Cyclic fatigue resistance of four different nickel-titanium instruments in an artificial canal

Abstract

Introduction: The objective of this study was to measure the number of cycles to fracture of four continuous or reciprocating rotary nickel-titanium instruments in different materials. Methods: A total of 40 nickel-titanium instruments were used for the present study. Instruments were divided into four groups (n=10): group 1, Revo-S SU; group 2, ProTaper Next X2; group 3, Reciproc R25; group 4, WaveOne Gold Primary. An artificial stainless-steel was used to test the cyclic fatigue of the instruments. The instruments were introduced into the stainless-steel canal, one at a time, until they reached the other end, then they were rotated inside the canal without in-out motion. The time from the beginning of instrument rotation until the occurrence of breakage was recorded. The number of rotated cycles to fracture of the instrument were calculated based on the revolutions per minute (rpm) of each instrument and the recorded rotated time. The mean number of cycles to fracture and standard deviations were calculated and statistically analysed. Results: The number of cycles to fracture of the Revo-S SU was the lowest, and that of the WaveOne Gold Primary was highest. Scanning electronic microscope images of fracture surfaces revealed the characteristics of fatigue. Conclusions: The number of cycles to fracture of the reciprocating WaveOne Gold Primary system was the highest amongst the tested instruments.