Purpose: To investigate the biomechanical expression of different shapes of attachments on the maxillary anterior teeth during the lingual tooth movement process using clear aligners, providing new insights for orthodontists to improve the clinical design.
Methods: In this study, CBCT data were simulated using the three-dimensional finite element technique. Attachments of various shapes, including no attachment(A1), rectangular attachment(A2), wedge-shaped attachment(A3), and curved arc attachment(A4), were designed on the lateral incisors. Ansys software was employed to calculate the three-dimensional changes in the lateral incisors, dental arch, and clear aligners and the distribution of equivalent stress on the periodontal ligament(von Mises) under the same load conditions.
Results: The coronal displacement of the lateral incisors showed the following variations: A1＞A4＞A3＞A2. The sagittal displacement exhibited the following variations: A3＞A4＞A1＞A2. The vertical elongation demonstrated the following variations: A4＞A3＞ A1＞A2. The overall displacement of each dental arch displayed an arch-shaped trend. Different regions of the clear aligners exhibited variations in deformation. The von Mises distribution of the periodontal ligament in A1 and A2 group showed similarities, while A3 group exhibited stress concentration only in the lingual area of the root's one-third region. Group A4 experienced significantly higher stress in the cervical region compared to A1 and A2 group.
Conclusions: Rectangular attachments and curved arc attachments possess advantages in coronal control, with rectangular attachments exhibiting the best control effect in vertical control. The area of attachment force and actual displacement efficiency do not have an absolute correlation, as the shape of the force-bearing surface can significantly affect its specific biomechanical expression.