Effect of different kinematics and operational temperature on cyclic fatigue resistance of rotary NiTi systems

Abstract

Background The aim of this study was to compare the effect of different kinematics and operational temperature on cyclic fatigue resistance of Protaper Next, WaveOne Gold, and Twisted File Adaptive files in a static model. Methodology An artificial canal, made of stainless steel with an inner diameter of 1.5 mm, a 60° angle of curvature, and a curvature radius of 2 mm, was used for the cyclic fatigue test immersed in a water bath for temperature adjustment (37 °C and 20 °C). A total of 120 files were divided into three groups according to the type of motion continuous rotation motion (CRM), adaptive motion (AM), and reciprocation motion (RM). Each group was further subdivided into two subgroups according to the operational temperature (37 °C and 20 °C), All instruments were operated until fracture occurred, and the time to fracture was recorded in seconds. Mean number of cycles to failure and standard deviations were calculated for each group, and data were analyzed statistically using two-way ANOVA followed by Tukey’s post hoc test (P ≤ 0.05). Results The continuous rotation motion exhibited significantly lower cyclic fatigue resistance than reciprocating or adaptive motion (p ≤ 0.001) at 37 °C and 20 °C. Conclusions Cyclic fatigue resistance of NiTi files was affected by the motion used during root canal preparation. Reciprocation motion and adaptive motion resulted in extended fatigue. The operational temperature affects the cyclic fatigue resistance of the twisted file.

Evaluation of temperature effect on cyclic fatigue resistance of nickeltitanium instruments in a double-curved canal: a comparative study

“…The main findings of the current study showed that the cyclic fatigue resistances of WOG and EOF at room temperature are more significant than at body temperature (p≤0.05). This is compatible with the aforementioned studies, while the result of previous study which was done by Ismail et al [22], found that there was a nonsignificant difference in cyclic fatigue resistance of WOG at room and body temperatures which is different from the result of current study because of different test that was used.…”

“…So the second null hypothesis was partially rejected. The result of this study showed that the temperature at which the instruments are tested influenced on the results of cyclic fatigue resistance of NiTi files with a different behavior which depends on the heat treatment of the alloy and the type of alloy of the tested endodontic files [22,24]. At (20±1°C), there was non-significant difference in NCF between WOG and EOF.…”

“…These findings might be attributed to the release of the reaction stresses that built up in the material by reversing the rotational direction [26]. Number of studies [22,27] reported that, regardless of the file type, reciprocation motion increased the cyclic fatigue resistance of files more than continuous rotation did. Karatas et al [27], concluded that the fatigue life is associated with the number of times of opening and closing of the crack in an instrument.…”

Effect of body temperature on the cyclic fatigue resistance of the nickel”titanium endodontic instruments: A systematic review and meta-analysis of in vitro studies

“…A total of 21 studies met the criteria for inclusion. [ 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 ]…”

“…The studies revealed differences in the test model type, radius of curvature, angle of curvature, and immersion media. [ 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 ] The distance of the curvature from the tip, the fit of the instrument, angle of insertion, and length of the instrument inserted were not mentioned in all the studies [ Table 1 ].…”