Evaluation of Tooth Movement and Anchorage Control in Clear Aligners versus Fixed Appliances: A Finite Element...

To evaluate the biomechanical performance of various clear aligner models in comparison to a fixed appliance model, with a focus on tooth movement, stress distribution, and the potential risk of root resorption.

A patient with a maxillary protrusion requiring first premolar extraction was selected for this study. Cone-beam computed tomography and 3D intraoral scanning were used to acquire DICOM data, which were processed into 3D models using Mimics and Geomagic Studio software. Various clear aligner models were designed (Model C1 with a palatal plate and Model C2 with a lingual retractor) and compared to a fixed appliance. Finite element analysis was performed using ABAQUS to simulate force application and analyze the displacement and stress distribution in the periodontal ligament (PDL) during anterior retraction.

Clear aligners exhibited higher sagittal and vertical displacements than fixed appliances, with Model C1 showing a displacement of 0.304961 mm compared to 0.022658 mm for the fixed appliance. The Von Mises stress in the clear aligners (693.733 MPa for Model C1) was significantly lower than that in the fixed appliance (68,668.1 MPa). The stress distribution in the PDL was more evenly spread across the anterior teeth in the clear aligner models, whereas the fixed appliance concentrated the stress in specific areas. Model C1, with the palatal plate, reduced PDL stress and minimized root resorption risk during anterior retraction.

Clear aligners, particularly Model C1 with a palatal plate, offer better control over torque and vertical movement, reducing the risk of root resorption compared to other aligner models. However, clear aligners exhibit greater displacement and PDL stress than fixed appliances, which have better control over posterior retention.