OBJECTIVES The aim of this study was to compare body temperature cyclic fatigue resistance (CF) of heat-treated NiTi rotary instruments submitted to gamma-irradiation or autoclave sterilization. MATERIALS AND METHODS A total of 176 instruments (88 Hyflex EDM (HEDM) and 88 TRUShape (TS)) were used. Forty-four of each were submitted to gamma-irradiation. Twenty-two in each group were further autoclaved, resulting in a total of eight groups (n = 22 each): TS-γ and HEDM-γ (gamma-irradiated)/TS-γ-ac and HEDM-γ-ac (gamma-irradiated and autoclaved)/TS-non-γ and HEDM-non-γ (non-sterilized controls, non-gamma-irradiated/non-autoclaved)/TS-non-γ-ac and HEDM-non-γ-ac (non-gamma-irradiated and autoclaved). Twenty in each were tested for CF. Weibull parameters were calculated and compared. The remainder was used for differential scanning calorimetry analysis. RESULTS TS instruments lasted significantly longer if not submitted to gamma-irradiation (TS-non-γ mean-life = 101.5 s, 95 CI% 91.7-112.3; TS-γ mean-life = 83.2 s, 95 CI% 76-91.1); further autoclaving did not significantly affect CF. Gamma-irradiation did not affect HEDM (HEDM-γ mean-life = 717.9 s, 95 CI% 636.8-809.3; HEDM-non-γ: mean-life = 678.8 s, 95 CI% 595.1-744.2); further sterilization significantly decreased fatigue resistance (HEDM-γ-ac mean-life = 524.1 s, 95 CI% 476.1-576.8; HEDM-non-γ-ac mean-life = 570.6, 95 CI% 512.3-635.5). Gamma irradiation benefited HEDM conversion to martensite state and its maintenance, while further autoclave sterilization reverted the benefit. CONCLUSIONS Gamma-irradiation and autoclaving differentially affected fatigue life span and transformation temperatures of contemporary martensitic rotary instruments manufactured with different methods. CLINICAL RELEVANCE Gamma-ray processing is increasingly utilized by manufacturers for clinician to use fully sterile packaged instruments; however, the sterilization method of choice should vary depending on the effects on the behavior of contemporary martensitic rotary instruments manufactured with different methods.

中文翻译：

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伽马射线灭菌对当代镍钛仪器的相变行为和抗疲劳性的影响。

目的本研究的目的是比较经受过γ射线辐照或高压灭菌的热处理后的NiTi旋转器械的体温循环疲劳强度（CF）。材料与方法总共使用了176种仪器（88种Hyflex EDM（HEDM）和88种TRUShape（TS））。每个中有44个接受了伽马射线辐照。将每组中的22个进一步高压灭菌，总共形成8组（每组n = 22）：TS-γ和HEDM-γ（γ辐照）/TS-γ-ac和HEDM-γ-ac（γ -辐照和高压灭菌）/ TS-非-γ和HEDM-非-γ（非灭菌对照，非伽马射线辐照/非高压灭菌）/ TS-非-γ-ac和HEDM-非-γ-ac非伽马射线照射和高压灭菌）。每个测试20个CF。计算并比较了威布尔参数。其余的用于差示扫描量热分析。结果如果不接受伽玛射线辐照，TS仪器的寿命会大大延长（TS-非γ平均寿命= 101.5 s，95 CI％91.7-112.3；TS-γ平均寿命= 83.2 s，95 CI％76-91.1）。 ; 进一步的高压灭菌对CF无明显影响。伽马射线辐照不影响HEDM（HEDM-γ平均寿命= 717.9 s，95 CI％636.8-809.3;HEDM-non-γ：平均寿命= 678.8 s，95 CI％595.1-744.2）; 进一步灭菌会显着降低抗疲劳性（HEDM-γ-ac平均寿命= 524.1 s，95 CI％476.1-576.8;HEDM-non-γ-ac平均寿命= 570.6，95 CI％512.3-635.5）。伽马射线辐照有益于HEDM转变为马氏体状态及其维护，而进一步的高压灭菌处理则恢复了这种优势。结论伽马射线辐照和高压灭菌会不同程度地影响使用不同方法制造的当代马氏体旋转器械的疲劳寿命和转变温度。临床相关性制造商越来越多地使用伽马射线处理技术，以供临床医生使用完全无菌的包装器械。但是，选择的灭菌方法应根据对用不同方法制造的现代马氏体旋转器械的性能影响而有所不同。