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Isolating design variables by assessing the impact of cross-section geometry on the mechanical performance of
Anne Rafaella Tenório Vieira1, Guilherme Ferreira da Silva1, Emmanuel João Nogueira Leal da Silva2,3
1Department of Operative Dentistry, Endodontics, and Dental Materials, Bauru School of Dentistry, University of São Paulo - USP, Bauru, Brazil.
Objectives:
This study aimed to assess the effect of cross-section geometry on the mechanical properties of nickel-titanium (NiTi) instruments by comparing two instruments with identical tip size, taper, and thermal treatment but differing in cross-section design.
Methods:
One hundred four NiTi rotary instruments, being S-shaped and triangular cross-section, manufactured with Blueish thermal treatment, were tested (n = 52 per group). Differential scanning calorimetry was employed, and the metal mass volume and cross-section area were assessed. The cyclic fatigue, torsional, and bending resistance tests were assessed. Data were analyzed using the Kolmogorov-Smirnov and Student t tests, and the level of significance was set at 5%.
Results:
The instruments exhibited similar start and finish temperatures of phase transformation. The S-shaped instruments had significantly lower metal mass volume and cross-sectional area (p < 0.05). S-shaped instruments demonstrated superior cyclic fatigue resistance, greater angular deflection, and lower bending stiffness (p < 0.05).
Conclusions:
Cross-section geometry significantly influences the mechanical properties of NiTi rotary instruments.
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