Comparison of Mechanical Characteristics of Three Different Types of Wires for Bonded Lingual Retainer Fabrication

Bonded lingual retainers (BLRs) are essential in orthodontics to maintain post-treatment alignment, particularly for mandibular and maxillary anterior teeth. The mechanical properties of the wires used in BLRs significantly influence their performance and longevity.

This study evaluates the mechanical characteristics of three wire types commonly used in BLRs including Coaxial, Dead Soft, and Multi-Strand Retainer wires.

This in vitro study was description-analytical. A total of 120 extracted human premolar teeth (60 dental double blocks and 60 acrylic blocks) were divided into three groups based on wire type. Teeth were prepared using standard etching and bonding procedures, followed by wire placement and curing. Mechanical tests, including detachment force evaluation, fracture mode analysis, deformation measurement, and pull-out testing were conducted using an Instron Testing Machine. Statistical analysis was performed using SPSS software (version 23.0), employing ANOVA and non-parametric tests where appropriate.

The Dead Soft wire exhibited the highest pull-out force (92.92 N) and detachment force (51.68 N), while the Multi-Strand Retainer wire showed the lowest pull-out force (58.38 N). The Coaxial wire demonstrated the highest deformation (1.34mm), whereas the Dead Soft wire had the least deformation (0.91mm). Fracture mode analysis revealed significant differences among groups; Coaxial wires predominantly exhibited type 3 fractures (90%), while Dead Soft wires had no type 3 fractures.

The Dead Soft wire outperformed other wire types in terms of pull-out and detachment forces, making it a robust choice for BLRs. However, its lower deformation may reduce flexibility under stress. These findings provide valuable insights for orthodontists in selecting optimal wires for BLR fabrication to enhance clinical outcomes and device longevity.