The purpose of the present investigation was to observe the vertical motion of tongue during mastication using serial ultrasonography. Observation was made on 6 males with an average age of 28.7 with no evidence of neurological disorder. Real-time M-mode ultrasonic observation of the tongue movement during mastication was carried out in the median sagittal plane of the mandible.
The results were as follows:
1. The tongue surface in an ultrasonography M-mode image was continuously recorded without fixed contrivance of the transducer using the operator's finger and holder, because the transducer is small and light.
2. The vertical motion of the tongue was shown in two stages, the sorting out and the bolus formation stages.
3. No difference of tongue position was shown at rest and after swallowing within one individual. The significant differences of the tongue position and movement in subject-factor were analyzed, however, there was no food factor.
4. The tongue movements were slight and slow, when hardness, cohesiveness, gumminess and adhesiveness of the foods texture were high or fracturability of the texture were low.