Metallurgical Properties Of Precious Metals And Their Alloys Which Affect Their Use In Dentistry

THE amount or value of the precious metals consumed in dentistry is probably amazing to most people. It falls very little short of that which is consumed in jewelry. Inasmuch as the ultimate destination is in the human mouth, dental alloys enjoy some importance because life and health depend upon restorations made with them. Prosthetic dentistry has made wonderful progress in the last few years. The manufacturers who supply the metals also deserve commendation. This industry which deals with metals to go into people's mouths is comparatively new. There is no literature on the subject, and little or no precedent by which to be guided. It was only by close cooperation with the dentist or prosthetic technician that desirable physical properties were produced, as nearly as possible, in the metals which were available and permissible. It is true that there were and still are conflicting opinions among the dentists as to the physical properties they require. Sometimes they request the impossible, such as alloys which are exceedingly stiff and springy, yet will bend or adjust easily. Even in this latter instance, progress has been made by supplying methods of heat-treatment whereby metals may be softened or hardened at will. (Figs. 1 and 2.) The demands made upon manufacturers are extremely varied. They must supply metals of tensile strengths ranging from approximately 30,000 to 100,000 lb. per sq. in. and over. The latter metals must be workable and in many instances capable of extreme deformation. They must not be affected by mouth conditions, nor should they oxidize greatly when molten, at red heat, or during a soldering operation. In addition to physical specifications, color demands must also be met. The firm of which I have the most knowledge manufacturers 11,553 standard stock articles of precious metals, taking into consideration formulas, finenesses, grades, colors, gages, lengths, sizes and weights. If special demands are taken into consideration, the number would be in excess of 25,000. Wrought metals are manufactured in a great many alloys of different sizes and shapes, such as plate, bar, rod, wire, sheet, strip, mesh and foil. There are also other products of importance.