Linear dimensional change of copper-rich dental amalgam

Copper-rich amalgams made from alloy mixtures have large expansions in air at 105 +/- 2 weeks that range from 100 to 194 micrometers/cm at 60 C, from 36 to 101 micrometers/cm at 37 C, and from 14 to 44 micrometers/cm at 23 C on unrestricted 8- x 4-mm cylinders (Dispersalloy, Micro II, and Optaloy II). Other copper-rich amalgams made from one alloy usually had a slight shrinkages at the three temperatures with an exception, a slight expansion of 12 micrometers/cm at 60 C (Aristaloy CR, Indilogy non-zinc, Sybraloy, and Tytin). Dimensional changes during hardening ranged,on the average, from -3 to +19 micrometers/cm when measured by ADA Specification methods and from -2 to +25 micrometers/cm when measured by an indirect method. The clinical significance of the foregoing findings is unknown; nor is a relationship known among dimensional change of unrestricted specimens, dimensional change of restricted specimens, creep value, and clinical behavior of amalgams generally. In specific instances, however, a relationship is sometimes shown.