Sintered molding, its manufacturing method, and use of sintered molding

Abstract

The present invention relates to a compact having a color profile for use in the manufacture of dental restorations obtained by sintering a pressed compact comprising two or more differently colored ceramic powder layers, characterized in that each powder layer comprises at least 80% by weight of ZrO2 and is essentially free of iron oxide, and at least one powder layer comprises terbium oxide (Tb4O7).

Description

[Technical field]

[0001] The present invention relates to a sintered molding with a color gradient for use in the manufacture of dental restorations, obtained by sintering a compression molding comprising two or more ceramic powder layers with different colors, as well as a method for its manufacture and the use of the molding for the manufacture of dental restorations. [Background technology]

[0002] DE 10 2016 106 370 A1 describes a method for producing zirconia-containing colored blanks for the production of dental restorations, in which powdered starting materials, at least some of which contain coloring elements, are mixed, the resulting die mixture is compressed and then subjected to a heat treatment. The powder mixture used contains elements such as bismuth that produce a fluorescent effect, but which can have a detrimental effect on the sintering performance.

[0003] WO 2018 / 115529 discloses a multilayer oxide ceramic body comprising at least two layers, at least one of which contains lanthanum oxide and in which the lanthanum oxide content is different in at least two different layers. The lanthanum oxide is used to adapt the sintering performance.

[0004] EP 3108849 A1 describes porous multi-layered coloured zirconia-based blanks, in which the individual powder layers can have different thicknesses.

[0005] EP 3772497 A1 describes a sintered moulding with a colour gradient for use in dental restorations having a powder layer, the powder layer containing iron oxide.

[0006] Zirconia ceramics have been introduced into dental engineering for the manufacture of dental restorations due to their hardness and good processability, as well as their controllable translucency. The coloring of ZrO2 ceramics is usually done by adding coloring oxides that are sintered together with the zirconia. To obtain a color gradient that matches the natural color of the tooth, it suggests itself to vary the concentration of the coloring oxide from layer to layer and adjust the color gradient to be as close as possible to the natural color of the tooth. However, there is the problem that coloring metal oxides can affect the sintering performance of the zirconia ceramic. This has been confirmed especially when iron oxides are used. The layered structure of zirconia ceramics, where the concentration of iron oxide varies from layer to layer, leads to sintering distortion of the ceramic. Such distortions must then be compensated / corrected, which is difficult. Moreover, the different sintering performance from layer to layer also leads to different hardness of the individual layers, which further complicates processing by subtractive methods for the manufacture of dental restorations. Summary of the Invention [Problem to be solved by the invention]

[0007] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to provide a sintered moulding which solves the above mentioned problems, in particular which can be sintered without distortion over a wide temperature range.

[0008] It is a further object of the present invention to provide a ceramic sintered molding having a color gradient that has a substantially uniform hardness and is therefore easily processable. [Means for solving the problem]

[0009] The above-mentioned object is achieved by the sintering molding according to claim 1 of the present invention. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 shows an example of a dental restoration obtained from an exemplary ceramic molding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In a first embodiment, the invention relates to a sintered moulding with a colour gradient for use in the manufacture of dental restorations obtained by sintering a compression moulding comprising two or more ceramic powder layers with different colours, characterized in that each powder layer comprises at least 80% by weight of ZrO2 and is essentially free of iron oxide, and at least one powder layer comprises terbium oxide.

[0012] As used herein, "essentially free of iron oxide" means that the powder layer contains less than 0.01 wt. %, preferably less than 0.001 wt. %, or less than 0.0001 wt. %, respectively, of iron oxide based on the total weight of the powder layer. In a preferred embodiment, the sintered molding is free of iron oxide.

[0013] The use of terbium oxide has proven to provide both excellent color and strain stability.

[0014] "Terbium oxide" in the sense of the present invention essentially includes all oxides of terbium. Preferably, said terbium oxide is Tb2O3, Tb4O7, Tb7O 12 , Tb 11 O 20 , TbO2, and mixtures thereof.

[0015] More preferably, TbO, TbO 12 , Tb 11 O 20 A terbium oxide selected from the group consisting of , and any mixtures thereof may be used.

[0016] Particularly preferably, the terbium oxide is in the form of Tb4O7 or Tb4O7 and Tb7O 12 , and / or Tb 11 O 20 It is a mixture of.

[0017] Additionally, terbium oxide having mixed valence is preferred.

[0018] In a preferred embodiment, at least one powder layer, preferably at least two powder layers, or at least three powder layers, or at least four powder layers, in particular five powder layers, or all powder layers comprise terbium oxide in an amount of 0.001-0.15 wt.-%, preferably 0.01-0.1 wt.-%, in particular 0.02-0.08 wt.-%, in particular 0.02-0.06 wt.-%.

[0019] Surprisingly, it has been found that each of the sintered powder layers undergoes essentially equal volume changes over the temperature range of 25-1600°C, particularly over the temperature range of 50-1400°C, or over the temperature range of 900-1400°C, particularly over the temperature range of 900-1350°C.

[0020] As used in the present invention, "essentially equal volume changes" means that the difference in volume changes at a specified temperature in the range of 25 to 1600°C of the two layers of a blank sintered according to the present invention is at most 1%, preferably at most 0.5%, in particular at most 0.05%.

[0021] This results in low distortion of the sintered molding according to the invention.

[0022] In a further preferred embodiment of the present invention, each powder layer has a different concentration of terbium oxide, erbium oxide, and cobalt oxide.

[0023] In a preferred embodiment, each powder layer has only terbium oxide, erbium oxide, and cobalt oxide as the coloring metal oxides.

[0024] In another embodiment, each powder layer contains terbium oxide, erbium oxide, and cobalt oxide, but is essentially free of other colored metal oxides.

[0025] As used herein, "essentially free of other coloring metal oxides" means that the powder layer contains less than 0.01 wt.%, preferably less than 0.001 wt.%, or less than 0.0001 wt.%, each of other coloring metal oxides, based on the total weight of the powder layer. In a preferred embodiment, the sintered molding does not contain other coloring metal oxides.

[0026] In a further preferred embodiment of the invention, at least one powder layer, preferably two or more powder layers, in particular all powder layers are essentially free of elements which produce a fluorescent effect, in particular essentially free of bismuth.

[0027] As used herein, "essentially free of elements that produce a fluorescent effect" means that the powder layer contains less than 0.01% by weight, preferably less than 0.001% by weight, or less than 0.0001% by weight, of each of these elements based on the total weight of the powder layer. In a preferred embodiment, the sintered molding does not contain other metal oxides that produce a fluorescent effect.

[0028] The use of lanthanum oxide in dental restorations can adversely affect the color composition, i.e., the interaction of the colored metal oxides used in the powder compositions used according to the present invention.

[0029] Therefore, in a further preferred embodiment of the present invention, at least one powder layer, preferably two or more powder layers, in particular all powder layers, are essentially free of lanthanum oxide.

[0030] As used herein, "essentially free of lanthanum oxide" means that the powder layer contains less than 0.004 wt.%, preferably less than 0.001 wt.%, or less than 0.0001 wt.%, of lanthanum oxide, based on the total weight of the powder layer. In a preferred embodiment, the sintered molding does not contain lanthanum oxide.

[0031] EP 3108849 A1 discloses a porous, coloured multi-layer zirconia blank in which the layers are arranged to have different thicknesses.

[0032] Preferably at least one powder layer, more preferably two or more powder layers, in particular each powder layer, contains erbium oxide (Er2O3) in an amount of 0.1-1.0% by weight, in particular 0.2-0.8% by weight, based on the total weight of the powder layers. Surprisingly, it has been found that erbium oxide can be used as a coloring metal oxide in such amounts without adversely affecting the sintering properties.

[0033] In a further preferred embodiment of the present invention, the weight ratio of terbium oxide to cobalt oxide is in the range of 80:1 to 5:1, preferably 75:1 to 10:1, in particular 60:1 to 15:1 in at least one powder layer, preferably in at least two or three powder layers, in particular in each powder layer. In particular, good coloring and sintering properties can be achieved with the above-mentioned adjusted weight ratio, especially when Tb4O7 is used.

[0034] Each powder layer can be preferably produced by mixing base powders. In a preferred embodiment, the production of each powder layer is carried out by mixing two or more, preferably three or more, in particular four or more base powders. The use of limited amounts of base powders in different amounts for the production of each powder layer has advantages in terms of compatibility of the individual layers stacked on top of each other and their color gradient in sintered molding. Suitable base powders can be obtained, for example, from Tosoh Corporation.

[0035] The sintered moulding of the present invention preferably has a step-wise colour gradient. In one embodiment of the present invention, the blank has layers with different colours and the sintering process results in a step-wise colour gradient.

[0036] In a preferred embodiment of the present invention, at least two, and preferably all, of the powder layers have essentially the same yttria content.

[0037] As used herein, "essentially the same yttria content in two or more layers" means that the difference within the layers is no more than 0.1 mol %, preferably no more than 0.05 mol %, in particular less than 0.01 mol %.

[0038] In another embodiment of the invention, the sintered molding has a translucent gradient.Preferably, the molding according to the invention exhibits a layer-by-layer increase in yttria content.

[0039] In a preferred embodiment, the molding according to the invention has powder layers each having at least 0.02% by weight of Al2O3.

[0040] It has been found to be suitable for each of the powder layers to have at least 0.02% by weight of Al2O3, preferably 0.03-0.15% by weight of Al2O3, in particular 0.03-0.08% by weight of Al2O3. The preferred amount of Al2O3 in the individual powder layers improves the stability and strength performance of the moulding according to the invention.

[0041] In another embodiment of the invention, at least one, preferably at least two or at least three, in particular all, powder layers comprise Y2O3 and / or Er2O3 in an amount of preferably at least 3 wt.-%, in particular at least 5 wt.-%, or at least 6 wt.-%, in particular 4.5-12 wt.-%, in particular 6-10 wt.-%, based on the total weight of the components of the powder layers.

[0042] Y2O3 has the function of stabilizing the zirconia crystalline phase and is not a colouring metal oxide within the meaning of the present invention.

[0043] Erbium oxide (Er2O3) has the function of stabilizing the crystalline phase of ZrO2 and is a colouring metal oxide within the meaning of the present invention.

[0044] Preferably, the powder layer comprises zirconia and / or HfO2 in an amount of at least 89 wt.-%, preferably 89-98 wt.-%, in particular 90-96 wt.-%, each based on the total weight of the components of the powder layer.

[0045] In a preferred embodiment, the powder layer comprises zirconia and hafnia, more preferably the amount of hafnia is 0.1-5 wt. %, especially 0.5-2.5 wt. %, based on the total weight of zirconia and hafnia.

[0046] In a preferred embodiment of the invention, the compression moulding is composed of three or four, especially five, different ceramic powder layers.

[0047] In a further preferred embodiment of the present invention, the compression molding consists of five ceramic powder layers, the first powder layer comprising 20-30%, preferably 22-28%, of the total thickness of the stacked powder layers, the second powder layer comprising 10-20%, preferably 12-18%, the third powder layer comprising 15-25%, preferably 17-23%, the fourth powder layer comprising 10-20%, preferably 12-18%, and the fifth powder layer comprising 20-30%, preferably 22-28%, totalling 100% of the total thickness.

[0048] In one embodiment of the present invention, the sintered molding is first pre-sintered and processed by a subtractive process, and preferably then final sintered in a separate step.

[0049] The sintered mouldings according to the invention can in particular be used as dental restorations or for the production of dental restorations.

[0050] In another embodiment of the invention, at least one powder layer, preferably all powder layers, further comprises an organic component, preferably in an amount of 3-6 wt. %, in particular in an amount of 4-5 wt. %. Suitable organic components include in particular binders and press additives, which can be easily removed by heat in a binder removal step. Suitable binders for zirconia sintered powders are known to those skilled in the art. These include, for example, polyvinyl alcohol (PVA).

[0051] Preferably, the layered powder is 1.2 g / cm 3 It has a bulk density of less than 1000 nm.

[0052] A particle size D of 35 μm to 85 μm, preferably 40 μm to 80 μm, in particular 50 μm to 70 μm, or 40 to 60 μm 50 It has been found to be suitable to use a layered powder having the following properties: The granular powder is measured in the dry state by laser diffraction using a Cilas granulometer.

[0053] Typically, the inorganic components of the base powder, i.e. the inorganic components after removal of organic components such as binders, have a particle size D measured by laser diffraction of 0.1 to 1 μm, preferably 0.2 μm to 0.8 μm, in particular 0.2 μm to 0.7 μm. 50 It has been found that the particle size has a positive effect on sintering, especially on the color gradient between the individual powder layers.

[0054] The sintered compression mouldings according to the invention can be obtained by stacking two or three, or in particular four or five or more ceramic powder layers layer by layer. The stacking of layers may be carried out, for example, in a cylindrical container to form a disk. Usually, uniaxial pressing of the powder layers can be carried out after the application of each layer. This can be done, for example, by using a pressing plunger, which only causes a preliminary compression. The uniaxial pressing of the layers perpendicular to the layer surface is preferably carried out under a pressure of 10 to 20 MPa, in particular 12 to 15 MPa.

[0055] In another preferred embodiment, the layered ceramic powder layers are first pressed to form a compression molding by uniaxial pressing, and a pressure of preferably 2.8 g / cm is applied perpendicular to the layer plane. 3 Density less than 2.5-2.75 g / cm 3 , e.g. 2.65g / cm 3 The uniaxial precompression results in a better, more intimate mix and can result in a more uniform transition between layers.

[0056] In another preferred embodiment, the pressing to produce the compression moulding is carried out isostatically, said isostatic pressing being preferably carried out following a uniaxial pre-compression and having a pressure of 3.4 g / cm 3 Density less than 2.80~3.3g / cm 3 Density, especially 2.85-3.25g / cm 3 The isostatic pressing is preferably performed after all layers of the compression molding are stacked. Suitable pressures for the isostatic pressing are usually in the range of 500-10000 bar, preferably in the range of 800-8000 bar, for example 1000-7000 bar, or 1000-3000 bar.

[0057] The thickness of the individual powder layers of the compression molding may vary. In a preferred embodiment, at least two of the ceramic powder layers differ in thickness. Preferably, at least two of the ceramic powder layers of the compression molding have a thickness difference of at least 5%. Typically, the compression molding may be in the form of a cylindrical disk having a diameter in the range of 50-200 mm, for example 75-150 mm. The total thickness of the cylindrical disk may for example be in the range of 8-40 mm, preferably 10-30 mm, in particular 13-25 mm. The dimensions refer to the compression molding in the green state.

[0058] For color design and subsequent processing, it has been found to be advantageous if at least one, preferably both, of the outer ceramic powder layers of the compression molding is thicker than the ceramic powder layers between the outer ceramic powder layers. In particular, when the ceramic molding produced according to the invention is used for the production of dental restorations, a layer structure having at least one thicker outer layer as described above has been found to be advantageous, since it is a structure suitable for processing in a CAD / CAM system or other subtractive processing methods.

[0059] In a particularly preferred embodiment of the invention, the compression molding comprises five ceramic powder layers, the first powder layer comprising 20-30%, preferably 22-28%, of the total thickness of the stacked powder layers, the second powder layer comprising 10-20%, preferably 12-18%, the third powder layer comprising 15-25%, preferably 17-23%, the fourth powder layer comprising 10-20%, preferably 12-18%, and the fifth powder layer comprising 20-30%, preferably 22-28%, totalling 100% of the total thickness.

[0060] In another embodiment of the invention, sintering is carried out at a temperature in the range of 950-1100°C, preferably 980-1050°C, to form a pre-sintered ceramic molding (white body). Typically, sintering is carried out for a time sufficient to remove the existing binder and give the compression molding sufficient strength for subtractive processing. The pre-sintered and binder-removed compression molding is referred to as a "white body."

[0061] In one embodiment, sintering to form the white body is carried out for more than 30 minutes, preferably more than 1 hour, in particular more than 20 hours or more than 50 hours, for example from 60 to 200 hours, or from 70 to 150 hours.

[0062] In particular, for producing ceramic dental restorations, the pre-sintered ceramic moulding is suitably processed by subtractive methods and preferably then final sintered in a separate step. When subtractive methods are applied, sintering shrinkage is usually taken into account in the calculations.

[0063] The final sintering is usually carried out at a temperature above 1350°C, preferably above 1400°C, in particular in the range from 1420°C to 1600°C, or from 1450°C to 1590°C, or from 1480°C to 1580°C.

[0064] The sintering time for the final sintering is usually more than 4 minutes, preferably more than 5 minutes, and particularly within the range of 5 to 120 minutes.

[0065] The molding of the present invention can be used in particular in the dental field.The molding of the present invention features high edge strength, excellent structure, and high three-point bending strength in dental restorations.Therefore, the ceramic molding of the present invention is preferably a dental restoration such as inlay, onlay, crown, bridge, or veneer.

[0066] The invention further relates to the use of a ceramic moulding according to the invention for a dental restoration or for producing a dental restoration.

[0067] The invention further relates to the use of a base powder comprising zirconium oxide and terbium oxide, in particular Tb4O7, and yttrium oxide, for producing ceramic dental restorations without sintering distortion, preferably having a color gradient.

[0068] The base powder preferably comprises yttria in an amount of 5-8 wt.-%, preferably 6-7 wt.-%, terbium oxide in an amount of 0.1-0.4 wt.-%, preferably 0.1-0.3 wt.-%, and zirconia in an amount of more than 80 wt.-%, preferably 82 wt.-% to 94 wt.-%, in particular 84 wt.-% to 90 wt.-%, each based on the total weight of the base powder.

[0069] The invention further relates to a method for producing a sintered moulding according to the invention with a colour gradient, comprising the following steps: a) providing 2 or 3 or 4 or 5 or more layers of ceramic powder, which are stacked on top of each other; b) pressing the layered ceramic powder layers together to form a compression molding; c) sintering the molding obtained in step b) to form a ceramic molding, wherein each of the ceramic powder layers has a different composition, and each ceramic powder layer comprises a mixture of at least two different base powders, each of the base powders having at least 80% by weight ZrO2, the weights indicated being based on the total weight of the base powders.

[0070] Above, preferred embodiments of the method according to the invention have been described.

[0071] The invention further relates to a sintered molding having a layer structure and a color gradient for use in the manufacture of dental restorations, wherein the molding comprises at least three different ceramic powder layers, each layer consisting of at least three or four different base powders, each base powder comprising at least 80% by weight of a ceramic oxide, the weights indicated being based on the total weight of the base powders, respectively.

[0072] Preferably, the ceramic powder layer comprises a ceramic oxide as defined above. The base powders used correspond respectively to the base powders defined above. EXAMPLES

[0073] Table 1 shows five base powders A to E used in the composition of the ceramic powder layer. 50 The inorganic components of the base powder have a particle size D of 0.2 to 0.7 μm. 50 has.

[0074] The weights given are each based on the total weight of the powder composition.

[0075] [Table 1] JPEG2024544336000003.jpg212154

[0076] The layer arrangement shown in Table 2 below indicates the composition of each individual ceramic powder layer in the compression molding. The compression molding is provided for use in the manufacture of dental restorations, so that the layer composition is designed according to the tooth position. The composition of the powder layers is formed from the base powders by varying the ratios to obtain an ideal color gradient. The composition of each powder layer is achieved by homogeneously mixing the base powders in the amounts described. The powders are then placed layer by layer in a cylindrical mold with a diameter of 100 mm, with the layer thickness set at 18 mm. The powder layers are uniaxially precompressed under a pressure of 13 MPa perpendicular to the layer surface and then isotropically compressed under a pressure of 2000 bar.

[0077] This is followed by debindering for about 100 hours at about 1000° C. The white body thus obtained is ground into dental restorations using a CAD / CAM system.

[0078] These pre-sintered and processed white bodies are then subjected to final sintering at 1450° C. for 120 minutes.

[0079] [Table 2]

[0080] In this embodiment, the ceramic powder layers are arranged such that Layer 1 (tip) constitutes 25% of the total thickness of the compression molding, Layer 2 (dentin / tip) 15%, Layer 3 (dentin) 20%, Layer 4 (dentin / neck) 15%, and Layer 5 (neck) 25%.

[0081] Surprisingly, it was found that no sintering distortion could be observed even at higher temperatures compared to formulations containing iron oxide resulting in the same color design. In comparison, sintering distortion was observed in formulations containing iron oxide known from the prior art. As the proportion of iron oxide increases, sintering increases, and as a result, the Vickers hardness in the white body also increases from the lighter layers (lower proportion of iron oxide) to the darker layers (higher proportion of iron oxide). In contrast, the embodiment according to the invention colored with terbium oxide is distortion-free throughout the layer, and therefore the degree of sintering is uniform throughout the layer, which also results in a uniform distribution of Vickers hardness and therefore consistent processing properties in CAM processing.

[0082] Figure 1 shows an example of a dental restoration obtained from an exemplary ceramic molding. An anterior crown 2 is shown.

[0083] Layer and color transitions are smooth. Restorations show excellent edge strength and stability. No reworking or rematching of tooth color is required.

[0084] An optimal structure and configuration of the layers exhibits a substantially uniform shrinkage throughout the layers during sintering, which is particularly advantageous for flawless production of dental restorations, since laborious reworking can be substantially avoided.

[0085] Table 3 below shows examples of various tooth colors of VITA Classical A1-D4 that can be achieved using the base powder.

[0086] [Table 3] JPEG2024544336000006.jpg244162 JPEG2024544336000007.jpg96162

[0087] With respect to ingredients, the weights listed add up to 100% by weight, including binder and zirconia.

[0088] Table 4: Different tooth colors that can be obtained by mixing base powders These can be used, for example, as powder layer material for the sinter moulding according to the invention.

[0089] [Table 4]

[0090] Table 5: Examples of monolayer compositions The powder layer composition is obtained by mixing base powders.

[0091] [Table 5]

[0092] The powder compositions for the individual powder layers of the sintered moulding according to the invention are obtained by mixing base powders.

[0093] To produce the multi-layer sintered mouldings, the layered powder compositions listed in Tables 4 and 5 are compressed in a Weber press (program number 22; 100 MPa = 80 kN). The total charge per block was 40 g. The various layers are distributed in the following way, as described in Tables 6 and 7:

[0094] [Table 6]

[0095] [Table 7]

[0096] The green density of the pressed blank was 3.08 g / cm 3 It is.

[0097] The press blanks produced according to Tables 6 and 7 are subsequently freed from the binder. The debindering is carried out in a Thermo-STAR oven. The debindering or sinter-bonding of the blocks is carried out using the following debindering program (approximately 20 hours): Tmax=1040°C (see Table 8).

[0098] [Table 8]

[0099] The white body density of the green body is 3.17 g / cm 3 It was.

[0100] The Vickers hardness of the white body was measured using a Zwick hardness tester. Thus, the hardness of the upper and lower sides was determined by six measurements and averaging, respectively. (Test force 19.61 N, Load level HV2, Waiting time at load point 20 s): Vickers hardness HV2 (upper side): 55.3 Vickers hardness HV2 (bottom surface): 55.0 From the white body, two anterior crowns are milled and finally sintered, the crowns being first heated to 1450° C., then heated at that temperature for 2 hours and then cooled continuously to room temperature.

[0101] What is surprising in the sintered bodies according to the invention is especially the Vickers hardness: whereas in the sintered bodies not according to the invention the Vickers hardness of the pre-sintered blanks (white bodies) increases with increasing Fe2O3 content, in the sintered bodies according to the invention the Vickers hardness does not change over the whole block and remains at about 55 HV2.

[0102] In terms of aesthetics, the variant with a higher yttrium content at the tip (Table 8) shows a slightly higher translucency along the tip.

Claims

1. 1. A sintered molding with a color gradient for use in the manufacture of dental restorations, obtained by sintering a compression molding comprising two or more ceramic powder layers with different colors, Each powder layer is at least 80% by weight ZrO ２ and is essentially free of iron oxide; A sintered molding, wherein each powder layer has a different concentration of terbium oxide, erbium oxide, and cobalt oxide.

2. A sintered molding as described in claim 1, characterized in that each of the sintered powder layers undergoes essentially equal volume changes over a temperature range of 25 to 1600°C.

3. 2. The sintered molding of claim 1, wherein the weight ratio of terbium oxide to cobalt oxide is in the range of 80:1 to 5:1 in at least one powder layer.

4. A sintered molding as described in claim 1, characterized in that the sintered molding has layers with different colors and the sintering process results in a gradual color gradient.

5. 10. The sintered molding of claim 1, wherein the at least two powder layers have essentially the same yttria content.

6. A sintered molding as described in claim 1, characterized in that the sintered molding has a translucent gradient.

7. Each of the powder layers contains at least 0.02 wt. % Al ２ O ３ 2. The sintered molding of claim 1, characterized in that it has

8. At least one of the powder layers comprises Y ２ O ３ and / or Er ２ O ３ 2. The sintered molding according to claim 1, characterized in that it contains at least 3% by weight of

9. The powder layer is zirconia and / or HfO ２ 10. The sintered molding according to claim 1, wherein each of said powder layers contains at least 89% by weight of the components of said powder layer.

10. 10. The sintered molding of claim 1, wherein the compression molding comprises four or more powder layers.

11. 2. The sintered molding of claim 1, characterized in that the compression molding consists of five ceramic powder layers, the first powder layer comprising 20-30% of the total thickness of the stacked powder layers, the second powder layer comprising 10-20%, the third powder layer comprising 15-25%, the fourth powder layer comprising 10-20%, and the fifth powder layer comprising 20-30%, totaling 100% of the total thickness.

12. 10. The sintered molding of claim 1, wherein the pre-sintered ceramic molding is processed by a subtractive process.

13. 10. The sintered molding of claim 1, wherein the sintered molding exhibits a layer-by-layer increase in terbium oxide content.

14. 2. The sintered molding according to claim 1, wherein the sintered molding contains terbium oxide in an amount of 0.001 to 0.15% by weight in each powder layer.

15. 15. Use of a sinter moulding according to any one of claims 1 to 14 for a dental restoration or for producing a dental restoration.

16. 15. A method for producing a sintered molding with a color gradient according to any one of claims 1 to 14, comprising: a) providing two or three or four or five or more ceramic powder layers of different colors stacked on top of each other; b) pressing the stacked ceramic powder layers to form a compression molding; and c) sintering the molding obtained in step b) to form a ceramic molding, the ceramic powder layers each have a different composition; Each powder layer contains 80% by weight or more of ZrO ２ and is substantially free of iron oxide; 1. A method for producing a sintered molding, wherein each powder layer has a different concentration of terbium oxide, erbium oxide, and cobalt oxide.

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