Every dental material used to rebuild teeth has advantages and disadvantages. Dental amalgam or silver fillings have been around for over 160 years. Amalgam is composed of silver, tin, copper, mercury, and zinc. Amalgam fillings are relatively inexpensive, durable, and time-tested. On the flip side, they are considered unaesthetic because they blacken over time and can give teeth a gray appearance, and they do not strengthen the tooth.
Composite, resin, or white fillings have been around for more than 30 years. Composite fillings are composed of an organic polymer known as bisphenol-A-glycidyl methacrylate (BIS-GMA), and inorganic particles such as quartz, borosilicate glass, and lithium aluminum silicate. They have the advantage of requiring a more conservative tooth preparation, (less drilling required), can have a strengthening effect on the tooth, and are very aesthetic, virtually blending in with the tooth.
Porcelain is sometimes used for dental fillings called inlays. Porcelain is a non-crystalline glass composed of silicon and oxygen. It has the advantage of being highly aesthetic, and is the restoration of choice for people who place the highest value in the appearance of their teeth. Porcelain has the disadvantage of being brittle and therefore susceptible to breakage.
Gold is sometimes used for dental fillings, most commonly as an inlay. Gold is not used in its pure form, but as an alloy containing 75% gold, as well as copper, silver, platinum, palladium, and zinc. Gold is extremely durable; fairly esthetic, does not damage the opposing tooth when biting, and is very well tolerated by the gums and other intra-oral tissues.
A well-done gold filling can last two to four times longer than any other dental material, and might be considered the "gold standard" for dental fillings. Gold inlays, like porcelain inlays, take two dental visits to complete and are also much more costly than amalgam or composite. They are also not nearly as aesthetic as composite or porcelain.