Introduction: The effect of different attachment positions on torque control during the labialization of maxillary lateral incisor with clear aligners was evaluated using the finite element analysis.
Materials and Methods: The anatomical data acquired through cone-beam computed tomography, in conjunction with the designs of 0.625-mm-thick aligners and horizontal attachments, were integrated into the software. Five distinct simulations were generated: (1) an attachment-free group, (2) a labial attachment placed gingivally, (3) a labial attachment placed mid-crown, (4) a labial attachment placed incisally, (5) an attachment placed palatally, and (6) attachments placed both labially and palatally. The evaluation was performed with a default 0.25 mm aligner activation.
Results: The crown of the lateral incisor demonstrated labial movement, while the root exhibited a palatal movement in all models. Group 6 displayed the least crown and root displacement in both axes. Conversely, the attachment-free group showed the most extensive crown movement. The aligner experienced maximum deformation at the incisal edge, progressively decreasing towards the gingival region. The Group 6 demonstrated the least amount of aligner deformation. Von Mises stresses in the periodontal ligament (PDL) were more pronounced at the gingival level, with higher values on the palatal side compared to the labial area.
Conclusions: The utilization of attachments, especially a combination of labial and palatal attachments, facilitates a more precise labialization process, contributing to reduced tipping. Increasing the crown movement of the lateral incisor increases the stress within the PDL, with the most intense stress observed in the palatal region at the gingival level.

Keywords: Clear aligners, Lateral incisor, Torque, Finite element analysis