Deflection and Flexural Strength Effects on the Roughness of Aesthetic-Coated Orthodontic Wires

Abstract The aim was to evaluate the flexural strength and the effects of deflection on the surface roughness of esthetic orthodontic wires. The sample consisted of 70 archwire 0.014-inch: polytetrafluorethylene (PTFE)-coated Nickel-Titanium (Niti) archwires (Titanol Cosmetic-TC, Flexy Super Elastic Esthetic-FSE, esthetic Nickel Titanium Wire-ANT); epoxy resin-coated Niti archwires (Spectra-S, Niticosmetic-TEC); gold and rhodium coated Niti (Sentalloy-STC) and a control group (superelastic Niti (Nitinol-NS). The initial roughness was evaluated with a rugosimeter. After that, the wires were submitted to flexural test in an universal testing machine. Each wire was deflected up to 2 mm at a speed of 1 mm/min. After flexural test, the roughness of the wires was evaluted on the same surface as that used for the initial evaluation. The data of roughness and flexural strength were analyzed by one-way ANOVA and Tukey’s test (a=0.05). Student t-test compared roughness before and after deflection (a =0.05). The roughness of S and ANT (epoxy resin and PTFE-coated wires, respectively), before and after deflection, was significantly higher than the other groups (p<0.05). Wire deflection significantly increased the roughness of the wires S and STC (p<0.05). The flexural strength of groups FSE and NS (PTFE and uncoated) was higher compared with that of the other groups (p<0.05). We concluded that the roughness and flexural strength of the orthodontic wires does not depend on the type of the esthetic coating, but it is influenced by the method of application of this coating. The deflection can increase the roughness of the esthetic orthodontic wires.

摘要：本研究旨在评估美观型正畸弓丝的抗弯强度，以及挠曲对其表面粗糙度的影响。本次研究样本包含70根0.014英寸的弓丝：分别为聚四氟乙烯（polytetrafluorethylene, PTFE）涂层镍钛（Nickel-Titanium, NiTi）弓丝（包括Titanol Cosmetic-TC、Flexy Super Elastic Esthetic-FSE及美观型镍钛丝ANT）；环氧树脂涂层镍钛弓丝（Spectra-S、Niticosmetic-TEC）；金及铑涂层镍钛弓丝（Sentalloy-STC），以及对照组（超弹性镍钛丝Nitinol-NS）。首先使用粗糙度仪（rugosimeter）对弓丝的初始表面粗糙度进行检测，随后将弓丝置于万能试验机（universal testing machine）中开展抗弯测试：以1mm/min的加载速率将每根弓丝挠曲至2mm。抗弯测试完成后，在与初始粗糙度检测相同的弓丝表面上再次开展粗糙度检测。本研究采用单因素方差分析（one-way ANOVA）与Tukey检验（显著性水平α=0.05）对粗糙度及抗弯强度数据进行统计分析，采用Student t检验对比挠曲前后的弓丝粗糙度（显著性水平α=0.05）。结果显示，环氧树脂涂层组S与聚四氟乙烯涂层组ANT的弓丝，无论挠曲前后，其表面粗糙度均显著高于其余各组（p<0.05）；弓丝挠曲显著提升了S组与STC组弓丝的表面粗糙度（p<0.05）；FSE组与NS组（聚四氟乙烯涂层组及未涂层超弹性镍钛弓丝组）的抗弯强度显著高于其余各组（p<0.05）。本研究得出结论：美观型正畸弓丝的粗糙度与抗弯强度并不取决于美观涂层的类型，而是受该涂层的施涂方式影响；挠曲操作可提升美观型正畸弓丝的表面粗糙度。