细丝弓技术舌侧内收上颌前牙的三维有限元生物力学分析

目的 建立细丝弓舌侧内收上颌前牙的三维有限元模型，研究不同后倾曲力矩对上颌前牙牙周膜静水压以及初始位移的影响。方法 采用CT扫描法建立包含全牙列头颅的三维几何模型，用Solidworks软件生成舌侧托槽和弓丝的三维几何模型，组装并生成细丝弓舌侧内收上颌前牙的三维有限元模型。在三维有限元计算软件ANSYS中计算当颌间牵引力为0.556 N，后倾曲力矩分别为15、30、45、60、75 Nmm时上颌前牙的初始位移以及牙周膜静水压。结果 上颌中切牙、侧切牙以及尖牙的唇舌侧根尖和颈缘共产生4个应力集中区，并产生远中方向的旋转初始位移和相对压入移动；上颌尖牙牙周膜的静水压应力和初始位移均显著大于中切牙和侧切牙；随着后倾曲力矩的增加，上颌中切牙、侧切牙和尖牙垂直向的初始压入位移和牙周膜静水压应力均逐渐增加。结论 采用细丝弓技术舌侧内收上颌前牙的力系是安全可控的，通过改变弓丝后倾曲力矩的值可以有效控制牙齿移动的方式和移动量。

Three-dimensional finite element analysis of maxillary anterior teeth retraction force system in light wire technique

Objective This study aims to construct a three-dimensional finite element model of a maxillary anterior teeth retraction force system in light wire technique and to investigate the difference of hydrostatic pressure and initial displacement of upper anterior teeth under different torque values of tip back bend. Methods A geometric three-dimensional model of the maxillary bone, including all the upper teeth, was achieved via CT scan. To construct the force model system, lingual brackets and wire were constructed by using the Solid works. Brackets software, and wire were assembled to the teeth. ANASYS was used to calculate the hydrostatic pressure and the initial displacement of maxillary anterior teeth under different tip-back bend moments of 15, 30, 45, 60, and 75 Nmm when the class Ⅱ elastic force was 0.556 N. Results Hydrostatic pressure was concentrated in the root apices and cervical margin of upper anterior teeth. Distal tipping and relative intrusive displacement were observed. The hydrostatic pressure and initial displacement of upper canine were greater than in the central and lateral incisors. This hydrostatic pressure and initial intrusive displacement increased with an increase in tip-back bend moment. Conclusion Lingual retraction force system of maxillary anterior teeth in light wire technique can be applied safely and controllably. The type and quantity of teeth movement can be controlled by the alteration of tip-back bend moment.