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A system for automatic on-line analysis of electromyographic recordings during natural activity in the muscles of mastication has been developed. Acquisition and digitizing of data, their filtering to ,mean voltage, gain read-off statistical treatment, and table/graphic presentation of results are in control of a micro-computer. Amplitude and time measurements marked on direct tracings combined with tabulated statistics of the same data permit immediate check of their validity before further calculations. A screen menu directs standard examination reducing control to one pushbutton for start/compute and one for delete. With instant access to parameters of muscle action and appropriate statistics, electromyography is now available for direct functional control during clinical procedures and basic experiments. [ABSTRACT FROM AUTHOR]

A magnetic method was used to record mandibular positions and movements at the mandibular central incisors with the intercuspal position as reference. Movements were tracked separately during resting posture, swallowing, speech, chewing, and maximal opening, and then transferred to the same sagittal amid frontal kinesiogramns. In terms of mutual position of different functional areas, as well as their size and shape, the compound kinesiograms proved to be a favorable way of assessing functional characteristics of individual occlusion as well as changes thereof. [ABSTRACT FROM AUTHOR]

The present report documents, in a case of juvenile chronic arthritis (JCA) with mandibular retrognathia, three-dimensional (3D) changes in the mandible and the relationship between the mandible and the masticatory muscles resulting from treatment with the Herbst appliance after cessation of growth. Magnetic resonance scanning of the whole head was carried out before and after treatment. The mandible, the masseter, and the medial and lateral pterygoid muscles were segmented bilaterally and reconstructed in 3D for both stages. Superimposition of the datasets was carried out according to anatomical structures in the brain (cranial base). Mandibular superimposition was performed according to the mandibular symphysis and the lower mandibular border. The mandible moved forward and downward relative to the anterior cranial base. In addition, bone apposition was observed at the superior and posterior surfaces of both mandibular condyles and at the roof of the glenoid fossa. The masticatory muscles remained relatively stable in position in relation to the anterior cranial base. To our knowledge, such information in JCA patients has not previously been published in the literature. Using magnetic resonance imaging (MRI), it was possible to gain improved insight into the 3D morphology including soft tissues without the overlap of the surrounding tissues observed in the conventional radiographs. Accordingly, it is suggested that 3D magnetic resonance analysis is a more useful method for the follow-up of the JCA patients than radiographic techniques. [ABSTRACT FROM AUTHOR]

In four subjects the electrical activity in the anterior and posterior temporal and masseter muscles during maximal bite was recorded bilaterally with and without premature unilateral contact. Muscle activity was measured as the average level and the peak of the mean voltage with layers of strips of 0.05, 0.10, 0.15 and 2.0 mm, placed between first molars either on the left or the right side, and compared with the level of activity with undistrubed occlusion. Unilateral premature contact caused a significant asymmetry of action in all muscles under study with stronger activity ipsilaterally. With increasing thickness of the overlay the mean voltage decreased in parallel on both sides. We suggest that the asymmetry was caused by larger spindle afferent activity on the ipsilateral as compared to the contralateral side, and that the all-over decrease of muscle activity was due to a gradual reduction of activity from periodontal pressoreceptors. [ABSTRACT FROM AUTHOR]

In terms of the mean voltage during maximal bite in the intercuspal position we compared the strength of the temporal and masseter muscles of 39 patients with functional disorders of the chewing apparatus and 45 controls. Maximal electrical activity was significantly stronger in the controls than in the patients. Differences between the two samples with respect to sex, age, number of opposing teeth in contact and the presence of pain and tenderness tended to favor stronger activity in the controls. However, the different levels of electrical activity, especially in the case of the masseter muscles, could only be accounted for on the basis of a difference in maximal strength. We suggest that the weaker elevator muscles of the patients was a predisposing factor making these muscles less fit to endure hyperactivity induced psychologically or as a reflex response to occlusal interferences and functional disorders of the temporomandibular joints or other elements of the oral neuromuscular system. The sample of controls had much stronger elevators, less susceptible to such hyperactivity. [ABSTRACT FROM AUTHOR]