Comparison of cyclic fatigue resistance of nickel-titanium coronal flaring instruments

The purpose of this study was to compare the cyclic fatigue resistance of coronal flaring instruments.

Three groups of nickel-titanium (NiTi) endodontic coronal flaring instruments were tested in steel canals with a 3-mm curvature radius and 60° (n = 18) and 45° of curvature (n = 18). The cyclic fatigue of the following NiTi instruments was tested: ProTaper Sx (Dentsply Maillefer, Ballaigues, Switzerland), HyFlex 25.08 (Coltene-Whaledent, Allstetten, Switzerland), and Revo-S SC1 (Micro-Mega, Besancon, France). The length and diameter of the fractured fragment and the total area of the fractured surface of each instrument were measured. The data were then statistically analyzed using a 1-way analysis of variance and the post hoc Tukey test (α = .05).

At the 60° of curvature, Revo-S had the highest fatigue resistance, HyFlex had the second highest fatigue resistance, and ProTaper Universal had the least fatigue resistance. At the 45° of curvature, the Revo-S and HyFlex showed superior cyclic fatigue resistance compared with the ProTaper. The length of the fracture fragment of the ProTaper instrument was longer than that of the other groups at the 60° of curvature. At the 45° of curvature, the length of the fracture fragment of the ProTaper and HyFlex instruments was longer than that of Revo-S. The mean diameter and surface area of the HyFlex instruments in the fractured part was higher than that of other groups at both angles of curvature.

The Revo-S SC1 and HyFlex 25.08 instruments showed better cyclic fatigue resistance than the ProTaper Sx instrument.