中位前牵引颅面骨骼的三维有限元研究

Three-dimensional finite element analysis of craniofacial skeleton protraction at mediumposition

目的探讨中位骨骼前牵引和以牙齿承力前牵引的生物力学变化特点。方法在三维有限元颅面复合体模型上,分别以单个牙齿承力,牙列承力前牵引和中位骨骼前牵引,比较分析其生物力学变化。结果以梨状孔底承力的中位前牵引,矢向位移面中上1/2前移比牙齿或牙列承力的前牵引多,面中下1/2位移相对较少,垂直向及侧向位移值均小于牙齿或牙列承力的前牵引。中位前牵引颅面复合体,鼻根区压应力减少明显。结论与传统的牙体或牙列承力的前牵引比较,上颌中位前牵引可整体前移上颌,从而减少上颌的逆向旋转及硬腭前部压缩现象。

Objective The purpose of this study was to investigate the biomechanical changes of midface skeleton protraction at its medium position in the craniofacial complex, using the three-dimensional finite element method（FEM）. Methods A three-dimensional FEM model was developed from the CT scan images by the technologies of three-dimensional reconstruction, image processing and meshing. The protraction forces were applied to the following locations： the first molar, full maxillary arch, and the floor of apertura pirifonns. Biomechanical changes from different position protraction were investigated by means of finite element analyses. Results Protraction forces at the level of the floor of apertura piriforms produced a more forward movement of the upper maxilla in sagittal direction. Vertical and lateral displacements were less than those in loading with teeth or denture. Compressive stress on the radix nasi decreased obviously in midface skeleton protraction at its medium position. Conclusions Compared with traditional orthopedic protraction, midface skeleton protraction at its medium position could advance maxilla en bloc, decrease the counterclockwise rotation of the maxilla, and reduce the constriction of the anterior part of the palate.