Every dental material used to rebuild teeth has advantages and disadvantages. Dental amalgam or silver fillings have been around for over 150 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. Some people worry about the potential for mercury in dental amalgam to leak out and cause a wide variety of ailments, but research does not bear this fear out.
Composite, resin, or white fillings have been around for about two decades. 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. Composite fillings are the material of choice for repairing the front teeth. On the down side, they are more technique sensitive for the dentist to place, and are highly susceptible to decay in the future if placed improperly. They usually cost more than an amalgam, and recent research has shown that a by-product of some resin restorations called bisphenol-A may be estrogenic and increase the risk of breast cancer. Despite this research composite fillings are considered safe, and like the other dental filling materials, they are approved by the American Dental Association.
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. It is also even more technique sensitive to use than composite, requires two dental visits to place the filling, and costs significantly more than amalgam or composite fillings. Porcelain can also cause accelerated wear of the opposing tooth when biting.
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. In addition, gold inlays are fairly difficult to prepare and place - just ask any third-year or fourth-year dental student. They are usually required for graduation from dental school.