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Surface degradation of amalgams in vitro during static and cyclic loading
Scandinavian Journal of Dental Research
|December 1, 1983
Summary
Corrosion and static creep in dental amalgams cause grain boundary cracking. Cyclic loading significantly accelerates this degradation, releasing more mercury and copper from non-gamma 2 amalgams.
Area of Science:
- Materials Science
- Biomaterials Engineering
- Dental Materials
Background:
- Dental amalgams undergo degradation, influenced by mechanical stress and corrosive environments.
- Understanding corrosion mechanisms in amalgams is crucial for improving longevity and patient outcomes.
- Gamma 2-containing and dispersed phase amalgams exhibit different degradation behaviors.
Purpose of the Study:
- To investigate corrosion and creep mechanisms in dental amalgams under static and cyclic loading conditions.
- To compare the degradation behavior of gamma 2-containing amalgams with dispersed phase non-gamma 2 amalgams.
- To quantify material release during corrosion and assess the role of cracking.
Main Methods:
- Scanning Electron Microscopy (SEM) for observing microstructural changes and crack formation.
- Static creep tests in artificial saliva.
- Cyclic loading experiments with quantitative measurements using nuclear tracer techniques.
- Analysis of mercury (Hg), copper (Cu), and zinc (Zn) release.
Main Results:
- Corrosion occurs at gamma 1-grain boundaries during static creep, associated with grain boundary sliding and dislocation slip.
- Cracking within gamma 1-grains was observed, particularly in dispersed non-gamma 2 amalgams.
- Combined corrosion and stress accelerate crack formation.
- Cyclic loading significantly increases degradation rates (1-2 orders of magnitude) compared to static loading.
- Dispersed non-gamma 2 amalgams released more Hg, Cu, and Zn under cyclic loading, with 50-90% present as particulate matter.
- Observed degradation patterns differ from previous studies on marginal degradation.
Conclusions:
- Corrosion and creep, especially under cyclic loading, are significant degradation pathways for dental amalgams.
- Dispersed non-gamma 2 amalgams show a higher tendency for cracking and material release under stress.
- Cyclic loading dramatically enhances amalgam degradation, challenging previous findings on marginal degradation.