Corrective Effect On Occlusal Plane Deflection Produced By Asymmetric Rocking Chair Arch Wires:a Three-dimensional Nonlinear Finite Element Analysis

Objective The purpose of this experiment was to explore the biomechanical mechanism of asymmetric rocking chair archwire that effected on the dentition by the method of three-dimensional nonlinear finite element analysis.Methods The CT scanning technology and the three-dimensional nonlinear finite element analysis were employed in this experiment to construct the three-dimensional nonlinear finite element model of the maxilla,upper dentition,periodontal ligament,alveolar bone,and different depths of asymmetric rocking chair archwires.Then,the movement tendency of upper dentition in three dimensions and the changes of periodontal ligament Von Mises stress distribution produced by asymmetric rocking chair archwires(2mm,4mm,6mm)were calculated respectively by ABAQUS software.Results(1)The three-dimensional nonlinear finite element model of maxillary including of asymmetric rocking chair archwire was successfully reconstructed,consisted of 160,514 nodes and 242,878 elements.(2)Among the three kinds of conditions,the trend of dentition displacement in three dimensions were same,the stress on the periodontal ligament was distributed more evenly,no obvious concentration was found.(3)The increasing depth of asymmetric rocking chair archwires had a positive correlation with the displacement of the dentition in three dimensions and the periodontal ligament Von Mises stress.(4)The opposite dimension of displacement generated on the left and right side,and the canines had the maximum displacement.The amount of displacement decreased from the canines to the incisors and the posterior teeth gradually.(5)The crown of right upper anterior teeth had distal movement trends,left anterior teeth had mesial tends,upper right lateral incisor and canine had labial movement trends,left lateral incisor and canine had lingual movement trends,upper right second molar had a extrusion trends.Conclusion(1)The constructed three-dimensional nonlinear finite element model including of asymmetric rocking chair archwire,the maxillary dentition and periodontal support,is of high geometric similarity and in line with clinical practice.(2)The asymmetric rocking chair archwires within 6mm depth make the right and left dentition move in the opposite dimension,produce effective extrusion or intrusion of teeth,and the stress distribution of periodontal ligament is uniform,providing a theoretical basis for clinical treatment of the dental occlusal plane deflection,especially when the anterior teeth axis is wrong.(3)Asymmetric rocking chair archwire can extrude or intrude the teeth effectively,but at the same time,would have some adverse tooth movements,it needs to be controlled.