A six year follow-up of three dental alloy restorations with different copper contents.

Class II restorations of three amalgam alloys, with 6%, 12% and 23% copper content, respectively, were evaluated and compared intraindividually during a six year follow-up. In total 10.3% of the restorations were replaced during the test period. The reasons for replacement were bulk fracture (5.6%), tooth fracture (2.4%), marginal ridge fracture (0.8%), and secondary caries (1.6%). The intraindividual ranking of the three alloys, including evaluation of anatomical form, marginal adaptation and secondary caries, showed significantly better results for the two high copper alloys than for the conventional low copper alloy. No difference was seen between the two high copper containing alloys.