The invention relates to a process for the preparation of a glass-ceramic blank for dental purposes with lithium silicate as crystal phase, in which lithium silicate blanks that are no longer required and in particular residues thereof are used as starting material and which allows the production of a homogeneous starting glass within a short time.

The invention relates to glass-ceramics based on the lithium silicate system which can be mechanically machined easily in an intermediate step of crystallization and, after complete crystallisation, represent a very strong, highly-translucent and chemically-stable glass-ceramic Likewise, the invention relates to a method for the production of these glass-ceramics. The glass-ceramics according to the invention are used as dental material.

Provided is a dental bulk block made from a glass-ceramic material having a crystalline phase embedded in an amorphous glass matrix. The crystalline phase includes eucryptite and at least one lithium silicate-based crystalline phase selected from the group consisting of lithium metasilicate and lithium disilicate. The dental bulk block is a functionally graded material having a crystalline size gradient with respect to a depth thereof and having no interface at a point of change in main crystalline size gradient value. The bulk block that is heat-treated at 820° C. for 40 minutes exhibits a characteristic peak of a spodumene crystalline phase in an X-ray diffraction analysis result graph unlike the bulk block that is heat-treated at 820° C. for 2 minutes.

A lithium silicate glass ceramic having lithium metasilicate as main crystal phase and having not more than 30 wt.-% of lithium metasilicate crystals and having the following components in the amounts indicated:

TABLE-US-00001 Component Wt.-% SiO.sub.2 71.0 to 82.0 Li.sub.2O 6.0 to 14.0 Me.sup.I.sub.2O 4.0 to 15.0 Al.sub.2O.sub.3 2.0 to 10.0 P.sub.2O.sub.5 0.5 to 7.0,
wherein Me.sup.I.sub.2O is selected from Na.sub.2O, K.sub.2O, Rb.sub.2O, Cs.sub.2O and mixtures thereof, and
wherein the molar ratio of SiO.sub.2 to Li.sub.2O is in the range of 2.5 to 5.0.

A lithium silicate glass ceramic having lithium metasilicate as main crystal phase and having not more than 30 wt.-% of lithium metasilicate crystals.

The present invention provides a silicate glass that can reduce a color change in base material zirconia even when simultaneously fired with an unsintered zirconia. The present invention also provides a dental product using same. The present invention relates to a silicate glass comprising: 65.0 to 90.0 mol % SiO.sub.2, 4.0 to 15.0 mol % Al.sub.2O.sub.3, 1.0 to 10.0 mol % K.sub.2O, 0.1 to 7.0 mol % Na.sub.2O, and 0.01 to 15.0 mol % CaO, the silicate glass being essentially free of B.sub.2O.sub.3, and satisfying the relation {(number of moles of Al.sub.2O.sub.3)/(total number of moles of RO+R.sub.2O)}≥0.70, wherein R in the metal oxide represented by RO represents a metallic element in group 2 or 12 of the periodic table, and R in the metal oxide represented by R.sub.2O represents a metallic element in group 1 of the periodic table. The present invention also relates to a composite comprising the silicate glass and a base material formed of a ceramic; a sintered body as a fired product of the composite; and a dental product comprising the sintered body.

The present invention relates to a spinel glass-ceramic made from a composition with the components 25 to 50% by weight SiO.sub.2, 10 to 35% by weight Al.sub.2O.sub.3, 1 to 15% by weight MgO, 1 to 15% by weight P.sub.2O.sub.5, 1 to 25% by weight ZrO.sub.2 and/or TiO.sub.2, 0 to 20% by weight La.sub.2O.sub.3, 0 to 10% by weight B.sub.2O.sub.3, and 0 to 15% by weight additives. The spinel glass-ceramic contains at least one spinel phase, but no high quartz solid solution phase. The glass-ceramic according to the invention exhibits very high mechanical stability, for example, very high flexural strength, wherein its optical properties can be simultaneously adjusted. In addition, the present invention also relates to a method for producing and the use of the spinel glass-ceramic. Furthermore, the present invention relates to a shaped dental product containing the spinel glass-ceramic.

One aspect of the invention includes a glass powder for a chemical polymerization initiator, the glass powder including aluminum, silicon, and at least one of copper or vanadium.

A method of manufacture of a dental prosthesis is described, comprising using a rotary milling or drilling tool (16) to mill or drill a block (12) of a sintered ceramic material. The use of a tool (16) to mill or drill material from a block (12) of a sintered ceramic material such as lithium silicate or lithium disilicate allows manufacture of a glass ceramic dental prosthesis in a relatively efficient manner.

The present invention relates to a glass ceramic material comprising a core-rim structure, wherein the core-rim structure comprises an amorphous SiO.sub.2 matrix, ZrO.sub.2 crystals, and hardness-enhancing additive, the ZrO.sub.2 crystals are present in cores that are at least partly surrounded by a rim comprising hardness-enhancing additive.