Cyclic Fatigue, Torsional Failure and Flexural Resistance of Rotary and Reciprocating Instruments

Objectives: This study aimedto compare, cyclic fatigue, torsional failure and flexural resistance of NiTi endodontic files: Hyflex CM (HYF), Genius files (GEN), WaveOne Gold (WOG) and ProTaper Universal (PTU).
Methods: Fifteen instruments of each brand were usedin flexural test and the same instruments were used in the cyclicfatigue test, other fifteen were used to torsional failure test. To thecyclic fatigue test,no torque limit was applied and revolutions per minute (rpm) used were set according to the respective manufacturer guidelines. Test was made under deionized water at 36°C, and all instruments were tested in a 3mm radius of curvature with an angle of curvature of 60°, time of the fracture was recorded;Torsional fatigue test was performed in a machine (Instrom MT, USA), recording the fractured time and torque data by the machine software; Flexural fatigue test was performed in 60° of curvature.All data were statistically analyzedby one-way analysis of variance, Dun, andKruskal-Wallis test.
Results: Mean values of the test results: Cyclic fatigue (seconds) = HYF:744,1±231.9/ GEN:477,3±220.5/ WO:278,4±57.0/ PTU:152,4±65.2; Torsion failure (N X cm) = HYF:6,85±1.484/ GEN:6,55±0.828/ WOG:5,73±0.360/ PTU:4,43±0.900; Flexural resistance (N X mm) = HYF:0,33±0.294/ GEN:0,19±0.136/ WOG:0,98±0.216/ PTU:1,85±0.276. To all tests, Hyflex CM showed the best results, but it was not statistically different only from Genius, followed by Wave One and ProTaper Universal respectively.
Conclusions: Hyflex CM and Genius showed the best results for cyclic fatigue, torsional failure, and flexural resistance, followed by Waveone Gold and Protaper Universal.