## 4 Discussion  
The results obtained in the present study reject the null hypothesis (H0) that states that time of use would have no effect on the dynamic cyclic fatigue resistance of NiTi endodontic reciprocating files. However, it also accepts the null hypothesis (H0) that states that the number of sterilization cycles applied to NiTi endodontic reciprocating files would have no effect on their resistance to dynamic cyclic fatigue. The cyclic fatigue resistance of NiTi endodontic rotary and reciprocating instruments has been widely compared with regard to the NiTi alloy used, cross-section design, curvature angle, radius, pecking motion frequency, etc., with both static and dynamic custom-made cyclic fatigue devices having been used [20; 21]. However, dynamic custom-made cyclic fatigue devices are the only ones that faithfully simulate the pecking movement performed by the clinician, more accurately representing the amount of time during which the NiTi endodontic rotary instrument remains in the artificial root canal. In addition, the artificial root canal should be custom-designed for the specific NiTi endodontic rotary instrument being tested in order to ensure immediate contact with the artificial root canal (as happens in a clinical setting). This also ensures that compression and tensile stress cycles are localized at the maximum flexure point [22], distributes the shear resistance homogeneously along the NiTi endodontic rotary instrument surface, and leads to the formation of microcracks on the instruments' microstructure [23] without any signs of plastic deformation in the static model; the area of these stresses spreads through the instrument shaft in the dynamic model [21]. Most of the static and dynamic custom-made cyclic fatigue devices provided a non-instrument-based artificial root \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Study Group** & \multicolumn{3}{c}{**Weibull Shape (\(\beta\))**} & \multicolumn{3}{c}{**Weibull Scale (\(n\))**} \\ \hline  & **Estimate** & **St Error** & **Lower** & **Upper** & **Estimate** & **St Error** & **Lower** & **Upper** \\ \hline
0 s & 7.8371 & 1.0332 & 6.0526 & 10.1478 & 247.8093 & 5.2331 & 237.7620 & 258.2813 \\
60 s & 5.9056 & 0.7502 & 4.6039 & 7.5752 & 213.5034 & 6.0177 & 202.0287 & 225.6298 \\
120 s & 8.0777 & 0.9119 & 6.4743 & 10.0782 & 93.5190 & 1.9349 & 89.8025 & 97.3892 \\
0 cycles & 2.8397 & 0.4369 & 2.1004 & 3.8391 & 202.3470 & 13.6633 & 177.2639 & 230.9795 \\
1 cycle & 2.6486 & 0.4087 & 1.9573 & 3.5841 & 198.0170 & 14.3348 & 171.8235 & 228.2036 \\
5 cycles & 2.9091 & 0.4413 & 2.1610 & 3.9163 & 187.3384 & 12.3756 & 164.5872 & 213.2345 \\
10 cycles & 2.8747 & 0.4233 & 2.1540 & 3.8366 & 191.7153 & 12.8646 & 168.0889 & 218.6626 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Weibull statistics of the number of cycles of in-and-out movements for the time of use and sterilization cycles study groups. Figure 8: **(A)** Weibull probability plot of the number of cycles of in-and-out movements for the time of use and **(B)** sterilization cycles study groups. canal [24; 25], so the results extracted from these studies should be carefully considered and not applied to clinical practice. [PERSON] et al. reported statistically significant differences (\(p<0.05\)) between the time to failure of Wave One Gold NiTi endodontic reciprocating files (\(50.75\pm 20.06\) s) and Reziflow (\(30.13\pm 9.40\)) conventional NiTi endodontic rotary instruments [26]. Although this was a static cyclic fatigue test with an artificial root canal of parallel walls and \(90^{\circ}\) and \(5\) mm curvature radius, Reziflow has a similar design and manufacturing process as Procedile. In this study, a curvature angle of \(60^{\circ}\) was designed, because [PERSON] et al.