According to the Shanghai Stomatological Hospital's Clinical Analysis of Nitinol Expanding Needles, the main factors affecting the life of Nitinol expanding needles are stress fatigue fracture of Nitinol alloy and calcification of the root canals, which depends on whether or not the root canals prepared with Nitinol are smooth and whether or not the operator operates in accordance with the standard procedure.
Therefore, it is recommended that each set of Nitinol reaming needles should be used 22 times for clinical use, and the number of preparations should be reduced if there is a lot of calcification and bending during the preparation of root canals. If the preparation process is artificially broken, increase the thickness of the flaring needles and try to select straight and smooth canals for use.