What is usually the cause of corrosion and discoloration of amalgam restorations?

The corrosion and discoloration of amalgam restorations can primarily be attributed to exposure to environmental factors, particularly sulphur oxides. Amalgam is a dental material that can undergo chemical reactions when subjected to acidic compounds, which can lead to corrosion. Sulphur oxides, often present in industrial emissions, can react with the metal components of the amalgam, causing both corrosion and aesthetic changes like discoloration.

While oxygen does play a role in certain chemical reactions, and chlorides can influence the corrosion process as well, it is the specific reactivity of sulphur oxides with the metals in amalgam that is most significant for causing noticeable deterioration and coloring changes in dental restorations. Over triturating, which refers to the mechanical mixing process of amalgam, can affect the physical properties of the material but is not a direct cause of corrosion or discoloration due to environmental exposure. Therefore, sulphur oxides are identified as a primary concern when discussing the degradation of amalgam restorations.