The impact of different surface treatments on the shear bond strength of orthodontic metal brackets applied to different CAD/CAM composites

Abstract

Background: To investigate the shear bond strength (SBS) of orthodontic metal brackets applied to different CAD/ CAM composites treated with different surface treatments. Material and Methods: Specimens of two CAD/CAM composites were obtained of Lava Ultimate (LU; n=60) and Brilliant Crios (BC; n=60) which were randomly separated into six subgroups (n=10) according to the surface treatment: control (CTL); sandblasting (SB); sandblasting and silane (SBSL); hydrofluoric acid (HF); hydrofluoric acid and silane (HFSL); and Monobond Etch&Prime (MEP). The mandibular central incisor metal brackets were bonded with a light-cure adhesive. The SBS data were analyzed using the two-way analysis of variance and Turkey's test, while the adhesive remnant index (ARI) by the Kruskal-Wallis, all the significance was set at 5%. Results: A higher SBS was found for BC in comparison with LU (p < 0.05). All the surface treatments increased the SBS in comparison with CTL (p < 0.0001). Treatment with HF, SBSL and HFSL (p > 0.05) showed a higher SBS, which was followed by MEP and SB (p > 0.05), all in comparison with CTL (p < 0.0001). For ARI, a significant effect was detected only for the surface treatment (p < 0.01), and not for CAD/CAM resin (p > 0.05). Significant differences were detected between CTL to HF, and HF to MEP, as well. Conclusions: The SBS is highly affected by the surface treatment and also by the CAD/CAM composite. The surface treatment improves the SBS and should be encouraged when orthodontic brackets are bonded to CAD/CAM composites.