Pre-sintered blank for dental purposes
Pre-sintered blanks based on lithium disilicate 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 disilicate glass ceramic, wherein the blank has a relative density of from 60 to 90%, relative to the true density of the glass ceramic, and wherein the blank has a relative density which results when
(a) powder of a corresponding starting glass with an average particle size of <100 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 2 to 120 min at a temperature
(i) which temperature is at least 500° C., and
(ii) which temperature lies in a temperature range which extends over at least 30° C. and in which temperature range the relative density varies by less than 2.5%.
2. Pre-sintered blank according to claim 1 , which consists essentially of lithium disilicate glass ceramic.
3. Pre-sintered blank according to claim 1 , wherein the glass ceramic includes lithium disilicate as main crystal phase.
4. Pre-sintered blank according to claim 3 , wherein the glass ceramic contains more than 10 vol.-% lithium disilicate crystals.
5. Pre-sintered blank according to claim 3 , wherein the glass ceramic contains more than 20 vol.-% lithium disilicate crystals.
6. Pre-sintered blank according to claim 1 , wherein the lithium disilicate 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.
7. Pre-sintered blank according to claim 1 , which has at least two areas which differ by their coloration or translucence.
8. Pre-sintered blank according to claim 7 , which has at least two layers which differ by their coloration or translucence.
9. Pre-sintered blank according to claim 1 , which has a holder for securing the blank to a processing device.
10. Pre-sintered blank according to claim 1 , which has an interface for connection to a dental implant.
11. Pre-sintered blank according to claim 10 , wherein the interface comprises a recess for connection to the dental implant.
12. Pre-sintered blank according to claim 1 , wherein the blank has a relative density of from 62 to 88%, relative to the true density of the glass ceramic.
13. Pre-sintered blank according to claim 1 , wherein the blank has a relative density of from 65 to 87%, relative to the true density of the glass ceramic.
14. Pre-sintered blank according to claim 1 , wherein the lithium disilicate 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
0.1 to 10.0
Me(II)O
0.1 to 12.0
Me(III) 2 O 3
0.1 to 8.0
Me(IV)O 2
0.1 to 8.0
Me(V) 2 O 5
0.1 to 8.0
Me(VI)O 3
0.1 to 8.0
nucleating agent
0.1 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.
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 <100 μm, relative to the number of particles, is uniaxially or isostatically pressed at a pressure of from 40 to 120 MPa and
(b) the obtained glass powder green compact is heat-treated for 5 to 60 min at a temperature
(i) which temperature is at least 540° C., and
(ii) which temperature lies in a temperature range which extends over at least 50° C. and in which temperature range the relative density varies by less than 2.0%.
16. 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 <100 μm, relative to the number of particles, is uniaxially or isostatically pressed at a pressure of from 50 to 100 MPa and
(b) the obtained glass powder green compact is heat-treated for 10 to 30 min at a temperature
(i) which temperature is at least 580° C., and
(ii) which temperature lies in a temperature range which extends over at least 70° C. and in which temperature range the relative density varies by less than 1.5%.
17. Process for the preparation of dental restorations, in which
(i) the pre-sintered blank based on lithium di silicate 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.
18. Process according to claim 17 , in which the machining is carried out with computer-controlled milling and/or grinding devices.
19. Process according to claim 17 , in which
(a) lithium silicate glass in powder or granulate form is pressed to form a glass blank,
(b) the glass blank is heat-treated in order to prepare a pre-sintered blank based on lithium disilicate glass ceramic,
(i) wherein the temperature of the heat treatment is at least 500° C., and
(ii) wherein the temperature of the heat treatment lies in a temperature range which extends over at least 30° C. and in which temperature range the relative density varies by less than 2.5% and
is carried out in order to obtain the pre-sintered blank based on lithium disilicate glass ceramic.
20. Process according to claim 17 , in which the dental restorations are selected from crowns, abutments, abutment crowns, inlays, onlays, veneers, shells, bridges and overstructures.
21. A method of using the blank according to claim 1 to prepare dental restorations comprising crowns, abutments, abutment crowns, inlays, onlays, veneers, shells, bridges and overstructures.