Ultrasonographic images of tongue movement during mastication.

We observed vertical motion of the tongue during mastication in ultrasonographic images of 6 males with an average age of 28.7 years. All subjects had complete dentition and no evidence of neurological disorders. We used a 7 MHz mechanical convex scanning transducer to obtain a continuous, real-time ultrasonic image of the tongue, and carried out real-time B-mode ultrasonic observation at the median sagittal plane of the mandible. We recorded vertical motion of the tongue in the M-mode on a line connecting the mandibular first molars. The transducer produced good quality images of the dorsal surface during mastication of peanuts, rice, crackers, boiled fish paste, pickled radishes, pudding and bananas. The transducer, which was small and light, permitted capture of the images on videotape without manual placement of the scanner. Continuous images showed that the tongue turned the food, mixed it with saliva, sorted out unsuitable particles and aided in bolus formation. Vertical motion of the tongue had two phases, sorting and bolus formation.