Fractographic analysis of separated endodontic file designs

Area of Science:

• Materials Science
• Biomaterials Engineering
• Dental Materials

Background:

• Endodontic rotary files are crucial for root canal procedures.
• File separation failure is a significant clinical concern.
• Understanding failure mechanisms is essential for improving instrument reliability.

Purpose of the Study:

• To investigate the fractographic characteristics of endodontic rotary files.
• To correlate fracture analysis with Weibull reliability determination.
• To identify factors contributing to file separation failure.

Main Methods:

• Controlled, dynamic testing of commercial rotary files to failure.
• Ex vivo testing of three distinct file designs with standardized dimensions.
• Fractographic analysis using scanning electron microscopy (SEM) and Weibull statistical analysis.

Main Results:

• Significant statistical differences in the number of cycles to failure (NCF) among file designs (p < 0.001).
• Fractographic analysis identified separation fractures, inclusions, fatigue striations, and stress concentrations.
• Weibull moduli were statistically equivalent across groups, indicating similar reliability trends despite NCF differences.

Conclusions:

• Cyclic fatigue failure in rotary files is governed by stress concentration points and defect distribution, irrespective of design.
• Apical fragments showed statistically significant differences related to file design.
• Modifications to working edges and surface finish could potentially reduce failures by minimizing stress concentrations and initiating cracks.