Shear bond strengths of laboratory-cured prosthetic composite to primed metal surfaces

To examine the effect of using metal primers to enhance the shear bond strength of a laboratory-cured prosthetic composite to cast metal surfaces.

Cast discs (10 mm diam., 2.5 mm thick) were prepared from high gold-containing alloy, Ag-Au-Pd alloy, and commercially pure titanium (CP Ti). After casting, the surfaces of the discs were sandblasted with 50 microm Al2O3. Each surface to be bonded was treated with one of four types of metal primers: V-Primer (VP), Metal Primer II (MP), Cesead II Opaque Primer (OP), and an experimental primer (EP). Specimens without primer were prepared as controls. After tape with a circular hole (5 mm diam.) was fixed on the disc surface to define the bonding area, the opaque resin was applied within the hole and light-cured according to the manufacturer's instructions. After polymerization of the opaque resin, a layer (1 mm thick) of each dentin and enamel resin was applied separately using Teflon matrices (6 mm I. D.). The bonded specimens were immersed in 37 degrees C water for 24 hours (baseline) and were then thermocycled for 5,000 and 10,000 cycles. The shear bond strengths were determined at the baseline and after thermocycling. The results were analyzed using ANOVA/Bonferroni/Dunn's test (c = 0.05).

There were no statistical differences (P > 0.05) in the shear bond strength among surface applications for the gold alloy at the baseline. After 5,000 and 10,000 thermocycles, the gold alloy specimens primed with OP and EP primers exhibited higher bond strength compared to those primed with VP and MP primers, and the non-primed control specimens. The Ag-Au-Pd alloy specimens tended to be similar to the gold alloy specimens after each number of thermocycles. The shear bond strengths to CP Ti primed with OP and EP were significantly (P < 0.05) higher than the others after 5,000 and 10,000 thermocycles.