Amalgam is a mercury alloy that can come in different variations. In dentistry, one variation of amalgam has been used as a dental filling for centuries thanks to its beneficial properties. Medical amalgam consists of about half mercury, the other half is a mixture of copper, silver and tin. Amalgam is medically controversial because of its mercury component. While it is a very inexpensive material, subsequent health problems such as amalgam poisoning cannot be ruled out in principle.
What is amalgam?
Amalgam is a very inexpensive material for filling teeth, but subsequent health problems such as amalgam poisoning cannot be fundamentally ruled out. Chemically, amalgam is a mercury alloy. In addition to a number of naturally occurring amalgams, there are also a number of technical amalgams that are made for various purposes. Amalgam is particularly well known for its use in dentistry. There it is often used as a filling material for damaged teeth. Dental amalgam consists of half mercury and half a metallic powder mixture of silver, copper and tin. Both are made into a paste and can then be poured into the tooth, where it hardens into a durable filling.
Shapes, types and types
Because many metals exist that are soluble in mercury, many different amalgams also exist. Depending on the level of mercury content, these amalgams are liquid to solid at room temperature. The higher the mercury content, the more liquid the corresponding amalgam is, since mercury itself is liquid at room temperature. In addition to naturally occurring amalgams with lead, copper, palladium, silver or gold, there are also technical, artificially produced amalgams, which often find their use as reducing agents in chemistry or in low-temperature thermometers. Known technical amalgams are the aluminum amalgam, the sodium amalgam, the ammonium amalgam, the thallium amalgam and the gold amalgam. However, the well-known dental amalgam also belongs to the technical amalgams. This was the only type of amalgam commonly used as a filling material in dentistry.
Structure and function
Dental amalgam is used when a tooth that has been affected with caries had to be drilled and the existing hole has to be filled again afterwards. For an amalgam filling, the dentist must thoroughly mix the metals contained in the alloy, thus the mercury and a powder mixture of copper, silver and tin. The dentist then has about 10 to 30 minutes to place the filling in the correct position. This includes adjusting the filling to the bite. After this period, the filling begins to harden and can be polished so that the transitions between the filling and the tooth become smooth. After just 60 minutes, the finished filling can withstand light loads. During the curing process, the mercury combines with the silver, causing the filling to change its state from malleable to solid. After about 24 hours, the amalgam filling is fully cured and very resistant. Provided there are no medical problems, the finished filling can remain in the tooth for about 10 years if it is made professionally and without errors. The body is exposed to mercury mainly before the amalgam filling is fully cured. When fully cured, mercury can no longer escape from the alloy because the silver binds the mercury. However, abrasion of the filling cannot be completely prevented despite the hardness of the material. A professionally made amalgam filling is very easy to maintain. General dental care is sufficient. However, a regular check-up by the dentist is advisable. The transition between the filling and the tooth should be polished occasionally to avoid the risk of caries at the transitions. In addition, the amalgam filling should be checked for proper seating and possible cracks, as in such a case it would leak. Caries can then quickly form under a loosely fitted filling.
Medical and health benefits
Amalgam finds its medical benefits as a dental filling. Amalgam has been the most commonly used filling material for tooth decay for several centuries.This is due to its numerous positive properties: Dental amalgam is not only very cost-effective, but also robust and resistant to pressure and moisture, fracture-resistant and very durable. In terms of expansion at different temperatures, amalgam and dental enamel have very similar properties. Furthermore, a filling made of amalgam is quick and easy to make and can remain in the tooth for up to ten years. Nevertheless, the possible uses of amalgam in dentistry are limited. In the case of complicated fillings such as a root canal filling or a build-up filling under existing crowns, an alternative filling material is usually used. Amalgam is also often criticized as a filling material because of its high mercury content. Although the burden on the body is in the non-measurable range, the material was nevertheless classified by the EU in 2014 as “low risk”, which corresponds to a different verdict than “non-hazardous”. In Sweden, Norway and Denmark, the use of amalgam has now been severely restricted. However, it is still a permitted low-cost alternative to other dental restoratives. People with a mercury allergy or kidney damage, as well as pregnant and lactating women, should use an alternative filling material. In addition to amalgam, plastics, glass mixtures, cement, ceramics or gold can also be used.
