A set of colored porous zirconium oxide dental milling blanks and production method

Abstract

The present invention relates to a set of porous zirconia dental mill blanks, the set comprising at least two differently colored porous zirconia dental mill blanks, the porous zirconia dental mill blanks comprising zirconium oxide, yttrium oxide, coloring ions and optionally aluminum oxide, comprising a plurality of layers with different yttrium oxide contents, having a bottom layer and a top layer, the contents of yttrium oxide and coloring ions in mol % varying in opposite directions from the bottom layer to the top layer, and the contents of yttrium oxide and coloring ions in mol % being adjusted to provide a substantially constant ratio of the sum of yttrium oxide and coloring ions in mol % between the top layer and the bottom layer of the at least two differently colored zirconia dental mill blanks. The invention also relates to a method for producing such a set.

Description

Technical Field

[0001] The invention relates to a set of porous zirconia dental mill blanks comprising at least two differently colored porous zirconia dental mill blanks, a method for producing such a set, a method for producing a dental restoration from such a set and a kit comprising such a set and a dental cement. Background Art

[0002] There is a continuing need for improved esthetic appearance of dental zirconia restorations, particularly monolithic dental zirconia restorations.

[0003] To make zirconium oxide materials more closely resemble the appearance of natural teeth, zirconium oxide with different levels of translucency can be used in one restoration to simulate the natural transition from dentin to enamel.

[0004] In this regard, various methods and materials have been proposed.

[0005] US 2016 / 0120765 A1 (Dang et al.) describes a dental product for producing dentures, the dental product comprising: a first layer, the first layer comprising a first weight percentage of yttrium oxide and zirconium oxide particles; a second layer, the second layer comprising a second weight percentage of yttrium oxide and zirconium oxide particles; and a third layer, the third layer comprising a third weight percentage of yttrium oxide and zirconium oxide particles, wherein: the first layer is located below the second layer and the third layer, the second layer is located between the first layer and the third layer, and at least one of the first layer, the second layer and the third layer comprises a certain weight percentage of pigment.

[0006] WO 2019 / 180766 A1 (Tosoh) relates to a zirconia sintered body having both translucency and high strength and a method for producing the same, wherein the zirconia sintered body can be produced by controlling the state of the raw material powder, for example, by using a first zirconia powder having an yttrium oxide content of 2 mol% to 4 mol% (including the end values) and a second zirconia powder having an yttrium oxide content greater than 4 mol% and less than or equal to 6 mol%, and the yttrium oxide content is greater than 3 mol% and less than or equal to 5.2 mol%.

[0007] US 2019 / 0380815 A1 (Aiba et al.) describes a dental zirconia blank having multiple layers, the multiple layers comprising: a first layer composed of a high magnetic permeability ceramic containing 91.6 mol% to 96.5 mol% of zirconium oxide and 3.5 mol% to 8.4 mol% of yttrium oxide and a second layer composed of a low magnetic permeability ceramic containing 95.6 mol% to 98.5 mol% of zirconium oxide and 1.5 mol% to 4.4 mol% of yttrium oxide, wherein the yttrium oxide content in the low magnetic permeability ceramic is 0.5 mol% to 5.4 mol% lower than the yttrium oxide content in the high magnetic permeability ceramic, and the first layer is located at one end of the multiple layers in the laying direction.

[0008] US 2018 / 0263863 A1 (Kim et al.) describes a method for enhancing the optical properties of a sintered zirconia ceramic body and provides a zirconia ceramic dental restoration. The method steps include: a) applying a first yttrium-containing composition to the surface of a pre-sintered or porous ceramic body; b) applying a second yttrium-containing composition to the pre-sintered or porous ceramic body; and c) sintering the ceramic body.

[0009] US 2019 / 0321146 A1 (Jung et al.) relates to a green zirconia dental blank having a chemical composition of increasing amounts of yttria throughout its thickness and pre-sintered optical properties that are substantially consistent and white in chromaticity across the thickness; and is milled, stained and sintered to form a denture having optical properties that, after sintering, reduce in chromaticity through the thickness of the denture.

[0010] US 2016 / 157971 A1 (Rothbrust et al.) describes a method comprising (a) providing at least a first oxide ceramic material and a second oxide ceramic material, wherein the first oxide ceramic material and the second oxide ceramic material differ in sintering properties; and (b) adjusting at least one of the oxide ceramic materials so that the sintering properties of the first oxide ceramic material are consistent with the sintering properties of the second oxide ceramic material.

[0011] US 2018 / 002235 A1 (Ito et al.) describes a partially stabilized zirconia sintered body comprising 4 mol% to 7 mol% of yttrium oxide as a stabilizer, wherein the zirconia sintered body comprises a shading material, the zirconia sintered body having a first region and a second region in which the content ratio of the shading material is higher than the content ratio of the first region, and the difference between the content ratio of yttrium oxide in the first region and the content ratio of yttrium oxide in the second region is less than 1 mol%.

[0012] US 10,238,473 (Jung et al.) describes a zirconia sintered body comprising: a) a sintered body comprising zirconia; b) the sintered body having a plurality of distinct regions, including at least one upper region and at least one lower region; c) the at least one upper region and the at least one lower region having different chemical compositions, wherein at least one region has a different strength than another region; and d) the sintered body having an inverse relationship of translucency and strength, the translucency increasing in one direction across the plurality of distinct regions, while the strength decreasing in the same direction across the plurality of distinct regions.

[0013] EP 3 108 849 A1 (3M) describes a porous multilayer colored zirconium oxide dental mill blank comprising a bottom layer B, a top layer E, at least one intermediate layer E x and at least one intermediate layer B x , wherein the layers are arranged in an alternating sequence and wherein the individual layers B, B x The thickness decreases from bottom to top, and the single layers E, E x The thickness decreases from top to bottom. Summary of the invention

[0014] Providing aesthetically pleasing dental restorations by laying down different zirconium oxide compositions having different yttria contents can be challenging.

[0015] Several factors must be considered, such as the difference in yttria content between the layers and the interaction of the yttria content of the layers with the coloring components.

[0016] Sometimes, interfaces between layers of differently doped materials appear opaque or produce other undesirable optical effects in the material. It is presumed that the observed effects are caused by too high a difference in yttrium oxide doping between the layers.

[0017] Higher doping of the coloring component will reduce the relative amount of yttrium oxide. In addition, the sum of yttrium oxide and the coloring component can be higher than the amount of yttrium oxide alone, but due to the darker color caused by the coloring component, the resulting translucency is generally lower rather than higher, despite the higher amount of dopant.

[0018] Manufacturers of dental mill blanks are therefore faced with the object of providing dental mill blanks which, after machining and sintering, result in dental restorations having the desired translucency for different tooth shades.

[0019] It is desirable that the translucency gradient be improved, ie clearly visible, and at the same time be as similar as possible for a wide range of tooth colours (eg from very light to very dark colours).

[0020] This is also valid for the strength of the material. Different amounts of additives (e.g., coloring ions and stabilizers) generally result in different strengths of the ceramic. Ideally, this difference would be predictable for a wide range of tooth colors (e.g., from very light to very dark colors).

[0021] However, different amounts of additives (such as coloring ions and stabilizers) present in dental mill blanks may have an influence on the sintering properties.Depending on the chemical composition in the blank, the ceramic may sometimes deform during the sintering process.

[0022] Therefore, there is a need for a set of dental mill blanks that produce aesthetically pleasing results, are reliable in terms of translucency and strength, can be easily produced and can be reliably sintered.

[0023] The invention described herein solves this object by providing a set of colored zirconium oxide dental mill blanks comprising a ratio of yttrium oxide and coloring ions. For the set of mill blanks having a wide range of tooth colors (e.g. from very light to very dark colors), this ratio is preferably as high and as constant as possible.

[0024] In one embodiment, the invention features a set of porous zirconia dental mill blanks comprising at least two differently colored porous zirconia dental mill blanks,

[0025] The porous zirconia dental milling blank

[0026] comprising zirconium oxide, yttrium oxide, coloring ions and optionally aluminum oxide,

[0027] comprising multiple layers having different yttrium oxide contents,

[0028] Having a bottom layer and a top layer,

[0029] The contents of yttrium oxide and coloring ions in mol % vary in opposite directions from the bottom layer to the top layer, and

[0030] The contents of yttrium oxide and coloring ions in mol % are adjusted to provide a substantially constant ratio of the sum of yttrium oxide and coloring ions in mol % between the top and bottom layers of the differently colored zirconium oxide dental mill blanks.

[0031] The invention also relates to a method for producing a set of porous zirconia dental mill blanks as described herein, the method comprising the following steps:

[0032] A powder composition of at least:

[0033] Zirconia powder ZP1 with yttria content Y1,

[0034] Zirconia powder ZP2 with yttria content Y2,

[0035] Zirconia powder ZP3 containing coloring ions CI-A,

[0036] Zirconia powder ZP4 containing coloring ions CI-B,

[0037] The yttrium oxide content Y2 in mol % is higher than the yttrium oxide content Y1;

[0038] Zirconia powders ZP1, ZP2, ZP3 and ZP4 were mixed in different mixing ratios to obtain at least

[0039] Zirconia powder composition ZP-MX-B,

[0040] Zirconia powder composition ZP-MX-I m ,

[0041] Zirconia powder composition ZP-MX-T,

[0042] The yttrium oxide content of the zirconium oxide powder composition in mole % is

[0043] ZP-MX-B <ZP-MX-I m <ZP-MX-T,

[0044] The number of intermediate layers is M≥1, where m=1, ..., M,

[0045] For each colored porous zirconium oxide dental mill blank of the set, a zirconium oxide powder composition was laid out in the cavity of the mold such that

[0046] The ZP-MX-B layer is located on one or more ZP-MX-I m Below the layer,

[0047] The one or more ZP-MX-I m The layer is located below the ZP-MX-T layer;

[0048] compacting the laid zirconium oxide powder composition;

[0049] The compacted zirconium oxide powder composition is optionally heat treated.

[0050] Another embodiment of the present invention also relates to a method for producing a dental restoration, the method comprising the following steps:

[0051] Providing a set of porous zirconia dental mill blanks as described herein;

[0052] selecting or choosing a porous zirconia dental milling blank from the group;

[0053] machining a porous dental restoration precursor from a porous zirconia dental milling blank;

[0054] The porous dental restoration precursor is sintered to obtain a dental restoration.

[0055] Furthermore, the invention relates to a kit comprising the set of porous zirconium oxide dental mill blanks and dental cement as described herein.

[0056] Unless otherwise defined, for the purposes of this specification, the following terms shall have the given meanings:

[0057] The term "dental article" refers to an article to be used in the dental or orthodontic field, in particular for the preparation or use as dental restorations, tooth models and parts thereof.

[0058] "Dental restoration" refers to a dental product used to restore defective tooth structure. A dental restoration typically has a three-dimensional inner and outer surface. The surface typically includes convex and concave structures. Compared to other products such as pottery or paving stones, dental restorations are small and finely crafted. The thickness of a dental restoration can vary from extremely thin, such as at the edges and margins (less than 0.1 mm), to quite thick, such as in the occlusal area (up to 8 mm or 16 mm). Portions of the crown portion in a bridge may have a thickness of up to 20 mm. The outer surface typically has an overall convex shape, while the inner surface typically has an overall concave shape.

[0059] The dental restorations described herein comprise or consist essentially of a polycrystalline ceramic material comprising yttrium-stabilized zirconia after sintering.

[0060] Examples of dental articles include crowns (including single crowns), bridges, inlays, onlays, veneers, facings, copings, crown and bridge frameworks, implants, abutments, orthodontic appliances (e.g., trays, buccal tubes, braces and buckles), monolithic dental restorations (i.e., restorations that do not require veneers), and components thereof.

[0061] The surfaces of teeth are not considered dental products.

[0062] Dental articles should not contain components that are harmful to the patient's health and therefore contain no hazardous and toxic components that could migrate out of the dental article.

[0063] By "dental mill blank" is meant a solid block of material (three-dimensional article) from which a dental article, dental workpiece, dental support structure or dental restoration can be and usually is processed by any subtractive process such as milling, grinding, drilling or the like.

[0064] A dental mill blank has a geometrically defined shape and comprises at least one flat surface. So-called "free-form surfaces" are not considered "geometrically defined". In this regard, the shape of the dental restoration itself (eg a crown or a bridge) is not considered a dental mill blank.

[0065] "Zirconium oxide article" shall mean a three-dimensional article wherein at least one of the x, y, z dimensions is at least about 5 mm, the article comprising at least 80 wt%, or at least 90 wt%, or at least 95 wt% zirconium oxide.

[0066] "Ceramic" refers to an inorganic, non-metallic material prepared by the application of heat. Ceramics are generally hard, porous, and brittle, and, unlike glass or glass-ceramics, exhibit an essentially completely crystalline structure.

[0067] "Crystalline" means a solid comprising atoms arranged in a periodic pattern in three dimensions (ie, having a long range crystal structure as determined by X-ray diffraction). Crystal structures include tetragonal, monoclinic, cubic zirconia, and mixtures thereof.

[0068] A "monolithic dental restoration" shall mean a dental ceramic article that has no facings or veneers attached to its surface. That is, a monolithic dental restoration consists essentially of only one material composition. However, a thin layer of glaze may be applied if desired.

[0069] "Glass" means an inorganic, non-metallic, amorphous material that is thermodynamically supercooled and freeze-thawed. Glass refers to a hard, brittle, transparent solid. Typical examples include soda-lime glass and borosilicate glass. Glass is an inorganic product of a melt that has been cooled to a rigid state without crystallization. Most glasses contain silicon dioxide as their main component and certain amounts of glass formers and modifiers.

[0070] The porous ceramic dental materials described herein do not contain glass.

[0071] "Glass ceramic" means an inorganic non-metallic material in which one or more crystalline phases are surrounded by a glass phase, so that the material includes a glass material and a ceramic material in a composite or mixed state. It is formed into glass and then partially crystallized by heat treatment. Glass ceramics may refer to a mixture of lithium oxide, silicon oxide, and aluminum oxide.

[0072] The porous dental materials described herein do not comprise glass ceramics.

[0073] "Powder" means a dry, mass of fine particles comprising a mass of particles which flow freely when vibrated or tilted.

[0074] "Particle" means a solid substance having a geometrically determinable shape. The shape may be regular or irregular. Particles can often be analyzed with respect to, for example, size and size distribution.

[0075] Density refers to the ratio of an object's mass to its volume. Density is usually expressed in g / cm 3The density of an object can be calculated, for example, by determining its volume (eg, by calculation or application of Archimedean principle or method) and measuring its mass.

[0076] The volume of the sample can be determined based on the overall outer dimensions of the sample. The density of the sample can be calculated from the measured sample volume and the sample mass. The total volume of the ceramic material can be calculated from the mass of the sample and the density of the material used. The total volume of the pores in the sample is assumed to be the remainder of the sample volume (100% minus the total volume of the material).

[0077] In the field of ceramic technology, "porous material" refers to a material comprising a partial space formed by pores, pores or holes. Accordingly, the "open pore" structure of the material is sometimes referred to as an "open porous" structure, and the "closed pore" material structure is sometimes referred to as a "closed porous" structure. In addition, it can be found that "pores" are sometimes used instead of the term "hole" in the art. For different porosities measured according to DIN 66133 at different material samples (for example, using mercury "Poremaster 60-GT" from Quantachrome Inc., USA), the material structure classifications "open pore" and "closed pore" can be determined. Materials with open pores or open porous structures can be passed through by, for example, gases.

[0078] Typical values ​​for "open cell" materials are between 15% and 75%, or between 18% and 75%, or between 30% and 70%, or between 34% and 67%, or between 40% and 68%, or between 42% and 67%. The term "closed cell" relates to "closed porosity". Closed cells are those pores that are not accessible from the outside and that cannot be entered by gases under ambient conditions.

[0079] "Average connected pore size" means the average size of the pores of the open pores of a material. The average connected pore size can be calculated as described in the Examples section.

[0080] "Calcination" refers to the process of heating a solid material to drive off at least 90% by weight of volatile chemically bound components (e.g., organic components) (as opposed to, for example, drying, where physically bound water is driven off by heating). Calcination is carried out at a temperature lower than that required to carry out the pre-sintering step.

[0081] The terms "sintering" or "firing" are used interchangeably. The pre-sintered ceramic article shrinks during the sintering step (i.e., if sufficient temperature is applied). The sintering temperature applied depends on the ceramic material selected. For zirconia-based ceramics, typical sintering temperatures range from 1,100°C to 1,600°C. Sintering generally involves densifying a porous material into a less porous material (or a material with fewer small pores) with a higher density, and in some cases, sintering may also include a change in the phase composition of the material (e.g., a partial transformation of an amorphous phase to a crystalline phase).

[0082] "Fluorescent agent" shall mean an agent that shows or provides fluorescence in the region of visible light (380 nm to 780 nm).

[0083] By "machining" is meant the milling, grinding, cutting, carving or shaping of a material by a machine. Milling is generally faster and less expensive than grinding. A "machinable article" is an article that has a three-dimensional shape and is strong enough to be machined.

[0084] "Environmental conditions" refers to the conditions to which the solutions of the present invention are usually subjected during storage and handling. Environmental conditions may be, for example, a pressure of 900 mbar to 1,100 mbar, a temperature of 10° C. to 40° C., and a relative humidity of 10% to 100%. In the laboratory, the environmental conditions are adjusted to 20° C. to 25° C. and 1,000 mbar to 1,025 mbar (at sea level).

[0085] A composition is "substantially or substantially free of" a certain component if the composition does not contain the component as an essential feature. Thus, the component is not arbitrarily added to the composition or is not arbitrarily combined with other components or ingredients of other components. A composition that is substantially free of a certain component generally does not contain the component at all. However, the presence of a small amount of the component is sometimes unavoidable, for example due to impurities contained in the raw materials used.

[0086] As used herein, "a", "an", "the", "at least one", and "one or more" are used interchangeably.

[0087] The terms "comprising" or "containing" and variations thereof do not have a limiting meaning when these terms appear in the specification and claims. "Consisting essentially of means that certain additional components may be present, i.e., those components that do not materially affect the basic characteristics of the article or composition. "Consisting of means that no additional components should be present. The term "comprising" shall also include the terms "consisting essentially of" and "consisting of."

[0088] The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0089] Adding the plural form "(s)" to a term means that the term should include both the singular and the plural. For example, the term "additive" means one additive and multiple additives (eg, 2, 3, 4, etc.).

[0090] Unless otherwise indicated, all numbers expressing quantities of ingredients, measurements of physical properties such as described below, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." BRIEF DESCRIPTION OF THE DRAWINGS

[0091] Figure 1 A multi-layered dental mill blank with color and translucency gradients is schematically shown. DETAILED DESCRIPTION

[0092] The invention described herein is advantageous for a number of reasons:

[0093] Since the porous dental mill blank comprises multiple layers with different yttria contents, the dental mill blank or a dental article machined therefrom will show a translucency gradient after sintering.

[0094] Furthermore, since the amounts of yttrium oxide and coloring ions vary in opposite directions from the bottom layer to the top layer, the dental mill blank or the dental article machined therefrom will show a color gradient after sintering.

[0095] The translucency and / or color gradient obtained after sintering closely resembles the translucency and color gradient of natural teeth.

[0096] Furthermore, since the ratio of yttria and the sum of coloring ions between the top and bottom layers is substantially constant for the set of dental mill blanks, differently colored zirconium oxide mill blanks can be sintered under substantially the same conditions, reducing the risk of discoloration and / or deformation.

[0097] It was found that by using a specific molar ratio of yttrium oxide and the coloring component, a higher stability of the total dopant dosage across different shades (from very light to very dark) can be achieved. Thus, the strength and reliability of the translucent gradient can be improved for a wide range of tooth colors (from very light to very dark).

[0098] The present invention relates to a set of porous zirconium oxide dental mill blanks.

[0099] The set comprises at least two differently colored zirconium oxide dental mill blanks. The set may comprise at least 3, 4, 5, 6, 7, 8, 9, 10, 15, 16 or 17 differently colored zirconium oxide dental mill blanks.

[0100] Different colors mean that individual zirconium oxide dental mill blanks can be distinguished from one another by the color obtained after having undergone a sintering process.

[0101] The porous zirconium oxide dental mill blank has a bottom layer and a top layer. The bottom layer and the top layer correspond to individual layers. If there are more than two layers, the additional layers are referred to as intermediate layers.

[0102] The porous zirconium oxide dental mill blank comprises a plurality of layers with different yttria contents.

[0103] The porous zirconia dental mill blank typically comprises at least 3 or 4 or 5 layers. Typically, the porous zirconia dental mill blank comprises 3 to 8 layers or 4 to 7 layers.

[0104] The thickness of a single layer of porous zirconium oxide dental mill blank is typically in the range of 2 mm to 12 mm or 2 mm to 10 mm or 2 mm to 8 mm.

[0105] The thickness of the layers of the porous zirconium oxide dental mill blank can be the same or different.

[0106] According to one embodiment, the bottom layer (body area) of the porous zirconia dental mill blank is thicker than the top layer (enamel area). Such an arrangement may help to improve the aesthetic effect even further.

[0107] According to one embodiment, the thicknesses of the individual layers are as follows: bottom layer > top layer > middle layer.

[0108] An example of a dental mill blank with 6 layers is shown in Figure 1 The values ​​given are the layer heights in mm in the presintered compact.

[0109] The dental mill blank shows a color gradient from the bottom layer to the top layer. The numbers given describe the layer thickness in mm (left: powder height in the mold before pressing the zirconium oxide powder; right: estimated layer height after pressing the zirconium oxide powder).

[0110] The difference in yttrium oxide concentration between adjacent layers generally does not exceed 0.5 mol %, and is preferably in the range of 0.35 mol % to 0.5 mol %.

[0111] This may be advantageous because on the one hand the difference is high enough to obtain a measurable translucency gradient and on the other hand the difference is low enough to reduce the risk of deformation during sintering.

[0112] Furthermore, if the yttrium oxide concentration difference between adjacent layers is not too high, opaque optical effects at the layer interfaces can be avoided.

[0113] The amount of yttria and the amount of coloring ions (given in mol %) vary in opposite directions from the bottom layer to the top layer of the porous zirconia dental mill blank.

[0114] According to one embodiment, the amount of yttrium oxide in the bottom layer is lower than that in the top layer, and the amount of coloring ions in the bottom layer is higher than that in the top layer.

[0115] Thus, after sintering, the dental mill blank or the dental article machined therefrom exhibits translucency and / or a color gradient.

[0116] The amounts of yttrium oxide and coloring ions are adjusted to provide a substantially constant dopant ratio between the top and bottom layers of the dental mill blanks contained in the set.

[0117] More precisely, the ratio of the sum of yttrium oxide and coloring ions in mol % between the top layer and the bottom layer of the porous zirconium oxide dental mill blank is substantially constant for the different colours of the dental mill blanks.

[0118] Essentially constant means that the ratio of the sum of yttrium oxide and coloring ions in mol % between the top and bottom layers of the porous zirconium oxide dental mill blank varies with a deviation D which is not greater than 2.70 for all colored mill blanks of the set.

[0119] By using formula (1), the deviation D of each color can be calculated from the above ratio R.

[0120] D n =((R max -R n ) / R max *100) / R max 2 (1)

[0121] The blank group contains N colors, where N≥2, n=1, 2, ..., N.

[0122] R = (amount of yttrium oxide + colored oxide in the top layer, in mol %) / (amount of yttrium oxide + colored oxide in the bottom layer, in mol %). max is the highest ratio found for the color composition within the group. Typically, the highest ratio is found for the lightest color of the group.

[0123] Depending on the amount of yttrium oxide present in the dental mill blank, the ratio of the amount of yttrium oxide in mol % plus the amount of coloring ions in mol % in the top layer divided by the amount of yttrium oxide in mol % plus the amount of coloring ions in mol % in the bottom layer will vary.

[0124] For example, for porous zirconia dental mill blanks having a gradient of yttria from 3.0 mol % to 5.5 mol % from the bottom layer to the top layer, for darker colors, especially for progressively darker colors, the ratio is typically 1.83 or lower, preferably in the range of 1.83 to 1.67.

[0125] For porous zirconia dental mill blanks having a gradient of yttria from 4.0 mol % to 5.5 mol % from the bottom layer to the top layer, for darker colors, especially for progressively darker colors, the ratio is typically 1.37 or lower, preferably in the range of 1.37 to 1.31.

[0126] For porous zirconia dental mill blanks having a gradient of yttria from 3.0 mol % to 5.0 mol % from the bottom layer to the top layer, for darker colors, especially for progressively darker colors, the ratio is typically 1.66 or lower, preferably in the range of 1.66 to 1.54.

[0127] For porous zirconia dental mill blanks having a gradient of 4.0 mol % to 5.0 mol % yttria from bottom layer to top layer, for darker colors, especially for progressively darker colors, the ratio is typically 1.25 or less, preferably in the range of 1.25 to 1.20.

[0128] For porous zirconia dental mill blanks having a gradient of yttria from 3.2 mol % to 5.65 mol % from the bottom layer to the top layer, for darker colors, especially for progressively darker colors, the ratio is typically 1.76 or lower, preferably in the range of 1.76 to 1.62.

[0129] These differences are explained by formula (1). n and R max A simple way to express the deviation between max -R n ) / R max *100, which is the deviation in percent. By dividing this term by R max 2 , the results are normalized and become valid for many different yttria gradients, while the deviations from the simpler calculations will vary with the yttria gradient or R, respectively. max increases with the increase of value.

[0130] It must also be considered that if the set of dental mill blanks contains very light colors and the doping with coloring ions is low, then the R given above max value is applicable. If this is not the case, then R max The values ​​can be lower even if the yttria gradient is relatively high.

[0131] The porous zirconia dental mill blanks described herein comprise, consist essentially of, or consist of zirconium oxide, yttrium oxide and coloring ions and optionally fluorescent components and / or aluminum oxide.

[0132] The layers of porous zirconia dental mill blanks contain varying amounts of yttria, typically an amount of yttria of 2.8 mol % to 7.0 mol % or 3.0 mol % to 5.5 mol %.

[0133] The layers of the porous zirconia dental mill blanks of the set of mill blanks described herein also contain coloring ions, in particular Er and at least one further coloring ion selected from Fe, Tb, V, Mn, Cr, Co.

[0134] Optionally, alumina may be present. If present, alumina is typically present in an amount of at most 0.15 mol % or at most 0.1 mol % or at most 0.05 mol % relative to the material of the porous zirconia dental mill blank.

[0135] If desired, the porous dental zirconia mill blank may also contain a fluorescent agent, in particular a Bi component. If a Bi component is present, the presence of a Fe component should be avoided.

[0136] If present, the Bi component (calculated as Bi2O3) is typically present in an amount of at most 0.04 mol% or at most 0.03 mol% or at most 0.02 mol% relative to the material of the porous zirconia dental mill blank.

[0137] Without wishing to be bound by a certain theory, it is believed that by using Fe as a colorant, either the UV light required to induce fluorescence or the emitted blue fluorescence itself may be absorbed by the Fe component, or even both and thus the desired visual appearance is lost.

[0138] The porous zirconia dental mill blanks of the group of dental mill blanks described herein typically comprise or consist essentially of 89.35 to 97.18 mol % of ZrO2, 0 to 3 mol % of HfO2, 2.8 to 7.0 mol % of Y2O3, 0 to 0.15 mol % of Al2O3, an amount of 0.02 to 0.5 mol % of coloring ions calculated as their respective oxides, the mol % being calculated relative to the chemical composition of the porous zirconia dental mill blank, the coloring ions being Er and at least one other ion selected from Fe, Tb, V, Mn, Cr, Co.

[0139] The amount of yttrium oxide of 2.8 mol % to 7.0 mol % refers to each individual layer of a single block, provided that the block has the yttrium oxide gradient described herein.

[0140] Porous zirconia dental mill blanks can generally be characterized by the following parameters alone or in combination:

[0141] a) Average primary particle size: less than 900 nm, or less than 800 nm, or less than 600 nm;

[0142] b) Average connection pore diameter: 10nm to 200nm;

[0143] c) BET surface: 2m 2 / g to 20m 2 / g or 5m 2 / g to 16m 2 / g or 7m 2 / g to 14m2 / g;

[0144] d) Biaxial flexural strength: 8 MPa to 80 MPa, or 15 MPa to 55 MPa;

[0145] e) Vickers hardness: 25 (HV 0.5) to 150 (HV 0.5) or 35 (HV 1) to 140 (HV 1).

[0146] According to one embodiment, the porous zirconia dental mill blank may be characterized by the following features alone or in combination:

[0147] a) Average primary particle size: less than 800 nm;

[0148] b) Average connection pore diameter: 10nm to 200nm;

[0149] c) BET surface: 2m 2 / g to 20m 2 / g;

[0150] d) Biaxial flexural strength: 8MPa to 80MPa;

[0151] e) Vickers hardness: 25 (HV 0.5) to 150 (HV 0.5).

[0152] According to another embodiment, the porous zirconia dental mill blank may be characterized by the following features alone or in combination:

[0153] a) Average primary particle size: less than 600 nm;

[0154] b) Average connection pore diameter: 10nm to 200nm;

[0155] c) BET surface: 7m 2 / g to 14m 2 / g;

[0156] d) Biaxial flexural strength: 15MPa to 55MPa;

[0157] e) Vickers hardness: 35 (HV 1) to 140 (HV 1).

[0158] If desired, individual properties can be determined as described in the Examples section.

[0159] A combination of parameters a) and b); or a) and c); or a) and d); or a), c) and d) may sometimes be preferred.

[0160] It was found that for certain properties it may be beneficial for the porous zirconia material to have a certain BET surface. The BET surface should be within a specific range. It should not be too small and it should not be too large.

[0161] If the BET surface of a material is too low, then its sintering activity may not be sufficient to reach or approach theoretical density during an accelerated sintering cycle, which will negatively affect material strength and translucency.

[0162] If the BET surface of the material is too high, it may be difficult to adequately control the sintering properties. In this case, it may also be difficult to obtain a material with the desired strength and translucency.

[0163] The Vickers hardness of the material is also usually within a specific range.

[0164] If the Vickers hardness of the material is too low, the machinability may be reduced in quality (edge ​​chipping or workpiece breakage) or similar difficulties may arise with manual remachining for individualizing the framework of a dental restoration or monolithic restoration.

[0165] If the Vickers hardness of the material is too high, the wear of the machining tools will increase to an uneconomical level, or the tool will break and damage the workpiece.

[0166] The biaxial flexural strength of a material is usually within a specific range.

[0167] It has been found that if the biaxial flexural strength of a material is too low, the material tends to break during the milling process or during manual machining by a dental technician.

[0168] On the other hand, if the biaxial flexural strength of the material is too high, machining the material by milling machines is often impossible with reasonable effort. The milling tool or the milled material often tends to chip or crack. In this case, the material must be formed by, for example, using Cerec TM The grinding was performed using a grinding machine (Sirona).

[0169] It was found that the porous dental materials having the above characteristics generally exhibited better machinability and faster sinterability compared to other commercially available dental mill blanks, while maintaining good translucency and strength.

[0170] Thus, the porous zirconia material of the porous dental zirconia mill blanks described herein may have a unique combination of features that facilitate the reliable production of highly aesthetic dental ceramic articles.

[0171] The porous zirconia dental mill blank may also be characterized by its shape and / or size.

[0172] The porous zirconia dental mill blank has a shape that enables the dental mill blank to be reversibly attached or fixed to a machining device. Suitable shapes include a disc or a block (eg a cube, a cuboid, a cylinder, etc.).

[0173] For cubic or cuboid shaped dental mill blanks typical dimensions are at least 19 mm in 2 dimensions and at least 12 mm in the third dimension.

[0174] Alternatively, the dental mill blank having a block shape may have the following dimensions: x dimension: 12 mm to 45 mm or 19 mm to 40 mm; y dimension: 12 mm to 70 mm or 19 mm to 60 mm; z dimension: 10 mm to 40 mm or 12 mm to 25 mm.

[0175] Typical dimensions for cylindrical or disc-shaped dental mill blanks are a diameter of more than 19 mm and a height of more than 12 mm.

[0176] Alternatively, the dental mill blank having the shape of a disk may have the following dimensions: x-dimension, y-dimension: 90 mm to 110 mm or 95 mm to 105 mm; z-dimension: 10 mm to 35 mm or 12 mm to 30 mm.

[0177] The dental mill blank may further comprise means for attaching the dental mill blank to a machining device. Suitable means include frames, recesses, stubs, mandrels and combinations thereof.

[0178] Fixing of dental mill blanks to such devices can be achieved by clamping, gluing, screwing and combinations thereof.Using such devices can facilitate the preparation of dental restorations with machining equipment.

[0179] Examples of fixing devices or arrangements are described in, for example, US 8,141,217 B2 (Gubler et al.), WO 02 / 45614 A1 (ETH Zurich), DE 203 16004 U1 (Stuehrenberg), US 7,985,119 B2 (Basler et al.) or WO 01 / 13862 (3M). The contents of these documents with respect to the description of the fixing device are incorporated herein by reference.

[0180] The invention also relates to a method for producing the set of porous dental zirconium oxide milling blanks.

[0181] Typically, a porous zirconia material for a dental mill blank can be obtained by a method comprising the following steps:

[0182] Mixing powders of different compositions to obtain a powder mixture,

[0183] Compress the powder mixture,

[0184] and optionally heat treating the pressed powder mixture.

[0185] The individual powders can be obtained by a process comprising the following steps:

[0186] treating the zirconium oxide powder with a solution containing coloring ions, in particular Er ions and other ions selected from Fe, Tb, V, Mn, Cr and / or Co;

[0187] The mixture was dried to obtain a powder.

[0188] Alternatively, the individual powders may be obtained by a process comprising the steps of:

[0189] Treating zirconium oxide powder with a powder containing coloring oxides, in particular a powder containing Er oxide and other oxides of Fe, Tb, V, Mn, Cr and / or Co;

[0190] Milling of wet mixture,

[0191] The mixture is (spray) dried to obtain a powder.

[0192] Suitable zirconium oxide powders are commercially available from various sources including Tosoh Company, Japan.

[0193] The mixing of the separate powders can be achieved by shaking the powders or placing the powders in a milling machine (eg, ball mill, agitator ball mill) and milling the powders until a homogeneous powder mixture is obtained. Other suitable mixing equipment may include sieves or granulators.

[0194] To facilitate the pressing or compacting step, a pressing aid may be added as desired.

[0195] Suitable compression aids include binders, lubricity additives, and mixtures thereof.

[0196] If necessary, such additives may be added to the zirconium oxide powder which is the main component of the powder mixture.

[0197] The powder mixture is then placed into a mold (layer by layer) and pressed into the shape of a dental mill blank.

[0198] The pressure to be applied is typically in the range of 150 MPa to 300 MPa. Alternatively, the applied pressure is set so that the pressed ceramic body reaches a certain density, for example, 2.8 g / cm in the case of zirconia ceramics. 3 Up to 3.5g / cm 3 density.

[0199] In a further step, the compacted composition is generally subjected to a heat treatment in order to obtain a porous dental mill blank. During this step, the organic compounds (eg binder components) are removed (generally referred to as calcination).

[0200] The temperature of the heat treatment is generally in the range of 800° C. to 1,100° C. or 900° C. to 1,000° C. The heat treatment is generally performed for a duration of 10 hours to 70 hours or 15 hours to 60 hours.

[0201] The article obtained after heat treatment can be machined or cut into any desired shape.

[0202] More specifically, the porous zirconia dental mill blanks of the set described herein can be produced by a method comprising the following steps:

[0203] A powder composition of at least:

[0204] Zirconia powder ZP1 with yttria content Y1,

[0205] Zirconia powder ZP2 with yttria content Y2,

[0206] Zirconia powder ZP3 containing coloring ions CI-A,

[0207] Zirconia powder ZP4 containing coloring ions CI-B,

[0208] The yttrium oxide content Y2 in mol % is higher than the yttrium oxide content Y1;

[0209] Zirconia powders ZP1, ZP2, ZP3 and ZP4 were mixed in different mixing ratios to obtain at least

[0210] Zirconia powder composition ZP-MX-B,

[0211] Zirconia powder composition ZP-MX-I m ,

[0212] Zirconia powder composition ZP-MX-T,

[0213] The yttrium oxide content of the zirconium oxide powder composition in mole % is

[0214] ZP-MX-B <ZP-MX-I m <ZP-MX-T,

[0215] The number of intermediate layers is M≥1, where m=1, ..., M,

[0216] For each colored porous zirconium oxide dental mill blank of the set, a zirconium oxide powder composition was laid out in the cavity of the mold such that

[0217] The ZP-MX-B layer is located below the ZP-MX-I m layer,

[0218] The ZP-MX-I m layer is located below the ZP-MX-T layer;

[0219] Compacting the laid zirconia powder composition;

[0220] Optionally heat-treating the compacted zirconia powder composition.

[0221] According to one embodiment, the layer thickness of the zirconia powder composition layer is as follows: ZP-MX-B > ZP-MX-I m < ZP-MX-T, where generally ZP-MX-B > ZP-MX-T.

[0222] According to one embodiment, the group of porous zirconia dental milling blanks described herein includes at least two differently colored porous zirconia dental milling blanks,

[0223] The porous zirconia dental milling blank

[0224] comprises zirconia, yttria, coloring ions and optionally alumina,

[0225] These coloring ions are selected from Er and at least one other ion selected from Fe, Tb, V, Mn, Cr, Co;

[0226] Comprises 3 to 7 layers,

[0227] The first layer is called the bottom layer and the last layer is called the top layer;

[0228] The bottom layer is thicker than the top layer;

[0229] Each layer has a different yttria content;

[0230] Relative to the material of the porous zirconia dental milling blank, the yttria content is in the range of 2.8 mol% to 7.0 mol%;

[0231] The difference in yttria content between layers does not exceed 0.5 mol%;

[0232] The contents of yttria and coloring ions in mol% vary in opposite directions from the bottom layer to the top layer;

[0233] Deviation D, calculated from the ratio R of the sum in mol% of yttria and coloring ions between the top layer and the bottom layer using the following formula

[0234] D n = ((R max - R n ) / R max * 100) / Rmax 2 ,

[0235] For all differently colored porous zirconia dental milling blanks in a group containing N (N≥2, n=1, 2, ..., N) different colors, it shall not exceed 2.70, where R max is the highest rate found within this group.

[0236] The invention also relates to a method for producing a dental restoration from a porous zirconia dental mill blank of the set of dental mill blanks described herein.

[0237] Such methods typically include the following steps:

[0238] Providing a set of porous zirconia dental mill blanks as described herein;

[0239] optionally determining the tooth color of the tooth to be restored;

[0240] selecting a porous zirconia dental milling blank from the group;

[0241] machining a porous dental restoration precursor from a porous zirconia dental milling blank;

[0242] The porous dental restoration precursor is sintered.

[0243] The step of selecting or choosing a porous zirconia dental mill blank is not particularly limited. Any porous zirconia dental mill blank of the group can be selected. Typically, the professional will select a porous zirconia dental mill blank from the group that is best suited to match the tooth color of the tooth to be restored after sintering.

[0244] If desired, tooth color can be determined using commercially available shade guides (eg, from Vita Corporation).

[0245] Typically, the machining step is accomplished using or by using milling or grinding equipment. These devices are available from Roland (DWX milling machine) or Sirona (CEREC TM inLab CAD / CAM) and others.

[0246] The machining step may be performed using milling, drilling, cutting, engraving or grinding devices.

[0247] Available milling parameters include: rotation speed of the milling tool: 5,000 rpm to 40,000 rpm; feed rate: 20 mm / min to 5,000 mm / min; milling cutter diameter: 0.8 mm to 4 mm.

[0248] If necessary, the machined porous dental zirconia restoration is cleaned, for example by removing milling dust with pressurized air.

[0249] The method of producing a dental restoration comprises a sintering step.

[0250] Sintering results in the formation of a zirconium oxide dental article, sometimes referred to as a crystalline metal oxide article.

[0251] If performed, this should be done in a manner that results in a dental ceramic article with an acceptable tooth-like color (e.g., conforming to Vita TM The firing or sintering step is completed under conditions of Classical color system).

[0252] Useful sintering conditions can generally be characterized by the following parameters, either alone or in combination:

[0253] Temperature: 1,100°C to 1,600°C, or 1,100°C to 1,500°C, or 1,100°C to 1,450°C, or 1,100°C to 1,300°C, or 1,300°C to 1,600°C, or 1,400°C to 1,580°C, or 1,450°C to 1,580°C;

[0254] Atmospheric environment: air;

[0255] Duration: until the density reaches at least 98% or 99% to 100% of the theoretically achievable density of the material;

[0256] Holding time: 0h to 24h or 0.1h to 5h;

[0257] Pressure: Environmental pressure.

[0258] According to one embodiment, the sintering conditions are characterized as follows: temperature: 1,100°C to 1,600°C; atmosphere: air; duration: until the density reaches at least 98% of the theoretically achievable density of the material; dwell time: 0h to 24h.

[0259] During the firing process, the porous dental article is sintered into its final shape, thereby changing in size, density, hardness, flexural strength and / or grain size.

[0260] The holding time is the duration during which the product is kept at the maximum sintering temperature. The holding time may be zero. However, the holding time may also be in the range of 0 h to 24 h or 0.1 h to 5 h.

[0261] However, sintering temperature and dwell time are usually related. Higher temperatures usually require shorter dwell times.

[0262] Therefore, the dwell time may last from 0 h to 5 h (for example, if the firing temperature is 1,550° C.) or from 0.1 h to 24 h (for example, if the firing temperature is 1,100° C.).

[0263] In general, the sintering or firing conditions are adjusted so that the density of the sintered dental ceramic article is equal to or greater than 98% compared to the theoretically achievable density.

[0264] If faster processing is desired, higher heating rates may be used.

[0265] In general, useful heat treatment conditions for so-called accelerated or fast sintering can be characterized by the following features, either alone or in combination:

[0266] a) Heating rate: 1.5°C / sec to 7°C / sec, or 2°C / sec to 7°C / sec, or 3°C / sec to 7°C / sec;

[0267] b) sintering temperature: at least 1,400° C., at least 1,450° C., or at least 1,500° C.;

[0268] c) Atmospheric environment: air;

[0269] d) Duration: less than 60 minutes;

[0270] e) Holding time: 0 to 10 minutes;

[0271] f) Pressure: environmental pressure.

[0272] According to one embodiment, suitable heat treatment conditions are characterized by the following features, alone or in combination:

[0273] a) Heating rate: 2°C / sec to 7°C / sec;

[0274] b) Sintering temperature: at least 1,500°C;

[0275] c) Atmospheric environment: air;

[0276] d) Duration: less than 60 minutes;

[0277] e) Holding time: 0 to 10 minutes;

[0278] f) Pressure: environmental pressure.

[0279] Combinations of the following features are sometimes preferred: a) and b); a), b) and d); a), b), c), d) and e).

[0280] Ovens that can be used in the methods described herein are available from Dentsply Sirona, SpeedFire TM ) were purchased commercially.

[0281] A suitable heating furnace is also described in WO 2017 / 144644 ​​A1 (Sirona). The heating furnace is used to perform heat treatment of dental replacement parts and comprises an induction coil, a radiant heater, an insulating layer and a heating furnace chamber. In addition, the heating furnace has a cooling system to control the internal temperature of the heating furnace chamber.

[0282] Alternatively, for the above-mentioned rapid thermal treatment process using a high heating rate, the sintering process may also be performed by using a lower heating rate.

[0283] The corresponding sintering scheme can be characterized as follows: heating rate: 1°C / min to 60°C / min; sintering temperature: 1,100°C to 1,600°C; duration: 60 min to 480 min.

[0284] A heating furnace that can be used is the commercially available Lava TM Furnace 200 (3M OralCare).

[0285] Also described are dental restoration precursors obtained or obtainable (eg by applying a machining step) from a porous zirconia milling blank of the set described herein.

[0286] Such dental restoration precursors or dental restorations subsequently obtained by sintering such dental restoration precursors typically have the shape of an inlay, onlay, veneer, covering, coping, crown, bridge, implant, abutment, orthodontic appliance or a part thereof.

[0287] Also described is a dental restoration obtained or obtainable by sintering a dental restoration precursor.

[0288] Such dental restorations are generally characterized by the following features, either alone or in combination:

[0289] Density: 5.8g / cm 3 Up to 6.1g / cm 3 ;

[0290] Translucency: at least 30%, measured in reflection mode, averaged over a wavelength between 400 nm and 700 nm, determined on a sample having a thickness of 1 mm and cut from the top layer of a dental zirconium oxide milling blank;

[0291] Translucency: at least 15%, measured in reflection mode, averaged over a wavelength between 400 nm and 700 nm, determined on samples having a thickness of 1 mm and cut from the bottom layer of a dental zirconium oxide milling blank.

[0292] If desired, sintered samples of dental mill blanks may also be characterized by additional parameters such as biaxial flexural strength and crystalline phase content.

[0293] Biaxial flexural strength is typically in the range of 500 MPa to 2,000 MPa.

[0294] The crystalline phase content is generally 30 to 80% by weight for the tetragonal phase and 20 to 70% by weight for the cubic phase.

[0295] The present invention also relates to a kit, which comprises the set of porous zirconium oxide dental milling blanks and dental cement as described herein.

[0296] Dental cements are used to attach or secure dental restorations machined from dental mill blanks to tooth surfaces.

[0297] Suitable dental cements include resin modified glass ionomer cements (RM-GIZ), and self-adhesive resin cements.

[0298] RM-GIZ cements typically contain an acid-reactive filler (such as fluoroaluminosilicate glass), water, optionally a polyacid, a polymerizable component (such as a (meth)acrylate component), and an initiator system.

[0299] Self-adhesive resin cements generally contain an acidic polymerizable component (eg, a (meth)acrylate component bearing a phosphoric acid or carboxylic acid moiety), a polymerizable component not containing an acidic moiety, an initiator system, and a filler.

[0300] Suitable dental cements are also commercially available, such as RelyX TM Unicem 2 or RelyX TM Luting Plus (3M Oral Care).

[0301] The kit box described herein may further include the following components alone or in combination: instruction manual; sintering heating furnace.

[0302] The instructions generally contain information as described herein regarding the machining process and the parameters to be applied and the sintering conditions that can be used to sinter the machined article to final density.

[0303] The sintering heating furnace may be a heating furnace for performing a conventional sintering process or a heating furnace for performing an accelerated sintering process.

[0304] Sintering equipment as described herein may be used.Sintering furnaces are also commercially available, for example from 3M Oral Care, Dentsply Sirona or Ivocar.

[0305] All components used to produce the dental zirconia mill blanks described herein should be sufficiently biocompatible, ie the material of the dental zirconia mill blank should not produce a toxic, damaging or immune response in living tissue.

[0306] The dental articles described herein generally do not contain components or additives that would compromise the intended purpose of the invention. Thus, components or additives in amounts that would ultimately result in a non-tooth-colored dental article are generally not included in the dental article. Generally, if it is not known from Vita TM Color coding systems assign a color to the article, characterizing the article as not tooth-colored. Additionally, components that would reduce the mechanical strength of the dental restoration to the point where mechanical failure might occur are also often not included in dental articles.

[0307] Furthermore, the production of zirconia dental mill blanks or dental articles obtained therefrom generally does not require the application of a hot isostatic pressing step (HIP).

[0308] More precisely, the dental mill blanks of the group described herein generally do not contain the following components, alone or in combination: glass in an amount of more than 1 wt.-%; glass ceramic in an amount of more than 1 wt.-%; Ca or Mg as stabilizers in an amount of more than 1 wt.-%; fluoride in an amount of more than 0.1 wt.-% relative to the dental zirconia mill blank.

[0309] All disclosures of the patents, patent documents and publications cited herein are incorporated by reference in their entirety, as if each file were cited separately. Various modifications and changes of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The above description, examples and data provide a description of the manufacture, use and method of the present invention of the composition of the present invention. The present invention is not limited to the embodiments disclosed herein. Those skilled in the art will appreciate that many alternative embodiments can achieve the present invention without departing from the spirit and scope of the present invention.

[0310] The following examples are intended to further illustrate the present invention.

[0311] Example

[0312] Unless otherwise specified, all parts and percentages are based on weight, all water is deionized water, and all molecular weights are weight average molecular weight. In addition, unless otherwise specified, all experiments were performed under ambient conditions (23° C.; 1013 mbar).

[0313] method

[0314] Elemental composition

[0315] If desired, the elemental composition can be determined by X-ray fluorescence spectroscopy (XRF), for example using a ZSX Primus II from Rigaku, Japan. This method is particularly suitable for analyzing solids, such as zirconia ceramics or glass materials.

[0316] Average connection pore size

[0317] If desired, the average connected pore size can be determined as follows: Using a porosimeter (Kanta Poremaster), mercury is introduced into the porous material under high pressure. The applied pressure is related to the pore size via the opposing force of the mercury surface tension. Using the so-called Washburn equation, the average connected pore size can be determined. The following measurement parameters are applied or used in the calculation of the results: pressure range from 20 PSIA to 60000 PSIA, temperature during measurement of 20°C, Hg contact angle of 140°, and Hg surface tension of 480 mN / m.

[0318] Porosity

[0319] If desired, the porosity can be determined as follows: Porosity = (1-(density of porous material / density of sintered material)) x 100. The density of the porous material can be calculated by dividing the weight by the volume. The volume can be obtained by geometric measurement.

[0320] Average grain size of sintered body

[0321] If necessary, the average grain size can be determined by line analysis. Grain size measurements were performed using FESEM micrographs at 70,000 times magnification. Three or four micrographs of different regions of the sintered body were used for each sample. Ten horizontal lines were drawn that were roughly equally spaced across the height of each micrograph. The number of grain boundary intersections observed on each line was counted and used to calculate the average distance between intersections. The average distance of each line was multiplied by 1.56 to determine the grain size, and the value was averaged for all lines of all micrographs for each sample.

[0322] Average primary particle size of powder composition

[0323] If desired, the average primary particle size of the particles of the zirconium oxide powder can be determined by light scattering techniques, for example using a Mastersizer 3000 from Malvern Panalytical.

[0324] Biaxial bending strength

[0325] If necessary, the biaxial flexural strength of the pre-sintered material can be determined according to ISO 6872, but with the following modifications: Use a dry cutting saw to saw the pre-sintered sample into a thin sheet with a thickness of 2+ / -0.1mm. The diameter of the sample should be 17+ / -2mm. Use silicon carbide sandpaper (P2500) to grind the parallel large faces of the thin sheet. Each thin sheet is centered on a support of three steel balls (ball diameter is 6mm), wherein the support diameter is 14mm. The diameter of the punch in contact with the thin sheet is 3.6mm. The punch is pushed onto the thin sheet at a rate of 0.1mm / minute. The minimum value of 15 samples is measured to determine the average strength. It can be tested in an Instron5566 universal testing machine (Instron Deutschland GmbH, Germany).

[0326] Vickers hardness

[0327] If necessary, the Vickers hardness can be determined according to ISO 14705, but with the following modifications: The surface of the pre-sintered sample is ground using silicon carbide sandpaper (P2500). The surface of the sintered sample is polished with a 20 μm diamond suspension. The test force is adjusted to the hardness level of the sample. The test force used is between 0.2 kg and 2 kg and is applied for 15 seconds for each indentation. A minimum of 10 indentations are measured to determine the average Vickers hardness. The test can be performed using a hardness tester Leco M-400-G (Leco Instruments).

[0328] density

[0329] If necessary, the density of the sintered material can be measured by the Archimedes technique. The measurement is carried out on a precision balance using a density determination kit (identified as "YDK01", from Sartorius AG). In this procedure, the sample is first weighed in air (A) and then immersed in a solution (B). The solution is a 0.05 wt. % surfactant solution in deionized water (e.g. "Berol 266", Fa. Hoesch). The density is calculated using the formula ρ = (A / (AB))ρ0, where ρ0 is the density of water. The relative density can be calculated based on the theoretical density of the material (ρt), ρ rel =(ρ / ρt)100.

[0330] Crystalline phase content

[0331] If desired, the X-ray diffraction can be performed using a Bruker D8 Discover instrument (Bruker AXS) and TOPAS provided by the manufacturer (Bruker). TMSoftware that applies Rietveld analysis and determines phase contents using Bragg-Brentano geometry. TM The phase contents calculated by the software are given in wt %.The measurements are typically performed down to a depth of 3 μm to 6 μm, which is approximately the penetration depth of x-rays in zirconium oxide.

[0332] BET Surface

[0333] If desired, the BET surface of the porous article can be determined as follows: The total pore volume and average pore size can be analyzed using N2 adsorption isotherms and BET surface area analysis. If necessary, cut about 0.1 to 2 grams of sample from a larger sample to insert into the straight test tube of the instrument. Prior to analysis, all samples were vacuum degassed at 120°C for more than 1 hour. The samples were then measured in a 9 mm cell with a 2 cm bulb and a 5 mm glass rod using Belsorb II (Robotherm Precision Measuring Technology, Bochum, Germany). ) distribution) adsorption and desorption of N2 gas to analyze the sample. At the temperature of liquid nitrogen, adsorption data points were collected from 0.1p / p0 to 0.99p / p0, and desorption points were collected from 0.99p / p0 to 0.5p / p0. The specific surface area S was calculated by the BET method at p / p0 0.25-0.3 (for details on calculation, please refer to Belsorb Analysis Software User Manual Operating Manual, Chapter 12, Bell Japan.INC).

[0334] Fluorescence

[0335] If necessary, place the sample in a UV light box for detecting, for example, thin layer chromatography plates. Fluorescence can be detected by the human eye as the sample is brighter against a dark background.

[0336] Methods for measuring translucency

[0337] If desired, the translucency of the ceramic article can be evaluated using the following procedure: a disc-shaped test piece with an approximate thickness of 1±0.05 mm and a measuring area of ​​at least 10 mm in diameter is provided. To prepare the test piece, a pre-sintered block sample is sawed into a thin sheet with a thickness of about 1.3 mm using a dry cutting saw. The parallel large faces of the thin sheet are ground using silicon carbide sandpaper (P2500). Alternatively, a disc-shaped sample can also be prepared during the pressing step, which eliminates the need for sawing and grinding. The sample is sintered in an appropriate heating furnace to a sintered sample with a thickness of 1±0.05 mm. During firing, a spectrophotometer (e.g., X-Rite Color i7, Grand Rapids, USA) is used to measure the sintered sample in reflection mode against a white and black background to obtain the opacity (contrast ratio) of the material, which is an average value in the wavelength range of 400 nm to 700 nm. The translucency T is calculated according to T=100%-opacity (in percentage). Higher translucency values ​​indicate greater light transmittance and less opacity.

[0338] color

[0339] If desired, L*a*b* values ​​can be determined using the same equipment and material samples used to determine opacity (contrast ratio) and translucency.

[0340] Material

[0341] The powders described in Table 1 can be used:

[0342] Table 1: Amount of Inorganic Components in Zirconia Powder Used in Examples (mol%)

[0343]

[0344]

[0345] The molecular weights used for the calculations are: ZrO2: 123.22 g / mole; HfO2: 210.49 g / mole; Y2O3: 225.81 g / mole; Al2O3: 101.96 g / mole; Er2O3: 382.56 g / mole; Tb4O7: 747.70 g / mole; MnO2: 86.94 g / mole.

[0346] General procedure for preparing individual zirconium oxide powders

[0347] The separate powders can be obtained by a process comprising the steps of treating a coprecipitated zirconium oxide / hafnium oxide / yttrium oxide powder with a powder containing a coloring oxide, for example with an oxide of Er, Tb or Mn; optionally also adding an aluminum oxide powder; milling the mixture in the wet state and (spray) drying the mixture to obtain a compressible powder.

[0348] General procedure for preparing mixed zirconia powders

[0349] The mixed powder can be prepared by combining the four raw materials from Table 1 (e.g., ZRO2-3.2Y and ZRO2-P1 (Er) and ZRO2-Y (Tb) and ZRO2-G (Mn)) in the desired amounts and shaking the mixture with a laboratory mixing device (Minishaker MS2 from IKA Corporation (IKA)) until a homogeneous mixture is obtained.

[0350] General procedure for preparing dental zirconia samples

[0351] The sample can be prepared by using the above-mentioned zirconium oxide material.

[0352] Apply the following steps:

[0353] mixing four zirconium oxide powders into a powder composition;

[0354] The powder composition was filled in a mold (diameter: 24.9 mm);

[0355] Apply pressure (97kN) to the powder filling;

[0356] Demolding the compacted body;

[0357] applying a heat treatment at 960°C for about 1 hour;

[0358] Discs were sliced ​​and ground from the obtained blocks.

[0359] The thickness of the samples was approximately 1.3 mm. After sintering, the sample dimensions were suitable for color and translucency measurements.

[0360] Embodiment 1 of the present invention (IE) :

[0361] The Y-gradient is about 3.0 mol% Y2O3 in the bulk and about 5.6 mol% Y2O3 in the enamel:

[0362] Zirconia powders ZRO2-3.2Y, ZRO2-5.6Y, ZRO2-P2, ZRO2-Y and ZRO2-G are mixed in different ratios to obtain the zirconium oxide powders for different Vita TM Classical shades (i.e. A1, A2, A3, A4, B4, C4, D4) and very light bleached shades of body compositions (with ZRO 2-3.2Y) and enamel compositions (with ZRO 2-5.6Y).

[0363] Table 2a: Composition of Example 1 (IE1) of the present invention .

[0364]

[0365] Table 2b: Composition of Example 1 (IE1) of the present invention (continued) .

[0366]

[0367] Embodiment 2 of the present invention (IE) :

[0368] The Y-gradient is about 4.0 mol% Y2O3 in the bulk and about 5.6 mol% Y2O3 in the enamel:

[0369] Zirconia powders ZRO2-4.0Y, ZRO2-5.6Y, ZRO2-P2, ZRO2-Y and ZRO2-G are used to obtain a less pronounced Y gradient.

[0370] Table 3a: Composition of Example 2 (IE2) of the present invention .

[0371]

[0372] Table 3b: Composition of Inventive Example 2 (IE2) (Continued) .

[0373]

[0374]

[0375] Comparative Example (CE) 1 :

[0376] The Y-gradient is about 3.0 mol% Y2O3 in the bulk and about 5.6 mol% Y2O3 in the enamel:

[0377] Different erbium doped zirconium oxide powders than in Example 1 of the present invention were used to obtain the same color as in IE 1. Powders ZRO2-3.2Y, ZRO2-5.6Y, ZRO2-P1, ZRO2-Y and ZRO2-G were used.

[0378] Table 4a: Composition of Comparative Example 1 (CE1) .

[0379]

[0380]

[0381] Table 4b: Composition of Comparative Example 1 (CE1) (continued) .

[0382]

[0383] Comparative Example (CE) 2 :

[0384] The Y-gradient is about 4.0 mol% Y2O3 in the bulk and about 5.6 mol% Y2O3 in the enamel:

[0385] Zirconia powders ZRO2-4.0Y, ZRO2-5.6Y, ZRO2-P1, ZRO2-Y and ZRO2-G are used to obtain a less pronounced Y gradient.

[0386] Table 5a: Composition of Comparative Example 2 (CE2) .

[0387]

[0388] Table 5b: Composition of Comparative Example 2 (CE2) (continued) .

[0389]

[0390]

[0391] The invention examples and comparative examples of each color are intended to contain the same mole % of coloring ions. However, the precision of the amounts of the different ZRO2 powders was chosen to be one tenth of a weight %. This is a reasonable precision to work with in the manufacturing process, but it may result in very small variations in the composition of the mixed powders. Such small variations have a negligible effect on the resulting color.

[0392] The "color ratio R" values ​​shown in Table 6 are calculated from the mole % values ​​and can therefore sometimes also deviate in the last digit. A person skilled in the art will understand that if the precision of the amounts of the different ZRO2 powders is increased to a few percent or even a few thousandths of a weight %, exactly the same composition (down to the fourth digit in Tables 2 to 5) can be obtained, although this does not bring additional benefits to the material.

[0393] For each color from Tables 2 to 5, calculate the "Color Ratio R" by dividing the "Coloring Oxide Sum" of the enamel by the "Coloring Oxide Sum" of the body.

[0394] For each color from Tables 2 to 5, the "Color + Y Ratio R" was calculated by dividing the "Colored Oxide + Yttria Total" of the enamel by the "Colored Oxide + Yttria Total" of the body.

[0395] The “color + Y deviation D” is calculated by using formula (1), where R n is the "color + Y ratio R" value of the corresponding color, and R max It is the "Color+Y Ratio R" value of bleaching.

[0396] D values ​​exceeding the limit of 2.70 are underlined.

[0397] For example, for Example 1 (A1) of the present invention, the calculation is as follows:

[0398] "Total coloring oxides (A1)" of the enamel: 0.0355 mol%

[0399] "Total coloring oxides (A1)" of the main body: 0.0669 mol%

[0400] ≥ "Color ratio R(A1)": 0.0355 mol% / 0.0669 mol% = 0.5306

[0401] "Total of coloring oxides + yttrium oxide (A1)" of enamel: 5.5557 mol%

[0402] Main component "coloring oxide + yttrium oxide total (A1)": 3.1960 mol%

[0403] ≥ "Color + Y ratio R (A1)": 5.5557 mol% / 3.1960 mol% = 1.7383 "Total of colored oxides + yttrium oxide (bleaching)" of enamel: 5.6145 mol%

[0404] Main body "coloring oxide + yttrium oxide total (bleaching)": 3.1924 mol%

[0405] ≥ "Color ratio R (bleached)": 5.6145 mol% / 3.1924 mol% = 1.7587

[0406] “R max " corresponds to "Color Y Ratio R (bleached)": 1.7587

[0407] “R A1 " corresponds to "Color Y ratio R (A1)": 1.7383

[0408] ≥D A1 =((R max -R A1 ) / R max *100) / R max 2 =((1.7587-1.7383) / 1.7587*100) / 1.7587 2 =((0.0204 / 1.7587)*100) / 3.0930=1.1604 / 3.0930=0.3751

[0409]

[0410] The ratios of the content of colouring oxides (in mol %) in enamel: bulk ("colour ratio R") are all <1, since the enamel layer has a lighter hue than the bulk layer. The ratios of the content of colouring oxides + yttria (in mol %) in enamel: bulk ("colour + R ratio") are all >1, since the enamel layer has a higher yttria content than the bulk layer, which is not compensated by the colouring oxides.

[0411] The results in Table 6 show that the inventive examples have very stable enamel:host doping ratios in all colors tested (D values ​​for all colors are below 2.70).

[0412] Such a stable ratio cannot be obtained with the powder set of the comparative examples (D values ​​above 2.70 for fairly dark colors).

[0413] For aesthetic color gradients, the embodiments all have a "color ratio R" of 0.49-0.77. Numbers closer to 1 would indicate a more subtle gradient that may be smaller than desired or even difficult to see. Numbers much lower than 0.5 may indicate a color gradient that is too dramatic.

[0414] Embodiments of the present invention having high and stable "Color+Y Ratio R" values ​​are expected to display desirable, noticeable, and reliable translucency gradients over a wide range of different colors.

Claims

1. A set of porous zirconia dental mill blanks, the set of porous zirconia dental mill blanks comprising at least two differently colored porous zirconia dental mill blanks, The porous zirconia dental milling blank comprising zirconium oxide, yttrium oxide, coloring ions and optionally aluminum oxide, comprising multiple layers having different yttrium oxide contents, Having a bottom layer and a top layer, The contents of yttrium oxide and coloring ions in mol % vary in opposite directions from the bottom layer to the top layer, and adjusting the content of yttrium oxide and coloring ions in mol % to provide a substantially constant ratio of the sum of yttrium oxide and coloring ions in mol % between the top layer and the bottom layer of the differently colored zirconia dental mill blanks, substantially constant meaning that the ratio of the sum of yttrium oxide and coloring ions in mol % in the top layer and the sum of yttrium oxide and coloring ions in mol % in the bottom layer of the porous zirconia dental mill blank varies by a deviation D which is not greater than 2.70 for all colored mill blanks of the set, wherein the set of porous zirconia dental mill blanks has a set of deviation values ​​D n , the deviation value is calculated from the ratio R of the sum of yttrium oxide and coloring ions in the top layer in mol % and the sum of yttrium oxide and coloring ions in the bottom layer in mol % using the following formula, D n =((R max -R n ) / R max *100) / R max 2 , Wherein for the differently colored porous zirconia dental mill blanks comprising N different colors in the group, D n Not more than 2.70, where R max is the highest ratio found within the group, and N ≥ 2, n = 1, 2, ..., N; The porous zirconia dental milling blank comprises: 89.35 mol% to 97.18 mol% ZrO2, 0 mol% to 3 mol% HfO2, 2.8 mol% to 7.0 mol% Y2O3, 0 mol% to 0.15 mol% Al2O3, Coloring ions, the amount of the coloring ions calculated as their respective oxides is 0.02 mol % to 0.5 mol %, The mol % are calculated relative to the material of the porous zirconia dental mill blank, The coloring ions are Er and at least one other ion selected from Fe, Tb, V, Mn, Cr, and Co.

2. A set of porous zirconia dental mill blanks according to claim 1, wherein the content of yttria in the porous zirconia dental mill blanks increases from the bottom layer to the top layer, and the content of coloring ions in the porous zirconia dental mill blanks decreases from the bottom layer to the top layer.

3. A set of porous zirconia dental mill blanks according to claim 1 or 2, the yttria content of the differently colored porous zirconia dental mill blanks differing from layer to layer by no more than 0.5 mol %.

4. A set of porous zirconia dental mill blanks according to claim 1 or 2, the yttria content of the differently colored porous zirconia dental mill blanks differing from layer to layer by an amount in the range of 0.35 mol % to 0.5 mol %.

5. A set of porous zirconia dental mill blanks according to claim 1 or 2, comprising at least 3 layers.

6. A set of porous zirconia dental mill blanks according to claim 1 or 2, the thickness of a single layer of said porous zirconia dental mill blanks being in the range of 2 mm to 12 mm.

7. A set of porous zirconia dental mill blanks according to claim 1 or 2, characterized by the following features alone or in combination: Density: 2.8g / cm 3 Up to 3.2g / cm 3 ; Biaxial flexural strength: 8MPa to 80MPa; BET surface area: 2m 2 / g to 20m 2 / g; Vickers hardness: 25 (HV 0.5) to 150 (HV 0.5) or 35 (HV 1) to 140 (HV 1).

8. A set of porous zirconia dental mill blanks according to claim 1 or 2, characterized by the following features: Number of layers: 3 to 7 layers; Yttria concentration difference between layers: 0.35 mol% to 0.5 mol%; Containing Er and at least one other coloring ion selected from Fe, Tb, V, Mn, Cr, and Co; Yttria concentration: 2.8 mol% to 7.0 mol%, with a difference of at least 1.0 mol% between the top and bottom layers.

9. A set of porous zirconia dental mill blanks according to claim 1 or 2, The ratio R of (the amount of yttrium oxide + the amount of colored ions in the top layer, in mol %) / (the amount of yttrium oxide + the amount of colored ions in the bottom layer, in mol %) in the range of 1.83 to 1.67 for porous zirconia dental mill blanks having a gradient of yttria from 3.0 mol % to 5.5 mol % from said bottom layer to said top layer; in the range of 1.37 to 1.31 for porous zirconia dental mill blanks having a gradient of yttria from 4.0 mol% to 5.5 mol% from said bottom layer to said top layer; for porous zirconia dental mill blanks having a gradient of yttria from 3.0 mol % to 5.0 mol % from said bottom layer to said top layer in the range of 1.66 to 1.54; in the range of 1.25 to 1.20 for porous zirconia dental mill blanks having a gradient of yttria from 4.0 mol% to 5.0 mol% from said bottom layer to said top layer; For porous zirconia dental mill blanks having a gradient of yttria from 3.2 mol % to 5.65 mol % from the bottom layer to the top layer is in the range of 1.76 to 1.

62.

10. A method for producing a set of porous zirconia dental mill blanks according to any one of claims 1 to 9, the method comprising the following steps: A powder composition of at least: Zirconia powder ZP1 with yttria content Y1, Zirconia powder ZP2 with yttria content Y2, Zirconia powder ZP3 containing coloring ions CI-A, Zirconia powder ZP4 containing coloring ions CI-B, The yttrium oxide content Y2 is higher than the yttrium oxide content Y1 in mol %; Zirconium oxide powders ZP1, ZP2, ZP3 and ZP4 were mixed in different mixing ratios to obtain at least Zirconia powder composition ZP-MX-B, Zirconia powder composition ZP-MX-I m , Zirconia powder composition ZP-MX-T, The yttrium oxide content of the zirconium oxide powder composition in mol% ZP-MX-B<ZP-MX-I m <ZP-MX-T, The number of intermediate layers is M≥1, where m=1, ..., M, For each colored porous zirconia dental mill blank of the set, the zirconia powder composition is laid out in the cavity of the mold such that The ZP-MX-B layer is located on one or more ZP-MX-I m Below the layer, The one or more ZP-MX-I m The layer is located below the ZP-MX-T layer; compacting the laid zirconium oxide powder composition; The compacted zirconium oxide powder composition is optionally heat treated.

11. The method according to claim 10, wherein the zirconium oxide powder composition layer has a layer thickness of: ZP-MX-B>ZP-MX-I m <ZP-MX-T。 12. A method for producing a dental restoration, the method comprising the steps of: Providing a set of porous zirconia dental mill blanks according to any one of claims 1 to 9; selecting a porous zirconia dental mill blank from the group; machining a porous dental restoration precursor from the porous zirconia dental milling blank; The porous dental restoration precursor is sintered to obtain a dental restoration.

13. The method according to claim 12, wherein the dental restoration is characterized by the following features alone or in combination: Density: 5.8g / cm 3 Up to 6.1g / cm 3 ; Translucency: at least 30%, measured in reflection mode, averaged over a wavelength between 400 nm and 700 nm, determined on a sample having a thickness of 1 mm and cut from said top layer of said porous zirconia dental mill blank; Translucency: at least 15%, measured in reflection mode, averaged over a wavelength between 400 nm and 700 nm, determined on a sample having a thickness of 1 mm and cut from said bottom layer of said porous zirconia dental mill blank.

14. A kit comprising a dental cement and a set of porous zirconia dental mill blanks according to any one of claims 1 to 9.

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