Cyclic fatigue comparison among endodontic instruments with similar cross section and different surface coating

Area of Science:

• Endodontics
• Dental Materials Science
• Biomaterials Engineering

Background:

• Rotary endodontic instruments are crucial for root canal preparation.
• Instrument geometry and surface treatments, like titanium-nitride (TiN) coating, can influence fatigue resistance.
• Understanding these factors is vital for preventing instrument fracture during endodontic procedures.

Purpose of the Study:

• To compare the cyclic fatigue resistance of Mtwo and Easy Shape endodontic rotary instruments.
• To analyze the influence of instrument geometry and TiN surface treatment on fatigue fracture.
• To determine if TiN coating affects the cyclic fatigue performance of Easy Shape instruments.

Main Methods:

• 130 Mtwo and Easy Shape rotary instruments of various sizes and tapers were tested for cyclic fatigue resistance.
• Time to fracture (TtF) was measured in a simulated canal (60° angle, 5 mm radius).
• Fracture surfaces were examined using scanning electron microscopy (SEM), and data analyzed with ANOVA and Tukey tests.

Main Results:

• Mtwo instruments demonstrated significantly higher cyclic fatigue resistance (higher number of cycles to fracture - NCF) compared to Easy Shape instruments of the same size and taper.
• Instruments with the same taper showed significantly higher TtF for Mtwo files than Easy Shape files.
• No significant differences in fatigue performance were found between Mtwo and Easy Shape instruments with the same tip size.

Conclusions:

• Mtwo instruments exhibit superior cyclic fatigue resistance due to their smaller core metal volume.
• Titanium-nitride (TiN) coating did not significantly influence the cyclic fatigue performance of Easy Shape instruments in this study.
• Instrument geometry, specifically core design, appears to be a more critical factor than TiN coating for cyclic fatigue resistance in these systems.