Lithium silicate materials are described which can be easily processed by machining to dental products without undue wear of the tools and which subsequently can be converted into lithium silicate products showing high strength.

Quartz solid solution glass ceramics and precursors thereof are described, which are characterized by very good mechanical and optical properties and in particular can be used as restoration material in dentistry.

Glass ceramics having SiO.sub.2 as main crystal phase and precursors thereof are described which are characterized by very good mechanical and optical properties and in particular can be used as restoration material in dentistry.

The invention relates to a method for the preparation of a glass ceramic or a glass, which comprise cerium ions and are suitable in particular for the preparation of dental restorations, the fluorescence properties of which largely correspond to those of natural teeth. The invention also relates to a glass ceramic and a glass which can be obtained using the method according to the invention, the use thereof as dental material and in particular for the preparation of dental restorations, as well as a glass-forming composition which is suitable for use in the method according to the invention.

ZrO.sub.2-toughened glass ceramics having high molar fractions of tetragonal ZrO.sub.2 and fracture toughness value of greater than 1.8 MPa.Math.m.sup.1/2. The glass ceramic may also include also contain other secondary phases, including lithium silicates, that may be beneficial for toughening or for strengthening through an ion exchange process. Additional second phases may also decrease the coefficient of thermal expansion of the glass ceramic. A method of making such glass ceramics is also provided.

ZrO.sub.2-toughened glass ceramics having high molar fractions of tetragonal ZrO.sub.2 and fracture toughness value of greater than 1.8 MPa.Math.m.sup.1/2. The glass ceramic may also include also contain other secondary phases, including lithium silicates, that may be beneficial for toughening or for strengthening through an ion exchange process. Additional second phases may also decrease the coefficient of thermal expansion of the glass ceramic. A method of making such glass ceramics is also provided.

The invention relates to a method to increase the strength of a form body of lithium silicate glass ceramic, which after it has a desired end geometry and after the application of a material which influences its surface to form a coating, is subject to a heat treatment. To create a surface compressive stress through the replacement of lithium ions by alkali ions of greater diameter at least that region not covered by the application layer is covered by a melt or paste consisting of or containing a salt of an alkali metal with ions of greater diameter and the form body is in contact with the melt or paste for a period of time t at a temperature T and the melt or paste is subsequently removed from the form body.

The present invention relates to a blank for dental purposes which has a first and a second layer which, independently of each other, are based on glass, glass-ceramic or ceramic, wherein the first layer and the second layer differ in colour and form a boundary surface, wherein the boundary surface runs obliquely.

The invention relates to a glazing composition for a porous dental zirconia article, the glazing composition comprising liquid, glass particles, fluorescing component(s) comprising europium, optionally hydrophilic silica nano-particles, and optionally hydrophobic silica nano-particles, wherein the fluorescing component(s) can be contained in the glass particles or as separate component. The invention also relates to a process for sintering a porous dental zirconia article with a glazing composition on its surface.

The present invention provides a dental product comprising a base material formed of a zirconia sintered body, and having high aesthetic quality with enhanced fracture toughness and with reduced chipping and cracking in the porcelain layer. The present invention also provides a method for manufacturing such a dental product. The present invention relates to a dental product comprising: a base material formed of a zirconia sintered body, and a porcelain layer, wherein the porcelain of the porcelain layer has a suitable firing temperature of 900° C. or more, and the porcelain layer has a fracture toughness value of 1.20 MPa.Math.m.sup.0.5 or more.