Comparative evaluation of the performance of orthodontic retainers using different surface protocols: an in vitro study

Abstract

This study aims to assess the in vitro durability of Nitinol retainers, manufactured using computer-aided methods with hydrophilic or superhydrophilic surfaces to reduce debonding, alongside a commonly used composite adhesive. The 112 lower incisor teeth were embedded in blocks in pairs. Retainer wires were made up of 0.018 × 0.018 inch Nickel Titanium alloy(G4™ Nickel Titanium G&H Orthodontics, USA) by bending a robot arm. A total of 16 teeth(8 blocks) were used for each of the mentioned 7 groups Ni-Ti Retainer; Laser Textured Ni-Ti Retainer; Laser Texturing and Atmospheric Plasma Applicated Ni-Ti Retainer; Atmospheric Plasma Applicated Ni-Ti Retainer; Laser Texturing and Atmospheric Plasma Applicated Ni-Ti Retainer*2; Laser Texturing and Atmospheric Plasma Applicated Ni-Ti Retainer*3; SS-0.0018"(Morelli, Brazil). Transbond LR(3 M Unitek, California) was used. The shear bond strength tests were conducted. The Kruskal-Wallis H test was employed, pairwise comparisons followed by Dunn's test with Bonferroni correction as a post-hoc analysis. There was no statistically significant difference between the groups for maximum force and maximum stress(p > 0.05). However, a significant difference was found in maximum elongation (p:0.0023). Pairwise comparisons highlighted significantly higher elongation values in the SS-0.0018" group. The stainless-steel wire demonstrated higher elongation values, which may offer clinical advantages in cases with higher occlusal forces and periodontal problems due to its material flexibility. Laser Texturing and Atmospheric Plasma Applied Ni-Ti Retainers exhibited higher test performance. Surface treatments applied to CAD/CAM retainers can provide an advantage by enhancing bond strength, potentially reducing the risk of debonding. These findings underline the importance of material selection and surface treatments in optimizing fixed retention strategies for long-term clinical success.

Keywords: Atmospheric plasma; Computer-aided design/computer-aided manufacturing; Fixed lingual retainers; Laser surface texturing; Permanent retantion.

Fig. 1

This figure shows the CAD models of fixed orthodontic retainers, displaying the detailed structure and components used in the study. R-1: 0.018 × 0.018 inch Nickel Titanium alloy (G&H Orthodontics, USA) Ni-Ti Retainer; R-2: 0.018 × 0.018 inch Nickel Titanium alloy(G&H Orthodontics, USA) Laser Textured Ni-Ti Retainer, R-3: 0.018 × 0.018 inch Nickel Titanium alloy(G&H Orthodontics, USA) Laser Texturing and Atmospheric Plasma Applicated Ni-Ti Retainer, R-4: 0.018 × 0.018 inch Nickel Titanium alloy(G&H Orthodontics, USA) Atmospheric Plasma Applicated Ni-Ti Retainer, R-5: SS − 0.0018” (Morelli, Brazil), R-6:0.018 × 0.018 inch Nickel Titanium alloy(G&H Orthodontics, USA) Laser Texturing and Atmospheric Plasma Applicated Ni-Ti Retainer*2, R-7: 0.018 × 0.018 inch Nickel Titanium alloy(G&H Orthodontics, USA). Laser Texturing + Atmospheric Plasma Applicated Ni-Ti Retainer*3

Fig. 2

This figure illustrates the design of the testing retainer including the placement protocol used for the tests

Fig. 3

Demonstration of the process of applying bending forces to the retainers, showing the setup and how the retainers were subjected to stress in the experimental conditions

Fig. 4

The moment of debonding during the testing procedure