Amalgam fillings refer to a material known as amalgam which is used by dentists to fill dental cavities. It is composed of a mixture of various metals, including silver and mercury, and has been in wide use in the field of dentistry for centuries. It has been in use longer than most drugs, and the only material that has been used in dentistry longer than amalgam is gold.
For many decades, amalgam fillings were the most common type of fillings used in dentistry. The material was and continues to be relatively inexpensive, as well as being strong, fairly durable, and easy to apply. More recently, the use of amalgam fillings has been on a decline, principally because of controversy over the high percentage of mercury content in dental amalgam. Mercury is a heavy metal, and as such can pose health hazards if it gets into the bloodstream. Like lead, it can settle in the central nervous system where it causes irreversible damage if the concentrations are too high.
The typical formulation of dental amalgam is anywhere between 43% and 54% percent mercury, mixed with a powder containing mainly silver, zinc, as well as small amounts of tin and copper. Materials known as dental composites are increasingly being substituted for amalgam, but these are more expensive, take greater care to apply, and generally do not last as long. It is common for composite fillings to fall out or need replacement in five to ten years, while amalgam fillings remain in place for ten to 12 years.
Even before ceramic composite materials were developed, the use of amalgam fillings began to decline in the 1970s. It is generally thought that this was due to a better popular awareness of the importance of dental hygiene, and the ways to prevent dental cavities from forming. Many dentists have reported that, as part of this trend, many of the cavities seen today are smaller and easier to treat.
Notwithstanding the controversy over the use of mercury-containing amalgam fillings, they continue to be widely used. In fact, the U.S. Public Health Service does not believe that it is necessary to restrict the use of amalgam. This is due to the lack of conclusive scientific evidence that the mercury present in amalgam poses a consistent health risk. While it is true that people with amalgam fillings do absorb some mercury, there is little evidence that it is absorbed at a level that can be considered dangerous. Also, there has yet to be found an alternative material to use in place of amalgam that offers similar benefits, such as those of low cost and longevity.