Abdulkareem, Tareq Ahmad2022-07-212022-07-212022430.1-2022.03https://repository.mbru.ac.ae/handle/1/998Background: Endodontic rotary instruments can be used in a variety of canal conditions; fatigue fracture is a risk. This study looked at the cyclic fatigue resistance of two batches of nickel–titanium (NiTi) dental rotary files with same geometry and different heat treatments operating in clinically simulated root canal. Aim: To compare the deference in the cyclic fatigue resistance between heat treated and nonheat treated NiTi rotary instruments in static and dynamic modes. Materials and Methods: Cyclic fatigue tests were performed on PTU and PTG instruments with a curvature of 35° and a radius of 6 mm in static and dynamic mode at body temperature (EndoC: DMJ mechanism, Busan, Korea). The number of cycles to fracture (NCF) was rerecorded. A scanning electron microscope was used to examine the fracture surfaces of all fragments. Results: Depending on the motions performed, the cyclic fatigue resistance of the PTU and PTG varies (static or dynamic). When PTU and PTG were compared, they showed statistically significant differences in cycle fatigue resistance. PTG had higher cyclic fatigue fracture resistance on both modes tasted, but dynamic mode of testing of testing was associated with a high NCF in both files tested. The transverse and longitudinal sections of SEM micrograph of the specimens were examined after cyclic fatigue testing for PTG files and PTU files. The micro crack initiation regions, overload quick fracture areas, and microcrack areas in both were identified. PTG was discovered to have a lower concentration of microcracks.enEndodonticsThesis