A palatal augmentation prosthesis (PAP) is used in postoperative patients with oral cancer as an intraoral appliance. The purpose of this study was to use ultrasound imaging to evaluate the effects of a PAP on lingual movement dynamics when postoperative patients with oral cancer swallowed food while wearing a PAP and to elucidate the effectiveness of the PAP. The subjects were seven patients with tongue cancer. They wore a PAP as an intraoral device to compensate for postoperative dysfunction after surgery for tongue cancer. The measurements were made by using ultrasonography. Ultrasound images of the lingual movement dynamics of the center of the tongue (central grooving of the tongue in a coronal plane, passing through the distal surfaces of both the left and right lower second premolars) during swallowing were obtained in M mode. The mean duration of lingual-palatal contact was 805.4 +/- 306.0 ms in patients without a PAP and 621.8 +/- 364.9 ms in those with a PAP. The duration decreased significantly in patients wearing a PAP (P = 0.03). The mean total duration of lingual movement was 1612.2 +/- 478.3 ms in patients without a PAP and 1245.6 +/- 272.5 ms in those with a PAP. The mean total duration decreased significantly in patients with a PAP (P = 0.03). The study results indicated that wearing an intraoral appliance may effectively help lingual movement on swallowing in postoperative patients with oral cancer.