Abstract
Masticatory movements are a result of the complex coordination of the neuromuscular system. The purpose of the this study was to determine whether measuring and observation of these movements with linear envelope analysis is a viable approach. Three normal volunteers (average age of 25.3) participated in this experiment. All had complete natural dentition that included the second molar, and none showed any signs or symptoms of problems in the stomatognathic system. Bipolar surface EMG of the anterior temporal and masseter muscles, tongue and mandibular movements were simultaneously recorded during gum chewing, which they were instructed to chew ad lib for 90 seconds. Tongue movement was observed through ultrasonography at the median saggital plane of a line bisecting the right and left mandibular first molars, and a mandibular kinesiograph was used for tracking incisal point movement during chewing. It was possible to trace normalized linear envelopes for tongue movements, mandibular movements and EMG activity of jaw elevator muscles for each stroke during chewing.
Results:
1. The lowest point of tongue movement was occlusal phase of mandibular movement each stroke. Tongue and mandibular movements were functionally cooperated.
2. Peak activity for anterior temporal and masseter muscles was at between closing stroke and occlusal phase.
3. EMG profiles showed stable pattern after 60-75 seconds after initiation of chewing.
