Which component of amalgam increases strength and expansion?

The component of amalgam that increases strength and expansion is copper. Copper plays a crucial role in enhancing the mechanical properties of dental amalgam, notably increasing its strength. When amalgam contains copper, it forms copper-rich compounds during the setting reaction, which significantly improves its physical characteristics, including compressive strength and resistance to corrosion.

Additionally, copper assists in reducing the likelihood of amalgam being prone to expansion due to its ability to create a more stable phase within the amalgam mixture. The inclusion of copper has been found to enhance the performance of amalgam restorations, allowing for better longevity and durability in oral environments.

While silver is a key component of amalgam that also contributes to its strength, copper's influence on both strength and dimensional stability through expansion is more pronounced. Gold and lead are not typically associated with the properties of dental amalgams used in restorative dentistry, as gold is used in different types of restorations and lead can be toxic and is not used in dental materials.