EVALUATION OF CYCLIC FATIGUE, TORSIONAL RESISTANCE AND ANGLE DEFLECTION OF A NEW ENDODONTIC INSTRUMENT

Abstract

The aim of this study was to evaluate the cyclic fatigue and torsional resistance, and angular deflection of a new nickel-titanium (NiTi) instrument. Sixty instruments were selected: ProDesign Logic2 25.03 (n=20) and 25.05 (n=20) (Easy Equipamentos Odontolo?gico, Belo Horizonte, Brazil) and Flat File 25.04 (n=20) (MK Life, Porto Alegre, Brazil). For the cyclic fatigue test, instruments were introduced into an artificial stainless-steel canal with a 60° angle and 5mm curvature radius located 5mm from the instruments tip. Cyclic fatigue test was performed at controlled room temperature (37o ± 1oC). Time to fracture was recorded and calculated. Torque and angle of rotation at failure were measured according to ISO 3630-1, in which the 3mm tip of each instrument was fixed and connected to a motor, a processor and a load cell. Torque (N/cm) to instrument fracture was measured and angular deflection at failure was recorded (in degrees). Statistical analysis was performed using one-way ANOVA and Tukey post hoc tests. Flat File 25.04 instruments had a lower cyclic fatigue resistance than Logic 25.03 and 25.05 instruments (P < 0.05). Flat File 25.04 and Logic2 25.05 presented similar torque to fracture (P < 0.05) and both were more torque resistant than Logic2 25.03 (P < 0.05). Angular deflection was different for all tested instruments (P < 0.05), as follows: Logic2 25.03, Logic2 25.05 and Flat File 25.04. Mechanical properties of the evaluated instruments depended on their geometric features and thermal treatment of the NiTi alloy.