Method for enhancing optical properties in ceramics having applications in dental restorations

1. Method for enhancing the translucency of a sintered zirconia dental restoration comprising

obtaining a porous zirconia ceramic body that comprises an yttria-stabilized zirconia material comprising 2 mol % yttria to 7 mol % yttria,

wherein the porous zirconia ceramic body is in the shape of a dental restoration having an incisal edge and a facial surface;

obtaining an aqueous yttrium-containing composition comprising

between 20% wt and 70% wt yttrium-containing material,

between 0.05M and 5M citric acid, and

a colorant comprising at least one metal-containing component as a coloring agent; and

providing a first application of the yttrium-containing composition to penetrate a portion of the porous zirconia ceramic body;

providing a second application of the yttrium-containing composition to penetrate the portion of the porous zirconia ceramic body that comprises the aqueous yttrium-containing composition of the first application; and

sintering the porous zirconia ceramic body after the first and second application to form a sintered zirconia dental restoration;

wherein a difference in L* values (CIE color space) between (i) the sintered zirconia dental restoration having the first and second applications of the yttrium-containing composition and (ii) an untreated sintered zirconia dental restoration is less than or equal to 6%.

2. The method of claim 1 wherein the yttria-stabilized zirconia material is a pre-shaded zirconia ceramic material.

3. The method of claim 1 , wherein the yttria-stabilized zirconia material is a pre-shaded zirconia ceramic material and the yttrium-containing composition comprises between 40 wt % and 70 wt % of the yttrium-containing material.

4. The method of claim 1 , wherein the yttria-stabilized zirconia material is a pre-shaded zirconia ceramic material comprising from 3 mol % yttria to 5 mol % yttria, and the yttrium-containing composition comprises between 20 wt % and 40 wt % of an yttrium-chloride.

5. The method of claim 1 , wherein the yttria-stabilized zirconia material is an unshaded, white zirconia ceramic material and the yttrium-containing composition comprises from 20 wt % to 65 wt % of the yttrium-containing material based on the total weight of yttrium-containing composition.

6. The method of claim 1 , wherein the at least one metal-containing component of the colorant comprises one or more metals selected from terbium, erbium, chromium, cobalt and manganese.

7. The method of claim 6 , wherein the colorant comprises one or more coloring agents selected from terbium chloride, chromium chloride, and manganese sulfate.

8. The method of claim 1 , wherein the colorant comprises 0.05 wt % to 2 wt % of a metallic salt as a coloring agent, based on the total weight of the yttrium-containing composition.

9. The method of claim 1 , wherein the porous zirconia ceramic body has a density of 50% to 90% of full theoretical density.

10. The method of claim 1 , wherein the yttria-stabilized zirconia ceramic material comprises 85 wt % to 100 wt % of a zirconia ceramic material.

11. The method of claim 1 , comprising applying the yttrium-containing composition to the facial surface of the dental restoration from an incisal edge to a distance of one-third to one-half the length of the facial surface proximate the incisal edge, and the applying the second application to penetrate a portion of the porous ceramic body that comprises the aqueous yttrium-containing composition from the first application.

12. The method of claim 1 , wherein the first application is applied to the facial surface from the incisal edge for a first distance of 1 mm to 5 mm from the incisal edge, and the second application is applied to the facial surface from the incisal edge for a second distance of 0.5 mm to 3 mm wherein the second distance is less than the first distance.

13. The method of claim 1 , further comprising the step of penetrating through the thickness of the ceramic body with the yttrium-containing composition.

14. The method of claim 1 , wherein the sintered body has an yttria concentration gradient wherein the yttria concentration is increasingly lower as the distance from the incisal edge increases.

15. A method for applying an yttria-containing composition to enhance optical properties of a sintered zirconia ceramic body, comprising an application method comprising

applying a first application of an aqueous yttria-containing composition to an edge of a porous ceramic dental restoration form comprising an yttria-stabilized zirconia ceramic material for a first application distance of 1 mm to 5 mm from the edge, and penetrating a portion of the porous ceramic dental form,

wherein the yttrium-containing composition comprises between 30% wt and 70% wt yttrium-containing material, between 0.05M and 5M citric acid, and a colorant comprising at least one metal-containing component as a coloring agent;

applying a second application of the yttria-containing composition to the edge for a second application distance of 0.5 mm to 3 mm from the edge, penetrating the portion of the porous ceramic dental restoration form containing the aqueous yttria-containing composition from the first application, wherein the second application distance is less than the first application distance, wherein the application method provides at least 46% or greater transmittance at 700 nm when applied to a porous zirconia ceramic body made from the yttria-stabilized zirconia ceramic material having a 1 mm target thickness when sintered to at least 98% theoretical density; and

wherein a difference in L* values (CIE color space) between (i) a sintered zirconia ceramic body having the first and second applications of the yttrium-containing composition and (ii) an untreated sintered zirconia ceramic body is less than or equal to 6%; and

sintering the porous ceramic dental restoration form after the first and second application to form a dental restoration.

16. The method of claim 15 , wherein the porous, yttria-stabilized zirconia ceramic material is a pre-shaded zirconia ceramic material, the yttrium-containing material is between 40% wt and 70% wt, and the application method provides at least 50% or greater transmittance at 700 nm after sintering, when applied to the porous zirconia ceramic body made from the yttria-stabilized zirconia ceramic material shaped to a target thickness of 1 mm when sintered.

17. The method of claim 15 , wherein the porous, yttria-stabilized zirconia ceramic material is a pre-shaded zirconia ceramic material, the yttrium-containing material is between 50% wt and 70% wt, and the application method results in at least 50% or greater transmittance at 700 nm after sintering, when applied to the porous zirconia ceramic body made from the yttria-stabilized zirconia ceramic material shaped to a target thickness of 1 mm when sintered.

18. Method for enhancing the translucency of a sintered zirconia dental restoration comprising

obtaining a porous zirconia ceramic body formed from an yttria-stabilized zirconia powder comprising 2 mol % yttria to 5 mol % yttria,

wherein the porous zirconia ceramic body is in the shape of a dental restoration;

obtaining an yttrium-containing composition comprising between 20 wt % and 70 wt % of an yttrium salt dissolved in an aqueous solvent, between 0.05M and 5M citric acid, and a colorant comprising at least one metal-containing component as a coloring agent; and

providing a first application of the yttrium-containing composition to penetrate a portion of the porous zirconia ceramic body;

providing a second application of the yttrium-containing composition to penetrate the portion of the porous zirconia ceramic body that comprises the yttrium-containing composition of the first application; and

sintering the porous zirconia ceramic body after the first and second applications to form a sintered zirconia dental restoration;

wherein a difference in L* values (CIE color space) between (i) a sintered zirconia ceramic body having the first and second applications of the yttrium-containing composition and (ii) an untreated sintered zirconia ceramic body is less than or equal to 6%.

19. The method of claim 18 , wherein the yttrium-containing composition is applied to a facial surface adjacent a biting edge of the porous zirconia ceramic body.

20. The method of claim 18 , wherein the yttrium salt comprises at least one of yttrium chloride, yttrium nitrate or yttrium carbonate.

21. The method of claim 18 , wherein the yttrium-containing composition comprises between 40 wt % and 70 wt % yttrium salt dissolved in the aqueous solvent.

22. The method of claim 18 , wherein the yttrium-containing composition comprises between 20 wt % and 65 wt % yttrium salt dissolved in the aqueous solvent.

23. The method of claim 18 , wherein the yttrium-containing composition comprises between 40 wt % and 60 wt % yttrium salt dissolved in the aqueous solvent.

24. The method of claim 18 , wherein the yttria-stabilized zirconia powder comprises 3 mol % yttria to 5 mol % yttria.

25. The method of claim 18 , wherein the coloring agent comprises at least one metallic salt, and the coloring agent provides a dental shade to the porous zirconia ceramic body after sintering.

26. The method of claim 25 , wherein the yttrium-containing composition comprises 0.05 wt % to 2 wt % of the at least one metallic salt, based on the total weight of the yttrium-containing composition.

27. The method of claim 18 , wherein the porous zirconia ceramic body is formed from an unshaded, white yttria-stabilized zirconia powder.

28. The method of claim 18 , wherein the yttria-stabilized zirconia powder comprises a shaded zirconia ceramic powder that provides a dental shade to the porous zirconia ceramic body after sintering.