West China Journal of Stomatology ›› 2022, Vol. 40 ›› Issue (5): 589-596.doi: 10.7518/hxkq.2022.05.013

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

Shi Zean(), Xia Kai, Luo Liangyu, Zhao Zhihe, Liu Jun.()   

  1. State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases & Dept. of Orthodontics, West China Hospital of Stomatology, Si-chuan University, Chengdu 610041, China
  • Received:2022-04-13 Revised:2022-07-04 Online:2022-10-01 Published:2022-10-17
  • Contact: Liu Jun. E-mail:344655604@qq.com;junliu@scu.edu.cn
  • Supported by:
    The National Natural Science Foundation of China(81870743);Angelalign Scientific Research Fund(SDTS21-4-08);Correspondence: Liu Jun, E-mail: junliu@scu.edu.cn

Abstract:

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.

Key words: three-dimensional finite element, retraction, intrusion of upper anterior teeth, mini-implant, clear aligner

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