Cyclic fatigue resistance of two NiTi rotary instruments after blue heat treatment.

BACKGROUND

This study evaluated the cyclic fatigue resistance of two blue heat-treated rotary instruments. Thirty files (15 Eflex Blue and 15 BlueShaper) activated by an E-CONNECT motor at 350 RPM with a 2.5 N torque were evaluated.

MATERIAL AND

METHODS

A stainless-steel device with three different curvatures (25°, 45°, and 90°) was fixed to a SHIMADZU tensile testing machine to measure cyclic fatigue. The instruments were placed on the motor at a constant speed, then on the testing device; the time to each instrument's fracture was recorded. Tension, time, and instrument deformation were measured. Data were analyzed using the Shapiro-Wilk and Kruskal-Wallis tests at a 5% significance level.

RESULTS

Eflex Blue files demonstrated superior tensile strength and stability over time, particularly at a 25° curvature (p < 0.05). Performance was comparable between the two files at 45° and 90° curvatures, with no significant differences in deformation percentage.

CONCLUSIONS

Eflex Blue files demonstrated greater cyclic fatigue resistance than BlueShaper, especially at smaller curvatures (25°). Although both systems exhibited similar deformation rates, the fracture resistance of both files decreased as curvature increased, reaching a critical threshold at 90°.