from allegations of being too risky from the health standpoint. Low copper to high copper amalgam alloy Amalgam has been used for many years for restorations, commonly known as fillings. Prior to 1900 many compositions were tried but few were successful when placed in the oral environment. Around 1900, small amounts of copper and occasionally zinc were added. Zinc acts as a scavenger because it prevents oxidation of the other metals in the alloy during the manufacturing process. Zinc accomplishes this by combining readily with oxygen to form zinc oxide. Amalgam restorations made from this balanced formula were reasonably successful and its longevity increased. However, one disadvantage that remained was fracture at the tooth-amalgam interface commonly called marginal fracture. Sn8Hg (γ2 phase) was considered to be responsible for this problem. This phase has been shown to be the weakest phase in the set amalgam and is subject to corrosion, particularly at the tooth-amalgam interface. In 1962 a new amalgam alloy, called Dispersalloy, was introduced with the addition of a spherical silver-copper eutectic particle to the traditional lathe-cut Ag3Sn particle in a ratio of 1:2. The mixture of these two types of particles is known as admix alloy. This alloy strengthened the set amalgam and reduced the γ2 phase (Sn8Hg). The increased copper in the silver-copper eutectic reacted preferentially with tin so that Sn8Hg could not form. Early results from the clinical use of this new amalgam showed an improvement in marginal integrity. About 10 years later, another alloy, called Tytin, was introduced by adding significant amount of Cu3Sn together with Ag3Sn, in the form of a unicompositional spherical particle to eliminate the γ2 phase. Both of these relatively new alloys raised the copper content from 5%, present in the older balanced composition alloy, to about 13% for the newer alloys. Composition Dental amalgam is produced by mixing liquid mercury with an alloy made of silver, tin, and copper solid particles. Small quantities of zinc, mercury and other metals may be present in some alloys. This combination of solid particles is known as amalgam alloy. The composition of the alloy particles are controlled by the ISO Standard (ISO 1559) for dental amalgam alloy in order to control properties of set amalgam such as corrosion and setting expansion. It is important to differentiate between dental amalgam and the amalgam alloy that is commercially produced and marketed as small filings, spheroid particles, or