Marginal adaptation of amalgam and resin composite restorations in Class II conservative preparations

Objective: The purpose of this study was to compare and contrast the perfor mance, in terms of marginal adaptation, of a non-gamma-ii amalgam alloy wit h a compact-filled light-cured composite in the restoration of Class II pre parations of conservative design. Method and materials: Fifty recently extr acted teeth were selected for the study. The teeth were restored with eithe r a non-gamma-2 amalgam alloy, Dispersalloy, or a compact-filled resin comp osite, Z100, using standard techniques. The marginal adaptation of the rest orative materials to the proximal surface outline form of each preparation was assessed at magnification x30. Results: Highly significant differences were demonstrated in the mean percentages of perfect margins in all 3 segme nts of the proximal boxes of the restorations with the resin composite perf orming significantly better than the amalgam. The percentages of marginal f issuring were significantly higher in the amalgam restorations, except at t he cervical margin, where the incidence of fissuring was almost the same fo r the amalgam and resin composite restorations. The resin composite restora tions had significantly fewer underfilled margins than the amalgam restorat ions. Conclusion: In the conservative Class II preparations, the amalgam re storations were of poor quality with respect to marginal adaptation, compar ed with the resin composite restorations. It is suggested that the use of a malgam as a control in a clinical evaluation of resin composite restoration s in conservative preparations cannot be justified, because it is apparentl y not possible to compare restorations of equivalent initial quality.