Slip-casting method of fabricating zirconia blanks for milling into dental appliances

• US 20090115084A1
• Filed: 10/27/2008
• Published: 05/07/2009
• Est. Priority Date: 11/05/2007
• Status: Abandoned Application

• Current Assignee: James R Glidewell Dental Ceramics Incorporated
• Original Assignee: James R Glidewell Dental Ceramics Incorporated
• Inventors: Moon, Haksung
• Application Number:
  US12/290,089
• Publication Number:
  US 20090115084A1
• Time in Patent Office: Days
• US Class Current: 264/16
• CPC Class Codes: A61C 13/0003 Making bridge-work, inlays, implants or the like
• CPC Class Codes: A61C 13/0022 Blanks or green, unfinished dental restoration parts
• CPC Class Codes: A61K 6/84 comprising metals or alloys

Abstract

A process for fabricating pre-sintered zirconia blanks that are then computer machined and sintered to form dental appliances having highly advantageous features. The principal steps of a preferred embodiment of that process comprise a) preparing a ceramic slurry of binderless zirconia powder; b) subjecting the slurry to attrition milling; c) preparing a vacuum assisted slip casting mold and pouring the milled slurry into the slip-casting mold; d) after casting, excess slurry is poured from the mold and a consolidated zirconia blank is removed; e) drying the blank and pre-sintering it to form solid blanks ready for CAD/CAM machining and sintering to net shape.

Claims

1. A process for fabricating dental appliances of translucent zirconia;

the process comprising the steps of;

a) preparing a slurry of binderless zirconia powder;

b) attrition milling the slurry;

c) slip casting the milled slurry in a vacuum assisted mold;

d) removing zirconia blanks formed in said slip casting step;

e) allowing the blanks to dry;

f) pre-sintering the dried blanks;

g) shaping the fully dried, pre-sintered blanks into a desired appliance form; and

h) sintering the appliance-shaped blanks to net shape and size.

2. The process recited in claim 1 wherein step c) is performed in an openable silicone mold secured in surrounding engagement with a plaster of paris mold and attached to a vacuum.

3. The process recited in claim 1 wherein step c) is performed wherein a polymer sleeve is in radial surrounding engagement with a plaster of paris mold.

4. The process recited in claim 1 wherein step a) is performed by dispersing the zirconia powder in deionized water.

5. The process recited in claim 1 wherein step a) is performed by dispersing the zirconia powder in water.

6. The process recited in claim 1 wherein step a) is performed by dispersing the zirconia powder in water by controlled pH.

7. The process recited in claim 1 wherein step a) comprises the additional step of ultra-sonicating the slurry to remove soft agglomerates for improved mixing of the powder.

8. The process recited in claim 1 wherein step b) is performed using a zirconia bowl.

9. The process recited in claim 1 wherein step f) is performed at a temperature in the range of about 850°

C. to 1200°

C.

10. The process recited in claim 1 wherein step f) is performed at a temperature in the range of about 850°

C. to 1200°

C. for about two hours.

11. A process for forming millable blanks of zirconia for use in fabricating dental appliances;

the process comprising the steps of;

a) preparing a slurry of zirconia powder dispersed by chemical dispersants in deionized water;

b) mixing the slurry to form a homogeneous slurry;

c) pouring the mixed slurry into a vacuum-assisted slip casting assembly;

d) allowing zirconia blanks to form in said assembly and removing said blanks therefrom; and

e) subjecting said zirconia blanks to a presintering temperature to achieve partial densification of said blanks.

12. The process recited in claim 11 wherein step c) is performed in an openable silicone mold secured in surrounding engagement with a plaster of paris mold and attached to a vacuum.

13. The process recited in claim 11 wherein step c) is performed wherein a polymer sleeve is in radial surrounding engagement with a plaster of paris mold.

14. The process recited in claim 11 wherein step a) is performed by dispersing the zirconia powder in water by controlled pH.

15. The process recited in claim 11 wherein step a) comprises the additional step of ultra-sonicating the slurry to remove soft agglomerates for improved mixing of the powder.

16. The process recited in claim 11 wherein step b) is performed using a zirconia bowl.

17. The process recited in claim 11 wherein step f) is performed at a temperature in the range of about 850°

C. to 1200°

C.

18. The process recited in claim 11 wherein step e) is performed at a temperature in the range of about 850°

C. to 1200°

C. for about two hours.

19. The process in claim 11 wherein said chemical dispersants in step a) comprise tetramethyl ammonium hydroxide.