Lithium disilicate-apatite glass ceramic with transition metal oxide

Abstract

Lithium disilicate-apatite glass ceramics comprising transition metal oxide are described which are characterized by a high chemical stability, and the translucence of which can be adjusted as desired, and which can therefore be used in particular as restoration material in dentistry.

Claims

1. Lithium disilicate-apatite glass ceramic, which comprises lithium disilicate as main crystal phase and apatite as further crystal phase, and which comprises divalent oxide selected from the group of CaO, SrO and mixtures thereof and transition metal oxide selected from the group of oxides of transition metals with an atomic number from 39 to 79 and mixtures thereof, wherein the molar ratio of divalent oxide to transition metal oxide is in the range of from 1.0 to 20.0.

2. Glass ceramic according to claim 1, which comprises 52.0 to 75.0 wt.-% SiO.sub.2.

3. Glass ceramic according to claim 1, which comprises 10.0 to 20.0 wt.-% Li.sub.2O.

4. Glass ceramic according to claim 1, which comprises 4.0 to 8.0 wt.-% P.sub.2O.sub.5.

5. Glass ceramic according to claim 1, which comprises 2.0 to 9.0 wt.-% divalent oxide.

6. Glass ceramic according to claim 1, which comprises 2.5 to 8.5 wt.-% CaO.

7. Glass ceramic according to claim 1, which comprises 1.0 to 6.5 wt.-% SrO.

8. Glass ceramic according to claim 1, which comprises 0.1 to 1.5 wt.-% F.

9. Glass ceramic according to claim 1, which comprises 0 to 4.0 wt.-% Al.sub.2O.sub.3.

10. Glass ceramic according to claim 1, which comprises 0.5 to 8.5 wt.-% transition metal oxide.

11. Glass ceramic according to claim 1, in which the transition metal oxide is selected from the group of La.sub.2O.sub.3, Y.sub.2O.sub.3, Er.sub.2O.sub.3, ZrO.sub.2, CeO.sub.2, Tb.sub.4O.sub.7, V.sub.2O.sub.5, Ta.sub.2O.sub.5, Nb.sub.2O.sub.5 and mixtures thereof.

12. Glass ceramic according to claim 1, in which the transition metal oxide is present according to the formula Me.sub.2O.sub.3 in an amount of from 0 to 5.0 wt.-%, according to the formula MeO.sub.2 in an amount of from 0 to 6.5 wt.-%, according to the formula Me.sub.4O.sub.7 in an amount of from 0 to 1.0 wt.-% and/or according to the formula Me.sub.2O.sub.5 in an amount of from 0 to 5.0 wt.-%.

13. Glass ceramic according to claim 1, which comprises monovalent oxide selected from the group of Na.sub.2O, K.sub.2O, Rb.sub.2O, Cs.sub.2O and mixtures thereof in an amount of from 0 to 12.0 wt.-%.

14. Glass ceramic according to claim 1, which comprises fluoroapatite as apatite.

15. Glass ceramic according to claim 1, in which the apatite crystal phase makes up 0.5 to 10 wt.-% of the glass ceramic and/or the apatite crystals have an average size of from 5 to 500 nm.

16. Lithium metasilicate-apatite glass ceramic, which comprises lithium metasilicate as main crystal phase and apatite as further crystal phase, and which comprises divalent oxide selected from the group of CaO, SrO and mixtures thereof and transition metal oxide selected from the group of oxides of transition metals with an atomic number from 39 to 79 and mixtures thereof, wherein the molar ratio of divalent oxide to transition metal oxide is in the range of from 1.0 to 20.0.

17. Glass ceramic according to claim 1, wherein the glass ceramicis present in the form of a powder, a granulate, a blank or a dental restoration.

18. Process for the preparation of the glass ceramic according to claim 1, wherein a starting glass or a lithium metasilicate glass ceramic is subjected to at least one heat treatment in the range of from 450 to 1000 C.

19. Process according to claim 18, wherein (a) the starting glass is subjected to a heat treatment at a temperature of from 450 to 600 C. in order to form starting glass with nuclei, and (b) the starting glass with nuclei is subjected to a heat treatment at a temperature of from 700 to 1000 C. in order to form the lithium disilicate-apatite glass ceramic.

20. Process of using the lithium disilicate-apatite glass ceramic according to claim 1 as dental material for coating dental restorations or for the preparation of dental restorations.

21. Process of using the lithium disilicate-apatite glass ceramic according to claim 20, wherein the lithium disilicate-apatite glass ceramic is given, by pressing or machining, a shape of the dental restoration, as a bridge, inlay, onlay, veneer, abutment, partial crown, crown or facet.

22. Lithium disilicate-apatite glass ceramic, according to claim 1, wherein the molar ratio of divalent oxide to transition metal oxide is in the range of from 1.0 to 17.0.

23. Lithium disilicate-apatite glass ceramic, according to claim 1, wherein the molar ratio of divalent oxide to transition metal oxide is in the range of from 1.5 to 16.5.

24. Glass ceramic according to claim 2, which comprises 54.0 to 73.0 wt.-% SiO.sub.2.

25. Glass ceramic according to claim 3, which comprises 2.0 to 20.0 wt.-% Li.sub.2O.

26. Glass ceramic according to claim 5, which comprises 3.0 to 8.0 wt.-% divalent oxide.

27. Glass ceramic according to claim 6, which comprises 3.0 to 8.0 wt.-% CaO.

28. Glass ceramic according to claim 7, which comprises 1.0 to 6.0 wt.-% SrO.

29. Glass ceramic according claim 8, which comprises 0.3 to 1.0 wt.-% F.

30. Glass ceramic according to claim 9, which comprises 1.0 to 4.0 Al.sub.2O.sub.3.

31. Glass ceramic according to claim 9, which comprises 1.5 to 4.0 wt.-% Al.sub.2O.sub.3.

32. Glass ceramic according to claim 10, which comprises 1.0 to 8.0 wt.-% transition metal oxide.

33. Glass ceramic according to claim 10, which comprises 2.0 to 7.5 wt.-% transition metal oxide.

34. Glass ceramic according to claim 12, in which the transition metal oxide is present according to the formula Me.sub.2O.sub.3 in an amount of from 2.5 to 4.0 wt.-%, according to the formula MeO.sub.2 in an amount of from 1.0 to 6.0 wt.-%, according to the formula Me.sub.4O.sub.7 in an amount of from 0.4 to 1.0 wt.-% and/or according to the formula Me.sub.2O.sub.5 in an amount of from 0.1 to 4.0 wt.-%.

35. Glass ceramic according to claim 13, which comprises monovalent oxide selected from the group of Na.sub.2O, K.sub.2O, Rb.sub.2O, Cs.sub.2O and mixtures thereof in an amount of from 0 to 12.0 wt.-%.

36. Glass ceramic according to claim 13, which comprises monovalent oxide selected from the group of Na.sub.2O, K.sub.2O, Rb.sub.2O, Cs.sub.2O and mixtures thereof in an amount of from 3.0 to 11.5 wt.-%.

37. Glass ceramic according to claim 15, in which the apatite crystal phase makes up 1 to 10 and preferably 2 to 8 wt.-% of the glass ceramic and/or the apatite crystals have an average size of from 10 to 300.

38. Glass ceramic according to claim 15, in which the apatite crystal phase makes up 2 to 8 wt.-% of the glass ceramic and/or the apatite crystals have an average size of 20 to 200 nm.

39. Lithium metasilicate glass ceramic according to claim 16, wherein the lithium metasilicate glass ceramic is present in the form of a powder, a granulate, a blank or a dental restoration.

40. Process of using the lithium metasilicate glass ceramic according to claim 16 as dental material for coating dental restorations or for the preparation of dental restorations.

41. Process of using the lithium metasilicate glass ceramic according to claim 40, wherein the lithium metasilicate glass ceramic is given, by pressing or machining, a shape of the dental restoration as a bridge, inlay, onlay, veneer, abutment, partial crown, crown or facet.

Description

EXAMPLES

Examples 1 to 20Composition and Crystal Phases

(1) A total of 20 glasses and glass ceramics according to the invention with the composition given in the table below were prepared by melting corresponding starting glasses followed by heat treatment for controlled nucleation and crystallization.

(2) The T.sub.g values of the glasses as well as the heat treatments used for controlled nucleation and controlled crystallization are also given in the table. The following meanings apply T.sub.N and t.sub.N temperature and time used for nucleation T.sub.K1 and t.sub.K1 temperature and time used for a 1st crystallization T.sub.K2 and t.sub.K2 temperature and time used for a 2nd crystallization

(3) For this, the starting glasses in batches of 100 to 200 g were first melted from customary raw materials at 1400 to 1500 C., wherein the melting was very easily possible without formation of bubbles or streaks. By pouring the starting glasses into water, glass frits were produced which were then melted a second time at 1450 to 1550 C. for 1 to 3 h for homogenization.

(4) A heat treatment of the starting glasses at a temperature of from 460 to 540 C. led to the formation of lithium silicate glasses with nuclei.

(5) As a result of at least one further heat treatment, these nuclei-containing glasses crystallized to form glass ceramics with lithium metasilicate as main crystal phase or glass ceramics with lithium disilicate as main crystal phase and apatite as further crystal phase, as was established by X-ray diffraction tests. The apatite was present as Ca-fluoroapatite, Sr-fluoroapatite or Ca/Sr-fluoroapatite.

(6) In Examples 1 to 4, 7, 9, 10 and 15, a first further heat treatment T.sub.K1 of the nuclei-containing starting glasses led to glass ceramics with lithium metasilicate as main crystal phase and the obtained lithium metasilicate glass ceramics were converted into glass ceramics with lithium disilicate as main crystal phase and apatite as further crystal phase by a second further heat treatment T.sub.K2.

(7) In Examples 13, 14, 16, 17, 19 and 20, the nuclei-containing starting glasses were converted into glass ceramics with lithium disilicate as main crystal phase and apatite as further crystal phase by only one further heat treatment, and in the case of Example 18 into a glass ceramic with lithium metasilicate as main crystal phase and apatite as further crystal phase.

(8) In Examples 8, 11 and 12, glass ceramics with lithium metasilicate as main crystal phase were also present after the second further heat treatment.

(9) Finally, Examples 5 and 6 show the production of glass ceramics with lithium disilicate as main crystal phase even after the first further heat treatment and the further crystallization thereof by a second further heat treatment.

(10) The examples thus collectively show how different glass ceramics according to the invention can be produced by altering the composition of the starting glasses and the heat treatment thereof.

(11) The obtained lithium disilicate-apatite glass ceramics according to the invention displayed an excellent chemical stability according to ISO test 6872 (2008). The mass loss during storage in aqueous acetic acid was less than 100 g/cm.sup.2, in particular less than 50 g/cm.sup.2.

(12) By contrast, conventional bioactive glass ceramics show a very high mass loss and thus a very low chemical stability. They are not suitable for use as restorative dental material which repeatedly comes into contact with fluids of the most varied composition in the oral cavity.

(13) The produced lithium disilicate-apatite glass ceramics also had a very high biaxial strength .sub.B of more than 390 and in particular of up to about 640 MPa. This strength was determined according to dental standard ISO 6872 (2008) on test pieces. The test pieces were produced by machining of the lithium metasilicate glass ceramic obtained after the 1st crystallization (T.sub.K1) and subsequent 2nd crystallization (T.sub.K2) to form the respective lithium disilicate-apatite glass ceramic. A CEREC-InLab machine (Sirona, Bensheim) was used for the machining of the lithium metasilicate glass ceramic.

(14) The lithium disilicate-apatite glass ceramics produced and the lithium metasilicate glass ceramics produced as precursor were able to be very satisfactorily brought into the form of various dental restorations by machining in a CAD/CAM process or by hot pressing, which restorations were also provided with a veneer if required. The lithium metasilicate glass ceramics proved particularly suitable for shaping by machining due to their mechanical properties.

(15) The glass ceramics were also able to be applied by hot pressing as coatings onto in particular dental restorations, e.g. in order to veneer the latter as desired.

(16) Finally, the glass ceramics had a linear coefficient of thermal expansion (CTE) in the broad range of from 8.6 to 11.110.sup.6K.sup.1 (measured in the range of from 100 to 500 C.). Specifically, materials with a CTE of less than 1010.sup.6K.sup.1 are particularly well-suited for veneering e.g. ZrO.sub.2 ceramics.

(17) In the following table, TMO in the indication of the molar ratios stands for transition metal oxides.

(18) RT-XRD stands for X-ray diffraction tests at room temperature.

(19) CTE stands for linear coefficient of thermal expansion.

(20) TABLE-US-00002 Example 1 2 3 4 5 6 SiO.sub.2 65.3 64.1 65.3 63.3 62.1 72.7 GeO.sub.2 2.9 Li.sub.2O 13.5 15.0 13.5 13.3 13.5 12.1 P.sub.2O.sub.5 5.7 4.5 5.7 5.2 4.3 4.3 Al.sub.2O.sub.3 3.2 3.2 3.2 2.4 3.6 1.9 K.sub.2O 3.7 3.7 3.7 3.7 3.0 Rb.sub.2O 7.7 Cs.sub.2O CaO 4.1 5.0 4.1 4.1 4.0 3.0 SrO 1.4 F 0.5 0.5 0.5 0.4 0.5 0.5 ZrO.sub.2 CeO.sub.2 La.sub.2O.sub.3 4.0 4.0 2.5 Y.sub.2O.sub.3 3.6 V.sub.2O.sub.5 Ta.sub.2O.sub.5 4.0 Nb.sub.2O.sub.5 4.0 Tb.sub.4O.sub.7 Er.sub.2O.sub.3 100.0 100.0 100.0 100.0 100.0 100.0 molar ratio 4.7 10.0 6.0 5.4 7.0 7.5 (CaO + SrO) to TMO T.sub.g/ C. 467 453 458 469 453 456 T.sub.N/ C. 520 480 500 490 540 460 t.sub.N/min. 20 40 10 40 10 30 T.sub.K1/ C. 670 650 640 620 680 600 t.sub.K1/min. 10 20 40 30 40 30 RT-XRD after T.sub.K1 Main crystal phase Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Further crystal Li.sub.2Si.sub.2O.sub.5, Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4, Li.sub.2SiO.sub.3 phases Li.sub.3PO.sub.4 Ca.sub.5(PO.sub.4).sub.3F T.sub.K2/ C. 800 800 760 800 820 810 t.sub.K2/min. 10 15 60 30 10 20 RT-XRD after T.sub.K2 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 Further crystal Li.sub.3PO.sub.4, Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, phases Ca.sub.5(PO.sub.4).sub.3F Li.sub.3PO.sub.4, Ca.sub.5(PO.sub.4).sub.3F Ca.sub.5(PO.sub.4).sub.3F Ca.sub.9.37Sr.sub.0.63(PO.sub.4).sub.3F Ca.sub.5(PO.sub.4).sub.3F, Ca.sub.5(PO.sub.4).sub.3F SiO.sub.2 CTE.sub.100-500 C./ 10.3 11.2 10.5 10.5 11.1 10.sup.6 .Math. K.sup.1 .sub.B/MPa 442 637 385 562 548 Example 7 8 9 10 11 12 SiO.sub.2 65.3 54.9 61.5 65.3 61.8 59.9 GeO.sub.2 Li.sub.2O 13.5 18.2 12.4 13.5 17.1 18.7 P.sub.2O.sub.5 5.7 4.8 4.3 5.7 4.4 4.4 Al.sub.2O.sub.3 3.2 3.5 3.2 3.2 3.5 3.5 K.sub.2O 3.7 4.6 3.7 3.9 3.9 Rb.sub.2O Cs.sub.2O 11.1 CaO 4.1 4.5 4.1 4.0 4.0 SrO 6.0 F 0.5 0.8 0.5 0.5 0.5 0.5 ZrO.sub.2 CeO.sub.2 1.8 1.7 1.9 La.sub.2O.sub.3 Y.sub.2O.sub.3 4.8 4.0 2.5 V.sub.2O.sub.5 0.1 0.1 Ta.sub.2O.sub.5 4.0 2.5 Nb.sub.2O.sub.5 2.5 Tb.sub.4O.sub.7 0.5 0.4 0.4 Er.sub.2O.sub.3 0.1 0.1 0.2 100.0 100.0 100.0 100.0 100.0 100.0 molar ratio 8.4 1.8 16.3 4.7 3.5 3.3 (CaO + SrO) to TMO T.sub.g/ C. 465 441 466 461 447 443 T.sub.N/ C. 490 470 500 470 500 520 t.sub.N/min. 60 60 10 120 10 10 T.sub.K1/ C. 600 700 630 580 650 620 t.sub.K1/min. 30 20 30 60 20 30 RT-XRD after T.sub.K1 Main crystal phase Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Further crystal Li.sub.2Si.sub.2O.sub.5, Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 phases Li.sub.3PO.sub.4 T.sub.K2/ C. 770 840 840 790 800 800 t.sub.K2/min. 30 10 10 20 30 20 RT-XRD after T.sub.K2 Main crystal phase 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 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Further crystal Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, Cs.sub.0.809(AlSi.sub.5O.sub.12), Li.sub.3PO.sub.4, Li.sub.2Si.sub.2O.sub.5, Li.sub.3PO.sub.4, phases Ca.sub.5(PO.sub.4).sub.3F Sr.sub.5(PO.sub.4).sub.3F Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4, Ca.sub.5(PO.sub.4).sub.3F Li.sub.3PO.sub.4, Ca.sub.5(PO.sub.4).sub.3F Ca.sub.5(PO.sub.4).sub.3F Ca.sub.5(PO.sub.4).sub.3F CTE.sub.100-500 C./ 10.2 10.4 10.sup.6 .Math. K.sup.1 .sub.B/MPa 419 392 Example 13 14 15 16 17 18 SiO.sub.2 68.5 67.3 65.3 64.0 64.8 59.2 GeO.sub.2 Li.sub.2O 14.5 14.0 13.5 13.1 13.5 19.6 P.sub.2O.sub.5 4.4 5.9 5.7 5.6 5.7 5.7 Al.sub.2O.sub.3 3.5 3.3 3.2 3.2 3.2 3.2 K.sub.2O 3.8 3.7 3.6 3.7 3.7 Rb.sub.2O Cs.sub.2O CaO 4.0 4.2 4.1 8.0 4.1 4.1 SrO F 0.5 0.5 0.5 0.5 1.0 0.5 ZrO.sub.2 1.0 4.0 2.0 4.0 4.0 CeO.sub.2 1.6 La.sub.2O.sub.3 Y.sub.2O.sub.3 2.5 V.sub.2O.sub.5 Ta.sub.2O.sub.5 0.5 Nb.sub.2O.sub.5 Tb.sub.4O.sub.7 Er.sub.2O.sub.3 100.0 100.0 100.0 100.0 100.0 100.0 molar ratio 3.5 8.4 2.3 8.8 2.3 2.3 (CaO + SrO) to TMO T.sub.g/ C. 443 457 471 463 464 442 T.sub.N/ C. 480 480 490 490 480 460 t.sub.N/min. 10 10 10 10 10 10 T.sub.K1/ C. 890 650 t.sub.K1/min. 10 40 RT-XRD after T.sub.K1 Main crystal Li.sub.2Si.sub.2O.sub.5 Li.sub.2SiO.sub.3 phase Further crystal Li.sub.2OAl.sub.2O.sub.37.5SiO.sub.2, Li.sub.3PO.sub.4 phases Li.sub.3PO.sub.4, Ca.sub.5(PO.sub.4).sub.3F, SiO.sub.2 T.sub.K2/ C. 790 780 810 780 820 t.sub.K2/min. 60 60 60 60 60 RT-XRD after T.sub.K2 Main crystal 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 phase Further crystal Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4, Li.sub.2Si.sub.2O.sub.5, phases Ca.sub.5(PO.sub.4).sub.3F Ca.sub.5(PO.sub.4).sub.3F Li.sub.3PO.sub.4, Ca.sub.5(PO.sub.4).sub.3F Li.sub.3PO.sub.4, Ca.sub.5(PO.sub.4).sub.3F Ca.sub.5(PO.sub.4).sub.3F CTE.sub.100-500 C./ 8.6 10.sup.6 .Math. K.sup.1 .sub.B/Mpa Example 19 20 SiO.sub.2 63.4 66.2 GeO.sub.2 Li.sub.2O 13.4 13.6 P.sub.2O.sub.5 8.0 5.8 Al.sub.2O.sub.3 3.1 K.sub.2O 3.6 3.7 Rb.sub.2O Cs.sub.2O CaO 4.0 4.2 SrO F 0.5 0.5 ZrO.sub.2 4.0 6.0 CeO.sub.2 La.sub.2O.sub.3 Y.sub.2O.sub.3 V.sub.2O.sub.5 Ta.sub.2O.sub.5 Nb.sub.2O.sub.5 Tb.sub.4O.sub.7 Er.sub.2O.sub.3 100.0 100.0 molar ratio 2.1 1.6 (CaO + SrO) to TMO T.sub.g/ C. 484 473 T.sub.N/ C. 500 490 t.sub.N/min. 10 10 T.sub.K1/ C. t.sub.K1/min. RT-XRD after T.sub.K1 Main crystal phase Further crystal phases T.sub.K2/ C. 800 830 t.sub.K2/min. 40 60 RT-XRD after T.sub.K2 Main crystal phase Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Further crystal Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, phases Ca.sub.5(PO.sub.4).sub.3F Ca.sub.5(PO.sub.4).sub.3F, KLi.sub.3Zr.sub.2Si.sub.12O.sub.30, SiO.sub.2 CTE.sub.100-500 C./ 10.sup.6 .Math. K.sup.1 .sub.B/MPa