目的：比较高压蒸汽灭菌对K3XF和K3表面形态和疲劳折断性能的影响。方法：将25 mm长、25#/0.06锥度的K3XF和K3各48支随机分为4组（n=12），组1不做处理，组2~4分别进行高压蒸汽灭菌，分别循环10次、20次、30次。每组随机选取2支锉在扫描电子显微镜（scanning electron microscope，SEM）下观察表面形态，其余10支锉使用60°弯曲角度、3.5 mm弯曲半径的模拟金属根管进行疲劳折断实验。记录疲劳折断时间，计算疲劳折断圈数（number of cyclic fatigue，NCF），测量折断段长度，并对折断断口进行SEM观察。以SAS 9.3软件进行双因素方差分析，显著性水平0.05。结果：SEM观察可见K3XF表面粗糙，呈现微孔结构，K3沟槽处表面有明显车磨条纹，切割刃处较平滑。高压蒸汽灭菌使K3XF的微孔数量增加且孔径变大，K3的车磨条纹变形、受挤压、裂开。K3XF新锉的NCF为210±59，高压蒸汽灭菌10次、20次、30次后的NCF分别为178±37，208±48和227±43，与新锉相比，差异均无统计学意义（P>0.05）。K3新锉的NCF为145±38，高压蒸汽灭菌10次、20次后的NCF分别为128±43和124±46，与新锉相比，差异均无统计学意义（P>0.05），但是高压蒸汽灭菌30次后，NCF显著升高到216±38（P<0.05），所有断口均呈典型的疲劳折断特征。结论：K3XF经多次高压蒸汽灭菌后，表面粗糙度增加，但是疲劳折断性能保持稳定。

Objective： To compare the effects of autoclave on surface microstructure and cyclic fatigue resistance of K3XF and K3. Methods: Forty-eight size 25, 0.06 taper 25 mm-long K3XF or K3 were randomly divided into 4 groups (n=12). The instruments from group 1 were not autoclaved, and the groups 2 to 4 underwent autoclave for 10 cycles, 20 cycles, and 30 cycles, respectively. The surface microstructure of two instruments randomly selected from each group was observed using scanning electron microscope (SEM). The remaining 10 instruments were submitted to the cyclic fatigue test by using a simulated metal root canal with curvature of 60° and radius 3.5 mm. The time till fracture was recorded, the number of cyclic fatigue (NCF) calculated, the fragment length evaluated, and the topographic features were analyzed using SEM. The data were analyzed using the two-way ANOVA analysis by SAS 9.3 software at a significance level of P<0.05. Results: SEM observation identified rough features on the surface of K3XF with micropores existing evenly. K3 was characterized by machining grooves, which located specifically in the flute, leaving a smooth cutting edge. After autoclave, SEM observation indicated that the micropores in the surface of K3XF became larger and more, whereas the machining grooves in the surface of K3 were squeezed, out of shape and flaking. As far as the NCF was concerned, new K3XF was 210±59, and no significant difference was found after 10, 20, and 30 cycles of autoclave for K3XF, values being 178±37, 208±48, and 227±43, respectively (P>0.05). For K3, the new one was 145±38, and no significant difference in NCF was demonstrated after 10 and 20 cycles of autoclave, with the values of 128±43 and 124±46, respectively (P>0.05). However, after 30 cycles of autoclave of K3, significant increase to 216±38 was identified (P<0.05). Topographic features demonstrated typical cyclic fatigue for all the groups. Conclusions: The surface roughness of K3XF was increased after autoclave, while the cyclic resistance remained stable after up to 30 cycles.