Lithium Silicate-Wollastonite Glass Ceramic

Abstract

Lithium silicate-wollastonite glass ceramics are described which are characterized by a controllable translucence and can be easily machined and therefore can be used in particular as restoration material in dentistry.

Claims

1. Lithium silicate-wollastonite glass ceramic, which comprises lithium silicate as a crystal phase and wollastonite as a further crystal phase.

2. Glass ceramic according to claim 1, which comprises 55.0 to 74.0 wt.-% SiO.sub.2.

3. Glass ceramic according to claim 1, which comprises 10.0 to 18.0 wt.-% Li.sub.2O.

4. Glass ceramic according to claim 1, which comprises 4.0 to 17.0 wt.-% CaO.

5. Glass ceramic according to claim 1, which comprises 0.5 to 6.0 wt.-% Al.sub.2O.sub.3.

6. Glass ceramic according to claim 1, which comprises 0 to 5.0 wt.-% K.sub.2O.

7. Glass ceramic according to claim 1, which comprises 1.0 to 7.0 wt.-% P.sub.2O.sub.5.

8. Glass ceramic according to claim 1, which comprises 0 to 13.0 wt.-% further alkali metal oxide Me.sup.I.sub.2O, wherein Me.sup.I.sub.2O is selected from Na.sub.2O, Rb.sub.2O and/or Cs.sub.2O.

9. Glass ceramic according to claim 1, which comprises 0 to 6.0 wt.-% further oxide of divalent elements Me.sup.IIO, wherein Me.sup.IIO is selected from MgO, SrO and/or ZnO.

10. Glass ceramic according to claim 1, which comprises 0 to 6.0 wt.-% oxide of trivalent elements Me.sup.III.sub.2O.sub.3, wherein Me.sup.III.sub.2O.sub.3 is selected from B.sub.2O.sub.3, Y.sub.2O.sub.3, La.sub.2O.sub.3 and/or Er.sub.2O.sub.3.

11. Glass ceramic according to claim 1, which comprises 0 to 8.0 wt.-% further oxide of tetravalent elements Me.sup.IVO.sub.2, wherein 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.

12. Glass ceramic according to claim 1, which comprises 0 to 6.0 wt.-% further oxide of pentavalent elements Me.sup.V.sub.2O.sub.5, wherein 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.

13. Glass ceramic according to claim 1, which comprises 0 to 6.0 wt.-% oxide of hexavalent elements Me.sup.IVO.sub.3, wherein Me.sup.IVO.sub.3 is selected from WO.sub.3 and/or MoO.sub.3.

14. Glass ceramic according to claim 1, which comprises at least one of the following components in the amounts specified: TABLE-US-00009 Component wt.-% SiO.sub.2 56.0 to 74.0 Li.sub.2O 10.0 to 18.0 CaO 4.0 to 17.0 Al.sub.2O.sub.3 0.5 to 6.0 K.sub.2O 0 to 5.0 P.sub.2O.sub.5 1.0 to 7.0 Me.sup.I.sub.2O 0 to 13.0 Me.sup.IIO 0 to 6.0 Me.sup.III.sub.2O.sub.3 0 to 6.0 Me.sup.IVO.sub.2 0 to 8.0 Me.sup.V.sub.2O.sub.5 0 to 6.0 Me.sup.VIO.sub.3 0 to 6.0.

15. Glass ceramic according to claim 1, which comprises lithium disilicate and/or lithium metasilicate.

16. Glass ceramic according to claim 1, which comprises lithium metasilicate or lithium disilicate as main crystal phase.

17. Glass ceramic according to claim 1, which comprises lithium phosphate as further crystal phase.

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

19. Starting glass, which comprises the components of the glass ceramic according to claim 1 and comprises nuclei for the crystallization of lithium silicate and/or wollastonite.

20. Starting glass according to claim 19, which is present in the form of a ground powder or a compact made of ground powder.

21. Process for the preparation of the glass ceramic according to claim 1, in which (a) a starting glass which comprises components of the glass ceramic and comprises nuclei for the crystallization of lithium silicate and/or wollastonite is ground, (b) optionally the ground starting glass is pressed to form a powder compact and (c) the ground starting glass or the powder compact is subjected to at least one heat treatment at a temperature in the range of 700 to 950 C. for a period of 5 to 120 min.

22. Process of using lithium silicate-wollastonite glass ceramic, which comprises lithium silicate as a crystal phase and wollastonite as a further crystal phase 8 or a starting glass which comprises components of the lithium silicate-wollastonite glass ceramic and comprises nuclei for the crystallization of lithium silicate and/or wollastonite dental material for the preparation of dental restorations.

23. Process according to claim 22, wherein the glass ceramic is given the shape of the desired dental restoration comprising a bridge, inlay, onlay, veneer, abutment, partial crown, crown or facet, by pressing or machining.

Description

EXAMPLES

Examples 1 to 32Composition and Crystal Phases

[0077] In total, 32 glasses and glass ceramics with the composition specified in Table I were prepared.

[0078] The following meanings apply in Table I: [0079] T.sub.g glass transition temperature, determined by means of DSC [0080] T.sub.S and t.sub.S temperature and time used for melting the starting glass [0081] T.sub.Kb and t.sub.Kb temperature and time used for nucleation of the starting glass [0082] T.sub.Sinter and t.sub.Sinter temperature and time used for the heat treatment for the crystallization and sintering of compacts [0083] T.sub.press and t.sub.press temperature and holding time at temperature used for pressing crystallized compacts [0084] CR value contrast value of the glass ceramic according to British Standard BS 5612 [0085] Li.sub.2Si.sub.2O.sub.5 lithium disilicate [0086] Li.sub.2SiO.sub.3 lithium metasilicate [0087] CaSiO.sub.3 wollastonite [0088] KM ground with ball mill [0089] AFG ground with jet mill

[0090] In Examples 1 to 32 glasses made of 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. granular glass material, were prepared by pouring the melted starting glasses into water. The three process variants A), B) and C) indicated below were used for the further processing of the glass frits into glass ceramics according to the invention.

[0091] It was shown that, depending on the P.sub.2O.sub.5 content, the lithium disilicate crystals obtained had a size of about 500 nm to 6 m. The lithium disilicate crystals formed a crosslinked and interlocked structure, which is presumably also responsible for the good mechanical properties of the glass ceramics. The wollastonite crystals were present scattered in the lithium disilicate structure and had a size of about 5 m to more than 10 m.

[0092] A) Vibratory Mills

[0093] The glass frits prepared according to Examples 1 to 30 were ground with a KM100 vibratory mill from Retsch GmbH, Haan, Germany, or an RM31 zirconium oxide vibratory mill from Retsch GmbH, Haan, Germany, to an average particle size of <90 m, 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 to determine the crystal phases present as well as colour measurements were carried out on the prepared test pieces.

[0094] B) Jet Mill

[0095] The glass frit with the composition according to Example 31 was ground in an AFG 100 opposed jet mill from Hosokawa Alpine to an average particle size of 23 m, 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. X-ray diffraction analyses were carried out on the test pieces prepared in this way.

[0096] C) Ball Mill

[0097] The glass frits with the composition according to Example 31 and 32 were ground in a ball mill to an average particle size of 23 m, relative to the number of particles. The ball mill had, as grinding chamber, a cylindrical porcelain container with a volumetric capacity of 5 l. The following mixture of porcelain grinding balls was used as grinding medium: 0.9 kg with diameter 10 mm, 1.8 kg with diameter 20 mm and 0.9 kg with diameter 30 mm. The ground glass powders were 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. X-ray diffraction analyses were carried out on the test pieces prepared in this way to determine the crystal phases. The content of wollastonite crystals in these glass ceramics was higher than in the glass ceramics prepared according to variants A) and B).

TABLE-US-00008 TABLE 1 Example No. 1 2 3 4 5 6 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 62.4 68.2 64.5 63.3 63.4 63.2 Li.sub.2O 13.0 14.1 13.4 13.2 13.2 13.1 CaO 15.4 7.7 10.0 9.8 9.9 9.8 MgO SrO ZnO Na.sub.2O K.sub.2O 3.4 3.7 3.5 3.4 3.4 3.4 Cs.sub.2O Rb.sub.2O Al.sub.2O.sub.3 3.0 3.2 3.1 3.0 3.0 3.0 B.sub.2O.sub.3 Y.sub.2O.sub.3 La.sub.2O.sub.3 ZrO.sub.2 P.sub.2O.sub.5 2.8 3.1 5.5 5.4 5.4 5.4 GeO.sub.2 CeO.sub.2 1.7 1.2 1.2 V.sub.2O.sub.5 0.2 0.2 0.2 Er.sub.2O.sub.3 0.3 0.7 TiO.sub.2 SnO.sub.2 Nb.sub.2O.sub.5 Ta.sub.2O.sub.5 MoO.sub.3 WO.sub.3 T.sub.g/ C. 472.3 464.1 466.3 466.9 467.5 468.5 T.sub.Kb/ C., t.sub.Kb/min. 480, 20 480, 20 490, 20 490, 20 490, 20 490, 20 T.sub.s/ C., t.sub.s/min. 1500, 60 1500, 120 1500, 90 1500, 90 1500, 90 1500, 90 Main crystal phase 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.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Further crystal CaSiO.sub.3, 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, phases Li.sub.3PO.sub.4 Li.sub.3PO.sub.4, CaSiO.sub.3 CaSiO.sub.3 CaSiO.sub.3 CaSiO.sub.3 CaSiO.sub.3 T.sub.Sinter/ C., t.sub.Sinter/min. 850, 5 850, 30 810, 5 830, 30 810, 10 810, 30 T.sub.press/ C., t.sub.press/min. Example No. 7 8 9 10 11 12 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 64.1 60.7 67.2 65.8 63.1 60.8 Li.sub.2O 13.3 16.5 13.9 13.7 13.1 12.7 CaO 10.0 10.3 10.2 10.1 9.9 9.5 MgO SrO ZnO Na.sub.2O 5.6 K.sub.2O 3.5 3.6 3.5 3.5 3.3 Cs.sub.2O Rb.sub.2O Al.sub.2O.sub.3 3.1 3.2 3.1 1.3 4.9 2.9 B.sub.2O.sub.3 Y.sub.2O.sub.3 La.sub.2O.sub.3 ZrO.sub.2 P.sub.2O.sub.5 6.0 5.7 5.6 5.6 5.5 5.2 GeO.sub.2 CeO.sub.2 V.sub.2O.sub.5 Er.sub.2O.sub.3 TiO.sub.2 SnO.sub.2 Nb.sub.2O.sub.5 Ta.sub.2O.sub.5 MoO.sub.3 WO.sub.3 T.sub.g/ C. 466.4 450.8 467.9 461.9 462.7 436.8 T.sub.Kb/ C., t.sub.Kb/min. 490, 20 470, 20 490, 20 480, 20 480, 20 460, 20 T.sub.s/ C., t.sub.s/min. 1500, 60 1500, 90 1500, 90 1500, 90 1500, 90 1500, 120 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.2Si.sub.2O.sub.5 Li.sub.2SiO.sub.3 Further crystal 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.3PO.sub.4, phases CaSiO.sub.3 CaSiO.sub.3 CaSiO.sub.3, CaSiO.sub.3 Li.sub.3PO.sub.4, CaSiO.sub.3 LiAlSi.sub.2O.sub.6, CaSiO.sub.3 SiO.sub.2 T.sub.Sinter/ C., t.sub.Sinter/min. 850, 5 850, 5 880, 5 850, 30 800, 30 800, 30 T.sub.press/ C., t.sub.press/min. Example No. 13 14 15 16 17 18 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 56.9 63.3 61.5 62.1 62.5 61.8 Li.sub.2O 11.9 13.2 12.8 12.9 13.0 12.9 CaO 8.9 9.9 9.6 9.7 9.7 9.6 MgO 1.8 SrO 4.6 ZnO 3.6 Na.sub.2O K.sub.2O 3.1 3.4 3.3 3.4 3.4 3.4 Cs.sub.2O 11.6 Rb.sub.2O Al.sub.2O.sub.3 2.7 3.0 2.9 3.0 3.0 3.0 B.sub.2O.sub.3 3.1 Y.sub.2O.sub.3 4.0 La.sub.2O.sub.3 ZrO.sub.2 P.sub.2O.sub.5 4.9 5.4 5.3 5.3 5.3 5.3 GeO.sub.2 CeO.sub.2 V.sub.2O.sub.5 Er.sub.2O.sub.3 TiO.sub.2 SnO.sub.2 Nb.sub.2O.sub.5 Ta.sub.2O.sub.5 MoO.sub.3 WO.sub.3 T.sub.g/ C. 473.8 462 461.3 463.1 468.6 474.7 T.sub.Kb/ C., t.sub.Kb/min. 490, 20 490, 20 480, 20 460, 20 470, 20 470, 20 T.sub.s/ C., t.sub.s/min. 1500, 90 1500, 90 1500, 90 1500, 120 1500, 120 1500, 90 Main crystal phase 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.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.2SiO.sub.3, Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4, Li.sub.2SiO.sub.3, phases CaSiO.sub.3, Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, CaSiO.sub.3 Li.sub.3PO.sub.4, CsAlSi.sub.5O.sub.12 CaSiO.sub.3 CaSiO.sub.3 CaSiO.sub.3 CaSiO.sub.3, Y.sub.2O.sub.3 T.sub.Sinter/ C., t.sub.Sinter/min. 820, 30 810, 30 810, 30 810, 30 810, 30 810, 30 T.sub.press/ C., t.sub.press/min. Example No. 19 20 21 22 23 24 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 61.5 60.2 62.1 61.0 62.4 61.5 Li.sub.2O 12.8 12.5 12.9 12.7 13.0 12.8 CaO 9.6 9.4 9.7 9.5 9.7 9.6 MgO SrO ZnO Na.sub.2O K.sub.2O 3.3 3.3 3.4 3.3 3.4 3.3 Cs.sub.2O Rb.sub.2O Al.sub.2O.sub.3 2.9 2.9 3.0 2.9 3.0 2.9 B.sub.2O.sub.3 Y.sub.2O.sub.3 La.sub.2O.sub.3 ZrO.sub.2 5.4 P.sub.2O.sub.5 5.3 5.2 5.3 5.2 5.3 5.3 GeO.sub.2 4.6 CeO.sub.2 V.sub.2O.sub.5 3.2 Er.sub.2O.sub.3 TiO.sub.2 3.6 SnO.sub.2 6.5 Nb.sub.2O.sub.5 4.6 Ta.sub.2O.sub.5 MoO.sub.3 WO.sub.3 T.sub.g/ C. 466.8 487.9 471.8 479.3 455.8 472.1 T.sub.Kb/ C., t.sub.Kb/min. 470, 20 460, 20 470, 20 480, 20 480, 20 490, 20 T.sub.s/ C., t.sub.s/min. 1500, 60 1500, 60 1500, 60 1500, 60 1500, 60 1500, 60 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.2SiO.sub.3, Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, phases CaSiO.sub.3 Li.sub.3PO.sub.4,, Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, CaSiO.sub.3 CaSiO.sub.3 CaSiO.sub.3, CaSiO.sub.3 CaSiO.sub.3 SnO.sub.2 T.sub.Sinter/ C., t.sub.Sinter/min. 800, 30 810, 60 800, 30 810, 60 790, 30 790, 60 T.sub.press/ C., t.sub.press/min. Example No. 25 26 27 28 29 30 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 62.7 61.8 67.5 61.9 72.7 70.9 Li.sub.2O 13.1 12.9 14.0 12.9 12.9 12.8 CaO 9.8 9.6 7.6 9.6 7.7 7.7 MgO SrO ZnO Na.sub.2O K.sub.2O 3.4 3.4 1.6 3.4 1.0 0.9 Cs.sub.2O Rb.sub.2O Al.sub.2O.sub.3 3.0 2.9 1.8 3.0 3.3 5.4 B.sub.2O.sub.3 Y.sub.2O.sub.3 La.sub.2O.sub.3 4.4 ZrO.sub.2 P.sub.2O.sub.5 5.4 5.3 3.1 5.3 2.4 2.3 GeO.sub.2 CeO.sub.2 V.sub.2O.sub.5 Er.sub.2O.sub.3 TiO.sub.2 SnO.sub.2 Nb.sub.2O.sub.5 Ta.sub.2O.sub.5 3.9 MoO.sub.3 2.6 WO.sub.3 4.1 T.sub.g/ C. 466.7 469.6 465.3 470.8 470.7 473.8 T.sub.Kb/ C., t.sub.Kb/min. 490, 20 490, 20 490, 20 490, 20 480, 20 490, 20 T.sub.s/ C., t.sub.s/min. 1500, 60 1500, 60 1500, 90 1500, 90 1500, 90 1500, 90 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.3PO.sub.4, Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, Li.sub.3PO.sub.4, phases CaSiO.sub.3 CaSiO.sub.3, CaSiO.sub.3 CaSiO.sub.3 CaSiO.sub.3, CaSiO.sub.3, CaWO.sub.4 SiO.sub.2, LiAlSi.sub.3O.sub.8, Li.sub.xAl.sub.xSi.sub.1xO.sub.2 T.sub.Sinter/ C., t.sub.Sinter/min. 810, 30 810, 30 850, 30 810, 30 870, 5 870, 5 T.sub.press/ C., t.sub.press/min. Example No. 31 32 Composition wt.-% wt.-% SiO.sub.2 66.1 68.1 Li.sub.2O 13.8 14.1 CaO 7.6 5.1 MgO SrO ZnO Na.sub.2O K.sub.2O 3.6 3.7 Cs.sub.2O Rb.sub.2O Al.sub.2O.sub.3 3.2 3.2 B.sub.2O.sub.3 Y.sub.2O.sub.3 La.sub.2O.sub.3 ZrO.sub.2 P.sub.2O.sub.5 5.7 5.8 GeO.sub.2 CeO.sub.2 V.sub.2O.sub.5 Er.sub.2O.sub.3 TiO.sub.2 SnO.sub.2 Nb.sub.2O.sub.5 Ta.sub.2O.sub.5 MoO.sub.3 WO.sub.3 T.sub.g/ C. 471.3 (KM)/469.8 (AFG) 467.8 (KM) T.sub.Kb/ C., t.sub.Kb/min. 500, 20 (KM)/(AFG) 500, 20 (KM) T.sub.s/ C., t.sub.s/min. 1500, 120 1500, 120 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 CaSiO.sub.3 CaSiO.sub.3, SiO.sub.2 T.sub.Sinter/ C., t.sub.Sinter/min. 800, 5 (KM); 800, 20 (AFG) 850, 10 (KM) T.sub.press/ C., t.sub.press/min. 900/25

Example 33Hot Pressing

[0098] A glass with the composition according to Example 31 was melted in a platinum crucible at a temperature of 1500 C. and then poured into water. The glass frits prepared in this way were ground with an AFG 100 opposed jet mill from Hosokawa Alpine to an average particle size of 23 m, relative to the number of particles. A powder compact was prepared by uniaxial pressing from the glass powder obtained. The press blank was densely sintered at a temperature of 800 C. and a holding time of 20 min in a Programat-type furnace. The densely sintered and already crystallized blank was then pressed by means of hot pressing at a temperature of 900 C. with a holding time of 25 min. The pressed test piece had a CR value of 86.65 and a coefficient of thermal expansion of 10.75*10.sup.6 K.sup.1, measured in the range of 100 to 500 C.

Example 34Machinability

[0099] To test the machinability, glass powders according to Examples 3, 5 and 31 were pressed uniaxially to form blocks and densely sintered in a Programat-type furnace. Corresponding holders were then glued 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, which was possible without problems and only with low tool wear.