Rucker Brian K, Kusy Robert P
Department of Biomedical Engineering, University of North Carolina, Chapel Hill, 27599, USA.
Am J Orthod Dentofacial Orthop. 2002 Nov;122(5):528-41. doi: 10.1067/mod.2002.127292.
The strength, stiffness, and range of single-stranded stainless steel (SS) and superelastic nickel-titanium (NiTi) archwires were compared with those of alternative leveling products, including nylon-coated and multistranded wires. Wire cross-sections were photographed after being potted in polymer, ground, and polished. Because the rectangular wires had rounded or beveled corners, gravimetric measurements and specific gravity calculations quantified the actual polygonal cross-sectional areas versus the ideal rectangular cross-sectional areas. Beveling reduced the cross-sectional areas by 7% to 8%; this decreased the wire stiffnesses by 15% to 19%. Using a testing machine, we measured the yield strengths, the elastic limits, and the ultimate tensile strengths in tension, and wire stiffnesses in 3-point bending. From cyclic loading tests, the elastic limits of the superelastic NiTi wires were approximately 90% and 45% of their ultimate tensile strengths for the round and rectangular wires, respectively. Using the measurements of the mechanical properties and geometric parameters of each wire, we computed the elastic property ratios (EPRs) versus a 16-mil (0.41 mm) NiTi wire. The single-stranded NiTi wires outperformed the alternative wires, whose EPRs varied from 0.05 to 0.32 for strength, from 0.11 to 1.55 for stiffness, and from 0.10 to 0.80 for range. Based on the current study and a review of the orthodontic literature, few superelastic wires are activated sufficiently in vivo to exhibit superelastic behavior. Therefore, the EPR data reported here for superelastic wires truly represent their performance in most clinical situations.
将单股不锈钢（SS）和超弹性镍钛（NiTi）弓丝的强度、刚度和范围与其他整平产品（包括尼龙涂层丝和多股丝）进行了比较。将丝材浇铸在聚合物中，进行研磨和抛光后，对其横截面进行拍照。由于矩形丝的角是圆形或斜角的，通过重量测量和比重计算来量化实际多边形横截面积与理想矩形横截面积。斜角使横截面积减少了7%至8%；这使丝材的刚度降低了15%至19%。使用测试机，我们测量了拉伸时的屈服强度、弹性极限和极限抗拉强度，以及三点弯曲时的丝材刚度。通过循环加载试验，超弹性NiTi丝的弹性极限对于圆形丝和矩形丝分别约为其极限抗拉强度的90%和45%。利用每根丝材的力学性能和几何参数测量值，我们计算了相对于一根16密耳（0.41毫米）NiTi丝的弹性性能比（EPR）。单股NiTi丝的性能优于其他丝材，其他丝材的EPR强度在0.05至0.32之间，刚度在0.11至1.55之间，范围在0.10至0.80之间。基于当前研究和对正畸文献的回顾，很少有超弹性丝在体内被充分激活以表现出超弹性行为。因此，这里报告的超弹性丝的EPR数据真实地代表了它们在大多数临床情况下的性能。
