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Interplay between surface characteristics, instrument design, and mechanical behavior of contemporary heat-treated nickel-titanium instruments: an in vitro comparative study
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Tânia Nunes Soares, Emmanuel João Nogueira Leal da Silva, Carlos Nelson Elias, Daniel Guimarães Pedro Rocha, Victor Talarico Leal Vieira
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J Korean Acad Conserv Dent ;Published online October 29, 2026
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DOI: https://doi.org/10.5395/rde.2027.52.e1
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 Abstract
- Objectives
This study aimed to evaluate the surface characteristics and mechanical behavior of contemporary thermally treated nickel-titanium (NiTi) rotary instruments, focusing on the interplay between surface condition, instrument design, and mechanical performance.
Methods
A total of 180 instruments were included (n = 45 per group): TruNatomy Prime (TRN; 26/.04), ProTaper Next X2 (PTN; 25/.06), ProTaper Gold F2 (PTG; 25/.08), and ProTaper Ultimate F2 (PTU; 25/.08). Surface characteristics were assessed qualitatively using scanning electron microscopy and quantitatively by optical profilometry. Mechanical properties, including bending, buckling, cyclic fatigue, and torsional resistance, were evaluated using standardized testing methods. Data were analyzed using one-way ANOVA and the Student-Newman-Keuls post hoc test (α = 0.05).
Results
PTN exhibited significantly higher surface roughness compared to the other systems (p < 0.05). Flexibility was greatest for TRN and lowest for PTN (p < 0.05), whereas buckling resistance and maximum torque were highest for PTG (p < 0.05). Cyclic fatigue resistance was similar among TRN, PTG, and PTU, all outperforming PTN (p < 0.05). Despite marked differences in alloy and design, PTN and TRN showed comparable torsional resistance (p > 0.05). Angular deflection was highest for TRN and lowest for PTN (p < 0.05).
Conclusions
The mechanical behavior of thermally treated NiTi instruments is multifactorial and cannot be explained by alloy type or design alone. Instead, performance reflects the interaction between surface characteristics, geometry, and metallurgical properties. These findings highlight the importance of a comprehensive approach to instrument selection based on the specific mechanical demands of each clinical scenario.
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KACD
