[Defects in 2061 discarded ProTaper handfiles after clinical use]

Area of Science:

• Endodontics
• Materials Science
• Dental Instruments

Background:

• Root canal preparation relies on Nickel-Titanium (NiTi) rotary files.
• ProTaper NiTi files are widely used in endodontic procedures.
• Understanding file failure mechanisms is crucial for clinical success.

Purpose of the Study:

• To investigate the failure mechanisms of ProTaper NiTi handfiles after clinical use.
• To identify the types of defects leading to ProTaper handfile failure.
• To correlate failure modes with specific file types and locations.

Main Methods:

• Analysis of 2061 discarded ProTaper handfiles using stereomicroscopy.
• Digital photography and image analysis to measure fracture points.
• Statistical analysis of defect types and fracture rates across different file groups.

Main Results:

• Plastic deformation (unwinding, winding flutes, bending) occurred in 8.2% of files.
• Instrument separation (fracture) was observed in 28.2% of files.
• The F2 file group exhibited the highest fracture rate (41.7%), with fractures averaging 4.4 mm from the tip.

Conclusions:

• Shaping files primarily fail due to torque overload, particularly at the apical region.
• Finishing files are more prone to cyclic fatigue failure, especially in the coronal portion.
• Recognizing these failure patterns aids clinicians in preventing ProTaper handfile breakage during root canal therapy.