CeO2-stabilized ZrO2 ceramics for dental applications

Abstract

The present invention is directed to a porous pre-densified CeO.sub.2 stabilized ZrO.sub.2 ceramic having a density of 50.0 to 95.0%, relative to the theoretical density of zirconia, and an open porosity of 5 to 50% as well as to ceramic having a density of 97.0 to 100.0%, relative to the theoretical density of zirconia, and wherein the grains of the ceramic have an average grain size of 50 to 1000 nm, methods for the preparation of the pre-densified and densified ceramics and their use for the manufacture of dental restorations.

Claims

1. Porous CeO.sub.2-stabilized ZrO.sub.2 ceramic having a density of 50.0 to 95.0%, relative to the theoretical density of zirconia, and an open porosity of 5 to 50%, wherein the pores of the ceramic have a mean pore diameter of 10 to 500 nm.

2. Porous ceramic according to claim 1 having a density of 60.0 to 90.0%.

3. Porous ceramic according to claim 1 having an open porosity of 10 to 30%.

4. Porous ceramic according to claim 1 having a closed porosity of less than 5%.

5. Porous CeO.sub.2-stabilized ZrO.sub.2 ceramic having a density of 50.0 to 95.0%, relative to the theoretical density of zirconia, and an open porosity of 5 to 50%, wherein grains of the ceramic have an average grain size of 10 to 500 nm.

6. Porous ceramic according to claim 1 comprising tetragonal ZrO.sub.2 in an amount of 50 to 100 vol.-%, based on the total volume of crystals of the ceramic.

7. Porous ceramic according to claim 2 having a density of 70.0 to 85.0%.

8. Porous ceramic according to claim 3 having an open porosity of 14 to 25%.

9. Porous ceramic according to claim 3 having an open porosity of 15 to 23%.

10. Porous ceramic according to claim 4 having a closed porosity of less than 2%.

11. Porous ceramic according to claim 4 having a closed porosity of less than 1%.

12. Porous ceramic according to claim 1, wherein the pores of the ceramic have a mean pore diameter of 25 to 300 nm.

13. Porous ceramic according to claim 1, wherein the pores of the ceramic have a mean pore diameter of 50 to 200 nm.

14. Porous ceramic according to claim 5, wherein the grains of the ceramic have an average grain size of 25 to 300 nm.

15. Porous ceramic according to claim 5, wherein the grains of the ceramic have an average grain size of 50 to 200 nm.

16. Porous ceramic according to claim 6 comprising tetragonal ZrO.sub.2 in an amount of 70 to 100 vol.-%, based on the total volume of crystals of the ceramic.

17. Porous ceramic according to claim 6 comprising tetragonal ZrO.sub.2 in an amount of 90 to 100 vol.-%, based on the total volume of crystals of the ceramic.

18. Method for preparing a porous CeO.sub.2-stabilized ZrO.sub.2 ceramic having a density of 50.0 to 95.0%, relative to the theoretical density of zirconia, and an open porosity of 5 to 50%, wherein the pores of the ceramic have a mean pore diameter of 10 to 500 nm comprising (a) pre-densifying a CeO.sub.2-containing ZrO.sub.2 starting material to provide the porous ceramic.

19. Method according to claim 18, wherein pre-densifying in step (a) is performed by spark plasma sintering which includes heating the CeO.sub.2-containing ZrO.sub.2 starting material to a sintering temperature of about 950 to 1350 C. and/or heating the CeO.sub.2-containing ZrO.sub.2 starting material at a heating rate of 1 to 400 C./min.

20. Method according to claim 18, comprising (b) re-oxidizing the porous ceramic obtained in step (a).

21. Method according to claim 19, wherein pre-densifying in step (a) is performed by spark plasma sintering the CeO.sub.2-containing ZrO.sub.2 starting material to a sintering temperature of about 1050 to 1250 C., and/or heating the CeO.sub.2-containing ZrO.sub.2 starting material at a heating rate of 5 to 100 C./min.

22. Method according to claim 19, wherein pre-densifying in step (a) is performed heating the CeO.sub.2-containing ZrO.sub.2 starting material at a heating rate of 50 to 100 C./min.

23. Method of using a porous CeO.sub.2-stabilized ZrO.sub.2 ceramic having a density of 50.0 to 95.0%, relative to the theoretical density of zirconia, and an open porosity of 5 to 50%, wherein grains of the ceramic have an average grain size of 10 to 500 nm, for the preparation of dental restorations, dental frameworks, dental abutments and dental implants.

Description

(1) FIG. 1 shows an SEM image of the pre-densified CeO.sub.2ZrO.sub.2 ceramic obtained in Example 1. It can be seen that the microstructure of this sample is characterized by very fine, spherical Ce-TZP nanoparticles having a diameter of about 100 nm.

(2) FIG. 2 shows an SEM image of the densified CeO.sub.2ZrO.sub.2 ceramic obtained in Example 1 (left picture) and an SEM image of the CeO.sub.2ZrO.sub.2 ceramic obtained in Comparative Example 1 (right picture). As can be seen, the densification was nearly complete (close to 100% of theoretical density) and only some very small pores of less than 80 nanometers in their biggest dimension were visible in the sample prepared according to the invention (Example 1). Moreover, the grain sizes obtained in the sample of Example 1 are about half of the grain sizes obtained for the sample of Comparative Example 1. The average grain size of the densified ceramic according to Example 1 was 0.60.1 m.

(3) FIG. 3 shows an SEM image of the densified CeO.sub.2ZrO.sub.2 ceramic obtained in Comparative Example 2. In contrast to the fully densified sample of Example 1, the ceramic of Comparative Example 2 is characterized by several, clearly visible pores of about 200 nm.

(4) The mechanical properties of the samples obtained in the examples are given in Table 4.

(5) TABLE-US-00004 TABLE 4 Mechanical properties of the samples after densifying Biaxial Vickers flexural Hardness Standard strength Standard (GPa) deviation (MPa) deviation Example 1 9.070 47 Example 2 9.013 38 Example 3 9.096 43 Comparative 8.390 23 624 35 Example 1 Example 4 >720 35