Changes in the Surface Area and Volume of Hyflex EDM Instruments after Multiple Uses

Area of Science:

• Endodontics
• Dental Materials Science

Background:

• Nickel-titanium (NiTi) rotary files are widely used in endodontic procedures.
• Understanding the cyclic fatigue and wear of NiTi files is crucial for clinical safety and efficacy.

Purpose of the Study:

• To evaluate the changes in surface area and volume of HyFlex EDM (HEDM) nickel-titanium (NiTi) files after multiple uses.
• To assess the impact of repeated instrumentation on the structural integrity of HEDM files.

Main Methods:

• Micro-computed tomography (micro-CT) was used to analyze HEDM files (10/.05 and 25/.08) before and after use.
• Files were examined after single or multiple root canal preparations in human mandibular molars.
• Surface area and volume measurements were statistically analyzed using Friedman's test and Wilcoxon signed-rank test.

Main Results:

• Intact HEDM files exhibited significantly larger surface areas and volumes compared to used files.
• A consistent and significant reduction in both volume and surface area was observed with an increasing number of uses, irrespective of file size.

Conclusions:

• Repeated use of HEDM NiTi files leads to significant structural alterations, evidenced by decreased surface area and volume.
• Clinicians must be aware of these changes to ensure safe instrument reuse and prevent endodontic treatment failure.