[Mastication and the electromyographic silent period in denture wearers]. / Mastication et période de silence électromyographique chez des porteurs de prothèses.

The purpose of this study is to compare the masticatory efficiency and the physiological activity of masticatory muscles among patients with removable partial dentures (R.P.D.) and patients with natural dentition. The masticatory efficiency is assessed from the duration of chewing sequences for various foods, from the first masticatory cycle to the swallowing. The physiological activity is tested by the duration of the inhibition reflex called the "silent period" (S.P.) obtained upon each muscle examined: 29 subjects are examined, 24 of them had a R.P.D.; they were divided into four groups according to the extent of their edentation; 5 control subjects have full natural dentition. The study is performed using global electromyography of the two masseter muscles and the two anterior temporal muscles. The mastication of the control subjects appears to have a regular alternance of working potential and periods of rest. The duration of the chewing sequences is determined by the nature of the food, brief for soft food, long for hard food. The mastication of patients with R.P.D. appears more irregular with a lengthening of active phases. The duration of chewing sequences is significantly longer for the control subjects. The duration of the S.P. is 19-21 milliseconds for the masseter muscles of the patients with dentures and the control patients, and 20-22 milliseconds for the temporal muscles for the same individuals. The differences of the S.P. durations between control subjects and patients with R.P.D. is never significant.(ABSTRACT TRUNCATED AT 250 WORDS)

[A procedure for the 3-dimensional recording of human mandibular movements]. / Un procédé d'enregistrement tri-dimensionnel des mouvements de la mandibule chez l'homme.

A 3 dimensional process of recording the human mandible movements. Our system belongs to a general process made by the C.N.E.S. (Centre National d'Etudes Spatiales) in Toulouse; it records and measures the movements of body and limbs of spacemen. A test of this process is adapted for movements of mandible. The system uses a various instrumentation: two electronic cameras; infrared rays; reflectors; a multiplexor case; a magnetoscope; a dimultiplexor; a computer; two screens of control. Four reflectors are fixed on the face of subject; two others are fixed on a metallic system that is glued on the buccal face of inferior canines. These reflectors record the specific movements of mandible. Usual mastication and mastication on one side in turn are recorded in a young man with his natural teeth. Some graphs are showed for example. A data processing system measures the trajectory of mandible in the three dimensions of space, according to time and rapidity of movement. This video data processing seems to be a good method to analyze movements of mandible and mastication.

The silent period duration of the masticatory muscles.

This study was conducted to determine whether the reflex activity of the masticatory muscles is altered in prostheses wearers. The electromyographic silent period was measured on an oscilloscope screen. Thirty subjects were examined. Five subjects had natural dentitions. Twenty-five partially edentulous subjects wore removable prostheses. The silent period duration reached 18 to 21 ms on the masseter muscles and 20 to 22 ms on the temporal muscles. These values were not significantly different for subjects with and without teeth and in the control group. The duration of the silent period was the same for patients wearing prostheses and for subjects with natural teeth. This finding suggests that wearing a prosthesis does not change the normal activity of the masticatory muscles.

[Influence of age and contraction strength on the duration of the electromyographic silence period in the elevator muscles of the mandible]. / Influence de l'âge et de la force de contraction sur la durée de la période de silence électromyographique des élévateurs de la mandibule.

The electromyographic silent period (P.S.) of the elevator muscles is highly variable and seems to be influenced by many factors. The effects of the subject's age and the contraction strength of the muscle were investigated. The subject's age was studied in 51 patients divided in two groups: young adults aged 20 to 35 years and older adults, aged 50 to 65 years. The P.S. difference appearing between the two groups was very small and not significant. Age did not seem to modify the P.S. period in patients who all had satisfactory dentitions and good masticatory function. The influence of the contraction strength was compared in 21 subjects from the preceding group of 51 patients. These 21 patients were asked to perform a maximum voluntary contraction in a position of maximum intercuspidation. The P.S. period was then significantly shorter than in the case of a contraction of medium strength. Most of the workers agreed to the conclusion that an increase in contraction strength involves a reduction of the P.S. almost to its complete disappearance.

[Physiological parameters of masseter and temporal reflexes in man]. / Etude des paramètres physiologiques des réflexes masséterin et temporal chez l'homme.

This study is carried out in global electromyography, on man. The reflex activity of masseter and anterior temporal muscles is induced by a mechanical shock on the chin. The measures of the latency time duration and the silent period duration, are read in milliseconds on an oscilloscope screen. The average values of the latency time are/7.8 ms on the masseter muscle and 10 ms on the temporal muscle. The variability on this parameter, essentially neurological, according to the examined muscle, can be attributed to the diversity of the reflex passages. The average values of the duration of the silent period are of 36 ms on the masseter muscle and of 44 ms on the temporal muscle. This discrepancy is significant, and can be explained only by the specific functions of each of these two examined muscles. On the other hand, the high variability of the silent period duration, the same muscle, and in the same experiment, can be related to the strength of contraction exerted by the subject.

[The electromyographic silent period of the mandibular elevators in variations of the vertical dimension of occlusion]. / La période de silence électromyographique des élévateurs de la mandibule dans des variations de la dimension verticale d'occlusion.

The duration of the electromyographic silent period of masseter and temporal muscles was measured on nineteen healthy subjects by global electromyography. Average values were established for each muscle examined indicating a S.P. of 36.5 ms on the masseter and 44.31 ms on the temporal muscles. Artificially increasing the vertical occlusal dimension changed the S.P. duration of the four elevator muscles of the mandible very significantly. However, the temporal muscle response which gave a more predictable reduction of the S.P. duration, was different from the response of the masseter which presented either an extension or a reduction of the S.P.

[Reflex activity of the elevator muscles of the human mandible: electromyographic study]. / Activité réflexe des élévateurs de la mandibule chez l'homme: étude électromyographique.

In this study of global electromyography, of the masseter and anterior temporal muscles of man, the stimulus used was the mechanical percussion of the chin, the results being recorded on an oscilloscope. The twenty-two subjects used presented no sign of pathology after clinical examination. On the same subject, for one given muscle, the reflex was identically reproduced. The latency time was a very constant parameter; 7,8 ms for the masseter muscle and 10 ms for the temporal muscle. These values are not significantly different from one another. They are compared to those obtained by other authors. On the other hand, the reflex response of the anterior temporal muscle can present a particular pattern comparable with that of the trigemino-facial reflex.