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Results for “Pterygoid Muscles”

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At least 91 records · Page 5Linked to original sources

PubMed2003

[Characteristic changes of acetylcholine receptor in rat lateral pterygoid muscles after functional mandibule advancement].

OBJECTIVE: The purpose of this study was to evaluate the maximum binding(Bmax) and affinity(Kd value) changes of acetylcholine receptor (n-AchR) in rat lateral pterygoid muscles after functional mandibule advancement. METHODS: 40 five-weeks-old male Sprague-Dawley rats were equally divided into experimental and control group. The mimic functional appliances were used in experiment group and the rats were killed after 1, 3, 7, 14 days. Radio-ligand binding assay (RBA) was applied to determine the maximum binding(Bmax) and Kd value of n-AchR of lateral pterygoid muscle. RESULTS: The Bmax of n-AchR in experimental group was higher than that in control group and the Kd value always kept in high level. CONCLUSION: The functional orthopedics can increase the Bmax of n-AchR in rapid growing rat lateral pterygoid muscles.

Animals↗

PubMed1991

[A histological study of the meniscal insertion of the external pterygoid muscle].

The paper reports a study of the relationship between the upper head of the pterygoid muscle and the temporomandibular joint disc. Using optical microscopy, TMJ serial sections of 10 human embryos and fetuses aged from 6 to 22 weeks were examined. From the observation of serial sections, it appears that from the start of histogenesis the lateral pterygoid muscle is in contact with the condylar blastema and later with the disc and the condyle. A fibrous attachment was detected between the muscle tendon and the meniscus, and oxytalan and elastic fibres were observed near this attachment.

Gestational Age↗

PubMed1994

[Magnetic resonance imaging of lateral pterygoid muscle in temporomandibular joint dysfunction syndrome].

Fifteen TMJS of fifteen normal controls and thirty TMJs of thirty patients with TMJDS were studied with head-coil MR imaging. T1 weighted oblique sagittal scanning in closed and opened mouth and T2 weighted oblique sagittal scanning in closed mouth were used to evaluate the lateral pterygoid muscle of the controls and the patients. The upper head of lateral pterygoid muscle was found shorter and straighter in opened mouth than that in closed mouth. It is suggested that the upper head is in the state of contraction in opened mouth. The same finding was also found in the patients with TMJDS in opened mouth. Edema and effusion in lateral pterygoid muscle were found in 80% patients with TMJDS on T2 weighted image.

Adolescent↗

PubMed1988

Insertions of the lateral pterygoid muscle: an anatomic study of the human temporomandibular joint.

The objective of this investigation was to evaluate the anatomic relationships of the lateral pterygoid muscle with the disc-condyle complex using an acrylic embedding technique to obtain anatomic serial cuts of a solid block containing the temporomandibular joint (TMJ) and the neighboring structures. The fibers of the upper and lower heads were found to be fused in front of the TMJ and to constitute medially a strong muscular wall. The lateral third of the anterior band of the disc was free of any muscle insertions and related anteriorly with loose connective tissue; the middle third showed fibers that run under the anterior band of the disc and attached in the upper part of the condylar fovea. Only the medial portion demonstrated both fibers running into the disc and fibers inserting into the bone. The fibers inserted into the bone run under those attached into the disc and terminated below the medial pole of the condyle binding the disc tightly over the medial pole. This study demonstrates that the main insertions of the superior head are not into the disc but into the condyle. Considering the anatomic organization of the upper head, the explanation of anterior displacement of the disc due to a spastic activity of this muscle alone is not probable. Hypotonicity, not hyperactivity, of the upper head may contribute to an anterior and medial disc displacement.

Dissection↗

PubMed1996

[An electromyographic study of the exposed lateral pterygoid muscle in monkey].

The purpose of the present study is to observe the electromyogram (EGM) manifestations of the lateral pterygoid muscle (LPM) in monkey during mouth opening and closing movements. The lateral pterygoid muscle of five healthy monkeys (macaques) was exposed by operation under general anesthsia and the electropolar needles were placed into the superior and inferior head of LPM respectively. The EMG manifestations of the superior and inferior head of LPM were recorded by O.T.E. Biomedica EMG Recorder during the natural condition and the movements of opening and closing mouth after complete recovery from anesthesia. It has been found that the two heads acted synergistically only in opening movement and no activity was noted in closing movement. This finding disagrees with the previous viewpoint that the function of the superior and inferior head of LPM is independent.

Animals↗

PubMed1989

Reflex inhibition in single motor units of the human lateral pterygoid muscle.

Reflex electromyographic (EMG) responses to electrical stimulation in the human lateral pterygoid muscle are ambiguous, possibly due to previous methods of EMG analysis. In a rigorous paradigm, single motor unit (SMU) activity in 30 units was recorded in the inferior head of the lateral pterygoid muscle in 5 subjects. Single pulses of 1 ms duration at 6T intensity were delivered via bipolar electrodes attached to the gingiva near the maxillary canine. The firing frequency of each SMU was constrained to 10 or 15 Hz by biofeedback techniques. Stimuli were delivered at known positions relative to a series of preselected spikes. Successive stimuli were delivered sequentially by increasing increments of 1 ms. SMUs were activated consistently by incisal clenching and jaw opening against resistance applied to the chin. When the SMU prestimulus firing frequency was constrained at 10 Hz, each unit displayed an inhibitory effect which was highly dependent on the stimulus position. In units with a constrained firing frequency of 15 Hz, no effect was observed. These findings qualitatively resemble responses observed in the human masseter muscle.

Action Potentials↗

PubMed1992

[Histological observations on structure of endomysium, perimysium and epimysium of lateral pterygoid muscle in rat].

To understand the muscle as a locomotorium, I observed the structure of the connective tissue sheaths (the endomysium, the perimysium and the epimysium) in the mature rat lateral pterygoid muscle. The following results were obtained using the macroscopy and light and electron microscopy. The lateral pterygoid muscle consists of two parts. The superior head originates from the basisphenoid and is mainly inserted into the articular disk and capsule. The inferior head originates from the lateral pterygoid processus and is mainly inserted into the condylar processus of the mandible. The perimysium is thick and bound the fasciculus secondarily as sheaths near the insertion of the superior head. The collagenous fibers are very fine in the endomysium. The collagenous fibers that make the connective tissue sheaths arrange on a skew against the muscle fibers, but parallel around the origin and the insertion. It seems that the connective tissue sheaths in the rat lateral pterygoid muscle, in view of the morphology, retain the forms of fasciculus, act as the runways for the muscle fibers in time of expansion and contraction and offer spaces for the attachment of the muscle fibers.

Animals↗

PubMed1993

[Analysis of the image of external pterygoid muscle during close and wide open of the jaw by condylo-pterygo-maxillo-oblique projection in magnetic resonance].

External pterygoid muscle is an important muscle. It is easy to be hurt by acute and chronic trauma which may become one of the chief cause of TMJDS. It is difficult to be studied, because it locates deeply. It is covered by thick soft and hard tissues. That is why the questions about its anatomy and physiological functions have been debated. In this paper, the changes of images form of external pterygoid muscle during the jaw closing and wide opening were observed and analysed in 14 cases, 25 sides, of adult men and women. By CPMOP in MR. The results can by concluded that (1) the upper head of this muscle inserts fully or mainly to the condyle pterygoid fossa; (2) the direction of the muscle fibers is not entirely horizontal but with some inclined and (3) the two heads of this muscle are relaxed in the jaw closing and are contracted in the jaw wide opening synchronously.

Adult↗

PubMed1996

Histological features of endomysium, perimysium and epimysium in rat lateral pterygoid muscle.

The distribution of the endomysium, perimysium, and epimysium and their constituent connective tissue fiber types in the mature rat lateral pterygoid muscle was examined with the light microscope. The endomysium and perimysium were relatively thin and consisted mainly of reticular fibers. The epimysium was thicker than the intramuscular sheaths and consisted of both collagen and reticular fibers; however, the thickness and constitutent connective tissue fiber types of these sheaths varied regionally. Near the articular capsule and disc, the endomysium, perimysium, and epimysium were all thicker than in other regions of the muscle and consisted of collagen, reticular, and elastic fibers. The perimysium bound the bundles of muscle fibers together and frequently included blood vessels and nerves. As the superior head of the pterygoid muscle approached its insertion, sheaths of perimysium divided this head into smaller and smaller bundles of muscle fibers. In the inferior head, some of the perimysial sheaths and part of the epimysium were aponeurotic, and many muscle fibers attached to them. There were few such aponeurotic regions in the superior head.

Animals↗

PubMed1982

[Role of the lateral pterygoid muscle in mandibular movements].

The two bundles, superior and inferior, of the lateral pterygoid muscle were studied by EMG and integrated EMG during various movements of the mandible in 36 children and 2 adults. At the same time, the EMG of other masticatory muscles was also recorded. The functional specialization of the two bundles is expressed by different levels of recruitment: In the inferior bundle (pterygo-condylian,) electrical activity is stronger in the movements of opening, antepulsion and controlaterality. In the superior bundle (spheno-meniscal), activity is stronger in the movements of occlusion and retraction. Thus the inferior bundle principally has a function of stabilization of the temporomandibular joint.

Adolescent↗

PubMed1989

Relationships between the size and spatial morphology of human masseter and medial pterygoid muscles, the craniofacial skeleton, and jaw biomechanics.

The relationship between human craniofacial morphology and the biomechanical efficiency of bite force generation in widely varying muscular and skeletal types is unknown. To address this problem, we selected 22 subjects with different facial morphologies and used magnetic resonance imaging, cephalometric radiography, and data from dental casts to reconstruct their craniofacial tissues in three dimensions. Conventional cephalometric analyses were carried out, and the cross-sectional sizes of the masseter and medial pterygoid muscles were measured from reconstituted sections. The potential abilities of the muscles to generate bite forces at the molar teeth and mandibular condyles were calculated according to static equilibrium theory using muscle, first molar, and condylar moment arms. On average, the masseter muscle was about 66% larger in cross section than the medial pterygoid and was inclined more anteriorly relative to the functional occlusal plane. There was a significant positive correlation (P less than 0.01) between the cross-sectional areas of the masseter and medial pterygoid muscles (r = 0.75) and between the bizygomatic arch width and masseter cross-sectional area (r = 0.56) and medial pterygoid cross-sectional area (r = 0.69). The masseter muscle was always a more efficient producer of vertically oriented bite force than the medial pterygoid. Putative bite force from the medial pterygoid muscle alone correlated positively with mandibular length and inversely with upper face height. When muscle and tooth moment arms were considered together, a system efficient at producing force on the first molar was statistically associated with a face having a large intergonial width, small intercondylar width, narrow dental arch, forward maxilla, and forward mandible. There was no significant correlation between muscle cross-sectional areas and their respective putative bite forces. This suggests that there is no simple relationship between the tension-generating capacity of the muscles and their mechanical efficiency as described by their spatial arrangement. The study shows that in a modern human population so many combinations of biomechanically relevant variables are possible that subjects cannot easily be placed into ideal or nonideal categories for producing molar force. Our findings also confirm the impression that similar bite-force efficiencies can be found in subjects with disparate facial features.

Adult↗

PubMed1999

Electromyographic evidence for functional heterogeneity in the inferior head of the human lateral pterygoid muscle: a preliminary multi-unit study.

OBJECTIVE: Functional heterogeneity, i.e. regional or selective activation of subpopulations of fibres within a muscle, has been described in some jaw and limb muscles. Each head of the lateral pterygoid muscle may also be functionally heterogeneous. The aims of this investigation were to develop a technique to test this hypothesis, and to use this technique to determine whether there is any multi-unit electromyographic (EMG) evidence for functional heterogeneity within the inferior head of the lateral pterygoid (IHLP). METHODS: In 3 human subjects without craniomandibular disorders, recordings were made of condylar movement and multi-unit EMG activity from two sites in the IHLP during repeated trials of a contralateral (n = 21) and a protrusive (n = 26) jaw movement. The recording sites within IHLP were approached extraorally (labelled IHLP-extra) and were verified by computer tomography (CT); the other (IHLP-intra) were from sites in IHLP approached intraorally. RESULTS: In each subject, the time of occurrence of the peak filtered signal from IHLP-extra was significantly different (P<0.05) from IHLP-intra for all protrusion trials but not for contralateral trials. CONCLUSIONS: The data suggest a task-dependent change in motor unit recruitment order within IHLP and that IHLP is functionally heterogeneous.

Adult↗

PubMed1990

[Fundamental properties of the human lateral pterygoid muscle activity and quantitative observation in relation to vertical dimension and bite force].

The purpose of this study is to investigate the fundamental property of the superior head of the lateral pterygoid muscle (LPT) of the human beings. The experiments were performed on 6 subjects. Electromyographic activity of the superior head of LPT were simultaneously recorded with masseter, temporal and digastric muscle. The findings may be summarized as follows: 1. Superior head of LPT showed the maximum activity during closing and clenching. 2. Superior head of LPT showed remarkable tonic activity at rest position and notable activity during swallowing and passive retrusion. 3. Superior head of LPT activity was related to vertical dimension and bite force quantitatively, but such relationship was quite different from masseter and temporal muscle. 4. Jaw-jerk reflex was evoked by mechanical chin tap in the superior head of LPT, masseter and temporal muscle showing identical time course. 5. Periodontal excitatory reflex was evoked by mechanical tooth stimulation in the superior head of LPT and temporal muscle. From these findings it was concluded that superior head of LPT was qualitatively similar to but quantitatively distinct from jaw closing muscles such as masseter and temporal muscle.

Bite Force↗

PubMed2001

Comparison of phosphocreatine concentration in the human masseter and medial pterygoid muscles by 31P-CSI.

The aim of this study is to compare phosphocreatine (PCr) concentrations of human masseter and medial pterygoid muscles by a recently developed localized magnetic resonance spectroscopy (MRS) method, chemical shift imaging (CSI). The characteristic spectra of phosphorous metabolites including PCr and beta-ATP from the superficial part of the masseter (SM) and the deep part of the masseter (DM) and the medial pterygoid muscles (MPt) from 11 volunteers, 20-27-year-old were obtained. The study clearly demonstrated higher PCr/beta-ATP in the SM and MPt than in the DM both in mean values (P < 0.01) and in individual subjects. The results indicate that SM and MPt are power producers. There were no significant differences in the mean values of the PCr/beta-ATP ratios in SM and MPt, however, the PCr/beta-ATP ratios varied individually and the subjects could be divided into three distinct groups: values of MPt higher than SM (group A, 4 subjects); values of MPt almost equal to SM (group B, 3 subjects); and values of MPt lower than SM (group C, 4 subjects). There appears to be a close relationship between the PCr content as determined in the groups here and occlusal guidance.

Adenosine Triphosphate↗

PubMed1990

Role of the lateral pterygoid muscle and meniscotemporomandibular frenum in spontaneous growth of the mandible and in growth stimulated by the postural hyperpropulsor.

Our experimental studies in young rats represent an attempt to elucidate the respective roles of the lateral pterygoid muscle (LPM), the temporomandibular frenum (TMF), and the postural hyperpropulsor (Hp) in the control of the growth rate, the growth direction, and the growth amount of the condylar cartilage. Even after surgical resection of the LPM, the growth of the condylar cartilage and the lengthening of the mandible continue but are significantly decreased. Also, the stimulating effect of postural hyperpropulsion on the condylar cartilage and mandibular growth is much less intense after resection of the LPM. The TMF, which has a blood-circulating and a biomechanical component, appears to be a mediator of the LPM in the control of the condylar cartilage growth. After the surgical resection of the TMF, the growth the condylar cartilage and the lengthening of the mandible continue but are significantly diminished.

Activator Appliances↗

PubMed1992

Biomechanical model of the human mandible: a hypothesis involving stabilizing activity of the superior belly of lateral pterygoid muscle.

A new biomechanical analog for the human mandible is proposed. The biomechanics of the human mandible can be explained by a simple support model, where muscular forces are produced by the masseter, medial pterygoid, temporal, and superior lateral pterygoid muscle components, and reaction forces are produced by the occlusal surfaces and condyle. All forces are resolved into components orthogonal and parallel to the temporal articular plane (articular eminence). In this model, one component of muscular forces is parallel to the temporal articular plane. The influence of the inclination of the occlusal plane, the inclination of the temporal articular plane, the position of the resultant of the occlusal reactions, and the relative contribution of the different jaw elevator muscles on the parallel and orthogonal components are evaluated according to a computer model of the system. The muscular force parallel to the temporal articular plane may be produced by the superior lateral pterygoid muscle, which during clenching acts as a stabilizer of the mandibular condyle to prevent posterior dislocation and compression of nonarticular tissues.

Biomechanical Phenomena↗

PubMed2006

Heterogeneous activation of the medial pterygoid muscle during simulated clenching.

The aim of this study was to investigate whether the medial pterygoid muscle shows differential activation under experimental conditions simulating force generation during jaw clenching. To answer this question, the electromyographic activity of the right medial pterygoid was recorded with two intramuscular electrodes placed in an anterior and posterior muscle region, respectively. Intraoral force transfer and force measurement were achieved by a central bearing pin device equipped with strain gauges. The activity distribution in the muscle was recorded in a central mandibular position during generation of eight different force vectors at a constant amount of force (F=150 N). The investigated muscle regions showed different amounts of EMG activity. The relative intensity of the activation in the two regions changed depending on the task. In other words, the muscle regions demonstrated heterogeneous changes of the EMG pattern for various motor tasks. The results indicate a heterogeneous activation of the medial pterygoid muscle under test conditions simulating force generation during clenching. This muscle behaviour might offer an explanatory model for the therapeutic effects of oral splints.

Adult↗

PubMed1997

[Electromyography studies for objective assessment of loss of function of the lateral pterygoid muscles after dislocation fractures of the mandibular processes].

The aim of treatment for luxation fractures of the mandibular articular processes is not only complete anatomical restitution but also restoration of the mobility. In a retrospective study on 242 patients after operative and conservative treatment, it was possible to demonstrate that there are no correlations between fragment position and functional result. Functional restitution was observed after conservative treatment in 65% of cases and after operative treatment in 57%. In order to establish the causes for dysfunction of the lateral pterygoid muscle an electromyographical technique was developed to dissipate the action potentials of the muscle. Another retrospective study, performed in 23 patients with dysfunction of the mandible revealed loss of activity of the lateral pterygoid muscle after fracture treatment, independent of the treatment method, in 11.5% of cases (two patients). Without any connection to the treatment method, the remaining results permit to conclude that there are preoperative neurological defects. Therefore the pre- and posttherapeutic functions of muscles and nerves were investigated in a prospective study on 18 patients. Before the treatment 16.6% of the patients (n = 3) showed defects of the lateral pterygoid nerve with a resulting loss of muscle function. According to the findings, residual dysfunction of the lateral pterygoid muscle is determined by the extend of the traumatic nerve injury, independent of the treatment method. In the case of axonal defects of the pterygoid nerve, there can be no expectation of a restitutio ad integrum after the operative fragment position.

Adolescent↗