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 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.

Claims

1. (canceled)

2. A method of producing a shaped lithium disilicate dental product, comprising: a) producing an initial glass, wherein the amount of SiO.sub.2 is 55 to 70 weight percent, the amount of Li.sub.2O is 10 to 15 weight percent, the amount of K.sub.2O is 0.1 to 5 weight percent, the amount of A1203 is 0.1 to 5 weight percent, the amount of P.sub.2O.sub.5 is 2 to 5 weight percent, and the amount of ZrO.sub.2 is at least 10.0 weight percent, wherein the total weight percent is 100 weight percent; b) subjecting the initial glass to a first heat treatment in order to produce a glass-ceramic which has lithium metasilicate as the main crystal phase; c) forming a shaped dental product out of the glass-ceramic; and d) forming a shaped lithium disilicate dental product by subjecting the shaped dental product 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 the main crystal phase.

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 AI.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 disilicate disilicate disilicate disilicate disilicate disilicate (>80%) Subsidiary phase — — — — metasilicate metasilicate (<20%) Translucence excellent very good excellent very good excellent excellent 3-point 375 MPa 413 MPa 380 MPa 418 MPa 356 MPa 385 MPa bending strength