Jinushi H, Suzuki T, Naruse T, Isshiki Y
Department of Orthodontics, Tokyo Dental College, Chiba, Japan.
Bull Tokyo Dent Coll. 1997 Feb;38(1):33-41.
In order to investigate the effects of a face bow on the maxillofacial complex, we applied an analysis by a finite element method. To create a skull model, we measured an adult skull sample, and constructed a left lateral model without a mandible with 11 bones of 11 types, 30 sutures, and 3 synchondroses. The numbers of elements and nodes in the model were 1,207 and 1,539, respectively. The numbers of elements in the face bows used were 16 for the short type and 22 for the long one, respectively. Both of them were directly connected to the first molar tooth. To establish the constraining conditions, a symmetrical condition at the center of the model was chosen, and the basal part of the occipital bone was completely fixed. Each 1 kg loading was applied in three directions: 30 degrees post-superior, 0 degree posterior, and 30 degrees post-inferior. The results from this face bow loading experiment showed that the direction of displacement and the stress distribution were significantly different among the kinds of the face bows and the loading directions. For the short type face bow, simple compression appeared due to the post-superior loading and bending deformation due to the posterior and post-inferior ones. For the long type face bow, some bending deformations appeared, including anterior-elongation and posterior compression due to the post-superior loading. Post-inferior bending due to posterior loading and post-inferior bending and inferior displacement due to the post-inferior loading also appeared. Thus it is feasible to dynamically control the maxillofacial complex form by changing the type of the face bow and the direction of the loading traction.
为了研究面弓对颌面复合体的影响，我们采用有限元方法进行分析。为创建颅骨模型，我们测量了一个成人颅骨样本，并构建了一个不含下颌骨的左侧模型，该模型由11种类型的11块骨头、30条缝和3个软骨结合组成。模型中的单元数和节点数分别为1207和1539。所使用的面弓中，短型的单元数为16，长型的为22。两者均直接连接到第一磨牙。为建立约束条件，选择模型中心的对称条件，并将枕骨基部完全固定。在三个方向上分别施加1 kg的载荷：后上30度、后0度和后下30度。该面弓加载实验的结果表明，面弓类型和加载方向不同，位移方向和应力分布也存在显著差异。对于短型面弓，后上加载时出现简单压缩，后向和后下加载时出现弯曲变形。对于长型面弓，后上加载时出现一些弯曲变形，包括前伸和后压缩。后向加载时出现后下弯曲，后下加载时出现后下弯曲和向下位移。因此，通过改变面弓类型和加载牵引方向来动态控制颌面复合体形态是可行的。
