To evaluate mastication, it is important to analyze the whole process from ingestion of foods to swallowing. However, correlation of masticatory sequence with swallowing or tongue movement is not clearly understood yet. The purpose of this study was to identify whether the timing of electromyographic (EMG) activity of jaw opening and closing muscles is differentiated between chewing and swallowingmotions.
Five healthy young dentate subjects were asked to randomly chew the test foods (pudding, raisin, and mixed) until swallowing. The surface EMGs of the bilateral posterior temporal, masseter, myohyoid, and anterior belly of digastric muscles were recorded simultaneously with mandibular movements using Mandibular Kinesiograph (Myo-Tronics). An accelerometer was applied to the larynx for extracting the swallowing cycles. Time differences of burst onset (TDBO) among workingside jaw opening and closing muscles were observed until swallowing.
TDBOs among four muscles increased during the raisin chewing sequence, and decreased during pudding chewing. The results suggested that TDBO increases during crushing and/or chewing motions, and decreases during swallowing motion.
In conclusion, evaluating time differences of EMG burst onset among the jaw opening and closing muscles might be useful for evaluating swallowing behavior.