Defects in rotary nickel-titanium files after clinical use

Area of Science:

• Endodontics
• Materials Science
• Dental Instrument Failure Analysis

Background:

• Nickel-titanium rotary endodontic files are widely used in root canal therapy.
• Understanding failure modes is crucial for improving instrument longevity and patient safety.

Purpose of the Study:

• To analyze the types and frequency of defects in nickel-titanium rotary endodontic files after routine clinical use.
• To determine the primary reasons for file failure.

Main Methods:

• Analysis of 378 discarded Quantec Series 2000 nickel-titanium rotary files from a specialist endodontic practice over six months.
• Categorization of defects, including fractures and other non-fracture related issues.

Main Results:

• Almost 50% of files exhibited visible defects.
• 21% of files showed fractures, while 28% had other defects without fracture.
• Torsional fracture accounted for 55.7% of all fractured files, and flexural fatigue for 44.3%.

Conclusions:

• Torsional failure is more frequent than flexural fatigue in clinical use.
• Excessive apical force during instrumentation may lead to torsional failure.
• Use in curved canals might contribute to flexural fatigue failures.