隐形矫治配合Ⅱ类牵引时不同硬度矫治器对尖牙稳定及矫治器贴合的影响

Effect of Different Hardness Appliances on the Stability of the Canine and the Fit of the Appliance During Invisible Appliance Combined with Class Ⅱ Elastics

目的研究不同硬度(弹性模量)的隐形矫治器在上颌尖牙仅受Ⅱ类牵引力时,对尖牙位置稳定及尖牙区矫治器贴合的影响,为隐形矫治器材料的选择提供理论依据。方法利用有限元法分别建立弹性模量为415.6 MPa(1号矫治器)、528.0 MPa(2号矫治器)、816.31 MPa(3号矫治器)的隐形矫治器模型,模拟上颌尖牙受1 N的力,对施力瞬间各工况下尖牙位移、尖牙牙周膜应力以及尖牙与矫治器各个定位点的相对位移进行对比分析。结果不同硬度矫治器作用下尖牙瞬间位移方向一致,均偏向远中、舌侧、[牙合]方。1号矫治器、2号矫治器、3号矫治器尖牙位移量分别为31.46、26.10、22.38μm。随着材料硬度的增大,牙周膜Von-Mises应力值分别为15.97、12.08、9.61 kPa,尖牙与矫治器[牙合]方观测点的相对位移量分别为7.30、4.76、4.32μm,龈方观测点的相对位移分别为6.12、5.30、4.01μm。结论对上颌尖牙仅施加Ⅱ类牵引力时,与弹性模量为415.6 MPa与528.0 MPa的隐形矫治器比较,硬度(816.31 MPa)最大的矫治器更有助于维持尖牙的稳定性及尖牙区矫治器贴合。

Objective To study the effect of invisible appliance of different hardness(elastic modulus)on the stability of the canine position and the fit of the appliance in the canine area when the maxillary canine was only subjected to class Ⅱ elastics,as to provide theoretical basis for plastic aligner equipment material selection.Methods The finite element method was used to establish models of invisible appliance with elastic modulus of 415.6 MPa(No.1 appliance),528.0 MPa(No.2 appliance),and 816.31 MPa(No.3 appliance).The maxillary canines were subjected to a force of 1 N.The canine displacement,the canine periodontal ligament stress,and the relative displacement of the canine and the appliance’s positioning points under working conditions were compared and analyzed.Results The direction of the instantaneous displacement of the canine under the action of appliances of different hardness was the same,and they were all biased towards the distal,lingual and occlusal sides.The displacements of the canine of No.1 appliance,No.2 appliance and No.3 appliance were 31.46,26.10 and 22.38μm,respectively.As the hardness of the material increased,the Von-Mises stress values of the periodontal ligament were 15.97,12.08 and 9.61 kPa,and the relative displacements of the canine and appliance occlusal observation points were 7.30,4.76 and 4.32μm,respectively.The relative displacements of gingival observation point were 6.12,5.30 and 4.01μm,respectively.Conclusion When only Class Ⅱ elastics is applied to the maxillary canine,compared with invisible appliances with elastic modulus of 415.6 MPa and 528.0 MPa,the appliance with the largest hardness(816.31 MPa)is more helpful to maintain the stability of the canine and the fit of the appliance in the canine area.