埋伏倒置上中切牙导萌正畸中旋转中心变化规律的研究

A study on the regularity of center of rotation in the orthodontic treatment of embedded and inverted impact upper central incisor

目的 :了解埋伏倒置阻生上颌中切牙正畸时不同约束状态对旋转中心的影响 ,以及模拟总结正畸前后旋转中心的变化规律。方法 :在已取得的临床资料的基础上 ,实施不同约束条件下旋转中心变化的静力学实验 ,并根据能量法则以计算机有限元SuperDrawⅡ建立翻转移动的计算分析模拟模型进行理论计算 ,以实验手段对临床可行性进行理论验证。结果 :静力学实验结果证明 ,作用力点越接近切缘 ,旋转中心也随之冠向移动 ;有限元实验结果表明 ,牙冠被硬组织包埋得越多 ,旋转中心的切端移位也越多。与初始旋转中心位置相比较 ,在倒置牙冠外露时 ,旋转中心的移动轨迹向量和趋向前上方 ;而在完全埋伏状态下 ,旋转中心的移动轨迹向量和趋向下前方。结论 :正畸作用力方向垂直于牙长轴、作用力点尽可能接近切端以及牙冠被部分牙槽骨包埋 ,尤其是牙冠舌侧牙槽骨的存在 ,是牙根尖得以上移竖直的三个极为重要的条件。提示临床正畸实施得当可避免正畸初期可能发生的旋转中心过快下沉。

Objective: To study the influence of different inhibition conditions for center of rotation (CR) and regularity variations of CR before and after orthodontic treatment of embedded and inverted impact upper central incisor. Methods:Based on clinical findings a computer model of rolling movement was established,then computer finite element Super DrawnⅡwas applied to establish an analytic analogue computing model for calculation. Results:The deeper the crown embedded by hard tissue,the more the edgewise displacement of CR;while the crown was normally exposed,the moving locus tended toward front and upward. Conclusions: Perpendicular orthodontic force to the long axis of tooth forced point that close to the incisal margin and the partly embedded crown by the alveolar bone,especially the bone of lingual aspect are the main factors for the upward moving and erectness of the root apex. Possible subsidence of CR may be avoided by suitable early stage orthodontic treatment.