Shear bond strength of the amalgam-resin composite interface

Objective: This study compared the initial and one year shear bond strengths (SBS) of resin composite bonded to amalgam using Amalgambond-Plus. Methods: Resin composite cylinders (Point 4, Kerr Corporation) were bonded to either etched-enamel (A), 50% etched enamel-50% polished amalgam (B), airborne-particle abraded amalgam (C), carbide bur prepared amalgam (D) and airborne-particle abraded 50% amalgam-50% etched-enamel (E). Shear bond strengths were determined using a standardized testing device (Ultradent Products) in a universal testing machine (Instron model 4204). The failed interfaces were evaluated with SEM to obtain visual evidence of the failure mode. Results: ANOVA indicated significant differences among the groups (p < 0.0001). SBS in MPa (Mean/SD) were for A at year 0: (24.63/4.19), A at year 1: (16.84/7.25), B at year 0: (9.13/2.18), B at year 1: (15.54/6.41), C at year 0: (16.82/3.60), C at year 1: (15.26/3.90), D at year 0: (9.27/4.03), D at year 1: (7.97/7.17), E at year 0: (16.67/4.87) and E at year 1: (8.63/3.64). Conclusion: In vitro testing demonstrated that resin composite masking has the strongest, most durable SBS on airborne-particle abraded amalgam and airborne-particle abraded enamel-amalgam surfaces and could be used as a method to improve the esthetics of amalgam restorations.