Purpose: To compare the clinical performance of two high-copper amalga
m alloys with different compositions by evaluating marginal fracture o
f each restoration over a 2-year period. Materials and Methods: Restor
ations of Valiant PhD and Zenith Premium alloy were placed in Class I
and II cavity preparations in patients and evaluated at baseline, 1 an
d 2 years to determine their degree of marginal breakdown. Results: Af
ter 2 years, the Zenith Premium alloy exhibited significantly less mar
ginal breakdown than the Valiant PhD alloy with no significant additio
nal deterioration of the Zenith restorations between the 1st and 2nd y
ear. The data indicate that the Zenith Premium alloy exhibits less mar
ginal deterioration than Valiant PhD so it may be predicted that it wi
ll perform better long term. A possible explanation for this better pe
rformance may be that the Zenith Premium contains zinc while the Valia
nt PhD includes palladium but no zinc in its formulation.