The physiological mechanisms underlying Stage II transport (STII), during which comminuted solid food is transported from the oral cavity into the meso-pharynx for aggregation into a pre-swallow bolus, have yet to be clarified. The purpose of the present study was to investigate relationships between tongue-palate contact during mastication and incidence of STII by synchronised analysis of tongue pressure production on a hard palate and video-endoscopic (VE) images during mastication. Tongue pressure at 5 measuring points with an ultra-thin sensor sheet attached to the hard palate and trans-nasal VE images while masticating corned beef was recorded for 12 healthy subjects. All recordings were divided into 2 groups: mastication with STII and without STII. Tongue pressure duration was longer at the anterior-median part in the group with STII than in the group without STII. Integrated values of tongue pressure were greater at the anterior-median parts and posterior circumferential part in the group with STII. Integrated values of tongue pressure per second were greater in late-stage mastication than in early-stage mastication in the group with STII. These results suggest that the tongue-palate contacting at the anterior-median and post-circumferential parts of the hard palate is related with the incidence of STII.
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