Objectives: The aim of this study was to evaluate the reactions of silanes prior to attaching the composite to titanium and evaluate these silanes as coupling agents. Veneered titanium may be used as a prosthetic material.
Methods: Two silane solutions, a mixture of both gamma-methacryloxypropyltrimethoxysilane and vinyltriisopropoxysilane, and tris(3-trimethoxysilylpropyl)isocyanurate were prepared as 2 wt% in two different (95% 2-propanol and 90% acetone) solutions. A control, 2 wt% gamma-methacryloxypropyltrimethoxysilane was prepared in both solutions. These six silane solutions were applied onto flat titanium surfaces. The samples (N = 250) were divided into two main groups: air-dried (room temperature) and heat cured for 1 h at 110 degrees C. Sinfony veneering composite was applied and light-cured on the titanium. The control group was non-silanized. The specimens were assigned to two subgroups: not thermocycled, and thermocycled (5000 cycles, 5-55 degrees C). Shear bond strength of the composite was tested at a crosshead speed of 1.0 mm min(-1). Fresh silane solution hydrolysis, and condensation reaction on titanium surface were monitored by FTIR spectrometry.
Results: Dry samples could be successfully tested, while thermocycling after 3700 cycles had gradually de-bonded the composite from the silanized titanium substrate. For dry samples, statistical analysis (ANOVA) showed that solvent and silane significantly affected the shear bond strength. The silane mixture in 2-propanol reacted at room temperature yielded 11.3 MPa (Standard deviation, SD, 3.6 MPa) and on the other hand, tris(3-trimethoxysilylpropyl)isocyanurate in 2-propanol yielded 10.7 MPa (SD 8.0 MPa) and gamma-methacryloxypropyltrimethoxysilane 20.4 MPa (SD 12.2 MPa). Non-silanized samples yielded 4.8 MPa (SD 2.1 MPa).
Significance: In all solvents used, silanes reacted chemically with the titanium surface and covalent Si-O-Ti- and -Si-O-Si- bonds were evident.