Promotion of adhesion between resin and silica-coated titanium by silane monomers and formic acid catalyst

Three bifunctional silane coupling agent monomers and their blends with a cross-linking silane were investigated as six experimental adhesion-promoters in vitro. Three organosilane monomers, 3-methacryloxypropyltrimethoxysilane, styrylethyltrimethoxysilane, and 3-(N-allylamino)propyltrimethoxysilane, were prepared as 1% (v/v) primers and also blended with a cross-linking silane, 1,2-bis-(triethoxysilyl)ethane at 0.5% (v/v), in a 95:5 solution of ethanol in deionized water. The silanes were allowed to hydrolyze using formic acid as catalyst and were applied to a substrate of silica-coated Ti. The control was a pre-hydrolyzed silane coupling agent that is commonly used in dentistry. An experimental unfilled bis-phenol-A-diglycidyldimethacrylate/methylmethacrylate resin was bonded by photo-polymerization as stubs to the prepared Ti. Half of the specimens were artificially aged by wet thermo-cycling and half were stored in dry conditions in a desiccator. Storage conditions and the type of primer silane or blend significantly affected shear bond strength values. 3-Methacryloxypropyltrimethoxysilane, alone or blended, produced significantly higher shear bond strength values than the control, both after dry storage and after thermo-cycling.