Postgraduate School of Orthodontics, University of Ferrara, Via Borsari, 46, 44121, Ferrara, Italy.
Department of Engineering, University of Ferrara, Ferrara, Italy.
Prog Orthod. 2019 Jan 7;20(1):1. doi: 10.1186/s40510-018-0251-z.
The aim of this study is to investigate and compare the characteristics of as received and retrieved NiTi archwires at a constant temperature by plotting their load/deflection graphs and quantifying three parameters describing the discharge plateau phase.
Two hundred four NiTi archwires, traditional and heat-activated, of various cross sections, were obtained from 5 different manufacturers. Specimens prepared from the selected wires were subjected to a three-point bending test where 92 were retrieved through an in vivo retrieval protocol (crowding group C1 and group C2), 56 went through an in vitro retrieval protocol, and 56 were as received. The in vitro retrieval protocol was performed by a gear motor connected to a stainless steel support that performed fatigue cycles to the bent wires in artificial saliva. The load/deflection graphs of as received and retrieved wires were described through three parameters and the results were analyzed with classification and regression trees (CART) and analysis of variance (ANOVA).
Statistically significant differences between as received and retrieved wires were found only for the parameter plateau slope which represents the constancy of force expressed by the wire.
The aging of NiTi archwires influences the force constancy expressed. The behavior of the wires changes depending on the size, brand, and type of retrieval protocol. In terms of performance, the poorest is represented by all wires retrieved in vitro and in vivo group C2 (moderate to severe crowding).
本研究旨在通过绘制负载/变形图并量化描述卸载平台阶段的三个参数来比较和研究在恒定温度下接收和回收的 NiTi 弓丝的特性。
从 5 家不同制造商处获得了 204 根传统和热激活的不同横截面的 NiTi 弓丝。从选定的弓丝制备的样本进行三点弯曲测试，其中 92 根通过体内回收协议（拥挤组 C1 和 C2）回收，56 根通过体外回收协议回收，56 根为接收状态。体外回收协议由与不锈钢支架相连的齿轮电机执行，对弯曲的弓丝在人工唾液中进行疲劳循环。通过三个参数描述接收和回收弓丝的负载/变形图，并使用分类和回归树 (CART) 和方差分析 (ANOVA) 对结果进行分析。
仅发现接收和回收弓丝之间在平台斜率参数上存在统计学显著差异，该参数代表弓丝所表达的力的恒定性。
NiTi 弓丝的老化会影响其表达的力的恒定性。弓丝的行为会根据尺寸、品牌和回收协议的类型而变化。就性能而言，所有体外和体内组 C2 （中度至重度拥挤）回收的弓丝表现最差。
