| Objective: The purpose of this study was to investigate the influence of different silane coupling agents and different adhesive materials to the shear bond strength of metal brackets bonded to porcelain surface,and provide evidence for clinical practice.Methods: 120 porcelain specimens were deglazed by 1000 grit water sandpaper and etched with 9.6%HF acid for 120s, rinsed with distilled water and dried before applying the silane primer. All specimens were divided randomly into 3 groups according to different silane coupling agents application, the first group was treated with one-mix silane coupling agent, the second group was treated with two-mix system, the third group was treated without silane primer as control group. Each group was subdivided into 4 subgroups depending on different adhesive material, every subgroup had 10 porcelain facets. 120 metal brackets were bonded to ceramic specimens with 4 adhesive material: light-cured composite resin(A), one-component chemically cured composite resin(B),resin-modified light-cured glass ionomer cements(RMGIC) (C), two-component chemically cured resin adhesive(D). All specimens were stored in artificial saliva bath at 37℃for 24 hours. after brackets bonded for 60min, then the specimens underwent shear testing with Instron universal testing machine. Shear bond strength were measured, a two-way analysis of variance and LSD-t tests were run on the data. Porcelain Fracture Index (PFI)were recorded after shearing. Kruskal-Wallis H test and Nemenyi test were used to analysis PFI.Results: The shear bond strength of the groups treated with silane primer were higher than that without silane primer (p<0.05).There was not any statistically significant in the shear bond strength between the group of one-mix silane coupling agent and the group of two-mix silane coupling agent (p>0.05). The shear bond strength of the group with light-cured composite resin was higher than the others (p<0.05). The shear bond strength of the group with RMGIC was lower than the others (p<0.05). There were not statistically significant (p>0.05) in the shear bond strength between the group with one-component chemically cured composite resin and the group with two- component chemically cured composite resin. The group of light-cured composite resin treated with two-mix silane coupling agent showed the highest shear bond strength. The group of RMGIC treated without silane coupling agent showed the lowest shear bond strength There was a interactive relation between the two factors (p<0.05). There were statistically significant (p<0.05) between porcelain fracture of these groups. The groups treated without silane coupling agent showed lower porcelain fracture than the groups treated with silane coupling agent.Conclusions: Silane coupling agent can improve the shear bond strength between metal brackets and porcelain surface. There were not statistically significan between one-mix silane coupling agent and two-mix system. The group of light-cured composite resin treated with two-mix silane coupling agent can get the highest shear bond strength. Resin-modified light-cured glass ionomer cements (RMGIC) was not a suitable adhesive to bond metal brackets onto porcelain surface.
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