Lithium Silicate Diopside Glass Ceramics

Abstract

Lithium silicate-diopside glass ceramics are described which are characterized by a controllable translucence and can be satisfactorily processed mechanically and therefore can be used in particular as restoration material in dentistry.

Claims

1. Lithium silicate-diopside glass ceramic which comprises lithium silicate as main crystal phase and diopside as further crystal phase.

2. Glass ceramic according to claim 1, which comprises 53.0 to 75.0 wt.-% SiO.sub.2.

3. Glass ceramic according to claim 1, which comprises 10.0 to 23.0 wt.-% Li.sub.2O.

4. Glass ceramic according to claim 1, which comprises 1.0 to 13.0 wt.-% CaO and/or 1.0 to 12.0 wt.-% MgO.

5. Glass ceramic according to claim 4, wherein the molar ratio of CaO to MgO is 0.5 to 2.0.

6. Glass ceramic according to claim 1, which comprises 0 to 8.0 O.sub.5.

7. Glass ceramic according to claim 1, which comprises 0 to 10.0 wt.-% further alkali metal oxide Me.sup.I.sub.2O, wherein Me.sup.I.sub.2O is selected from Na.sub.2O, K.sub.2O, Rb.sub.2O and/or Cs.sub.2O.

8. (canceled)

9. Glass ceramic according to claim 1, which comprises 0 to 10.0 wt.-% oxide of trivalent elements Me.sup.III.sub.2O.sub.3, wherein Me.sup.III.sub.2O.sub.3 is selected from Al.sub.2O.sub.3, B.sub.2O.sub.3, Y.sub.2O.sub.3, La.sub.2O.sub.3, Ga.sub.2O.sub.3 and/or In.sub.2O.sub.3.

10. (canceled)

11. (canceled)

12. (canceled)

13. Glass ceramic according to claim 1, which comprises the following components: TABLE-US-00010 Component wt.-% SiO.sub.2 53.0 to 75.0 Li.sub.2O 10.0 to 23.0 CaO 1.0 to 13.0 MgO 1.0 to 12.0 P.sub.2O.sub.5 0 to 8.0 Me.sup.I.sub.2O 0 to 10.0 Me.sup.IIO 0 to 10.0 Me.sup.III.sub.2O.sub.3 0 to 10.0 Me.sup.IVO.sub.2 0 to 15.0 Me.sup.V.sub.2O.sub.5 0 to 4.0 Me.sup.VIO.sub.3 0 to 5.0 fluorine 0 to 3.0, wherein Me.sup.I.sub.2O is selected from Na.sub.2O, K.sub.2O, Rb.sub.2O and/or Cs.sub.2O, Me.sup.IIO is selected from SrO and/or ZnO, Me.sup.III.sub.2O.sub.3 is selected from Al.sub.2O.sub.3, B.sub.2O.sub.3, Y.sub.2O.sub.3, La.sub.2O.sub.3, Ga.sub.2O.sub.3 and/or In.sub.2O, Me.sup.IVO.sub.2 is selected from ZrO.sub.2, GeO.sub.2, CeO.sub.2 TiO.sub.2 and/or SnO.sub.2, Me.sup.V.sub.2O.sub.5 is selected from V.sub.2O.sub.5 Ta.sub.2O.sub.5 and/or Nb.sub.2O.sub.5 and Me.sup.VIO.sub.3 is WO.sub.3 and/or MoO.sub.3.

14. (canceled)

15. Glass ceramic according to claim 1, which comprises lithium silicate in the form of lithium disilicate and/or lithium metasilicate.

16. (canceled)

17. (canceled)

18. (canceled)

19. Glass ceramic according to claim 1, which is present in the form of a blank or a dental restoration.

20. Starting glass which comprises the components of the glass ceramic according to claim 1.

21. Starting glass according to claim 20, which is present in the form of a ground powder or a compact made of ground powder.

22. Process for the preparation of the glass ceramic according to claim 1, wherein (a) the starting glass according to claim 20 is ground, (b) the ground starting glass is optionally pressed to form a powder green compact and (c) the ground starting glass or the powder green compact is subjected to at least one heat treatment at a temperature in the range of from 500° to 1000° C. for a period of from 5 to 120 min.

23. (canceled)

24. (canceled)

25. Glass ceramic according to claim 1, which comprises 53.0 to 70.0 wt.-% SiO.sub.2.

26. Glass ceramic according to claim 1, which comprises 2.0 to 8.0 wt.-% P.sub.2O.sub.5.

27. Glass ceramic according to claim 1, which comprises 3.0 to 6.0 wt.-% P.sub.2O.sub.5.

28. Glass ceramic according to claim 1, which comprises 0.5 to 10.0 wt.-% further alkali metal oxide Me.sup.I.sub.2O, wherein Me.sup.I.sub.2O is selected from Na.sub.2O, K.sub.2O, Rb.sub.2O and/or Cs.sub.2O.

29. Glass ceramic according to claim 1, which comprises 0.5 to 8.0 further alkali metal oxide Me.sup.I.sub.2O, wherein Me.sup.I.sub.2O is selected from Na.sub.2O, K.sub.2O, Rb.sub.2O and/or Cs.sub.2O.

30. Glass ceramic according to claim 1, which comprises 1.0 to 5.0 wt.-% further alkali metal oxide Me.sup.I.sub.2O, wherein Me.sup.I.sub.2O is selected from Na.sub.2O, K.sub.2O, Rb.sub.2O and/or Cs.sub.2O.

31. Glass ceramic according to claim 1, which comprises 0.1 to 8.0 wt.-% Al.sub.2O.sub.3.

32. Glass ceramic according to claim 1, which comprises 1.0 to 7.0 wt.-% Al.sub.2O.sub.3.

33. Glass ceramic according to claim 1, which comprises 2.0 to 5.0 wt.-% Al.sub.2O.sub.3.

34. Process for the preparation of dental restorations, wherein the glass ceramic according to claim 1 is given the shape of the desired dental restoration by pressing or machining.

35. Process according to claim 34, wherein the dental restoration is selected from bridge, inlay, onlay, veneer, abutment, partial crown, crown and shell.

Description

EXAMPLES

Examples 1 to 22—Composition and Crystal Phases

[0077] In total, 22 glasses and glass ceramics with the composition specified in Table I were prepared.

[0078] The following meanings apply in Table I:

TABLE-US-00008 T.sub.g glass transition temperature, determined by means of DSC T.sub.S and t.sub.S temperature and time used for melting the starting glass T.sub.Sinter and t.sub.Sinter temperature and time used for the heat treatment and thus crystallization of compacts T.sub.Press and t.sub.Press temperature and time used for pressing crystallized compacts L*a*b value key for characterizing the colour CR value contrast value of the glass ceramic according to British Standard BS 5612 Li.sub.2Si.sub.2O.sub.5 lithium disilicate Li.sub.2SiO.sub.3 lithium metasilicate CaMgSi.sub.2O.sub.6 diopside SiO.sub.2 quartz, in particular low quartz, or cristobalite Cs.sub.0.809AlSi.sub.5O.sub.12 caesium alumosilicate

[0079] In Examples 1 to 22 glasses from usual raw materials were melted in a platinum crucible at the temperature T.sub.S for a period t.sub.S. Glass frits, i.e. glass granules, were prepared by pouring the melted starting glasses into water. For the further processing of the glass frits, the three process variants A), B) and C) specified below were used:

A) Vibratory Mills

[0080] The glass frits prepared according to Examples 1 to 9, 11 to 19, 21 and 22 were ground with a KM100 vibratory mill from Retsch GmbH, Haan, Germany, and an RM31 zirconium oxide vibratory mill from Retsch GmbH, Haan, Germany to an average particle size of <90 μm, relative to the number of particles. The ground glass powder was then pressed uniaxially to form a small cylinder and crystallized and sintered in a Programat-type furnace (Ivoclar Vivadent AG) at the temperature T.sub.Sinter for the period t.sub.Sinter. X-ray diffraction analyses were carried out on the test pieces prepared to determine the crystal phases present and colour measurements were also carried out.

B) Jet Mill

[0081] The glass frit with the composition according to Example 10 was ground in an AFG 100 opposed jet mill from Hosokawa Alpine to an average particle size of 20 μm, relative to the number of particles. The ground glass powder was then pressed uniaxially and crystallized and sintered in a Programat-type furnace (Ivoclar Vivadent AG) at the temperature T.sub.Sinter for the period t.sub.Sinter. Colour measurements and X-ray diffraction analyses were carried out on the test pieces prepared in this way. The CR value of the lithium silicate-diopside glass ceramic produced was 69.95.

C) Ball Mill

[0082] The glass frit with the composition according to Example 20 was ground in a ball mill for a period of about 20 h to an average particle size of 10 μm, relative to the number of particles. The ball mill had, as grinding chamber, a cylindrical porcelain container with a volumetric capacity of 1. The following mixture of porcelain grinding balls was used as grinding medium: 0.9 kg with 10 mm diameter, 1.8 kg with 20 mm diameter and 0.9 kg with 30 mm diameter. The ground glass powder was then pressed uniaxially and crystallized and sintered in a Programat-type furnace (Ivoclar Vivadent AG) at the temperature T.sub.Sinter for the period t.sub.Sinter. Colour measurements and X-ray diffraction analyses were carried out on the test pieces prepared in this way to determine the crystal phases. The content of diopside crystals in this glass ceramic was higher than in the glass ceramics prepared according to variants A) and B).

TABLE-US-00009 TABLE I Example No. 1 2 3 4 5 6 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 67.1 60.9 68.5 61.1 67.6 66.9 Li.sub.2O 14.0 21.7 14.2 14.3 14.0 13.8 CaO 5.2 8.7 4.2 5.1 4.1 3.9 MgO 3.8 8.7 3.0 3.7 3.0 2.8 Na.sub.2O — — — — — — K.sub.2O 3.6 — 3.7 3.4 3.3 3.4 Cs.sub.2O — — — — — — Rb.sub.2O — — — — 1.7 — ZnO — — — — — — SrO — — — — — — Al.sub.2O.sub.3 3.2 — 3.3 3.1 3.2 4.0 B.sub.2O.sub.3 — — — — — — Y.sub.2O.sub.3 — — — — — — La.sub.2O.sub.3 — — — — — — Er.sub.2O.sub.3 — — — — — — ZrO.sub.2 — — — 5.9 — — CeO.sub.2 — — — — — — P.sub.2O.sub.5 3.1 — 3.1 3.4 3.1 5.2 V.sub.2O.sub.5 — — — — — — Nb.sub.2O.sub.5 — — — — — — WO.sub.3 — — — — — — F — — — — — — GeO.sub.2 — — — — — — T.sub.g/° C. 456.9 454.2 455.2 462.6 T.sub.s/° C., t.sub.s/min 1500, 120 1500, 120 1500, 120 1500, 120 1500, 150 T.sub.Sinter/° C., t.sub.Sinter/min 800, 5  930, 10 780, 8  800, 8 840, 5  830, 5  T.sub.Press/° C., t.sub.Press/° C. 910, 25 Main crystal phase Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2SiO.sub.3 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 (Sinter) Li.sub.2SiO.sub.3 (Sinter and press) Further crystal CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, phases Li.sub.2SiO.sub.3, SiO.sub.2 Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4, quartz, Li.sub.3PO.sub.4, SiO.sub.2 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 low cristobalite L* 87.8 a* 0.58 b* 4.78 CR 88.6 Example No. 7 8 9 10 11 12 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 65.8 73.2 65.7 66.7 58.0 67.9 Li.sub.2O 11.8 13.6 13.3 13.8 19.6 14.0 CaO 4.0 4.2 4.0 4.0 5.4 3.7 MgO 2.9 3.0 2.9 2.9 3.9 4.5 Na.sub.2O — — — — — — K.sub.2O 3.7 0.9 3.2 3.4 4.2 3.6 Cs.sub.2O — — — — — — Rb.sub.2O — — — — — — ZnO — — — — — — SrO — — — — — Al.sub.2O.sub.3 3.6 1.9 3.2 4.0 3.4 3.2 B.sub.2O.sub.3 3.1 — — — — — Y.sub.2O.sub.3 — — — — — — La.sub.2O.sub.3 — — — — — — Er.sub.2O.sub.3 — — — — — — ZrO.sub.2 — — — — — — CeO.sub.2 — — — — — — P.sub.2O.sub.5 5.1 3.2 7.7 5.2 5.5 3.1 V.sub.2O.sub.5 — — — — — — Nb.sub.2O.sub.5 — — — — — — WO.sub.3 — — — — — — F — — — — — — GeO.sub.2 — — — — — — T.sub.g/° C. 459.9 460.3 470.3 463.4 453 T.sub.s/° C., t.sub.s/min 1500, 150 1500, 60 1500, 120 1400, 240 1500, 120 1500, 120 T.sub.Sinter/° C., t.sub.Sinter/min 800, 5  800, 5 840, 5  820, 5  900, 5  800, 5  T.sub.Press/° C., t.sub.Press/° C. Main crystal phase Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2SiO.sub.3 Li.sub.2Si.sub.2O.sub.5 Further crystal CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, phases Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, low quartz, Li.sub.3PO.sub.4, Li.sub.2Si.sub.2O.sub.5, Li.sub.2SiO.sub.3, quartz quartz, low Li.sub.3PO.sub.4 MgSiO.sub.3 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 cristobalite L* 85.5 85.97 92.07 89.53 85.5 a* 0.71 0.38 −0.24 0.71 0.37 b* 6.9 4.95 4.09 5.59 5.36 CR 84.72 89.69 69.95 93.81 84.97 Example No. 13 14 15 16 17 18 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 65.6 64.3 67.6 54.7 65.5 62.8 Li.sub.2O 13.8 13.3 14.0 11.2 13.9 13.0 CaO 4.9 4.9 4.1 5.3 4.7 4.5 MgO 3.5 3.5 3.0 3.8 3.4 3.2 Na.sub.2O — — — — — — K.sub.2O 3.1 2.5 3.7 3.5 3.4 0.7 Cs.sub.2O — — — — — 7.5 Rb.sub.2O — — — — — — ZnO — — — — — — SrO — 4.7 — — — — Al.sub.2O.sub.3 2.6 2.8 3.2 3.3 2.7 3.4 B.sub.2O.sub.3 — — — — — — Y.sub.2O.sub.3 — — — — — — La.sub.2O.sub.3 — — — — — — Er.sub.2O.sub.3 — — 0.4 — — — ZrO.sub.2 — — — — — — CeO.sub.2 — — 0.8 — — — P.sub.2O.sub.5 4.0 4.0 3.1 4.8 4.0 4.9 V.sub.2O.sub.5 — — 0.1 — — — Nb.sub.2O.sub.5 — — — — 2.4 — WO.sub.3 2.5 — — — — — F — — — — — — GeO.sub.2 — — — 13.4 — — T.sub.g/° C. 460.7 453.9 452.2 462.2 465.2 T.sub.s/° C., t.sub.s/min 1500, 120 1500, 120 1500, 120 1500, 120 1500, 120 1500, 120 T.sub.Sinter/° C., t.sub.Sinter/min 800, 5P11 800, 5  850, 10 730, 5  800, 5  810, 5  T.sub.Press/° C., t.sub.Press/° C. Main crystal phase Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5/ Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2SiO.sub.3 Further crystal CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, phases Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3, Li.sub.2SiO.sub.3 Li.sub.3SiO.sub.4 Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4, Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Cs.sub.0.809AlSi.sub.5O.sub.12 L* 83.09 86.84 78.76 81.47 80.42 a* −0.35 0.23 0.61 0.78 0.57 b* 0.96 4.39 6.56 9.77 3.59 CR 99.96 96.22 84.81 88.96 99.82 Example No. 19 20 21 22 Composition wt.-% wt.-% wt.-% wt.-% SiO.sub.2 65.7 67.9 64.7 67.0 Li.sub.2O 13.7 14.0 13.2 13.9 CaO 5.1 3.1 4.5 6.3 MgO 3.6 2.2 3.3 3.0 Na.sub.2O — — 1.8 — K.sub.2O 3.1 3.5 0.7 3.6 Cs.sub.2O — — — — Rb.sub.2O — — — — ZnO — — — — SrO — — — — Al.sub.2O.sub.3 3.4 4.0 2.9 3.2 B.sub.2O.sub.3 — — — — Y.sub.2O.sub.3 — — 4.1 La.sub.2O.sub.3 1.2 — — — Er.sub.2O.sub.3 — — — — ZrO.sub.2 — — — — CeO.sub.2 — — — — P.sub.2O.sub.5 4.0 5.3 4.8 3.0 V.sub.2O.sub.5 — — — Nb.sub.2O.sub.5 — — — WO.sub.3 — — — F 0.2 — — GeO.sub.2 — — — T.sub.g/° C. 455.1 469.4 458.1 457 T.sub.s/° C., t.sub.s/min 1500, 120 1400, 240 1500, 120 1400, 120 T.sub.Sinter/° C., t.sub.Sinter/min 800, 5  860, 10 800, 5  800, 5  T.sub.Press/° C., t.sub.Press/° C. Main crystal phase Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Further crystal CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, CaMgSi.sub.2O.sub.6, phases Li.sub.2SiO.sub.3, cristobalite, Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 L* 79.74 94.92 83.46 a* 0.7 −0.3 0.36 b* 5.48 1.5 4 CR 94.56 85.55 94.74

Example 23—Influence of Comminution

[0083] A glass frit with the composition according to Example 10 was ground with a ball mill in the same way as specified for Example 20 to an average particle size of 20 μm, relative to the number of particles. The ground glass powder was then pressed uniaxially and crystallized and sintered in a Programat-type furnace (Ivoclar Vivadent AG) at a temperature of 870° C. for a period of 5 min. A colour measurement (Minolta apparatus) and an X-ray diffraction analysis to determine the crystal phases were then carried out on the test piece prepared in this way. Li.sub.2Si.sub.2O.sub.5 formed the main crystal phase of the glass ceramic. Diopside and Li.sub.3PO.sub.4 were the secondary crystal phases. The diopside content was greater than in Example 10. The increased proportion of diopside leads to a higher degree of opacity which could be read from a CR value of 90.00 instead of 69.95.

Example 24—Hot Pressing

[0084] A glass with the composition according to Example 1 was melted in a platinum crucible at a temperature of 1500° C. and then poured into water. The glass frit prepared in this way was ground with a KM100 vibratory mill from Retsch GmbH, Haan, Germany, to an average particle size of <90 μm, relative to the number of particles. A powder green compact was prepared by uniaxial pressing from the glass powder obtained. The powder green compact was crystallized and densely sintered at a temperature of 800° C. and with a holding time of 5 min in a Programat-type furnace. The crystallized and densely sintered blank was then pressed by means of hot pressing with a holding time of 25 min at a temperature of 910° C. An X-ray structural analysis was carried out on the pressed test pieces and the coefficient of thermal expansion as well as the biaxial strength of the pressed material was determined according to ISO 6872. The biaxial strength was 230 MPa.

Machinability

[0085] To test the machinability, glass powders according to Examples 3, 7, 10, 12, 16, 18 and 23 were pressed uniaxially to form blocks and densely sintered in a Programat-type furnace. Corresponding holders were then adhesively bonded to the glass ceramic blocks prepared in this way and they were processed with a CAD/CAM grinding unit (Sirona InLab). To test the processability, biaxial test pieces were ground out of the blocks.

FIGS. 1 and 2—Microstructure Images

[0086] FIG. 1 shows the microstructure of the glass ceramic according to Example 10. Characteristic is the very fine lithium disilicate microstructure with few interjacent diopside crystals. FIG. 2 shows the microstructure of the glass ceramic obtained according to Example 23 and the increased formation of diopside vis-à-vis Example 10 is clearly recognizable.