Environmental Temperature Drastically Affects Flexural Fatigue Resistance of Nickel-titanium Rotary Files.

Introduction: The aim of the present study was to analyze how a low environmental temperature can affect the fatigue life of instruments made by different types of heat-treated nickel-titanium alloys.

Methods: The flexural cyclic fatigue of 40 new specimens for each of the following systems was tested for cyclic fatigue resistance: ProTaper Universal F2 (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Gold F2 (Dentsply Tulsa Dental Specialties, Tulsa, OK), Twisted Files SM2 (SybronEndo, Orange, CA), Mtwo #25.06 (VDW, Munich, Germany), and Vortex Blue #30.