Purpose:　During the oral preparatory stage, semi-solid foods are usually mashed by the tongue against the hard palate. However, some normal subjects chew semi-solid foods as well as solid foods. This study examined whether the palatal height influences the pattern of chewing semi-solid foods.

Materials and Methods:　Fifty young females participated in the study. ① Their maxillary impressions were used to measure from the occlusal plane to the palatal base at 5-millimeter intervals. ② Maximum tongue pressure was measured three times for each subject and the mean value was used for analysis. ③ Their food processing method was classified into chewing or mashing pattern through observation and interview without giving instructions when swallowing 5 grams of jelly. ④ An imitation palatal augmentation prosthesis (PAP) using soft wax was applied to 9 subjects who were classified as chewing pattern, and the alterations in food processing method and tongue pressure were tested. ⑤ A videofluoroscopic study was done on 3 subjects to observe the swallowing pattern with and without the imitation PAP.

Results:　A value of more than 20 mm obtained from statistical analysis between chewing and compressed pattern was defined as high arch. Among the subjects with high arch, chewing pattern was significant and the tongue pressure was significantly low. When applying the imitation PAP to the 9 subjects with high arch, the chewing pattern changed to the compressed pattern and the tongue pressure increased by 5 kPa on average. The position of the bolus head at the time of triggering of pharyngeal swallowing was 100% below the vallecular for the chewing pattern, however the position changed to the oral/upper pharyngeal area by 87.5% of the time, and the vallecular aggregation time was shortened for the compressed pattern.

Discussion:　It was suggested that the subjects with high arch might chew semi-solid food because they could easily triturate and automatically propel food into the pharynx using Stage II Transport. It is hypothesized that a client with dysphagia may be able to chew semi-solid food if he/she has a high arched palate. It is proposed that observation of palatal height and chewing pattern should be added to dysphagia screening. Application of PAP might be effective for some dysphagia clients with a high arched palate.