**5. Conclusions**

Compared with the PTU and PTN series, the PTG series demonstrated superior CF behavior. The PTU series was the least resistant to CF. As fatigue resistance is one of the most common factors attributed to instrument fracture and considering the recent advances in technology, international standards for CF testing devices should be established to minimize the variations in reported data. Furthermore, the experimental results and SEM analysis used in this work can be used to define the KT diagram for fatigue life prediction.

**Acknowledgments:** The authors thank King Saud University, College of Dentistry Research Center (CDRC), particularly the physical laboratory staff, for their assistance in conducting this study.

**Author Contributions:** Abdullah Alqedairi and Hussam Alfawaz designed the study, supervised and performed the experiments, analyzed the data, and finalized the manuscript. Amani bin Rabba, Areej Almutairi, and Sarah Alnafaiy performed the experiments and wrote the initial draft of manuscript. Muneer Khan Mohammed designed and fabricated the artificial canals, helped in statistical analysis and wrote the laser micromachining part of the manuscript.

**Conflicts of Interest:** The authors have no conflicts of interest to declare.
