Amalgam (dentistry) packs the plastic mass, before it sets, into the cavity. The amalgam expands ≈0.1% over 6–8 hours on setting. The final structure is a metal matrix composite, where γ, η and γ phases, are a matrix for unreacted original alloy, minus the fast-reacting β-phase and excess Sn. Amalgam is a mixture of two or more metals (alloy) with mercury which has been purified first by distillation to remove impurities. Currently, major components of the alloy are silver tin and copper. The composition of the alloy powder is controlled by ISO standard for dental amalgam alloy (ISO 1559) to control the
Dental amalgam controversy safety and effectiveness of amalgam restorations. In 2012, the Australian Dental Association published a position paper on the safety of dental amalgam. Their position is that "Dental Amalgam has been used as a dental restorative material for more than 150 years. It has proved to be a durable, safe and effective material which has been the subject of extensive research over this time" and that "amalgam should continue to be available as a dental restorative material". Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) is a scientific committee within the European Commission. In a 2008 document of 74