What is the importance of the secondary reaction availability of copper in high copper amalgams?

The importance of the secondary reaction availability of copper in high copper amalgams primarily relates to its role in eliminating the Gamma-2 phase. In dental amalgam, the Gamma-2 phase is a component that can be detrimental to the overall performance of the restoration, as it is associated with corrosion and degradation. High copper amalgams were developed to overcome the deficiencies of traditional amalgams, particularly those that contain this problematic Gamma-2 phase.

When additional copper is present in the amalgam, it reacts with the tin from the alloy to form stable compounds, thus effectively reducing or entirely eliminating the Gamma-2 phase. The absence of this phase enhances the durability and longevity of the restoration, as it minimizes potential failures related to corrosion and fracture susceptibility. Therefore, the elimination of the Gamma-2 phase through the secondary reaction with copper significantly contributes to the improved mechanical properties and clinical performance of high copper amalgams compared to conventional formulations.