교정용 초탄성 니켈-티타늄 와이어의 전기저항 열처리를 이용한 굴곡 부여 후의 하중-변위 특성 변화

Abstract

In order to investigate the effects of bending with direct electric resistance heat treatment (hereafter DERHT) on the load-deflection characteristics of superelastic NiTi alloy orthodontic wires, bilateral step bends were formed using DERHT, and then the step bends were removed by unbending using DERHT. .016" x .022" and .018" x .025" Sentalloy and L&H Titan wires were used in this study. The load-deflection characteristics were examined using three point bending tests. The results were as follows. 1. Bending step bends with DERHT significantly lowered loading and unloading plateau forces of the load-deflection curves of NiTi wires except .016" x .022" Sentalloy. The forces decreased because the step bends increased the amount of wires placed between the wire supports of lower jigs. The patterns of superelastic plateaus of the load-deflection curves were largely unchanged. 2. Unbending the step bends with DERHT caused recovery of loading and unloading plateau forces of load deflection curves to the force levels of unbent NiTi wires (control group), but the loading force of .018" x .025" Sentalloy was significantly less than the control, and the unloading force was significantly greater than the control. 3. Bending step bends and unbending the step bends with DERHT both increased the amount permanent deformation after three point bending test. This indicates that the bending with DERHT decreased the spring-back of NiTi wires. 4. Differential Scaning Calorimetry showed decreased heat flow of peaks, indicating decreased transformation characteristics. In conclusion, bending NiTi wires with DERHT deteriorated spring-back property and transformation characteristics, but largely did not deteriorate the superelastic characteristics of load-deflection curves, When bending NiTi wires, slight overbending is recommended to compensate the decreased spring-back.