Effects of Attachment Placement on Palatal Root Torque Control of Maxillary Incisors with Clear Aligners: A Finite Element Study.

Abstract

<b>Objective:</b> The objective of this study is to evaluate the biomechanical effects of different attachment placement strategies using rectangular attachments on palatal root torque control of maxillary central and lateral incisors with clear aligners. <b>Methods:</b> Three-dimensional finite element analysis was performed to simulate simultaneous 1° palatal root torque of maxillary central and lateral incisors. Six attachment configurations were evaluated: no attachment (control), canine-only, both incisors, central incisor-only, lateral incisor-only, and all anterior teeth. Three-dimensional tooth displacement and torque expression were analyzed across 200 iterative simulations. Model validation was confirmed through mesh convergence analysis and comparison with published studies. <b>Results:</b> Only the control and canine-only groups simultaneously achieved the appropriate torque direction for both incisors. Attachments on central incisors produced reverse torque, with the central incisor-only group showing the most severe magnitude, while the control and canine-only groups achieved expected directions, validating model reliability. Lateral incisors exhibited different responses, including reverse torque in the lateral incisor-only group. The canine-only attachment demonstrated the most balanced torque expression. Increasing anterior attachments was associated with greater extrusion and canine displacement. <b>Conclusions:</b> Attachment placement using rectangular attachments significantly influenced torque expression during palatal root torque. Central and lateral incisors responded differently to attachments, and certain configurations produced reverse torque. For small torque movements (1-2°), a "less is more" approach using rectangular canine attachments for anchorage proved most effective, suggesting that anchorage may be more critical than incisor attachments for anterior torque control.