[Use of an adaptive bioregulation method for correcting masticatory muscle function in the apparatus treatment of maxillodental anomalies in children].
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Adaptation, Physiological↗
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The action of three types of functional appliances on the activity of the masticatory muscles.
Three commonly used functional appliances; namely, the Herbst, Frankel, and a simulation of the Clark twin block appliances were used to test the lateral pterygoid muscle hypothesis. This hypothesis states that postural and functional activity of the superior and inferior heads of the lateral pterygoid muscle increases after the insertion of a functional appliance. This increased activity, especially in the superior head of the lateral pterygoid muscle then acts to stimulate increased condylar growth. The electromyographic (EMG) activity of the masseter, digastric, superior, and inferior heads of the lateral pterygoid muscles was monitored with chronically inserted EMG electrodes, in nonhuman primates, to determine whether functional appliances actually produce a change in functional activity of these muscles. The involuntary swallow was used to represent functional activity. Thus swallow-related EMG activity levels were monitored longitudinally and compared before and after the insertion of each appliance type. The insertion of these three appliances was associated with a decrease in functional EMG activity of the four muscles. This decrease was statistically significant in all muscles 3 and 6 weeks after appliance insertion. This is consistent with our previous findings that functional appliances are associated with a decrease in the postural activity of the above muscles in nonhuman primates. In view of the fact that the animals showed large skeletal changes in the temporomandibular facial area, this study could not support the lateral pterygoid muscle hypothesis.
Analysis of Variance↗
[Fast Fourier transformation analysis of masticatory muscle activity in children. 1. Reproducibility].
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Adult↗
[Electromyographic study of masticatory muscle fatigue and recovery under voluntary contraction. 2. Comparison between normal subjects and craniomandibular disorder patients].
During fatiguing clenching, power spectrum in the surface electromyogram decrease to the lower frequency. The phenomenon has been expected to indicate the fatiguing condition. However, the underlying mechanism between the muscle fatigue and the power spectrum shift is still unclear. Therefore, it may be difficult to employ the spectrum shift for the diagnostic process. The aim of this paper was to clarify the mechanism in the power spectrum shift and to find a possible parameter for diagnostic process. The shift in the mean power frequency (MPF) was observed during fatiguing clenching and the successive recovery period from a normal group (n = 47) and a craniomandibular disorder patient group (n = 46). The results suggested that the power spectrum shift during the fatiguing clenching might be due to a reflex inhibition at the motoneuron level. From the comparison between the normal group and the dysfunctional group, there was larger difference in normalized absolute MPF values between the right and left muscles. Also the larger variance was seen during the fatiguing process and the recovery process in the dysfunctional group than in the normal group.
Bruxism↗
[Disorders of the coordination of masticatory muscles in lesions of the brain stem].
Observations of 10 patients were reported. In addition to other neurologic deficits, coordination of the trigeminus, a motor nerve, may also be disturbed with brain lesions. Disturbance of bilateral synergism can be demonstrated with the EMG. The muscles closing the jaw on the affected side are paradoxically innervated when the jaw is opened, i.e., they function like antagonists to the muscles responsible for jaw closure on the opposite side. This condition may produce trismus. Similar central disturbances in bilateral coordination of the ocular muscles have also been established. Bilateral synergism of the trigeminus is also controlled via a center in the brain stem.
Brain Stem↗
[Functional morphology of the maxillo-mandibular apparatus in the mini-Lewe minipig. 5. Structural and functional changes of the masticatory muscles and their dry weight development].
The basic pinnate structures caused by Sehnenspiegel in the jaw muscles are already present in newborn animals. The functional changes in the jaw muscles are described in terms of an analysis of force components based on the dry weights of the individual muscles involved in chewing action. Although the protractive and retractive components are relatively large in newborn pigs, the adductive components predominate clearly in adult animals. The development of the jaw muscles in terms of dry weight shows that the masseter muscle predominates at all ages. The miniature pig MINI-LEWE is assigned to the herbivorous type on the basis of the dry weight distribution.
Aging↗
[Functional disorders of the masticatory muscles and temporomandibular joint in pathological tooth abrasion].
Altogether 568 patients, 308 women and 260 men aged 30 to 64 with abnormal teeth abrasion were examined by clinical, anthropometric, X-ray (spot and panoramic radiography of the teeth and jaws, tomography of the temporomandibular joint), electromyography, and rheoparodontography. Pathological teeth abrasion was associated with various morphological and functional disturbances in the maxillodental system. Two types of abrasion were distinguished: with and without masticatory function disorders. The latter condition was detected in 252 (44.36%) patients. Painful dysfunction of the temporomandibular joint was observed in 66 (11.6%) patients. Three factors contribute to the pathogenesis of these functional disorders in abnormal teeth abrasion: reduction of occlusion height (interalveolar distance) and shortening of the lower third of the face, blocking of mandibular movements, lateral and distal shift of the mandible.
Adult↗
[Masticatory muscle activity in a patient with implant dentures. A case of Kennedy Class II division 1].
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Dental Implantation, Endosseous↗
Latency and inhibition of human masticatory muscles following stimuli.
Latency-inhibition behavior was always produced in contracting anterior temporal muscles following the application of various stimuli to the teeth and jaws of 31 subjects. Statistically significant differences in duration were generally observed with different procedures. In half of the subjects, the first one or two closures in a sequence of repetitive tapping evoked a longer period of inhibition than subsequent closures. No reflex or latency-inhibition behavior could be produced in contracting digastric muscles. Comparisons of means for individual subjects did not follow the pattern suggested by comparisons of total sample means in almost half of the subjects.
Electromyography↗
Histoenzymology and morphometry of the masticatory muscles of tufted capuchin monkey (Cebus apella Linnaeus, 1758).
Samples of the anterior and posterior regions of the masseter and temporal muscles and of the anterior belly of the digastric muscle of 4 adult male tufted capuchin monkeys (Cebus apella) were removed and stained with HE and submitted to the m-ATPase reaction (with alkaline and acid preincubation) and to the NADH-TR and SDH reactions. The results of the histoenzymologic reactions were similar, except for acid reversal which did not occur in fibers of the fast glycolytic (FG) type in the mandibular locomotor muscles. FG fibers had a larger area and were more frequent in all regions studied. No significant differences in frequency or area of each fiber type were detected, considering the anterior and posterior regions of the masseter and temporal muscles. The frequency of fibers of the fast oxidative glycolytic (FOG) and slow oxidative (SO) types and of FOG area differed significantly between the anterior belly of the digastric muscle and the mandibular locomotor muscle. The predominance of fast twitch (FG and FOG) fibers and the multipenniform and bipenniform internal architecture of the masseter and temporal muscles, respectively, are characteristics that permit the powerful bite typical of tufted capuchin monkeys.
Adenosine Triphosphatases↗
[The effect of a modified blood supply on the craniofacial growth of rabbits. 2. Masticatory muscles].
After ligation of the right common carotid artery, the dry weight of the muscles of mastication on the ligated side did not differ from that of the control animals between the 45th and 225th d of life. On the opposite side, however, the muscles were in some cases significantly heavier than those of the control animals, particularly in male rabbits with ligated common carotid arteries. The methodical application of these results is proposed.
Animals↗
Symmetric force response of human masticatory muscles to stretch and unloading.
During chewing, the force exerted by the jaw-closing muscles must constantly adapt to changing resistances between the teeth, as the food is broken down. In the present study, the changes in biting force resulting from small, controlled displacements imposed on isometrically contracting jaw-closing muscles were measured. We found that the force changes resulting from small loading and unloading movements were normally highly symmetrical. The initial force change was linear, and preceded the onset of reflex changes in muscle activity. Later changes in force were the result of both short- and long-latency reflexes in the jaw-closing muscles, the long-latency component being quantitatively greater. The long-latency unloading reflex in the jaw-closing muscles has not been described hitherto. The symmetry of force increase with loading and decrease with unloading was absent in one subject with atypical stretch and H-reflexes.
Adult↗
The influence of altered working-side occlusal guidance on masticatory muscles and related jaw movement.
The effect of four different occlusal situations (group function, canine guidance, working side occlusal interference, and hyperbalancing occlusal interference) on EMG activity in jaw elevator muscles and related mandibular movement was investigated on 12 subjects. With a computer-based system, EMG and displacement signals were collected simultaneously during specific functional (unilateral chewing) and parafunctional tasks (mandibular gliding movements and various tooth clenching efforts) and analyzed quantitatively. When a naturally acquired group function was temporarily and artificially changed into a dominant canine guidance, a significant general reduction of elevator muscle activity was observed when subjects exerted full isometric tooth-clenching efforts in a lateral mandibular position. The original muscular coordination pattern (relative contraction from muscle to muscle) remained unaltered during this test. With respect to unilateral chewing, no significant alterations in the activity or coordination of the muscles occurred when an artificial canine guidance was introduced. Introduction of a hyperbalancing occlusal contact caused significant alterations in muscle activity and coordination during maximal tooth clenching in a lateral mandibular position. A marked shift of temporal muscle EMG activity toward the side of the interference and unchanged bilateral activity of the two masseter muscles were observed. The results suggest that canine-protected occlusions do not significantly alter muscle activity during mastication but significantly reduce muscle activity during parafunctional clenching. They also suggest that non-working side contacts dramatically alter the distribution of muscle activity during parafunctional clenching, and that this redistribution may affect the nature of reaction forces at the temporomandibular joints.
Adult↗
Ultrasonography and electromyography of masticatory muscles in a group of adolescents with signs and symptoms of TMD.
The thickness and electrical activity of masseter and anterior temporalis muscles were compared in adolescents with and without signs and symptoms of TMD. Forty individuals were selected using the Cranio Mandibular Index and a questionnaire. There was no significant correlation between thickness and activity (p > 0.05). However, there were correlations between thickness and weight and height (p < 0.05). The effect of signs and symptoms on muscle thickness and activity was weak, considering the low CMI scores found.
Adolescent↗
Demonstration of the nerve distribution of the masticatory muscles in rabbits (Oryctolagus cuniculus).
Two methods can be used in order to demonstrate the nerve distribution of an organ. One is the three-dimensional reconstruction of the innervation pattern of the organ by tracing images of that organ from serial histological sections. The other is the in toto staining of the organ with subsequent clearing of the muscles. In the present study, in order to visualize the nerve distribution of the organ, that organ was completely cleared and the nerve fibres were stained. Detailed morphological structure of the intramuscular nerve distribution of a certain region and its functions are of importance not only for anatomists and physiologists but also for clinicians. In this study eight New Zealand rabbits were used to visualize the intramuscular nerve distribution of the muscles involved in mastication (temporalis m., pterygoideus medialis m., digastricus m., retractor mandibulae m. and masseter m.). The main nerve bundle was observed entering into the muscle as a single trunk and dividing into three branches in the muscle. These branches were also observed dividing into several subbranches while going to the periphery. When the samples were examined under a stereomicroscope, 'Y'-, 'I'- and 'O'-shaped communications between those branches were observed.
Animals↗
Masticatory muscle activity as a function of parafunctional, active and passive oral behavioural patterns.
Oral behavioural patterns have received limited empirical support for their causal role in the development of head and facial pain. The present study was designed to assess electromyographic (EMG) variations in six muscle groups (i.e., bilateral masseter, temporalis and orbicularis oris) as a function of various oral behavioural patterns. A second purpose was to determine whether mandibular movement patterns and specific oral behaviours could be predicted by EMG patterns. Eleven non-pain subjects followed each of twenty oral behavioural patterns while EMG was recorded. Electromyographic change scores were computed for each behaviour relative to baseline measures. Initial analyses were performed using factorial repeated measures ANOVAS. Using post hoc analyses as general guides, specific EMG criteria were developed for classifying mandibular movements. For most subjects, EMG patterns accurately classified teeth clenching, protrusive/retrusive movements, right movements, left movements and lip movement patterns. Wide individual variations were found among muscle groups for identical behaviours. The association between particular oral behaviours and EMG patterns may explain 'sinus' headaches and certain types of facial pain.
Adolescent↗
[Electromyographic study of masticatory muscle fatigue and recovery under voluntary contraction. 1. Comparison of spectrum parameters for the power spectral shift].
The aim of this paper was to determine the best parameter for describing the muscle fatiguing process. Three parameters of mean power frequency (MPF), median frequency (MF), and peak frequency (PF) were tested with healthy subjects. During 10 sessions at more than one week intervals, the subjects performed the same endurance test with clenching at 80% of maximal electromyographic activity. Changes in the surface electromyogram of the bilateral masseter and temporal muscles were obtained in the above three parameters. From the comparison between the three parameters, PF showed the largest scattering, and MPF indicated a clear difference calculated from the values before and after fatigue. Thus it is concluded that MPF may be the best parameter.
Electromyography↗
[The development of strength in the masticatory muscles and its sensory control].
By means of inductive dynamometers the absolute force of mastication as well as factors influencing that force are studied. In addition to the mechanical effects resulting from the lower jaw's acting as lever arm, the pulp, especially its coronal portion, showed a dominating influence on the extent of the developed adduction force.
Dental Pulp↗