Methacrylate bonding to zirconia by in situ silica nanoparticle surface deposition

• A novel method to deposit nano-silica onto yttria-stabilized zirconia ceramic and improve bonding of methacrylate-based materials is described.
• The zirconia and silica precursors used in this study are safe, non-toxic, and reasonably inexpensive.
• The application technique could use the sintering time and temperature used to process or glaze dental ceramics.
• Primers with silica/zirconia content of 25:75 can favour the establishment of a stable bond more resistant to hydrolytic degradation.

ObjectiveThis study introduces an innovative method to enhance adhesion of methacrylate-based cements to yttria-stabilized zirconia (Y-TZP) by means of a silica-nanoparticle deposition process.MethodsTwo alkoxide organic precursors, tetraethyl-orthosilicate (TEOS) and zirconium tert-butoxide (ZTB) were diluted in hexane at different concentrations in order to obtain several experimental materials to enhance deposition of a SiOx reactive layer to Y-TZP. This deposition was attained via sintering alkoxide precursors directly on pre-sintered zirconia (infiltration method—INF) or application on the surface of fully sintered zirconia (coating method—COA). Untreated specimens and a commercial tribochemical silica coating were also tested as controls and all the treated Y-TZP specimens were analyzed using SEM-EDX. Specimens were bonded using silane, adhesive and dual-cure luting cement and submitted to shear bond strength test after different water storage periods (24 h, 3-, 6- and 12-months).ResultsSEM-EDX revealed Y-TZP surface covered by silica nanoclusters. The morphology of silica-covered Y-TZP surfaces was influenced by sintering method, employed to deposit nanoclusters. High bond strength (MPa) was observed when using COA method; highest TEOS percentage achieved the greatest bond strengths to Y-TZP surface (36.7 ± 6.3 at 24 h). However, bonds stability was dependent on ZTB presence (32.9 ± 9.7 at 3 months; 32.3 ± 7.1 at 6 months). Regarding INF method, the highest and more stable resin–zirconia bond strength was attained when using experimental solutions containing TEOS and no ZTB. Both sintering methods tested in this study were able to achieve a bonding performance similar to that of classic tribochemical strategies.SignificanceThis study demonstrates that it is possible to achieve a reliable and long-lasting bonding between yttria-stabilized zirconia ceramic and methacrylate-based cements when using this novel, simple, and cost-effective bonding approach.