The Three-dimensional Finite Element Analysis Of Corrective Mechanism Of Reverse-curve Arch Wire

Objective: With the method of 3-D finite element analysis, the study was to analyze the perpendicular force on each tooth as well as the Von Mises distribution on tooth roots, periodontal ligaments and alveolar bone that were produced by the reverse-curve arch wires of various angles and depths. Methods: 3-D finite element models of lower teeth, periodontal ligaments and alveolar bone as well as the 0.018×0.025 inch stainless steel reverse-curve arch wires with different angles and depths were developed with the ANSYS finite element software. The displacements of deformation of the reverse-curve arch wires were established on the models. The perpendicular force on each tooth and the Von Mises distribution on tooth roots, periodontal ligaments and alveolar bone were calculated. Results: The depth and angle of the reverse-curve arch wires produced obvious effect on the force exerted to teeth . They could alter both the strength and the direction of the force. The force was mainly loaded on the canines, the bicuspids as well as the molars, but less loaded on the incisors. Affected by the reverse-curve arch wires, the incisors were brought intrusively and the molars were brought intrusively and distal upright; however, the canines and the bicuspids, in the perpendicular direction, moved along with the transformation of the angle and depth of the reverse-curve arch wires. When the angle of reverse-curve arch wires was fixed, the intrusive force on the incisors and molars was increased along with the increase of depth of the reverse-curve arch wires. Perpendicularly, the canines underwent a process from extrusion to intrusion, while the bicuspids were from intrusion to extrusion. When the depth of reverse-curve arch wires was fixed, the intrusive force on the incisors and molars was increased along with the increase of angle of the reverse-curve arch wires. The canines underwent a process from intrusion to extrusion. Affected by the reverse-curve arch wires,the highest Von Mises was observed on the root surface,the intermediate on the alveolar bone and the lowest in the periodontal ligaments .The Von Mises on tooth roots , periodontal ligaments and alveolar bones was increased along with the increase of angle and depth of the reverse-curve arch wires. The concentration of Von Mises was produced at the cervix and apex of the root surface, alveolar bone and periodontal ligaments.Conclusion: The variation of the angle and depth of the reverse-curve arch wires produced evident effect on the force exerted to teeth, as well as the Von Mises on tooth roots, periodontal ligaments and alveolar bone. As it was revealed from the regular patterns of the force on each teeth and Von Mises distribution on tooth roots , periodontal ligaments and alveolar bone by 0.018×0.025 inch stainless steel reverse-curve arch wires, it is believed that the angles of the reverse-curve arch wires should not go beyond 15°,in addition, the depth of the reverse-curve arch wires should not exceeded 4mm.