Evaluation of biting performance with standardized test-foods

Human masseter muscle is the main power source used for crushing or grindin g the foods. Its size is regarded as an determining factor of chewing force and function. A system of measuring the masseter muscle volume from MR ima ges was developed in this study. For a better understanding of the masseter muscle function, a standardized test-food developed in our laboratory was used. Twelve male subjects having complete dentition and healthy masticator y function were used to chew the test-foods. The EMG muscle activity of the masseter muscle during breaking and chewing the test-foods was observed. I t was found that the muscle volume was positively related to the body size. The increase of the muscle activity during breaking and chewing was almost parallel to the increase of the test-food hardness, and the increase was m ostly in the duration of muscle contraction. It was concluded that the meas urement of masseter muscle volume is possible, and our test-foods can be us ed for chewing function examination with high reliability. Within a certain level of hardness, harder food requires longer muscle contraction time ins tead of stronger muscle force to break and chew the food.