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PubMed1987

Innervation of facial skin but not masticatory muscles or the tongue by trigeminal primary afferents containing somatostatin in the rat.

Using retrograde transport of a fluorescent dye, True blue, the peripheral tissues innervated by trigeminal ganglion neurones containing somatostatin have been investigated. Of ganglion neurones retrogradely labelled from injections of dye into the facial skin, 3.45% were found to be immunoreactive for somatostatin. In contrast, none of the neurones labelled from injections of dye into the tongue or masseter muscle were found to contain this peptide. This demonstration of a restricted distribution of somatostatin-containing primary afferents raises the possibility that somatostatin may be involved in functions which are specific to skin and not to the other tissues examined.

Animals↗
PubMed1982

[Venous networks and plexuses in the masticatory muscles].

Studied were the structure and localization of the venous plexuses in the chewing muscles of a total of twenty newborn and growing lambs and sheep (aged up to 8 years) of both sexes through preparation, corrosion, and measuring. It was found that the venous plexuses were localized within the muscles and had definite boundaries. They were shown to be connected with the muscles and the periosteum of the neighbouring bones, and lay in the way of the emissary and bone veins and the veins that came from the muscles. The venous plexuses formed loops of a varying size and form, and the veins had two layer valvulae. In newborn lambs the plexuses were at birth well structured and localized. The venous vessels were found to be in close contact with the branching of the regional arteries. Numerical data are given concerning the size of the plexuses observed. It was assumed that these structures, beside their collecting the blood from the muscles, the rostral portion of the maxillary sinus, the alveolae of the last two molars of the maxilla, the brain and the venous sinuses in dura mater, are also of hemodynamic importance with regard to the correct distribution of the blood and its downward course (from the head to the neck).

Animals↗
PubMed1987

[Functional morphology of the maxillo-mandibular system in the mini-Lewe minipig. 4. Functional analysis of the masticatory muscles at various ages].

The percentage of dry weight distribution of the jaw muscles is described, and muscle growth is calculated by means of second degree homogeneous linear differential equations with constant coefficients. The components of the chewing muscles are calculated from the parallelogram of forces on the basis of their dry weights. Changes in the shape of the skull during postnatal development leads to an increase in the adductive components and a reduction of the protractive components. Changes in the reaction, medial tensile, lateral tensile and depressive components are minor.

Aging↗
PubMed1988

[Sex dimorphism of quantitative parameters of the masticatory muscles and skull of the rabbit].

The dry weight of the muscles of mastication and the size of the skull in the rabbit were studied from the 45th to the 225th d of life. Sexual dimorphism in the dry weight of the muscles of mastication appeared after the 100th d, the weight being higher in the case of the males. Sexual dimorphism of the skull affected only the zygomatic arch, the dimensions of the zygomatic arch in the male being greater than in the female from the 120th d on. The 2 differences are considered in relation to each other.

Animals↗
PubMed1994

Sensibility threshold in patients with masticatory muscle pain.

Sensibility and pain thresholds were measured in 27 patients with myofascial pain and craniomandibular disorders and in 19 controls. A monopolar electric stimulator with increasing direct current values was used to record pain and sensibility thresholds in the lower incisors. Patients with myofascial pain had a tendency towards lower sensibility and lower pain thresholds than the controls, although the differences were not statistically significant.

Adult↗
PubMed1988

Histochemical analysis of masticatory muscle in the growing rat after prolonged alteration in the consistency of the diet.

Changes in muscle function induce alteration in craniofacial bone growth. To study morphological changes after alteration of masticatory function, NADH-TR reductase and myofibrillar Ca2+-activated ATPase were assessed histochemically, after alkaline and acid pre-incubation, in sections from the anterior deep masseter and the anterior digastric muscles. Type IIA, IIB and transitional fibres of the anterior deep masseter but not of the digastric muscle were smaller in a soft-diet group than in a normal-diet group. There was a small percentage of type IIA fibres and a large percentage of type IIB fibres in the anterior deep masseter in the soft-diet than in the normal-diet group. The elevator muscles do not encounter the same functional demands on a soft as on a normal diet, and this causes different biting and chewing loads, which may in turn induce skeletal changes.

Animals↗
PubMedDate not supplied

The influence of dental status on masticatory muscle activity in elderly patients.

PURPOSE: The objective of this study was to determine whether elevator and depressor muscle activity during 5 minutes of mastication is affected by the presence of a prosthetic appliance in elderly patients. MATERIALS AND METHODS: Thirty edentulous subjects (EG) and 30 age-matched dentate subjects (DG) were studied. Surface electromyographic (EMG) recordings were obtained from the anterior temporal muscle, masseter muscle, and the submandibular group in the region of the anterior belly of the digastric muscle on the left and right sides. Muscle activity was recorded during maximal voluntary contraction (MVC) in the intercuspal position, maximal opening (Omax), and during 5 minutes of mastication. Elevator muscle activity during mastication was expressed as a percentage of maximal muscle activity in the intercuspal position (%MVC), and depressor muscle activity was expressed as a percentage of maximal opening (%Omax). The effect of 3 factors was investigated using a mixed analysis of variance design: the factor of muscle, with 6 muscles involved; the factor of time (5 minutes of mastication); and the factor of dental status, where some participants had their own natural dentition and others had complete dentures. RESULTS: The results revealed significant effects for the factors "muscle" and e" (P < .001 for the factor "muscle"; P < .001 for the factor "time"). The time by group interaction was significant (P = .046). In the EG, muscle activity gradually decreased during the 5-minute interval of mastication, while in the DG it decreased more rapidly from the first to the third minute and then increased until the fifth minute. There was also a significant effect regarding the presence of natural teeth or complete dentures (P < .034). Complete denture wearers had higher muscle activity relative to %MVC or %Omax than dentate subjects. CONCLUSIONS: Muscle activity during 5 minutes of mastication depended greatly on the presence of the prosthetic appliance, since edentulous subjects had to use higher potentials of muscle activity (%MVC or %Omax) than age-matched dentate subjects, and were unable to increase activity at the end of mastication. The difference in chewing patterns and activity between complete denture wearers and dentate subjects should be explained to patients prior to prosthetic treatment to help them adjust their expectations.

Aged↗
PubMed2005

Neural mechanisms of temporomandibular joint and masticatory muscle pain: a possible role for peripheral glutamate receptor mechanisms.

The purpose of the present review is to correlate recent knowledge of the role of peripheral ionotropic glutamate receptors in the temporomandibular joint and muscle pain from animal and human experimental pain models with findings in patients. Chronic pain is common, and many people suffer from chronic pain conditions involving deep craniofacial tissues such as temporomandibular disorders or fibromyalgia. Animal and human studies have indicated that the activation of peripheral ionotropic glutamate receptors in deep craniofacial tissues may contribute to muscle and temporomandibular joint pain and that sex differences in the activation of glutamate receptors may be involved in the female predominance in temporomandibular disorders and fibromyalgia. A peripheral mechanism involving autocrine and/or paracrine regulation of nociceptive neuronal excitability via injury or inflammation-induced release of glutamate into peripheral tissues that may contribute to the development of craniofacial pain is proposed.

Animals↗
PubMedDate not supplied

[The correlations between the electromyographic display and the aspects involved with masticatory muscle contraction and phosphorus-calcium metabolism].

The neuromuscular activity at the level of the stomatognathic system has a specific complexity, due to the multiple systemic functions, realizing the statistical and dynamical mandibular positions and the integration of the stomatognathic system at the level of the human body. Knowing that the neuroendocrine system represents an important factor for the over-systemic coordination of the stomatognathic muscular activity, we want to establish the implication and the neuroendocrine correlation in the stomatognathic muscular dysfunctions determined by some endocrine diseases.

Calcium↗
PubMed1989

Non-specific esterases and esterproteases in masticatory muscles from the muscular dystrophic mouse.

With the aid of histochemical and electrophoretic techniques activities for esterase and esterprotease were investigated in the digastric and masseter muscles from normal and dystrophic mice. The substrates used were alpha-naphthyl acetate and N-acetyl-L-alanine alpha-naphthyl ester. According to the microscopic observations of the dystrophic muscles the histopathological changes in the masseter muscle were much more pronounced than in the digastric muscle. The connective tissue surrounding the myofibers of the dystrophic masseter contained a large number of cells with pronounced enzyme activity. Among them were mast cells that were strongly stained for esterprotease. The connective tissue of the dystrophic digastricus was much less infiltrated with cellular elements reacting for esterprotease. In zymograms the normal digastricus, the dystrophic masseter and the dystrophic digastricus showed a strong activity for certain isoenzymes that were absent or weakly expressed in the normal masseter.

Animals↗
PubMed2003

[Myoarthropathy of the temporomandibular joint and masticatory muscles. Pain therapy management and relaxation instead of aggressive surgery].

Temporomandibular pain is often characterized by a mismatch between symptoms and findings. The dentist's well-established therapeutic strategies for the management of acute pain are therefore frequently not effective in patients with painful temporomandibular disorders (TMD). Instead, dentists should apply the tried and tested principles that are applied in general medicine to the diagnosis and treatment of musculoskeletal pain (e.g. arthritic pain or fibromyalgia). When consulted by patients with rheumatic diseases, physicians should routinely enquire whether they also experience temporomandibular pain.

Analgesics↗
PubMed2002

Occlusal conditions just after the relief of temporomandibular joint and masticatory muscle pain.

When the signs and symptoms of temporomandibular joint disorders (TMD) are present, it is possible that occlusal conditions and mandibular movements are changed. Accordingly, the presence of occlusal interferences may be misjudged. It is therefore reasonable to consider that occlusal conditions should be examined just after the relief of symptoms. The comparison of occlusal conditions in 52 temparomandibular joint (TMJ) pain patients and 27 muscle pain patients with that in 60 asymptomatic controls was made. Occlusal examination in the patients was administered just after the relief of pain by bite plane therapy alone. The only occlusal factor which was associated with pain symptoms was no canine contact on the working side on laterotrusion. It is suggested therefore that further studies as regards this type of interference should be performed.

Adolescent↗
PubMed1978

Inverse activity of masticatory muscles with and without trismus: a brainstem syndrome.

Clinical and EMG findings in 10 cases of intrinsic brainstem lesions are reported with paradoxical activity of jaw closing muscles during jaw opening, with and without trismus. In five cases with trigeminal anaesthesia, the inverse activity of jaw closers is interpreted as a manifestation of disturbance in the central programming of mastication in the motor trigeminal area of the brainstem. Stretch reflex mechanisms and disinhibition of the trigeminal motor neurones play no part in the origin of inverse activity. The distinct brainstem syndrome can only be detected by EMG and the special clinical features.

Adult↗
PubMed1994

The effects of electrogalvanic stimulation therapy on masticatory muscle dysfunction as determined by the pantronic reproducibility index.

Patients with temporomandibular joint dysfunctional activity (TM dysfunction) present with a diverse spectrum of clinical signs and symptoms. The multifactorial aetiology of such disorders has been noted. Diagnostic and therapeutic problems arise due to the inadequacy of quantifying the dysfunction. TM dysfunction can affect the muscles of mastication which are responsible for mandibular movement. A pantographic reproducibility index (PRI) is available to quantitatively and qualitatively measure a subjects ability to reproduce mandibular border movements. Physical therapy modalities are used in the management of TM dysfunction. Electrogalvanic stimulation (EGS) is such an example. The effect of electrogalvanic stimulation on subjects with and without TM dysfunction was assessed by Pantronic PRI appraisal in 20 subjects. No statistically significant differences were noted. At the individual level, some changes were observed in susceptible subjects.

Adolescent↗
PubMed1995

Influence of stress and occlusal interference on the EMG activity of some masticatory muscles during a single mastication cycle.

The aim of the study was to investigate the influence of stress on the open-close activity in mastication, using an animal model. For this, we have compared the single-motor activities of three muscles: anterior digastric (AD), anterior temporalis (AT) and the superficial masseter (MS) in different groups of rats classed according to emotional state and dental occlusion. The EMG graphs have been analysed by the method proposed by the Weijs & Dantuma (1975). The results show that a dominant action of the stress on the AD and a combined action of the stress and the occlusal state on AT and MS occur during a single mastication cycle. A suppression of the reflex myotatic inhibition for AT and MS occurred in the presence of an occlusal interference.

Animals↗
PubMed1988

[The healing of osteotomies of the lower jaw and the adaptation of the masticatory muscles after miniplate osteosynthesis in rabbits. I. Radiologic and histological evaluation of the lower jaw].

Radiographic and histological investigations were carried out on a total of 15 rabbits after lower-jaw osteotomy and miniplate osteosynthesis. After the removal of the lower jaw (4, 8, 12 and 24 weeks) consolidation of the osteotomy surfaces without complications was observed in all animals. Radiographic examinations showed that callus formation in the operated area increased as the experiment proceeded. Histological observations made clear that only secondary bone-fracture healing resulted which must be attributed to the operation technique. These findings show that the lower jaw of the rabbit is very well suited to experimental research on miniplate osteosynthesis.

Animals↗
PubMed2000

An electromyographic investigation of masticatory muscles symmetry in normo-occlusion subjects.

The influence of occlusal conditions on stomatognathic function can be assessed by electromyography. Electromyographic activity of left and right temporal and masseter muscles was recorded in 30 young healthy adults with a normal occlusion during: (1) a 3-s maximum voluntary clench on cotton rolls positioned on the posterior teeth (standardization recording); (2) a 3-s maximum voluntary clench in intercuspal position; and (3) a 3-s alternate 'maximum' voluntary contraction and relaxation with a 1 Hz frequency. All potentials were standardized as a percentage of the maximum potential of test 1. Waveforms of paired muscles were compared by computing a percentage overlapping coefficient (ratio between each 50-ms overlapped areas and the total areas, up to 100% for symmetric muscles). Waveforms were also analysed for a laterodeviating effect on the mandible given by unbalanced muscular couples, and a torque coefficient (up to 100% for a significant laterodeviating couple on the mandible) was computed. In all subjects, both tests were performed with symmetric muscular patterns (more than 88%) and with negligible laterodeviating couples on the mandible (lower than 10%). The two coefficients allow an assessment of muscular asymmetry during static and dynamic clenching tests, and, together with the standardization of the potentials, could be a useful tool to detect functionally altered occlusal conditions, i.e. conditions where an apparent good morphological situation is not related to a correct neuromuscular status.

Adolescent↗