**5. Conclusions**

The conclusion derived from the present study is that the double S-shaped crosssection of Mtwo NiTi endodontic files shows higher cyclic fatigue resistance than the rectangular cross-section of T Pro E1 NiTi endodontic files, the convex triangular crosssection of T Pro E2 NiTi endodontic files, and the triangular cross-section of T Pro E4 NiTi endodontic files.

**Author Contributions:** Conceptualization, V.F.-L., N.H.-K. and Á.Z.-M.; design, I.F.-M.; data acquisition, C.R.S.; formal analysis, V.F.-M.; statistical analyses, Á.Z.-M. and V.F.-L.; review and editing, N.H.-K. and M.T.M.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data are available on request due to restrictions, e.g., privacy or ethical.

**Conflicts of Interest:** The authors declare no conflict of interest.
