Evaluation of porcelain preparation procedures on shear bond strength of steel brackets

The aim of this study was to compare ten porcelain surface preparation procedures for acquiring reliable procedure for steel bracket bonding. This experimental study was conducted with100 steel brackets (3M) bonded to 100 uniform porcelain fused to metal uniform disks by ten different porcelain surface preparation methods with Unite composite. The procedures were: 1) Glazed layer preservation+silane, 2) Glazed layer preservation+phosphoric acid+silane, 3) Glaze removing with diamond bur, 4) Glaze removing with diamond bur+silane, 5) Glaze removing with sandblast, 6) Glaze removing with sandblast+silane, 7) Hydroflouric acid etching, 8) HF etching+silane, 9) combination of 5 and 7, and 10) Combination of 5 and 8. After bonding, samples were preserved in wet environment and then they were thermocycled. Shear bond strength was measured with Dartec machine. Surface of samples were evaluated under light microscope after bracket removal. Comparison of shear bond strengths was done by one way ANOVA and Dunnett’s C tests. For evaluation of fracture pattern and the quality of porcelain surface after bracket removing, Kruskal Walis and Manwitney tests were used. Adequate shear bond strength was not attained by 1st, third and fifth procedures. Other procedures can produce adequate or extra shear bond strength in orthodontic needs. Only in two groups, damage to porcelain was zero or minimum (P<0.0005) and damage was higher in other groups. Results showed two reliable procedures (second and seventh procedures) for bonding of steel brackets to porcelain especially in anterior regions that undamaged porcelain is critical.