Bond Strength of Universal Self-Etch 1-Step Adhesive Systems for Orthodontic Brackets

Objective: The objective of this study was to assess the shear bond strength (SBS) of orthodontic brackets bonded to uncut enamel with universal self-etch 1-step adhesive systems. Methods: Extracted uncut premolars (n = 160) were randomly divided into 4 groups for treatment with Scotchbond Universal Adhesive (SU), All-Bond Universal (BU), Clearfil Universal Bond (CU) or the control, Adper Scotchbond Multi-Purpose Adhesive. Following bonding of brackets on tooth surfaces, teeth were stored in distilled water for 24 h and 6 months, and brackets were tested for SBS. The adhesive remnant index (ARI) and quantitative percentage of remaining resin (%RR) were recorded. Scanning electron microscopy was used to analyze debonded surfaces qualitatively. SBS and %RR data were analyzed by 2-way ANOVA followed by the Tukey test (a = 0.05). Results: At neither time did these universal adhesives achieve satisfactory SBS for orthodontic treatment. The control group had the highest SBS, ARI score and mean %RR (and these differences were significant), while the BU group had the lowest SBS. SBS mean values and ARI scores decreased over time for SU and BU, but remained stable for CU. There was no difference in %RR among the universal adhesives tested. Conclusion: None of the universal adhesives used in self-etch mode achieved SBS values (at 24 h and 6 months) that were satisfactory for orthodontic treatment.