Department of Conservative Dentistry, School of Dentistry, Complutense University, Madrid, Spain; Department of Endodontics, University of the Pacific Arthur A. Dugoni School of Dentistry, San Francisco, California.
Department of Conservative Dentistry, School of Dentistry, Complutense University, Madrid, Spain.
J Endod. 2018 Apr;44(4):630-634. doi: 10.1016/j.joen.2017.11.022. Epub 2018 Feb 3.
The aim of this study was to assess differences in cyclic fatigue (CF) life of contemporary heat-treated nickel-titanium rotary instruments at room and body temperatures and to document corresponding phase transformations.
Forty Hyflex EDM (H-EDM) files (Coltene, Cuyahoga Falls, OH [#25/.08, manufactured by electrical discharge machining]) and 40 TRUShape (TS) files (Dentsply Tulsa Dental Specialties, Tulsa, OK [#25/.06v, manufactured by grinding and shape setting]) were divided into 2 groups (n = 20) for CF resistance tests in a water bath either at room (22°C ± 0.5°C) or body temperature (37°C ± 0.5°C). Instruments were rotated in a simulated canal (angle = 60°, radius = 3 mm, and center of the curvature 5 mm from the tip) until fracture occurred. The motor was controlled by an electric circuit that was interrupted after instrument fracture. The mean half-life and beta and eta Weibull parameters were determined and compared. Two instruments of each brand were subjected to differential scanning calorimetry (DSC).
While TS instruments lasted significantly longer at room temperature (mean life = 234.7 seconds; 95% confidence interval [CI], 209-263.6) than at body temperature (mean life = 83.2 seconds; 95% CI, 76-91.1), temperature did not affect H-EDM behavior (room temperature mean life = 725.4 seconds; 95% CI, 658.8-798.8 and body temperature mean life = 717.9 seconds; 95% CI, 636.8-809.3). H-EDM instruments significantly outlasted TS instruments at both temperatures. At body temperature, TS was predominantly austenitic, whereas H-EDM was martensitic or in R-phase. TS was in a mixed austenitic/martensitic phase at 22°C, whereas H-EDM was in the same state as at 37°C.
H-EDM had a longer fatigue life than TS, which showed a marked decrease in fatigue life at body temperature; neither the life span nor the state of the microstructure in the DSC differed for H-EDM between room or body temperature.
本研究旨在评估在室温（22°C±0.5°C）和体温（37°C±0.5°C）下，现代热处理镍钛旋转器械的循环疲劳（CF）寿命差异，并记录相应的相变。
将 40 根 Hyflex EDM（H-EDM）锉（Coltene，Cuyahoga Falls，OH，#25/.08，电火花加工制造）和 40 根 TRUShape（TS）锉（Dentsply Tulsa Dental Specialties，Tulsa，OK，#25/.06v，研磨和成型制造）分为两组（每组 20 根），在水浴中进行 CF 阻力测试，水浴温度分别为室温（22°C±0.5°C）或体温（37°C±0.5°C）。器械在模拟根管中旋转（角度=60°，半径=3mm，曲率中心距尖端 5mm），直至断裂。电机由一个电路控制，当器械断裂时电路会被中断。确定并比较平均半衰期和 beta 和 eta 威布尔参数。每个品牌的两个器械进行差示扫描量热法（DSC）。
TS 锉在室温下的使用寿命明显长于体温下的使用寿命（室温下的平均寿命为 234.7 秒；95%置信区间[CI]，209-263.6，而体温下的平均寿命为 83.2 秒；95%CI，76-91.1），但温度对 H-EDM 行为没有影响（室温下的平均寿命为 725.4 秒；95%CI，658.8-798.8，体温下的平均寿命为 717.9 秒；95%CI，636.8-809.3）。H-EDM 器械在两种温度下均明显比 TS 器械耐用。在体温下，TS 主要是奥氏体，而 H-EDM 是马氏体或 R 相。在 22°C 时，TS 处于奥氏体/马氏体混合相，而 H-EDM 处于与 37°C 相同的状态。
H-EDM 的疲劳寿命长于 TS，后者在体温下的疲劳寿命明显下降；在室温或体温下，H-EDM 的寿命和 DSC 中的微观结构状态均无差异。
