A dental porcelain, a method of producing a dental restoration, a dental alloy

Claim 2

A dental porcelain as claimed in claim 1, characterized by a thermal expansion coefficient, measured at a temperature of from 20 to 500°C, above 15.0 µm/m.°C and a firing temperature below 900°C.

Claim 3

A dental porcelain as claimed in claim 1 or 2, prepared from at least three different glass compositions, including (a) one or more leucite-forming glass compositions having a thermal expansion coefficient, measured at a temperature of from 20 to 500°C, above 17.0 µm/m.°C, which consist essentially of 15-20 wt.% Al₂O₃, 13-19 wt.% K₂O, 0-5 wt.% Na₂O, balance SiO₂, additives and impurities, (b) one or more glass compositions having a thermal expansion coefficient, measured at a temperature of from 20 to 500°C, above 8.0-12.0 µm/m.°C and a melting point of 750-950°C, which consist essentially of 10-15 wt.% Al₂O₃, 4-7 wt.% K₂O, 6-15 wt.% Na₂O, 0-3 wt.% BaO, 0-3 wt.% Li₂O, balance SiO₂, additives and impurities, and (c) one or more low melting glass compositions having a melting point of 450-700°C, which consist essentially of 0-5 wt.% Al₂O₃, 12-30 wt.% Na₂O + K₂O, 0-5 wt.% BaO, 0-5 wt.% Li₂O, balance SiO₂, additives and impurities.

Claim 4

A dental porcelain as claimed in claim 3, prepared from 50-80 wt.% of one or more glass compositions of type (a), 5-45 wt.% of one or more glass compositions of type (b), and 5-15 wt.% of a glass composition of type (c).

Claim 6

A method as claimed in claim 5, characterized by applying a dental alloy having a thermal expansion coefficient, measured at a temperature of from 20 to 500°C, which is higher than that of the dental porcelain by 0.5-1.5 µm/m.°C and has a solidus temperature which is higher by at least 50°C, preferably at least 100°C, than the temperature at which the dental porcelain is fired on.

Claim 7

A method as claimed in claim 5 or 6, characterized by firing on dental porcelain while the dental restoration rests on a graphite plate and is shielded from the kiln atmosphere by means of a bell jar of quartz glass.

Claim 8

A dental alloy, characterized by a thermal expansion coefficient, measured at a temperature of from 20 to 500°C, above 14.5 µm/m.°C and a solidus temperature of at least 1000°C.

Claim 9

A dental alloy as claimed in claim 8, characterized by a thermal expansion coefficient, measured at a temperature of from 20 to 500°C, of 15-18 µm/m.°C and a solidus temperature of 1000-1200°C.

Claim 10

A dental alloy as claimed in claim 8 or 9, characterized by a composition consisting essentially of 40-80 wt.% Au; 15-50 wt.% Ag; 0-20 wt.% of Pd + Pt, with the understanding that when Pd and Pt are both present one of both is present at a content of not more than 4 wt.%; 0-5 wt.% in total of one or more elements from the group consisting of Zn, In, Sn, Ga, Ge, Al, Si and B; 0-5 wt.% in total of one or more elements from the group consisting of Ta, Ti and Re; 0-5 wt.% in total of one or more elements from the group consisting of Rh, Ir and Ru; 0-5 wt.% in total of one or more elements from the group consisting of Mo, Nb, W, Cr, Cu, Co, Ni and Fe; 0-3 wt.% in total of one or more elements from the group consisting of Sc, Y, La and the rare earths; balance additives and impurities.

Claim 11

A dental alloy as claimed in claim 10, characterized by a composition consisting essentially of 45-75 wt.% Au; 20-40 wt.% Ag; 4-12 wt.% Pd and 0-2 wt.% Pt, or conversely, 4-12 wt.% Pt, and 0-2 wt.% Pd; 0.05-0.5 wt.% Ir; 0.5-2.0 wt.% Zn; 0-1.0 wt.% Sn; 0-0.5 wt.% Ta; balance impurities.