Effect of hyposalivation on masticatory movements while eating several crackers in healthy individuals

Abstract Saliva serves to lubricate the food bolus, which suggests that saliva aids in swallowing. This study aimed to examine how a reduction in salivary flow changes mastication of solid foods with several types of hardness, taste and fat content. Twenty-one healthy adults were instructed to masticate four foods, namely rice crackers with (rice cracker 1) and without fat content and seasoning (rice cracker 2), flour crackers with fat content, and potato starch crackers without fat content, on their habitual masticatory side. Electromyograms of the masseter and suprahyoid muscles on the left and right, and subjective feeling of ease of mastication and swallowing were recorded before and after atropine sulfate administration (1 mg) to reduce salivary flow. Hyposalivation significantly extended the masticatory duration and increased the number of masticatory cycles in all of the test foods with increase of number of masticatory cycles only for rice cracker 1 and flour crackers. An increase in the masticatory cycle time and suprahyoid activity was observed from the middle to late stage of mastication with hyposalivation for rice cracker 2 and flour crackers. For potato crackers, the masticatory cycle time a bit increased throughout the masticatory period with hyposalivation without changes of muscle activity per masticatory cycles in which the size of the bolus was the largest. There was no difference in these values between the various conditions for rice cracker 1. Stimulated salivary flow was the largest for rice cracker 1. Not only fat content but also tastants and/or nutrition facts may compensate for difficulty in mastication.