外翼肌水平作用力與顳顎關節邊界條件對於下顎形變的影響－有限元素分析

Clinical findings indicated that geometrical shape of a mandible deformed during mouth opening. This deformation results in a reduction in the width of the mandibular arch. Several scholars reported that this phenomenon is strongly related to the activation of masticatory muscles. However, the effects of the movement limitation by temporomandibular joint (TMJ) on the mandibular deformation is still unclear. The aim of this study is to evaluate the boundary effects of TMJ on the madibular deformation during mouth is undergoing an opening motion. In methodology, a mandible finite element (FE) mod el with intact denture was developed. Mandibular deformations were calculated with various degrees of TMJ restriction and pterygoid muscle forces. Our results demonstrated that the mandible width between the two second molar changed from 0.19mm to 0.29mm when the movement capability of the mandible at TMJ was set to 0.4mm and 0.6mm, respectively. This result is consistent with previous clinical reports. In addition, we found that both horizontal component of the muscles forces and movement capability of mandible at TMJ have positive effect on the mandibular deformation. These findings showed that mandibular deformation is not only related to the muscle force, bit also affected by the limitation of TMJ. Accordingly, we suggest that the restrictions of the TMJ should be considered when the related clinical practice was carried out.