**5. Conclusions**

NiTi alloy endodontic rotary files used with a reciprocating movement at 350 rpm with 120◦ counterclockwise and 30◦ clockwise motion were more resistant to dynamic cyclic fatigue than those used with a reciprocating movement at 400 rpm with 120◦ counterclockwise and 30◦ clockwise motion, continuous rotational speed at 200 rpm, continuous rotational speed at 350 rpm, and continuous rotational speed at 500 rpm. It is therefore advisable to use reciprocating movements at a low speed.

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

**Funding:** This research did not receive any external funding.

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Information available upon request, subject to relevant restrictions (such as privacy or ethical).

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