LITHIUM SILICATE MATERIALS

• US 20080120994A1
• Filed: 11/05/2007
• Published: 05/29/2008
• Est. Priority Date: 08/07/2003
• Status: Active Grant

• Current Assignee: Ivoclar Vivadent AG
• Original Assignee: Ivoclar Vivadent AG
• Inventors: RHEINBERGER, Volker M., HOLAND, Wolfram, SCHWEIGER, Marcel, BURKE, Harald
• Granted Patent: US 8,042,358 B2
• Time in Patent Office: Days
• US Class Current: 65/33.4
• 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 process for manufacturing a lithium silicate restoration comprising preparing 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,

and

(e) shaping the lithium silicate blank into a dental restoration.

2. A process according to claim 1, wherein the shaping of the lithium silicate blank into a dental restoration of step (e) comprises coating a dental framework with the lithium silicate blank.

3. A process according to claim 2 wherein the dental framework is coated by hot pressing the lithium silicate blank onto the dental framework.

4. A process according to claim 3, wherein the dental framework is a crown, a partial crown, a bridge, a coping, a veneer, a facing or an abutment.

5. A process according to claim 4, wherein the dental framework is made from a metal, an alloy, a ceramic or a glass ceramic.

6. A process according to claim 5, wherein the ceramic comprises zirconium oxide, aluminium oxide, a zirconium mix oxide, an aluminium mix oxide, or a combination thereof.

7. A process according to claim 3, 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.

8. A process according to claim 1, 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.

9. A process according to claim 8 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.

10. A process according to claim 8 wherein the machining is performed by grinding or milling.

11. A process according to claim 10, wherein the machining is controlled by a computer.

12. A process according to claim 8, 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.

13. A process according to claim 12 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.

14. A process according to claim 12 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.

15. A process according to claim 12, wherein the linear shrinkage that occurs during the third heat treatment is about 0.2 to 0.3%.

16. A process according to claim 8 which comprises shaping of a lithium silicate material to the desired geometry by hot pressing to produce the dental restoration.

17. A process for manufacturing a dental restoration according to claim 16 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.

18. A process according to claim 17 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.

19. A process according to claim 12 which comprises an increasing of strength and fracture toughness of the lithium silicate material.

20. A process according to claim 8, 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.

21. A process according to claim 8, further comprising finishing the dental restoration to obtain a natural appearance.

22. A process according to claim 21, 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.

23. A process according to claim 12, 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.

24. A process according to claim 17, which comprises an increasing of strength and fracture toughness of the lithium silicate material.