基于牙槽骨生物力学机制预测正畸牙齿移动的定量化研究

Malocclusion is a common oral disease, and tooth position can be corrected by orthodontic treatment. How to predict exactly the movement of tooth and the change of alveolar bone is very significant for the clinical treatment. Under the treatment load, during the initial stage, tooth movement and mechanical deformation can be studied by numerical simulation approaches, such as the Finite Element Method. But during the secondary phase, the analysis and forecasting of periodontal tissues reconstruction have to be combined with alveolar bone modeling and remodeling mechanism. At present, several studies have been executed to reproduce the process of tooth movement. In our previous study, the algorithm for orthodontic tooth movement based on biomechanical mechanisms has been also proposed, and the orthodontic treatment has been simulated. However, this model lacks targeted experimental verification and adequate scientific basis. Accordingly, the objective of this project is to establish animal models to validate the existing simulation results of tooth movement, to research the nonlinear relationship between orthodontic force and tooth movement rate, and to limit the range of bone modeling and remodeling parameters. This study intends to apply orthodontic force on the anterior and posterior teeth of rats, producing translational and rotational movement. Then, the micro-computed tomography and histological staining methods will be used to test regularly rat teeth, alveolar bone and periodontal ligament, and this quantitative analysis will be applied to fit the data and derive the theoretical formulas. In this study, it is hoped to promote the further development of numerical prediction of orthodontic tooth movement.

牙颌畸形为口腔常见病，通过正畸治疗可对牙齿位置进行矫正。如何在术前准确预测牙齿的移动和牙槽骨的反应，对于临床治疗具有重要的指导意义。在矫治载荷作用下，初始阶段的牙齿机械性移动与变形已经可用有限元计算进行分析，而继发阶段的牙周组织改建则必须结合牙槽骨的骨塑建和重建机制进行分析。目前，已经有国内外学者针对正畸牙移动过程进行了模拟预测；申请人在先期研究中也提出相应算法，初步模拟了此正畸过程。但是，现有模型缺乏针对性的实验验证和充分的科学依据。据此，本项目的研究目标就是通过建立动物实验模型，验证现有牙移动模拟结果，深入探究矫治力与牙移动速率的非线性对应关系，对骨塑建和重建算法的调控参数进行限定，从而推动正畸牙移动预测的进一步发展。本研究中拟对大鼠的前后牙分别施加不同大小的矫治力，然后利用微观计算机断层扫描和荧光染色组织学检验的方法定期对牙齿、牙槽骨和牙周膜进行定量分析，拟合数据并推导完善理论方程。

1.项目的背景.国内流行病学调查显示我国牙颌畸形的患病率高达91.20%！通过正畸治疗可对牙齿位置进行重新排列以获得稳定、良好的咬合状态。如果能够在术前准确计算预测和分析评估正畸牙移动，预知牙槽骨对生物力学环境改变的生理学反应，必将能够对提高临床矫正效果具有重要意义！ ..2.主要研究内容.①正畸牙齿移动动物模型Micro-CT扫描及分析.本实验以 SD 大鼠为实验对象，利用齿科镍钛拉簧进行正畸加力，近中移动上颌第一磨牙，建立大鼠正畸牙齿移动模型，观察牙齿移动速度、牙槽骨骨密度及骨量的变化。.②上颌前牙牙齿内收移动的CBCT扫描及测量.本实验采用CBCT对青少年上颌前突拔牙矫治患者进行内收，对牙齿内收前后的牙根长度、牙槽骨厚度、牙槽骨面积、牙槽嵴顶的高度以及牙齿的移动方式等进行测量分析。.③微种植体支抗舌侧内收上前牙力系的三维有限元分析.通过高精度CT扫描以及Mimics三维重建获得高仿真的上颌骨三维几何模型，在FEA软件中生成唇舌侧托槽、弓丝和微种植体的有限元模型。..3.重要结果和关键数据.①从动物实验中大鼠的牙齿移动速率来看， 从加力开始到第 3 天，牙齿移动速率增长较快，从第 3 天到第 28 天，总体速率变化不大，加力后第 3 天皮质骨切开后正畸牙齿移动速率显著大于直接牙齿移动，加力后第 28 天明显小于直接牙齿移动侧。.②从临床研究中牙齿移动速率来看，牙槽骨密度随正畸加力时间、牙槽骨部位及皮质骨切开等因素变化，力学参数变化会对牙槽骨改建产生影响。.③从三维有限元分析研究中来看， 在100g舌向内收力下，上颌中、侧切牙切缘在矢状向上均表现为舌向倾斜初始位移，上颌尖牙切缘表现为远中倾斜移动趋势。..4.科学意义.本课题的研究结果可用于通过有针对性的建立动物实验研究，验证现有基于牙槽骨生物力学机制预测正畸牙齿移动的模拟结果，深入探索矫治力与牙齿移动速率的非线性关系，并对骨组织的塑建和重建调控参数的取值进行限定，能够推动数值预测正畸牙齿移动的进一步发展，最终对临床正畸治疗起到帮助作用和指导意义。