Three-Dimensional Finite Element Analysis on En-Mass Retraction of Maxillary Anterior Teeth With the Clear Aligner Technique

Abstract

Objective This study aimed to investigate the biomechanics effects during en⁃mass retraction of maxillary anterior teeth with the clear aligner (CA) system by three⁃dimensional finite element method, which provides a theoretical basis for orthodontics and CA exploitation. Methods Cone-beam computer tomography (CBCT) was used to scan a normal occlusion adult volunteer who meeting the modeling standards from the Hospital of Stomatology Nankai University. A finite element model including maxillary teeth, periodontal ligament (PDL),alveolar bone and CA was established by Mimics 17.0, Geomagic Studio 12.0, and UG NX software packages. The analysis of material properties of the model set the contact, constraint, and load was performed using the ANSYS Workbench 19.0. CA was employed to simulate the 0.2 mm en⁃mass retraction of anterior teeth and analyze the results. Results The movement of anterior teeth with an inclination of the lingual and distal crown was observed to have the tendency overbite increasing and the posterior teeth tending to incline mesially. The maximum displacement of the central incisor, lateral incisor, canine, second premolar, and first molar were 0.320, 0.290, 0.287, 0.350, and 0.230 mm, respectively. The stress distribution of PDL and alveolar fossa were concentrated in the neck and apical areas of teeth. The stress distribution of PDL on both sides of the extraction space was broad which consistent with the trend of tooth movement. The entire CA had a tendency of dislocation༌displacement and deformation. The CA showed stress concentration at the junction of adjacent teeth and the joints of the posterior teeth were the main stress concentration areas. Conclusion To achieve en⁃mass retraction of maxillary anterior teeth with the CA system, we should pay attention to the orthodontic optimization design, the retraction procedure of torque, intrusion and anchorage protection of posterior teeth, and the CA retention.