Instrument deterioration with usage: nickel-titanium versus stainless steel

Area of Science:

• Endodontics
• Materials Science
• Dental Instrument Technology

Background:

• Nickel-titanium (NiTi) instruments are suggested to outperform stainless steel in terms of wear resistance and maintaining sharpness.
• However, concerns exist regarding the potential for increased fracture susceptibility in NiTi instruments.

Purpose of the Study:

• To comparatively analyze the wear and breakage patterns of nickel-titanium and stainless steel endodontic instruments.
• To evaluate the durability and failure modes of different types of NiTi and stainless steel files.

Main Methods:

• Sixty endodontic files from three manufacturers, encompassing five types, were subjected to repeated use in curved canals.
• Instruments were examined using scanning electron microscopy (SEM) at intervals to assess wear, fatigue, and breakage.
• Usage was standardized to a maximum of 22 minutes per instrument or until failure.

Main Results:

• Stainless steel instruments exhibited the most rapid wear.
• Nickel-titanium rotary instruments showed intermediate wear, while NiTi hand instruments demonstrated the highest resistance to wear.
• Instrument separation (breakage) was infrequent overall, but nickel-titanium rotary instruments accounted for the majority of fractures.

Conclusions:

• Nickel-titanium instruments, particularly hand-operated types, generally exhibit superior resistance to wear and deterioration compared to stainless steel instruments.
• While nickel-titanium rotary instruments showed a higher incidence of breakage, their overall performance in resisting wear was favorable.