Existence of an electrically insulating layer in amalgam-containing galvanic couples
Elliott J Sutow1, James C Taylor, Wayne A Maillet
1Department of Applied Oral Sciences, Faculty of Dentistry, Dalhousie University, 5981 University Avenue, Halifax, Nova Scotia, Canada B3H 3J5. Elliott.Sutow@dal.ca <Elliott.Sutow@dal.ca>
Summary
An electrically insulating layer likely forms between dental restorations, reducing galvanic corrosion. This layer, composed of corrosion products and biofilms, was observed in amalgam/noble metal and amalgam/amalgam couples, mitigating corrosion risks.
Area of Science:
- Dental Materials Science
- Electrochemistry
- Biomaterials
Background:
- Galvanic corrosion is a concern for dissimilar dental restorations (amalgam/noble metal) and similar ones (amalgam/amalgam).
- The formation of an electrically insulating layer could mitigate galvanic corrosion rates.
Purpose of the Study:
- To investigate the presence of an electrically insulating layer in galvanic couples of dental restorations.
- To determine if this layer reduces galvanic corrosion between amalgam and noble metal restorations, and between amalgam restorations themselves.
Main Methods:
- Corrosion potentials were measured on 158 human subjects with existing restorations (amalgam/noble metal, amalgam/amalgam, noble metal/noble metal).
- Measurements utilized a Ag/AgCl micro-reference electrode and a high impedance voltmeter.
- All restorations were at least 6 months old to ensure mature surface conditions.
Main Results:
- Significant corrosion potential differences were observed in amalgam/noble metal couples (mean absolute difference: 62mV).
- Smaller, yet detectable, potential differences were found in amalgam/amalgam (11mV) and noble metal/noble metal (7mV) couples.
- These differences indicate the presence of an electrically insulating layer in all tested couple types.
Conclusions:
- An electrically insulating layer consistently forms between amalgam/noble metal restorations, significantly reducing galvanic corrosion.
- Similar insulating layers are present in amalgam/amalgam and noble metal/noble metal couples.
- This layer, likely comprising corrosion products, biofilms, and calculus, effectively minimizes galvanic corrosion rates in dental restorations.
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