Evaluation of torsional strength and bending stiffness of Edge Endo file systems using different heat treatments

Introduction: Ideal endodontic instruments should exhibit high fracture resistance and flexibility, which facili tate endodontic therapy and result in no complications.Objectives: This study aimed to evaluate and compare the torsional strength and bending stiffness of three diffe rent Edge Endo file systems.Material and methods: Ninety NiTi rotary files of EdgeFile X7 (EX7), Edge X7 Utopia (EX7 Utopia), and EdgeOne Blaze Utopia (EOB Utopia) of 25 mm length and #25 tip size were used.Torsional strength was evaluat ed at BT (n 15/file) by repetitive torsional load method, using endomotor with autostop property at 300 rpm and 2 Ncm maximum speed and torque.Fractured files were examined under SEM to identify topographic charac teristics of fracture surface.Cantilever bending test was employed to assess bending stiffness at BT (n 15/file) by applying a load at 3 mm from the tip, and bending stress resistance was recorded.Data were analyzed by oneway ANOVA and Tukey HSD tests at p < 0.05 significance level. Results:The EX7 file demonstrated the highest torsional resistance and the lowest bending resistance (p < 0.05), while the EOB Utopia file showed the lowest torsional resistance.The EX7 Utopia file displayed the highest bend ing resistance.Conclusions: Torsional and bending resistance of the tested rotary NiTi file systems significantly decreased with the FireWire Blaze new heat treatment.