Cyclic Fatigue Resistance of Edge File X7 and 2Shape Endodontic Systems: in vitro study.

Objectives: In order to test the resistance of rotary instruments to cyclic fatigue fracture and its importance in root canal preparationthe purpose of this study was to see how different tapers (4% and 6%) affected the cyclic fatigue resistance of the Edge File X7 and 2Shape endodontic systems at 45° and 60°canal curvature.Methods: Eighty NiTi files from two different systems (N= 40 each) were used; Group 1: Edge File X7, Group 2: 2Shape. each group was subdivided into four subgroups (N= 10 for each subgroup). The files were evaluated for cyclic fatigue resistance using a modified custom-made static model with 45°and 60° angles having a radius of 3mm and a diameter of 1.5 mm. Each file was rotated in a continuous rotation motion at 300 rpm with 1.2 N.cm torque for TS1, 300 rpm with 2.5 N.cm torque for TS2, and Edge file X7 was used at 300 rpm and 3 N.cm. Until it fractured. The time it took to separate the files was noted. Each file's number of cycles to failure was computed. A Kolmogorov-Smirnova normality test was done for all groups, and a two-way ANOVA was used to statistically examine the data.Results: The ranking of the groups from the highest to the lowest NCF was as follows: EdgeFile 4% 45 degrees (6594.00), EdgeFile 6% 45 degrees (6317.90), EdgeFile 4% 60 degrees (5682.00), EdgeFile 6% 60 degrees (2142.00), 2Shape 4% 45 degrees (2517.00), 2Shape 4% 60 degrees (535.90), 2Shape 6% 45 degrees (474.50), and 2Shape 6% 60 degrees (213.00).                                                                                                                                                Conclusions: Edge File X7 showed better results than the 2Shape system. EdgeFile X7 4% at 45 degrees showed the highest NCF. The 2Shape system 6% at 60 degree that showed lowest NCF. As the canal curvature increased the NCF decreased. Taper 4% is better than taper 6%.