Dental glass ceramic molded bodies

Abstract

The present invention relates to a glass ceramic molded body containing zirconium dioxide crystals incorporating one or more cometallic oxides.

Description

[Technical Field]

[0001] The present invention relates to a glass-ceramic molded body advantageously suited for dental applications, a method for manufacturing the same, and its use for manufacturing dental restorations. [Background technology]

[0002] Modern dental prosthetic materials must meet high stability and aesthetic requirements. Since every dental restoration is unique and individually crafted for each patient, balancing effort and quality plays a crucial role. Recreating an aesthetically pleasing tooth appearance during the manufacturing process is particularly important for patient comfort, meaning the restoration must have a certain degree of translucency or opacity depending on its intended use. In addition, the materials used must withstand the mechanical and chemical stresses encountered during daily eating.

[0003] Due to these demands, glass ceramics have become a common material for manufacturing dental restorations, primarily valued for their strength and aesthetic properties. The crystalline portion not only prevents crack propagation but also reflects and diffracts light in a way different from that seen in conventional glass. This results in a translucency very similar to that of natural teeth, making dental glass ceramics particularly popular in the aesthetic areas of the anterior teeth.

[0004] The Journal of the European Ceramic Society, Vol. 41, No. 11, pages 5728-5739, describes glass ceramic materials containing a zirconium silicate glass matrix, in addition to lithium disilicate, lithium metasilicate, and lithium phosphate. However, it does not mention the use of zirconium dioxide co-crystallites or their application to dental restorations with gradients.

[0005] The Journal of the Mechanical Behavior of Biomedical Materials, Elsevier, Amsterdam, Vol. 105, pp. 1-8, describes processes for plasma sintering and atmospheric pressure sintering of lithium silicate glass ceramics containing ZrO2. These processes enable sintering at low temperatures and the formation of lithium disilicate nanocrystals. However, there is no description of the use of zirconium dioxide cocrystallites or their application to dental restorations with gradients.

[0006] The document "Properties of ZrO2-Enhanced Lithium Disilicate," presented at the Brazilian Congress of Materials Science and Technology (Congresso Brasiliero de Engenharia e Ciencia dos Materiais), discloses glass ceramics containing ZrO2. However, it does not describe zirconium dioxide cocrystallites that form a color gradient in ceramic blocks or dental restorations.

[0007] European Patent Application Publication No. 3772492 (EP3772492A1) describes a glass ceramic whose opacity is increased by multiple heat treatments. However, the formation of zirconium oxide cocrystallites is not disclosed.

[0008] International Publication No. 2017 / 067909 (WO2017 / 067909A1) describes glass ceramics whose optical properties are adjusted by several heating steps. However, the formation of zirconium dioxide cocrystallites is not disclosed.

[0009] European Patent No. 2765119 (EP2765119) describes a dental blank having at least two layers bonded together, of lithium silicate glass, lithium silicate glass with a core, or lithium metasilicate glass ceramic, where each layer is of a different color and each layer is monolithic. It is said that this makes it possible to closely mimic the optical properties of natural tooth material and to achieve shrinkage-free molding.

[0010] International Publication No. 2013 / 086187 (WO2013 / 086187) relates to lithium silicate glass ceramics containing 6-30 wt% Cs2O, 55-80 wt% SiO2, 1-5 wt% Al2O3 and B2O3, 7-16 wt% Li2O, and 1-5 wt% P2O5, where each weight percentage is based on the total weight of the glass ceramic. In particular, it is said that blocks with high transparency can be obtained from this composition.

[0011] European Patent No. 2114348 (EP2114348) describes a ceramic material made of yttrium-stabilized zirconium dioxide containing 58.0 to 74.0 wt% SiO2, 4.0 to 19.0 wt% Al2O3, 5.0 to 17.0 wt% Li2O, 4.0 to 12.0 wt% Na2O, and 0.5 to 6.0 wt% ZrO2, which results in high flexural strength and light transmission. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] European Patent Application Publication No. 3772492 [Patent Document 2] International Publication No. 2017 / 067909 [Patent Document 3] European Patent No. 2765119 [Patent Document 4] International Publication No. 2013 / 086187

Patent Document 5

Non-Patent Document

[0013]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Disclosure of the Invention

Problems to be Solved by the Invention

[0014] Despite the successful aesthetic results achieved so far in glass-ceramic prosthetic materials for dentistry, there remains a need in conventional technology for materials that can reproduce the translucency and color gradient of natural teeth without creating a noticeable transition between the incisal, dentin, and cervical regions. This often leads patients seeking dental restorations to feel self-conscious (embarrassed) about being associated with inadequate oral hygiene. Therefore, there is a high demand for dental restorative materials that closely resemble the appearance of natural teeth. At the same time, glass-ceramic materials must be easy to process and manufacture while exhibiting high strength. [Means for solving the problem]

[0015] Surprisingly, it has been found that glass-ceramic molded bodies containing zirconium dioxide crystals incorporating one or more co-metallic oxides solve the aforementioned problems and are suitable for reproducing natural translucency and tooth color gradients (Farbverlaeufe) without creating a recognizable transition between the incisal, dentin, and cervical regions. At the same time, it can be used to manufacture glass-ceramic molded bodies that are easy to process while possessing high strength.

[0016] The subject matter of the present invention is described in the independent claims. Preferred embodiments are described in particular in the dependent claims.

[0017] The present invention relates to a glass-ceramic molded body containing zirconium dioxide crystals incorporating one or more cometallic oxides. The glass-ceramic molded body according to the present invention preferably has a color gradient and / or a translucency gradient and is particularly suitable as a monolithic molded body for dental restorations.

[0018] Surprisingly, it was discovered that crystals could be induced from an amorphous glass matrix. Here, the crystals consist of zirconium dioxide incorporating one or more cometallic oxides.

[0019] Hereafter, these crystals will also be referred to as "zirconium dioxide cometallic oxide crystals."

[0020] In a preferred embodiment, the crystal consists of zirconium dioxide incorporating one or more cometallic oxides. These are mixed crystals of zirconium dioxide and cometallic oxides.

[0021] In another preferred embodiment, the crystal may be a zirconium dioxide crystal doped with a cometallic oxide.

[0022] In this embodiment, the glass ceramic molded body may contain oxides of element d and / or element f as the cometallic oxide. This can produce a color effect different from that of a molded body that does not contain crystalline components, and can result in a continuous increase in saturation.

[0023] In a preferred embodiment, the cometallic oxide is selected from the group consisting of oxides of d and f elements of the periodic table.

[0024] More preferably, the cometallic oxide is an oxide of an element selected from the group of elements: 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.

[0025] More preferably, the cometallic oxide is an oxide of an element selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Cometallic oxides that produce tooth color (zahnfarbene toene) are particularly suitable. These are well known to those skilled in the art in the field of dental technology.

[0026] When the cometallic 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, particularly good results were obtained with respect to the natural tooth color and shade gradient. In particular, oxides of cerium, terbium, praseodymium, erbium, neodymium, europium, iron, vanadium, or manganese, and mixtures thereof, are incorporated very well into lithium silicate glass ceramics, which can lead to the formation of zirconium dioxide crystals containing one or more of these cometallic oxides.

[0027] These cometallic oxides incorporated into zirconium dioxide particularly enhance the desired shade gradient. Particularly preferred is cerium oxide as the cometallic oxide. This makes it possible to achieve a particularly good shade gradient that closely resembles the color of natural teeth.

[0028] In a preferred embodiment, the cometallic oxide content is preferably 0.1 to 10% by weight. More preferably, the cometallic oxide content is 0.1 to 8% by weight, even more preferably 0.5 to 7% by weight, more specifically 1 to 4% by weight, and particularly 0.4 to 2.5% by weight. Cerium oxide is specifically preferred. These weight values ​​are based on the total weight (Gesamtgewicht) of the glass ceramic molded body.

[0029] In a more preferred embodiment of the present invention, the glass ceramic molded body is defined by formula M z Zr 1-z O2 (or Me x Zr 1-x This also refers to a crystal of O2 (where Me=M and x=z), where M is an element of d or f, and z is a rational number (rationale Zahl) between 0.0001 and 0.5, preferably 0.001 and 0.3, more preferably 0.001 and 0.1, or 0.002 and 0.05, or 0.003 and 0.03.

[0030] 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, the aforementioned formula M z Zr 1-z Crystals of O2 are particularly preferred.

[0031] In addition, M is selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb, the aforementioned formula M z Zr 1-z Crystals of O2 are preferred.

[0032] By using the glass-ceramic formed body according to the present invention, a glass-ceramic having excellent colors and a color gradient particularly suitable for dental applications can be obtained. Here, the formed body contains crystals of the aforementioned formula M z Zr 1-z O2, and M is selected from the group consisting of Ce, Tb, Pr, Er, Nd, Eu, Fe, V, and Mn.

[0033] Although not bound by theory, it is believed that by using the aforementioned cometallic oxides in combination with zirconium dioxide, the cometallic oxides are incorporated into the zirconium dioxide crystal. By crystallizing zirconium dioxide with compounds containing cometallic oxides, particularly oxides of elements d or f, these elements can be incorporated into lattice points or non-lattice points (interstitial spaces) within the ZrO2 lattice. Zirconium dioxide is preferably the host lattice (Wirtsgitter), and its particles, usually zirconium, are substituted by the cometallic, particularly elements d or f. Thus, the term "incorporation (Einbau)" can be understood as meaning that particles of the host lattice (Wirtsgitter) are substituted and / or that particles are inserted into existing gaps in the host lattice. The resulting crystals are known to those skilled in the art as substitutional and / or interstitial solid solutions (feste Loesungen). Therefore, in a preferred embodiment of the present invention, the lattice structure of the zirconium dioxide host lattice can be maintained, so that a tetragonal and / or equiaxed (cubic) mixed crystal is formed, more preferably the above-mentioned formula M z Zr 1-zIt is formed in the form of O2 (where M = d element or f element, z < 0.2, preferably 0.001 to 0.1, or 0.002 to 0.05, or 0.003 to 0.03). According to this theoretical consideration, in the case of homoeotype mixed crystals, it is necessary that the incorporated cometals (particularly the d element and / or f element) have the same crystal structure as ZrO2, but this is not always the case. Furthermore, the color effect in the preferred embodiment of the molded article according to the present invention may be due to so-called heterotype mixed crystals. In such mixed crystals, one crystal type defines the crystal structure of the other. A well-known example is an alloy, also called a binary system, which has limited solubility in the solid state. Therefore, ZrO2, which normally exists as the main component, can define its own crystal structure for cometallic oxides (particularly oxides of d and / or f elements), thereby altering the field of these cations within the lattice compared to the field surrounding them in the glass matrix, potentially resulting in color effects. In addition, the term "incorporation into the crystal" can also be understood as doping (Dotiervorgang) into the ZrO2 crystal phase. As is known from semiconductor technology, adding compounds of the cometallic elements (particularly d and / or f elements) to be incorporated ensures a uniform distribution of atoms within the main crystal phase. One way to describe the crystal incorporated into the main crystal phase is the above formula M z Zr 1-z O2 is the metal selected from elements d and / or f in particular, in the composition of the glass ceramic molded body according to the present invention. In principle, z may be any rational number determined by the region it refers to, preferably 0.001 to 0.3, particularly 0.002 to 0.1, and specifically 0.003 to 0.05. Furthermore, the incorporation of cometallic elements, particularly elements d and / or f, may be regular or random. This can be controlled using the melting temperature and / or crystallization temperature, which are well known to those skilled in the art.

[0034] Depending on the manufacturing process, cometallic oxides can be incorporated into glass-ceramic molded bodies in various forms. Depending on the oxidation time and temperature, compounds of cometallic elements (particularly f and d elements) are incorporated into zirconium dioxide crystals. During the manufacturing or crystallization process, the electron configuration of the contained cometallic elements (particularly f and / or d elements) may change depending on the compound, thereby allowing for control of chrominance.

[0035] Furthermore, in a preferred embodiment, the glass ceramic molded body according to the present invention has the above-mentioned mixed crystal M present as a crystalline phase. z Zr 1-z O2 can be contained in an amount of 0.1 to 15% by weight, particularly 0.2 to 10% by weight, especially preferably 0.2 to 8% by weight, or 0.3 to 4% by weight, based on the total weight of the crystalline phase in the molded body.

[0036] In a more preferred embodiment, the glass ceramic molded body according to the present invention is the mixed crystal M described above. z Zr 1-z It contains O2. Here, the molar ratio n(M) / n(Zr) is 0.0001 to 0.6, preferably 0.001 to 0.55, more preferably 0.04 to 0.4, particularly preferably 0.1 to 0.3, and most preferably 0.1 to 0.2. where n(M) is the number of moles of the cometallic element (particularly d or f) of the corresponding compound, and n(Zr) is the number of moles of Zr derived from the ZrO2 used.

[0037] In a preferred embodiment, the glass-ceramic molded body is a monolithic molded body for dental restorations. The monolithic structure is advantageous because it does not require a layered structure with coordinated intervals between individual layers. Therefore, the glass-ceramic according to the present invention can reliably provide a continuous, seamless color gradient.

[0038] The glass ceramic molded body according to the present invention has an amorphous portion and a crystalline portion, and preferably the molded body has a non-uniform distribution (inhomogene Verteilung) of the amorphous portion and the crystalline portion.

[0039] In a particularly preferred embodiment, the molded article according to the present invention has a stepped weight ratio between amorphous and crystalline portions. This gradient typically occurs along an axis passing through the molded article.

[0040] In particular, regarding the formation of tooth color and shade gradients, molded bodies in which the weight ratio of zirconium dioxide crystals incorporating one or more co-metallic oxides changes in a stepwise manner have been proven to be extremely superior.

[0041] In a preferred embodiment of the present invention, the zirconium dioxide cometallic oxide crystals are non-uniformly distributed in the molded body. Non-uniformity here means, for example, that the concentration of zirconium dioxide cometallic oxide crystals in the molded body differs between two different, but equal-volume regions of the molded body. The difference is macroscopically measurable and may be at least 0.0001%, preferably at least 0.001%, based, for example, on the higher-concentration volume range. The non-uniform distribution can be recognized, for example, by the presence of a color gradient and / or translucency gradient, particularly in a monolithic molded body.

[0042] In a more preferred embodiment, a stepwise change in the weight ratio of zirconium dioxide crystals incorporating a cometallic oxide in a glass-ceramic molded body, preferably monolithic, defines the color effect and / or saturation. Thus, the color gradient and saturation can be induced or controlled in accordance with the stepwise change in the zirconium dioxide cometallic oxide crystals.

[0043] The gradient of the zirconium dioxide cometal oxide crystal, and the ratio of amorphous to crystalline portions, preferentially occur from the cervical region to the enamel (incisal edge), and consequently, the saturation and / or color gradient preferentially increases from the enamel to the cervical region.

[0044] In this invention, saturation (Farbsaettigung) refers to the degree to which a color differs from an achromatic stimulus, regardless of its lightness. For example, white, gray, and black each have a saturation of 0%, while chromatic colors have a saturation of 100%. The terms saturation (Farbsaettigung), chroma (Chromazitaet), color intensity (Farbigkeit), color vibrancy (Farbintensitaet), color depth (Brillanz), and color strength (Farbtiefe) are synonymous and are therefore interchangeable in this invention.

[0045] The color, especially its L * a * b * The material can be characterized by a value or a color code commonly used in the dental industry. Translucency (Transluzenz) refers to the light transmittance of the glass ceramic molded body according to the present invention, which can vary with the gradient. A preferred value for L is 60 to 90, and particularly preferred is 70 to 80. Furthermore, the a value can be selected from the range of 0 to 6, more preferably from 0.1 to 5. For the b value, a value of 5 to 40, preferably 10 to 35, is possible. For all parameters, namely L, a, and b, it is particularly preferable that the cervical value for each parameter is higher than that for the incisal edge of the tooth.

[0046] Furthermore, the color is L * a * b *The difference in values ​​can be characterized by the difference in values. Therefore, the color difference between the cervical area and the incisal edge of the tooth can be described by the difference in the values ​​of L, a, and / or b (hereinafter, ΔL, Δa, and Δb). In a preferred embodiment, ΔL may be 0 to 10, preferably 1 to 5, Δa may be 0 to 5, preferably 0.5 to 2.5, and Δb may be 0 to 15, preferably 6 to 12. The color difference can also be described using ΔE, which is familiar to those skilled in the art. For the color difference and / or difference in hue between the cervical area and the incisal edge of the tooth, ΔE is preferably 0 to 15, more preferably 0.5 to 10.

[0047] To mimic the appearance of natural teeth, it has been proven that the change in the amorphous portion within the molded body should be minimal, and in all cases, the amorphous portion should be minimal. In a preferred embodiment, the amorphous portion in the molded body changes along the gradient by at least 5% by weight, preferably at least 7% by weight, and preferably not exceeding 30% by weight, based on the total volume of the molded body. In a particularly preferred embodiment, the change in the amorphous portion in the molded body along the gradient is in the range of 5 to 30% by weight, preferably 15 to 25% by weight, based on the total weight of the molded body.

[0048] Furthermore, another preferred embodiment of the present invention is a glass-ceramic molded body, preferably having a monolithic nature, which contains zirconium cometallic oxide crystals with a size of up to 1000 nm, preferably 500 nm. This size can be determined by electron microscopy. In the present invention, "crystal (Kristalle)" in this context means a crystal cluster. Thus, zirconium cometallic oxide crystals, also called zirconium cometallic oxide clusters, are composed of several smaller zirconium cometallic oxide (individual) crystals. Surprisingly, it has been found that this small domain size still results in very attractive translucency despite the crystallization of the zirconium cometallic oxide in a preferred embodiment. In this context, domain size and size should be understood to be interchangeable.

[0049] This size, also called domain size, refers to the two-dimensional appearance of the crystal or cluster (see Figure 1). Surprisingly, it has been found that crystals become opaque when they become excessively large. This is likely due to large differences in refractive index. Therefore, the molded body according to the present invention has nanocrystalline ZrO2 cometal oxide (individual) crystals in the cluster (see Figure 2), which are preferably 200 nm or less, more preferably 100 nm or less, or particularly preferably 50 nm or less in size. The size of individual crystals can be determined by X-ray diffraction.

[0050] Furthermore, in a preferred embodiment, the weight ratio of the zirconium dioxide cometallic oxide crystals to the remaining crystalline and amorphous portions changes in a stepwise and continuous manner. Therefore, in a preferred embodiment, the ratio of the present zirconium dioxide crystals to the remaining composition (i.e., the sum of the amorphous and residual crystalline portions) can be increased or decreased.

[0051] A stepwise, and preferably continuous, change in the weight ratio of the zirconium dioxide cometallic oxide crystals to the remaining crystalline and amorphous portions typically occurs along the axis present in the molded body according to the present invention.

[0052] Furthermore, in a preferred embodiment, the glass-ceramic molded body according to the present invention may have a region that is substantially free of crystalline zirconium cometallic oxide. The expression "substantially free of crystalline zirconium cometallic oxide" means that, in a preferred embodiment, the zirconium content is less than 5% by weight, particularly preferably less than 1% by weight, and most preferably less than 0.1% by weight, based on the total weight of the zirconium-free region of the molded body. It is particularly preferable that the molded body has a region that is substantially free of zirconium cometallic oxide in the range of 0 to 30 vol%, 1 to 35 vol%, 5 to 40 vol%, or 10 to 50 vol%, based on the total volume of the molded body. In the glass-ceramic molded body according to the present invention, since the zirconium cometallic oxide, in a preferred embodiment, is responsible for chroma in combination with element d and / or element f, in a preferred embodiment of the present invention, the zone of the glass-ceramic molded body that is free of zirconium cometallic oxide can preferentially be located in the incisal edge region of the tooth.

[0053] The glass ceramic molded body of the present invention preferably contains lithium silicate. Surprisingly, it has been found that the crystallization of zirconium dioxide cometal oxide proceeds very well in a silicate matrix, particularly in a lithium silicate environment. In preferred embodiments, the molded body further contains lithium metasilicate crystals and / or lithium disilicate crystals. Particularly preferably, the molded body has lithium disilicate as the main crystalline phase.

[0054] The glass ceramic molded body of the present invention contains SiO2, preferably 50 to 70% by weight, and more preferably 55 to 65% by weight, based on the total weight of the molded body.

[0055] The glass ceramic molded body of the present invention preferably contains 10 to 25% by weight, more preferably 15 to 22% by weight, of Li2O based on the total weight of the molded body.

[0056] The glass ceramic molded body of the present invention contains, based on the total weight of the molded body, preferably 0.5 to 6% by weight, and more preferably 1 to 5% by weight, of K2O.

[0057] The glass ceramic molded body of the present invention preferably contains 2 to 12% by weight, more preferably 4 to 10% by weight, of P2O5 based on the total weight of the molded body.

[0058] The glass ceramic molded body of the present invention preferably contains 6 to 15% by weight, more preferably 8 to 12% by weight, of ZrO2 based on the total weight of the molded body.

[0059] In a preferred embodiment, the glass ceramic molded body has one or more of the following components. i) 56-64% by weight, preferably 56-59% by weight of SiO2, ii) 15-21% by weight, preferably 16-20% by weight of Li2O, iii) 1-4% by weight of K2O, v) 8-15% by weight, preferably 8-12% by weight, particularly 9-11% by weight of ZrO2, and vi) 0.1 to 8% by weight of a cometallic oxide.

[0060] In a preferred embodiment of the present invention, the molded body according to the present invention is a monolithic glass-ceramic molded body for dental restorations, comprising an amorphous portion and a crystalline portion, and comprising the following: (a) the weight ratio of crystalline portion to amorphous portion, which changes continuously and stepwise, and / or (b) Weight percentage of zirconium dioxide cometal oxide crystals that change continuously and stepwise. Here, the molded body preferably contains lithium disilicate as the main crystalline phase, and the molded body preferably has the following components. i) 56-64% by weight, preferably 56-59% by weight of SiO2, ii) 13-21% by weight, preferably 16-20% by weight of Li2O, iii) 1-4% by weight of K2O, iv) 3-8% by weight of P2O5, and v) 8-15% by weight, preferably 8-12% by weight, especially 9-11% by weight of ZrO2.

[0061] In the manufacture of dental restorative materials, attempts have been made to replicate both mechanical and chemical durability, as well as the appearance of natural teeth. While prior art has described several materials or mixtures that exhibit satisfactory mechanical and chemical resistance, replicating the appearance of natural teeth remains difficult. This is due to the complex appearance of teeth, including their opacity and translucency. Glass-ceramic compositions that are pre-colored before crystallization or manufacture are particularly well-established. However, teeth have a natural color gradient, and the materials used can only represent a single color, thus failing to replicate this gradient.

[0062] As already mentioned, dental restorations are easily recognizable to others, which can cause patients to feel embarrassed or ashamed, and such treatments can also be associated with poor oral hygiene.

[0063] Therefore, there is a need for materials, particularly glass-ceramic compositions, that can be used as molded bodies that can simultaneously provide mechanical and chemical resistance while expressing the natural color gradient of teeth.

[0064] The monolithic glass-ceramic molded body according to the present invention is advantageous in that the weight ratio of crystalline portions to amorphous portions changes continuously and stepwise, and at the same time, the weight percentage of zirconium dioxide cometal oxide crystals in the molded body changes continuously and stepwise. This results in a novel color gradient while maintaining a gradient of translucency.

[0065] The gradual and continuous changes preferably occur along the axis passing through the molded body according to the present invention.

[0066] According to the present invention, the glass-ceramic molded body has a crystalline component consisting of zirconium dioxide cometallic oxide. However, in addition to the zirconium dioxide cometallic oxide crystals, other crystals may be present in the glass-ceramic molded body. For example, lithium disilicate is preferred, and it may be present particularly as the main component of the crystalline phase.

[0067] In the spirit of this invention, the main component of the crystalline phase means that it has the highest crystal content (weight %) compared to other crystals with different chemical compositions within the molded body. Preferably, the main component accounts for more than 30% by weight, more preferably more than 40% by weight, and especially more than 50% by weight, based on the total weight of all crystals. In particular, lithium disilicate is present at a higher weight fraction than lithium metasilicate. Preferably, the weight ratio of lithium disilicate to lithium metasilicate is greater than 1:1, especially greater than 1.1:1 or greater than 1.2:1.

[0068] Preferably, additional other crystals can be selected from the group consisting of lithium metasilicate, lithium phosphate, lithium aluminum oxide, spodumene, vergilite, keytite, SiO2 polymorphs, α-quartz, β-quartz, α-tridymit, β-tridymit, α-cristobalite, β-cristobalite, and mixtures thereof. Furthermore, in a particularly preferred embodiment, the molded article according to the present invention may have lithium metasilicate and lithium disilicate as dominant crystalline phases. "Dominant crystalline phase" refers to the crystalline phase that is present in the highest proportion by weight. In yet another preferred embodiment, the molded article preferably does not contain spodumene and / or vergelite, and the proportion of them in the molded article is preferably less than 1% by weight, more preferably less than 0.5% by weight, particularly less than 0.1% by weight, and especially less than 0.01% by weight, based on the total weight of the molded article.

[0069] The glass ceramic molded body according to the present invention more preferably contains silicon dioxide, lithium oxide, potassium oxide, and phosphorus pentoxide, and according to the present invention, the molded body preferably contains the following amounts. i) 56-64% by weight, preferably 56-59% by weight of SiO2, ii) 13-21% by weight, preferably 16-20% by weight of Li2O, iii) 1-4% by weight of K2O, iv) 3-8% by weight of P2O5, and v) 8-15% by weight, preferably 8-12% by weight, especially 9-11% by weight of ZrO2.

[0070] In a preferred embodiment, the glass-ceramic molded body according to the present invention contains, in any case, preferably 0.1 to 10% by weight, more preferably 0.5 to 8% by weight, and most preferably 1 to 4% by weight of aluminum oxide, based on the total weight of the molded body. This contributes to the stability of the glass-ceramic molded body.

[0071] In another particularly preferred embodiment, the glass-ceramic molded body according to the present invention, preferably an essentially monolithic one, includes the following: a) 56-64% by weight, preferably 56-59% by weight of SiO2, b) 13-21% by weight, preferably 16-20% by weight of Li2O, c) 1-4% by weight of K2O, d) 3-8% by weight of P2O5, e) 0-10% by weight, preferably 1-4% by weight of Al2O3, f) 8-15% by weight, preferably 8-12% by weight, particularly 9-11% by weight of ZrO2, g) 0.1 to 10% by weight, preferably 0.1 to 7% by weight, more preferably 1 to 4% by weight, at least one cometallic oxide, The weights shown here are all based on the total weight of the glass-ceramic molded body.

[0072] The cometallic element is not zirconium, and preferably not yttrium, hafnium, or mercury.

[0073] In a preferred embodiment of the present invention, the molded article according to the present invention has two or more, particularly preferably three or more, and especially four or more different cometal oxides.

[0074] Furthermore, the glass-ceramic molded bodies according to the present invention are used for dental purposes, particularly for single tooth restorations, maxillary and / or mandibular complete dentures, dental bridges, locator dentures, and / or dental crowns. Since other dental purposes are known to those skilled in the art, the uses of the glass-ceramic molded bodies are not limited to this list.

[0075] The monolithic glass-ceramic body according to the present invention has amorphous and crystalline components. The amorphous component is characterized in that the compound atoms within it are not arranged in a regular structure, but rather exist irregularly. In particular, amorphous materials are characterized in that their structure has only short-range order and no long-range order, and behaves isotropically. Furthermore, in the present invention, "crystalline" means that the atoms in the compound exhibit a regular structure with both short-range and long-range order, and that discrete reflections attributable to individual structures are produced in the X-ray diffraction pattern. The presence of both amorphous and crystalline portions can also be expressed as "semi-crystalline" to explain the properties of the present invention.

[0076] Unless otherwise specified, the weight ratio of amorphous to crystalline portions, and the composition of the crystalline phase, can be determined by Rietveld analysis using Al2O3 as the internal standard.

[0077] The preferred gradients in the glass-ceramic molded body according to the present invention are particularly pronounced in terms of color gradients and translucency gradients. Natural teeth exhibit a color gradient along the gradient from the gingiva to the incisal edge or occlusal surface. To reproduce this natural appearance, it has been found advantageous for the gradient to be along an axis running through the molded body. In a preferred embodiment, the gradient extends perpendicular to the maximum dimension of the molded body, preferably at about 90° to its longitudinal axis. In another preferred embodiment, the gradient runs along the maximum dimension of the molded body, preferably parallel to its longitudinal axis. In machining the molded body by cutting and / or grinding machines, the former path has been found to be particularly advantageous.

[0078] The preferred gradient in the glass ceramic molded body according to the present invention is achieved by continuously changing the weight ratio of amorphous to crystalline components and the weight percentage of zirconium dioxide cometal oxide crystals. This means that the above-mentioned gradient is not merely limited to stepwise changes in crystalline and amorphous components, but also applies to the fraction of zirconium dioxide crystals in the glass ceramic molded body.

[0079] The zirconium cometallic oxide in the glass ceramic molded body according to the present invention, when crystallized, combined with a similarly stepwise changing ratio of amorphous and crystalline components, can produce a color gradient and translucency gradient that faithfully mimics the appearance of natural teeth. The presence of ZrO2 cometallic oxide microcrystals in the nanoscale region ensures that the material is aesthetically superior with sufficiently high translucency even in the cervical region, despite a large difference in refractive index (of ZrO2 compared to other parts of the molded body). Although not bound by theory, it is thought that the presence of nanoscale ZrO2 cometallic oxide crystals contributes to the coloration and, consequently, the aesthetics of the molded body. The translucency profile can be controlled by changing the amorphous content in the molded body.

[0080] The preferred monolithic glass-ceramic molded body according to the present invention is particularly used in the manufacture of dental restorations and therefore needs to have sufficient strength for processing and sufficient stability to withstand chewing forces. For this reason, embodiments of the molded body according to the present invention that have a strength of 200 to 600 MPa, particularly 300 to 600 MPa, as measured by a three-point bending test in accordance with DIN EN ISO 6872:2019 are preferred. Furthermore, preferred embodiments of the molded body according to the present invention have a biaxial strength of 300 to 700 MPa, preferably 400 to 600 MPa. In another preferred embodiment, the molded body according to the present invention has a Vickers hardness of 5000 to 8000 MPa, preferably 6000 to 7500 MPa, as measured in accordance with ISO EN 6507:2018 after crystallization.

[0081] To obtain good fit for dental restorations, the restorations can be manufactured using a CAD / CAM process, which requires that the workpiece be capable of being removed by processes such as grinding. To avoid the occurrence and propagation of cracks during processing, the blank according to the present invention is measured by the SEVNB method and in all cases has a pressure of 1.0 to 3.0 MPa·m. 1 / 2 Preferably 1.2 to 2.5 MPa·m 1 / 2 It is preferable that it has fracture toughness.

[0082] A favorable gradient in the molded body is achieved by continuously changing the weight ratio of amorphous to crystalline components and / or the proportion of zirconium dioxide cometal oxide crystals. This means that the transition of the gradient described above is not limited to merely stepwise changes in crystalline and amorphous components, but also applies to the fraction of zirconium dioxide crystals in the glass ceramic molded body.

[0083] In addition, embodiments are preferred in which the crystalline components have different phases, and at least two of these phases are different from each other. This allows for further adaptation and optimization of the optical properties of the molded article according to the present invention. Preferably, these phases differ in at least one of the following properties. ·Crystal concentration • Crystal size • Crystal shape • Crystal composition • Types of crystals • Crystal structure

[0084] These listed parameters affect the optical properties and can therefore be used as adjustment levers for further modification. Thus, by changing these parameters, the appearance of the molded article according to the present invention can be individually adjusted.

[0085] The glass-ceramic molded body according to the present invention is composed of amorphous and crystalline components. In one possible embodiment, the weight ratio of amorphous to crystalline components is in the range of 65:35 to 35:65, preferably 60:40 to 40:60. Furthermore, this glass-ceramic molded body can be a monolithic molded body, thereby enabling a seamless transition between color and translucency.

[0086] The molded articles according to the present invention are characterized in particular by their optical properties. Surprisingly, it has been found that the optical properties are formed in a very favorable manner when the amorphous components of the molded article are within a specific range. Therefore, embodiments in which the proportion of amorphous material in the molded article is 30 to 70% by weight, preferably 40 to 60% by weight, based on the total weight of the molded article, are preferred. This makes it possible to achieve a transition in translucency that corresponds particularly to natural teeth.

[0087] A particularly preferred embodiment is one in which the composition of the molded article contains 56 to 59% by weight, particularly 56 to 58% by weight, of SiO2, based on the total weight.

[0088] Furthermore, embodiments in which the composition of the molded body contains 16 to 20% by weight of Li2O based on the total weight of the molded body are preferred.

[0089] The molar ratio of Li2O:SiO2 in the molded article is preferably 1.5 to 2.5, which has been found to be particularly advantageous for the formation of lithium silicate glass ceramics.

[0090] Furthermore, embodiments in which the composition of the molded body contains 0.1 to 15% by weight, preferably 0.5 to 10% by weight, and particularly preferably 1 to 8% by weight of zirconium dioxide, based on the total weight of the crystals in the molded body, are preferred.

[0091] In addition, in a preferred embodiment, the molded article according to the present invention may contain, based on the total volume of the molded article, portions that are substantially free of zirconium dioxide crystals and in which zirconium dioxide remains amorphous in the glass phase, preferably in proportion to 0 to 50 volume%, more preferably 5 to 40 volume%, in any case.

[0092] In yet another preferred embodiment, the glass ceramic molded article according to the present invention may contain in any case 0.1 to 6% by weight, more preferably 0 to 4% by weight, and particularly 0.5 to 4% by weight or 1 to 2.5% by weight of CeO2 in the glass ceramic, based on the total weight of the glass ceramic.

[0093] Surprisingly, CeO2 as a cometallic oxide was found to produce a different coloration effect in the ZrO2 crystal compared to other parts of the molded body.

[0094] In a particularly preferred embodiment, the molded body has a non-uniform distribution of zirconium dioxide co-oxide cerium crystals. 3+ / Ce 4+ It has been found that molded bodies in which the weight ratio of preferably changes in steps along an axis running through the molded body are particularly preferred. This makes it possible to provide an extremely good aesthetic color gradient in the molded body (especially dental restorations) when combined with zirconium dioxide. This is because not only do the number and size of ZrO2 clusters change along the gradient, but the Ce inside them also changes. 3+ / Ce 4+ This is because the ratio also changes.

[0095] In yet another preferred embodiment, the glass ceramic molded body according to the present invention may contain 0 to 1% by weight, preferably 0.05 to 0.9% by weight, of La2O3 in any case, based on the total weight of the glass ceramic.

[0096] In yet another preferred embodiment, the glass ceramic molded body according to the present invention may be configured such that lithium desilicate is present as the main crystalline phase in an amount of preferably 51 to 75% by weight, particularly 52 to 65% by weight, and especially preferably 53 to 60% by weight, based on the total weight of the crystalline phase in the molded body.

[0097] Furthermore, in another preferred embodiment, the glass ceramic molded body according to the present invention may be configured such that lithium metasilicate is present as a subcrystalline phase in an amount of preferably 20 to 49% by weight, particularly 35 to 48% by weight, and especially preferably 30 to 47% by weight, based on the total weight of the crystalline phase in the molded body.

[0098] In addition, in a preferred embodiment of the glass ceramic molded body according to the present invention, lithium phosphate may be present as a subcrystalline phase in an amount of preferably 5 to 15% by weight, particularly 6 to 14% by weight, and especially preferably 7 to 13% by weight, based on the total weight of the crystalline phase in the molded body.

[0099] The present invention further relates to a process for manufacturing a glass ceramic molded body according to the present invention, comprising the following steps. a) A step of preparing a glass ceramic blank containing zirconium dioxide and one or more cometallic oxides, which can be heat-treated to form zirconium dioxide crystals incorporating one or more cometallic oxides. b) Optionally, preferably a heat treatment at a temperature of 500°C to 600°C to promote nucleation. c) A step of performing heat treatment at a temperature of 500°C to 850°C, preferably 550°C to 780°C, particularly 600°C to 700°C, in order to preferably induce precrystallization, and d) A process of performing non-uniform heat treatment.

[0100] The glass ceramic blank in step a) can be manufactured by melting the components for the molded body according to the present invention as described above. As is known to those skilled in the art, glass ceramics are manufactured by melting starting materials in the first step to obtain glass from the melt. Subsequent crystallization converts the glass melt into glass ceramics.

[0101] The glass ceramic blank described in step a) is substantially composed of a glass melt of the starting components.

[0102] Next, the glass blank can be heated to a temperature range of preferably 450 to 600°C to form crystal nuclei. The nucleation process is usually carried out for more than 30 minutes, preferably more than 60 minutes, and particularly for 60 to 240 minutes.

[0103] The heat treatment for precrystallization in step c) is usually carried out for more than 30 minutes, preferably more than 60 minutes, and particularly for 60 to 600 minutes (e.g., 70 to 250 minutes). This precrystallization makes it possible to crystallize ZrO2 at a low final temperature and a long holding time, forming nanometer-sized microcrystals. In conventional technology, a problem has been that ZrO2-containing glass ceramics crystallize at high temperatures, causing the glass ceramics to suddenly become opaque.

[0104] Non-uniform heat treatment results in the formation of a temperature gradient, which preferably occurs along the axis perpendicular to the heat source.

[0105] In a preferred embodiment, the non-uniform heat treatment is performed at a temperature T1 in a first zone of the blank and at a temperature T2 in a second zone of the blank, where the temperature difference between T1 and T2 is at least 10°C, preferably at least 20°C, more preferably at least 30°C, 40°C, or 45°C or higher, and / or temperature T2 is preferably higher than temperature T1.

[0106] Preferably, temperature T1 is in the range of 600°C to 750°C, more preferably 650°C to 720°C, and / or temperature T2 is in the range of 700°C to 900°C, preferably 740°C to 860°C, where T2 is higher than T1.

[0107] In a preferred embodiment, non-uniform heat treatment is performed by placing the blank at least partially, preferably via form engagement, in a heating chamber and heating the heating chamber, and optionally, in a further step, gradually increasing the temperature inside the heating chamber, and / or by bringing the blank into direct or indirect contact with a heat source, the heat source being preferably a heating plate.

[0108] The present invention also relates to the use of the molded body according to the present invention in the manufacture of dental restorations.

[0109] The present invention further relates to a manufacturing process for dental restorations, wherein the molded body according to the present invention is subjected to at least one non-uniform heat treatment, followed by an isothermal treatment.

[0110] Furthermore, it was surprisingly discovered that the transition in the ratio of the glass phase to the crystalline phase, and the different domains of the crystalline phase, provided in the glass-ceramic molded body according to the present invention, can be achieved by a specific heat treatment. Therefore, the present invention further relates to a manufacturing process for the glass-ceramic molded body according to the present invention, preferably comprising the following steps. a) A step of providing a glass ceramic blank that can form crystals by heat treatment, b) A first uniform heat treatment step preferably performed at a temperature of 500-600°C to promote nucleation. c) A second uniform heat treatment step at a temperature of 580 to 720°C, preferably to induce precrystallization, wherein this temperature is preferably higher than the temperature in step b), and particularly 610 to 720°C, and d) Preferably a non-uniform heat treatment step performed to form a zirconium dioxide-cometallic oxide crystal, preferably a weight gradient.

[0111] The gradient of the zirconium dioxide cometallic oxide crystal is evident from the stepwise increase in the weight (concentration) of the zirconium dioxide cometallic oxide crystal along the axis running through the molded body.

[0112] The glass ceramic blank in step a) can be manufactured by melting the components for the molded body according to the present invention as described above. As is known to those skilled in the art, glass ceramics are manufactured by melting starting materials in a first step to obtain glass from the melt. Subsequent crystallization converts the glass melt into glass ceramics.

[0113] The glass ceramic blank described in step a) is substantially composed of a glass melt of the starting components.

[0114] The first uniform heat treatment is typically performed with a holding time of more than 30 minutes, preferably 30 minutes to 3 hours.

[0115] The second uniform heat treatment is usually performed with a holding time of 30 minutes or more, preferably 30 minutes to 3 hours.

[0116] The non-uniform heat treatment in step d) is typically carried out over a period of 15 to 220 minutes.

[0117] According to the present invention, precrystallization is understood to be a crystallization process carried out at low temperatures and for long holding times, which serves as a basis for the subsequent formation of smaller, particularly nanometer-sized, ZrO2 cometal oxide microcrystals, as well as for the main crystallization of the main and subphases.

[0118] The non-uniform heat treatment of the blank in step d) preferably includes at least one or more non-uniform heat treatments, which are carried out by setting an isothermal and / or non-isothermal heat gradient.

[0119] To achieve non-uniform heat treatment of the blank, preferably a first region of the blank is treated at temperature T1 and a second region of the blank is treated at temperature T2, where 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, 40°C, or 45°C or higher, and / or temperature T2 is preferably higher than temperature T1.

[0120] Temperature T1 is preferably in the range of 600°C to 750°C, more preferably 650°C to 720°C, while temperature T2 is preferably in the range of 700°C to 900°C, more preferably 740°C to 860°C, where T2 is higher than T1.

[0121] The uneven heat treatment of the blank is preferably carried out by contact with a heat source, which may be direct or indirect. The heat source may be a heating chamber or a heatable substrate. Preferably, the uneven heat treatment imparts a thermal gradient to the molded body, which preferably occurs along an axis running through the molded body.

[0122] In a preferred embodiment, the heat treatment is performed by inserting the blank at least partially, preferably via shape engagement, into a heating chamber and heating the heating chamber. This allows for selective heat treatment of individual regions of the blank. The heating chamber is preferably a thermally conductive material having a thermal conductivity of 50 to 500 W / (m·K), preferably 150 to 450 W / (m·K), as measured by thermal flux scanning calorimetry (Waermestromkalorimetrie).

[0123] The thermally conductive material is preferably selected from the group consisting of non-oxide ceramics (preferably Si3N4, silicon carbide, and aluminum nitride) or metals. The heating of the heating chamber can be adjusted according to the required intensity. Thus, in a preferred embodiment, the heating chamber is heated indirectly by the ambient atmosphere, or more preferably directly by contact with a heat source.

[0124] Alternatively, a more preferred method is to heat-treat the blank by means of a heat-retaining substrate on which the blank is placed. In this case as well, the contact may be indirect or direct, depending on the desired intensity. Therefore, an embodiment is preferred where the heat-retaining substrate is a heating plate on which the blank is placed. Alternatively, the heat-retaining substrate may be a thermally conductive material that is heated, for example, via a heating plate, thereby indirectly heating the blank. It is also possible to combine both types of heat treatment.

[0125] Therefore, in a preferred process, the heat treatment is performed by placing the blank at least partially, preferably via shape engagement, in a heating chamber and heating the heating chamber, and optionally, in a further step, by gradually increasing the temperature inside the heating chamber, and / or by bringing the blank into direct or indirect contact with a heat source, which is preferably a heating plate.

[0126] Figure 7 shows an exemplary heating scheme in which the following heating conditions are applied to a blank that has been pre-crystallized. The blank is placed on a heated base inside the furnace. The furnace and the base are heated at a heating rate HR1, the furnace is set to a temperature T1, and this temperature is maintained for a time t1. The substrate is set to a temperature T2 and held at that temperature for a time t2. After the elapse of time t1, the furnace environment is set to a temperature T3 at a heating rate HR2 and held at that temperature for a time t3. Thereafter, the blank is cooled to room temperature (25°C) without control. Since the blank is placed on the base inside the furnace and its lower surface is in direct contact with the base, a temperature gradient between the ambient temperature T1 of the furnace and T2 or T3 may occur within the blank starting from the temperature T2 of the base.

[0127] Generally, this embodiment assumes that T1 < T2, T3 <= T2, and T1 < T3. Also, preferably, t3 < t2 and t1 > t3 hold.

[0128] The opacity and chroma of the cervical region and the dentin region can be adjusted using the temperature T2 and the holding time t2. Generally, the longer the holding time and the higher the temperature in this heating process, the higher the chroma and opacity of the cervical region become.

[0129] The gradient can be set using the temperature T1 and the holding time t1 (assuming T2 and t2 are constant at this time). The difference between T1 and T2 determines how much the gradient spreads towards the incisal edge (the strength (strong - weak) of the gradient can also be adjusted). <000​​​​​The present invention further relates to the use of molded bodies according to the present invention for manufacturing dental restorations. The molded bodies according to the present invention are used to manufacture dental restorations, preferably in the anterior tooth region, and particularly for laminate veneers, crowns, inlays, and onlays. Furthermore, the glass-ceramic molded bodies according to the present invention are used particularly for single tooth restorations, maxillary and / or mandibular complete dentures, dental bridges, and locator dentures. Other dental applications are known to those skilled in the art, and therefore the use of such glass-ceramic molded bodies is not limited to this list.

[0132] The present invention further relates to a process for manufacturing dental restorations using a monolithic glass-ceramic molded body according to the present invention. In this process, a molded body according to the present invention is prepared by subjecting it to at least one first non-uniform heat treatment, and then subjected to a further isothermal treatment. The temperature of this isothermal treatment is preferably 730 to 850°C, more preferably 750 to 820°C. The holding time at this temperature is preferably 1 to 60 minutes, particularly preferably 5 to 30 minutes. This process step can optionally be directly incorporated into the same furnace firing process following the first non-uniform heat treatment. In a preferred embodiment, the method according to the present invention further includes a step of cutting the molded body into the geometric shape of a dental restoration, preferably before subjecting the molded body to further heat treatment. [Brief explanation of the drawing]

[0133] The present invention will be described in more detail by the following embodiments and drawings, but these should not be understood as limiting the concept of the present invention.

[0134] [Figure 1] This image shows the crystal structure and the size of the ZrO2 crystal clusters in the cervical region of the glass ceramic molded body according to the present invention, as captured using a scanning electron microscope (SEM). [Figure 2] This shows a ZrO2 cluster according to the present invention, which contains nanocrystalline ZrO2 crystals. [Figure 3]The changes in the crystal structure of the glass ceramic molded body according to the present invention, from the cervical region (1) to the edentary region (12), are shown, as recorded using SEM and XRD. [Figure 4] The following are exemplary color measurements of different regions of the glass ceramic body according to the present invention (from plate (1), the incisal edge of the tooth crown, to plate (5), the cervical region), which were characterized by color coordinates (reflectance) and ΔE. [Figure 5] The crystal composition of the crystalline phase from the tooth tip (1) to the tooth neck (7) of the glass ceramic molded body according to the present invention, as determined by Rietveld analysis, and the results of color measurements by transmission over a wavelength range of 360 to 750 nm are shown. [Figure 6] The crystal composition of the entire molded body (crystalline phase and glass phase) from the tooth tip (1) to the tooth neck (7) of the glass ceramic molded body according to the present invention, as determined by Rietveld analysis, and the results of color measurements by transmission over a wavelength range of 360 to 750 nm are shown. [Figure 7] The temperature profile of the process for manufacturing a glass-ceramic molded body according to the present invention is shown exemplarily. [Figure 8a] A TEM image of a zirconium dioxide-cerium oxide crystal is shown. [Figure 8b] A TEM image of a zirconium dioxide-terbium oxide crystal is shown. [Figure 8c] A TEM image of a zirconium dioxide crystal is shown. [Figure 8d] A TEM image of a zirconium dioxide-vanadium oxide crystal is shown. [Figure 9a] This shows a TEM image of tetragonal ZrO2. [Figure 9b] Exemplary electron diffraction patterns are shown, proving that ZrO2 has a tetragonal crystal structure. [Figure 10]Using electron energy loss spectroscopy (EELS) charts, the proportion of incorporated f elements increases from top to bottom (with increasing ZrO2 cluster size). Similarly, the cervical region shows a higher Ce3+ / Ce4+ ratio than the central region. Trivalent cerium shows a color effect, but tetravalent cerium does not. No Ce or Tb signals are detected in the outermost region. [Figure 11] A schematic diagram shows a monolithic molded body according to the present invention, having an incisal edge region and a cervical region. [Figure 12] This diagram schematically illustrates the preparation of a molded body according to the present invention onto a plate used for measurement. [Figure 13a] Using the aforementioned Example VIII as an example, the preparation of 12 plates cut from a 12 mm thick molded body is shown, with plate 1 being the cervical plate (closest to the non-uniform heat source (base)) and extending to the incisal edge (plate 12, furthest from the non-uniform heat source (base)). Translucency increases and saturation decreases from 1 to 12, similar to natural teeth. [Figure 13b] This shows an artificial tooth milled from Example VIII, which has a natural color tone and translucency gradient. [Figure 13c] The following shows the SEM measurement results of 12 plates cut from a 12mm thick molded body. [Examples]

[0135] An example composition of a glass-ceramic molded article according to the present invention. Values ​​are in weight percent.

[0136] [Table 1]

[0137] Table 1 shows the measured reflectance values ​​of four glass ceramic molded bodies according to the present invention. This is reflected as a color gradient from the incisal edge to the cervical area, a characteristic L * a * b *It is determined by a value.

[0138] [Table 2]

[0139] Table 2 shows the results of Rietveld analysis of a molded body with MgO as the internal standard. Here, four equally sized sections A-D, extracted from different locations on the molded body, were measured. Each percentage is expressed in weight percent.

[0140] [Table 3]

[0141] To further illustrate the color tone or color difference, plates were fabricated from the glass-ceramic molded body according to the present invention. These plates were then examined again with respect to their color coordinates, as shown in Figure 4.

[0142] [Table 4]

[0143] [Table 5]

[0144] To illustrate the light transmission profile in a preferred embodiment of the glass-ceramic molded body according to the present invention, several plates were prepared and compared with one another (see Figure 5).

[0145] [Table 6]

[0146] Furthermore, the morphology and lithium crystal content of the plate in another preferred embodiment (Figure 6) were investigated.

[0147] [Table 7]

[0148] Further exemplary manufacturing processes for glass-ceramic molded articles according to the present invention. Composition values ​​are in weight percent.

[0149] [Table 8]

[0150] Further exemplary manufacturing processes for glass-ceramic molded articles according to the present invention. Composition values ​​are in weight percent.

[0151] After cooling, the blank is heated at 550°C for 2 hours for nucleation, and then further heated in the furnace at 660°C for 2 hours for precrystallization.

[0152] The following heating conditions are applied to a pre-crystallized blank according to the heating scheme shown in Figure 7. The blank is placed on the heating surface inside the furnace. The furnace and base are heated at a heating rate of HR1, and the furnace is set to a temperature T1, which is maintained for a time t1. The substrate (base) is set to a temperature T2 and held there for a time t2. After time t1 has elapsed, the furnace environment is set to a temperature T3 at a heating rate of HR2 and held there for a time t3. Thereafter, the blank is cooled to room temperature (25°C) without control. Since the blank is placed on the base inside the furnace and its underside is in direct contact with the base, a temperature gradient may be created inside the blank between the ambient furnace temperatures T1 and T2 or T3, starting from the base temperature T2.

[0153] The following parameters were set for the blank according to composition i) in Table A (Examples I-VII). For Example VIII, composition ii) was used.

[0154] [Table 9]

[0155] The resulting glass ceramics I to VIII exhibit a color gradient and translucency gradient similar to the natural color and translucency gradient of natural teeth.

[0156] Color measurements and Rietveld analysis of glass ceramics I-IV were performed on the blank zones that were in contact with the substrate (cervical region) and the blank zones furthest from the substrate (edges / incisal edge) (see Figure 11).

[0157] The measurement results are shown in Tables C and D below.

[0158] [Table 10]

[0159] [Table 11]

[0160] The crystalline phase is calculated to make up 100% by weight, excluding the glass phase.

[0161] For the glass ceramic of Example VII, the heat-treated glass ceramic molded body according to the present invention was cut into plate shapes along the principal axis, which moves away from the substrate (the hottest point) along the formed temperature gradient, and perpendicular to that principal axis (from the cervical region to the incisal edge) (see Figure 12). Transmittance tests and XRD measurements were performed on these small plates to determine the proportion of crystalline and amorphous materials.

[0162] The results of Example VII are shown in Table E below.

[0163] [Table 12]

[0164] A color gradient appears to be formed along the temperature gradient, which is due to the incorporation of one or more cometallic oxides into zirconium dioxide (Me x Zr 1-x This is due to O2. A concentration gradient of zirconium dioxide crystallites containing cometallic oxides is formed within the glass-ceramic molded body perpendicular to the substrate (heat source for non-uniform heating) and along an axis that penetrates the molded body.

[0165] In a further series of measurements of the molded body according to Example VII, the molded body was cut into five plates in the same manner as described above, and the color values ​​were measured.

[0166] The measured values ​​are shown in Table F below. Here, plate 1 is located at the incisal edge and plate 5 is located at the cervical region.

[0167] [Table 13]

[0168] For the molded article according to the present invention shown in Example VIII, seven plates were cut out and measured in the same manner as described above in Example VII and shown in Figure 12. The measurement data is shown in Table G below.

[0169] [Table 14]

[0170] Figure 13a shows an example of fabricating 12 plates from a 12 mm thick molded body using the aforementioned Example VIII. These were measured by SEM observation (Figure 13c) after being cut out. Plate 1 is the cervical plate (closest to the non-uniform heat source (base)), and plate 12 is the incisal edge (farthest from the non-uniform heat source (base)). Translucency increases and saturation decreases from 1 to 12, similar to natural teeth. Figure 13b shows an artificial tooth milled from Example VIII with a natural color and translucency gradient.

Claims

1. A glass ceramic molded body having a color gradient (Farbverlauf), comprising zirconium dioxide crystals incorporating one or more cometallic oxides.

2. The glass ceramic molded body according to claim 1, wherein the crystal is a mixed crystal (Mischkristalle) of zirconium dioxide and one or more cometallic oxides.

3. The glass ceramic molded body according to claim 1, wherein the crystal is a zirconium dioxide crystal doped with a cometallic oxide.

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

5. The glass ceramic molded body according to any one of the preceding claims, wherein the cometallic 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.

6. The glass ceramic molded body according to any one of the preceding claims, wherein the zirconium dioxide crystals incorporating one or more cometallic oxides have a size of 1000 nm or less, preferably 500 nm or less.

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

8. The glass ceramic molded body according to any one of the preceding claims, wherein the molded body has an amorphous portion and a crystalline portion, and the molded body has a non-uniform distribution of the amorphous portion and the crystalline portion.

9. A glass ceramic molded body according to any one of the preceding claims, wherein the molded body has a structure in which the weight ratio of amorphous portions to crystalline portions changes gradually, and the gradient occurs along an axis that penetrates the molded body.

10. The glass ceramic molded body according to any one of the preceding claims, wherein the molded body has a structure in which the weight fraction of zirconium dioxide crystals incorporating one or more cometallic oxides gradually changes, and the gradient is along an axis that runs through the molded body.

11. The glass ceramic molded article according to any one of the preceding claims, further comprising lithium metasilicate crystals and / or lithium disilicate crystals.

12. The molded body is a glass ceramic molded body according to any one of the preceding claims, wherein the molded body has lithium disilicate as the main crystalline phase.

13. The molded body preferably contains 50 to 70% by weight of SiO ２ A glass ceramic molded body according to any one of the preceding claims, comprising the above.

14. The molded body preferably contains 10 to 25% by weight of Li ２ A glass ceramic molded body according to any one of the preceding claims, comprising O.

15. The molded body preferably contains 0.5 to 6% by weight of K ２ A glass ceramic molded body according to any one of the preceding claims, comprising O.

16. The molded body preferably contains 2 to 12% by weight of P ２ O ５ A glass ceramic molded body according to any one of the preceding claims, comprising the above.

17. The molded body preferably contains 2 to 12% by weight of P ２ O ５ A glass ceramic molded body according to any one of the preceding claims, comprising the above.

18. The molded body preferably contains 8 to 15% by weight of ZrO ２ A glass ceramic molded body according to any one of the preceding claims, comprising the above.

19. The glass ceramic molded article according to any one of the preceding claims, wherein the molded article preferably contains 0.1 to 10% by weight of a cometal oxide.

20. The aforementioned molded body consists of the following components: i) 56 to 64% by weight, preferably 56 to 59% by weight of SiO ２ ii) 15-21% by weight, preferably 16-20% by weight of Li ２ O iii) 1-4% by weight of K ２ O iv) 3-8% by weight of P ２ O ５ v) 8-15% by weight, preferably 8-12% by weight, and especially 9-11% by weight of ZrO ２ vi) 0.1 to 8% by weight of cometal oxide A glass ceramic molded body according to any one of the preceding claims, comprising the above.

21. The aforementioned molded body is, formula M ｚ Zr １－ｚ O ２ A glass ceramic molded body according to any one of the preceding claims, comprising a crystal represented by , wherein M is an element of d or an element of f, and z is a rational number of 0.0001 to 0.5, preferably 0.001 to 0.3, more preferably 0.001 to 0.1, or 0.002 to 0.05, or 0.003 to 0.

03.

22. The aforementioned molded body is, formula M ｚ Zr １－ｚ O ２ A glass ceramic molded body according to any one of the preceding claims, comprising a crystal represented by , wherein 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.

23. The aforementioned molded body is, formula M ｚ Zr １－ｚ O ２ A glass ceramic molded body according to any one of the preceding claims, comprising a crystal represented by , wherein M is selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb.

24. The glass ceramic molded body according to any one of the preceding claims, wherein the molded body contains a crystal represented by the formula MzZr1-zO2, and M is selected from the group consisting of Ce, Tb, Pr, Er, Nd, Eu, Fe, V, and Mn.

25. The following steps: a) A step of providing a glass blank containing zirconium dioxide and one or more cometallic oxides, wherein the blank is capable of forming zirconium dioxide crystals incorporating one or more cometallic oxides by heat treatment. b) Preferably a temperature of 500°C to 600°C, preferably an optional heat treatment step to promote nucleation. c) A heat treatment step to induce precrystallization, preferably at a temperature of 500°C to 850°C, preferably 550°C to 780°C. d) Non-uniform heat treatment process, A method for manufacturing a glass ceramic molded article according to any one or more of claims 1 to 24, including

26. The aforementioned non-uniform heat treatment results in a temperature T in the first region of the blank. １ Furthermore, in the second region of the blank, the temperature T ２ It was carried out at temperature T １ and temperature T ２ The temperature difference with 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 T ２ Preferably the temperature T １ The manufacturing method according to claim 25, which is higher than the above.

27. The temperature T １ The temperature is in the range of 600°C to 750°C, preferably 650°C to 720°C, and / or the temperature T ２ The temperature is in the range of 700°C to 900°C, preferably 740°C to 860°C. ２ is T １ A manufacturing method according to at least one of claims 25 or 26, which is higher than the method described above.

28. The manufacturing method according to any one or more of claims 25 to 27, wherein the non-uniform heat treatment is performed by inserting at least a portion of the blank into a heating chamber, preferably via shape engagement, and heating the heating chamber, optionally gradually increasing the temperature inside the heating chamber in another step, and / or the heat treatment is performed by direct or indirect contact with a heat source, the heat source preferably being a heating plate.

29. Use of a molded body according to any one or more of claims 1 to 24 for manufacturing dental restorations.

30. A method for manufacturing a dental restoration, which provides a molded article according to any one or more of claims 1 to 24, preferably subjected to at least one non-uniform heat treatment, and further provides a method for manufacturing the article by subjecting it to another heat treatment that is isothermal in nature.

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