Glass ceramic moulding for dental purposes

Abstract

The present invention relates to glass ceramic mouldings comprising crystals of zirconium dioxide, into which one or more co-metal oxides are incorporated.

Description

[0001] Glass-ceramic molded body for dental purposes The present invention relates to a glass-ceramic molded body that can advantageously be used for dental purposes, as well as to a method for its production and its use in the fabrication of dental restorations. Modern dental prosthetic materials must meet high stability and appearance requirements. The balance between effort and quality plays a major role, as each dental restoration is unique and custom-made for each patient. During production, recreating the appearance of aesthetic teeth is particularly important for patient well-being, so restorations should have a translucency or opacity depending on their area of ​​application. Furthermore, the materials used should be able to withstand the daily mechanical and chemical stresses encountered during food intake.Due to this special requirement profile, glass-ceramics have established themselves as a common material for dental restorations, with their strength and aesthetic properties being particularly valued. The crystalline component not only prevents the propagation of cracks but also reflects and deflects light differently than with conventional glass. This creates a translucency that closely resembles that of natural teeth, which is why dental glass-ceramics are used particularly in the aesthetic zone of the anterior teeth. Journal of the European Ceramic Society, Vol. 41, No. 11, pages 5728-5739 describes glass-ceramic materials that contain a zirconium silicate glass matrix in addition to lithium disilicate, lithium metasilicate, and lithium phosphate. However, no statements are made regarding the use of zirconium oxide cocrystallites and their application for dental restorations with color gradients.The Journal of the Mechanical Behavior of Biomedical Materials, Elsevier, Amsterdam, Vol. 105, pp. 1-8 describes processes for plasma sintering and pressureless sintering of ZrO2-containing lithium silicate glass-ceramics. These processes allow sintering at low temperatures and the formation of lithium disilicate nanocrystals. However, no statements are made about the use of zirconium oxide cocrystals and their application for dental restorations with color gradients. Propriedades de dissilicato de lito Reforcado com ZrO2, Congresso Brasiliero de Engenharia e Ciencia dos Materiais discloses ZrO2-containing glass-ceramics. However, zirconium oxide cocrystals that form a color gradient in a ceramic block or a dental restoration are not described. EP 3772492 A1 describes glass-ceramics that are made more opaque through multiple heat treatments. However, the formation of zirconium oxide cocrystallites is not disclosed.WO 2017 / 067909 A1 describes glass-ceramics whose optical properties are adjusted through multiple heating steps. However, the formation of zirconium oxide cocrystallites is not disclosed. EP 2765119 describes a blank for dental purposes comprising at least two interconnected layers of lithium silicate glass, lithium silicate glass with nuclei, or lithium metasilicate glass-ceramic, wherein the layers differ in color and are monolithic. This should make it possible to closely mimic the optical properties of natural tooth material and achieve a shape without shrinkage. WO 2013 / 086187 relates to a lithium silicate glass ceramic which comprises 6 to 30 wt% Cs2O, 55 to 80 wt% SiO2, 1 to 5 wt% Al2O3 and B2O3, 7 to 16 wt% Li2O and 1 to 5 wt% P2O5, wherein the wt% values ​​refer to the total weight of the glass ceramic.This composition is intended to produce blocks with particularly high transparency. EP 2114348 describes a ceramic material made of yttrium-stabilized zirconium dioxide containing SiO2 58.0-74.0 wt.%, Al2O3 4.0-19.0 wt.%, Li2O 5.0-17.0 wt.%, Na2O 4.0-12.0 wt.%, and ZrO2 0.5-6.0 wt.%, thus achieving high flexural strength with simultaneous translucency. Despite the positive aesthetic results achieved so far with glass-ceramic replacement materials in the dental field, there is still a need in the state of the art for materials that can replicate the natural translucency and color gradient of a tooth without discernible transitions between the incisal, dentin, and cervical regions. As a result, patients who seek dental restorations often feel embarrassed because the procedure is associated with inadequate oral hygiene.As a result, there is a high demand for dental replacement materials that closely resemble the appearance of natural teeth. At the same time, the glass-ceramic materials must exhibit high strength while still being easy to work and produce. Surprisingly, it has been found that glass-ceramic moldings containing zirconium dioxide crystals incorporating one or more Co-metal oxides solve the aforementioned problems and are suitable for replicating a tooth's natural translucency and color gradient without discernible transitions between the incisal, dentin, and cervical regions. At the same time, they can be used to produce highly machinable, high-strength glass-ceramic moldings. The subject matter of the present invention is set forth in the independent claims. Preferred embodiments are set forth, inter alia, in the dependent claims.The present invention relates to a glass-ceramic molded body comprising crystals of zirconium dioxide incorporating one or more Co-metal oxide(s). The glass-ceramic molded bodies according to the invention preferably have a color gradient and / or translucency gradient and are particularly suitable as monolithic molded bodies for dental restorations. It has surprisingly been found that crystals can be crystallized from an amorphous glass matrix in which the crystals consist of zirconium dioxide incorporating one or more Co-metal oxide(s). These crystals are also referred to below as zirconium dioxide-Co-metal oxide crystals. In a preferred embodiment, the crystals of zirconium dioxide incorporating one or more Co-metal oxide(s) are mixed crystals of zirconium dioxide and Co-metal oxide(s).In a further preferred embodiment, however, the crystals can also be zirconium dioxide crystals doped with Co metal oxides. In a further preferred embodiment, the glass-ceramic shaped body can contain and / or f-element oxides as Co metal oxide(s). This can produce a color effect that differs from the color of the shaped body without a crystalline portion and causes a continuous increase in color saturation. In a preferred embodiment, the Co metal oxide is selected from the group consisting of the oxides of the d and f elements of the periodic table. The Co metal oxide is particularly preferably an oxide from the group of elements selected from Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Lu, Ta, W, Re, Os, Ir, Pt and Au. More preferably, the Co metal oxide is an oxide from the group of elements selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb.Oxides of Co metals, which produce tooth-colored tones, are particularly suitable. These are known to those skilled in the technical field of dental technology. Particularly good results with regard to natural tooth colors and color gradients have been achieved when the Co metal oxide is selected from the group consisting of cerium oxide, terbium oxide, praseodymium oxide, erbium oxide, neodymium oxide, europium oxide, iron oxide, vanadium oxide, manganese oxide, and mixtures thereof. In particular, the oxides of cerium, terbium, praseodymium, erbium, neodymium, europium, iron, vanadium, or manganese, as well as mixtures thereof, can be excellently incorporated into lithium silicate glass ceramics and lead to the formation of zirconium dioxide crystals in which one or more of these Co metal oxide(s) can be incorporated. These Co metal oxide(s) incorporated into the zirconium dioxide particularly support the desired color gradient. The Co metal oxide cerium oxide is especially preferred.This allows particularly good color gradients that closely approximate natural tooth colors to be achieved. In a preferred embodiment, the Co metal oxide(s) are present in an amount of preferably 0.1 to 10 wt.%. The Co metal oxide(s) are particularly preferably present in an amount of 0.1 to 8 wt.%, particularly preferably 0.5 to 7 wt.%, and in particular 1 to 4 wt.%, especially 0.4 to 2.5 wt.%. Cerium oxide is especially preferred. The weight amounts are in each case based on the total weight of the glass-ceramic molded body. In a further preferred embodiment of the present invention, the glass-ceramic shaped body has crystals of the formula MZZr1-ZO2 (or also referred to as MexZr1-xO2, where Me=M and x=z), where M is a d- or f-element and z is a rational number from 0.0001 to 0.5, preferably from 0.001 to 0.3, particularly preferably from 0.001 to 0.1 or from 0.002 to 0.05 or from 0.003 to 0.03.Particularly preferred are crystals of the above-mentioned formula MZZr1-ZO2, where M is selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Lu, Ta, W, Re, Os, Ir, Pt, and Au. Also preferred are crystals of the above-mentioned formula MZZr1-ZO2, where M is selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Glass ceramics particularly suitable for the dental sector and having excellent colors and color gradients can be obtained using the glass-ceramic molded bodies according to the invention, wherein the molded body comprises crystals of the above-mentioned formula MZZr1-ZO2, where M is selected from the group consisting of Ce, Tb, Pr, Er, Nd, Eu, Fe, V, and Mn. Without being bound to any theory, it is assumed that the use of the aforementioned Co metal oxides in combination with zirconium dioxide leads to the incorporation of the Co metal oxides into the crystals of the zirconium dioxide.The crystallization of zirconium dioxide with a compound containing Co metal oxides, particularly d- or f-element oxides, can lead to the incorporation of these elements into lattice or non-lattice sites in the ZrO2 lattice. Zirconium dioxide is preferably the host lattice, whose particles, usually zirconium, are replaced by a Co metal, particularly d- or f-element. Thus, the term "incorporation" could be understood as the substitution of the particles of the host lattice and / or insertion into existing gaps in the host lattice. The resulting crystals are known to those skilled in the art as substitution and / or intercalation solid solutions.Thus, in a preferred embodiment of the invention, tetragonal and / or cubic solid solutions are formed, particularly preferably in the form of the previously defined formula MZZr1-ZO2 (where M = d- or f-element and z<0.2, preferably from 0.001 to 0.1 or 0.002 to 0.05 or 0.003 to 0.03), since the lattice structure of the zirconium dioxide host lattice can be retained. For homeotypic solid solutions, this theoretical consideration would require that the incorporated Co metals, particularly d- and / or f-elements, have the same crystal structure as the ZrO2, which is not always the case. Furthermore, the color effect of the preferred embodiment of the shaped body according to the invention could be attributed to so-called heterotypic solid solutions. In such solid solutions, one crystal type imposes its crystal structure on the other; well-known examples are alloys, which are also called binary systems with limited solubility in the solid state.For example, ZrO2, which is usually present as the main component, could impose its crystal structure on the Co metal oxides, particularly the d- and / or f-element oxides, thereby changing the field of these cations in the lattice compared to that surrounding them in the glass matrix, resulting in a color effect. Furthermore, incorporation of the crystals can be understood as doping the ZrO2 crystal phase. As is known from semiconductor technology, a uniform distribution of atoms in the main crystal phase is ensured by admixing the Co metal compounds, particularly the d- and / or f-elements, to be incorporated. One way to describe the incorporated crystals in the main crystal phase is the above-mentioned expression MZZr1-ZO2, where M are metals selected, in particular, from the d- and / or f-elements in the composition of the glass-ceramic molded body according to the invention.In principle, z can be any rational number, preferably from 0.001 to 0.3, in particular from 0.002 to 0.1, especially from 0.003 to 0.05, which is determined by the reference domain. Furthermore, the incorporation of the Co metal elements, in particular the d and / or f elements, can be ordered or random. This can be controlled using the melting temperature and / or crystallization temperature, which are known to the person skilled in the art. The Co metal oxides can be incorporated into the glass-ceramic molded body in various forms, depending on the manufacturing process. Depending on the oxidation time and temperature, the compounds of the Co metals, in particular the f and d elements, are incorporated into the zirconium dioxide crystals. During the manufacturing process or crystallization, depending on the compound, the electron configuration of the incorporated Co metal, in particular the f and / or d element, can change, so that the color saturation can also be controlled.Furthermore, in a preferred embodiment, the glass-ceramic shaped body according to the invention can contain the above-described mixed crystals MZZr1-ZO2, which are present as a crystal phase, preferably in an amount of 0.1 to 15 wt.%, in particular of 0.2 to 10 wt.% and particularly preferably of 0.2 to 8 wt.% or of 0.3 to 4 wt.%, in each case based on the total weight of the crystal phases in the shaped body. In a further preferred embodiment, the glass-ceramic shaped bodies according to the invention have the aforementioned mixed crystals MZZr1-ZO2, wherein the molar ratio of n(M) / n(Zr), with n(M) being the molar amount of the Co metal, in particular of the d- or f-element, of the corresponding compound and n(Zr) being the molar amount of Zr from the ZrO2 used, is from 0.0001 to 0.6, preferably from 0.001 to 0.55, particularly preferably from 0.04 to 0.4, especially preferably from 0.1 to 0.3 and most especially preferably from 0.1 to 0.2.In a preferred embodiment, the glass-ceramic molded body is a monolithic molded body for dental restorations. The monolithic structure is advantageous because no layered structure with adjustments between the individual layers is necessary. The glass-ceramics according to the invention can thus ensure a stepless and continuous color gradient. The glass-ceramic molded bodies according to the invention have an amorphous portion and a crystalline portion, with the molded body preferably having an inhomogeneous distribution of amorphous and crystalline portions. In a particularly preferred embodiment, the molded body according to the invention has a gradually changing weight ratio of amorphous to crystalline portion. The gradient usually runs along an axis passing through the molded body.Shaped bodies which have a gradually changing weight fraction of zirconium dioxide crystals incorporating one or more cobalt metal oxides have proven particularly excellent for the formation of tooth colors and tooth color gradients. In a preferred embodiment of the present invention, the zirconium dioxide cobalt metal oxide crystals are distributed inhomogeneously within the shaped body. Inhomogeneous here means, for example, that the zirconium dioxide cobalt metal oxide crystal concentration within the shaped body differs in two different, but equally sized volume regions of the shaped body. The difference is macroscopically measurable and can, for example, be at least 0.0001%, at least preferably 0.001%, in each case based on the volume region with the higher concentration.The inhomogeneous distribution can be recognized, for example, by the presence of a color gradient and / or translucency gradient of the, particularly monolithic, molded bodies. In a further preferred embodiment, the gradual change in the percentage weight fraction of the zirconium dioxide crystals with incorporated Co-metal oxide in the preferred monolithic glass-ceramic molded body influences the color effects and / or color saturation. The color gradient and color saturation can be induced or controlled according to the gradual change in the zirconium dioxide Co-metal oxide crystals. The gradient of the zirconium dioxide Co-metal oxide crystals and the proportion of amorphous to crystalline portion preferably run from the tooth neck to the tooth enamel (incisal edge), so that the color saturation and / or color gradient preferably increases from the tooth enamel to the tooth neck.In the present invention, color saturation refers to the degree to which a color differs from an achromatic stimulus, regardless of its brightness. Thus, for example, the colors white, gray, and black have a saturation of 0%, whereas bright colors have a saturation of 100%. The terms color saturation, chromacity, colorfulness, color intensity, brilliance, color depth, and color strength are synonymous in the present invention and thus interchangeable. The color can be characterized in particular by its L*a*b* value or by a color key commonly used in the dental industry. Translucency refers to the light transmittance of the glass-ceramic molded body according to the invention, which can change with the gradient. Preferred values ​​for L are from 60 to 90, particularly preferably from 70 to 80. Furthermore, the value for a can be selected from the range from 0 to 6, particularly preferably from 0.1 to 5.For the b value, values ​​from 5 to 40 are possible, preferably from 10 to 35. It is particularly preferred that for all parameters, i.e. L, a and b, higher values ​​are selected at the tooth neck than at the tooth incisal edge for the respective parameter. Furthermore, the color can be characterized by the difference in the L*a*b values. For example, the color difference from the tooth neck to the tooth incisal edge can be described by the difference in the L, a and / or b values ​​(hereinafter ΔL, Δa and Δb). Thus, in a preferred embodiment, ΔL can be from 0 to 10, preferably from 1 to 5, Δa from 0 to 5, preferably from 0.5 to 2.5, and Δb from 0 to 15 and preferably from 6 to 12. The color difference can also be described using ΔE, which is familiar to the person skilled in the art. Preferably, the ΔE is from 0 to 15, particularly preferably from 0.5 to 10 for the color distance and / or color difference between the neck of the tooth and the incisal edge.In order to replicate the appearance of a natural tooth, it has proven advantageous if the amorphous portion in the shaped body changes only to a small extent, with a minimum amorphous portion being preferred in each case. In a preferred embodiment, therefore, the amorphous portion in the shaped body changes along the gradient by at least 5 wt.%, preferably by at least 7 wt.%, but preferably by no more than 30 wt.%, in each case based on the total volume of the shaped body. In a particularly preferred embodiment, the change in the amorphous portion in the shaped body along the gradient is in the range from 5 to 30 wt.%, preferably from 15 to 25 wt.%, in each case based on the total weight of the shaped body.Furthermore, a further preferred embodiment is a preferably monolithic, glass-ceramic molded body according to the invention, which has zirconium dioxide-co-metal oxide crystallites with a maximum size of 1000 nm, preferably a maximum of 500 nm. The size can be determined using electron microscopy methods. According to the invention, "crystals" in this context means a crystal cluster. Thus, a zirconium dioxide-co-metal oxide crystal, or also called a zirconium dioxide-co-metal oxide cluster, is composed of several smaller zirconium dioxide-co-metal oxide (individual) crystallites. Surprisingly, it was found that precisely this small domain size in the preferred embodiment still leads to a very attractive translucency, even though zirconium dioxide-co-metal oxide crystals crystallize out. In this context, domain size and size are to be understood as synonyms and have the same meaning.The size, also called domain size, refers to the 2-dimensional observation of a crystal or cluster (compare Fig. 1). Surprisingly, it was found that if the crystallites are too large, the shaped body becomes opaque. This is possibly due to a large difference in the refractive index. The shaped body according to the invention thus has nanocrystalline ZrO2-Co-metal oxide (single) crystals in a cluster (compare Fig. 2), which preferably have a size of 200 nm or less, more preferably 100 nm or less, or especially preferably 50 nm or less. The size of the individual crystallites can be determined by X-ray diffraction. Furthermore, in a preferred embodiment, the weight ratio of the zirconium dioxide-Co-metal oxide crystals to the remaining crystalline and amorphous components changes gradually and continuously.Thus, in a preferred embodiment, there may be an increase or decrease in the ratio of existing zirconium dioxide crystals to the residual composition, i.e., the sum of the amorphous and residual crystalline portions. The gradual and preferably continuous change in the weight ratio of the zirconium dioxide-co-metal oxide crystals to the remaining crystalline and amorphous portions typically runs along an axis located in the molded body according to the invention. Furthermore, in a preferred embodiment, the glass-ceramic molded body according to the invention may have a region that is virtually free of crystalline zirconium dioxide-co-metal oxide crystals. The expression "virtually free of crystalline zirconium dioxide-co-metal oxide" means that, in the preferred embodiment, less than 5 wt. %, more preferably less than 1 wt. %, and most preferably less than 0.1 wt.-% zirconium dioxide based on the total weight of the zirconium-free region of the shaped body. It is particularly preferred that the shaped body has a region of 0 vol.% to 30 vol.% or of 1 vol.% to 35 vol.% or of 5 vol.% to 40 vol.% or of 10 to 50 vol.%, based on the total volume of the shaped body, which is almost free of zirconium dioxide-co-metal oxide crystals. Since the zirconium dioxide-co-metal oxide crystals in the glass-ceramic shaped body according to the invention are responsible for the color saturation in a preferred embodiment, in a preferred embodiment of the invention the tooth cutting edge is the region in which the zirconium dioxide-co-metal oxide-free region of the glass-ceramic shaped body can preferably be present. The glass-ceramic shaped bodies of the present invention preferably comprise lithium silicate.It has surprisingly been found that the crystallization of the zirconium dioxide co-metal oxides in a silicate matrix, in particular a lithium silicate environment, is particularly successful. In a preferred embodiment, the shaped body additionally comprises lithium metasilicate and / or lithium disilicate crystals. The shaped body particularly preferably comprises lithium disilicate as the main crystal phase. The glass-ceramic shaped bodies of the present invention preferably comprise SiO2 in an amount of 50 to 70 wt. %, more preferably 55 to 65 wt. %, in each case based on the total weight of the shaped body. The glass-ceramic shaped bodies of the present invention preferably comprise Li2O in an amount of preferably 10 to 25 wt. %, more preferably 15 to 22 wt. %, in each case based on the total weight of the shaped body. The glass-ceramic shaped bodies of the present invention preferably comprise K2O in an amount of preferably 0.5 to 6 wt.-%, more preferably from 1 to 5 wt.%, in each case based on the total weight of the shaped body. The glass-ceramic shaped bodies of the present invention preferably comprise P2O5 in an amount of preferably 2 to 12 wt.%, more preferably from 4 to 10 wt.%, in each case based on the total weight of the shaped body. The glass-ceramic shaped bodies of the present invention preferably comprise ZrO2 in an amount of preferably 6 to 15 wt.%, more preferably from 8 to 12 wt.%, in each case based on the total weight of the shaped body. In a preferred embodiment, the glass-ceramic shaped body comprises one or more of the following components: i) from 56 to 64 wt.%, preferably from 56 to 59 wt.% SiO2, ii) from 15 to 21 wt.%, preferably from 16 to 20 wt.% Li2O, iii) from 1 to 4 wt.% K2O, v) from 8 to 15 wt.%, preferably from 8 to 12 wt.%, in particular from 9 to 11 wt.% ZrO2, and vi) 0.1 to 8 wt.% Co metal oxide.In a preferred embodiment of the present invention, the shaped body according to the invention is a monolithic glass-ceramic shaped body for dental restorations, comprising an amorphous portion and a crystalline portion with (a) a continuously and gradually changing weight ratio of amorphous to crystalline portion and / or (b) a continuously and gradually changing percentage weight fraction of zirconium dioxide co-metal oxide crystals, wherein the shaped body preferably comprises lithium disilicate as the main crystal phase and the shaped body preferably comprises the following constituents: i) from 56 to 64 wt.%, preferably from 56 to 59 wt.% SiO. 2, ii) from 13 to 21 wt.%, preferably from 16 to 20 wt.%, Li2O, iii) from 1 to 4 wt.% K2O, iv) from 3 to 8 wt.% P2O5 and v) from 8 to 15 wt.%, preferably from 8 to 12 wt.%, in particular from 9 to 11 wt.% ZrO2. When manufacturing dental restoration materials, attempts are made to replicate both the mechanical and chemical resilience as well as the appearance of natural teeth. Even though some materials or mixtures are described in the prior art which demonstrate satisfactory mechanical and chemical resilience, recreating the appearance of natural teeth is difficult. This results from the complex appearance of teeth, which can be opaque or translucent. Glass-ceramic compositions which are pre-colored before crystallization or production have become particularly established.However, teeth have a natural color gradient that has not yet been reproduced because the materials used only represent a single color. As already mentioned, this leads to self-consciousness or embarrassment among patients, as dental restorations are easily recognized by others and such treatment suggests inadequate oral hygiene. Thus, there is a need for materials, particularly glass-ceramic compositions, used as molded bodies that can represent the natural color gradient of teeth while simultaneously offering mechanical and chemical resistance. Monolithic glass-ceramic molded bodies according to the invention are advantageous with a continuously and gradually changing weight ratio of amorphous to crystalline portion and the simultaneous presence of a continuously and gradually changing percentage weight fraction of zirconium dioxide co-metal oxide crystals in the molded body.This leads to a new type of color gradient which simultaneously maintains the translucency gradient. The gradual and continuous change preferably occurs along an axis running through the molded body according to the invention. According to the invention, the glass-ceramic molded body has a crystalline portion with zirconium dioxide-Co-metal oxide. However, in addition to the zirconium dioxide-Co-metal oxide crystals, other crystals can also be present in the glass-ceramic molded bodies. Preference is given to lithium disilicate, for example, which can be present in particular as the main constituent of the crystal phase. Main constituent of the crystal phase in the sense of the present invention means that the crystal proportion in wt. % is the highest in comparison to the other crystals with a different chemical composition in the molded body. The main constituent preferably makes up more than 30 wt. %, particularly preferably more than 40 wt. % and in particular more than 50 wt.-%, in each case based on the total weight of all crystals. In particular, lithium disilicate is present in a higher weight fraction than lithium metasilicate. The weight ratio of lithium disilicate to lithium metasilicate is preferably greater than 1:1, in particular greater than 1.1:1 or greater than 1.2:1. The additional other crystals can preferably be selected from the group consisting of lithium metasilicate, lithium phosphate, lithium aluminum oxide, spodumene, virgilite, keatite, SiO2 polymorphs, α-quartz, β-quartz, α-tridymite, β-tridymite, α-cristobalite, β-cristobalite, and mixtures thereof. Furthermore, in a particularly preferred embodiment, the shaped body according to the invention can have lithium metasilicate and disilicate as dominant crystal phases. Dominant crystal phases are those crystal phases that are present in the highest weight fractions.In a further preferred possible embodiment, the shaped body is preferably free of spodumene and / or virgilite, wherein their proportion in the shaped body is preferably less than 1 wt.%, particularly preferably less than 0.5 wt.%, in particular less than 0.1 wt.% and especially less than 0.01 wt.%, in each case based on the total weight of the shaped body. The glass-ceramic shaped body according to the invention further preferably comprises silicon dioxide, lithium oxide, potassium oxide, and diphosphorus pentoxide, wherein the following amounts are preferably included in the shaped body according to the invention: i) from 56 to 64 wt.%, preferably from 56 to 59 wt.% SiO2, ii) from 13 to 21 wt.%, preferably from 16 to 20 wt.% Li2O, iii) from 1 to 4 wt.% K. 2O, iv) from 3 to 8 wt.% P2O5 and v) from 8 to 15 wt.%, preferably from 8 to 12 wt.%, in particular from 9 to 11 wt.% ZrO2. In a preferred embodiment, the glass-ceramic shaped body according to the invention comprises aluminum oxide, preferably in an amount of from 0.1 to 10 wt.%, more preferably from 0.5 to 8 wt.%, and most preferably from 1 to 4 wt.%, in each case based on the total weight of the shaped body. This contributes to the stability of the glass-ceramic shaped body. In a further particularly preferred embodiment, the preferably monolithic, glass-ceramic shaped body according to the invention comprises a) from 56 to 64 wt.%, preferably from 56 to 59 wt.% SiO2, b) from 13 to 21 wt.%, preferably from 16 to 20 wt.%, Li2O, c) K2O from 1 to 4 wt.%, d) P2O5 from 3 to 8 wt.%, e) Al2O3 from 0 to 10 wt.%, preferably from 1 to 4 wt.%, f) from 8 to 15 wt.%, preferably from 8 to 12 wt.%, in particular from 9 to 11 wt.-% ZrO2, g) at least one Co metal oxide in an amount of 0.1 to 10 wt.%, preferably 0.1 to 7 wt.%, particularly preferably 1 to 4 wt.%; where the weight specifications are in each case based on the total weight of the glass-ceramic molded body. The Co metal elements are not zirconium and preferably not yttrium, hafnium, and mercury. In a preferred embodiment of the present invention, the molded body according to the invention comprises two or more, particularly preferably 3 or more, in particular 4 or more different Co metal oxides. Furthermore, the glass-ceramic molded body according to the invention is used for dental purposes, i.e. in particular for the restoration of individual teeth, full dentures of the upper and / or lower jaw, dental bridges, locator dentures, and / or dental crowns. Other dental purposes are familiar to the person skilled in the art, so that the application of the glass-ceramic molded body is not limited to the list.The monolithic glass-ceramic molded body according to the invention has an amorphous and a crystalline portion. The amorphous portion is characterized by the fact that the atoms of the chemical compounds therein are not arranged in an ordered structure, but are irregularly arranged. In particular, amorphous material is characterized by the fact that the structure possesses only short-range order, but no long-range order, and behaves isotropic. Furthermore, according to the present invention, "crystalline" means that the atoms in the chemical compounds have an ordered structure with both short-range and long-range order and generate discrete reflections in the X-ray diffraction pattern that can be assigned to the individual structures. This presence of both amorphous and crystalline portions can also be referred to as semi-crystalline to describe the property of this invention.Unless otherwise stated, the weight ratio of the amorphous and crystalline portions as well as the composition of the crystal phases can be determined by Rietveld analysis using Al2O3 as the internal standard. The preferred gradients in the glass-ceramic molded body according to the invention are reflected in particular in a color and translucency gradient. A natural tooth has a color gradient that follows a gradient from the gum (neck of the tooth) to the incisal or chewing surface. In order to replicate this natural image, it has proven advantageous if the gradient follows an axis that runs through the molded body. In a preferred embodiment, the gradient runs perpendicular to the longest dimension of the molded body, preferably approximately 90° to its longitudinal axis. In an alternative preferred embodiment, the gradient runs along the longest dimension of the molded body, preferably parallel to its longitudinal axis.Here, it has been shown that the former gradient is particularly advantageous for machining the molded body with a milling and / or grinding machine. The preferred gradient in the glass-ceramic molded body according to the invention is achieved by the continuously changing weight ratio of amorphous to crystalline portion and the continuously changing percentage weight fraction of zirconium dioxide co-metal oxide crystals. As a result, the gradient described above is not only limited to a gradual change in the crystalline and amorphous portions, but also applies to the proportion of zirconium dioxide crystals in the glass-ceramic molded body.The zirconium dioxide-Co metal oxide in the glass-ceramic molded body according to the invention can be crystallized in such a way that a gradient is created which, in conjunction with the equally gradually changing ratio of the amorphous to the crystalline portion, produces a color and translucency gradient that closely replicates the appearance of natural teeth. The presence of the ZrO2-Co metal oxide crystallites in the nanoscale also ensures that, despite the large difference in refractive index (ZrO2 compared to the rest of the molded body), an aesthetically pleasing material with sufficiently high translucency, even at the cervical level, is achieved. Without being bound to any theory, it is assumed that the presence of nanoscale ZrO2-Co metal crystals contributes to the color and thus to the aesthetics of the molded body. The translucency gradient can be controlled by the varying amorphous portion in the molded body.The preferred monolithic glass-ceramic molded body according to the invention is intended in particular for the production of dental restorations and must accordingly have sufficient strength for processing, but also be stable enough to withstand chewing forces. Therefore, an embodiment is preferred in which the molded body according to the invention has a strength of 200 to 600 MPa, in particular 300 to 600 MPa, determined according to DIN EN ISO 6872:2019 in the 3-point bending test. Furthermore, a preferred embodiment of the molded body according to the invention has a biaxial strength of 300 to 700 MPa, preferably 400 to 600 MPa. In a further preferred embodiment, the molded body according to the invention has a Vickers hardness of 5000 to 8000 MPa, preferably 6000 to 7500 MPa after crystallization, determined according to ISO EN 6507:2018.To achieve a good fit of the dental restoration, it can be manufactured using CAD / CAM processes, which requires that the molded body can be machined subtractively, for example by grinding. To avoid crack formation and crack propagation during machining, the blank according to the invention preferably has a fracture toughness of 1.0 to 3.0 MPa*m½, preferably 1.2 to 2.5 MPa*m½, in each case determined using the SEVNB method. The preferred gradient in the molded body is achieved by the continuously changing weight ratio of amorphous to crystalline portion and / or the proportion of zirconium dioxide co-metal oxide crystals. As a result, the gradient course described above is not limited to a gradual change in the crystalline and amorphous portions, but thus also applies to the proportion of zirconium dioxide crystals in the glass-ceramic molded body.Furthermore, an embodiment is preferred in which the crystalline portion has different phases, with at least two of the phases differing from one another. In this way, the optical properties of the glass-ceramic shaped body according to the invention can be further adapted and optimized. These phases preferably differ with regard to at least one of the following properties: ^ crystal concentration; ^ crystal size; ^ crystal shape; ^ crystal composition; ^ crystal type; ^ crystal structure. The parameters listed influence the optical properties and can therefore be used as adjusting screws for further adjustments. By varying the parameters, the appearance of the shaped body according to the invention can thus be individually adjusted. The glass-ceramic shaped body according to the invention consists of an amorphous and a crystalline portion.In one possible embodiment, the weight ratio of amorphous to crystalline portion ranges from 65:35 to 35:65, preferably from 60:40 to 40:60. Furthermore, the present glass-ceramic molded body can be a monolithic molded body, so that a seamless transition in the color and translucency gradient can be achieved. The molded body according to the invention is characterized in particular by its optical properties. It has surprisingly been found that these develop particularly advantageously when the amorphous portion in the molded body lies within certain ranges. Therefore, an embodiment is preferred in which the amorphous portion in the molded body is 30 to 70 wt.%, preferably 40 to 60 wt.%, in each case based on the total weight of the molded body. In this way, in particular, a translucency gradient can be achieved that corresponds to that of a natural tooth.A particularly preferred embodiment is one in which the composition of the shaped body has from 56 to 59 wt.%, in particular from 56 to 58 wt.% SiO2, in each case based on the total weight. Furthermore, an embodiment is preferred in which the composition of the shaped body has from 16 to 20 wt.% Li2O, based on the total weight of the shaped body. The molar ratio of Li2O:SiO2 in the shaped body is preferably from 1.5 to 2.5, which has proven to be particularly advantageous for forming a lithium silicate glass ceramic. Furthermore, an embodiment is preferred in which the composition of the shaped body has from 0.1 to 15 wt.%, preferably from 0.5 to 10 wt.% and particularly preferably from 1 to 8 wt.% zirconium dioxide in the shaped body, based on the total weight of the crystals of the shaped body. Furthermore, in a preferred embodiment, the shaped body according to the invention can have a proportion, preferably from 0 to 50 vol.-%, preferably 5 to 40 vol.%, in each case based on the total volume of the shaped body, which is almost free of zirconium dioxide crystals and in which the zirconium dioxide remains amorphous in the glass phase. In a further preferred embodiment, the glass-ceramic shaped body according to the invention can comprise CeO2 in an amount of 0.1 to 6 wt.%, particularly preferably 0 to 4 wt.%, in particular 0.5 to 4 or 0.4 to 2.2 wt.% or 1 to 2.5 wt.% in the glass-ceramic, in each case based on the total weight of the glass-ceramic. Surprisingly, it was found that CeO2 as Co metal oxide causes a different color effect of the ZrO2 crystals compared to the rest of the shaped body. In a particularly preferred embodiment, the shaped bodies have an inhomogeneous distribution of the zirconium dioxide-Co-cerium oxide crystals.Particularly preferred shaped bodies have been found to have a gradual progression of the Ce, preferably along an axis leading through the shaped body. 3+ / Ce 4+ This, in combination with the zirconium dioxide, can result in an excellent, aesthetically pleasing color gradient for molded articles, especially for dental restorations, since not only the number and size of the ZrO2 clusters, but also the Ce 3+ / Ce 4+-ratio changes. In a further preferred embodiment, the glass-ceramic shaped body according to the invention can comprise La2O3 in an amount of 0 to 1 wt.%, preferably 0.05 to 0.9 wt.%, in the glass-ceramic, in each case based on the total weight of the glass-ceramic. Furthermore, in a further preferred embodiment, the glass-ceramic shaped body according to the invention can be designed such that lithium disilicate is present as the main crystal phase, preferably in an amount of 51 to 75 wt.%, in particular 52 to 65 wt.% and particularly preferably 53 to 60 wt.%, based on the total weight of the crystal phases in the shaped body. Furthermore, it is possible for the glass-ceramic shaped body according to the invention to be designed such that lithium metasilicate is present as the secondary crystal phase, preferably in an amount of 20 to 49 wt.%, in particular 35 to 48 wt.% and particularly preferably 30 to 47 wt.-%, based on the total weight of the crystal phases in the shaped body. In addition, in a preferred embodiment of the glass-ceramic shaped body according to the invention, lithium phosphate may be present as a secondary crystal phase, preferably in an amount of 5 to 15 wt.%, in particular 6 to 14 wt.%, and particularly preferably 7 to 13 wt.%, based on the total weight of the crystal phases in the shaped body.The present invention further provides a process for producing the glass-ceramic molded body according to the invention, comprising the following steps: a) providing a glass-ceramic blank comprising zirconium dioxide and one or more Co metal oxide(s), wherein the blank can form crystals of zirconium dioxide incorporating one or more Co metal oxide(s) by heat treatment, b) optional heat treatment, preferably at a temperature of 500°C to 600°C, for preferential nuclei formation, c) heat treatment at a temperature of 500°C to 850°C, preferably at a temperature of 550°C to 780°C, in particular 600 to 700°C for preferential pre-crystallization, and d) inhomogeneous heat treatment. The glass-ceramic blank in step a) can be produced by melting the previously described constituents for the molded bodies according to the invention.As is known to those skilled in the art, a glass-ceramic is produced by melting the starting components in a first step and obtaining a glass from this melt. The subsequent crystallization transforms the glass melt into a glass-ceramic. The glass-ceramic blank described in step a) essentially consists of a glass melt of the starting components. The glass blank can then preferably be heated to a temperature range of 450 to 600°C in order to form crystal nuclei. The nucleation step usually takes place over a period of more than 30 minutes, preferably more than 60 minutes, in particular 60 to 240 minutes. The heat treatment for pre-crystallization in step c) typically takes place over a period of more than 30 minutes, preferably more than 60 minutes, in particular 60 to 600 minutes, for example 70 to 250 minutes.Pre-crystallization enables ZrO2 to crystallize in the form of nanometer-sized crystallites at low final temperatures and long holding times. In the prior art, it was considered a problem that glass ceramics containing ZrO2 crystallize at high temperatures and the glass ceramics suddenly become opaque. The inhomogeneous heat treatment leads to the formation of a temperature gradient that preferably runs along a vertical axis on the heat source. In a preferred embodiment, the inhomogeneous heat treatment takes place in a first region of the blank at a temperature T1 and a second region of the blank at a temperature T2, wherein the temperature difference between temperature T1 and temperature T2 is at least 10 °C, preferably at least 20 °C, more preferably at least 30 °C or at least 40 °C or at least 45 °C or more and / or wherein temperature T2 is preferably higher than temperature T1.Preferably, the temperature T1 is from 600°C to 750°C, preferably in the range from 650°C to 720°C and / or the temperature T2 is in a range from 700°C to 900°C, preferably from 740°C to 860°C, where T2 is higher than T1. In a preferred embodiment, the inhomogeneous heat treatment is carried out by at least partially introducing the blank, preferably in a form-fitting manner, into a heating chamber and heating the heating chamber, optionally gradually increasing the temperature in the heating chamber in a further step, and / or the heat treatment is carried out by direct or indirect contact of the blank with a heat source, where the heat source is preferably a hot plate. A further subject matter is the use of the shaped body according to the invention for the production of dental restorations.A further subject matter is a method for producing a dental restoration, wherein the molded body according to the invention has been subjected to at least one inhomogeneous heat treatment, is provided, and is subjected to a further, isothermal heat treatment. Furthermore, it was surprisingly found that a preferred profile of the ratio of glass phase to crystalline phase in the glass-ceramic molded body according to the invention, as well as different domains of the crystal phase, can be achieved through special heat treatments.Therefore, a further preferred subject of the present invention is a process for producing a glass-ceramic shaped body according to the invention, which comprises the following steps: a) providing a glass-ceramic blank which can form crystals by heat treatment, b) first homogeneous heat treatment preferably at a temperature of 500 °C to 600 °C for the preferential formation of nuclei, c) second homogeneous heat treatment at a temperature of 580 °C to 720 °C, wherein this temperature is preferably higher than the temperature in step b), in particular at a temperature of 610 °C to 720 °C for preferential pre-crystallization and d) inhomogeneous heat treatment for the preferential formation of a preferably weight gradient of the zirconium dioxide-co-metal oxide crystals.The gradient of the zirconium dioxide-co-metal oxide crystals is evident by a gradual increase in weight of the zirconium dioxide-co-metal oxide crystals (concentration) along an axis running through the molded body. The glass-ceramic blank in step a) can be produced by melting the previously described components for the molded bodies according to the invention. As is known to those skilled in the art, a glass-ceramic is produced by melting the starting components in a first step and obtaining a glass from this melt. Subsequent crystallization transforms the glass melt into a glass-ceramic. The glass-ceramic blank described in step a) essentially consists of a glass melt of the starting components. The first homogeneous heat treatment is usually carried out with a holding time of more than 30 minutes, preferably from 30 minutes to 3 hours.The second homogeneous heat treatment is typically carried out with a holding time of more than 30 minutes, preferably from 30 minutes to 3 hours. The inhomogeneous heat treatment in step d) is typically carried out over a period of 15 to 220 minutes. According to the present invention, pre-crystallization is understood to mean a crystallization process that takes place at low temperatures and longer holding times and serves as the basis for the subsequent formation of smaller, in particular nanometer-sized ZrO2-Co metal oxide crystallites, as well as the main crystallization of the primary and secondary phases. The inhomogeneous heat treatment of the blank in step d) preferably comprises at least one or more inhomogeneous heat treatments, which are carried out by establishing an isothermal and / or non-isothermal heat gradient.In order to achieve the inhomogeneous heat treatment of the blank, preferably a first region of the blank is treated at a temperature T1 and a second region of the blank is treated at a temperature T2, wherein the temperature difference between temperature T1 and temperature T2 is at least 10 °C, preferably at least 20 °C, more preferably at least 30 °C or at least 40 °C or at least 45 °C or more and / or the temperature T2 is preferably higher than the temperature T1. The temperature T1 is preferably from 600 °C to 750 °C, particularly preferably in the range from 650 °C to 720 °C, while the temperature T2 is preferably from 700 °C to 900 °C, particularly preferably from 740 °C to 860 °C, wherein T2 is higher than T1. The inhomogeneous heat treatment of the blank is preferably carried out by contact with a heat source, wherein the contact can be direct or indirect. The heat source can be a warming room or a heated surface.The inhomogeneous heat treatment preferably imparts a thermal gradient to the shaped body, which preferably runs along an axis through the shaped body. In a preferred embodiment, the heat treatment is carried out by at least partially placing the blank, preferably in a form-fitting manner, into a heating chamber and heating the heating chamber. In this way, targeted heat treatment of individual regions of the blank can be achieved. The heating chamber is preferably a thermally conductive material with a thermal conductivity of 50 to 500 W / (m*K), preferably 150 to 450 W / (m*K), determined by heat flow calorimetry. The thermally conductive material is preferably selected from the group consisting of non-oxide ceramics, preferably selected from Si3N4, silicon carbide and aluminum nitride, or metals. The heating of the heating chamber can be adjusted depending on the intensity.In a preferred embodiment, the heating chamber is therefore heated indirectly by the new ambient atmosphere or, more preferably, directly through contact with a heat source. Alternatively, and most preferably, the heat treatment of the blank can also be carried out using a heatable base onto which the blank is placed. Here, too, the contact can be indirect or direct, depending on the desired intensity. Therefore, an embodiment is preferred in which the heatable base is a heating plate onto which the blank is placed. Alternatively, the heatable base can be a heat-conducting material that is heated, for example, via a heating plate, so that the blank is heated indirectly. Both types of heat treatment can also be combined.Thus, in a preferred method, the heat treatment is carried out in such a way that it takes place by the blank being at least partially, preferably in a form-fitting manner, introduced into a heating chamber and the heating chamber is heated, wherein if appropriate the temperature in the heating chamber is gradually increased in a further step, and / or the heat treatment is carried out by direct or indirect contact of the blank with a heat source, wherein the heat source is preferably a hot plate. Figure 7 shows an example of a heating scheme for which the following heating conditions are applied to the previously pre-crystallized blanks. For this purpose, the blanks are placed on a heatable base in a furnace. The furnace and base are heated at the heating rate HR 1, wherein the furnace is set to a temperature T1 and the temperature T1 is maintained for the duration t1.The support is set to temperature T2 and held there for duration t2. After duration t1 has elapsed, the furnace environment is set to temperature T3 at heating rate HR2 and held there for duration t3. The blanks are then cooled to room temperature (25 °C) without control. The blanks are placed on the support in the furnace and their undersides are in direct contact with the support, so that, starting from the temperature T2 of the support, a temperature gradient can be established in the blank between the furnace ambient temperature T1 and T2 or T3. In general, this embodiment applies that T1 <T2, T3<=T2 und T1<T3 ist. Bevorzugt sind auch t3<t2 und t1> t3 The temperature T2 and the holding time t2 can be used to adjust the opacity and chroma of the cervical and dentin areas.In principle, the longer the holding time and the higher the temperature during this heating, the more chromatic and opaque the neck area. The gradient can be adjusted using the temperature T1 and holding time t1 (at constant T2 and t2). The difference between T1 and T2 sets how far the gradients extend towards the incisal edge (the severity of the gradients (strong-weak) can also be adjusted). The translucency and brightness of the incisal area can be adjusted using the temperature T3 and holding time t3 (at constant T1, t1, T2 and t2). The present invention further relates to the use of the shaped body according to the invention for producing dental restorations. The shaped body according to the invention is preferably used for producing dental restorations, preferably in the anterior tooth region, in particular veneers, crowns, inlays and onlays.Furthermore, the glass-ceramic molded body according to the invention is used in particular for the restoration of individual teeth, full dentures of the upper and / or lower jaw, dental bridges, and locator dentures. Other dental purposes are familiar to the person skilled in the art, so the application of the glass-ceramic molded body is not limited to this list. The present invention further provides a method for producing a dental restoration using the monolithic glass-ceramic molded body according to the invention. Within the scope of the method according to the invention, a molded body according to the invention that has been subjected to at least a first inhomogeneous heat treatment is provided and subjected to a further, isothermal heat treatment. The temperature of this isothermal heat treatment is preferably between 730 and 850°C, particularly preferably in the range between 750 and 820°C.The holding time at this temperature is preferably between one and 60 minutes, particularly preferably between five and 30 minutes. This process step can optionally also be directly linked to the first inhomogeneous heat treatment in the same furnace firing. In a preferred embodiment, the method according to the invention further comprises machining the shaped body to form the geometric shape of the dental restoration, preferably before the shaped body is subjected to further heat treatment. The present invention is described in more detail with reference to the following examples and figures, which, however, are in no way to be understood as a limitation of the inventive concept. Figure 1 shows the crystal structure and the size of the ZrO2 crystal clusters of the glass-ceramic shaped body according to the invention at the tooth neck, which was recorded using SEM. Figure 2 shows a ZrO2 cluster according to the invention with the nanocrystalline ZrO2 crystals.Figure 3 shows the change in the crystal structure of the glass-ceramic molded body according to the invention from the tooth neck (1) to the tooth incisal edge (12), which was recorded using SEM and XRD. Figure 4 shows exemplary color measurements of various regions (platelet (1) tooth incisal edge to platelet (5) tooth neck) of the glass-ceramic body according to the invention, which were characterized by the color coordinate (measured by reflection) and ΔE. Figure 5 shows the crystalline composition of the crystal phase of the glass-ceramic molded body according to the invention from the tooth incisal edge (1) to the tooth neck (7), which was determined by Rietveld analysis, as well as a color measurement by transmission over a wavelength range of 360-750 nm.Figure 6 shows the crystalline composition of the entire molded body (crystal phase and glass phase) of the glass-ceramic molded body according to the invention from the tooth incisal (1) to the tooth neck (7), which was determined by Rietveld analysis, as well as a color measurement via transmission over a wavelength range of 360-750 nm. Figure 7 shows, by way of example, the temperature profiles of the process for producing a glass-ceramic molded body according to the invention. Figure 8a shows a TEM image with zirconium dioxide-cerium oxide crystals. Figure 8b shows a TEM image with zirconium dioxide-terbium oxide crystals. Figure 8c shows a TEM image with zirconium dioxide crystals. Figure 8d shows a TEM image with zirconium dioxide-vanadium oxide crystals. Figure 9a shows a TEM image with tetragonal ZrO2. Figure 9b shows an exemplary electron diffraction pattern and proves that the ZrO2 is present in the tetragonal crystal structure.Figure 10 shows, using an electron loss energy spectroscopy diagram, that the proportion of incorporated f-elements increases from top to bottom (with increasing ZrO2 cluster size). Likewise, there is a higher Ce concentration in the cervical region. 3+ / Ce 4+-ratio than in the middle area. The trivalent cerium shows a color effect, the tetravalent does not. In the area of ​​the outermost cutting edge, no Ce or Tb signal is detectable. Figure 11 shows a schematic diagram of a monolithic molded body according to the invention with a cutting area and a neck area. Figure 12 shows a schematic diagram of the preparation of a molded body according to the invention into platelets that are used for measurement. Figure 13a shows, using the aforementioned Example VIII as an example, a preparation of 12 platelets sawn out of a 12 mm thick molded body and measured by SEM examination (Fig. 13c). Platelet 1 is the platelet at the neck piece (this was closest to the inhomogeneous heat source (base)) up to the cutting edge (platelet 12 with the greatest distance from the inhomogeneous heat source (base)). From 1 to 12, the translucency increases and the chroma decreases, just like natural teeth. Fig.Figure 13b shows an artificial tooth milled from Example VIII with a natural color and translucency gradient. Examples: Exemplary compositions for the glass-ceramic molded body according to the invention. The data are given in percent by weight: Chemical ZS I ZS II ZS III ZS IV ZS V Compound SiO2 58.13 58.89 58.38 58 58.13 P2O5 5.81 5.89 5.84 5.8 5.81 Al2O3 1.94 1.96 1.95 1.93 1.94 Li2O 18.41 18.65 18.49 18.37 18.41 K2O 1.94 1.96 1.95 1.93 1.94 ZrO2 10 10 10 10 10 CeO2 2.13 1.57 1.75 1.74 1.74 La2O3 0.1 0.1 0.1 0.1 0.1 Y2O3 - - - 0.48 - V2O5 0.1 - 0.1 0.19 0.48 Tb4O7 1.45 0.98 1.46 1.45 1.45 Table 1 shows the measured reflection for four glass-ceramic molded bodies according to the invention. This is reflected as a color gradient from cutting edge to neck and is given in the characteristic L*a*b values. Table 1: Color values ​​for the various regions of the glass-ceramic molded body according to the invention Cutting edge Neck wt.-% Li2Si2O5 Li2SiO3 Li3PO4 MexZr1-xO2 Li2Si2O5 Li2SiO3 Li3PO4 MexZr1-xO2 Example 50 38 11 1 49 37 11 3 V Example 50 36 14 - 50 33 16 1 VI Example 49 37 14 - 48 33 18 1 VII Example 49 35 16 - 48 32 16 2 VIII Cutting edge Neck - L* a* b* L* a* b* ΔE Example I 74.2 2.9 16.6 76.9 3.9 21.9 6.04 Example II 71.3 2.2 13.1 74.0 3.25 19.6 7.12 Example III 72.1 2.3 14.4 75.4 4.13 19.4 6.28 Example IV 74.5 3.4 19.2 76.0 3.04 21.5 2.77 Table 2 shows the result of the Rietveld analysis of the molded bodies with MgO as the internal standard, whereby four equal-sized sections A to D were prepared and measured at different locations on the molded body. The proportions are given in wt.%. In order to further illustrate the colors and color differences, platelets were produced according to the glass-ceramic molded body according to the invention. These platelets, shown in Fig. 4, were again examined with regard to their color coordinates. d = 1.60 mm color coordinates (± 0.02mm) L from plate 1 71.36 0.73 11.37 plate 2 71.93 0.80 11.95 plate 3 72.87 1.01 13.31 plate 4 73.66 1.60 16.36 plate 5 75.31 2.81 20.06.

[0002] d = 1.60 mm Reference color coordinate X 1 1 1 1 2 2 2 3 3 4 (± 0.02 mm) Color coordinate Y 2 3 4 5 3 4 5 4 5 5 Platelet 1 ΔE (YX) 1 xxxxxx 8 Platelet 2 ΔE (YX) . 0 6 4 . xxx 2 9 7 4 tiles 3 ΔE (YX) x . 5 5 6 . 7 . 1 0 8 x 9 . 4 5 1 0 9 xx . 2 4 Plates 4 ΔE (YX) x 8 . 3 . 7 3 2 plates 5 ΔE (YX) xxxxxx .4 In order to illustrate the translucency profile of the preferred embodiment of the glass-ceramic molded body according to the invention, platelets were prepared and compared with each other (see Fig. 5): Sample weight with 30 wt% Al2O3 as internal standard Powder Transmission Li2Si2O5 Li2SiO3 Li3PO4 MexZr1-xO2 amorphous [%] Platelet 1 22.7 18.1 2.2 - 57 39.5 Platelet 2 23.6 18.5 3.0 - 54.8 38.1 Platelet 3 22.2 19.4 4.2 - 54.3 35.9 Platelet 4 22.8 19.3 4.8 - 53.1 34.5 Platelet 5 23.8 20.0 5.0 0.5 50.7 32.8 Platelet 6 25.2 18.4 6.8 0.8 48.8 29.3 Plates 7 24.8 19.7 8.3 1.3 46.0 24.2

[0003] Furthermore, the platelets were examined in another preferred embodiment (Fig. 6) for their morphology and lithium crystal content: d = 1.00mm sample weight with 25wt% Al2O3 as internal standard (± 0.02mm) Li2Si2O5 Li2SiO3 Li3PO4 MexZr1-xO2 amorphous Transmission [%] Platelet 1 23.8 15.5 5.0 - 55.8 42.1 Platelet 2 23.4 15.4 6.8 - 54.4 40.1 Platelet 3 24.4 16.7 6.9 - 52.0 39.3 Platelet 4 25.9 16.6 8.1 - 49.5 36.9 Platelet 5 25.7 16.6 8.5 0.4 48.9 33.9 Platelets 6 25.7 17.1 9.6 0.7 47.0 29.4 Platelets 7 25.7 17.4 10.4 1.4 45.1 26.1 Further exemplary production processes for glass-ceramic shaped bodies according to the invention.The compositions are given in percent by weight: Table A: Chemical Example i) Example ii) Compound SiO2 58.38 58.89 P2O5 5.84 5.89 Al2O3 1.95 1.96 Li2O 18.49 18.65 K2O 1.95 1.96 ZrO2 10 10 CeO2 1.75 1.57 La2O3 0.1 0.1 Y2O3 - - V2O5 0.1 - Tb4O7 1.46 0.98 The compositions shown in examples i) and ii) are melted and blanks are produced. The dimensions are 12 mm x 14 mm x 18 mm. After cooling, the blanks are heated for 2 hours at 550 °C to form nuclei and then heated for another 2 hours in a furnace at 660 °C for pre-crystallization. According to the heating scheme shown in Figure 7, the following heating conditions are applied to the previously pre-crystallized blanks. The blanks are placed on a heated support in a furnace.The furnace and base are heated at heating rate HR1, with the furnace being set to temperature T1 and temperature T1 being maintained for time t1. The base is set to temperature T2 and maintained there for time t2. After time t1 has elapsed, the furnace environment is set to temperature T3 at heating rate HR2 and maintained for time t3. The blanks are then cooled to room temperature (25°C) in an uncontrolled manner. The blanks are placed on the base in the furnace and their underside is in direct contact with the base so that, starting from temperature T2 of the base, a temperature gradient can develop in the blank between the furnace environment temperature T1 and T2 or T3. The following parameters were set for the blanks according to example composition i) from Table A (Examples I to VII).For Example VIII, composition ii) was used: Table B: Example HR1 T1 t1(min) T2(°C) t2(min) HR2 T3(°C) t3(min) (°C / min) (°C) (°C / min) I 5 660 57 775 75 10 775 15 II 5 660 85 760 105 10 760 15 III 5 660 100 760 120 10 760 15 IV 5 660 72 775 90 10 775 15 V 5 660 58 775 75 10 760 15 VI 5 675 66 770 85 10 760 15 VII 5 700 64 770 85 10 750 15 VIII 5 660 57 775 75 10 775 15 The resulting glass-ceramics I to VIII exhibit a color and translucency gradient similar to the natural color and translucency gradient of teeth. Color measurement and crystal phase determination according to Rietvled for glass-ceramics I to IV were performed on the area of ​​the blank in contact with the substrate (neck / cervical) and the area of ​​the blank furthest from the substrate (cutting edge, incisal) (see Fig. 11).The measurement results can be found in the following Tables C and D: Table C: Color measurement of glass ceramics I to IV Table D: XRD - measurement of the crystal phases of glass ceramics I to IV (corresponds to Examples 1 to 4 in the table below). The crystal phases are summed to 100 wt. %, excluding the glass phase. For the glass ceramic according to Example VII, the heat-treated glass ceramic molded body according to the invention was sawn into platelets along a main axis leading away from the base (hottest point) along the developed temperature gradient, which are arranged orthogonal to the main axis (from neck to cutting edge) (see Fig. 12). The platelets were analyzed for their transmittance and with an XRD measurement to determine the crystal and amorphous fractions.The results of Example VII are shown in Table E below: Table E: It can be seen that a color gradient develops along the temperature gradient, which is attributable to zirconium dioxide incorporating one or more Co metal oxide(s) (MexZr1-xO2). A concentration gradient of crystallites made of zirconium dioxide with Co metal oxides forms in the glass-ceramic molded body along an axis that is perpendicular to the base (heat source for the inhomogeneous heating) and runs through the molded body. In a further series of measurements of the molded body according to Example VII, the molded body was sawn into 5 plates in a manner analogous to that described above, and the color values ​​were measured.The measured values ​​are shown in Table F below, with platelet 1 being on the cutting edge and platelet 5 on the neck: Table F: For the molded body according to the invention according to Example VIII, 7 platelets were also sawn out and measured as previously described for Example VII and shown in Fig. 12. The measured data are shown in Table G below: Table G: Figure 13 a shows, by way of example, the above-mentioned Example VIII, a preparation of 12 platelets sawn out of a 12 mm thick molded body and measured by SEM examination (Fig. 13 c). Plate 1 is the plate at the neck (this was closest to the inhomogeneous heat source (base)) up to the cutting edge (plate 12 with the greatest distance to the inhomogeneous heat source (base). From 1 to 12, the translucency increases and the chroma decreases, just like in natural teeth. Fig. 13 b shows an artificial tooth milled from Example VIII with a natural color and translucency gradient.

Claims

Patent claims 1. A glass-ceramic molded body with a color gradient comprising zirconium dioxide crystals incorporating one or more Co metal oxide(s).

2. A glass-ceramic molded body according to claim 1, wherein the crystals are mixed crystals of zirconium dioxide and Co metal oxide(s).

3. A glass-ceramic molded body according to claim 1, wherein the crystals are zirconium dioxide crystals doped with Co metal oxides.

4. A glass-ceramic molded body according to any one of the preceding claims, wherein the Co metal oxide is selected from the group consisting of the oxides of the d and f elements of the periodic table.

5. A glass-ceramic molded body according to any one of the preceding claims, wherein the Co metal oxide is selected from the group consisting of cerium oxide, terbium oxide, praseodymium oxide, erbium oxide, neodymium oxide, europium oxide, iron oxide, vanadium oxide, manganese oxide, and mixtures thereof.A glass-ceramic molded body according to one of the preceding claims, wherein the crystals of zirconium dioxide, in which one or more Co metal oxides are incorporated, have a size of a maximum of 1000 nm, preferably a maximum of 500 nm.

7. A glass-ceramic molded body according to one of the preceding claims, wherein the molded body is a monolithic molded body for dental restorations.

8. A glass-ceramic molded body according to one of the preceding claims, wherein the molded body has an amorphous portion and a crystalline portion, and the molded body has an inhomogeneous distribution of amorphous and crystalline portions.

9. A glass-ceramic molded body according to one of the preceding claims, wherein the molded body has a gradually changing weight ratio of amorphous to crystalline fraction, wherein the gradient occurs along an axis running through the molded body.

10. A glass-ceramic molded body according to one of the preceding claims, wherein the molded body has a gradually changing weight proportion of zirconium dioxide crystals incorporating one or more Co metal oxides, wherein the gradient occurs along an axis running through the molded body.

11. A glass-ceramic molded body according to one of the preceding claims, wherein the molded body additionally comprises lithium metasilicate and / or lithium disilicate crystals.

12. A glass-ceramic molded body according to one of the preceding claims, wherein the molded body has lithium disilicate as the main crystal phase. 13.Glass-ceramic shaped body according to one of the preceding claims, wherein the shaped body comprises SiO2 in an amount of preferably 50 to 70 wt.%.

14. Glass-ceramic shaped body according to one of the preceding claims, wherein the shaped body comprises Li2O in an amount of preferably 10 to 25 wt.%.

15. Glass-ceramic shaped body according to one of the preceding claims, wherein the shaped body comprises K2O in an amount of preferably 0.5 to 6 wt.%.

16. Glass-ceramic shaped body according to one of the preceding claims, wherein the shaped body comprises P. 2 O 5 in an amount of preferably 2 to 12 wt.%.

17. A glass-ceramic molded body according to any one of the preceding claims, wherein the molded body comprises P2O5 in an amount of preferably 2 to 12 wt.%.

18. A glass-ceramic molded body according to any one of the preceding claims, wherein the molded body comprises ZrO2 in an amount of preferably 8 to 15 wt.%.

19. A glass-ceramic molded body according to any one of the preceding claims, wherein the molded body comprises Co metal oxide(s) in an amount of preferably 0.1 to 10 wt.%.

20. A glass-ceramic molded body according to any one of the preceding claims, wherein the molded body comprises the following components: i) from 56 to 64 wt.%, preferably from 56 to 59 wt.% SiO2, ii) from 15 to 21 wt.%, preferably from 16 to 20 wt.% Li2O, iii) from 1 to 4 wt.% K2O, iv) from 3 to 8 wt.% P2O5, v) from 8 to 15 wt.%, preferably from 8 to 12 wt.%, in particular from 9 to 11 wt.% ZrO2, and vi) 0.1 to 8 wt.% Co metal oxide. 21.Glass-ceramic shaped body according to one of the preceding claims, wherein the shaped body comprises crystals of the formula MZZr1-ZO2, with M = d- or f-element and z = rational number from 0.0001 to 0.5, preferably from 0.001 to 0.3, particularly preferably from 0.001 to 0.1 or from 0.002 to 0.05 or from 0.003 to 0.

03.

22. Glass-ceramic shaped body according to one of the preceding claims, wherein the shaped body comprises crystals of the formula MZZr1-ZO2, with M selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Lu, Ta, W, Re, Os, Ir, Pt and Au.

23. Glass-ceramic shaped body according to one of the preceding claims, wherein the shaped body comprises crystals of the formula MZZr1-ZO2, with M selected. from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb.

24. A glass-ceramic shaped body according to any one of the preceding claims, wherein the shaped body comprises crystals of the formula MZZr1-ZO2, where M is selected from the group consisting of Ce, Tb, Pr, Er, Nd, Eu, Fe, V, and Mn. 25.A method for producing a glass-ceramic molded body according to one or more of claims 1 to 24, comprising the following steps: a) providing a glass blank comprising zirconium dioxide and one or more Co metal oxide(s), wherein the blank can form crystals of zirconium dioxide incorporating one or more Co metal oxide(s) by heat treatment, b) optional heat treatment, preferably at a temperature of 500°C to 600°C, for preferential nuclei formation, c) heat treatment at a temperature of 500°C to 850°C, preferably at a temperature of 550°C to 780°C, for preferential pre-crystallization, and d) inhomogeneous heat treatment. 26.Method according to claim 25, characterized in that the inhomogeneous heat treatment takes place in a first region of the blank at a temperature T1 and in a second region of the blank at a temperature T2, wherein the temperature difference between temperature T1 and temperature T2 is at least 10 °C, preferably at least 20 °C, more preferably at least 30 °C or at least 40 °C or at least 45 °C or more and / or wherein the temperature T2 is preferably higher than the temperature T1.

27. Method according to at least one of claims 25 or 26, characterized in that the temperature T1 is from 600 °C to 750 °C, preferably in the range from 650 °C to 720 °C and / or the temperature T2 is in a range from 700 °C to 900 °C, preferably from 740 °C to 860 °C, wherein T2 is higher than T1.

28. Method according to at least one of claims 25 to 27, characterized in that the inhomogeneous heat treatment is carried out by the blank being at least partially, preferably in a form-fitting manner, introduced into a heating chamber and the heating chamber being heated, wherein optionally the temperature in the heating chamber is gradually increased in a further step, and / or the heat treatment is carried out by direct or indirect contact of the blank with a heat source, wherein the heat source is preferably a hot plate.

29. Use of a shaped body according to at least one of claims 1 to 24 for the production of dental restorations.

30. Method for producing a dental restoration, wherein the shaped body according to at least one of claims 1 to 24, which has preferably been subjected to at least one inhomogeneous heat treatment, is provided and subjected to a further, isothermal heat treatment.

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