content) gold-platina alloy silver-palladium alloy Base metallic alloys cobalt-chrome alloy nickel-chrome alloy Amalgam Amalgams are alloys formed by a reaction between two or more metals, one of which is mercury. It is a hard restorative material and is silvery-grey in colour. One of the oldest direct restorative materials still in use, dental amalgam was widely used in the past with a high degree of success, although recently its popularity has declined due to a number of reasons, including the development of alternative bonded restorative materials, increase in demand for more aesthetic restorations and public perceptions concerning the potential health risks of the material. The composition of dental amalgam is controlled by the ISO Standard for dental amalgam alloy (ISO 1559). The major components of amalgam are silver, tin and copper. Other metals and small amounts of minor elements such as zinc, mercury, palladium, platinum and indium are also present. Earlier versions of dental amalgams, known as 'conventional' amalgams consisted of at least 65 wt% silver, 29 wt% tin, and less than 6 wt% copper. Improvements in the understanding of the structure of amalgam post-1986 gave rise to copper-enriched amalgam alloys, which contain between 12 wt% and 30 wt% copper and at least 40 wt% silver. The higher level of copper improved the setting reaction of amalgam, giving greater corrosion resistance and early strength after setting. Possible indications for amalgam are for load-bearing restorations in medium to large sized cavities in posterior teeth, and in core build-ups when a definitive restoration will be an indirect cast restoration such as a crown or bridge retainer. Contraindications for amalgam are if aesthetics are paramount to patient due to the colour of the material. Amalgams should be avoided if the patient has a history of sensitivity to mercury or other amalgam components. Besides that, amalgam is avoided if there is extensive loss of tooth substance such that a retentive cavity cannot be produced, or if excessive removal of health tooth substance would be required to produce a retentive cavity. Advantages of amalgam include durability - if placed under ideal conditions, there is evidence of good long term clinical performance of the restorations. Placement time of amalgam is shorter compared to that of composites and the restoration can be completed in a single appointment. The material is also more technique-forgiving compared to composite restorations used for that purpose. Dental amalgam is also radiopaque which is