Process for treating a porous dental zirconia block with coloring solutions

A process for treating a porous dental zirconia mill block with a coloring solution, the process comprising the steps of:

• providing a porous dental zirconia mill block having two opposing surfaces, surface U and surface L,
• treating the surface U of the porous dental zirconia mill block with a coloring solution A1, wherein the surface U corresponds to an upper surface of the porous dental zirconia mill block when the surface U is being treated with the coloring solution A1, and wherein the coloring solution A1 is provided with a volume VA1,
• turning the porous dental zirconia mill block around about an axis parallel to at least one of the two opposing surfaces to reduce a migration distance for the coloring solution A1 through the porous dental zirconia mill block compared to a distance between surface U and surface L, and
• treating the surface L of the porous dental zirconia mill block with a coloring solution A2, wherein upon turning the porous dental zirconia mill block the surface L corresponds to the upper surface of the porous dental zirconia mill block when the surface U is being treated with the coloring solution A2, and wherein the coloring solution A2 is provided with a volume VA2,
• wherein the volume of at least one of the coloring solutions A1 or A2 is applied in discrete portions incrementally to ensure uniform spread and absorption,
• wherein the following condition is met:
• V0=ΣVAx with x≥2,
• with V0 being an overall amount of coloring solutions used to infiltrate the porous dental zirconia mill block.