Restorations based on mercury and metallic alloys are also being used in dental restorations. An alloy is made by melting and mixing together two or more metals and then letting them cool. Amalgam is a mixture of a powdered solid metal or alloy with a liquid metal (mercury) at room temperature. Dentists use an amalgam of mercury with a powdered alloy of silver, tin and copper. Tiny amounts of other metals like palladium, indium and zinc may also be present. Dental amalgams are always made with mercury. That is because mercury is the only metal liquid at room temperature and able to bind to the metals and bind them together. In layman language it is known as the ‘silver filling’ material. It is the cheapest durable filling material available today.
The amalgam when mixed in the office at room temperature forms putty like substance. It allows the dentist fill the cavity and form the filling into the desired shape before it slowly hardens in about twenty four hours. Full strength is gained much later. It should be protected from contact with water before it is placed in the cavity. The filling has a silvery look and for this reason in layman language it is called the silver filling material.
Mercury constitutes nearly 50% of the amalgam mass, with silver about 22-32 %, tin 14%, and copper varying between 4-8 %. Thus we have high copper amalgam and low copper amalgam giving slightly different properties. There have questions about toxic effects of mercury being released into the body of the patient. However, current opinion is that it is quite safe and poses no threat. Amalgam has been used safely for over a century with no adverse effect noticed. After thorough testing regarding the safety of amalgam filling materials, the FDA has cleared it for use as a restorative material.
The use of amalgam in fillings is being challenged by composite of acrylic and glass. It has the advantage of color matching, since any desired color can be used to match the surrounding teeth. In a filling it may be almost as strong as the amalgam. The amalgam has the advantage of a lower cost, and easier placement and shaping. It takes much less time to fill and form than composite materials. Composites have to be placed by the dentist layer by layer and consume time.
