Properties of Ag-Cu-Pd dispersed phase amalgams: microstructures

Area of Science:

• Materials Science
• Dental Materials Science
• Metallurgy

Background:

• Conventional dental amalgams, primarily composed of silver (Ag), tin (Sn), and copper (Cu), are susceptible to the formation of the gamma 2 (Sn8Hg) phase.
• The gamma 2 phase is known to be a weak point in amalgam restorations, contributing to corrosion and reduced mechanical properties.
• Palladium (Pd) has been investigated as an additive to dental alloys to improve corrosion resistance and mechanical strength.

Purpose of the Study:

• To investigate the effect of incorporating a 62% Ag-28% Cu-10% Pd lathe-cut alloy into conventional amalgam formulations.
• To evaluate the phase structure and stability of the resulting blended amalgam, specifically focusing on the formation of the gamma 2 phase.
• To understand the role of the copper-palladium (Cu3Pd) phase in the amalgam reaction and its distribution within the final restoration.

Main Methods:

• A novel lathe-cut alloy (62% Ag-28% Cu-10% Pd) was prepared and blended with conventional lathe-cut and spherical amalgam alloys.
• The blended amalgam samples were aged for one week at 37 degrees Celsius.
• Phase analysis of the aged amalgam was conducted using techniques to identify the resulting microstructures and phases, including the gamma 2 phase and the behavior of the dispersant alloy.

Main Results:

• The blended amalgam exhibited minimal formation of the gamma 2 phase after one week of aging at 37 degrees C.
• The resulting phase structure closely resembled that of commercial amalgam, indicating good compatibility.
• The copper-palladium (Cu3Pd) phase within the dispersant alloy appeared to actively participate in the amalgam reaction.
• Palladium was observed in the reaction zones surrounding the dispersants, specifically within the gamma 1 (Ag2Hg3) and/or Cu6Sn5 phases.

Conclusions:

• The addition of a 62% Ag-28% Cu-10% Pd alloy to conventional amalgam formulations effectively suppresses the formation of the detrimental gamma 2 phase.
• The Cu3Pd phase plays a significant role in the amalgam reaction, potentially enhancing the stability and properties of the final restoration.
• This Ag-Cu-Pd alloy shows promise as a component in developing more durable and corrosion-resistant dental amalgams.