In Vivo Comparison of Ultimate Tensile Strength and Surface Topography of Three Different Nickel–Titanium Archwires

Abstract

Objective: To investigate the surface topography and ultimate tensile strength of 3 types of nickel–titanium (NiTi) wires before and after 3 months of intraoral use and to assess the efficiency of the wires in cases requiring extensive alignment. Methods: NiTi wires of 0.016″ (0.40 mm) were divided into 3 groups—martensitic stabilized NiTi™ (group 1), austenitic active Copper NiTi™ 27°C (group 2), and martensitic active copper NiTi™ 35°C (group 3)—each further divided into 2 subgroups: (a) as-received wires; and (b) used wires. Each wire was subjected to scanning electron microscopy (SEM) analysis and tensile testing. Ultimate tensile strength data were analyzed using one-way analysis of variance (ANOVA) and Tukey testing at the .05 level of significance. Results: Martensitic stabilized archwires had a significantly lower ultimate tensile strength (93.99 ± 0.23 MPa) than martensitic active (116.96 ± 0.43 MPa) and austenitic active (106.94 ± 0.36 MPa) archwires. Among the used archwires, the martensitic stabilized ones showed the most and the martensitic active ones the least surface degradation. Conclusion: Ultimate tensile strength was the highest for martensitic active archwires with superior surface properties and the lowest for martensitic stabilized archwires with an increased amount of surface degradation.