The Three-dimensional Finite Element Analysis Of Intruding Lower Incisors By Reverse Curve Arch Wire And Invisible Appliance

Objective:In this study,the digital models of intruing the lower anterior teeth of the rocker arch and the invisible appliance were established,in order to simulate the clinical design characteristics of the rocking chair arch and the invisible appliance.One the hand,the movement trend and stress distribution of the tooth under different appliance and loading modes were observed.One the other hand,the stress of the lower anterior teeth in the same appliance under different loading modes was investigated in order to provide an important reference value for clinical orthodontic treatment.Methods:A young male volunteer was selected to establish a three-dimensional finite element model of the lower dentition-mandible-reverse arch and the lower dentition-mandible-invisible appliance by using Mimics,Abaqus and other software.The reverse curve arch was set to 10 °curvature,2 mm arc depth and 0.018 in diameter stainless steel wire and Ni Ti wire.The displacement and stress distribution of the lower anterior teeth were observed.The displacement and stress distribution of the inferior anterior teeth were observed during the simulated treatment of the lower anterior teeth(first pressing the canines,then adding the lateral incisors and the middle incisors)in the clinical treatment of global and step-by-step depressions.Results:1.In the treatment of fixed reverse curve arch,the displacement trend and stressdistribution of the lower anterior teeth of stainless steel wire and Ni Ti wire were approximately the same.The stress concentration areas were 1/3 on the labial surface,1/3 in the neck,1/3 in the root,and the stress in the right lower incisor with tongue inclination was more concentrated;2.Compared with Ni Ti wire,the stainless steel wire produces a larger displacement and greater stress of lower anterior teeth;3.In invisible correction,the displacement trend and stress distribution of the anterior teeth under stepwise depression and global depression are roughly the same,and the stress concentration area is the root of the tooth,and the stress is relatively uniform;4.Compared with the overall depression,step-by-step depression results in a large amount of displacement and stress of lower anterior teeth.Conclusion:1.For the rocking chair bow with the same parameters,the correction force produced by stainless steel wire,in the use of reverse curve arch wire to open the occlusal should choose appropriate materials in different periods;2.In the treatment of dental crown lip with reverse curve arch,the stress concentration of the crown should be prevented in the process of opening occlusal for the patients with cleft teeth,the clinician should pay attention to the stress of 1/3 on the labial surface of tooth crown;3.Step-by-step reduction is more efficient in stealthy correction.When designing the scheme,the appropriate way of lowering the pressure should be selected;4.For patients with deep overlying,the teeth should be aligned before the reverse curve arch should be used to open the occlusion and level the Spee curve,while the invisiblecorrection can make the teeth aligned and the anterior teeth depressed simultaneously,so as to improve the efficiency of the treatment.