Method for producing a blank and dental restoration
The invention relates to a method for the preparation of a blank from a ceramic material, wherein at least two layers of ceramic material of different compositions are filled into a die layer-by-layer and after filling of the layers they are then pressed and sintered, wherein after filling of a first layer this is structured on its surface in such a way that the first layer, viewed across its surface, differs in its height from region to region, and then a layer with a composition that differs from the first layer is filled as a second layer into the mold.
1. A method for producing a blank from a ceramic material, comprising the steps of:
filling a die with at least two layers of ceramic materials of different compositions in pourable condition layer-by-layer;
pressing the at least two layers of ceramic materials of different composition; and
sintering the pressed at least two layers of ceramic materials of different compositions,
wherein after filling of a first layer of a first ceramic material in pourable condition, a surface of the first layer is structured in such a way that the first layer when viewed across the surface, the surface differs from region to region in height in such a way that elevations and depressions or valleys are formed, and
wherein a layer of a second ceramic material in pourable condition with a composition that is different from that of the first layer is filled into the die to form a second layer,
wherein filing the die with the second ceramic material, a portion of the second ceramic material is disposed within the depressions or valleys formed between the elevations the first ceramic material along the structured surface of the first layer to form an intermediate layer having both the first ceramic material and the second ceramic material, the intermediate layer being located between the first layer having the first ceramic material and the second layer having the second ceramic material; and
wherein the height of the intermediate layer is 1/10 to 1/5 of the total height of the at least two layers to be filled into the die.
2. The method according to claim 1 , wherein the surface of the first layer is structured in such a way that result in the elevations, with the depressions or valleys that are demarcated from the elevations.
3. The method according to claim 1 , wherein a ring structure is formed in the surface when viewed from above, which shows concentrical elevations and depressions.
4. The method according to claim 1 , wherein the structure is produced by an element that moves in relative to the first layer and which structures the first layer in its surface region by means of a section which has a wave-like, comb-like or saw-tooth-like shape.
5. The method according to claim 1 , wherein the structure is generated by a pressure element that acts in the direction of the surface of the first layer.
6. The method according to claim 1 , wherein the pressure element used is such that elevations extending concentrically or parallel are pressed into the surface of the first layer with depressions extending between them.
7. The method according to claim 1 , wherein the structure is formed such that the volume of the elevations is equal to, or approximately equal to, the volume of the depressions.
8. The method according to claim 1 , wherein the materials used as ceramic materials include zirconium dioxide doped with yttrium oxide (Y 2 O 3 ), calcium oxide (CaO), magnesium oxide (MgO) and/or cerium oxide (CeO 2 ), wherein the material of the first layer differs from the material of the second layer in terms of color and/or the proportions of stabilized crystal forms present at room temperature.
9. The method according to claim 1 , wherein the first layer in an unstructured state has a height that is half, or approximately half the total height H of the first and second layers.
10. The method according to claim 1 , wherein the material used as the first and/or second ceramic material is one in which the percentage of yttrium oxide in the first layer is 4.5 wt % to 7.0 wt % and/or the percentage in the second layer is 7.0 wt % to 9.5 wt %, wherein the percentage of yttrium oxide in the first layer is lower than in the second layer.
11. The method according to claim 1 , wherein prior to the step of sintering, the method further comprises the step of pre-sintering the pressed at least two layers of ceramic materials of different compositions such that the ceramic material used for the first layer and the second layer is one in which the ratio of tetragonal crystal phase to cubic crystal phase of the zirconium dioxide both in the first layer and in the second layer after pre-sintering is 1.