Influence of stress and occlusal interference on the EMG activity of some masticatory muscles during a single mastication cycle.

The aim of the study was to investigate the influence of stress on the open-close activity in mastication, using an animal model. For this, we have compared the single-motor activities of three muscles: anterior digastric (AD), anterior temporalis (AT) and the superficial masseter (MS) in different groups of rats classed according to emotional state and dental occlusion. The EMG graphs have been analysed by the method proposed by the Weijs & Dantuma (1975). The results show that a dominant action of the stress on the AD and a combined action of the stress and the occlusal state on AT and MS occur during a single mastication cycle. A suppression of the reflex myotatic inhibition for AT and MS occurred in the presence of an occlusal interference.