Primozic Jasmina, Hren Miha, Mezeg Uros, Legat Andraz
Faculty of Medicine, University of Ljubljana, SI-1000 Ljubljana, Slovenia.
Slovenian National Building and Civil Engineering Institute, SI-1000 Ljubljana, Slovenia.
Materials (Basel). 2022 Feb 15;15(4):1427. doi: 10.3390/ma15041427.
To evaluate the effect of long-term in-vivo aging on orthodontic archwires, we aimed to assess the triboelectrochemical and mechanical characteristics of as-received and in-vivo aged nickel-titanium (NiTi) and stainless-steel (SS) orthodontic archwires. Four consecutive tribocorrosion cycles on six NiTi and six SS archwires, as-received and in-vivo aged, were performed on a reciprocal tribometer. Electrochemical noise and friction coefficient measurements, three-dimensional surface profiling, and hardness measurements were performed. Repassivation times of as-received archwires were longer than of the in-vivo aged; however, were shorter for NiTi. Friction coefficients were higher for NiTi than for SS archwires. Sudden major current drops concomitant with inverse potential shifts and friction coefficients' fluctuations, were seen for as-received (last cycle) and in-vivo aged (last three cycles) NiTi archwires. More pronounced tribocorrosion damage was observed on in-vivo aged NiTi than on other archwires. Hardness was generally higher inside the wear track of archwires. Long-term in-vivo exposure decreases the corrosion susceptibility of archwires, more evidently for the NiTi ones. Sudden major fluctuations in electrochemical current, potential, and friction coefficient detected for NiTi archwires, might be related to localized residual parts of the oxide layer persisting due to increased surface roughness or to phase transformations of the alloy's crystal structure.
为了评估长期体内老化对正畸弓丝的影响，我们旨在评估接收状态和体内老化的镍钛（NiTi）及不锈钢（SS）正畸弓丝的摩擦电化学和机械特性。在往复摩擦磨损试验机上，对6根接收状态和6根体内老化的NiTi弓丝以及6根接收状态和6根体内老化的SS弓丝进行了连续4次摩擦腐蚀循环试验。进行了电化学噪声和摩擦系数测量、三维表面轮廓分析以及硬度测量。接收状态弓丝的再钝化时间比体内老化弓丝的长；然而，NiTi弓丝的再钝化时间较短。NiTi弓丝的摩擦系数高于SS弓丝。在接收状态（最后一个循环）和体内老化（最后三个循环）的NiTi弓丝中，观察到伴随反向电位变化和摩擦系数波动的突然大幅电流下降。与其他弓丝相比，在体内老化的NiTi弓丝上观察到更明显的摩擦腐蚀损伤。弓丝磨损轨迹内部的硬度通常更高。长期体内暴露会降低弓丝的腐蚀敏感性，对于NiTi弓丝更为明显。在NiTi弓丝中检测到的电化学电流、电位和摩擦系数的突然大幅波动，可能与由于表面粗糙度增加而持续存在的氧化层局部残留部分或合金晶体结构的相变有关。
