Effect of casting conditions on some mechanical properties of cobalt-base alloys.

The casting of cobalt-base alloys in dentistry is comparatively new in relation to the casting of gold alloys and other restorative procedures. It has been less than thirty years since these alloys were introduced to dentistry, but each year they have become more popular. A survey of the choice of dental alloys for removable partial dentures conducted by Lane' in 1949 showed that five times as many removable partial dentures were cast of the cobalt-base alloys as of gold alloys. Today this ratio may be even higher, since cobalt-base alloys are the choice of many dentists and laboratory technicians. Unfortunately, even with such a high demand for this type of alloy in dentistry, little is known by the profession about the physical and mechanical properties of the alloy or about its basic nature. Similar alloys of cobalt are widely used in industry at high temperatures, and consequently more work is done and reported with this type of alloy used at high temperatures than at room temperature. Although acceptable dental techniques for casting these alloys are available, a completely dependable, accurate, and easy-to-apply technique has not yet been developed. Such a technique probably cannot be developed until more is known about the basic nature of these alloys and about the effect of variations in casting procedures upon their properties. The purpose of this study was to determine the physical properties of cobalt-base alloys and to relate these properties to the microstructure, as well as to observe the influence of casting variables on both microstructure and physical properties. In this way the most acceptable casting practice can be selected which is revealed by both physical tests and microstructure.