Flexibility and resistance to cyclic fatigue of instruments manufactured by different methods

Abstract

Objective: This study compared the mechanical behavior of nickel-titanium instruments with similar geometry, but manufactured by different methods. Material and Methods: Twenty 25/0.06 RaCe files (FKG Dentaire, La Chaux-de-Fonds, Switzerland), 25 mm in length, manufactured with machined conventional NiTi wires; twenty 25/0.06 Twisted File endodontic instruments (TF) (SybronEndo, Orange, CA, USA), 27 mm in length, manufactured by twisting; and twenty 25/0.06 ProFile Vortex endodontic instruments (Dentsply Tulsa Dental, Tulsa, OK, USA), 25 mm in length, manufactured with M-Wire alloy were subjected to flexibility and cyclic fatigue tests. Each group comprised 10 instruments from each manufacturer. Results: Parametric ANOVA revealed significant difference between maximum load values in the following sequence: ProFile Vortex > RaCe > TF (p < 0.01). The rotating-bending test assessed the cyclic fatigue by measuring the time and number of cycles to fracture (NCF). Parametric ANOVA, with significance level set at 1%, revealed that RaCe files had significantly lower resistance than ProFile Vortex which, in turn, had lower values than TF, in terms of time and number of cycles (p < 0.01). Conclusion: TF instruments were more flexible than RaCe which, in turn, presented lower resistance than ProFile Vortex. Regarding the cyclic fatigue test, TF instruments had significantly better performance than the other two instruments tested, particularly in terms of time and NCF.