Lithium silicate materials

• US 20050098064A1
• Filed: 08/06/2004
• Published: 05/12/2005
• Est. Priority Date: 08/07/2003
• Status: Active Grant

• Current Assignee: Ivoclar Vivadent AG
• Original Assignee: Ivoclar Vivadent AG
• Inventors: Schweiger, Marcel, Holand, Wolfram, Burke, Harald, Rheinberger, Volker M.
• Granted Patent: US 7,316,740 B2
• Time in Patent Office: Days
• US Class Current: 106/35
• CPC Class Codes: A61K 6/78 Pigments
• CPC Class Codes: A61K 6/807 comprising magnesium oxide
• CPC Class Codes: A61K 6/818 comprising zirconium oxide
• CPC Class Codes: A61K 6/833 Glass-ceramic composites
• CPC Class Codes: C03C 10/0027 containing SiO2, Al2O3, Li2O as main constituents
• CPC Class Codes: C03C 10/0036 containing SiO2, Al2O3 and a divalent metal oxide as main constituents
• CPC Class Codes: C03C 3/097 containing phosphorus, niobium or tantalum
• CPC Class Codes: C03C 4/0021 for dental use

Abstract

Lithium silicate materials are described which can be easily processed by machining to dental products without undue wear of the tools and which subsequently can be converted into lithium silicate products showing high strength.

Claims

1. A lithium silicate glass ceramic material which comprises the following components:

2. A lithium silicate material according to claim 1 which is formed in a process which includes a step wherein lithium metasilicate as main crystalline phase is produced.

3. A lithium silicate material according to claim 1 or 2 which further comprises the following additional components, independently from each other,

4. A lithium silicate material according to any one of claims 1 to 3 which comprises the following components, independently of one another,

5. A lithium silicate material according to any one of the claims 1 to 4 which comprises 67.0 to 70.0 wt.—

% of SiO₂.

6. A lithium silicate material according to any one of claims 1 to 5, wherein the lithium metasilicate forms 20 to 50 vol.—

% of the lithium silicate material.

7. A lithium silicate material according to claim 6, wherein the lithium metasilicate forms 30 to 40 vol.—

% of the lithium silicate material.

8. A lithium silicate material according to any one of claims 1 to 7, which, instead of P₂O₅, comprises other nucleation agents.

9. A lithium silicate material according to any one of claims 1 to 8, wherein the lithium metasilicate crystals are of lamellar or platelet form.

10. A lithium silicate material according to any one of claims 1 to 9 in the form of a blank.

11. A lithium silicate material according to any one of claims 1 to 10 in the form of a dental restoration.

12. A lithium silicate material according to claim 11, wherein the dental restoration is an inlay, an onlay, a bridge, an abutment, a facing, a veneer, a facet, a crown, a partial crown, a framework or a coping.

13. A lithium disilicate material which is formed in a process which includes a step wherein a phase comprising primarily crystalline lithium metasilicate is produced, the lithium metasilicate being subsequently converted to lithium disilicate.

14. A dental product made from lithium disilicate, said lithium disilicate being formed in a process which includes a step wherein a phase comprising primarily crystalline lithium metasilicate is produced, the lithium metasilicate being subsequently converted to lithium disilicate.

15. A process for the preparation of a lithium silicate blank, which comprises

(a) producing a melt of a starting glass containing the initial components SiO₂, Li₂O, K₂O, Al₂O₃ and P₂O₅ as the main components

(b) pouring the melt of the starting glass into a mould to form a starting glass blank and cooling the glass blank to room temperature,

(c) subjecting the starting glass blank to a first heat treatment at a first temperature to give a glass product which contains nuclei suitable for forming lithium metasilicate crystals,

(d) subjecting the glass product of step (c) to a second heat treatment at a second temperature which is higher than the first temperature to obtain the lithium silicate blank with lithium metasilicate crystals as the main crystalline phase.

16. A process according to claim 15, wherein the starting glass of step (a) further comprises ZnO, Na₂O, Me^IIO, ZrO₂, and coloring and fluorescent metal oxides, with Me^IIO being one or more members selected from the group consisting of CaO, BaO, SrO and MgO.

17. A process according to claims 15 or 16, wherein the starting glass of step (a) comprises the following initial components, independently of one another, in the following amounts

18. A process according to claim 15, wherein step (c) is replaced by modifying step (b) such that during the cooling process a temperature of about 450 to 550°

C. is held for a period of about 5 minutes to 50 minutes to produce the glass product which contains nuclei suitable for formation of the lithium metasilicate crystals.

19. A process according to any one of claims 15 to 17, wherein in step (c) the first heat treatment comprises heating the starting glass blank to a temperature of about 450 to 550°

C. for a period of about 5 minutes to 1 hour.

20. A process according to any one of claims 15 to 19 wherein the second heat treatment of step (d) comprises heating the glass product which contains nuclei suitable for formation of lithium silicate crystals to a second temperature of about 600 to 700°

C for a period of about 10 to 30 minutes.

21. A process according to any one of claims 15 to 20, wherein the lithium silicate blank has a biaxial strength of at least 90 MPa and a fracture toughness of at least 0.8 MPam^0.5.

22. A process according to any one of claims 15 to 21, wherein the starting glass blank of step (b), the glass product containing nuclei suitable for forming lithium metasilicate of step (c), or the lithium silicate blank with lithium metasilicate as the main crystalline phase of step (d) is shaped to a desired geometry by machining or by hot pressing to form a shaped lithium silicate product.

25. A process according to claim 22 wherein the machining is performed by grinding or milling.

26. A process according to claim 25, wherein the machining is controlled by a computer.

27. A process according to any one claims 22 to 26 further comprising subjecting the shaped lithium silicate product to a third heat treatment at a third temperature of about 700 to 950°

C. for a period of about 5 to 30 minutes.

28. A process according to claim 27 wherein the lithium silicate product subjected to the third heat treatment comprises lithium metasilicate as the main crystalline phase, and wherein the third heat treatment converts the lithium metasilicate crystals to lithium disilicate crystals as the main crystalline phase.

29. A process according to claim 27 wherein the lithium silicate product subjected to the third heat treatment comprises the glass product containing nuclei suitable for forming lithium metasilicate crystals, and wherein lithium disilicate crystals are crystallized directly from the nuclei suitable for forming lithium metasilicate crystals.

30. A process according to any one of claims 27 to 29, wherein the shrinkage that occurs during the third heat treatment is less than 0.5%, preferably less than 0.3%, by volume.

31. A process according to claim 22 which comprises shaping of a lithium silicate material to the desired geometry by hot pressing to produce the dental restoration.

32. A process for manufacturing a dental restoration according to claim 31 wherein the hot pressing comprises

subjecting the lithium silicate material to a heat treatment at a temperature of about 500 to 1200°

C. to convert the lithium silicate material into a viscous state and pressing the viscous lithium silicate material under a pressure of about 1 to 4 MPa into a mould or dye to obtain the dental restoration with a desired geometry.

33. A process according to claim 32 wherein the lithium silicate material subjected to the heat treatment and pressing comprises lithium metasilicate crystals which are converted into lithium disilicate crystals during the heat treatment and pressing.

34. A process according to any one of the claims 27 to 30 or 32 to 34 which comprises an increasing of strength and fracture toughness of the lithium silicate material.

38. A process according to any one onf claims 27 to 37 wherein the third heat treatment occurs during a firing of the layering materials or the hot pressing of the coating material onto the unfinished the dental restoration.

40. A blank made from a lithium silicate material prepared according to the process of any one of claims 15 to 21, wherein the blank has a holder to fix it in a machine.

41. A lithium silicate blank according to claim 40, wherein the holder is jointed and connected with the holder.

42. A lithium silicate blank according to claim 40 or 41, wherein the holder is from a different material from the blank.

43. A lithium silicate blank according to any one of claims 40 to 42, wherein the holder is made from an alloy, from a metal, from a glass ceramic or from a ceramic.

44. A lithium silicate blank according to claim 40 or 41, wherein the holder is made from the same material as the blank and is integral with the blank.

45. A lithium silicate blank according to any one of the claims 40 to 44, wherein the blank is labelled with information.

46. A lithium silicate blank according to claim 45, wherein the information on the blank comprises the material, the size and the type of the shape, which is to be machined from the blank.

47. A method for manufacturing a lithium silicate restoration comprising preparing a lithium silicate blank according to the process of any one of claims 15 to 21, and thereafter coating a dental restoration with the lithium silicate blank.

48. A method for manufacturing a dental restoration according to claim 47 wherein a dental framework is coated by hot pressing the lithium silicate blank onto the dental framework.

49. A method formanufacturing a dental restoration according to claim 48, wherein the dental framework is a crown, a partial crown, a bridge, a coping, a veneer, a facing or an abutment.

50. A method for manufacturing a dental restoration according to claim 49, wherein the dental framework is made from a metal, an alloy, a ceramic or a glass ceramic.

51. A method for manufacturing a dental restoration according to claim 50, wherein the ceramic comprises zirconium oxide, aluminium oxide, a zirconium mix oxide, an aluminium mix oxide, or a combination thereof.

52. A method for manufacturing a dental restoration according to any one of the claims 48 to 51 wherein the lithium silicate blank which is coated onto the framework comprises lithium metasilicate crystals which are converted to lithium disilicate crystals, or the lithium silicate blank comprises nuclei suitable for forming lithium metasilicate crystals which crystallize as lithium disilicate crystals during the hot pressing of the lithium silicate blank onto the dental framework.

23. A process according to claim 23, wherein the shaped lithium silicate blank is a dental restoration.

24. A process according to claim 23 wherein the dental restoration is an inlay, an onlay, a bridge, an abutment, a facing, a veneer, a facet, a crown, a partial crown, a framework or a coping.

35. A process for the manufacture of a dental restoration according to any one of the claims 23 to 34 wherein the dental restoration has a biaxial strength of at least 250 MPa and a fracture toughness of at least 1.5 MPam^0.5.

36. A process for the manufacture of a dental restoration according to any one of claims 23 to 35 further comprising finishing the dental restoration to obtain a natural appearance.

37. A process according to claim 36, wherein the finishing step comprises applying a coating to the dental restoration by layering with powdered materials or by hot pressing a coating material onto the unfinished dental restoration.

39. A lithium silicate glass which comprises the following components