Two organofunctional silane coupling agents alone and two silane blend systems with HEMA were evaluated in vitro as adhesion promoters for bonding bis-GMA resin to a silica-coated titanium surface. The silanes were applied onto tribochemically silica-coated titanium surfaces. Experimental bis-GMA resin stubs were applied and photo-polymerized onto titanium. The specimens were subjected to three different conditions: (1) dry storage for 24 h, (2) storage in de-ionized water at 37 degrees C for six months and (3) alternating storage in de-ionized water at 37 degrees C and thermocycling (6000 cycles, 5-55 degrees C) for 6 months. Shear bond strengths of the resin to titanium were measured using a universal testing machine. Surface examination was made with a scanning electron microscope (SEM) after the bond strength test. Highest shear bond strength was obtained with 3-acryloxypropyltrimethoxysilane stored in dry condition (20.2 +/- 3.2MPa), and the lowest value was obtained with 3-methacryloxypropyltrimethoxysilane (ESPE Sil) in alternating water storage and thermocycling condition (1.4 +/- 0.6 MPa). The type of storage condition affected significantly the shear bond strength (p < 0.05). The shear bond strength obtained from dry storage was the highest, while the shear bond strength obtained from alternating water storage and thermocycling condition was the lowest. Interfacial failure was the main failure mode (87.2%) followed by mixed failure (9.4%) and cohesive failure (3.4%). The addition of 0.5 vol%. HEMA into silane primers did not improve the shear bond strength between the experimental resin and silica-coated titanium. (C) Koninklijke Brill NV, Leiden, 2012