无托槽隐形矫治器联合微种植体内收并压低上前牙的三维有限元分析

目的 运用三维有限元技术研究无托槽隐形矫治器联合微种植体内收并且压低上前牙时，使用不同方式的微种植体牵引的治疗效果差异。 方法 获取患者上颌骨及牙体等锥形束CT数据，使用Mimics、Geomagic、Solidworks和Ansys软件建立所需要的三维有限元模型以及无托槽隐形矫治器。根据微种植体的设计不同，分为4个实验组。第1组为空白对照组；第2组在上颌双侧第二前磨牙和第一磨牙之间各植入一颗微种植体，在双侧尖牙牙套上沿内收方向加0.98 N的力；第3组在第2组基础上，在中切牙之间植入一颗微种植体加力0.98 N压低上前牙；第4组在第2组基础上，在双侧中切牙和侧切牙之间各植入一颗微种植体加力0.56 N压低上前牙。对各组进行受力分析，比较不同位点植入微种植体牵引加力时前牙转矩的改变、运动趋势以及应力分布。 结果 4组中所有上颌切牙皆表现出内收和压低的趋势，且伴有不同程度的转矩改变。第3组上颌中切牙及侧切牙在矢状向冠根位移差最小，第4组上颌中切牙及侧切牙压低值最大，第2组最大应力集中值最大。 结论 将微种植体植入上颌中切牙之间进行牵引更利于转矩控制；而植入上颌中切牙与侧切牙之间并联合前牙垂直牵引时更利于单纯压低，在一定程度上避免了“过山车”效应。

Three-dimensional finite element analysis of upper anterior teeth retraction and intrusion using clear aligners and mini-implants

Objective This study aimed to investigate the differences in treatment outcomes of upper anterior teeth retraction and intrusion with clear aligners and different types of elastics on mini-implants via the 3D finite element method. Methods Cone-beam computed tomography (CBCT) was conducted to construct a 3D finite element model of maxillary bone, dentition, and clear aligners using Mimics, Geomagic, Solidworks, and Ansys. Four model groups were developed. Group 1 was the control group. Group 2 implanted a mini-implant between the upper second premolar and the upper first molar with a force of 0.98 N applied to the canine cut along the retracting direction for each side. Group 3 was based on Group 2, which implanted an additional mini-implant between the upper central incisors with a force of 0.98 N applied to the upper anterior teeth cuts. Group 4 was also based on Group 2, which implanted 2 additional mini-implants between the upper central and lateral incisors with a force of 0.56 N applied to the upper anterior teeth cuts for both sides. Anterior teeth torque changes, displacement patterns, and stress distributions were analyzed. Results Among all the experimental groups, the anterior teeth demonstrated intrusion and distal inclination, accompanied with varied degrees of torque loss. In Group 3, the maxillary and lateral incisors had the smallest sagittal coronal displacement. In Group 4, the intrusion values of the maxillary and lateral incisors were the largest among all the experimental groups. The maximum stress concentration in Group 2 was the most significant among all the experimental groups. Conclusion Implanting the mini-implant between the central incisors for traction is conducive to torque control. By contrast, implanting the mini-implants between the central incisors and lateral incisors combined with vertical traction is conducive to simple intrusion, avoiding the “bowing effect” to a certain extent.