Lithium silicate glass ceramic and method for fabrication of dental appliances

• US 20090256274A1
• Filed: 09/12/2008
• Published: 10/15/2009
• Est. Priority Date: 04/11/2008
• Status: Active Grant

• Current Assignee: James R Glidewell Dental Ceramics Incorporated
• Original Assignee: James R Glidewell Dental Ceramics Incorporated
• Inventors: Castillo, Rodolfo
• Granted Patent: US 7,892,995 B2
• Time in Patent Office: Days
• US Class Current: 264/16
• CPC Class Codes: A61K 6/816 comprising titanium oxide
• CPC Class Codes: A61K 6/818 comprising zirconium oxide
• CPC Class Codes: A61K 6/822 comprising rare earth metal oxides
• CPC Class Codes: A61K 6/824 comprising transition metal oxides
• 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 3/097 containing phosphorus, niobium or tantalum
• CPC Class Codes: C03C 4/0021 for dental use

Abstract

The present invention relates to preparing an improved lithium silicate glass ceramic for the manufacture of blocks for dental appliance fabrication using a CAD/CAM process. The lithium silicate material has a chemical composition that is different from those reported in the prior art including 8 to 10% of germanium dioxide in the final composition. The softening points are close to the crystallization final temperature of 830° C. indicating that the samples will support the temperature process without shape deformation. The resulting material has improved castability and higher density.

Claims

1. A lithium silicate ceramic glass made from a composition mixture comprising:

up to about 59% wt SiO2;

up to about 20% wt Li₂O;

up to about 10% wt GeO₂; and

selected amounts % wt of at least Al₂O₃, K₂O, B₂O₃, CeO₂ and P₂O₅.

2. The lithium silicate ceramic glass recited in claim 1 wherein said composition mixture also comprises one or more of the components ZrO₂, TiO₂, Er₂O₃, V₂O₅, MnO₂, Tb₄O7, Ta₂O₅, Dy₂O₃, Sm₂O₃, Pr₂O₃, Ho₂O₃ and Eu₂O₃.

7. The lithium silicate ceramic glass recited in claim 1 comprising a molar ratio of (SiO₂+GeO₂)/Li₂O between 1.7 and 2.5 and SiO2/GeO2 molar ratio equal to or less than 13.

3. A lithium silicate ceramic glass made from a composition mixture comprising:

about 54.3% wt SiO₂;

about 15.2% wt Li₂O; and

about 7.6% wt GeO₂.

4. The lithium silicate ceramic glass recited in claim 3 wherein said composition mixture also comprises at least 1.9% wt of each of Al₂O₃, K₂O, P₂O₅, ZrO₂, CeO₂, Pr₂O₃ and Sm₂O₃.

5. The lithium silicate ceramic glass recited in claim 4 further comprising one or more of the following additional components TiO2, Er₂O₃ and V₂O₅.

6. A Lithium silicate material recited in claim 5 wherein the lithium silicate crystals form 50 to 60 vol % of the lithium silicate material.

8. A method of fabricating dental restorations made of lithium silicate glass;

the method comprising the steps of;

(a) blending a mix of precursors;

(b) ball milling the mix to homogenize components of the mix;

(c) melting the resultant mix of step (b) for about 1 to 3 hours at a temperature of about 1400°

to 1500°

C.;

(d) pouring the melt of step (c) into graphite molds to form shaped blanks and cooling such blanks to room temperature;

(e) heating the blanks of step (d) at a temperature of 625°

to 650°

C. for 10 to 60 minutes;

(f) milling the blanks of step (e) into dental restorations; and

(g) heating the restorations of step (f) at a temperature of 760°

to 830°

C.

9. The method of claim 8 wherein one of said precursors in step (a) is germanium oxide.