Evaluation of the effect of temperature on cyclic fatigue resistance of three types of Nickel-Titanium rotary files with various alloy properties: An in vitro study

Abstract

Background and objectives: the fracturing of nickel-titanium rotary instruments during endodontic treatment because of the cyclic fatigue remains a common incidence. This study evaluated the effect of temperature on the cyclic fatigue of various nickel-titanium rotary files and compare between them. Methods: Three types of rotary instruments with tip size 0.25 were used: HyFlex EDM (OneFile, variable taper, Colten/Whaledent), ProTaper Gold (F2, 0.08 taper, Dentsply) and 2Shape (TS2, 0.06 taper, Micro-Mega). Twenty files for each instrument were tested for cyclic fatigue at (20°C and 37°C) temperatures and rotated until fracture occurred in a simulated canal with an angle curvature of about 60°, a radius curvature of 5 mm, and a canal width of 1.5 mm. Six groups were formed for all instruments (total number = 60), with ten files in each group. The number of cycles to fracture was recorded, and statistical analysis was completed using analysis of variance and independent t-test with significance at a (P<0.05). Results: HyFlex EDM OneFile registered no differences in fatigue life between the 2 temperatures tested (P > .05), whereas ProTaper Gold F2 and 2Shape TS2 showed a statistically significant reduction in fatigue life at body temperature compared with room temperature (P <0.05). HyFlex EDM OneFile exhibited statistically higher resistance to cyclic fatigue than ProTaper Gold F2 and 2Shape TS2 both at room and body temperatures (P<0.05). Conclusions: Within the limitations of this study, body temperature influenced the cyclic fatigue resistance of ProTaper Gold F2 and 2Shape TS2 files, whereas it did not influence the fatigue life of HyFlex EDM OneFile. The HyFlex EDM OneFile was more resistant to cyclic fatigue than the ProTaper Gold F2 and 2Shape TS2 files at room and body temperatures.

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

“…Six studies were included,[ 29 30 31 32 33 34 ] examining 10 different instrument types, including the ProTaper Gold (Dentsply Sirona, Charlotte, NC, USA), EdgeFile (EdgeEndo, Albuquerque, NM), Vortex Blue (Dentsply Sirona, Charlotte, NC, USA), Reciproc Blue (VDW, Munich, Germany), HyFlex EDM (Coltene, Cuyahoga Falls, OH, USA), WaveOne Gold (Dentsply Sirona, Charlotte, NC, USA), Twisted File Adaptive (TFA) (SybronEndo, CA, USA), X1 Blue (MK Life, Porto Alegre, RS, Brazil), 2Shape (MicroMega, Besancon, France), and One Curve (MicroMega, Besancon, France). Three of these systems were reciprocating while one had an adaptive (rotation–reciprocating) motion.…”

“…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 ].…”

“…Six studies were selected with similar study designs, instrument characteristics, and outcome measures to achieve homogeneity. [ 29 30 31 32 33 34 ] A meta-analysis was performed, which discovered that the cyclic fatigue resistance of heat-treated NiTi endodontic instruments is significantly reduced at body temperature. This can be attributed to the alloy transitioning to the austenitic phase in heat-treated instruments.…”