The Effect of Various Types of Mechanical and Chemical Preconditioning on the Shear Bond Strength of Orthodontic Brackets on Zirconia Restorations

The purpose of this study was to investigate the combined effect of mechanical and chemical treatments on the shear bond strength (SBS) of metal orthodontic brackets on zirconia restoration. The zirconia specimens were randomly divided into 12 groups (n = 10) according to three factors: AL (Al2O3) and CO (CoJet™) by sandblasting material; SIL (silane), ZPP (Zirconia Prime Plus), and SBU (Single Bond Universal) by primer; and N (not thermocycled) and T (thermocycled). The specimens were evaluated for shear bond strength, and the fractured surfaces were observed using a stereomicroscope. Scanning electron microscopy images were also obtained. CO-SBU combination had the highest bond strength after thermocycling (26.2 MPa). CO-SIL showed significantly higher SBS than AL-SIL (p < 0.05). CO-ZPP resulted in lower bond strength than AL-ZPP before thermocycling, but the SBS increased after thermocycling (p > 0.05). Modified Adhesive Remnant Index (ARI) scoring and SEM figures were consistent with the results of the surface treatments. In conclusion, CO-SBU, which combines the effect of increased surface area and chemical bonding with both 10-MDP and silane, showed the highest SBS. Sandblasting with either material improved the mechanical bonding by increasing the surface area, and all primers showed clinically acceptable increase of shear bond strength for orthodontic treatment.