The 3-D Finite Element Analysis Of The Implement Of Tip-Edge Orthodontics

The research is to establish the three-dimensional finite element analysis models of the maxillary anterior teeth with Tip-Edge brackets, then give the maxillary right central incisor a torque in order to study the stress and strain of alveolar bone, roots and periodontal ligament (PDL) of the maxillary right central incisor and adjacent teeth. As a base, it is helpful for clinical practice of Tip-Edge Orthodontics.Objective:1 To establish three-dimensional finite element analysis models of maxilla, maxillary anterior teeth and their periodontal tissues with Tip-Edge brackets for biomechanics analysis.2 To study the stress and strain of roots and PDL of the maxillary right central incisor when it was given a torque.3 To study the stress and strain of roots and PDL of the adjacent teeth during the whole movement.4 To study the stress and strain of the alveolar bone during the whole movement. Method: 1 After maxilla and maxillary anterior teeth reconstructed by Mimics, a 3-D model was built in Geomagic studio, which is a reverse engineering software. The 3-D models of Tip-Edge brackets and rectangular archwire were established by UG. Then all the models were imported in ANSYS to be meshed.2 According to clinical practice of Tip-Edge Orthodontics, a force, that its magnitude was 0.5N, was imposed on the maxillary right central incisor to simulate the impact of side-winder spring. When archwire came into contact with the Tip-Edge bracket, a couple whose magnitude was 10N·mm was imposed on the maxillary right central incisor in order to produce a labial crown torque. The whole movement simulated implement of torque in clinical practice. To analyze the stress and strain of alveolar bone, roots and PDL of the maxillary right central incisor and adjacent teeth at three time points: beginning of torque, 6°torque angle and finishing of torque.Results:1 The 3-D FEM (finite element) models of maxilla,maxillary anterior teeth and their periodontal tissues with Tip-Edge brackets was established successfully, which contained 1362593 nodes and 977040 elements. The Tip-Edge brackets had 44410 nodes and 43210 elements, and the rectangular archwire had 6622 nodes and 8417 elements, and the maxilla had 231391 nodes and 196984 elements, and the teeth had 776371 nodes and 627281 elements, the PDL had 85594 nodes and 101489 elements.2 Tip-Edge appliance in the implementation process of the torque did not produce torque on the adjacent teeth; during torque the periodontal tissue's stress concentration area was basically the same, was located in the labial of tooth neck and palatal side apical part; maximum stress increases with the torque angle showed a stable trend, while the periodontal ligament of the maximum equivalent strain increases with the torque angle showed a decreasing trend, root and alveolar bone to stabilize the maximum equivalent strain .Conclusions:1 The 3-D FEM model had high biological similarity and reasonable mesh. It could provide a foundation for different biomechanical analyses about Tip-Edge orthodontic technique.2 In clinical practice, in order to protect the periodontal tissue and play Tip-Edge appliance really high efficiency, light force must be used.3 In the treatment of late, especially the impact of torque on the relatively root, in order to avoid root resorption, the proposed pay close attention to the root situation, once the symptoms of root resorption, the treatment should be terminated immediately.