Effects of Attachment Shapes and Positions on Maxillary Molar Derotation in Clear Aligner Therapy: A Finite Element Analysis

Aim With advancements in science and technology, clear aligners have become a viable alternative to traditional braces for many orthodontic treatments. In clear aligner therapy, the use of attachments on specific tooth surfaces is often essential to achieve complex dental movements such as rotation. This study aimed to evaluate the effects of various attachment shapes and positions on the derotation of the maxillary first molar using the Finite Element Method (FEM). Materials and Methods Three-dimensional models of the maxillary bone, teeth (including a mesiopalatally rotated right first molar), periodontal ligament (PDL), and clear aligner were generated from CBCT images of a patient. The models were categorized into six groups based on different attachment shapes and positions. A displacement of 0.2 mm was applied to the clear aligner on the maxillary first molar, and tooth displacement, aligner displacement, and Von Mises stress in the PDL were analyzed using FEM software. Results The highest tooth displacement (0.0130157 mm) and Von Mises stress in the PDL (0.0212361 MPa) were observed in the model featuring a horizontal beveled rectangular attachment on the distobuccal surface of the maxillary first molar. The lowest aligner displacement (0.018105 mm) was found in the model with the same attachment on the mesiobuccal surface. Overall, models with horizontal beveled rectangular attachments exhibited the greatest tooth movement and stress levels in the PDL. Conclusion Compared to models without attachments, those with attachments demonstrated greater tooth displacement. Among the tested designs, the horizontal beveled rectangular attachment on the distobuccal surface of the maxillary first molar showed the highest efficiency in correcting rotation and may be recommended for clinical use.