A shear stress analysis of the bonding of porcelain veneers to enamel.

This study demonstrated the relative strengths of the composite resin bond to etched enamel and the composite resin bond to surface-treated porcelain with similar conditions. It also compared the strength of a combined porcelain/composite/enamel bond with the strengths of porcelain/composite resin and enamel/composite resin bonds and evaluated the effectiveness of silane treatment of the etched porcelain. The influence of thermocycling was also investigated. There were 20 samples for each five categories: (1) composite resin/etched porcelain; (2) composite resin/etched and silane-treated porcelain; (3) composite resin/acid-etched enamel; (4) etched porcelain/composite resin/acid-etched enamel; and (5) etched and silane-treated porcelain/composite resin/acid-etched enamel. Half in each category were subjected to thermocycling. Shear testing and microscopic examination of the fracture sites resulted in the following: (1) Shear testing a combined enamel/composite/porcelain bond resulted in significantly different values from testing individual enamel/composite resin and porcelain/composite resin bond strengths. (2) Silane treatment of the etched porcelain recorded a significantly greater shear strength to the merely etched samples. (3) Thermocycling did not significantly dilute the effects of silane treatment of the etched porcelain surface.