Final answer:
The reaction that occurs when a silver-based alloy is mixed with mercury to create dental amalgam is called amalgamation. Dental amalgams consist of about 50% mercury, which has caused concerns due to mercury's toxicity.
Step-by-step explanation:
When the silver-based alloy used to create dental amalgam is mixed with mercury, the reaction that occurs is called amalgamation. In dentistry, amalgams containing silver and other metals such as tin and copper are used to fill cavities. Dental amalgams are approximately 50% mercury by weight, which binds well with the solid metal alloy to form a stable filling material. However, due to the toxicity of mercury, the use of mercury-based dental amalgam has been a concern in recent years.