Torsional, Static, and Dynamic Cyclic Fatigue Resistance of Reciprocating and Continuous Rotating Nickel-Titanium Instruments

Introduction: The aim of this study was to evaluate torsional, dynamic, and static cyclic fatigue resistance of the reciprocating One RECI (OR; Micromega, Besancon, France), WaveOne Gold (WOG; Dentsply Maillefer, Ballaigues, Switzerland), rotary One Curve (OC, MicroMega), and ProTaper Next X2 (PTN X-2; Dentsply Sirona, Charlotte, NC) instruments. Methods: A total of 120 OR (n = 30), WOG (n = 30), OC (n = 30), and PTN X2 (n = 30) nickel-titanium instruments were used. Torque and rotation angle until failure under static torsion loading were measured according to ISO 3630-1. Static and dynamic fatigue resistance was measured as the time to fracture in an artificial stainless steel canal with a 60 degrees angle and 5-mm radius of curvature at intracanal temperature. The results were analyzed with 1-way analysis of variance and the post hoc Tukey test. The alpha-type error was set at 5%. Fracture instruments from torsion and fatigue tests were examined with a scanning electron microscope. Results: OR showed higher static fatigue resistance and rotation angle at fracture than WOG, OC, and PTN X2 (P <.05). WOG exhibited higher torsional resistance than the others (P <.05). The cyclic fatigue tests in dynamic mode had higher TTF than static for the PTN X2 and WOG groups (P <.05). In the dynamic tests, OR and WOG showed higher TTF than OC and PTN X2 ( P <.05). Conclusions: Under these experimental conditions, One RECI exhibited suitable mechanical properties with the highest cyclic fatigue resistance and angle of rotation among the tested instruments. (J Endod 2022;48:1421-1427.)

Automated summary

This study aimed to evaluate the torsional, dynamic, and static cyclic fatigue resistance of different endodontic instruments. Results showed that One RECI had the highest cyclic fatigue resistance and rotation angle among the tested instruments. WaveOne Gold exhibited good torsional resistance. In the dynamic tests, One RECI and WaveOne Gold had longer fatigue time compared to One Curve and ProTaper Next X2.