A clinical study of marginal integrity and tarnish behaviour of three Cu-rich amalgam systems.

Three high Cu-gamma2 free amalgams and one conventional amalgam were used in a clinical study to evaluate degree of marginal integrity and surface discoloration occurring for time periods of up to two years. Two hundred and seventy restorations were placed in Class I and II cavities in sixty-two paedodontic patients. Amalgams were prepared from conventional alloy, Cu admixed, Dispersalloy and three parts 50Ag-20Sn-30Cu mixed with one part conventional alloy. Restorations were evaluated by three groups of clinicians. Ridit means obtained from all three groups of evaluations were in good agreement. The lower ridits indicate better marginal integrity and less tarnish. Marginal integrity of amalgams prepared from Cu-admix did not differ appreciably (0.41) from the ridit associated with initial placement (0.39). Conventional amalgams had the highest ridit (0.65) for marginal integrity whereas the ternary/conventional and Dispersalloy restorations were intermediate (0.55 and 0.52). The ridit for tarnish and surface discoloration was decidedly higher for the Cu-admix (0.73) than for the other systems investigated which had ridits of the order of 0.50 compared to an initial ridit for tarnish of 0.28.