Influence of a Bis-GMA-free universal adhesive system on enamel bond strength to ceramic brackets

The aim of this study was to evaluate the shear bond strength and Adhesive Remnant Index (ARI) of ceramic brackets bonded to enamel using a universal adhesive system free of bisphenol A glycidyl methacrylate (Bis-GMA). A total of 100 bovine incisors were divided into 2 groups (n = 50) that received ceramic brackets (Morelli Ceramic or Ice Clear) bonded after acid etching and application of 1 of 5 adhesive systems (n = 10): Adper Single Bond 2, a conventional adhesive system (control group); Scotchbond Universal Plus, a Bis-GMA-free universal adhesive system; and Single Bond Universal, BeautiBond Xtreme, and BeautiOrtho Bond II, all Bis-GMA-containing universal adhesives. Shear bond strength was tested in a universal testing machine (50-kgf load cell; 0.5 mm/min crosshead speed), and the ARI was analyzed under ×20 magnification. Statistical analysis included a generalized linear model with Fisher exact test, Kruskal-Wallis test with post hoc Dunn test, and Mann-Whitney U test; the significance level was set at 5%. No statistically significant differences in shear bond strength were observed among the adhesive systems (P = 0.7821) or their interactions with bracket type (P = 0.5449). A significant difference was found when bracket types were compared (P < 0.0001), with the Morelli Ceramic bracket groups showing the highest bond strengths regardless of the adhesive system used. A significant association between adhesives and the Morelli Ceramic bracket was observed for the ARI score (P = 0.0018), with 100% of specimens in the Scotchbond Universal Plus adhesive group retaining more than half of the resin on the tooth. The Bis-GMA-free universal adhesive system achieved the highest percentage of adhesive retention on the tooth for both bracket types.