An amalgam is defined as a special type of alloy in which mercury is one of the components. Mercury is able to react with certain alloys to form a plastic mass, which is conveniently packed into a prepared cavity in a tooth. This plastic mass hardens and is stronger than any dental cement or anterior filling material. Dental amalgam is the most widely used filling material for posterior teeth. The alloys before combining with mercury are known as dental amalgam alloys. Strictly speaking, however, this is a misnomer as they are not dental amalgam alloys but alloys from which dental amalgam is prepared. In dentistry, amalgam has been successfully used for more than a century as a restoration material for tooth decay. Over the years its quality has greatly improved, thanks to a lower amount of mercury and the addition of new components which can reduce its corrosion in the oral cavity.