Cyclic and Torsional Fatigue Resistance of a New Rotary File on a Rotary and Reciprocating Motion.

Abstract

Introduction: This study aimed to evaluate the cyclic and torsional fatigue resistance of a new nickel-titanium (Flat File 25.04) instrument on continuous and reciprocating motion. Methods: Sixty instruments of the ProDesign Logic2 25.03 and 25.05 (Easy Equipamentos Odontológicos, Belo Horizonte, Brazil), and MK Flat File 25.04 (n=20) (MK Life, Porto Alegre, Brazil) were used. For the cyclic fatigue test, an artificial stainless steel simulated canal with an angle of 60° and a radius of curvature of 5mm located 5mm from its tip was used. Torque and angle of rotation at failure of instruments on torsional fatigue test was based on the ISO 3630-1 protocol, in which the 3mm tip of each instrument was fixed and connected to an electric motor and a load cell. The fractured surface of each fragment was examined by scanning electron microscopy. Data were analyzed using 1-way analysis of variance and Tukey’s test with a significance level of 5%. Results: Flat File 25.04 had lower cyclic fatigue in both kinematics than the Logic instruments (P < .05). Reciprocating motion improved the cyclic fatigue of the tested instruments (P < .05). Flat File 25.04 had similar torque to Logic2 25.05 (P < .05), and both were superior to Logic2 25.03 (P < .05). The angular deflection values were different for the three tested instruments (P < .05), in the decreasing order: Logic2 25.03, 25.05, and Flat File 25.04. Conclusion: Flat File presented acceptable resistance to cyclic and torsional fatigue resistance. Reciprocating motion improved the cyclic fatigue resistance of the instruments and can be considered when using programmable motors.