[Fundamental study on effects of different form of mouthguards on modal shape and damping ratio of human dry mandible].

Effect of 6 types of mouthguards on the vibratory characteristics of the human dry mandible was investigated by means of modal analysis with the impact test method. In this study, 20 test points were established on the mandible and the modal shape and damping ratio of the vibration of the mandible itself and the mandible each attached with a mouthguard were analyzed by using the FFT analyzer (CF-6400) and personal computer (PC-9801FA) with a modal analyzing software (VIBRANT-PC). The results were as follows: 1. With regard to the modal shape, there was almost no difference among the mandibles and each mandible with 6 types of mouthguard. 2. With regard to the damping ratio, there was a significant difference between the mandible itself and mandible with each mouthguard. And the effect of the mandible with each mouthguard on the damping ratio was different.