A composite dental filling is an option for filling cavities or replacing the chipped or fractured structure of a tooth that involves using a mixture of plastic resin and ceramic compounds like silica. It has both advantages and disadvantages over the use of traditional metal amalgams for dental repair, which have been used by dentists for the past 150 years. One of the most common reasons that a composite dental filling is used is because it can be shaped and colored to precisely match the look of natural teeth. This makes its primary function that of a replacement for visible front teeth in the mouth that are part of a person's smile.
When composite resin dental fillings first appeared on the market, they were only used for front teeth that are involved in the cutting of food. This was due to the fact that the composite material itself was not strong enough to stand up to the grinding pressure of molars in the back of the mouth, so it was not suitable for tooth repair in these locations. Advances in composite dental filling compounds as of 2008 have made it possible to use them for teeth in any location in the mouth. Despite these improvements, however, composite fillings are still more prone to chipping and other degradation than metal amalgams, and have a typical life-span of about five years compared to 10 to 20 years for metal fillings.
Metal amalgams are usually a combination of silver, tin, and copper bound together with about 50% mercury. Such silver fillings are stronger than composite dental fillings and cost about half as much as the composites, though, if gold-based metal amalgams are used, the cost savings is negated. The silver fillings will blacken with age, which makes them unappealing to many people who want their teeth to look as clean and natural as possible.
Another limitation of installing a composite dental filling in the mouth is that the area has to be fairly dry for the resin to set properly, and this is a difficult process to maintain near the back of the mouth where molars are located. Improvements in the formula for the composite have been limited in overcoming their original drawbacks, and, as of 2011, most dental insurance plans only cover the installation of composite tooth fillings in the front of the mouth. This area includes the front six incisors and cuspids, as well as the two bicuspids alongside of them.
The value of a composite dental filling is foremost that of a cosmetic nature. They can be partial replacements for tooth damage that closely matches the original tooth material in appearance, and the resin chemically bonds to the tooth structure to strengthen it. Unlike amalgams, they can be used to fix finely chipped, cracked, or worn vertical sections of teeth that would look unnatural if repaired with metal inlay. Some dental procedures also allow for preserving more of the original tooth with a composite repair, though the actual dental procedure takes longer than a repair with traditional metal amalgam would.