Lithium disilicate glass-ceramics

Abstract

This invention is directed to lithium disilicate (Li Si O ) based glass-ceramics comprising silica, lithium oxide, alumina, potassium oxide and phosphorus pentoxide. The glass-ceramics are useful in the fabrication of single and multi-unit dental restorations (e.g. anterior bridges) made by heat pressing into refractory investment molds produced using lost wax techniques. The glass-ceramics have good pressability, i.e., the ability to be formed into dental articles by heat-pressing using commercially available equipment. In accordance with one embodiment directed to the process of making the glass-ceramics, the compositions herein are melted at about 1200 ° to about 1600 ° C., thereafter cast into steel molds in the shape of cylindrical blanks (pellets), or alternately, cooled to the crystallization temperature. The resulting glass blank are heat-treated to form glass-ceramic blanks via a one or two step heat-treatment cycle preferably in the temperature range of about 400 ° to about 1100 ° C. The resulting glass-ceramic pressable pellets and/or blanks of desired shapes, sizes and structures are later pressed into dental restorations. Alternatively, instead of forming into pressable pellets or blanks, the pulverized powder is used to form a dental restoration using the refractory die technique or platinum foil technique.