Adhesive System Effect on Metal Bracket Bond Strength to Different Microhybrid Composite Brands

Abstract

Aim: The aim of this in vitro study was to evaluate the shear bond strength (SBS) of orthodontic metal brackets bonded to microhybrid composite surfaces from different composite brands and to investigate the effects of composite brand and adhesive system on these values. Material and Methods: Two different brands of microhybrid composites (Charisma Smart and Herculite™ Classic) were included in this study. Surfaces received either 37% phosphoric acid etching or diamond-bur roughening. The Trulock adhesive system (Light-Activated Bonding Resin + Adhesive Paste) or the BracePaste system (MTP Primer + Adhesive) was used for bracket bonding, resulting in eight experimental groups (n = 16 per group; total n = 128). Before bond-ing, 10,000 thermal cycles were applied to the specimens; an additional 5,000 cycles preceded SBS testing. After debonding, residual adhesive was scored with the Adhesive Remnant Index (ARI). SBS values were analyzed using the Kruskal–Wallis and Mann–Whitney U tests, whereas ARI score distributions were evaluated using the Fisher–Freeman–Halton exact test with Monte Carlo estimation. Results: The highest mean SBS was obtained with the BracePaste system on bur-roughened Herculite™ Classic (HC) (8.46 ± 1.36 MPa), whereas the lowest occurred with the Trulock sys-tem on acid-etched Charisma Smart (CS) (0.55 ± 0.39 MPa). Bur roughening yielded higher SBS than acid etching for both composite brands. ARI scores differed significantly among the groups (P < 0.001). Conclusions: The composite brand and adhesive system influence bond strength. Clinically, evaluating both with the surface preparation method is critical for successful bonding.