What role does contamination from moisture play in amalgam expansion?

Contamination from moisture significantly increases the expansion of amalgam. Amalgam is a mixture of metals that reacts chemically upon setting, and this setting process can be adversely affected by the presence of moisture. When water or saliva comes into contact with the amalgam before it has solidified, it can cause a reaction that leads to a phenomenon known as "dimensional changes." Specifically, this moisture can promote hydrolysis, resulting in the formation of additional phase products that expand as they set.

The increase in expansion is important to consider because it can lead to discomfort for the patient, compromised dental restorations, and can even contribute to failure in achieving a proper seal at the margins of the restoration. Therefore, controlling moisture during amalgam placement is crucial to ensure the longevity and effectiveness of the dental restoration. Proper isolation techniques, such as the use of rubber dams or suction, are essential in minimizing moisture contamination during the placement of amalgam restorations.