Comprehensive Assessment of Cyclic Fatigue Strength in Five Multiple-File Nickel-Titanium Endodontic Systems

Area of Science:

• Endodontics
• Materials Science
• Biomedical Engineering

Background:

• Nickel-titanium (NiTi) endodontic instruments are prone to cyclic fatigue failure.
• Understanding instrument characteristics is crucial for clinical success and patient safety.

Purpose of the Study:

• To evaluate the cyclic fatigue resistance of five NiTi rotary systems.
• To correlate fatigue strength with geometric and metallurgical properties.

Main Methods:

• Mechanical testing of 250 instruments from five systems (ProTaper Gold, ProTaper Universal, Premium Taper Gold, Go-Taper Flex, U-Files).
• Analysis of design (spirals, angle), surface finishing (SEM), phase transformation (DSC), and elemental composition (EDS).
• Cyclic fatigue testing in a simulated canal (6mm radius, 86° curvature).

Main Results:

• Design characteristics varied among systems; U-Files and Premium Taper Gold had smoother surfaces.
• All instruments showed near-equiatomic NiTi composition; ProTaper Universal and U-Files had lower transformation temperatures.
• Larger instruments, ProTaper Universal, and U-Files exhibited lower cyclic fatigue strength.

Conclusions:

• Significant variations exist in NiTi endodontic instrument design, metallurgy, and cyclic fatigue performance.
• These findings aid clinicians in selecting instruments for improved safety and efficacy in root canal therapy.