In-situ nano-silica deposition and air-abrasion with Bioglass 45S5 or aluminium oxide: Effects on methacrylate bonding to yttria-tetragonal zirconia polycrystal

This study aimed at assessing the bonding performance after water storage (24h/6-month) of a methacrylate-based cement applied onto Yttria-Tetragonal Zirconia Polycrystal(Y-TZP) pre-treated using an innovative in-situ silica nanoparticle deposition method and/or air-abrasion with Bioglass 45S5 (BAG) or aluminium oxide (AlO). Pre-sintered blocks of Y-TZP were coated with nano-silica using an experimental in-situ deposition method or used as received (control/silica-free). Air-abrasion was performed with AlO or BAG particles both on silica-coated and control Y-TZP specimens. All the specimens were then analysed using SEM–EDX. Further specimens were treated as described above, bonded using a dual-cure resin cement system and submitted to shear bond strength test after water storage (24h and 6 months). Fracture analysis was subsequently performed using a stereo-microscope. Uniform nano-silica deposition was achieved in the Y-TZP specimens after in-situ silica deposition treatment. However, AlO air-abrasion removed the nano-silica and roughened the Y-TZP surfaces. Conversely, BAG air-abrasion caused partial removal of the nano-silica layer and created only little retention in the control/silica-free Y-TZP specimens. The highest bond strength both at 24h and 6-month water storage was attained with the silica-coated specimens air-abraded with BAG and with those which received no air-abrasion. AlO air-abrasion increased the bond strength (24h) in the Y-TZP specimens compared to the control/silica-free specimens which received no air-abrasion or BAG air-abrasion. The in-situ nano-silica coating method employed in this study may be a suitable, simplified and low-cost approach to provide reliable bond strength to Y-TZP ceramics. No air-abrasion is required after in-situ nano-silica deposition. However, AlO air-abrasion can create micro-retentions on the surface of silica-free Y-TZP ceramics and increases the immediate bond strength of methacrylate-based resin cements.