Three-dimensional finite element analysis of the optimal attachment position for clear aligners of the lower canine

Objective To compare the effects of different attachments and their placement positions on the correction movements of intrusion, extrusion, rotation, and torque in the right mandibular canine using the three-dimensional finite element method. Methods A female patient treated in the Department of Orthodontics at the Urumqi City Stomatology Hospital in 2022 was chosen as the model subject. A three-dimensional finite element model was constructed to simulate various conditions of the right mandibular canine undergoing intrusion, extrusion, rotation, and torque movements with 21 different types of attachments placed at various positions. A load of 11.821 N was applied at the corresponding positions of the aligner attachments, and simulations were performed in Abaqus 6.14 software to collect stress and displacement distribution maps along with maximum stress and displacement values. Results In the simulation of orthodontic treatment for extrusion, the highest periodontal ligament Von Mises stress(PVMS)values and canine displacement occurred when the attachment was located at the upper region of buccal incisal. For the intrusion group, it was observed that PVMS values and contact stress of the alveolar bone, canine, aligner, and attachment gradually increased as the attachment position moved from the upper region to the lower region. In the torque simulation, the canine PVMS was the highest when the attachment was on the buccalupper region. In the rotation group, canine displacement incrementally increased as the attachment moved from the upper region to the lower region, regardless of whether it was on the lingual or buccal side. Conclusion ①For the extrusion, intrusion, and torque movements of the lower canine, the most suitable attachment positions are on the middle lingual side and middle buccal sideof the canine; for the rotational movement of the lower canine, the attachments should be placed on the middle buccal side, and lower lingual side. ②The lingual position of the tooth attachment greatly influences tooth movement and the distribution of stress.