Differences in biomechanical features of tongue pressure production between articulation and swallow.

Summary  The purpose of this study was to compare the tongue pressure against the hard palate during the articulation of a monosyllable with that during swallowing. The participants were 20 healthy adults without swallowing or articulation disorder (10 men and 10 women, mean age ± standard deviation: 22·5 ± 0·9 years). Tongue pressure during articulation of [ki] (articulatory pressure) and during dry swallowing (swallowing pressure) was recorded by a 0·1-mm-thick sensor sheet with five measuring points attached to the hard palate. Biomechanical parameters such as maximal magnitude, duration, integrated value and slope gradient were compared between articulatory pressure and swallowing pressure at each measuring point. Although swallowing pressure was produced at each measuring point, articulatory pressure was found only in the posterior circumferential parts of the hard palate and was smaller in magnitude (14·9-16·7% of swallowing pressure) and integrated value, which meant the amount of work by tongue pressing (7·0-7·9%), shorter in duration (26·6-31·8%) and shallower in slope gradient, which meant the speed of tongue pressing (26·9-27·4%). Maximal magnitude was closely correlated with duration (R(2)  = 0·386) and slope gradient (R(2)  = 0·843) for articulatory pressure. These results first show the biomechanical differences between articulation and swallowing in terms of tongue contact with the hard palate. The findings suggest that tongue pressure measurement might be a useful investigation for patients with tongue motor disorder.