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(CC BY-NC 4.0).
Background: Endodontic nickel-titanium [NiTi] instruments, made from nitinol wire, are considered to facilitate root
canal preparation with less procedural errors due to their superelasticity. Despite the advantages of using the nickeltitanium alloy files , fracture of the rotary files remain a major concern when using these instruments.
Aim: The aim of the present study to evaluate effect different rotational-speed and torque on cyclic-fatigue resistance
of nickel-titanium-[Ni-Ti] endodontic-rotary files.
Methods: A total of 90 ProTaper Next shaper files X2 in six groups with different rotational speeds and torques rotated in an artificial canal made of stainless steel with 45° angles and a radius of curvature of 8 mm of curvature until fracture.
The time of fracture was recorded in second using a digital chronometer, The length of fracture was obtained by
measuring the fracture instrument using a digital microcaliper. Data were statistically analyzed by using one way
ANOVA and Tukey HSD test.
Results: The ANOVA test showed significant differences in resistance to cyclic fatigue among three rotational speed
groups [P < 0.05] and no significant difference among different torque.
Conclusions: The study reveals NiTi rotary files have higher resistance to static cyclic fatigue at 200 RPM, less
resistance at 500 RPM, no significant differences in different torque.