Biomechanical effects of attachment designs in maxillary first molar mesialization with clear aligners: A finite element study

Transparent plates are subject to biomechanical limitations, especially in complex tooth movements such as mesialization of molar teeth, despite the use of attachments. In such cases, it may be difficult to effectively perform the desired movements. Finite element analysis (FEA) is an effective method for analyzing these movements and enables the determination of the most suitable attachment designs in terms of force transmission.The aim of this study is to compare the displacement patterns and stress distributions during maxillary molar mesialization using three-dimensional finite element analysis (FEA) with four different attachment designs. A maxilla model based on magnetic resonance imaging (MRI) was created, including the periodontal ligament (PDL), alveolar bone, and a transparent plate with a thickness of 0.75 mm. Five different scenarios were simulated in the study: no attachment (Model-I), rectangular vertical attachment (Model-II), rectangular horizontal attachment (Model-III), optimized double semi-ellipsoidal attachment (Model-IV), and yin-yang attachment (Model-V). In each model, a 0.5 mm mesial displacement was applied, and the resulting deformation and stress distribution were analyzed using the ANSYS Workbench program. Model-IV (optimized attachment) provided the least molar tipping (0.319 mm total displacement) and the best mesiodistal control. Model-I, which did not use attachments, showed the highest tipping (0.376 mm). The Model-V with yin-yang attachments reduced buccal displacement by 92% compared to Model-I. Horizontal rectangular attachments were found to be effective, especially in minimizing rotational movement. Optimized double semi-ellipsoidal attachments provide superior movement control in molar mesialization. Yin-yang designs offer advantages in enhancing buccal-lingual stability. These findings demonstrate that attachment geometry plays a critical role in determining the effectiveness of orthodontic treatment with clear aligners.