Abstract
The present study compares the effect on the swallowing threshold of mastication time, number of masticatory strokes, water content of the food bolus, degree of food pulverization and bolus texture between normal salivary flow and suppressed flow.
Six adults with a normal complement of teeth were selected. Cooked (steamed) rice was used as the chewing material and hyposalivation was induced with 0.5 mg of atropine sulfate. Each subject chewed and swallowed 5 g of boiled rice and the mastication time and number of masticatory strokes were determined. Mastication rhythm was then calculated. After chewing 5 g of boiled rice in time with a metronome, the subjects expectorated the food bolus. The water content of the bolus was measured using a freeze dry method. The bolus was then sieved with 10 mesh screen to measure the degree of food pulverization. The Texture Analyzer® was used for texture measurement and the Texture Expert® for data analysis. Texture was measured and analyzed using the double-bite test method. One hundred and twenty minutes after administration of atropine sulfate, to confirm that the secretion of saliva was suppressed, each subject chewed 3 g of gum base for one minute. Once suppression had been confirmed, the same test used for normal salivary secretion was repeated six times and the same items were analyzed. The results of the analyses before and after saliva suppression were compared using Student's t-test.
Significant differences in mastication time, the number of strokes, bolus water content and degree of food pulverization were found, but no significant differences in adhesiveness was found in any of the subjects when the salivary flow rate was reduced. These findings suggested that degree of food pulverization and bolus adhesion is affected by food surface moisture and may affect the swallowing threshold.
