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 the use of dental amalgam, but allows phasing down amalgam use over a time period appropriate to domestic needs, an approach advocated by the World Health Organization (WHO). FDI World Dental Federation recognizes the safety and effectiveness of amalgam restorations. FDI is a federation of approximately 200 national dental associations and dental specialist groups representing over 1.5 million dentists. In collaboration with the WHO, they have produced an FDI position statement and WHO consensus statement on dental amalgam. Their position regarding the safety of dental amalgam is that, aside from rare allergic reactions and local side effects, "the small amount