Cyclic fatigue of advanced heat-treated nickel-titanium rotary files in simulated canals with single or double curvatures

Background: Fractures of endodontic files are one of the serious concerns affecting root canal treatment prognosis. Recently, countless innovations have been presented to optimize their microstructure and flexibility, reflected in different commercial brands. However, their performance has not been evaluated in complex root canals. Aim: To evaluate and compare the resistance to cyclic fatigue of three rotary endodontic files utilizing artificial canals designed with different angles and radii of curvature. Materials and Methods: sixty rotary instruments of the following types were used. Group I: Edge endo X7; Group II: Luster dent pliancy total solution; and Group III: Race Evo FKG. Instruments in each group were constrained into two subgroups (n=20) to be examined in artificial canals having a single curvature or a double curvature.  The cyclic fatigue resistance of each rotary file was tested, where the number of cycles to fracture (NCF) and the fractured segment length (FL) were recorded. Results: In both single and double curvature canals, the Edge endo X7 files (9162.50 ± 441.14 and 2210.00 ± 341.07, respectively) demonstrated significantly higher resistance to cyclic fatigue than did the Race Evo FK (3866.66 ± 410.99 and 1825.00 ± 230.17, respectively) and Luster dent pliancy total solution (7077.77 ± 1001.84 and 1257.77 ± 126.95, respectively). However, in the double canal tests, the Luster dent pliancy total solution had a greater mean NCF than the Race Evo FK. In relation to the FL, there was no statistically significant difference between any of the groups, and only the edge of the Endo X7 file was significantly different between single- and double-curvature canals (P = 0.058). Conclusion: The Edge Endo X7 rotary file demonstrated greater cyclic fatigue resistance than did the Race Evo FKG and Luster dent pliancy total solution.