comparison of cyclic fatigue resistance of xp-endo shaper, hyflex cm, flexmaster and race instruments

Background. the aim of this study was to compare the cyclic fatigue resistance of xp-endo shaper, hyflex cm, flexmaster and race rotary instruments at body temperature (37±1°c). methods. twenty xp-endo shaper (#30/.01), 20 hyflex cm (#30/.04), 20 flexmaster (#30/.04) and 20 race (#30/.04) instruments were tested at body temperature (n=20). the instruments were evaluated in artificial canals with a 3-mm radius of curvature and 60° angle of curvature to the center of the 1.5-mm-wide canal. each instrument was rotated until fracture occurred and the number of cycles to failure (ncf) recorded. data were analyzed using one-way anova and tukey hsd tests (p<0.05). results. the difference in the ncf of all the instruments was statistically significant (p<0.05). the order of the instruments from the highest to the lowest ncf was as follows: xp-endo shaper (3064.0±248.1), hyflex cm (1120.5±106.1), flexmaster (569.8±48.4) and race (445.5±53.5). conclusion. under the limitations of the present study, xp-endo shaper instruments were more resistant to cyclic fatigue than the #30/.04 nickel-titanium rotary instruments immersed in water at simulated body temperature.