Pre-sintered blank for dental purposes
Pre-sintered blanks based on lithium metasilicate glass ceramic are described which are suitable in particular for the preparation of dental restorations.
1. Pre-sintered blank for dental purposes based on lithium metasilicate glass ceramic, wherein the blank has a relative density of from 66 to 90% relative to a blank of same composition that has been fully sintered to a lithium disilicate glass ceramic and wherein the pre-sintered blank has layers which differ in color or translucence.
2. Pre-sintered blank according to claim 1 , wherein the relative density is from 68 to 88%, relative to a blank of same composition that has been fully sintered to a lithium disilicate glass ceramic.
3. Pre-sintered blank according to claim 1 , wherein the relative density is from 70 to 86%, relative to a blank of same composition that has been fully sintered to a lithium disilicate glass ceramic.
4. Pre-sintered blank according to claim 1 , wherein the layers comprise at least three layers.
5. Pre-sintered blank according to claim 1 , wherein the layers comprise up to ten layers.
6. Pre-sintered blank according to claim 1 , wherein the layers have a color gradient to ensure continuous color transition.
7. Pre-sintered blank according to claim 1 , which consists substantially of lithium metasilicate glass ceramic.
8. Pre-sintered blank according to claim 1 , wherein the glass ceramic includes lithium metasilicate as main crystal phase and contains more than 20 vol.-% lithium metasilicate crystals.
9. Pre-sintered blank according to claim 8 , wherein the glass ceramic contains more than 25 vol.-% lithium metasilicate crystals.
10. Pre-sintered blank according to claim 8 , wherein the glass ceramic contains more than 30 vol.-% lithium metasilicate.
11. Pre-sintered blank according to claim 1 , wherein the lithium metasilicate glass ceramic contains at least one of the following components:
Component
wt.-%
SiO 2
50.0 to 80.0
Li 2 O
6.0 to 20.0
Me(I) 2 O
0 to 10.0
Me(II)O
0 to 12.0
Me(III) 2 O 3
0 to 8.0
Me(IV)O 2
0 to 8.0
Me(V) 2 O 5
0 to 8.0
Me(VI)O 3
0 to 8.0
nucleating agent
0 to 8.0
wherein
Me(I) 2 O is selected from Na 2 O, K 2 O, Rb 2 O, Cs 2 O or mixtures thereof,
Me(II)O is selected from CaO, BaO, MgO, SrO, ZnO and mixtures thereof,
Me(III) 2 O 3 is selected from Al 2 O 3 , La 2 O 3 , Bi 2 O 3 , Y 2 O 3 , Yb 2 O 3 and mixtures thereof,
Me(IV)O 2 is selected from ZrO 2 , TiO 2 , SnO 2 , GeO 2 and mixtures thereof,
Me(V) 2 O 5 is selected from Ta 2 O 5 , Nb 2 O 5 and mixtures thereof,
Me(VI)O 3 is selected from WO 3 , MoO 3 and mixtures thereof, and
nucleating agent is selected from P 2 O 5 , metals and mixtures thereof.
12. Pre-sintered blank according to claim 1 , which has a holder for a processing device.
13. Pre-sintered blank according to claim 1 , which has an interface in the form of a recess, for connection to a dental implant.
14. Pre-sintered blank according to claim 1 , which is obtainable by the process of arranging differently colored or differently translucent powders or granulates in layers on top of one another in a compression mold.
15. Pre-sintered blank according to claim 1 , which has a relative density which results when
(a) powder of a corresponding starting glass with an average particle size of <50 μm, relative to the number of particles, is uniaxially or isostatically pressed at a pressure of from 20 MPa to 200 MPa and
(b) the obtained glass powder green compact is heat-treated for 5 to 60 min at a temperature which
(i) is at least 500° C., and
(ii) lies in a range which extends over at least 30K and in which the relative density varies by less than 2.5%.
16. Pre-sintered blank according to claim 15 , wherein the powder of the corresponding starting glass is uniaxially or isostatically pressed at a pressure of from 40 MPa to 120 MPa and the obtained glass powder green compact is heat-treated for 10 to 40 min at a temperature which is at least 540° C., and lies in a range which extends over at least 50K and in which the relative density varies by less than 2.0%.
17. Pre-sintered blank according to claim 15 , wherein the powder of the corresponding starting glass is uniaxially or isostatically pressed at a pressure of from 50 MPa to 100 MPa and the obtained glass powder green compact is heat-treated for 15 to 30 min at a temperature which is at least 580° C., and lies in a range which extends over at least 70K and in which the relative density varies by less than 1.5%.
18. Process for the preparation of the pre-sintered blank according to claim 1 , in which
(a) layers of differently colored or differently translucent lithium silicate glass powders or granulates are pressed to form a glass blank,
(b) the glass blank is heat-treated in order to prepare a pre-sintered blank based on lithium metasilicate glass ceramic, wherein the temperature of the heat treatment
(i) is at least 500° C., and
(ii) lies in a range which extends over at least 30K, and in which the relative density varies by less than 2.5%.
19. Process for the preparation of the blank according to 18 , wherein the temperature of the heat treatment is at least 540° C., and lies in a range which extends over at least 50K and in which the relative density varies by less than 2.0%.
20. Process for the preparation of the blank according to 18 , wherein the temperature of the heat treatment is at least 580° C., and lies in a range which extends over at least 70K, and in which the relative density varies by less than 1.5%.
21. Process for the preparation of dental restorations, in which
(i) the pre-sintered blank based on lithium metasilicate glass ceramic according to claim 1 is shaped by machining to form a precursor of the dental restoration,
(ii) the precursor is substantially dense-sintered in order to produce the dental restoration, and
(iii) optionally the surface of the dental restoration is provided with a finish.
22. Process according to claim 21 , in which the machining is carried out with computer-controlled milling and/or grinding devices.
23. Process according to claim 21 , in which the dental restorations are selected from crowns, abutments, abutment crowns, inlays, onlays, veneers, shells, bridges and overstructures.
24. Process of using the blank according to claim 1 to prepare dental restorations comprising crowns, abutments, abutment crowns, inlays, onlays, veneers, shells, bridges and overstructures.
25. Pre-sintered blank according to claim 1 , wherein the fully sintered lithium disilicate glass ceramic is obtainable by treating the pre-sintered blank for 20 min in a furnace heated to 920° C.