Abstract
This study analyzed the movements of tongue and the mandible related to progress of mastication. Six subjects (average age: 26.7, range 23-29yrs) with no evidence of neurological disorders were given rice cracker, boiled fish paste and pickled radish as foodstuffs and asked to chew freely and swallow. Tongue movement was observed through ultrasonography and mandibular movement with the MKG-K6 device. The oral stage of mastication was divided into three phases: sorting out (SO-phase), development (DE-phase) and bolus formation (BF-phase) . Results:
1. Mandibular movement: As mastication progressed the duration of closing phase became shorter and the duration of occlusal phase longer. There were no specific change in the duration of opening phase.
2. Tongue movement: As mastication progressed no change occurred in the time lag between beginning points of closing stroke and lowest points of tongue stroke. Time lag between beginning points of occlusal phase and lowest points of tongue stroke shortened. Time lag between beginning points of opening phase and lowest points of tongue stroke did not change.
3. The SO-phase was significantly different among foodstuffs as mastication progressed; however, the BF-phase was not.
