Abstract:

Objective To investigate the mechanical effects of various height combinations of canine long-arm hooks and micro-implant anchorage on the retraction of maxillary anterior teeth in clear aligner treatment. It focuses on analyzing the stress distribution within the periodontal ligament and the movement tendencies of the anterior teeth, providing scientific evidence for optimizing orthodontic treatment strategies. Methods Three-dimensional finite element models were developed using CBCT scan data of patients and software including Mimics, Geomagic Studio, and Hypermesh. The models incorporated 16 different configurations of canine long-arm hooks(4, 6, 8, 10 mm) and micro-implant anchorage(6, 8, 10, 12 mm). Elastic traction forces of 3/16, 3.5 oz were applied to these models. Simulations assessed how these variables influenced periodontal ligament stress distribution and the movement patterns of the maxillary anterior teeth. Results Stress during anterior teeth retraction was predominantly concentrated in the cervical and apex regions of the periodontal ligament, where it interfaced with the alveolar bone, indicating significant local concentration. Increasing the height of micro-implant anchorage and traction hooks markedly reduced positional changes in both the crown and apex. Specifically, when hooks exceeded 8 mm and anchorage heights surpassed 10 mm, canine movement became more uniform, preventing extrusion and minimizing the deepening of the overbite. Additionally, combinations of high traction hooks and high micro-implant anchorage promoted more uniform tooth movement, reducing unnecessary tipping and rotation. Conclusion In the retraction of maxillary anterior teeth with clear aligners, using high-position micro-implant anchorage and high-position traction hooks significantly enhances torque control of anterior teeth and effectively prevents deepening of the overbite.

Key words: three-dimensional finite element analysis, micro-implant anchorage, clear aligner