## 3 Results  
The means and standard deviations of TfF are presented in Table 1.  
The inferential analysis revealed statistically significant differences between the different types of irrigation, considering the temperature as the independent variable (two-way ANOVA, \(p<0.05\); interaction \(<0.05\)). Moreover, there were statistically significant differences between the temperatures considering the type of irrigation as the independent variable (two-way ANOVA, \(p<0.05\)). Post-hoc analysis revealed that the cyclic fatigue resistance of all instruments, independently from the testing conditions, decreased at 37 \({}^{\circ}\)C (\(p<0.05\)). At 20 \({}^{\circ}\)C, NaOCl improved cyclic fatigue resistance of F6 ST and OC compared to the control group (\(p<0.05\)). However, liquid irrigant significantly improved the TfF of F6 ST compared to the gel one (\(p<0.05\)), while no difference was observed between the two formulations for OC (\(p>0.05\)). At 37 \({}^{\circ}\)C, no difference was observed among the control and experimental groups for F6 ST (\(p>0.05\)). For OC, groups treated with hypochlorite revealed significantly higher TfF than the control group (\(p<0.05\)), with no difference between liquid and gel NaOCl (\(p>0.05\)). Independently of the temperature and irrigant use, OC reported significant higher TfF than F6 ST (\(p<0.05\)).  
The length of the fractured file fragments was not statistically different among the tested instruments (mean = 5.1 mm) (\(p>0.05\)). Field-emission scanning electron microscopic analysis of the fractured surfaces exhibited the representative signs of cyclic fatigue failure for both instruments. The crack initiation areas, the presence of fatigue striations and the overload fast fracture zone induced by cyclic fatigue are visible in the fracture surface of all instruments (Figure 3A-L). More specifically, crack initiation was generated at the cutting edges of the fracture cross sections, with microscopic  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type of Irrigation** & \multicolumn{3}{c}{**F6 SkyTaper**} & \multicolumn{3}{c}{**One Curve**} \\ \hline
**Without NaOCl** & 120 \({}^{\circ}\)C \(\pm\) 1 \({}^{\circ}\)C & 37 \({}^{\circ}\)C \(\pm\) 1 \({}^{\circ}\)C & 20 \({}^{\circ}\)C \(\pm\) 1 \({}^{\circ}\)C & 37 \({}^{\circ}\)C \(\pm\) 1 \({}^{\circ}\)C \\
**Liquid NaCl5.25\%** & 186 \({}^{\mathrm{a}2}\) \(\pm\) 18 & 98 \({}^{\mathrm{b}1}\)\(\pm\) 11 & 279 \({}^{\mathrm{c}2}\)\(\pm\) 20 & 225 \({}^{\mathrm{d}2}\)\(\pm\) 21 \\
**Gel NaCl5.25\%** & 147 \({}^{\mathrm{a}3}\)\(\pm\) 13 & 92 \({}^{\mathrm{b}1}\)\(\pm\) 11 & 269 \({}^{\mathrm{c}2}\)\(\pm\) 16 & 215 \({}^{\mathrm{d}2}\)\(\pm\) 17 \\ \hline \hline \end{tabular} Different superscript letters show significant differences between the same instruments at different temperatures as well as between the two brands in the same irrigation group (p \(<0.05\)). Different superscript numbers show significant differences between irrigation groups in the same brand of files (p \(<0.05\)).  
\end{table}
Table 1: Time to Fracture in Seconds of Each Group as the Mean \(\pm\) Standard Deviation.  
dimples present on the separation area. None of the tested files showed pitting or crevice corrosion with or without 5.25% NaOCl as assessed through field scanning electron microscopy.