Lithium silicate glass ceramics and lithium silicate glass containing cesium oxide

Abstract

The invention relates to the use of lithium silicate glass ceramics and glasses with caesium oxide content, which are suitable in particular for veneering oxide ceramic restorations and metal restorations.

Claims

1. Process of using a lithium silicate glass ceramic or a lithium silicate glass which comprise the following components TABLE-US-00006 Component wt.-% SiO.sub.2 54.0 to 78.0 Li.sub.2O 11.0 to 19.0 Cs.sub.2O 4.4 to 13.0 Al.sub.2O.sub.3 1.0 to 9.0 P.sub.2O.sub.5 0.5 to 9.0, for coating a substrate selected from oxide ceramics, metals and alloys.

2. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise at least one of the following components in the given amounts TABLE-US-00007 Component wt.-% SiO.sub.2 55.1 to 77.1 Li.sub.2O 11.8 to 17.8 Cs.sub.2O 4.4 to 11.7 Al.sub.2O.sub.3 1.7 to 8.0 P.sub.2O.sub.5 1.3 to 7.5 ZrO.sub.2 0 to 4.5 Transition metal oxide 0 to 7.5, wherein the transition metal oxide is selected from the group consisting of oxides of yttrium, oxides of transition metals with an atomic number from 41 to 79 and mixtures of these oxides.

3. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise up to 70.0 wt.-% SiO.sub.2.

4. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise 5.0 to 10.0 wt.-% Cs.sub.2O.

5. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise 2.0 to 6.0 wt.-% Al.sub.2O.sub.3.

6. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 4.0 wt.-% Na.sub.2O and/or K.sub.2O.

7. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 2.5 wt.-% Rb.sub.2O.

8. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 3.8 wt.-% BaO.

9. Process according to claim 1, in which a lithium silicate glass ceramic is used which comprises lithium metasilicate as main crystal phase.

10. Process according to claim 1, in which a lithium silicate glass ceramic is used which comprises lithium disilicate as main crystal phase.

11. Process of using a lithium silicate glass ceramic which comprises the following components TABLE-US-00008 Component wt.-% SiO.sub.2 54.0 to 78.0 Li.sub.2O 11.0 to 19.0 Cs.sub.2O  4.0 to 13.0 Al.sub.2O.sub.3 1.0 to 9.0 P.sub.2O.sub.5  0.5 to 9.0, for coating a substrate selected from oxide ceramics, metals and alloys, in which the lithium silicate glass ceramic comprises at least one caesium aluminosilicate crystal phase.

12. Process of using a lithium silicate glass ceramic which comprises the following components TABLE-US-00009 Component wt.-% SiO.sub.2 54.0 to 78.0 Li.sub.2O 11.0 to 19.0 Cs.sub.2O  4.0 to 13.0 Al.sub.2O.sub.3 1.0 to 9.0 P.sub.2O.sub.5  0.5 to 9.0, for coating a substrate selected from oxide ceramics, metals and alloys, in which the lithium silicate glass ceramic comprises at least one lithium aluminosilicate crystal phase.

13. Process according to claim 1, in which a lithium silicate glass is used, wherein the lithium silicate glass comprises nuclei which are suitable for forming lithium metasilicate and/or lithium disilicate crystals.

14. Process according to claim 1, in which the substrate is an oxide ceramic.

15. Process of using a lithium silicate glass ceramic which comprises the following components TABLE-US-00010 Component wt.-% SiO.sub.2 54.0 to 78.0 Li.sub.2O 11.0 to 19.0 Cs.sub.2O  4.0 to 13.0 Al.sub.2O.sub.3 1.0 to 9.0 P.sub.2O.sub.5  0.5 to 9.0, for coating a substrate in which the substrate is a metal or an alloy.

16. Process according to claim 1, in which the substrate is a dental restoration.

17. Process for coating a substrate selected from oxide ceramics, metals and alloys, in which a lithium silicate glass ceramic or a lithium silicate glass, as defined in claim 1, is applied to the substrate.

18. Process according to claim 17, in which the lithium silicate glass ceramic or the lithium silicate glass is applied to the substrate by sintering or by pressing-on.

19. Process according to claim 17, in which the lithium silicate glass ceramic or the lithium silicate glass is applied to the substrate by joining.

20. Process according to claim 19, in which the lithium silicate glass ceramic or the lithium silicate glass is shaped to a desired geometry by machining or by hot pressing before joining.

21. Process according to claim 17, in which a coating is obtained which comprises a lithium silicate glass ceramic that comprises lithium metasilicate as main crystal phase.

22. Process according to claim 17, in which a coating is obtained which comprises a lithium silicate glass ceramic that comprises lithium disilicate as main crystal phase.

23. Process according to claim 21, in which the lithium silicate glass ceramic comprises at least one caesium aluminosilicate crystal phase.

24. Composite material which comprises a lithium silicate glass ceramic or a lithium silicate glass, as defined in claim 1, on a substrate selected from oxide ceramics, metals and alloys.

25. Lithium silicate glass ceramic, which is as defined in claim 11 and which comprises at least one caesium aluminosilicate crystal phase.

26. Lithium silicate glass ceramic, which is as defined in claim 1 and which comprises the following components in the given amounts TABLE-US-00011 Component wt.-% SiO.sub.2 54.0 to 78.0, Li.sub.2O 11.0 to 19.0 Cs.sub.2O 4.6 to 13.0 Al.sub.2O.sub.3 1.0 to 9.0 P.sub.2O.sub.5 0.5 to 9.0 Rb.sub.2O 0 to 7.0 BaO 0 to 3.7 ZrO.sub.2 0 to 4.5 Transition metal oxide 0 to 7.5, wherein the transition metal oxide is selected from the group consisting of oxides of yttrium, oxides of transition metals with an atomic number from 41 to 79 and mixtures of these oxides.

27. Lithium silicate glass, which comprises the components of the glass ceramic according to claim 26.

28. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise at least one of the following components in the given amounts TABLE-US-00012 Component wt.-% SiO.sub.2 55.1 to 77.1 Li.sub.2O 11.8 to 17.8 Cs.sub.2O 4.4 to 11.7 Al.sub.2O.sub.3 1.7 to 8.0 P.sub.2O.sub.5 1.3 to 7.5 ZrO.sub.2 0 to 4.0 Transition metal oxide 0 to 7.0, wherein the transition metal oxide is selected from the group consisting of oxides of yttrium, oxides of transition metals with an atomic number from 41 to 79 and mixtures of these oxides.

29. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise 60.0 to 70.0 wt.-% SiO.sub.2.

30. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise 64.0 to 70.0 wt.-% SiO.sub.2.

31. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise 5.1 to 8.0 wt.-% Cs.sub.2O.

32. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise 5.5 to 7.7 wt.-% Cs.sub.2O.

33. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise 6.1 to 7.4 wt.-% Cs.sub.2O.

34. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise 2.5 to 5.0 wt.-% Al.sub.2O.sub.3.

35. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise 3.0 to 4.5 wt.-% Al.sub.2O.sub.3.

36. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 3.5 wt.-% Na.sub.2O and/or K.sub.2O.

37. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 3.0 wt.-% Na.sub.2O and/or K.sub.2O.

38. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 2.5 wt.-% Na.sub.2O and/or K.sub.2O.

39. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 2.0 wt.-% Na.sub.2O and/or K.sub.2O.

40. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 1.5 wt.-% Rb.sub.2O.

41. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 1.0 wt.-% Rb.sub.2O.

42. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 0.5 wt.-% Rb.sub.2O.

43. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass is substantially free of Rb.sub.2O.

44. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 2.5 wt.-% BaO.

45. Method according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 1.5 wt.-% BaO.

46. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass comprise less than 0.5 wt.-% BaO.

47. Process according to claim 1, in which the lithium silicate glass ceramic or the lithium silicate glass is substantially free of BaO.

48. Process according to claim 1, in which a lithium silicate glass ceramic is used which comprises lithium metasilicate as main crystal phase and has a bending strength in the range of about 180 to 300 MPa and/or a fracture toughness, measured as K.sub.IC value, of at least about 2.3 MPa.Math.m.sup.0.5.

49. Process according to claim 1, in which a lithium silicate glass ceramic is used which comprises lithium metasilicate as main crystal phase and has a bending strength in the range of about 180 to 300 MPa and/or a fracture toughness, measured as K.sub.IC value, of at least about 2.6 MPa.Math.m.sup.0.5.

50. Process according to claim 1, in which a lithium silicate glass ceramic is used which comprises lithium disilicate as main crystal phase and has a bending strength in the range of about 400 to 700 MPa and/or a fracture toughness, measured as K.sub.IC value, of at least about 2.3 MPa.Math.m.sup.0.5.

51. Process according to claim 1, in which a lithium silicate glass ceramic is used which comprises lithium disilicate as main crystal phase and has a bending strength in the range of about 400 to 700 MPa and/or a fracture toughness, measured as K.sub.IC value, of at least about 2.6 MPa.Math.m.sup.0.5.

52. Process according to claim 11, in which a lithium silicate glass ceramic is used which comprises at least one caesium aluminosilicate crystal phase, wherein the caesium aluminosilicate has the formula Cs.sub.xAlSi.sub.5O.sub.12, wherein x is 0.75 to 0.85.

53. Process according to claim 11, in which a lithium silicate glass ceramic is used which comprises at least one caesium aluminosilicate crystal phase, wherein the caesium aluminosilicate has the formula Cs.sub.xAlSi.sub.5O.sub.12, wherein x is 0.80 to 0.82.

54. Process according to claim 11, in which a lithium silicate glass ceramic is used which comprises at least one caesium aluminosilicate crystal phase, wherein the caesium aluminosilicate has the formula Cs.sub.xAlSi.sub.5O.sub.12, wherein x is 0.808 to 0.810.

55. Process according to claim 11, in which a lithium silicate glass ceramic is used which comprises at least one caesium aluminosilicate crystal phase, wherein the caesium aluminosilicate has the formula Cs.sub.0.809AlSi.sub.5O.sub.12.

56. Process according to claim 1, in which the substrate is a zirconium oxide ceramic.

57. Process according to claim 15, in which the substrate is non-precious metal alloy.

58. Lithium silicate glass ceramic, which is as defined in claim 1 and which comprises the following components in the given amounts TABLE-US-00013 Component wt.-% SiO.sub.2 55.1 to 77.1 Li.sub.2O 11.8 to 17.8 Cs.sub.2O 4.7 to 11.7 Al.sub.2O.sub.3 1.7 to 8.0 P.sub.2O.sub.5 1.3 to 7.5 Rb.sub.2O 0 to 5.0 BaO 0 to 3.0 ZrO.sub.2 0 to 4.0 Transition metal oxide 0 to 7.0, wherein the transition metal oxide is selected from the group consisting of oxides of yttrium, oxides of transition metals with an atomic number from 41 to 79 and mixtures of these oxides.

59. Process according to claim 1, in which a lithium silicate glass ceramic is used which comprises lithium metasilicate as main crystal phase and has a bending strength in the range of about 180 to 300 MPa and/or a fracture toughness, measured as K.sub.IC value, of at least about 2.0 MPa.Math.m.sup.0.5.

60. Process according to claim 1, in which a lithium silicate glass ceramic is used which comprises lithium disilicate as main crystal phase and has a bending strength in the range of about 400 to 700 MPa and/or a fracture toughness, measured as K.sub.IC value, of at least about 2.0 MPa.Math.m.sup.0.5.

61. Process according to claim 11, in which a lithium silicate glass ceramic is used which comprises at least one caesium aluminosilicate crystal phase, wherein the caesium aluminosilicate has the formula Cs.sub.XAlSi.sub.5O.sub.12, wherein x is 0.70 to 0.90.

62. Process according to claim 12, in which a lithium silicate glass ceramic is used which comprises at least one lithium aluminosilicate crystal phase, wherein the lithium aluminosilicate has the formula Li.sub.2O*Al.sub.2O.sub.3*7.5SiO.sub.2.

63. Process according to claim 16, in which the dental restoration is a bridge, an inlay, an onlay, a veneer, an abutment, a partial crown, a crown or a facet.

64. Process according to claim 17, in which a coating is obtained which comprises a lithium silicate glass ceramic that comprises lithium metasilicate as main crystal phase, and which has a bending strength in the range of about 180 to 300 MPa and/or a fracture toughness, measured as K.sub.IC value, of at least about 2.0MPa.Math.m.sup.0.5.

65. Process according to claim 17, in which a coating is obtained which comprises a lithium silicate glass ceramic that comprises lithium disilicate as main crystal phase, and which has a bending strength in the range of about 400 to 700 MPa and/or a fracture toughness, measured as K.sub.IC value, of at least about 2.0MPa.Math.m.sup.0.5.

66. Process according to claim 21, in which the lithium silicate glass ceramic comprises at least one caesium aluminosilicate crystal phase, wherein the caesium aluminosilicate has the formula Cs.sub.XAlSi.sub.5O.sub.12, wherein x is 0.70 to 0.90.

67. Process according to claim 21, in which the lithium silicate glass ceramic further comprises at least one lithium aluminosilicate crystal phase.

68. Process according to claim 21, in which the lithium silicate glass ceramic further comprises at least one lithium aluminosilicate crystal phase, wherein the lithium aluminosilicate has the formula Li.sub.2O*Al.sub.2O.sub.3*7.5SiO.sub.2.

Description

EXAMPLES

(1) A total of 28 glasses and glass ceramics according to the invention with the compositions given in Table I were produced by melting corresponding starting glasses followed by heat treatment for controlled nucleation and crystallization.

(2) For this, the starting glasses in amounts of 100 to 200 g were first melted from customary raw materials at 1450 to 1550° 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. The obtained glass melts were then poured into pre-heated moulds to produce glass monoliths. All glass monoliths proved transparent.

(3) The glass monoliths were then converted to glasses and glass ceramics according to the invention by thermal treatment. The thermal treatments used for controlled nucleation and controlled crystallization are also given in Table I. The following meanings apply

(4) TABLE-US-00004 T.sub.N and t.sub.N Temperature and time used for nucleation T.sub.C and t.sub.C Temperature and time used for first crystallization T.sub.FC and t.sub.FC Temperature and time used for final crystallization T.sub.press and t.sub.press Temperature and time used for hot pressing

(5) It can be seen that a first heat treatment in the range of from 470 to 580° C. resulted in the formation of lithium silicate glasses with nuclei and these glasses crystallized as a result of a further heat treatment at 600 to 750° C. to form glass ceramics with lithium metasilicate as main crystal phase, as was established by X-ray diffraction tests. Only in the case of Examples 8, 11 and 12 was lithium disilicate (also) formed as main crystal phase. A final heat treatment at a temperature of from 840 to 950° C. finally resulted predominantly in the formation of glass ceramics with lithium disilicate as main crystal phase. In the case of Examples 3, 5 and 9, glass ceramics with lithium metasilicate as main crystal phase were obtained.

(6) The produced lithium disilicate glass ceramics had high fracture toughness values, measured as critical stress intensity factor K.sub.IC according to the SEVNB method, of more than 2.0 MPa.Math.m.sup.0.5 and in particular even at least 2.6 MPa.Math.m.sup.0.5.

(7) The biaxial strength GB was also high, at at least 250 MPa and up to more than 600 MPa. It was determined according to dental standard ISO 6872 (2008) on test pieces that were produced by machining of the respective lithium disilicate glass ceramic. A CEREC-InLab machine (Sirona, Bensheim) was used for the processing.

(8) They were also able to be applied by hot pressing as coatings onto in particular oxide ceramic restorations or metal restorations, e.g. in order to veneer them as desired.

(9) Some examples are described in more detail below:

Example 10

(10) From a mixture of the raw materials with the composition given in Table I for Example 10, a glass was melted at a temperature of 1500° C. for 2 h and a glass frit was produced by subsequent pouring into water. After drying the glass frit in the drying furnace up to 750° C., it was melted again at 1500° C. for 2.5 h and then poured into graphite moulds in order to produce glass monoliths. Immediately after demoulding the hot glass monoliths, they were stress-relieved and nucleated for 10 min at 500° C. and then slowly cooled to room temperature.

(11) Before further processing, the glass blocks were converted to a lithium metasilicate glass ceramic. For this, the glass blocks were placed in a furnace preheated to 400° C. After a residence time of 20 min, the temperature was increased to 700° C. at a heating rate of 10 K/min and this temperature was maintained for 20 min. The blocks were then slowly cooled to room temperature in the closed furnace.

(12) In order to facilitate a CAM processing of the metasilicate blocks by means of Sirona inLab grinding machines, the corresponding holders were glued to the blocks. The grinding processing was carried out with diamond-coated grinding tools. Small discs with a diameter of about 12 mm and a thickness of about 2 mm were ground from the blocks.

(13) The conversion of the ground bodies from the metasilicate state to the disilicate state was carried out via a further thermal treatment. The bodies were heated in a Programat-type furnace (Ivoclar Vivadent AG) to a temperature of 920° C. and, after a residence time of 7 min, cooled slowly to a temperature of 400° C. and removed from the furnace. The XRD analysis of the thus-produced material displayed, in addition to the main phase Li.sub.2Si.sub.2O.sub.5, the secondary phase Cs.sub.0.809 (AlSi.sub.5O.sub.12), among others, which is responsible for a high coefficient of thermal expansion of the glass ceramics. The thus-produced glass ceramic is thereby suitable for joining to metals and metal alloys. The crystallized discs were then ground with diamond grinding wheels to a thickness of about 1.2 mm and polished to 0.5 μm. The biaxial strength was then determined on the thus-produced and prepared samples. An average strength of 608 MPa was measured.

Example 14

(14) From a mixture of the raw materials with the composition given in Table I for Example 14, a glass was melted at a temperature of 1500° C. for 2 h and a glass frit was produced by subsequent pouring into water. The dried glass frit was then melted again at 1500° C. for 2.5 h and then poured into graphite moulds to produce glass monoliths. The stress relief and nucleation of the thus-produced glass blocks was carried out immediately after the demoulding at 500° C. for 10 min, followed by a slow cooling to room temperature.

(15) Before further processing, the glass blocks were converted to the metasilicate state. For this, the glass blocks were placed in a furnace preheated to 400° C. After a residence time of 20 min, the temperature was increased to 600° C. at a heating rate of 10 K/min and this temperature was maintained for 120 min. The blocks were then slowly cooled to room temperature in the closed furnace. An X-ray structural analysis was carried out on the thus-crystallized blocks. Li.sub.2SiO.sub.3 was identified as main crystal phase.

(16) In order to facilitate a CAM processing of the metasilicate blocks by means of Sirona inLab grinding machines, the corresponding holders were glued to the blocks. The grinding processing was carried out with diamond-coated grinding tools. Small discs with a diameter of about 12 mm and a thickness of about 2 mm were ground from the blocks.

(17) The conversion of the ground bodies from the metasilicate state to the disilicate state was carried out via a further thermal treatment. The bodies were heated in a Programat-type furnace (Ivoclar Vivadent AG) to a temperature of 905° C. and, after a residence time of 30 min, cooled slowly to a temperature of 400° C. and removed from the furnace. An XRD analysis of the thus-treated material displayed, in addition to the main crystal phase Li.sub.2Si.sub.2O.sub.5, a lithium aluminosilicate secondary phase, among others. The linear coefficient of thermal expansion CTE.sub.100-400° C. was 9.0-10.sup.−6 K.sup.−1. Because of the low coefficient of thermal expansion, the thus-produced glass ceramic is suitable for joining to zirconium oxide ceramics.

Example 15

(18) From a mixture of the raw materials with the composition given in Table I for Example 15, a glass was melted at a temperature of 1500° C. for 2 h and a glass frit was produced by subsequent pouring into water. The dried glass frit was then melted again at 1500° C. for 2.5 h and then poured into graphite moulds to produce glass monoliths. The stress relief and nucleation of the thus-produced glass blocks were carried out immediately after the demoulding at 500° C. for 10 min, followed by a slow cooling to room temperature.

(19) a) CAM Processing of Metasilicate Blocks and Conversion to Lithium Disilicate

(20) For the conversion to the metasilicate state, the glass blocks were placed in a furnace preheated to 400° C. After a residence time of 20 min, the temperature was increased to 650° C. at a heating rate of 10 K/min and this temperature was maintained for 60 min. The blocks were then slowly cooled to room temperature in the closed furnace. An X-ray structural analysis was carried out on the thus-crystallized blocks. Li.sub.2SiO.sub.3 was identified as main crystal phase.

(21) In order to facilitate a CAM processing of the metasilicate blocks by means of Sirona inLab grinding machines, the corresponding holders were glued to the blocks. The grinding processing was carried out with diamond-coated grinding tools. Small discs with a diameter of about 12 mm and a thickness of about 2 mm were ground from the blocks.

(22) The conversion of the ground bodies from the metasilicate state to the disilicate state was carried out via a further thermal treatment. The bodies were heated in a Programat-type furnace (Ivoclar Vivadent AG) to a temperature of 920° C. and, after a residence time of 60 min, cooled slowly to a temperature of 400° C. and removed from the furnace. The XRD analysis of the thus-produced material displayed, in addition to the main phase Li.sub.2Si.sub.2O.sub.5, the secondary phase Cs.sub.0.809 (AlSi.sub.5O.sub.12), among others. The linear coefficient of thermal expansion CTE.sub.100-400° C. was 13.1.Math.10.sup.−6 K.sup.−1. The thus-produced glass ceramic is therefore suitable for joining to metals and metal alloys.

(23) The crystallized discs were then ground with diamond grinding wheels to a thickness of about 1.2 mm and polished to 0.5 μm. A biaxial strength was then determined on the thus-produced and prepared samples. An average strength of 350 MPa was measured.

(24) b) CAM Processing of Metasilicate Blocks, Conversion to Lithium Disilicate and Joining to Alloy

(25) A further glass block was converted via a temperature treatment at 600° C. for 120 min to a glass ceramic with the main crystal phase Li.sub.2SiO.sub.3. The metasilicate block was then provided with a holder suitable for processing by Sirona inLab grinding machines and an overstructure was ground from the block. The overstructure was then converted to the disilicate state by a temperature treatment at 940° C. for 15 min. A framework structure of the alloy d.SIGN® 30 (Ivoclar Vivadent AG) was covered with the opaquer IPS Classic (Ivoclar Vivadent AG) and then fired. With the help of a silicate glass ceramic solder with a coefficient of thermal expansion of about 13.5.Math.10.sup.−6 K.sup.−1, the framework was then joined to the overstructure at a joining temperature of 800° C. for 7 min.

Example 22

(26) From a mixture of the raw materials with the composition given in Table I for Example 22, a glass was melted at a temperature of 1500° C. for 2 h and a glass frit was produced by subsequent pouring into water. After drying the glass frit in the drying furnace, it was melted again at 1500° C. for 2 h and then poured into graphite moulds in order to produce glass monoliths. Immediately after demoulding the hot glass monoliths, they were stress-relieved and nucleated for 10 min at 480° C. and then slowly cooled to room temperature.

(27) a) CAM Processing of Metasilicate Blocks and Conversion to Lithium Disilicate

(28) In order to facilitate a CAM processing of the metasilicate blocks by means of Sirona inLab grinding machines, the corresponding holders were glued to the blocks. The grinding processing was carried out with diamond-coated grinding tools. Small discs with a diameter of about 12 mm and a thickness of about 2 mm were ground from the blocks.

(29) The conversion of the ground bodies to the disilicate state was carried out via a thermal treatment. The bodies were heated in a Programat-type furnace (Ivoclar Vivadent AG) to a temperature of 900° C. and, after a residence time of 7 min, cooled slowly to a temperature of 400° C. and removed from the furnace.

(30) The crystallized discs were then ground with diamond grinding wheels to a thickness of about 1.2 mm and polished to 0.5 μm. The biaxial strength was then determined on the thus-produced and prepared samples. An average strength of 319 MPa was measured.

(31) b) Hot Pressing of Nucleated Glass to Form Restorations

(32) For the hot pressing, plastic (PMMA) restorations of various geometries were embedded in a dental embedding compound, the plastic was burned out and the nucleated glass blocks were pressed within 2.29 min at a temperature of 950° C. (residence time 25 min) and using an EP5000. After the cooling had completed, the restorations were devested with a sandblaster and separated from their compression channels and ground. The linear coefficient of thermal expansion CTE.sub.100-400° C. was 11.9.Math.10.sup.−6 K.sup.−1.

Example 23A

(33) A mixture of oxides and carbonates with the composition given in Table I for Example 23 was first mixed in a Speed Mixer for 2 minutes and then melted at 1500° C. for 2 h in a platinum/rhodium crucible (Pt/Rh-90/10). The melt was then poured into water in order to obtain a fine-particle granulate which was melted again for 2 h at 1500° C. after drying in order to improve the homogeneity. Cylindrical glass blanks with a diameter of 12.5 mm were then poured into pre-heated, separable steel moulds, transferred to a furnace preheated to 470° C. and stress-relieved for 10 min. In this way, a glass with nuclei was obtained.

(34) a) Hot Pressing of Nucleated Glass to Form Restorations

(35) For the hot pressing, plastic (PMMA) restorations of various geometries were embedded in a dental embedding compound, the plastic was burned out and the nucleated glass cylinders were pressed within 4.20 min at a temperature of 920° C. (residence time 25 min) and using an EP5000. After the cooling had completed, the restorations were devested with a sandblaster and separated from their compression channels and ground. The linear coefficient of thermal expansion CTE.sub.100-400° C. was 12.1.Math.10.sup.−6 K.sup.−1.

(36) b) Hot Pressing of Nucleated Glass on Alloy

(37) The glass with nuclei was crystallized for 30 min at 890° C. and pressed onto a metal alloy d.Sign 30 (Ivoclar Vivadent AG) by hot pressing at 940° C. in a Programat EP 5000-type furnace (Ivoclar Vivadent AG). A ZrO.sub.2-containing opaquer from the IPS Classic® line (Ivoclar Vivadent AG) was used as intermediate layer between metal and pressed glass ceramic. After the pressing process, a defect-free surface was achieved. Thus, this glass ceramic is suitable for pressing over dental crowns of non-precious metal alloys, in particular Co—Cr and Ni—Cr alloys.

Example 23B

(38) From the raw materials of Example 23, a glass was melted at temperatures between 1450 and 1550° C. for 1 to 3 h and a glass frit was produced by subsequent pouring into water. After drying the glass frit in the drying furnace, it was comminuted to a particle size of <45 μm.

(39) a) Coating Glass Powder onto Alloy and Sintering

(40) The glass powder was mixed with a modelling fluid and the mixture was applied to a single tooth crown of the alloy IPS d.SIGN® 30 (Ivoclar Vivadent AG). The opaquer from the IPS Classic® line (Ivoclar Vivadent AG) was used as intermediate layer between metal and coated powder. The coated-on mixture was then sintered twice in a P100 dental furnace (Ivoclar Vivadent AG) at a holding temperature of 850° C. and a residence time of 5 min (2 corrective firings). The sintering was followed by the application of universal glaze (Ivoclar Vivadent AG) and a glaze firing at 850° C. and a residence time of 5 min.

(41) b) Coating of a Sintered Glass onto Alloy and Sintering

(42) The glass powder was processed to form blanks with a weight of 40 g and sintered for one hour at 940° C. The sintered body was then cooled in air for 1.30 min and then quenched in water and dried. This sintered body was comminuted again to a particle size of <45 μm and, analogously to the glass powder, coated onto a single tooth crown of the metal alloy IPS d.SIGN® 30. The opaquer from the IPS Classic® line (Ivoclar Vivadent AG) was likewise used as intermediate layer between metal and coated powder. The corrective firings were carried out at 900° C. for 5 min.

Example 26

(43) A mixture of oxides and carbonates with the composition given in Table I for Example 26 was first mixed in a Speed Mixer for 2 minutes and then melted at 1500° C. for 2 h in a platinum/rhodium crucible (Pt/Rh-90/10). The melt was then poured into water in order to obtain a fine-particle granulate which, after drying, was melted again for 2 h at 1500° C. in order to improve the homogeneity. Cylindrical glass blanks with a diameter of 12.5 mm were then poured into pre-heated, separable steel moulds and transferred to a furnace preheated to 480° C. and stress-relieved for 10 minutes. In this way, a glass with nuclei was obtained.

(44) a) Hot Pressing of Nucleated Glass to Form Restorations

(45) For the hot pressing, plastic (PMMA) restorations of various geometries were embedded in a dental embedding compound, the plastic was burned out and the nucleated glass cylinders were pressed within 1.25 min at a temperature of 930° C. (residence time 25 min) and using an EP5000. After the cooling had completed, the restorations were devested with a sandblaster and separated from their compression channels and ground. The linear coefficient of thermal expansion CTE.sub.100-400° C. was 12.1.Math.10.sup.−6 K.sup.−1.

(46) b) Hot Pressing onto Zirconium Oxide Ceramic

(47) The glass was applied by hot pressing at 940° C. to a zirconium oxide ceramic of the type 3Y-TZP (Tosoh, Japan) in a Programat EP5000 press furnace (Ivoclar Vivadent AG). After completion of the coating process, a defect-free glass ceramic crown was obtained.

(48) TABLE-US-00005 TABLE I Example 1 2 3 4 5 6 7 8 9 10 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 68.3 69.8 59.8 70.4 57.5 69.1 70.4 71.9 55.1 74.1 Li.sub.2O 14.2 14.5 17.0 14.6 17.1 14.4 14.6 14.9 16.0 15.5 Cs.sub.2O 11.1 9.2 10.8 8.0 11.7 9.8 8.1 5.7 10.0 5.1 Al.sub.2O.sub.3 3.3 3.3 4.0 3.2 4.0 3.6 3.2 3.3 4.0 1.9 P.sub.2O.sub.5 3.1 3.2 3.4 3.4 3.4 3.1 3.4 3.4 3.3 3.4 Na.sub.2O — — 0.9 — — — 0.3 0.8 — — K.sub.2O — — — 0.4 — — — — — — CaO — — — — — — — — — — SrO — — — — — — — — — — ZnO — — — — — — — — — — Y.sub.2O.sub.3 — — 3.0 — — — — — — — La.sub.2O.sub.3 — — — — — — — — — TiO.sub.2 — — — — — — — — — — GeO.sub.2 — — — — — — — — 8.0 — ZrO.sub.2 — — — — 4.5 — — — 1.0 — CeO.sub.2 — — 1 — 1.0 — — — 0.9 — V.sub.2O.sub.5 — — 0.1 — 0.1 — — — 0.1 — Ta.sub.2O.sub.5 — — — — — — — — 1.0 — Tb.sub.4O.sub.7 — — — — 0.5 — — — 0.3 — Er.sub.2O.sub.3 — — — — 0.2 — — — 0.3 — B.sub.2O.sub.3 — — — — — — — — — — F — — — — — — — — — — T.sub.g/° C. 492 474 462 492 476 482 472 465 464 477 T.sub.N/° C. 510 510 480 510 500 500 490 480 480 500 t.sub.N/min 10 10 10 10 10 10 10 10 10 10 T.sub.c/° C. 700 700 680 700 720 700 700 700 660 700 t.sub.c/min 20 20 40 20 20 20 10 20 60 20 Main 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 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 crystal Li.sub.2Si.sub.2O.sub.5 phase Other Li.sub.2Si.sub.2O.sub.5 crystal phases T.sub.FC/° C. 920 900 930 900 910 910 880 840 910 920 t.sub.FC/min 7 7 10 7 30 7 7 7 10 7 T.sub.press/° C. t.sub.Press/min Main 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.2SiO.sub.3 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 crystal phase Other Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4 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 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 crystal Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 CAS CAS CAS Li.sub.3PO.sub.4 CAS CAS CAS CAS phases CAS CAS CAS L* a* b* CR CTE.sub.100-400° C./ 13.3 12.9 12.4 11.7 13.6 12.4 11.3 12.2 16.1 10.sup.−6 .Math. K.sup.−1 K.sub.IC/ 2.8 MPa m.sup.0.5 σ.sub.B/MPa 385 470 338 253 432 352 608 CAS = Cs.sub.0.809 (AlSi.sub.5O.sub.12) L*,a*,b*: colour coordinates of the samples, determined according to DIN 5033 and DIN 6174 CR: contrast value as a measure of the translucence, determined according to BS 5612 Example 11 12 13 14 15 16 17 18 19 20 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 74.1 71.7 77.1 71.5 67.1 66.8 64.9 65.9 75.8 71.0 Li.sub.2O 15.5 17.8 12.8 14.9 13.9 13.9 13.5 13.7 15.8 14.8 Cs.sub.2O 5.1 5.2 5.0 5.0 10.9 4.6 10.6 9.4 5.2 4.9 Al.sub.2O.sub.3 1.9 1.9 1.8 5.4 3.2 1.7 3.1 8.0 1.9 1.8 P.sub.2O.sub.5 3.4 3.4 3.3 3.2 3.0 3.0 3.0 3.0 1.3 7.5 Na.sub.2O — — — — — — — — — — K.sub.2O — — — — — — — — — — CaO — — — — — — — — — — SrO — — — — — 3.0 — — — — ZnO — — — — — — — — — — Y.sub.2O.sub.3 — — — — — — 3.0 — — — La.sub.2O.sub.3 — — — — — 3.0 — — — — TiO.sub.2 — — — — — 4.0 — — — — GeO.sub.2 — — — — — — — — — — ZrO.sub.2 — — — — — — — — — — CeO.sub.2 — — — — 1.8 — 1.8 — — — V.sub.2O.sub.5 — — — — 0.1 — 0.1 — — — Ta.sub.2O.sub.5 — — — — — — — — — — Tb.sub.4O.sub.7 — — — — — — — — — — Er.sub.2O.sub.3 — — — — — — — — — — B.sub.2O.sub.3 — — — — — — — — — — F — — — — — — — — — — T.sub.g/° C. 477 464 483 475 476 490 492 478 467 485 T.sub.N/° C. 500 580 500 500 500 510 510 500 490 510 t.sub.N/min 120 5 10 10 10 10 10 10 10 10 T.sub.c/° C. 650 700 700 600 650 t.sub.c/min 10 60 20 120 60 Main Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 crystal phase Other Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3, crystal Li.sub.3PO.sub.4 phases T.sub.FC/° C. 950 880 920 905 920 875 900 875 900 920 t.sub.FC/min 5 7 7 30 60 30 30 10 10 7 T.sub.press/° C. t.sub.Press/min Main 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.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 crystal phase Other Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li2Si02 Li.sub.3PO.sub.4 CAS Li.sub.3PO.sub.4 crystal CAS CAS CAS CAS CAS Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 CAS CAS phases SiO.sub.2 LAS CAS CAS LAS AlPO.sub.4 L* a* b* CR CTE.sub.100-400° C./ 13.2 11.8 16.7 9.0 13.1 9.0 16.5 10.sup.−6 .Math. K.sup.−1 K.sub.IC/ 2.6 2.8 MPa m.sup.0.5 σ.sub.B/MPa 614 334 260 350 CAS = Cs.sub.0.809 (AlSi.sub.5O.sub.12); LAS = Li.sub.2O*Al.sub.2O.sub.3*7.5 SiO.sub.2 L*,a*,b*: colour coordinates of the samples, determined according to DIN 5033 and DIN 6174 CR: contrast value as a measure of the translucence, determined according to BS 5612 Example 21 22 23 24 25 26 27 28 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 69.1 69.0 69.0 68.7 67.6 70.6 68.8 67.5 Li.sub.2O 14.3 13.3 12.6 12.0 12.4 13.6 13.2 11.8 Cs.sub.2O 4.7 8.3 7.8 7.3 7.6 4.5 4.4 7.2 Al.sub.2O.sub.3 1.7 3.7 3.8 4.0 3.7 5.6 5.4 3.9 P.sub.2O.sub.5 3.1 2.9 2.7 2.5 2.6 2.9 2.8 2.5 Na.sub.2O — 0.7 1.0 1.4 1.0 0.7 0.7 1.3 K.sub.2O — 0.7 1.1 1.5 1.1 0.7 0.7 1.4 CaO — 0.1 0.2 0.5 0.2 0.1 0.1 0.3 SrO — 0.2 0.3 0.4 0.3 0.2 0.2 0.4 ZnO — 0.3 0.5 0.6 0.5 0.3 0.3 0.6 Y.sub.2O.sub.3 — — — — — — — — La.sub.2O.sub.3 — — — — — — — — TiO.sub.2 7.1 0.2 0.2 0.3 0.2 0.2 0.2 0.3 GeO.sub.2 — — — — — — — — ZrO.sub.2 — 0.1 0.1 0.1 0.1 0.1 0.1 0.1 CeO.sub.2 — 0.1 0.1 0.1 2.0 0.1 2.0 2.0 V.sub.2O.sub.5 — — — — 0.1 — 0.1 0.1 Ta.sub.2O.sub.5 — — — — — — — — Tb.sub.4O.sub.7 — — — — — — 0.4 — Er.sub.2O.sub.3 — — — — — — 0.2 — B.sub.2O.sub.3 — 0.2 0.3 0.3 0.3 0.2 0.2 0.3 F — 0.2 0.3 0.3 0.3 0.2 0.2 0.3 T.sub.g/° C. 495 456 453 450 456 458 450 456 T.sub.N/° C. 520 480 470 470 480 480 470 480 t.sub.N/min 10 10 10 10 10 10 10 10 T.sub.c/° C. 750 t.sub.c/min 20 Main crystal Li.sub.2SiO.sub.3 phase Other crystal phases T.sub.FC/° C. 870 860 t.sub.FC/min 7 60 T.sub.press/° C. 950 920 900 920 930 900 890 t.sub.Press/min 25 25 25 25 25 25 25 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.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 phase Other crystal Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 phases CAS CAS CAS CAS CAS small small CAS TiO.sub.2 amount amount of CAS of CAS L* 79.3 74.8 82.6 a* 4.5 7.4 1.5 b* 30.9 32.1 33.1 CR 77 79 78 65 CTE.sub.100-400° C./ 11.9 12.1 11.3 11.4 8.8 9.8 11.6 10.sup.−6 .Math. K.sup.−1 K.sub.IC/ MPa m.sup.0.5 σ.sub.B/MPa 319 (900° C./7 min) CAS = Cs.sub.0.809 (AlSi.sub.5O.sub.12) L*,a*,b*: colour coordinates of the samples, determined according to DIN 5033 and DIN 6174 CR: contrast value as a measure of the translucence, determined according to BS 5612