Amalgam

Amalgam is composed of an alloy of silver, tin and copper combined with mercury. It has a number of advantages as a filling material: low cost, a relatively long lifespan (around thirteen years on average), good strength, and moisture insensitivity – making it excellent for fillings beneath the gums. Amalgam has been in use as a filling for a long time, but some people do have concerns about the health risks posed by the mercury content.

Alternative materials include composite, porcelain and gold.