Mechanical Properties of Heat-Treated NiTi Endodontic Instruments: A Systematic Review

Introduction: Mechanized endodontic treatment represents a continuously evolving advance in dental practice. Objective: To characterize endodontic instruments by scanning electron microscopy and evaluate their mechanical properties, including 45° flexibility, buckling resistance, and Vickers microhardness, in ProTaper systems. Materials and Methods: Ten nickel-titanium instruments from each system were analyzed:

• ProTaper Universal (PTUN)
• ProTaper Gold (PTGO)
• ProTaper Ultimate (PTUL)
• ProTaper Next (PTNE)

Methodology:

1. Structural analysis: Scanning electron microscopy (SEM FEG Quanta FEI 250)
2. Mechanical testing:
   • 45° bending and buckling (EMIC LD 200MF universal testing machine)
   • Vickers microhardness (Micromet 2003 Bueler microhardness tester)
3. Statistical analysis: Shapiro–Wilk test followed by one-way ANOVA (α = 5%)

Results:

1. Flexibility: PTUL > PTGO > PTUN > PTNE
2. Buckling resistance: PTUN > PTGO > PTNE = PTUL
3. Vickers microhardness: PTUN = PTNE > PTGO = PTUL

Conclusion:

• PTUL instruments exhibited the greatest flexibility
• PTUN demonstrated the highest buckling resistance
• Gold Wire technology instruments (controlled memory) showed lower microhardness
• All evaluated systems displayed good surface finish

KEYWORDS: Endodontic instruments; NiTi alloy; flexibility; buckling resistance; Vickers microhardness