多种镍钛弓丝应力应变的研究

The load/deflection characteristics of NITI orthodontic archwires.

目的本研究探讨多种 NITI 弓丝在口腔温度下的应力应变,指导临床合理选择弓丝。方法选取9个厂家20年种镍钛弓丝,其中圆丝12种,方丝8种;超弹性弓丝9种,热激活弓丝11种。使用材料力学实验机在35℃±2范围内,进行三点弯曲实验,弓丝跨度为10mm,加载及卸载速度为2mm/s。实验机自动绘制应力应变曲线,进行定性与定量分析。结果弓丝在形变超过3mm 后加载应力下降而卸载力值并无明显变化;相同尺寸情况下,热激活镍钛弓丝与超弹性 NITI 丝相比,并不一会产生更小的卸载力值。本研究中 Dentaurum 的 Tensic 16毫英寸弓丝产生最小的卸载应力(37.03g),其次为非凡的14毫英寸马氏体弓丝(46.33g)。方形 NITI 弓丝较圆丝有较大的滞后。结论镍钛弓丝可以在临床中产生很大的形变同时矫治力变化不大;弓丝的尺寸并不能成为临床弓丝选择的唯一依据,热激活 NITI 弓丝并不一定产生更小的矫治力,但可以提供更方便的临床操作。方 NITI 弓丝在初期纠正旋转拥挤后可以尽早使用。弓丝的选择需要参考其材料力学特性。

Objective The load and deflecting characteristics of 20 kinds of archwire at oral temperature was investingated, to help orthodontist choose NITI archwire in clinic. Methods 20 kinds of NITI archwire from 9 companies were selected, with 12 pieces of round wires and 8 pieces of rectangular wires, 9 pieces of superelastic wire and 11 pieces of thermodynamic archwires. Three point bending test was conducted by material testing machine with a span of 10mm, the deflect rate is 2mm/s. Temperature was controlled at 35 ± 2 ℃ by thermostatic box. Results The loading stress was becoming lower when the deflection was above 3ram, while the unloading stress is not significantly affected. Thermodynamic wire does not produce smaller stress than superelastic wire with same dimension. Tensic 16 mil archwire produce the smallest stress（37. 03g） in this study, the second one was Forestadent 14 mil Martensitic NITI wire. Rectanguar NITI wires has greater hyterisis than round ones. Conclusions NITI archwire does not produce large stress under big deflection. The dimension of archwire is not the only property used to choose archwire. Thermodynamic arch wire does not produce small stresss. Rectangular wire can be used early after the rotation is corrected.