Comparative Evaluation of Mechanical Performance among Fixed Orthodontic Retention Wires

Abstract

Background: The biomechanical reliability of fixed orthodontic retainers is integral to achieving durable post-treatment stability. With a broad spectrum of multistranded stainless-steel wire designs available in contemporary orthodontics, a rigorous and evidence-based assessment of their mechanical performance is essential to guide clinical decision-making. This in vitro investigation provided a systematic and analytically robust evaluation of four clinically utilized retainer wire configurations, emphasizing tensile strength, yield strength, and modulus of elasticity—parameters that fundamentally determine structural integrity and long-term functional behavior.
Methods: Seventy-six multistranded stainless-steel wires were allocated into four groups (n = 19): Group 1 (7-stranded, 0.0175”), Group 2 (6-stranded, 0.0195”), Group 3 (6-stranded, 0.0175”), and Group 4 (5-stranded, 0.0175”). Each specimen underwent monotonic tensile loading using an Instron Universal Testing Machine (TEQIP-II) under standardized laboratory conditions. The resulting load–deflection curves were examined to determine the modulus of elasticity and yield strength. Intergroup statistical comparisons were conducted using one-way ANOVA followed by Tukey’s HSD post-hoc test, with significance established at p < 0.05.
Results: Significant intergroup differences were identified for all evaluated mechanical parameters. The 7-stranded 0.0175” wire (G&H) displayed the most advantageous mechanical profile, demonstrating the highest tensile capacity, increased yield strength, and superior stiffness. The 6-stranded 0.0175” (Optima) and the 6-stranded 0.0195” (OrthoClassic) wires exhibited intermediate performance, whereas the 5-stranded 0.0175” wire (Acti 5S) presented distinctly inferior biomechanical characteristics.
Conclusion: Within the limitations of an in vitro design, the 7-stranded 0.0175” configuration emerges as the most mechanically robust and clinically advantageous option for sustained orthodontic retention, while the 5-stranded 0.0175” wire demonstrates markedly reduced structural competence.