Development of a hollow orthodontic wire with functionally graded properties

两种不同直径的弯曲特性- o。016和0.018英寸的空心Ti-Ni合金丝；在37°C的温度下，对Ti-Ni和Co-Cr耦合导线进行三点弯曲试验研究。耦合线是将0.010英寸或0.012英寸的CO-Cr线插入空心Ti-Ni线中制成的。首先，在30mm的硝酸盐浴中对空心Ti-Ni丝进行热处理。温度范围：400-650ºC。从载荷-挠曲曲线上看，在40 ~ 600℃的热处理温度下，材料表现出超弹性，塑性变形很小。然而，当温度超过600℃时，发现了一些塑性转变。在450℃的温度下，热处理得到最小的负载水平；在600℃的温度下，热处理得到最大的负载水平。此外，空心型焊丝的载荷水平低于常规Ti-Ni合金焊丝，应力滞后率仅为常规焊丝的65%。综上所述，在正畸治疗的初始阶段，不需要减小弓丝的尺寸，就可以产生轻微的恒定力来移动牙齿。将Co-Cr合金线插入空心超弹性Ti-Ni合金线的耦合线的刚度提高了2倍。在正畸治疗的后期，前牙收拔和咬合提升时，需要使用刚度较高的弓丝。通过使用耦合线，可以在不改变拱丝的情况下增加刚度。目前，一种新的扭矩和弯曲试验装置仍在研制过程中。对钛镍合金空心矩形丝的扭力和弯曲力进行了计算。

Bending characteristics of two different diameters-O.016 and 0.018 inch-of hollow Ti-Ni alloy wire ; which are widely used in the medical field, and a coupling Ti-Ni and Co-Cr wire were investigated by three-point bending test at 37ﾟC.The coupling wire was made by inserting a 0.010 inch or 0.012 inch CO-Cr wire to a hollow Ti-Ni wire.First, heat treatment of the hollow Ti-Ni wires was performed in a nitrate salt bath for 30mm. The temperature ranged between 400-650ﾟC.From a load-deflection curve, in heat treatment temperature of 40O-600ﾟC, the super elastic property was shown and there was very little plastic deformation.However, when the temperature exceeded 600ﾟC, some plastic transformation was found.A smallest load level was obtained by heat treatment at 450ﾟC, and the biggest load level was obtained at 600ﾟC.Moreover, the load level of the hollow-type wire was lower than that of the conventional Ti-Ni alloy wire and the stress hysterisis was shown to be only 65% of the conventional wire.From the above, findings, the light constant force to move teeth can be generated during the initial stage of orthodontic treatment without the need to reduce an archwire size.A coupling wire that inserted Co-Cr alloy wire to a hollow super-elastic Ti-Ni alloy wire was shown to have stiffness of 2 times.In the later stage of orthodontic treatment, when retraction of anterior teeth and bite raising are performed, the archwire which has high stiffness is required. By using the coupling wire, it is possible to increase the stiffness without changing the archwire.At present, a new torquing and bending test device is still in developing process.Evaluation of the force produced by torquing and bending of a hollow Ti-Ni alloy rectangular wire is planned.