Model-B had higher masticatory muscle strength on the left side, model-C had symmetrical masticatory muscle strength but the occlusal plane was inclined upwards towards the right and model-D had the occlusal plane inclined upwards towards the right with higher masticatory muscle strength on the left side. Model-A showed a completely symmetrical stress distribution pattern, while in model-B there was an uneven distribution in the mandible with higher stress on the left side. In addition, the stress distribution in the cervical spine was asymmetrical, showing displacement to the right. Model-C showed a similar mandibular tendency to model-B but the opposite tendency in the cervical spine. In model-D, the mandibular stress distribution was markedly asymmetrical, but almost symmetrical in the cervical spine with markedly decreased lateral displacement. These results suggest that lateral inclination of the occlusal plane and imbalance between the right and left masticatory muscles antagonistically act on displacement of the cervical spine, i.e. the morphological and functional characteristics in patients with mandibular lateral displacement may play a compensatory role in posture control.

Adaptation, Physiological↗
PubMed1981

[Morphometric analysis of differentiation of skeletal muscle fibers of the maxillofacial region during the process of embryonic development].

The skeletal muscle tissue of the lip, tongue, soft palate and masticatory muscles have been morphometrically studied in 70 human fetuses (4-10-month-old). In the muscles mentioned decrease in the nuclear volume and in the nuclear-cytoplasmic ratio is observed. Increase of the muscle fibres in the area of transversal sections is especially intensive during last three months. The labial and glossal fibres reach the greatest thickness. On the 6th month and further, there is an essential difference in number of myons with nuclei in the transversal section of the tongue and lips, as compared with the masticatory muscle and soft palate. In 9-10-month-old fetuses the index on saturation of the glossal and labial muscle fasciculi with capillaries is much greater than that of the soft palate and the masticatory muscle. There exists a statistically important and rather high positive correlation between the area of transversal sections of the muscle fibres, the number of nuclei in them and the density of capillaries in the muscle fasciculi. The relation between histochemical profile of the muscles under investigation and the number of capillaries in them is discussed.

Adenosine Triphosphatases↗
PubMed1990

An animal model for human masseter muscle: histochemical characterization of mouse, rat, rabbit, cat, dog, pig, and cow masseter muscle.

The masseter muscle of several animal species was investigated by use of a histochemical method for the demonstration of acid-stable and alkali-stable myosin adenosine triphosphatase (ATPase). The following subdivisions of fiber types were used: Type I fibers show weak ATPase activity at pH 9.4, type IM fibers react moderately, and type II fibers react strongly. Rat and mouse masseter muscles contained type II fibers only, as did some rabbit masseter muscles, whereas other rabbit masseter muscles possessed equal amounts of type I and II fibers. Cat and dog masseter muscles possessed both type II and I fibers, with type II predominating. Cow masseter muscle consisted mainly of type I fibers, although some cow masseter muscles contained a very small number of type II fibers. Pig masseter muscle had both type I, II, and IM fibers. One of the characteristics of human masseter muscle is type IM fibers, which are rarely seen in muscles other than the masticatory muscles. Therefore, pig masseter muscle might be a suitable animal model for experimental studies, such as an investigation of the distribution and diameter of fiber types in the masticatory muscles before and after orthognathic surgery.

Adenosine Triphosphatases↗
PubMed1990

Electromyographic findings in Class II division 2 and Class III malocclusions.

Electromyography of masticatory muscles has proved useful for the functional study of occlusal dysfunctions. We employed this technique to study the activity of masseter and temporal muscles of 6 subjects with Class II division 2 malocclusion and 7 subjects with Class III malocclusion. Significant differences of masticatory muscles activity during mastication and swallowing were observed between the two groups. We hypothesize that the change of the activity of masticatory muscles might influence the clinical presentation of malocclusion.

Adult↗
PubMed1990

Microtrauma to rat superficial masseter muscles following lengthening contractions.

Repetitive lengthening contractions have been predicted as a mechanism causing injury, pain, and delayed soreness in the hyperactive masticatory muscle. This mechanism was examined by the mechanical lengthening of the contracted superficial masseter (SM) muscle in anesthetized rats. Repetitive stimulation of the left SM to tetanic tension was followed by mechanical lengthening, which stressed contracted muscle. The contralateral muscle was passively lengthened repetitively. Contractile tension in response to a varying frequency of stimulation was measured in pre- and post-lengthened SM muscles. A selective loss of force at all frequencies up to 100 Hz occurred in the muscles subjected to lengthening contractions. Low-frequency fatigue did not occur in SM muscles passively lengthened. All animals recovered without loss of weight or dehydration. They were killed at 24 or 72 h post-lengthening. The SM muscles were collected, and no significant differences were found in mean weight, length, or cross-sectional area when the right and left SM muscles were compared at 24 or 72 h. Two observers independently examined histological secretions of SM muscles and graded the localized inflammatory sites on a scale of 1-4. A non-parametric statistical test was used so that the inflammatory scale for each muscle could be ranked. There were significantly more injured sites in SM muscles subjected to lengthening contractions, compared with the lengthened (but relaxed) SM muscles. The SM muscles of anesthetized rats were internally injured by repetitive lengthening contractions, and they exhibited low-frequency fatigue. These findings support the hypothesis that repetitive lengthening contractions in the masticatory muscle could be a mechanism for the pain and dysfunction of masticatory muscles in humans with certain parafunctional habits.

Animals↗
PubMed1975

Localization of masticatory motoneurons in the cat and rat by means of retrograde axonal transport of horseradish peroxidase.

Topographical localization of monotoneurons supplying the masticatory muscles was investigated in the cat and rat, utilizing retrograde axonal transport of horseradish peroxidase. Following injection of horseradish peroxidase in each masticatory muscle, motoneurons labelled with peroxidase were seen to be aggregated into a cluster within the motor nucleus of the trigeminal nerve. Such clusters of peroxidase-motoneurons innervating each masticatory muscle were demarcated more sharply in kittens than in adult animals. The pattern of the nuclear representation of the masticatory muscles was found to be essentially the same in the cat and rat; it could be summarized as follows: The motor nucleus of the trigeminal nerve could be divided cytoarchitectonically into the dorsolateral and ventromedial divisions; the former was seen in almost the whole rostrocaudal extent of the nucleus, while the latter was localized at the levels of caudal two thirds of the nucleus. In the dorsolateral division, the temporal muscle was represented dorsally and dorsomedially, the masseter muscle ventrolaterally, and the pterygoid muscles ventromedially. In the ventromedial division, the anterior digastric muscle was represented dorsomedially, and the mylohyoid muscle ventrolaterally. It was also confirmed that the motoneurons supplying the posterior digastric muscle were localized in the accessory facial nucleus.

Animals↗
PubMed1993

Alterations of muscle activities and jaw movements after blocking individual jaw-closing muscles in the miniature pig.

Although the inactivation or removal of motoneurones and muscles are known to affect development and growth of the craniofacial skeleton and masticatory muscles, the effect of these on functional activity patterns is not clear. The goal of this study was to evaluate the immediate responses of masticatory muscle activities to temporary nerve blocks of individual jaw-closing muscles. Nineteen experiments were made with four miniature pigs (Sus scrofa). Electromyograms of the masticatory muscles and jaw movements were recorded during natural chewing. Then, the function of individual jaw-closing muscles was removed unilaterally by local anaesthesia, and the recording repeated. The results showed a general increase in the activities of the other jaw-closing muscles, particularly those that were synergistic with the blocked muscle in producing lateral movements. Furthermore, the lateral pterygoid showed stronger activity, and accordingly the lateral movement was increased. Digastric muscle activity and the magnitude of jaw opening also tended to increase. Thus, the response to loss of a muscle is a strong, immediate compensation by synergists.

Animals↗
PubMed1975

[Types of fibers in skeletal muscles of mammals: histochemical and ultrastructural characteristics in relation to their contractile properties].

A tentative correlation of histochemical and ultrastructural features with physiological properties in mammalian skeletal muscle fibers is presented. In particular, the characteristic metabolic and structural profile of fast-twitch red fibers is described and evidence is presented for the presence of such fibers in limb muscles and masticatory muscles of the rat. The existence of interspecies and even intraspecies variation in the histochemical correlates of the different fiber categories is emphasized and the significance of intermediate fiber types is discussed.

Animals↗