Evaluation of single-use rotary nickel-titanium instruments

Area of Science:

• Endodontics
• Dental Materials Science
• Biomaterials Engineering

Background:

• Rotary nickel-titanium instruments are widely used in endodontics.
• Understanding instrument failure modes is crucial for patient safety and treatment efficacy.
• Single-use protocols are debated for rotary endodontic instruments.

Purpose of the Study:

• To analyze the incidence and types of defects in single-use ProFile Series 29 rotary nickel-titanium instruments.
• To evaluate defect rates across different instrument sizes after one clinical use.
• To determine if experienced clinicians influence the defect rate of new instruments.

Main Methods:

• Collected 786 new ProFile Series 29 .04 taper nickel-titanium instruments used over 4 weeks.
• Instruments were used with standard protocols (crown-down, lubrication, irrigation) in a specific air motor.
• Post-use, instruments underwent ultrasonic cleaning, sterilization, and inspection at 16x magnification for defects.

Main Results:

• 14.63% of instruments (115/786) exhibited defects after a single clinical use.
• Size 3 instruments showed the highest defect rate (22.66%), with no statistically significant difference between sizes 2-5.
• Instrument fracture occurred in 0.891% (7/786) of cases, with no significant difference in failure type by size.

Conclusions:

• Defects are common in single-use rotary nickel-titanium instruments, even when new and used by experienced clinicians.
• The findings support a single-use protocol for these instruments to ensure absolute safety.
• Further research could explore long-term cyclic fatigue and torsional resistance of various instrument designs.