||Changes in muscle activity and physical property of foods with different textures during chewing
Iguchi, Hiroko井口, 寛子
28 , 2015-09-24 , 新潟大学
学位の種類: 博士（歯学）. 報告番号: 甲第4073号. 学位記番号: 新大院博（歯）甲第333号. 学位授与年月日: 平成27年9月24日
This study aimed to investigate how the activity of the masseter (Mas) and suprahyoid (Hyoid) muscle are influenced by the condition of food, how changes in rheological property differ in the process of food reduction between different foods, and how different salivary flow rates affect bolus-making capability during chewing in healthy humans. Ten healthy adult males participated. Electromyographic (EMG) recordings were obtained in the Mas and Hyoid muscles, and 15 g steamed rice and rice cake were prepared as test foods. In the ingestion test, the subjects were asked to eat each food in their usual manner. The chewing duration, number of chewing cycles before the first swallow, Mas and Hyoid EMG activity, and chewing cycle time were compared between the foods. The chewing duration was divided into three substages: early, middle, and late; chewing cycle time and EMG activity per chewing cycle of each substage were compared between the foods and among the substages. In the spitting test, the rheological property of the bolus at the end of each substage was compared between the foods and among the substages. Finally, stimulated salivary flow rate was measured and the relationships between the salivary flow rate and chewing duration, EMG activity, changes in the physical properties, and EMG activity were investigated. There were significant differences in the chewing duration and number of chewing cycles between the foods with similar hardness, but not in the chewing cycle time. The Mas and Hyoid EMG activity per chewing cycle for the rice cake was significantly greater than for steamed rice throughout the recording periods. While the Mas activity did not change among the substages during chewing, the Hyoid EMG activity decreased as chewing progressed. Chewing cycle time also gradually decreased as chewing progressed. The hardness of both foods initially increased, then gradually decreased back to baseline. Adhesiveness of the rice cake initially increased, and did not fall throughout the recording period; adhesiveness did not significantly change for the steamed rice. Cohesiveness barely changed for the two foods during chewing, but was significantly greater for the rice cake than for steamed rice. Finally, a correlation between the stimulated salivary flow rate and chewing performance was noted only in change in Mas EMG activity. The current results demonstrate that the Mas and Hyoid muscle activity changed as chewing progressed, and was affected by hardness, adhesiveness, and cohesiveness. Salivary flow rate may affect the changes in Mas activity in the process of bolus formation.