Abstract
Corrosion resistance and mechanical properties of the dental alloy have been improved by the addition of palladium, platinum, indium, and zinc and others, to the basic alloy which consists of gold, silver, and copper.However, use of precious metals raises the price of the alloy and the surface of cast alloy is covered with black or gray black oxide film.We have manufactured trial alloys utilizing elements that contain boron in copper instead of single copper for the study of an alloy which maintains a golden color without blackish oxide film.The mechanical characteristics and color tone of the alloy were determined.The alloy containing boron-copper(B-Cu), an alloy which consists of 40wt% Au, 30wt% Ag, 10wt% Pd, 15wt% In, 2wt% Zn, and 3wt% B-Cu had the strongest tensile strength during softening heat treatment and also hardening heat treatment.An alloy consisting of 30wt% Au, 40wt% Ag, 10wt% Pd, 15wt% In, 2wt% Zn and 3wt% B-Cu had the largest elongation.An alloy consisting of 40wt% Au, 30wt% Ag, 15wt% Pd, 5wt% In, 2wt% Zn and 3wt% B-Cu had the largest hardness value.The surface of a casted alloy consisting of 30wt% Au, 40wt% Ag, 5wt% Pd, 20wt% In, 2wt% Zn and 3wt% B-Cu had a low lightness(L)value and the other trial alloys had a L value above 50.The L value for most of the trial alloys at the polished surface was above 80.The alloy consisting of 40wt% Au, 30wt% Ag, 10wt% Pd, 15wt% In, 2wt% Zn, and 3wt% B-Cu had a color resembling the low carat alloy as judged from chromaticity index a and b value.The surface of the cast alloy and the polished surface of an alloy consisting of 40wt% Au, 40wt% Ag, 5wt% Pd, 20wt% In, 2wt% Zn and 3wt% B-Cu had the largest color difference and the alloy consisting of 40wt% Au, 30wt% Ag, 10wt% Pd, 15wt% In, 2wt% Zn and 3wt% B-Cu had the lowest color difference.Lightness and saturation were compared between the 18-carat gold alloy and the trial alloys.The trial alloys showed a higher L value and lower saturation value than the 18-carat gold alloy at the surface of the cast alloy.Both had the same lightness and the former had a smaller saturation value at the polished surface.Boron acts as a deoxidizer, and the oxide tunic helped prevent the change in color of the alloy when the copper containing the boron was added.
