Considering the long time spent in low frequency cyclic fatigue tests, this study aimed to evaluate the influence of loading frequency (2 Hz and 20 Hz) on the flexural fatigue strength (FFS) and on the time and number of cycles to failure of a leucite-reinforced glass-ceramic. Disc-shaped specimens were produced using leucite-reinforced glass-ceramic CAD/CAM blocks (IPS Empress CAD), according to ISO 6872/2015. Two fatigue tests were performed. The FFS (n = 17) was determined by staircase approach at a lifetime of 500,000 cycles, for 2 Hz (control – chewing frequency estimative) and 20 Hz (accelerated approach). To determine the time and the number of cycles to failure in flexural fatigue, discs (n = 20) were submitted to a cyclic loading ranging from 10 MPa to 99 MPa (60% of the monotonic strength), until a maximum of 500,000 cycles. Means, standard deviation and confidence intervals (CI) at 95% for FFS were calculated, whereas statistical differences were detected based on maximum likelihood estimations and overlapping of 95% CIs. Kaplan Meier (α = 0.05) and log rank post-hoc tests were used to analyze the time (in minutes) and the number of cycles to failure in the lifetime test. FFS did not differ significantly between 2 Hz (mean: 78 MPa; 95% CI: 69–88 MPa) and 20 Hz (mean: 84 MPa; 95% CI: 78–90 MPa). Regarding the lifetime test, there was no difference (p = 0.3) in the time to failure for 2 Hz (mean: 13 min; 95% CI: 6–20 min) and 20 Hz (mean: 69 min; 95% CI: 9–128 min). However, the group tested with 20 Hz survived a significantly (p < 0.01) higher number of cycles (mean: 82,247 cycles; 95% CI: 11,450–153,044) than the group tested with 2 Hz (mean: 1588 cycles; 95% CI: 779–2397). Therefore, in leucite-reinforced glass-ceramic fatigue strength tests, limited to a lifetime of 500,000 cycles, the use of loading frequencies up to 20 Hz did not influence the FFS estimations when compared to 2 Hz (chewing frequency estimative), and may be an alternative to accelerate data collection in this type of mechanical test. However, in lifetime tests, the use of higher loading frequencies, as 20 Hz, did not save time, since a higher number of cycles was necessary to promote the failure, when compared to 2 Hz.

考虑到长时间在低频循环疲劳测试中的花费，本研究旨在评估加载频率（2 Hz和20 Hz）对弯曲疲劳强度（FFS）以及对白云石破坏的时间和循环次数的影响增强玻璃陶瓷。根据ISO 6872/2015，使用白云石增强的玻璃陶瓷CAD / CAM块（IPS Empress CAD）制作了盘状样品。进行了两次疲劳测试。FFS（n = 17）是通过阶梯法在500,000个循环的寿命中确定的，频率为2 Hz（控制–咀嚼频率估算）和20 Hz（加速方法）。为了确定弯曲疲劳失效的时间和次数，将圆盘（n = 20）承受的循环载荷范围为10 MPa至99 MPa（单调强度的60％），直到最大500,000个循环。手段，计算了FFS在95％的标准偏差和置信区间（CI），而根据最大似然估计和95％CI的重叠检测到统计差异。Kaplan Meier（α= 0.05）和对数秩事后测试用于分析寿命测试中的时间（以分钟为单位）和失效循环的次数。FFS在2 Hz（平均：78 MPa； 95％CI：69-88 MPa）和20 Hz（平均：84 MPa； 95％CI：78-90 MPa）之间没有显着差异。关于寿命测试，在2 Hz（平均值：13分钟； 95％CI：6–20分钟）和20 Hz（平均值：69分钟； 95％CI ：）下，失效时间没有差异（p = 0.3）。 9–128分钟）。但是，以20 Hz进行测试的组比以2 Hz进行测试的组（平均值：1588周期； 95％CI）存活（p：0.01）的周期数（平均值：82,247个周期； 95％CI：11,450–153,044）高得多。 ：779-2397）。因此，在白云石增强的玻璃陶瓷疲劳强度测试中，寿命限制为500,000个循环，与2 Hz（咀嚼频率估算值）相比，使用高达20 Hz的加载频率不会影响FFS估算。这种类型的机械测试中加快数据收集速度的另一种选择。但是，在寿命测试中，使用较高的负载频率（例如20 Hz）并不能节省时间，因为与2 Hz相比，需要更多的循环次数来促进故障。在这种类型的机械测试中可能是加速数据收集的替代方法。但是，在寿命测试中，使用较高的负载频率（例如20 Hz）并不能节省时间，因为与2 Hz相比，需要更多的循环次数来促进故障。并可能是加快此类机械测试中数据收集速度的替代方法。但是，在寿命测试中，使用较高的负载频率（例如20 Hz）并不能节省时间，因为与2 Hz相比，需要更多的循环次数来促进故障。