UNIFORMLY COLOURED CERAMIC FRAMEWORK AND COLOURING SOLUTION

1 . A process for treating a dental ceramic framework, the process comprising:

a) providing a presintered ceramic framework;

b) providing a colouring solution comprising:

i) a solvent;

ii) a metal salt or metal complex, soluble in the solvent, wherein the amount of the metal ions in the composition is in the range of 0.01 to 7.0% by weight; and

iii) polyethylene glycol having a Mn in the range of 10,000 to 50,000 in an amount of 1 to 8% by weight of the total composition;

wherein the metal salt is selected from rare earth elements and/or the subgroups of the rare earth elements and/or salts of transition metals of the groups IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB;

c) treating the presintered ceramic framework with the colouring solution to form a treated presintered ceramic framework; and

d) firing the treated presintered ceramic framework.

2 . The process of claim 1 , further comprising the step of drying the treated ceramic framework after it has been treated with the solution.

3 . The process according to claim 1 , wherein the presintered ceramic framework is treated with the solution for about 1 to 5 minutes at room temperature.

4 . The process according to claim 1 , wherein the firing takes place for a ZrO 2 based ceramic at a temperature above 1300° C. and lasts for at least 0.5 h and for a Al 2 O 3 based ceramic at a temperature above 1350° C. and lasts for at least 0.5 h.

5 . The process according to claim 1 , wherein the firing takes place at a temperature above about 1300° C.

6 . The process according to claim 8 , wherein treating the presintered ceramic framework comprises dipping the framework into the solution, spraying the solution onto the framework, brushing the solution onto the framework, or by using a sponge or fabric to apply the solution to the framework.

7 . The process of claim 1 , wherein the ceramic framework is selected from presintered bodies comprising ZrO 2 and/or Al 2 O 3 .

8 . The process of claim 1 , wherein the colouring solution does not include pigments.

9 . A process of reducing the sintering deformation of a dental ceramic framework during firing, the method comprising:

a) providing a dental ceramic framework;

b) providing a solution comprising:

i) a solvent;

ii) a metal salt or metal complex, soluble in the solvent, wherein the amount of the metal ions in the composition is in the range of 0.01 to 7.0% by weight; and

iii) polyethylene glycol having a Mn in the range of 10,000 to 50,000 in an amount of 1 to 8% by weight of the total composition;

wherein the metal salt is selected from rare earth elements and/or the subgroups of the rare earth elements and/or salts of transition metals of the groups IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB;

c) treating the ceramic framework with the solution to form a treated ceramic framework; and

d) firing the treated ceramic framework to form a sintered dental ceramic framework;

wherein the sintered dental ceramic framework has reduced sintering deformation compared to a dental ceramic framework fired the same way but without being treated with the solution.

10 . The process of claim 9 , wherein providing a dental ceramic framework comprises providing a presintered dental ceramic framework.

11 . The process of claim 10 , wherein the ceramic framework is selected from presintered bodies comprising ZrO 2 and/or Al 2 O 3 .

12 . The process of claim 9 , further comprising the step of drying the treated ceramic framework after it has been treated with the solution.

13 . The process according to claim 9 , wherein the ceramic framework is treated with the solution for about 1 to 5 minutes at room temperature.

14 . The process according to claim 9 , wherein the firing takes place for a ZrO 2 based ceramic at a temperature above 1300° C. and lasts for at least 0.5 h and for a Al 2 O 3 based ceramic at a temperature above 1350° C. and lasts for at least 0.5 h.

15 . The process according to claim 9 , wherein the firing takes place at a temperature above about 1300° C.

16 . The process of claim 9 , wherein the solution does not include pigments.

17 . A method for colouring a dental ceramic framework, the method comprising:

a) providing a dental ceramic framework;

b) providing a colouring solution comprising:

i) a solvent;

ii) a metal salt or metal complex, soluble in the solvent, wherein the amount of the metal ions in the composition is in the range of 0.01 to 7.0% by weight; and

iii) polyethylene glycol having a Mn in the range of 10,000 to 50,000 in an amount of 1 to 8% by weight of the total composition;

wherein the metal salt is selected from rare earth elements and/or the subgroups of the rare earth elements and/or salts of transition metals of the groups IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB;

c) treating the ceramic framework with the colouring solution to form a treated ceramic framework; and

d) firing the treated ceramic framework to form a sintered dental ceramic framework;

wherein the sintered dental ceramic framework has improved uniformity in colouring compared to a dental ceramic framework fired the same way but without being treated with the colouring solution.

18 . The process of claim 17 , wherein providing a dental ceramic framework comprises providing a presintered dental ceramic framework.

19 . The process of claim 18 , wherein the ceramic framework is selected from presintered bodies comprising ZrO 2 and/or Al 2 O 3 .

20 . The process of claim 17 , further comprising the step of drying the treated ceramic framework after it has been treated with the solution.

21 . The process according to claim 17 , wherein the ceramic framework is treated with the solution for about 1 to 5 minutes at room temperature.

22 . The process according to claim 17 , wherein the firing takes place for a ZrO 2 based ceramic at a temperature above 1300° C. and lasts for at least 0.5 h and for a Al 2 O 3 based ceramic at a temperature above 1350° C. and lasts for at least 0.5 h.

23 . The process of claim 17 , wherein the colouring solution does not include pigments.