engleski

Inhibitory reflex (silent period) in individuals without input from periodontal receptors

Inhibitory reflexes (silent periods - SPs) in jaw elevator muscles were electromyographically examined in 30 complete denture wearers (CDWs) (periodontal receptor missing), as well as in 62 controls with all the teeth and normal occlusion. SPs were elicted during ten subsequent open-close-clench cycles. The new EMGA-1 configuration and Medwin software enabled exact measurement of such short reflex appearances. Latencies in individuals with periodontal inervation varied from 12.54-12.97 ms. In individuals without periodontal inervation latencies were significantly longer (p<0.05) and varied from 16.46-17.27 ms, dependent interindividually, or between the examined muscles. Longer latencies in individuals with complete dentures could be attributed to the time needed for the denture to shift and elicit oral mucosa and/or more synapses (or a longer conduction time) from the oral mucosal receptors to the nucleus motorius n. trigemini than from the periodontal receptors. Although complete denture wearers exhibit similar patterns of muscle activity to the individuals with natural dentition, it is obvious that reflex reaction time is longer without periodontal receptors. Duration and shapes of a silent period in complete denture wearers varied dependent on the stability and occlusion of the dentures. In controls only one short duration SP could be noticed (app. 20 ms), while in CDWs all different shapes and duration of a SP complex could be noticed (prolonged, double, triple SPs, etc.), with significantly bigger amount of SPs of relative inhibition of motoneuron activity, as pure isometric activity could not be established, but some motor units still exhibited isotonic contracture due to the instability of the dentures.

electromyiography; EMG; silent period; inhibitory reflex; periodontal receptors

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