Effect of Rotational Speed on the Resistance of NiTi Alloy Endodontic Rotary Files to Cyclic Fatigue—An In Vitro Study

Abstract

The present study aims to evaluate and contrast the function of the rotational speed of NiTi alloy endodontic rotary files on how resistant they are to dynamic cyclic fatigue. Methods: A total of 150 NiTi alloy endodontic rotary files with similar geometrical design and metallurgical properties were randomly divided into study groups: Group A: 200 rpm (n = 30); Group B: 350 rpm (n = 30); Group C: 500 rpm (n = 30); Group D: reciprocating movement at 350 rpm with 120° counterclockwise and 30° clockwise motion (350 rpm+) (n = 30); and Group E: reciprocating movement at 400 rpm with 120° counterclockwise and 30° clockwise motion (400 rpm+) (n = 30). A dynamic device was designed to carry out dynamic cyclic fatigue tests using artificial root canal systems made from stainless steel with an apical diameter of 250 µm, 5 mm radius of curvature, 60° curvature angle, and 6% taper, and 20 mm in length. A Weibull statistical analysis and ANOVA test were used to analyze the results. Results: The ANOVA analysis showed differences in time to failure among all the study groups that were of statistical significance (p < 0.001). Conclusions: NiTi alloy endodontic rotary files using reciprocating movement at 350 rpm with 120° counterclockwise and 30° clockwise motion exhibit greater resistance to dynamic cyclic fatigue than files used with a reciprocating movement at 400 rpm with 120° counterclockwise and 30° clockwise motion, continuous rotational speed at 200 rpm, continuous rotational speed at 350 rpm, or continuous rotational speed at 500 rpm; it is therefore advisable to use reciprocating movements at a low speed.

Assessment of the Cyclic Fatigue Performance of the Novel Protaper Ultimate File System Used in Different Kinematics: An In Vitro Study

“…The present study showed that all of the file systems had an improved TTF/NCF when FRM was employed, in accordance with the findings derived from V Faus-Matoses (2022) [29], Ferreira F et al (2017) [46], and Van der Vyver 2020 [47], who indicated that the resistance of NiTi alloy endodontic rotary files to cyclic fatigue was better when reciprocating motion was used compared to CR.…”

“…Another important factor that can affect the cyclic fatigue resistance of endodontic rotary instruments is the speed at which the endodontic instruments are rotated, as this could play an important role in the cyclic behavior [28]. Various studies have shown that the TTF is linked to the rotation speed, i.e., instruments show more resistance when used at lower speeds [24]; therefore, it is preferable to use instruments at a low speed [29]. In his study from 2014, Pedulla E. [30] found, in agreement with other results, that the rotational speed has no significant influence on the number of rotations needed to fracture NiTi rotary instruments; although speed does not influence the NCF, it has an influence on the TTF, as observed by Zanza A.…”

Effect of simulated clinical use and sterilization on the cyclic fatigue resistance of nickel titanium files

“…However, this finding could be attributed to the high rotational speed of Race Evo (800 rpm) compared to Tia Tornado (350 rpm). A recent study indicated that the resistance of NiTi rotary files to cyclic fatigue is inversely proportional to the rotational speed, it found that files rotating at 200 rpm and 350 rpm are significantly more resistant to cyclic fatigue failure compared to the same files when rotating at 500 rpm ( Faus-Matoses et al, 2022 ). Conversely, another recent study testing the cyclic fatigue resistance and bending of the files used in this study (Race Evo and Tia Tornado Blue files) found that Race Evo files are more resistant to cyclic fatigue failure than Tia Tornado Blue files ( Ramadan, AbuMostafa & Alharith, 2023 ).…”

NiTi rotary system in endodontics – An overview

“…cyclic fatigue is inversely proportional to speed. 16 Greater speed leads to lots of disadvantage like canal transportation, breakage of instruments, loss of tactile sensation.…”