Nanocrystalline zirconia and methods of processing thereof
Zirconia dental ceramics exhibiting opalescence and having a grain size in the range of 10 nm to 300 nm, a density of at least 99.5% of theoretical density, a visible light transmittance at or higher than 45% at 560 nm, and a strength of at least 800 MPa.
1. A zirconia dental ceramic comprising:
predominantly tetragonal zirconia with less than 15% monoclinic and cubic phases combined;
at least 95% of all grains by volume within the range of 10 nm to 300 nm;
a density of at least 99.5% of theoretical density; and
exhibiting opalescence.
2. The zirconia dental ceramic of claim 1 , comprising an average grain size from 40 nm to 150 nm.
3. The zirconia dental ceramic of claim 2 , comprising an average grain size from 50 nm to 100 nm.
4. The zirconia dental ceramic of claim 3 , comprising an average grain size from 50 nm to 80 nm.
5. The zirconia dental ceramic of claim 1 , wherein at least 95% of all grains are within the range of 20 nm to 250 nm.
6. The zirconia dental ceramic of claim 1 , wherein all the grains are within the range of 10 nm to 300 nm.
7. The zirconia dental ceramic of claim 1 , wherein the opalescence is at least 9.
8. The zirconia dental ceramic of claim 7 , wherein the opalescence is at least 12 and no greater than 28.
9. The zirconia dental ceramic of claim 1 , comprising a visible light transmittance for a one millimeter thickness of greater than 45% at a wavelength in the range of 560 nm to 700 nm.
10. The zirconia dental ceramic of claim 9 , comprising a visible light transmittance for a one millimeter thickness of greater than 45% at a wavelength of 560 nm.
11. The zirconia dental ceramic of claim 9 , comprising a visible light transmittance for a one millimeter thickness of greater than 50% at a wavelength in the range of 560 nm to 700 nm.
12. The zirconia dental ceramic of claim 11 , comprising a visible light transmittance for a one millimeter thickness of greater than 50% at a wavelength of 560 nm.
13. The zirconia dental ceramic of claim 1 , comprising a visible light transmittance for a one millimeter thickness of greater than 35% at a wavelength in the range of 560 nm to 700 nm.
14. The zirconia dental ceramic of claim 13 , comprising a visible light transmittance for a one millimeter thickness of greater than 35% at a wavelength of 560 nm.
15. The zirconia dental ceramic of claim 13 , comprising a visible light transmittance for a one millimeter thickness of greater than 40% at a wavelength in the range of 560 nm to 700 nm.
16. The zirconia dental ceramic of claim 15 , comprising a visible light transmittance for a one millimeter thickness of greater than 40% at a wavelength of 560 nm.
17. The zirconia dental ceramic of claim 1 , wherein the density is at least 99.9% of theoretical density.
18. The zirconia dental ceramic of claim 1 , comprising a flexural strength of at least 800 MPa.
19. The zirconia dental ceramic of claim 18 , comprising a flexural strength of at least 1200 MPa.
20. The zirconia dental ceramic of claim 19 , comprising a flexural strength of at least 2 GPa.
21. The zirconia dental ceramic of claim 18 , comprising a flexural strength of no greater than 2.8 GPa.
22. The zirconia dental ceramic of claim 1 , wherein the opalescence is measured on a 1 mm thick sample by using the formula
OP=[(CIE a T *−CIE a R *) 2 +(CIE b T *−CIE b R *) 2 ] 1/2 ,
wherein (CIEa T *−CIEa R *) is the difference between transmission and reflectance modes in red-green coordinate a* of CIE L*a*b* color space; and
wherein (CIEb T *−CIEb R *) is the difference between transmission and reflectance modes in yellow-blue color coordinate b* of CIE L*a*b* color space.
23. The zirconia dental ceramic of claim 1 , comprising YTZP (yttria-stabilized tetragonal zirconia polycrystal) with 0-3 mol % Y 2 O 3 .
24. The zirconia dental ceramic of claim 1 , comprising less than 0.5% porosity, wherein a majority of pores are at least 25 nm in diameter when porosity is greater than 0.1.
25. The zirconia dental ceramic of claim 24 , comprising less than 0.5% porosity, wherein a majority of pores are at least 30 nm in diameter when porosity is greater than 0.1.
26. The zirconia dental ceramic of claim 1 , wherein the zirconia comprises a stabilizing additive selected from Y, Ce, Mg, or mixtures thereof.
27. A dental article comprising the zirconia dental ceramic of claim 1 .
28. The dental article of claim 27 , fabricated by shaping a green, brown or pre-sintered zirconia material and sintering it to final density greater than or equal to 99.5% of theoretical density.
29. The dental article of claim 27 , formed into blanks, full-contour FPDs (fixed partial dentures), bridges, implant bridges, multi-unit frameworks, abutments, crowns, partial crowns, veneers, inlays, onlays, orthodontic retainers, space maintainers, tooth replacement appliances, splints, dentures, posts, teeth, jackets, facings, facets, implants, cylinders, and connectors.