Precious-metal dental casting alloys

The precious metals are used for dental casting alloys because of their recognized stability in the human mouth. This use is split between the traditional gold-coloured crown and bridge restorations and the newer, more aesthetic porcelain-veneered devices. Three ternary systems provide the basis for most of the commercially successful alloys; Au-Ag-Cu, Pd-Ag-Cu, and Au-Pt-Pd. Basic features of these three systems are discussed with respect to alloy formulation and performance. Factors such as segregation, phase stability, hardenability, melting behaviour, th.ermal expansion, colour, castability, tarnish, corrosion, and biocompatibility are related to these ternary systems. The review focuses on specific applications and details properties of representative chemistries. Data are presented to demonstrate composition and microstructure influences on mechanical, physi cal, thermal, and chemical properties. Several unresolved questions are discussed, such as the criteria for porcelain-alloy compatibility, to provide a view on areas of active research. An overall emphasis is given to the use of precious metals in dentistry based on their accepted biocompatibility; current trends in the application and formulation of these alloys are included to enhance this point.