Chin Cap による顎顔面頭蓋の変形様相に関する力学的研究

Abstract

Many studies on the effects of chin cap appliance have been reported, but few mechanical investigations can be found on the craniofacial complex dealing with dried bones or simulated models. The present study was conducted to investigate the nature of reaction of craniofacial complex subjected to the chin cap force. Moreover, in order to examine the relationship between the bone deformation pattern in vivo and that in vitro, the data recorded in the dried skeleton of monkey (Macaca fuscata) subjected to the same experiment as for the human were compared with the previous report dealing with living monkey. The strain distribution was recorded, applying the static load ranging from 500 to 3, 000g to the midline of the chin toward condylar head in human and monkey subjects. The experimental data obtained were as follows : 1. The amount of strain markedly depended on the value of density index, which was defined as the ratio of the weight to the geometrical size of the skull. The smaller the value of this index, the larger the amount of strain. 2. A large amount of strain was observed in the lateral surface of mandibular ramus and retromolar area. In addition, strains were widely noted in the areas of craniofacial skeleton. 3. The deformation pattern in the mandible will be characterized as follows : closure of the gonial angle, inward bending at the body and superior region of the gonial angle in the child and adult, and inward bending in the child and outward bending in the adult from inferior region of the gonial angle to posterior part of the ramus. 4. The deformation pattern in the mandible of the monkey was found to be similar to that observed in the human subject (adult).