Bond strength of metal brackets bonded to a silica-based ceramic with light-cured adhesive Influence of various surface treatment methods

Objective The purpose of this work was to evaluate the effects of several surface treatment methods on the shear bond strengths of metal brackets bonded to a silica-based ceramic with a light-cured adhesive. Materials and methods Silica-based ceramic (IPS Classic (R)) with glazed surfaces was cut into discs that were used as substrates. A total of 80 specimens were randomly divided into four groups according to the method used: 9.6 % hydrofluoric acid (group 1), 9.6 % hydrofluoric acid (HF) + silane coupling agent (group 2), sandblasting (aluminum trioxide, 50 mu m) + silane (group 3), and tribochemical silica coating (CoJet (TM) sand, 30 mu m) + silane (group 4). Brackets were bonded to the treated specimens with a light-cure adhesive (Transbond XT, 3 M Unitek). Shear bond strength was tested after bracket bonding, and the Adhesive Remnant Index (ARI) scores were quantified after debonding. Results Group 4 showed the highest bond strength (12.3 +/- 1.0 MPa), which was not significantly different from that of group 3 (11.6 +/- 1.2 MPa, P > 0.05); however, the bond strength of group 4 was substantially higher than that of group 2 (9.4 +/- 1.1 MPa, P < 0.05). The shear bond strength of group 1 (3.1 +/- 0.6 MPa, P < 0.05) was significantly lower than that of the other groups. Conclusion Shear bond strengths exceeded the optimal range of ideal bond strength for clinical practice, except for the isolated HF group. HF acid etching followed by silane was the best suited method for bonding on IPS Classic (R). Failure modes in the sandblasting and silica-coating groups revealed signs of damaged ceramic surfaces.