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