Roulias Panagiotis, Mylonopoulou Ioulia-Maria, Sifakakis Iosif, Bourauel Christoph, Eliades Theodore
Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
Department of Oral Technology, School of Dentistry, University Hospital Bonn, Bonn, Germany.
Korean J Orthod. 2023 Mar 25;53(2):89-98. doi: 10.4041/kjod22.183. Epub 2023 Feb 7.
This study aimed to compare the mechanical and thermal properties in the anterior and posterior segments of new and retrieved specimens of a commercially available multizone superelastic nickel-titanium (NiTi) archwire.
The following groups of 0.016 × 0.022-inch Bioforce NiTi archwires were compared: a) anterior and b) posterior segments of new specimens and c) anterior and d) posterior segments of retrieved specimens. Six specimens were evaluated in each group, by three-point bending and bend and free recovery tests. Bending moduli (Eb) were calculated. Furthermore, the new specimens were evaluated with scanning electron microscopy/energy-dispersive X-ray spectrometry. A multiple linear regression model with a random intercept at the wire level was applied for data analysis.
The forces in the posterior segments or new specimens were higher than those recorded in the anterior segments or retrieved specimens, respectively. Accordingly, Eb also varied. Higher austenite start and austenite finish (Af) temperatures were recorded in the anterior segments. No statistically significant differences were found for these temperatures between retrieved and new wires. The mean elemental composition was (weight percentage): Ni, 52.6 ± 0.5; Ti, 47.4 ± 0.5.
The existence of multiple force zones was confirmed in new and retrieved Bioforce archwires. The retrieved archwires demonstrated lower forces during the initial stages of deactivation in three-point bending tests, compared with new specimens. The Af temperature of these archwires may lie higher than the regular intraoral temperature. Even at 2 mm deflections, the forces recorded from these archwires may lie beyond biologically safe limits.
本研究旨在比较市售多区超弹性镍钛（NiTi）弓丝新样本和回收样本前后段的力学性能和热性能。
对以下几组0.016×0.022英寸的Bioforce NiTi弓丝进行比较：a）新样本的前段和b）后段，以及c）回收样本的前段和d）后段。每组评估6个样本，通过三点弯曲、弯曲和自由恢复试验进行。计算弯曲模量（Eb）。此外，对新样本进行扫描电子显微镜/能量色散X射线光谱分析。采用在丝材水平具有随机截距的多元线性回归模型进行数据分析。
后段或新样本中的力分别高于前段或回收样本中记录的力。相应地，Eb也有所不同。前段记录到较高的奥氏体开始温度和奥氏体结束（Af）温度。回收丝材和新丝材在这些温度上未发现统计学上的显著差异。平均元素组成（重量百分比）为：Ni，52.6±0.5；Ti，47.4±0.5。
在新的和回收的Bioforce弓丝中证实存在多个力区。与新样本相比，回收弓丝在三点弯曲试验失活初始阶段表现出较低的力。这些弓丝的Af温度可能高于正常口腔内温度。即使在2毫米挠度下，从这些弓丝记录到的力可能超出生物安全限度。
