The aim of this study was to compare the shear bond strength and Adhesive Remnant Index of four different veneering ceramic materials to metal brackets. Additionally, it should be examined whether it is possible to overcome the etching method using hydrofluoric acid which is noxious. Instead of this treatment, air particle abrasion with 25 μm aluminium trioxide, silane coupling application and etching with 37.0 per cent orthophosphoric acid as pre-treatment procedures of the veneering ceramics before bonding was investigated. Two surface conditioning methods of four ceramic materials before bonding brackets were examined: in group 1 an air particle abrasion with 25 μm aluminium trioxide (4 seconds at a pressure of 2.5 bars) and subsequently a silane coupling agent (Espe Sil, 3M Unitek, Monrovia, USA) was applicated on one side of each ceramic specimen (10 per group). In group 2 one side of each sample (10 per group) was etched with 37.0 per cent orthophosphoric acid for two minutes and was followed by a silane application (Espe Sil, 3M Unitek, Monrovia, USA). After this procedure the self-ligating metal brackets SmartClip (3M Unitek, Monrovia, USA) brackets were bonded to the ceramic blocks and a thermocycling process started (5°C - 55°C, 6000 cycles). Then, shear bond strength and Adhesive Remnant Index (ARI) were measured. To determine statistical differences Oneway-ANOVA and Tukey Post-hoc test were performed. The level of significance was set at α = 0.05. On the basis of the results of the current study, it could be concluded that sandblasting with 25 μm aluminium trioxide and the use of orthophosphoric acid (37.0 per cent) seem to prepare the surface of the ceramic restoration sufficiently before bracket bonding. The found level of shear bond strength values seem be sufficient for bracket bonding. Hydrofluoric acid seems not to be justifiable anymore for preparing the surface of dental ceramic restorations before bracket bonding.
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