Picture of Composite Fillings
Existing fillings sometimes need to be replaced due to wear, chipping, or cracking. Many people use this opportunity to replace silver amalgam fillings with tooth-colored composites. Their reasons may be aesthetic or concern about amalgam fillings, which contain mercury. The American Dental Association asserts that the mercury in amalgam combines with other metals to render it safe for use in filling teeth.
Image Source: American Academy of Cosmetic Dentistry / aacd.com.
Text: "Dental Health and Tooth Fillings", WebMD Medical Reference