van Aken Cornelis A J M, Pallav Prem, Kleverlaan Cornelis J, Kuitert Reinder B, Prahl-Andersen Birte, Feilzer Albert J
Department of Orthodontics, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Amsterdam, The Netherlands.
Am J Orthod Dentofacial Orthop. 2008 Feb;133(2):269-76. doi: 10.1016/j.ajodo.2005.10.030.
The aim of this in-vitro study was to investigate the changes in force delivery of superelastic nickel-titanium archwires used in combination with a self-ligating bracket system after dynamic fatigue-loading in a 3-bracket model under controlled temperature.
Samples of 2 superelastic nickel-titanium (active austenitic) wires, a conventional nickel-titanium wire, and a stainless steel wire, all 0.014-in round, were divided into 2 groups: static deflection and dynamic deflection. The static specimens were under a constant deflection of 3.0 mm. The dynamic specimens had the same constant deflection of 3.0 mm but were subjected to additional repeated deflections of 0.5 mm, applied by a fatigue tester. The test situation simulates a patient's archwire under deflection and subjected to occlusal contact during 1, 100, 10,000, and 100,000 cycles. Fatigue changes were assessed with a 3-point bending test.
Type of wire, loading or unloading, and number of cycles as within-subject factors were statistically significantly different. No statistically significant difference between the test condition, static vs dynamic, was found. The repeated deflections of 0.5 mm were not enough to induce an extra effect of fatigue.
Occlusal forces transferred to a considerably deflected archwire, such as in the large malalignments in the early stages of orthodontic treatment, will have no fatigue effect on the unloading force of that archwire.
本体外研究的目的是调查在可控温度下，在三托槽模型中进行动态疲劳加载后，与自锁托槽系统联合使用的超弹性镍钛弓丝的力传递变化。
将2根超弹性镍钛（活性奥氏体）丝、1根传统镍钛丝和1根不锈钢丝的样本（均为0.014英寸圆形）分为2组：静态挠度组和动态挠度组。静态样本承受3.0毫米的恒定挠度。动态样本具有相同的3.0毫米恒定挠度，但由疲劳测试仪施加额外的0.5毫米重复挠度。测试情况模拟了患者的弓丝在挠度下并在1、100、10000和100000次循环中受到咬合接触。通过三点弯曲试验评估疲劳变化。
作为受试者内因素的弓丝类型、加载或卸载以及循环次数在统计学上有显著差异。未发现测试条件（静态与动态）之间有统计学上的显著差异。0.5毫米的重复挠度不足以产生额外的疲劳效应。
转移到明显挠曲的弓丝上的咬合力，如在正畸治疗早期的严重牙齿排列不齐中，对该弓丝的卸载力不会产生疲劳影响。
