Dental amalgam has been used for over 150 years. It has been thoroughly researched, tested and improved. It is commonly placed in the posterior teeth (“back teeth”). Amalgam is a mix of 43-54% mercury, silver, copper and tin, and it has a silver color when placed. In comparison to tooth-colored fillings, amalgam is stronger and more durable against biting force, shrinks less and therefore leaks less and lasts longer than tooth-colored filling material, tends to cause less sensitivity following placement. Disadvantages include: darkening over time, and concerns of mercury vapor release (though the FDA, CDC and WHO have not found evidence of harm).