Department of Dental Sciences, Alma Mater Studiorum, University of Bologna, Bologna, Italy.
J Endod. 2011 Jul;37(7):1013-6. doi: 10.1016/j.joen.2011.04.009. Epub 2011 May 28.
The aim of this study was to compare cyclic fatigue resistance of four nickel-titanium rotary systems and to evaluate their surface, fractographic, and matrix morphology.
Four models of endodontic rotary files (EasyShape [Komet/Gebr. Brasseler, Lemgo, Germany], ProTaper [Dentsply Maillefer, Ballaigues, Switzerland], NRT [MANI Inc, Toshigi-Ken, Japan], and AlphaKite [Komet/Gebr. Brasseler]) were subjected to fatigue testing in artificial canals with angle of curvature of 45° and 60° and a radius of curvature of 5 mm until fracture occurred. Nickel-titanium (NiTi) alloy properties were investigated by light microscopy, environmental scanning electron microscopy (ESEM), and energy dispersive x-ray spectrophotometry (EDS). ESEM analysis was conducted on new files to examine surface characteristics and on fractured samples to identify the crack origin and the fractographic features.
Analysis of variance testing revealed significant differences (P < .001) among the groups. NRT files had the highest fatigue resistance followed by AlphaKite, EasyShape, and ProTaper. All the new files presented surface imperfections. Fractographic analysis found the crack initiation to originate at the level of surface irregularities. Optical microscope inspection of the NiTi alloy matrix disclosed different-sized nonmetallic inclusions among models. EDS analysis of these inclusions showed that they were composed of carbon and oxygen in addition to nickel and titanium. Under light microscopy, austenitic grains appeared larger near the handle and smaller near the tip in all instruments.
NRT files presented the longest fatigue life. All samples showed surface irregularities and nonmetallic inclusions. Austenitic grains were smaller near the tip than near the handle. The angle of curvature was confirmed to influence the fatigue life of NiTi instruments.
本研究旨在比较四种镍钛旋转根管锉的循环疲劳性能，并评估其表面、断口形貌和基体形态。
将四种根管锉（EasyShape [德国科贸/布雷斯勒公司，莱姆戈]、ProTaper [登士柏迈兰公司，巴莱格]、NRT [MANI 公司，日本栃木县]和 AlphaKite [德国科贸/布雷斯勒公司]）分别进行疲劳试验，在弯曲角度为 45°和 60°、曲率半径为 5 毫米的人工根管内进行疲劳试验，直至发生断裂。通过光镜、环境扫描电子显微镜（ESEM）和能谱仪（EDS）对镍钛（NiTi）合金性能进行了研究。ESEM 分析在新锉刀上进行，以检查表面特征，在断裂样品上进行，以确定裂纹起源和断口特征。
方差分析显示，各组间差异有统计学意义（P <.001）。NRT 锉的疲劳强度最高，其次是 AlphaKite、EasyShape 和 ProTaper。所有新锉刀均存在表面缺陷。断口分析发现裂纹起源于表面不规则处。NiTi 合金基体的光学显微镜检查显示，各模型中有不同大小的非金属夹杂物。对这些夹杂物的 EDS 分析表明，它们除了镍和钛外，还含有碳和氧。在光镜下，所有器械的手柄附近奥氏体晶粒较大，尖端附近较小。
NRT 锉的疲劳寿命最长。所有样品均显示表面不平整和非金属夹杂物。尖端附近的奥氏体晶粒比手柄附近的小。曲率角被证实会影响 NiTi 器械的疲劳寿命。
