INTRODUCTION: This in vitro study compared the cyclic fatigue resistance of ProFile Vortex rotary instruments (DENTSPLY Tulsa Dental, Tulsa, OK) made of two different raw materials: M-Wire and regular superelastic wire (SE-wire) at two different rotational speeds. Two rotary-based Profile Vortex instruments with taper 0.04 and 0.06 (25 mm in length and #30 in size) were compared. METHODS: Cyclic fatigue testing was performed by rotating instruments in an artificially constructed stainless steel canal with a 5-mm radius and a 90 degrees angle of curvature at two different test frequencies: 300 and 500 rpm. The time to failure was recorded, and the total number of cycles to failure was calculated and compared for a total of 160 samples. Statistical analysis was performed with one-way analysis of variance and the Tukey test for individual comparisons (confidence level of p < 0.05). Fracture surfaces of broken instruments were also observed under scanning electron microscopy. Over 50% of broken files made of SE-wire exhibited multiple crack initiation sites compared with the single crack initiation on files made of M-Wire. RESULTS: Overall, there were significant differences in rotary instruments made of different materials (p < 0.001). However, for rotary instruments made from the same material (either M-Wire or SE-wire), there was no significant difference (p > 0.05) of cyclic fatigue life under different rotational speeds (300 and 500 rpm). CONCLUSIONS: ProFile Vortex files made of M-Wire exhibited superior cyclic fatigue resistance (approximately 150% longer in fatigue life) compared with those made of regular SE-wire at two test frequencies (300 and 500 rpm). Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.
INTRODUCTION: This in vitro study compared the cyclic fatigue resistance of ProFile Vortex rotary instruments (DENTSPLY Tulsa Dental, Tulsa, OK) made of two different raw materials: M-Wire and regular superelastic wire (SE-wire) at two different rotational speeds. Two rotary-based Profile Vortex instruments with taper 0.04 and 0.06 (25 mm in length and #30 in size) were compared. METHODS: Cyclic fatigue testing was performed by rotating instruments in an artificially constructed stainless steel canal with a 5-mm radius and a 90 degrees angle of curvature at two different test frequencies: 300 and 500 rpm. The time to failure was recorded, and the total number of cycles to failure was calculated and compared for a total of 160 samples. Statistical analysis was performed with one-way analysis of variance and the Tukey test for individual comparisons (confidence level of p < 0.05). Fracture surfaces of broken instruments were also observed under scanning electron microscopy. Over 50% of broken files made of SE-wire exhibited multiple crack initiation sites compared with the single crack initiation on files made of M-Wire. RESULTS: Overall, there were significant differences in rotary instruments made of different materials (p < 0.001). However, for rotary instruments made from the same material (either M-Wire or SE-wire), there was no significant difference (p > 0.05) of cyclic fatigue life under different rotational speeds (300 and 500 rpm). CONCLUSIONS: ProFile Vortex files made of M-Wire exhibited superior cyclic fatigue resistance (approximately 150% longer in fatigue life) compared with those made of regular SE-wire at two test frequencies (300 and 500 rpm). Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.