Effects of two silane coupling agents, a bonding agent, and thermal cycling on the bond strength of a CAD/CAM composite material cemented with two resin luting agents

Abstract

Statement of problem. Surface treatment of CAD/CAM-generated composite material is important for a strong bond of resin luting agents to composite material. Purpose. This study evaluated the shear bond strengths of 2 dual-cured resin luting agents to a CAD/CAM composite material and the effect of silane coupling agent and bonding resin on the bond strength. Material and methods. Rectangular- and disk-shaped CAD/CAM composite materials were untreated or treated with 1 of the 2 silane coupling agents or bonding resin and then cemented together with 1 of the 2 dual-cured resin luting agents. Half of the specimens were stored in water at 37°C for 24 hours, the other half thermocycled 50,000 times before shear bond strength testing. Shear bond strengths were measured with a servohydraulic mechanical testing machine, and results were analyzed with 2-way analysis of variance. Results. Surface treatment by silane coupling agent improved the shear bond strength when compared with nontreatment. Specimens treated with bonding resin showed significantly greater shear bond strength than the untreated groups. However, all specimens had the same adhesive failures at the composite-luting agent interface as untreated groups. When the CAD/CAM composite material was treated with 1 of the 2 silane coupling agents, no significant differences in bond strength were noted between water storage alone and after 50,000 thermocycles. For the 2 groups treated with bonding resin or silane coupling agent and cemented with 1 of the 2 dual-cured resin luting agents, there were significant increases in bond strength after 50,000 thermocycles, compared with specimens that were not subjected to thermal cycling. On the other hand, for the 2 untreated groups, there were significant decreases in bond strength after thermocycling. After 50,000 thermocycles, all specimens treated with silane coupling agent and then cemented with 1 of the 2 resin luting agents showed cohesive failures within the composite material. Conclusion. The application of a silane coupling agent to the CAD/CAM composite surface provided the highest bond strength between the resin luting agent and composite after long-term thermal cycling. (J Prosthet Dent 2001;85:184-9.)