Corrosion behavior and microhardness of three amalgams

Area of Science:

• Materials Science
• Dental Materials
• Corrosion Science

Background:

• Dental amalgams are widely used restorative materials.
• Marginal integrity is crucial for long-term restoration success.
• Amalgam corrosion in oral environments can compromise marginal seal.

Purpose of the Study:

• To evaluate the effect of a corrosive solution (NaCl and phosphates) on the marginal microhardness of three dental amalgam types.
• To investigate the corrosion mechanisms and identify phases susceptible to degradation.
• To assess the protective role of phosphates against amalgam corrosion.

Main Methods:

• Three amalgam types (conventional, high-Cu single composition, high-Cu blended) were immersed in NaCl and phosphate solutions for 2 months.
• Microhardness testing was performed at margins and bulk specimens.
• Corrosion products and elemental analysis were conducted using Scanning Electron Microscopy (SEM) and Atomic Absorption Spectrophotometry (AAS).

Main Results:

• Significant reduction in marginal microhardness observed for conventional and high-Cu single composition amalgams.
• High-Cu blended amalgam showed no significant marginal microhardness reduction.
• Corrosion primarily affected Cu-rich phases (high-Cu amalgams) and the gamma 2 phase (conventional amalgam).
• Phosphates demonstrated a corrosion-inhibiting effect in the presence of NaCl.

Conclusions:

• Marginal strength of dental amalgams is significantly influenced by their corrosion resistance in challenging environments.
• High-copper blended amalgams exhibit superior marginal stability compared to conventional and single-composition high-copper amalgams.
• Understanding corrosion mechanisms is key to developing more durable dental restorative materials.