LITHIUM DISILICATE GLASS-CERAMIC, METHOD FOR PRODUCTION THEREOF AND USE THEREOF

Abstract

The invention relates to glass-ceramics based on the lithium silicate system which can be mechanically machined easily in an intermediate step of crystallisation 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.

Claims

1. A lithium disilicate glass-ceramic comprising at least 10% by weight of a stabiliser in order to increase the chemical and mechanical stability, the stabiliser being present essentially in the amorphous phase.

2. The lithium disilicate glass-ceramic according to claim 1, wherein the stabiliser is selected from the group consisting of zirconium oxide, hafnium oxide and mixtures hereof.

3. The lithium disilicate glass-ceramic according to claim 2 having the following composition: 55 to 70% by weight of SiO.sub.2, 10 to 15% by weight of LiO.sub.2, 10 to 20% by weight of the stabiliser selected from the group consisting of ZrO.sub.2, HfO.sub.2 or mixtures hereof, 0.1 to 5% by weight of K.sub.2O, 0.1 to 5% by weight of Al.sub.2O.sub.3, 0 to 10% by weight of additives and also 0 to 10% by weight of colourants.

4. The lithium disilicate glass-ceramic according to claim 3, wherein the colourants are glass-colouring oxides and/or pigments.

5. The lithium disilicate glass-ceramic according to claim 4, wherein the glass-colouring oxides are selected from the group of the oxides of iron, titanium, cerium, copper, chromium, cobalt, nickel, manganese, selenium, silver, indium, gold, rare earth metals, in particular neodymium, praseodymium, samarium and europium.

6. The lithium disilicate glass-ceramic according to claim 4, wherein the pigments are doped spinels.

7. The lithium disilicate glass-ceramic according to claim 3, wherein the additives are selected from the group consisting of boron oxide, phosphorus oxide, fluorine, sodium oxide, barium oxide, strontium oxide, magnesium oxide, zinc oxide, calcium oxide, yttrium oxide, titanium oxide, niobium oxide, tantalum oxide, lanthanum oxide and mixtures hereof.

8. The lithium disilicate glass-ceramic according to claim 3 having the following composition: 58 to 64% by weight of SiO.sub.2, 11 to 13% by weight of LiO.sub.2, 10 to 15% by weight of the stabiliser selected from the group consisting of ZrO.sub.2, HfO.sub.2 or mixtures hereof, 2 to 5% by weight of K.sub.2O, 2 to 5% of Al.sub.2O.sub.3, 2 to 5% of P.sub.2O.sub.5 and also 0 to 5% by weight of additives and also 0 to 10% by weight of colourants.

9. A method for the production of a lithium disilicate glass-ceramic according to claim 3, wherein a) an initial glass is produced which comprises the components of the glass-ceramic, b) the initial glass is subjected to a first heat treatment in order to produce a glass-ceramic which has lithium metasilicate as main crystal phase, c) the glass-ceramic of b) is subjected to a second heat treatment in which the lithium metasilicate is converted with SiO.sub.2 from the glass phase into lithium disilicate and subsequently lithium disilicate is present as main crystal phase.

10. The method according to claim 9, wherein the first heat treatment is effected at a temperature of 620 C. to 800 C. over a period of time of 1 to 200 min, in particular of 650 C. to 750 C. over a period of time of 10 to 60 min.

11. The method according to claim 9, wherein the second heat treatment is effected at a temperature of 800 C. to 1,040 C. over a period of time of 5 to 200 min, in particular of 650 C. to 750 C. over a period of time of 5 to 30 min.

12. The lithium disilicate glass-ceramic of claim 3, wherein the glass-ceramic is a dental material or component of a dental material.

13. The lithium disilicate glass-ceramic of claim 12 in the form of an inlay, an onlay, a bridge, a pin construction, a veneer, a (partial) crown.

Description

EXAMPLES 1 TO 6

[0029] In examples 1 to 6, compositions of glasses with a high zirconium oxide content are indicated, which are converted by a two-step temperature treatment firstly into readily mechanically machinable lithium metasilicate glass-ceramics and subsequently into highly-translucent, very strong and chemically-stable lithium disilicate glass-ceramics.

[0030] The compositions with their components are represented in Table 1.

TABLE-US-00001 TABLE 1 81 82 83 84 85 86 Si0.sub.2 66.9 65.8 65.5 63.7 63.5 63.5 Li.sub.20 13.9 13.7 13.6 13.2 14.4 12.9 Zr0.sub.2 10.0 10.0 12.0 11.7 12.7 13.5 Al.sub.20.sub.3 3.2 3.1 3.1 3.0 3.3 3.5 P.sub.20.sub.5 3.0 3.0 3.0 2.9 3.1 3.4 K.sub.20 2.9 2.9 2.9 2.8 3.0 3.2 Ce0.sub.2 1.0 2.0 Er.sub.20.sub.3 0.2 0.3 Tb.sub.20.sub.3 0.3 0.3

[0031] The glasses were melted at 1,500 C. and poured into metal moulds to form blocks. The blocks were stress-relieved at 560 C. in the furnace and cooled slowly. For the different characterisation processes, the glass blocks were divided up and subjected to a first crystallisation treatment. For this purpose, the glasses were aged for 10 to 120 minutes at 600 C. to 750 C. As a result, glass-ceramics with strength values of 150 MPa to 220 MPa were produced. Exclusively lithium metasilicate was hereby established as crystal phase. In this state, machining by means of CAD/CAM methods is very readily possible.

[0032] With a second short crystallisation at 800 C. to 950 C. for 3 to 15 minutes, recrystallisation of the lithium metasilicate with amorphous SiO.sub.2 from the glass phase takes place to form lithium disilicate and the result is an increase in strength to 300 MPa to 450 MPa. In addition to the lithium disilicate phase, a subsidiary crystal phase with a zirconium oxide content can hereby be produced. In addition, also small residues of lithium metasilicate can be present. The unequivocal main crystal phase is lithium disilicate.

[0033] In Table 2, the crystallisation conditions of individual glasses and also the resulting crystal phases and strength values are displayed.

TABLE-US-00002 TABLE 2 Glass 81 82 83 84 85 86 1. Crystallisation 650 C. 700 C. 650 C. 700 C. 700 C. 700 C. 20 min 40 min 30 min 20 min 40 min 40 min 2. Crystallisation 850 C. 830 C. 870 C. 850 C. 820 C. 830 C. 10 min 10 min 20 min 8 min 10 min 10 min Crystal phases Main phase (>80%) disilicate disilicate disilicate disilicate disilicate disilicate Subsidiary phase (<20%) metasilicate metasilicate Translucence excellent very good excellent very good excellent excellent 3-point bending strength 375 MPa 413 MPa 380 MPa 418 MPa 356 MPa 385 MPa