High strength feldspathic dental porcelains containing crystalline leucite

Claim 1

A method of preparing a translucent feldspathic dental composition exhibiting a crystalline leucite content of at least about 45% by weight, wherein said leucite crystallites exhibit a size of less than about 35 microns, comprising the steps of: (a) culling a feldspar having the composition comprising: ______________________________________ Component Percentage (by weight) ______________________________________ SiO.sub.2 64-67 Al.sub.2 O.sub.3 17-20 CaO 0.5-1.0 K.sub.2 O 12.0-14.0 Na.sub.2 O 1.0-3.0 ______________________________________ to remove quartz, mica and biotite; (b) grinding said feldspar; (c) passing said ground feldspar through a 200 mesh screen; (d) blending the screened feldspar with potassium nitrate, potassium silicate, lithium carbonate, calcium carbonate, magnesium oxide, cerium oxide, alumina and/or aluminum silicate in quantities such that the resultant feldspathic dental porcelain composition, after fusion, comprises: ______________________________________ Component Percentage (by weight) ______________________________________ SiO.sub.2 55-70 Al.sub.2 O.sub.3 16-20 CaO 0.5-5.0 MgO 0.5-5.0 Li.sub.2 O 1.0-5.0 Na.sub.2 O 2.0-5.0 K.sub.2 O 12.5-22.5 Ce.sub.2 O.sub.3 0-1.0 ______________________________________ (e) fusing said feldspathic dental porcelain composition at from about 2150° to about 2350° for from about 2 to about 10 hours at a heat-up rate of about 400° F./hour, thereby forming a magma; (f) cooling said magma at about 5° F./minute to about 1900° F.; (g) holding said cooled magma at about 1900° F. for from about one to about four hours; (h) quenching said cooled magma in water; and (i) milling said quenched magma such that 95% thereof passes through a 180 mesh screen, thereby forming said translucent feldspathic dental porcelain composition.

Claim 2

A method of preparing a translucent feldspathic dental composition exhibiting a crystalline leucite content of at least about 45% by weight, wherein said leucite crystallites exhibit a size of less than about 35 microns, comprising the steps of: (a) culling a feldspar having the composition comprising: ______________________________________ Component Percentage (by weight) ______________________________________ SiO.sub.2 64-67 Al.sub.2 O.sub.3 17-20 CaO 0.5-1.0 K.sub.2 O 12.0-14.0 Na.sub.2 O 1.0-3.0 ______________________________________ to remove quartz, mica and biotite; (b) grinding said feldspar; (c) passing said ground feldspar through a 200 mesh screen; (d) blending the screened feldspar with potassium nitrate, potassium silicate, lithium carbonate, calcium carbonate, magnesium oxide, cerium oxide, alumina and/or aluminum silicate in quantities such that the resultant feldspathic dental porcelain composition, after fusion, comprises: ______________________________________ Component Percentage (by weight) ______________________________________ SiO.sub.2 55-70 Al.sub.2 O.sub.3 16-20 CaO 0.5-5.0 MgO 0.5-5.0 Li.sub.2 O 1.0-5.0 Na.sub.2 O 2.0-5.0 K.sub.2 O 12.5-22.5 Ce.sub.2 O.sub.3 0-1.0 ______________________________________ (e) fusing said feldspathic dental porcelain composition at from about 2150° to about 2350° for from about 2 to about 10 hours at a heat-up rate of about 400° F./hour, thereby forming a magma; (f) cooling said magma at about 5° F./minute to about 1900° F.; (g) holding said cooled magma at about 1900° F. for from about one to about four hours; (h) quenching said cooled magma in water; and (i) milling said quenched magma such that 95% thereof passes through a 180 mesh screen, thereby forming said translucent feldspathic dental porcelain composition.