“…During procedure of root canal treatment the endodontic files come in direct contact with pulp tissue, oral fluids blood and saliva, these files could be considered " reusable sharps " making there sterilization as a must mandatory step. (17) several sterilization techniques utilized such as autoclave,dry heat oven, ethylene oxide gas and also glass beads sterilizer which provide dry heat with shorter exposure time (18,19) Ni-Ti endodontic files are always having the risk of separation because of cyclic fatigue or torsional stress, (20,21,22) To reduce or overcome this mechanical failure, many method have been applicated by manufacturers to improve the fatigue resistance of file like electro-polishing the surface of the fileeg: (RaCe), twisting instead of machiningeg: (TF), and geometric characteristics alteration such as asymmetric design (Revo-S). (10,23) Today, thermal processing could be the main approach to develop the alloy metallurgy properties by affecting its transition temperatures and thus leading to alter the fatigue resistance.…”