Process for manufacturing ceramic and glass ceramic dental restorations

Abstract

Providing a method for manufacturing ceramic and glass ceramic dental restorations. [Solution] A method for manufacturing an all-ceramic dental restoration having an integrated core and shell structure, comprising constructing a digital construction model of the dental restoration, dividing the obtained CAD dataset into at least two separate CAD sub-datasets, one sub-dataset defining the contour of the core structure, a second sub-dataset defining the contour of the shell structure, manufacturing the green body of the core structure using the first CAD sub-dataset, and manufacturing the green body of the shell structure of the restoration using the second CAD sub-dataset. Next, the core structure and the shell structure are joined in a green state, the green body is subjected to heat treatment to remove the binder, and the parts are sintered to obtain a finished dental restoration. This process makes it possible to manufacture a dental restoration with improved aesthetics compared to the manufacture of an integrated restoration without significant additional effort.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing ceramic and glass-ceramic dental restorations, such as dental inlays, onlays, veneers, crowns, bridges, and frameworks. [Background technology]

[0002] For aesthetic reasons, dental restorations are increasingly being made entirely of ceramic. In practice, this often involves veneering glass ceramic onto a framework made of oxide ceramic.

[0003] DE102005042091 A1 discloses a method for manufacturing a ceramic dental prosthesis, comprising milling a framework from an oxide ceramic blank, such as aluminum oxide or zirconium dioxide, and milling a veneer from a glass ceramic block, such as silicate ceramic. The framework and veneer are manufactured using a CAD / CAM process. The framework and veneer are then joined and fired using a low-viscosity, low-melting-point ceramic material. After sintering, the occlusion is milled and the restoration is completed by glazing firing.

[0004] WO 2007 / 051447 A1 discloses a method for manufacturing a multilayer dental prosthesis, comprising first manufacturing a support framework structure from a metal or ceramic material or polymer using CAD / CAM, and then applying a functional layer that functions as a veneer. The functional layer is preferably manufactured using an additive process, such as hot pressing, die casting, or slip casting.

[0005] The manufacture of ceramic molded parts by milling is disadvantageous because ceramic materials are extremely hard, making processing very time-consuming and resulting in high wear on the grinding devices and milling cutters used. To avoid these disadvantages, WO 2010 / 010087 A1 proposes the use of porous ceramic bodies in the manufacture of veneers applied to metal or ceramic frameworks. The veneer may consist of several layers, and its interface corresponds to the dentin / enamel interface of a natural or artificial tooth. The veneer is manufactured by pressing commercially available veneer ceramic powder into a block and then pre-sintering it. The veneer is milled from the block using a CAD / CAM system and then densified sintered on a zirconia coping. In this procedure, the different shrinkage behaviors of the framework and the veneer material must be taken into consideration.

[0006] DE102010002484 A1 discloses the manufacture of a dental crown having an oxide ceramic core and an outer layer of plastic, oxide ceramic, or glass ceramic. The interface between the core and the outer layer follows the dentin-enamel boundary of a natural tooth. This method is said to achieve an appearance similar to that of a natural tooth. The core is manufactured using a computer-aided process, such as CAD / CAM or a manufacturing process, while the outer layer is manufactured by manual lamination, overpressing, or the use of a computer-aided process. The outer layer is bonded to the core by bonding, sintering, or polymerization.

[0007] DE102016115916 A1 discloses a method for generating processing data for the manufacture of dental prostheses having ceramic veneers and carriers. The method takes into account the different shrinkage rates of the support and veneer, and is said to enable, for the first time, the sintering of veneers and supports made from different materials together. The problem is that the support and veneer shells only fit together perfectly during the final sintering, which makes precise positioning of the shells on the support before sintering difficult and increases the risk of errors.

[0008] In addition to conventional milling processes, generative processes, such as stereolithography, are increasingly being used in the manufacture of dental restorations. In stereolithography, molded parts are constructed layer by layer from a curable liquid monomer resin using computer-aided design data (CAD data) (A. Beil, Fertigung von Mikro-Bauteilen mittels Stereolithographie [Production of micro-components using stereolithography], Duesseldorf 2002, VDI-Publisher 3 ff.). Stereolithography processes are advantageous in the manufacture of dental molded products made from ceramic materials because they allow for a significant simplification of manual molding and casting processes, as well as milling and grinding operations, and avoid the large amount of material loss that occurs in non-generative processes. With the establishment of fully digital process chains, the classic process steps for manufacturing dental restorations can now be replaced by digitizing the model, virtual design of the dental molded product, and generative stereolithography manufacturing thereof.

[0009] In the stereolithography manufacturing of ceramic molded parts, a ceramic green body is first produced by radiation-curing ceramic slip layers by layer. This green body is then debindered and sintered into a dense ceramic molded body. The green body is also called a green part. Debindering refers to the removal of the binder. In this specification, the used binder is typically decomposed and removed by heating the green body to a temperature of approximately 80°C to 600°C, forming volatile components through thermal and thermochemical processes. It is essential to avoid crack formation and deformation as much as possible.

[0010] Debinding is a critical step in the process. The gases and pressures generated during the decomposition of the organic matrix pose a high risk of component damage. Even small defects between individual building layers can cause cracking or even complete failure of the component during debinding. This risk can be reduced by increasing the debinding time, but this significantly increases the process time.

[0011] The debindered parts are sintered during high-temperature firing in a sintering furnace. The finely dispersed ceramic powder is compressed and solidified by the effect of temperatures below the melting point of the main component, reducing the size of the porous parts and increasing their strength.

[0012] US 5,496,682 discloses a photocurable composition for the production of three-dimensional bodies by stereolithography, comprising 40 to 70 volume percent of ceramic or metal particles, 10 to 35 wt percent of monomer, 1 to 10 wt percent of photoinitiator, 1 to 10 wt percent of dispersant, and preferably further comprising a solvent, a plasticizer, and a coupling agent.

[0013] US 6,117,612 describes a resin for the stereolithography of sintered ceramic or metal parts. The resin has a viscosity of less than 3000 mPa·s. Its manufacture uses low-viscosity monomers, preferably in aqueous solution. The use of dispersants is intended to achieve low viscosity and high solid content.

[0014] DE102005058116 A1 discloses a suspension for stereolithographic production of ceramic implants by the method described in US 6,117,612, which does not contain any diluents (e.g., water or organic solvents). The viscosity of the suspension is adjusted to less than 20 Pa·s by varying the concentration of the dispersant. Alkylammonium salts of copolymers having acidic groups can also be used as dispersants, which can be layered on top of ceramic powder particles.

[0015] US 2005 / 0090575 A1 describes methods and compositions for the stereolithographic manufacture of ceramic parts. It is stated that molded parts manufactured using liquid materials known from US 5,496,682 are soft and therefore require an additional curing step to avoid deformation during firing, while molded parts obtained from paste-like materials build internal stresses during debinding, which causes cracks during sintering. To avoid these problems, plasticizers are used and the amount of ceramic powder is selected so that the viscosity of the composition is at least 10,000 Pa·s. EP2233449 A1 discloses a slurry for the manufacture of ceramic molded parts using a hot-melt inkjet printing process, comprising ceramic particles, wax, and at least one radically polymerizable wax, for producing a green body that can be debindered without cracking. A drawback of these slurries is that they tend to separate in a liquid state when left standing for a long time. This is not a significant issue in hot-melt inkjet processes because the slurry exists in liquid form only during the printing process, i.e., for a relatively short period. However, in stereolithography processes, the slurry must remain stable in liquid form for a longer period, which in particular means that particles dispersed in the slurry must not settle prematurely. The object of the present invention is to provide a method and materials for manufacturing high-strength all-ceramic dental restorations that do not have the drawbacks of the prior art and enable the easy manufacture of aesthetically superior restorations with a natural appearance. [Prior art documents] [Patent Documents]

[0016] [Patent Document 1] German Patent Application Publication No. 102005042091 Specification [Patent Document 2] International Publication No. 2007 / 051447 [Patent Document 3] International Publication No. 2010 / 010087 [Patent Document 4] German Patent Application Publication No. 102010002484 Specification [Patent Document 5] German Patent Application Publication No. 102016115916 Specification [Patent Document 6] U.S. Patent No. 5,496,682 Specification [Patent Document 7] U.S. Patent No. 6,117,612 Specification [Patent Document 8] German Patent Application Publication No. 102005058116 Specification [Patent Document 9] U.S. Patent Application Publication No. 2005 / 0090575 Specification [Patent Document 10] European Patent Application Publication No. 2233449 Specification [Non-Patent Document]

[0017] [Non-Patent Document 1] A. Beil, Fertigung von Mikro-Bauteilen mittels Stereolithographie [Production of micro-components using stereolithography], Dusseldorf 2002, VDI-Publisher 3 ff. [Summary of the Invention] [Means for Solving the Problems]

[0018] According to the present invention, this task is solved by a process for manufacturing a dental restoration using an integrated framework structure and a matching veneer structure, by manufacturing the framework structure and the veneer structure separately using additive processes, and then joining them to form a dental restoration. The framework structure is also referred to here as the core structure or core. The veneer structure may be integrated or may consist of several components that together form the veneer structure. The veneer structure and its components are also referred to as the shell structure or shell. If the veneer structure consists of several components, these are preferably also manufactured separately from each other. [Modes for carrying out the invention]

[0019] In the first step of the process according to the present invention, a CAD (computer-aided design) program is used to construct a digital design model of a dental restoration in accordance with anatomical and clinical requirements. The CAD dataset of the restoration obtained in this manner is then divided (file split) into at least two separate but non-independent sub-datasets, the first CAD sub-dataset defining the contour of the internal core structure (core), and the second CAD sub-dataset defining the contour of the external shell structure (shell) of the dental restoration. The second sub-dataset can be further subdivided into two or more sub-datasets, each containing a portion of the contour of the external shell structure. One or more joint gaps can be provided at predetermined points between the contours. As a result, at least two CAD datasets are obtained, each of which is saved in a file format more suitable for the CAD software, preferably in STL format. Next, the CAD datasets are used to generate machining data for the additive manufacturing of the core and shell structures using CAM (computer-aided manufacturing) software. The final output format is at least two separate output files. Next, the core and shell structures are additively manufactured independently of each other in a computer-controlled process using the generated dataset, preferably by stereolithography.

[0020] The core and shell structures are designed according to the desired requirements. The core structure is typically darker and less translucent than the shell structure, which is lighter in color and more translucent. These respective characteristics are individually adapted to the aesthetic requirements of the practitioner or patient, or to the condition of the remaining teeth.

[0021] Preferably, to manufacture a dental restoration, a first CAD partial data set is used to harden a first slurry by locally irradiating it with radiant energy to form the geometric shape of the core structure, thereby manufacturing the green body of the core structure of the restoration.

[0022] In a further step, the second slurry is hardened by locally irradiating it with radiant energy using the second CAD partial dataset to form the geometric shape of the shell structure, thereby producing a green body of the restoration's shell structure.

[0023] If the shell structure contains more than one component, a separate green body is created for each part of the shell structure. To manufacture a multi-part shell structure, a second CAD part dataset of the digital design model is created from two or more additional CAD datasets (n 出力ファイル >2) Divide into parts, each containing a portion of the shell structure contour. Next, using these CAD shell structure sub-datasets, components are manufactured by using the first CAD shell structure sub-dataset to harden a second slip by locally irradiating it with radiant energy to form the geometric shape of the first component of the shell structure, and separately, using the second CAD shell structure sub-dataset, further slips are hardened by locally introducing radiant energy to form the geometric shape of the second component of the shell structure, and this step is repeated as many times as necessary depending on the number of CAD shell structure sub-datasets for the purpose of manufacturing a desired number of components. With each iteration, one green body of the shell structure component is manufactured.

[0024] To manufacture the components of the shell structure, the same or different slips can be used for each component. Preferably, the components are made from different, and more preferably differently, colored slurries.

[0025] In a subsequent step, the core structure and the shell structure, or the core structure and the components of the shell structure, are joined in a green state to obtain a bonded green body of the dental restoration. Preferably, an additional slurry, hereby called a bonded slip, is used to improve the adhesion of the individual parts. The bonded slip is preferably polymerizable, and particularly preferably radically polymerizable. A photoreactive bonded slurry, i.e., a slurry that can be cured by light irradiation, is particularly preferred, and polymerization of the bonded slip is preferably initiated by exposing the slurry to light. Polymerization of the bonded slip makes it possible to firmly bond the individual elements of the dental restoration in a green state.

[0026] By intentionally applying a strongly colored slurry before joining the parts and before applying the bonding slip, the bonding surfaces of the core and / or shell structures can be individually characterized. Slurries having the same composition as those used in the manufacture of the core and shell structures, but with a higher content of coloring components, are particularly suitable for this purpose. These strongly colored slurries are preferably photoreactive and can be locally fixed by irradiation before applying the bonding slip and finally joining the individual parts of the dental restoration.

[0027] Next, the green body of the dental restoration is subjected to a further heat treatment to remove the binder (de-bindering) to obtain the brown body of the dental restoration. In a subsequent step, the brown body of the dental restoration is sintered to obtain the finished dental restoration.

[0028] The core and shell structure of the green body is preferably manufactured by stereolithography. In this process, a ceramic green body with a core and shell structure is manufactured by radiation-curing a ceramic slurry that is fluid at the processing temperature layer by layer, and then these are joined together to form the green body of the dental restoration. The joining can be done manually. Preferably, the green bodies are joined using joining slips. It is particularly preferable to use photoreactive joining slips and cure them by irradiating them with light of a suitable wavelength after joining. This increases the strength of the green body of the dental restoration, makes it easier to handle, and reduces the risk of damage.

[0029] Next, the green body of the dental restoration is debindered by heating it to a temperature of preferably 90°C to 600°C.

[0030] Next, the resulting Brownian body of the dental restoration is sintered to form a dense ceramic molded body. Sintering is preferably carried out by heating to a temperature of 650 to 1800°C, for example, in a sintering furnace. The sintering conditions depend on the building material used. Brownian bodies made of glass ceramic are preferably sintered at a temperature of 650 to 1100°C, particularly preferably 700 to 950°C; Brownian bodies made of zirconium dioxide are preferably sintered at a temperature of 1100 to 1600°C, particularly preferably 1300 to 1500°C; and Brownian bodies made of aluminum oxide are preferably sintered at a temperature of 1400 to 1800°C, particularly preferably 1600 to 1700°C.

[0031] Ceramic molded articles manufactured according to the method of the present invention are characterized by high strength and excellent precision. For molded articles made of glass ceramic, the bending strength in accordance with ISO 6872 is preferably higher than 100 MPa, and particularly in the range of 150 to 500 MPa. For molded articles made of Al2O3, the bending strength preferably exceeds 300 MPa, and particularly in the range of 500 to 700 MPa, and for molded articles made of ZrO2, the bending strength exceeds 500 MPa, and particularly in the range of 800 to 1100 MPa.

[0032] According to the present invention, core and shell structures are manufactured using slurries having similar thermal expansion coefficients and similar sintering shrinkage, and used as bonding slips where applicable, so that the green bodies of dental restorations can be debindered and sintered without problems. By matching the thermal expansion coefficients and sintering shrinkage, it becomes possible to manufacture precisely fitting core and shell green bodies, as it is not necessary to consider different shrinkage behaviors. This greatly simplifies the joining of core and shell structures and reduces the risk of errors, for example, caused by unintended displacement of the shell structure on the core.

[0033] To facilitate the joining of the core and shell structures, the core and shell structures may be provided with insertion grooves, joints, ribs, or similar structures, which ideally align the core and shell with each other, enabling clear and geometrically mating alignment of the molded parts. Such structures can also serve optical functions after sintering. For example, they can mimic the natural mamelon structure of teeth.

[0034] The dental restoration according to the present invention includes a supporting core structure and a shell structure. The shell structure is attached to the core structure. The core structure is attached to the tooth(s) or implant(s) to be restored when the completed restoration is placed in the patient's oral cavity. The shell structure can completely, or preferably partially, surround or cover the surface of the core. The shell structure of the dental restoration may include one or more components, preferably one or two components (which together form the shell structure). Preferably, the shell structure includes only one component.

[0035] While the use of multiple components is more complex, it offers advantages because it allows for better encasing of core structures with undercuts. Additionally, dividing the shell structure into several components can be advantageous from a manufacturing perspective. For example, manufacturing two separate components to cover the front and back of the core structure is easier than manufacturing a single, integrated shell structure covering both areas. The risk of stress and bubble formation during joining can also be reduced by using a multi-part shell structure. Using multiple components can also have aesthetic advantages. For instance, stacking and arranging several shell structures of different colors can achieve a particularly natural appearance.

[0036] For the manufacture of core and shell structures, and as a joint slip, preferably, (a) at least one radical polymerizable monomer, (b) at least one photoinitiator, and (c) Ceramics, glass, and / or glass ceramic particles Use a slurry containing the following:

[0037] The slurry according to the present invention comprises, as monomer (a), at least one (meth)acrylate and / or (meth)acrylamide, preferably a monofunctional or polyfunctional (meth)acrylate, or a mixture thereof. Particularly preferred is a material containing, as a radical polymerizable monomer, at least one polyfunctional (meth)acrylate, or a mixture of monofunctional and polyfunctional (meth)acrylates. A monofunctional (meth)acrylate is a compound having one radical polymerizable group, and a polyfunctional (meth)acrylate is a compound having two or more, preferably 2 to 6, radical polymerizable groups.

[0038] Particularly preferred monofunctional or polyfunctional (meth)acrylates include methyl-, ethyl-, 2-hydroxyethyl-, butyl-, benzyl-, tetrahydrofurfuryl-, or isobornyl (meth)acrylate, p-cumylphenoxyethylene glycol methacrylate (CMP-1E), bisphenol A di(meth)acrylate, bis-G(M)A (addition product of (meth)acrylic acid and bisphenol A diglycidyl ether), ethoxylated or propoxylated bisphenol A di(meth)acrylate, for example, bisphenol-A-di(meth)acrylate having three ethoxy groups (SR-348C=methacrylate; SR-349=acrylate, Sartomer) or having two ethoxy groups (SR-348L=methacrylate, Sartomer), 2,2-bis[4-(2-(meth)acryloxypropoxy)phenyl]propane, UD(M)A (2-hydroxyethyl(meth) (Addition product of acrylate and 2,2,4- or 2,4,4-trimethylhexamethylene-1,6-diisocyanate), di-, tri-, tetra-, penta-, hexa-, or hepta-ethylene glycol di(meth)acrylate, di-, tri-, tetra-, penta-, hexa-, or hepta-propylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate These include glycerol di(meth)acrylate and tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate (D3MA), 1,12-dodecanediol di(meth)acrylate, oligomeric polyether-, polyester-, epoxy-, urethane-(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, and mixtures thereof.

[0039] Particularly preferred are monofunctional, difunctional, and trifunctional acrylates and monofunctional, difunctional, and trifunctional methacrylates with a molecular weight <1000 g / mol, such as aliphatic urethane diacrylates, HEA phthalates (Photomer 4173), diHEA pyromellitic acid (HEA = 2-hydroxyethyl acrylate), bisphenol A di(meth)acrylate, bis-G(M)A (addition product of (meth)acrylic acid and bisphenol A diglycidyl ether), and ethoxylated or propoxylated bisphenol A di (meth)acrylates, such as bisphenol A di(meth)acrylate (SR-348C, SR-349, SR-348L), 2,2-bis[4-(2-(meth)acryloxypropoxy)phenyl]propane, UD(M)A, triethylene glycol di(meth)acrylate (TEGD(M)A), tricyclodecanedimethanol di(meth)acrylate, ethoxylated or propoxylated trimethylolpropane tri(meth)acrylate, such as 3x propoxylated trimethylolpropane triacrylate (Sartomer SR-492), tripropylene glycol diacrylate, and mixtures thereof. These monomers are characterized by high reactivity / high double bond conversion rate, good mechanical properties, low polymerization shrinkage, and relatively low viscosity.

[0040] Further preferred monomers include acrylamides, such as N-ethylacrylamide, N,N-dimethylacrylamide, N-(2-hydroxyethyl)acrylamide, N,N'-diethyl-1,3-bis(acrylamide)propane, and 1,4-bis(acrylamide)butane. Compared to monoacrylamides, bisacrylamides are preferably used in excess in the organic binder.

[0041] The properties of the slurry before and after photocuring can be influenced by the specific combination of monomers. Mixtures of monofunctional and difunctional monomers are characterized by relatively low viscosity and reactivity in the resin mixture, with viscosity and reactivity decreasing with increasing monofunctional monomer content. The monofunctional monomer content ensures lower brittleness and faster debinding of the green body obtained by photocuring the slurry. Mixtures of difunctional and trifunctional monomers are more reactive, with reactivity increasing with increasing trifunctional monomer content. The trifunctional monomer content results in higher brittleness and slower debinding of the green body.

[0042] The reactivity and viscosity of the resin mixture, as well as polymerization shrinkage, are also determined by the molar mass of the monomers; as the molar mass increases, polymerization shrinkage decreases while viscosity increases. Finally, the interaction with the material in the stereolithography chamber, such as swelling of the material in the polymerization chamber, can be influenced by the polarity of the monomers.

[0043] Preferred photoinitiators (b) for initiating radical photopolymerization are benzophenone, benzoin, and their derivatives, or diketones or their derivatives, such as 9,10-phenanthrenequinone, 1-phenylpropane-1,2-dione, diacetyl, or 4,4'-dichlorobenzyl. Particularly preferred are camphorquinone (CQ) and 2,2-dimethoxy-2-phenylacetophenone, and especially preferred are combinations of α-diketones with amines as reducing agents, such as 4-(dimethylamino)-benzoic acid ester (EDMAB), N,N-dimethylaminoethyl methacrylate, N,N-dimethyl-sym.-xylidine, or triethanolamine.

[0044] Particularly preferred photoinitiators are Nourish type I photoinitiators, especially monoacyl or bisacylphosphine oxides, especially monoacyltrialkyl or diacyldialkylgermanium compounds, such as benzoyltrimethylgermanium, dibenzoyldiethylgermanium, or bis(4-methoxybenzoyl)diethylgermanium (MBDEGe). Advantageously, mixtures of various photoinitiators, such as a combination of bis(4-methoxybenzoyl)diethylgermanium with camphorquinone and ethyl 4-dimethylaminobenzoate, can also be used.

[0045] Particularly preferred are the combination of camphorquinone (CAS No. 10373-78-1) and ethyl 4-(dimethylamino)benzoate (EMBO, CAS No. 10287-53-3), as well as Nourish type I photoinitiators, especially 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO, CAS No. 75980-60-8), ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (TPO-L, CAS No. 84434-11-7), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure 819, CAS No. 162881-26-7), and bis(2,6-difluoro-3-(1-hydropyrrole-1-yl)phenyl)titanocene (Irgacure These include 784 (CAS number 125051-32-3), 2-benzyl-2-(dimethylamino)-4'-morpholinbutyrophenone (Irgacure 369, CAS number 119313-12-1), 1-butanone-2-(dimethylamino)-2-(4-methylphenyl)methyl-1-4-(4-morpholinyl)phenyl (Irgacure 379, CAS number 119344-86-4), and especially bis(4-methoxybenzoyl)diethylgermanium (MBDEGe; Ivocerin).

[0046] As component (c), the slurry according to the present invention contains ceramic and / or glass particles and / or glass ceramic particles. Ceramics are understood to be inorganic materials having a crystalline structure and are usually manufactured from the corresponding powder. Preferably, ceramics are manufactured by sintering (sintered ceramics). Oxide ceramics are preferably obtained by sintering metal oxide powder, for example, ZrO2 or Al2O3.

[0047] According to the present invention, a slurry containing glass and / or glass-ceramic particles as component (c) is preferred. Glass ceramics are typically produced from amorphous glass, particularly silicate glass, by controlled crystallization, and are materials in which a glass phase and one or more crystalline phases exist side by side in a solid. Glass or glass-ceramic particles containing leusite, apatite, and most preferably lithium disilicate crystals are particularly preferred. Glass ceramics can be produced by heat-treating (crystallizing and sintering) a well-structured glass powder that does not contain crystalline grains. Therefore, according to one embodiment, the slurry according to the present invention may contain glass powder that is not converted into the corresponding glass ceramic until the dental restoration is sintered.

[0048] In a more preferred embodiment, in addition to pure glass or glass ceramic powder, a mixture of glass powder and glass ceramic powder can be used. A preferred mixture contains 0.5 to 99.99% by weight of glass ceramic powder based on the total mass of glass and glass ceramic powder, with the proportion of glass powder preferably corresponding to the difference from 100% by weight. In this method, sintering activity and dimensional stability can be adjusted. Glass has higher sintering activity (fewer pores and a smoother surface), while glass ceramic powder has higher dimensional stability (no distortion). In addition, glass ceramic powder in the slurry is more chemically stable against ion dissolution and the formation of carbonates and other undesirable products, resulting in more stable slurry properties.

[0049] Preferred glass ceramics according to the present invention are described in detail in EP1505041 A1, EP2261184 A1, EP2377830 A1, and EP2377831 A1. Particularly preferred is the lithium silicate material described in DE10336913 A1, and particularly preferred is the lithium disilicate glass ceramic described in EP0827941 A1.

[0050] The ceramic, glass, or glass-ceramic particles used as component (c) are preferably colored, and it is particularly preferable to manufacture the core and shell structures using slurries that are colored differently. To achieve a natural appearance of dental restorations that mimics the impression of the tooth core-shell produced by dentin and enamel, the slurry for manufacturing the core is colored darker and more opaque, and the slurry for manufacturing the shell structure is colored lighter and more transparent to match natural enamel.

[0051] For this purpose, ceramic, glass, and / or glass-ceramic particles are preferably mixed with one or more pigments. Inorganic pigments, such as oxides of Pr, Tb, Ce, Co, Ni, Cu, Bi, La, Nd, Sm, Eu, Gd, and especially Fe, Mn, Cr, and Er, are particularly preferred. Also advantageous for coloring ceramic or glass-ceramic powders are AB2O4 type colored spinel compounds (where A is preferably an alkali metal or alkaline earth metal ion, and B is a transition metal ion in a higher oxidation state than A). Spinel is particularly suitable for coloring glass ceramics, especially lithium disilicate glass ceramics. The coloring component is added in the amount necessary to achieve the desired color. Preferably, the type and amount of the coloring component are selected so that tooth-colored ceramic molded articles are obtained after debinding and sintering. The color impression is only ultimately formed during sintering. Typically, each coloring component is used in an amount of 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight, based on the total mass of component (c). Alternatively, according to EP0827941 A1, ceramic, glass, or glass-ceramic powder can be colored by adding glass-colored oxides (so-called ionic coloring). Preferred glass-colored oxides are TiO2, CeO2, and / or Fe2O3.

[0052] To achieve the desired color impression, it is also possible to use a mixture of ceramics, glass, or glass-ceramic powders that are colored differently.

[0053] The particle size of component (c) is preferably in the range of 10 nm to 100 μm, more preferably 100 nm to 10 μm. This depends on the ceramic used. For Al2O3, the particle size used as component (c) is preferably in the range of 50 to 500 nm, particularly preferably 75 to 200 nm; for glass powder and / or glass ceramic powder, it is in the range of 500 nm to 50 μm, most preferably 1 to 15 μm; and for TZP-3Y zirconium dioxide, it is in the range of 50 to 500 nm, most preferably 50 to 350 nm. The particle size is preferably selected to obtain a slurry with settling stability. The specified lower and upper limits of the particle size range are the D10 and D90 values, respectively. Thus, the range of 500 nm to 50 μm means that the D10 value is 500 nm and the D90 value is 50 μm, i.e., 10 volume% of particles are smaller than 500 nm and 90 volume% of particles are smaller than 50 μm.

[0054] Furthermore, ceramic, glass, or glass-ceramic particles with particle sizes in the range of 10 to 200 nm can also be used as nano or organosols, i.e., as dispersions of nanoparticles in a solvent, a suitable monomer of component (a), or a mixture thereof. These also have D10 or D90 values.

[0055] The determination of particle size in the range of 0.1 μm to 1000 μm is preferably performed using static light scattering (SLS), for example, with a static laser scattering particle size analyzer LA-960 (Horiba, Japan) or a Microtrac S100 particle size analyzer (Microtrac, USA). The light sources used are a laser diode with a wavelength of 655 nm and an LED with a wavelength of 405 nm. By using two light sources with different wavelengths, it is possible to measure the entire particle size distribution of the sample in a single measurement run, and the measurement is performed as a wet measurement. For this purpose, an aqueous dispersion of the packing material is prepared and its scattered light is measured in a flow cell. Scattered light analysis for the calculation of particle size and particle size distribution is performed according to the Mie theory in accordance with DIN / ISO 13320. Particle size measurements in the range of 1 nm to 0.1 μm are preferably performed by dynamic light scattering (DLS) of an aqueous particle dispersion, preferably using a He-Ne laser with a wavelength of 633 nm, at a scattering angle of 90° and 25°C, for example, using a Malvern Zetasizer Nano ZS (Malvern Instruments, Malvern UK).

[0056] For aggregate and agglomerate particles, the primary particle size can be determined using TEM imaging. Transmission electron microscopy (TEM) is preferably performed using a Philips CM30 TEM at an accelerating voltage of 300 kV. For sample preparation, droplets of the particle dispersion are spread onto a carbon-coated copper grid with a thickness of 50 Å (mesh size 300 mesh), and then the solvent is evaporated. The particles are counted and the arithmetic mean is calculated.

[0057] Particularly preferred according to the present invention are the following compositions: SiO257.0~80.0wt% Al2O30~5.0wt% La2O30.1~6.0wt% MgO 0-5.0% by weight, especially 0.1-5.0% by weight ZnO 0~8.0wt% K2O 0~13.5wt% Li2O 11.0~19.0wt% P2O50~11.0wt% Color component 0~8.0% by weight Additional ingredients 0~6.0% by weight Glass and lithium disilicate glass ceramic having, Al2O3 + La2O3 is present in a concentration of 0.1 to 7.0% by weight. The amount of MgO + ZnO is 0.1 to 9.0% by weight. The following amounts of color components: Glass colored oxide 0-5.0% by weight and Colorant: 0-5.0% by weight It is a glass and lithium disilicate glass ceramic formed from glass-colored oxides and / or colorants.

[0058] Preferred glass coloring oxides are TiO2, CeO2, and / or Fe2O3. Preferred chromogens are metal oxides commonly used in dental glass ceramics, such as the inorganic pigments mentioned above, in particular commercially available isochroic chromogens, such as colored or doped spinel and / or doped ZrO2. The chromogen may be either a non-fluorescent or fluorescent material. Unless otherwise specified, all percentages herein refer to the total mass of the glass ceramic.

[0059] There is a preferred range of amounts for each component of the preferred glass or lithium disilicate glass ceramic according to the present invention. These can be selected independently of each other, as follows: SiO257.0~75.0wt% Al2O30~2.5wt% La2O30.1~4.0wt% MgO 0.1~4.0wt% ZnO 0-6.0% by weight, especially 0.1-5.0% by weight K2O 0-9.0% by weight, especially 0.5-7.0% by weight Li2O 13.0~19.0wt% P2O 50-8.0% by weight, especially 0.5-8.0% by weight Color component 0.05~6.0% by weight Additional ingredients 0~3.0% by weight.

[0060] In addition to the components mentioned, glass or lithium disilicate glass ceramics may contain other additional components, particularly B2O3, F, Na2O, ZrO2, BaO, and / or SrO. The viscosity of the residual glass phase of the glass ceramic may be influenced by B2O3 and F, which are assumed to shift the ratio to surface volume crystallization in a manner favorable to surface crystallization.

[0061] Preferably, the glass or lithium disilicate glass ceramic is essentially composed of the aforementioned components.

[0062] To produce glass or lithium disilicate glass ceramic, raw glass containing the above-mentioned components excluding the colorant is melted at a temperature of 1200 to 1650°C. For this purpose, suitable raw materials, such as carbonates, oxides, and fluorides, are thoroughly mixed and heated to a specific temperature. If colored oxides are used, they are added to the mixture. The resulting molten glass is poured into water to form glass granules, and then the glass granules are ground into a powder having the desired particle size. Subsequently, any colorant present is added to the powder. Next, the desired slurry can be produced using this glass powder. In this case, glass ceramic is formed during the sintering process. Preferably, the glass powder is subjected to heat treatment in the temperature range of 400 to 1100°C. The heat treatment induces crystallization of the initial glass, thereby playing a role in forming glass ceramic, which is present after the heat treatment is complete and can then be used to produce slip. As described above, mixtures of glass and glass ceramic powder can also be used to produce slip.

[0063] Preferred glass and lithium disilicate glass ceramics according to the present invention, as well as their manufacture, are described in detail in EP0827941 A1, and the glass ceramics specified in that specification are particularly preferred.

[0064] According to a preferred embodiment of the present invention, the particles of component (c) are surface-modified with a suitable substance. For surface modification, compounds that are chemically, i.e., ionic or covalently bonded, to the surface of ceramic, glass, and / or glass-ceramic particles are preferably used. Compounds containing any of the following are preferred: acidic groups, preferably carboxylic acids, phosphonic acids, hydrogen phosphate groups, or acidic phosphate ester groups, or silyl groups, preferably alkoxysilyl groups. The particle surface can be partially or preferably completely coated with the modifier. The modifying agent used according to the present invention is a monomer compound.

[0065] According to the present invention, in contrast to so-called adhesion promoters or coupling agents, compounds that contain only groups that react with the particle surface but do not contain radical polymerizable groups that form covalent bonds with the resin matrix (a) are particularly preferred. In this specification, such compounds are referred to as non-polymerizable surface modifiers. These compounds have the advantage that no stable bond is formed between the particle surface and the polymer matrix in the cured green, thereby simplifying the complete removal of polymer components in the debindering process.

[0066] Suitable non-polymerizable surface modifiers include, in particular, linear or branched carboxylic acids, such as formic acid, acetic acid, propionic acid, octanoic acid, isobutyric acid, isovaleric acid, pivalic acid, or phosphonic acids, such as methyl, ethyl, propyl, butyl, hexyl, octyl, or phenylphosphonic acid. Suitable silanes as non-polymerizable surface modifiers include, for example, propyltrimethoxysilane, phenyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, trimethylchlorosilane, trimethylbromosilane, trimethylmethoxysilane, or hexamethyldisilazane. Particularly preferred are acidic phosphate esters, such as dimethyl phosphate, diethyl phosphate, dipropyl phosphate, dibutyl phosphate, dipentyl phosphate, dihexyl phosphate, dioctyl phosphate, or di(2-ethylhexyl) phosphate.

[0067] Polymers, particularly polyelectrolytes such as polycarboxylic acids or polycarboxylate salts, or nonionic polymers such as polyethylene glycol or carboxymethylcellulose, are also suitable as surface modifiers for aqueous slurries. Polyelectrolytes having ionic groups, such as ammonium polycarboxylate, can be relatively easily adsorbed onto solid surfaces, thereby imparting an electric charge to the particles. In the case of organic non-aqueous slurries, polymers soluble in the polyreaction resin are preferred. Modifiers having a molecular weight in the range of 50 to 5,000 g / mol are preferred.

[0068] The surface modifier is used as needed, preferably in an amount of 0.1 to 5% by weight, particularly preferably 0.2 to 2% by weight, and most preferably 0.5 to 1.5% by weight, based on the mass of the slurry.

[0069] The slurry according to the present invention may contain one or more nonionic surfactants as component (d). Nonionic surfactants are substances that have surface activity properties that do not form ions in an aqueous medium. These are molecules that have hydrophobic and hydrophilic portions. The overall hydrophobicity of the molecule can be adjusted by selecting the length and type of the hydrophobic and hydrophilic portions.

[0070] According to the present invention, nonionic surfactants with an HLB value in the range of 3 to 16, particularly in the range of 4 to 13, and especially in the range of 4 to 10, are preferred. The HLB value is determined according to the Griffin method.

[0071] Preferred nonionic surfactants (d) include fatty alcohols, oxo alcohols, or ethoxylates of fatty acids, fatty acid esters of sugars and hydrinated sugars, alkyl glycosides, and block polymers of ethylene and propylene oxide, particularly short-chain block co-oligomers.

[0072] Particularly preferred are fatty acid esters of hydride sugars, especially those having the formula R'-CO-O-sugar, where R' is a branched or preferably linear alkyl group having 10 to 25 carbon atoms, preferably 12 to 22 carbon atoms. Linear alkyl groups having 16 to 22 carbon atoms are particularly preferred. "Sugar" preferably represents a hydride sugar residue that has been ethoxylated 1 to 5 times. Particularly preferred are fatty acid esters of sorbitol, especially sorbitan stearate, for example, sorbitan monostearate (CAS 1338-41-6).

[0073] Furthermore, a particularly preferred group of surfactants is fatty acid ethoxylates, especially those with the general formula R''-(CO)-(OCH2CH2) m The compound has an -OH group, where R'' is a branched or preferably linear alkyl group having 10 to 25 carbon atoms, preferably 12 to 22 carbon atoms. A linear alkyl group having 16 to 22 carbon atoms is particularly preferred. m is an integer from 2 to 20, preferably 2 to 10, and particularly preferably 2 to 6.

[0074] A particularly preferred surfactant according to the present invention is an ethoxylate of a fatty alcohol, particularly one of the general formula R-(OCH2CH2) n The polyalkylene glycol ether has an -OH group, where R is an alkyl group having 10 to 20 carbon atoms and n is an integer from 2 to 25. R can be a branched or preferably linear alkyl group, with a 12 to 22 carbon atom alkyl group being particularly preferred, and a linear alkyl group having 12 to 22 carbon atoms being particularly preferred. Particularly preferred alkyl groups are lauryl, cetyl, cetearyl, and stearyl.

[0075] Polyalkylene glycol ethers are obtained by reacting the corresponding fatty alcohol with ethylene oxide (EO). The subscript n indicates the number of ethylene oxide residues. Polyalkylene glycol ethers having 2 to 21 (n=2 to 21), particularly 2 to 12 (n=2 to 12), and especially 2 to 5 (n=2 to 5) ethylene oxide groups are preferred.

[0076] Examples of preferred polyalkylene glycol ethers according to the invention are compounds in which R is a cetyl group (C 16 group) and n is 20, especially 2. These compounds have the INCI names cetes-2 and cetes-20. For example, cetes-2 has the formula C 16 H 33 -(OCH2CH2)2-OH.

[0077] Even more preferred are compounds in which R is a stearyl group (C 18 group) and n is 2, 10, 20, or 21. These compounds have the INCI names steareth-2, steareth-10, steareth-20, and steareth-21. For example, steareth-2 has the formula C 18 H 37 -(OCH2CH2)-OH.

[0078] Particularly preferred nonionic surfactants are steareth-20 (HLB = 15.3), steareth-10 (HLB = 12.4), cetes-20 (HLB = 12.9), especially steareth-2 (HLB = 4.9) and cetes-2 (HLB = 5.3).

[0079] Mixtures of different nonionic surfactants, especially different polyalkylene glycol ethers, can also be used.

[0080] INCI stands for International Nomenclature of Cosmetic Ingredients. This is an international guideline for the correct declaration of raw materials in cosmetics. According to the invention, it has surprisingly been found that by using nonionic surfactants usually used in the manufacture of cosmetics and pharmaceuticals, the properties of slurries for stereolithographic production of ceramic and glass-ceramic bodies are significantly improved.

[0081] It has been found that the nonionic surfactant used in accordance with the present invention can be homogeneously miscible with radical polymerizable monomers, particularly acrylates and methacrylates, and does not inhibit the polymerization of these monomers. Therefore, high reactivity and short exposure and processing times can be ensured in stereolithography processing of the slurry in liquid state according to the present invention. Advantageously, the nonionic surfactant can also be readily miscible with short-chain, polar, and highly reactive monomers.

[0082] The nonionic surfactants according to the present invention are solid at temperatures preferably <20°C, and particularly preferably <30°C. As a result, they lead to the solidification of the slurry, i.e., the slurry has a viscosity ranging from paste-like to solid at temperatures of <20°C, preferably <30°C. One advantage of this is that homogeneous solidification prevents particle sedimentation and thus significantly improves storage stability when stored in a solid state at room temperature. In addition, the nonionic surfactants improve the strength of the polymerized material (green body) at room temperature compared to the green body prepared from a slurry without component (d).

[0083] Preferably, the slurry contains a nonionic surfactant having a melting point of 20°C to 120°C, preferably 20°C to 100°C, and particularly preferably 20°C to 60°C. The slurry components can be homogeneously mixed at temperatures above the melting point of component (d) and solidify homogeneously at temperatures below the melting point of (d). This effectively prevents particle sedimentation at temperatures below the melting point of component (d). This ensures the long-term stability of the mixture.

[0084] The nonionic surfactant used in accordance with the present invention has particular advantage in that it effectively prevents premature sedimentation of particles even in a liquid state, resulting in high stability of the slurry during processing.

[0085] The excellent dispersion properties of nonionic surfactants for particles allow for significantly higher concentrations of ceramic, glass, and / or glass-ceramic powders to be packed into the slurry, resulting in a higher green density.

[0086] A further advantage of the preferred nonionic surfactant (d) according to the present invention is that, due to their relatively low molecular weight, they melt during debinding and leach out or evaporate from the matrix. They do not hinder the debinding process but rather create channels that promote the release of decomposition products of the organic matrix, thus facilitating debinding. During the heating process in the oven, molecules of the nonionic surfactant (d) located between the polymer chains of the matrix leach out of the green body in liquid form, and subsequently the polymerized portion of the mixture is depolymerized and then thermally decomposed. Thus, the risk of defects during the debinding process, such as cracks or even fracture of the molded body, is reduced at least significantly and is usually completely eliminated. In addition, the leachate / evaporation of component (d) allows for a rapid further heating process until all organic components are completely removed, as some of the organic mass has already been removed at relatively low temperatures, whereas conventional methods only allowed for relatively low heating rates.

[0087] In addition to the components described above, the slurry according to the present invention preferably further contains at least one additive selected from colorants, UV absorbers, fluorescent whitening agents, solvents, inhibitors, binder removal accelerators, defoaming agents, and / or film formation inhibitors.

[0088] As colorants, organic dyes, particularly azo dyes, carbonyl dyes, cyanine dyes, azomethine and methine, phthalocyanine, and dioxazine are preferred. Particularly preferred are dyes soluble in slurry, especially azo dyes. A particularly preferred dye is (4-(4-nitrophenylazo)aniline (Disperse Orange 3, CAS number 730-40-5). Furthermore, dyes that absorb in the same wavelength range as the polymerization initiator are particularly preferred. Particularly preferred are dyes that have an absorption maximum corresponding to the wavelength of light used for curing. Dyes having an absorption maximum in the range of 350-550 nm, preferably 380-480 nm, are very advantageous.

[0089] In contrast to coloring components used for coloring ceramic or glass-ceramic powders, colorants are understood here to be substances that burn completely during debinding and sintering. These colorants are used simply to color the slurry and thus to facilitate its processing. They are not used for coloring ceramics. Coloring can help make it easier to distinguish between slips. In addition, dyes absorb transmitted light during stereolithography printing, reducing its penetration depth into the material, making it possible to print objects with greater precision, which is particularly advantageous in slips with very high transparency.

[0090] Preferred UV absorbers: 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol], 2,2',4,4'-tetrahydroxybenzophenone, 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol, 2,2'-benzene-1,4-diylbis(4h-3,1-benzoxazin-4-one), 2-(4,6-bis(2,4-dimethylphenyl)-1,3, These are 5-triazin-2-yl)-5-(octyloxy)-phenol, 2-(2-hydroxy-5-methylphenyl)benzotriazole, and 2-(2H-benzotriazole-2-yl)-6-dodecyl-4-methylphenol. A preferred fluorescent whitening agent according to the present invention is 2,5-bis(5-tert-butyl-benzoxazole-2-yl)thiophene. Particularly preferred are UV absorbers and fluorescent whitening agents having an absorption maximum corresponding to the wavelength of light used for curing.

[0091] As a solvent, an organic solvent is preferred, particularly one with a boiling point of at least about 120°C, preferably 150-250°C, so that premature evaporation does not occur during stereolithography of the slurry. A mixture of solvents that can gradually vaporize in the temperature range of 150-250°C is particularly preferred. Particularly preferred are n-octanol, triethylene glycol divinyl ether, 2-amino-2-methyl-1-propanol, 2-methyl-2,4-pentanediol, tripropylene glycol, tetraethylene glycol, triethylene glycol, triethyl citrate, ethyl acetoethyl, cyclohexanol, cyclohexanone, diethylene glycol monomethyl ether, dibutyl oxalate, 2,5-dimethoxytetrahydrofuran, polyethylene glycol 300, 1- or 2-nonanol, diethylene glycol diethyl ether, and mixtures thereof.

[0092] Preferred solvents also include polyethylene glycol (PEG), polypropylene glycol (PPG), PEG-PPG copolymer, glycerol and glycerol derivatives, particularly ethoxylated and / or propoxylated glycerols, as well as phthalates, benzoates, and alicyclic esters. Particularly preferred are solvents with an Mw of less than 5,000 g / mol, preferably less than 1,000 g / mol. Suitable solvents are compounds that are liquid at room temperature and do not react with other components of the slurry under storage and application conditions. Particularly preferred solvents are PEG 200-600 g / mol, PPG 200-800 g / mol, Co-PEG-PPG 200-800 g / mol, polypropylene glycol about 400 g / mol, diethyl phthalate, dimethyl phthalate, ethyl benzoate, butyl benzoate, benzyl benzoate, diethylene glycol dibenzoate, and 1,2-cyclohexanedicarboxylic acid diisononyl ester. Advantageously, mixtures of these solvents can also be used.

[0093] The solvent is preferably used in a total amount of 0 to 50% by weight, and particularly preferably 3 to 20% by weight, based on the mass of the slurry.

[0094] The evaporation of the above solvent was found to further promote the formation of micropores within the green material. These pores close in the same way as channels formed by the efflux or evaporation of nonionic surfactants during sintering. They facilitate the release of gases during debinding and thus prevent the formation of stress and cracks. In addition, the risk of separation of layers produced by stereolithography is reduced, and the complete removal of all organic components is promoted.

[0095] Alternatively, the porosity of the green material can be increased by extracting and removing extractable components before heat treatment. Suitable extractable components must be adapted to the extractant. For oxide ceramic particles, water can be used as the extractant. In this case, water-soluble polymers, such as polyvinyl alcohol, polyvinylpyrrolidone, and polyethylene glycol, are preferred. For water-sensitive ceramic, glass, and glass-ceramic particles, organic solvents (particularly nonpolar solvents) can be used for extraction. In this case, for example, petroleum-soluble substances, such as long-chain fatty acid esters, are preferred as extractable components. The preferred amount of extractable components is 0 to 30% by weight, particularly preferably 1 to 20% by weight, based on the mass of the slurry.

[0096] The slurry according to the present invention may advantageously contain inhibitors as stabilizers, as further additives to prevent spontaneous polymerization reactions. The inhibitors or stabilizers improve the storage stability of the slurry and also prevent uncontrolled polymerization reactions in the stereolithography tank. The inhibitor is preferably added in an amount such that the slurry is stable during storage for about 2 to 3 years. Particularly preferably, the inhibitor is used in each case in an amount of 0.001 to 1.0% by weight, most preferably 0.001 to 0.50% by weight, based on the total mass of the slurry.

[0097] Preferred are so-called aerobic inhibitors, particularly phenols, such as hydroquinone monomethyl ether (MEHQ) or 2,6-di-tert-butyl-4-methylphenol (BHT), which are effective only in the presence of oxygen and are preferably used in a concentration range of 100 to 2000 ppm. Preferred anaerobic inhibitors are phenothiazine, 2,2,6,6-tetramethyl-piperidine-1-oxyl radical (TEMPO), iodine, and copper(I) iodide. These are already effective even in the absence of oxygen, preferably at low concentrations of 10 to 50 ppm. Polymerization occurs only when these additives are consumed. It is advantageous to use a mixture of aerobic and anaerobic inhibitors.

[0098] Preferably, in each case, an aerobic inhibitor is used in an amount of 0.001 to 0.50% by weight and an anaerobic inhibitor in an amount of 0.001 to 0.02% by weight, based on the total mass of the slurry. The preferred mixture also contains 0.005 to 0.10% by weight of an aerobic inhibitor and 0.001 to 0.01% by weight of an anaerobic inhibitor, based on the total mass of the slurry.

[0099] According to further embodiments of the present invention, the slurry contains a so-called debinder accelerator as an additional additive. This is used in each case in an amount preferably 0 to 20% by weight, and particularly preferably 0.01 to 10% by weight, based on the total mass of the slurry. The debinder accelerator is a substance that promotes the removal of the binder during the debindering process.

[0100] The debinding of green bodies can be promoted or particularly influenced by polymerization reactive substances in polymerization reactive resins, for example. On the other hand, these are additives that affect network formation, such as chain transfer reactive substances, so-called chain modifiers, which lead to a decrease in polymer network density, thereby resulting in good thermal decomposition. For example, known chain modifiers for radical polymerization are mainly mercaptans, such as lauryl mercaptan and disulfides. Disulfides, in particular dithiourethane disulfides, such as tetramethylthiuram disulfide or isopropyl xanthogenic acid disulfide, act as so-called photoinitiators during radical photopolymerization. These compounds act as photoinitiators (photoini-) and are involved in transfer reactions (-fer-) and termination reactions (-ter) (see T. Ostsu, M. Yoshida, Makromol. Chem., Rapid. Commun. 3 (1982) 127-132: Role of Initiator-Transfer Agent-Terminator (Iniferter) in RadicalPolymerizations: Polymer Design by Organic Disulfides as Iniferters). The addition of chain transfer active substances, i.e., chain modifiers or photoinifers, reduces the network density of the polymerization reaction network without substantially changing the reactivity of the polymerization reaction resin mixture. Chain modifiers and photoinifers are used in amounts of preferably 0.005 to 25% by weight, and particularly preferably 0.01 to 10% by weight, respectively, relative to component (a).

[0101] Comonomers that reduce the thermal stability of the polymer network can also be used as debinder accelerators. Comonomers containing thermally unstable groups, such as peroxides, azos, or urethane groups, that are incorporated into the polymer network during the stereolithography process and then promote the decomposition of the polymer network in the thermal debinder process are suitable for this purpose. A preferred example of a polymerizable peroxide is 4,4'-divinylbenzoyl peroxide, which can be obtained by reacting 4-vinylbenzoyl chloride with sodium peroxide. A preferred example of a polymerizable azo compound is an ester of 2-hydroxyethyl methacrylate with 4,4'-azobis-(4-cyanovaleric acid). Preferred thermally unstable urethanes can be obtained from diisocyanates, for example, by reacting 2,2,4-trimethylhexamethylene diisocyanate (TMDI) or toluene diisocyanate (TDI) with hydroxypropyl acrylate (HPA) or 2-hydroxyethyl acrylate (HEA). Another example of a thermally unstable monomer building block is α,α,α',α'-tetramethyl-1,4-benzenedimethyl acrylate, which, when incorporated into, for example, the Michael addition network of diacrylates and diacetacetates, leads to accelerated degradation of the polymer network in the presence of a catalytic amount of acid.

[0102] Comonomers whose polymerization reaction products are readily thermally decomposable are also suitable as binder removal accelerators. For example, α-methylstyrene, which has a low ceiling temperature T c Comonomers having this property are preferred for radical polymerization resins. The ceiling temperature is the critical temperature at which polymerization is in equilibrium with depolymerization, and can be calculated from the quotient of polymerization enthalpy and polymerization entropy (H.-G. Elias, Makromolekuele [Macromolecules], Vol. 1, 6). th See ed., Wiley-VCH, Weinheim et al. 1999, 193 ff.). For example, the T of α-methylstyrene. c The temperature is 61°C. Ceiling temperature T of polytetrahydrofuran (PTHF)C The temperature is 80°C. Therefore, by using, for example, a telechelic polymer, particularly a PTHF di(meth)acrylate telechelic polymer, as a comonomer, the decomposition of the poly(meth)acrylate network can be accelerated. According to the present invention, comonomers with a ceiling temperature of -10 to 150°C, preferably 10 to 150°C, and particularly preferably 20 to 130°C are particularly suitable. The comonomer is used in an amount of preferably 0.1 to 30% by weight, and particularly preferably 0.5 to 20% by weight, based on component (a).

[0103] Furthermore, the slurry according to the present invention may contain additives that promote oxidative decomposition of the polymer matrix during the debinding process, such as peroxides that are stable at room temperature, or even catalytically active components that enable catalytic debinding. In addition to peroxides, other substances having an oxidizing effect, such as nitric acid, or other substances that separate or form oxidizing agents are also preferred.

[0104] In addition, the slurry according to the present invention may contain an antifoaming agent and / or a film-forming inhibitor to prevent foam formation during slurry production or film formation during slurry processing. The antifoaming agent and / or film-forming inhibitor is used in an amount of preferably 0 to 5% by weight, and particularly preferably 0.1 to 2% by weight, in the organic matrix based on the mass of component (a).

[0105] The rheological properties of the slurry according to the present invention are preferably adjusted so that its viscosity is in the range of 200 to 200,000 mPa·s, and particularly preferably in the range of 500 to 100,000 mPa·s. The viscosity is determined at a desired processing temperature of the slurry using a plate-plate viscometer with a shear rate of 20 / s. The processing temperature is preferably in the range of 10 to 100°C, more preferably in the range of 15 to 60°C, and most preferably in the range of 20 to 50°C.

[0106] The slurry according to the present invention preferably has the following composition: - 5-65% by weight, preferably 9-57% by weight, and particularly preferably 10-40% by weight of monomer (a); - 0.001 to 1.0% by weight, preferably 0.01 to 1.0% by weight, and particularly preferably 0.05 to 1.0% by weight of a photoinitiator (b); - 33-90% by weight, preferably 40-88% by weight, particularly preferably 56-86% by weight of ceramic, glass, and / or glass-ceramic particles (c); - If necessary, 1 to 30% by weight, preferably 2 to 15% by weight, and especially preferably 3 to 10% by weight of a nonionic surfactant (d) It holds.

[0107] Ceramic, glass, and / or glass-ceramic particles (c) are preferably colored by the method described above and mixed with, for example, a coloring pigment.

[0108] Furthermore, the slurry is preferably - A colorant for slurry coloring in an amount of 0 to 0.2% by weight, preferably 0 to 0.05% by weight, and particularly preferably 0 to 0.02% by weight; and / or - 0.1 to 5% by weight, preferably 0.2 to 2% by weight, particularly preferably 0.5 to 1.5% by weight of a surface modifier; and / or - 0 to 50% by weight, preferably 5 to 20% by weight, and particularly preferably 5 to 10% by weight of a solvent It contains.

[0109] Unless otherwise specified, all figures refer to the total weight of the slurry. The coloring components used to color the ceramic, glass, and / or glass-ceramic particles are included in the amounts stated for component (c).

[0110] According to the present invention, core and shell structures are manufactured using slurries of the same category, namely glass, glass ceramic, or ceramic slurry, where the slurries may be colored differently. According to a particularly preferred embodiment of the present invention, core and shell structures are manufactured using glass ceramic, particularly preferably lithium disilicate glass ceramic slurry, which differ only in color and opacity after sintering, and are otherwise identical in composition. In this method, a particularly good fit is achieved between the thermal expansion coefficient of the slip and sintering shrinkage. If aesthetic aspects are not of great importance, the core and shell structures can also be manufactured from the same slip.

[0111] It can be advantageous to manufacture the shell structure using a slurry containing ceramic, glass, and / or glass-ceramic particles (c) in a minimum lower or higher content than the slurry used to manufacture the core structure. Preferably, the deviation is ±1% by weight or less. This results in a slightly larger sinter shrinkage of the shell structure. The resulting tension stabilizes the dental restoration. This is especially true for one-piece shell structures that form a closed shell completely enclosing the core. When using bonding slip, a slightly different sinter shrinkage is particularly advantageous.

[0112] Furthermore, it can be advantageous to manufacture the shell structure using a slurry containing ceramic, glass, and / or glass-ceramic particles with a lower softening temperature (glass transition temperature) than the slurry used to manufacture the core. The difference in softening temperatures is preferably ≤50°C. This can improve the gloss of the dental restoration. In addition, if the softening temperatures of the core and shell materials are different, sintering can be controlled so that the porosity of the core is higher than that of the shell structure. Generally, the purpose of sintering is to achieve the highest possible density of the shell structure. If the density of the core is lower than that of the shell structure, it will appear more opaque compared to the shell structure, which gives the restoration a more natural appearance.

[0113] The slurry having the composition specified above is preferably also used for joining the core and shell structure green bodies. The color and transparency of this joining slip are preferably selected so that they are between the color and translucency of the core and shell structures. When using a joining slip, it is preferable to provide a joining gap of preferably 10 to 300 μm in width in at least a portion of the area between the core and shell structure. The core and shell green bodies can be joined, for example, by applying the joining slip to the core green body and then placing the shell structure green body(s) on the core green body under slight pressure. Then, the excess joining slip is removed.

[0114] The use of joint slip and joint gap has the advantage that so-called fixed webs, support structures, etc., formed during the printing of molded parts simply need to be removed before joining to the extent that they exceed the dimensions of the joint gap. Smaller residues and inaccuracies are offset by the joint gap and joint slip.

[0115] Joint slips are primarily used to secure parts after joining. They should be stable so as not to flow out during application and to form a stable slurry layer, and should have sufficient strength and adhesion after joining. During joining, the parts to be joined are aligned to fit their shapes. If necessary, joining can be facilitated by, for example, a vibrating table. The fixation of parts by the joint slip is usually sufficient for further processing of the green body, and as a result, photocuring of the joint slip is not absolutely necessary, but can be advantageous.

[0116] The slurry according to the present invention has sedimentation stability in the liquid state. After debinding, sintering, and cleaning, they provide good green body strength as well as high dimensional stability, accuracy, and precision. The green bodies have high green body density and can be debinding without deformation, cracking, or stress formation. During sintering, they yield high-strength ceramics suitable for dental purposes. During sintering, densities of >98% of the theoretical density can be easily achieved. The slip is particularly suitable for the manufacture of ceramic or glass-ceramic compacts, and especially for the manufacture of dental restorations, such as inlays, onlays, veneers, crowns, bridges, or frameworks.

[0117] Green bodies are preferably manufactured using stereolithography. Stereolithography printing is computer-aided based on CAD data. The necessary data is acquired in the usual manner by optical or mechanical digitization, either in the patient's mouth (intraoral) or based on a model (extraoral). Based on this dataset, the core and shell structures of the dental restoration are then designed on a computer. Tooth models stored in a database can be used for this. Two datasets are then created under software control, and these are used to print the core and shell structures independently of each other. When designing the restoration, shrinkage behavior related to the material is taken into account accordingly.

[0118] Green bodies manufactured by the printing process already possess relatively high strength and can be handled without any problems. The core and shell structures are preferably cleaned and then assembled to form the green bodies of dental restorations. Because the sintering shrinkage and thermal expansion coefficients are generally compatible, the green bodies can be manufactured by precisely fitting them together, and as a result, they can be held together after joining by shape fitting and / or mechanical fitting methods without the use of bonding slips, and can be debindered and sintered. However, it is preferable to use bonding slips to join the parts, especially when the shell structure does not completely enclose the core structure and / or consists of multiple parts.

[0119] Stereolithography of core and shell structures offers several advantages, including the ability to produce molded parts with extremely high precision, such as the complete absence of milling marks. Another advantage is that only one debindering and sintering process is required, significantly reducing the time required to manufacture dental restorations.

[0120] After sintering, dental restorations can be glazed as needed and individually characterized using dental ceramic stains.

[0121] The method and materials used according to the present invention are suitable for the manufacture of dental restorations for the restoration of several teeth, such as bridges, and especially for the manufacture of dental restorations for the restoration of a single tooth, such as inlays, onlays, veneers, and especially crowns. The multilayer structure of the restoration makes it possible to achieve improved aesthetics. However, by bonding the core and shell structures in a green state and then sintering the parts together, the multilayer structure requires virtually no additional effort compared to the manufacture of a one-piece restoration. The preferred slurry according to the present invention also provides high green strength, which allows for safe handling of the green body and ensures high stability during debinding. In addition, the green body can be debinding very well even after bonding.

[0122] A method for manufacturing an all-ceramic dental restoration having an integrated core and shell structure, comprising: constructing a digital construction model of the dental restoration; then dividing the obtained CAD dataset into at least two separate CAD sub-datasets, one sub-dataset defining the contour of the core structure and a second sub-dataset defining the contour of the shell structure; manufacturing the green body of the core structure using the first CAD sub-dataset and manufacturing the green body of the shell structure of the restoration using the second CAD sub-dataset; then joining the core structure and shell structure in a green state; then subjecting the green body to heat treatment to remove the binder; and subsequently sintering the parts to obtain a finished dental restoration. This process enables the manufacture of a dental restoration with improved aesthetics compared to the manufacture of an integrated restoration, without significant additional effort.

[0123] The present invention will be described in more detail below with reference to the drawings and examples of embodiments.

[0124] The present invention provides, for example, the following items. 1. A process for manufacturing all-ceramic dental restorations having an integrated core structure and a single-part or multi-part shell structure, In the first step, a digital construct model of the dental restoration is constructed, and then the CAD dataset of the restoration obtained in this manner is divided into at least two separate CAD sub-datasets, the first sub-dataset defining the contour of the core structure, and the second sub-dataset defining the contour of the shell structure. Next, the dental restoration is manufactured using the generated data record, and the process is as follows: In a subsequent step, the first slurry is hardened by locally irradiating it with radiant energy using the first CAD partial dataset to form the geometric shape of the core structure, thereby fabricating the green body of the core structure of the restoration. In a further step, the second slurry is hardened by locally irradiating it with radiant energy using the second CAD partial dataset to form the geometric shape of the shell structure, thereby fabricating the green body of the shell structure of the restoration. In the subsequent steps, the core structure and shell structure are combined in a green state to obtain a green body of dental restoration. In a further step, the green body of the dental restoration is subjected to heat treatment to remove the binder (de-bindering) and obtain the brown body of the dental restoration. Next, a process characterized by sintering a Brown body of a dental restoration to obtain a completed dental restoration. 2. The process described in any one of the preceding items, wherein a CAD partial dataset of a shell structure is divided into two or more CAD shell structure partial datasets, each of which contains a portion of the contour of the shell structure, and a second slip is hardened by locally introducing radiant energy using the first CAD shell structure partial dataset to form the geometric shape of the first component of the shell structure, and separately, a further slip is hardened by locally irradiating radiant energy using the second CAD shell structure partial dataset to form the geometric shape of the second component of the shell structure, and this step is repeated according to the number of CAD shell structure partial datasets, with each repetition producing one green body of further components of the shell structure, and then the core structure and the components of the shell structure are joined in a green state to obtain a green body of a dental restoration. 3. The process described in any one of the preceding items, wherein the same slurry is used to manufacture the components of the shell structure, or preferably different slurries, particularly preferably differently colored slurries are used to manufacture each component of the shell structure. 4. A process described in any one of the preceding items, wherein slurries having different colors and opacities but otherwise identical composition are used to manufacture a core structure and a shell structure. 5. The process described in any one of the preceding items, wherein a slurry containing ceramic, glass, and / or glass-ceramic particles (c) in a minimum lower or minimum higher content than the slurry used to manufacture the core structure is used to manufacture the shell structure. 6. The process described in any one of the preceding items, wherein the green bodies of the core structure and the shell structure are joined using bonding slip, and the bonding slip is cured by polymerization after joining. 7. The process described in any one of the preceding items, which involves debinding the green body of a dental restoration by heating it to a temperature of 90°C to 600°C to remove the binder. 8. A process described in any one of the preceding items, wherein a Brownian body is sintered at a temperature of 650°C to 1800°C. 9. In each case, with respect to the total mass of the slurry, (a) 5 to 65% by weight of at least one free radical polymerizable monomer, (b) 0.001 to 1.0% by weight of at least one photoinitiator, and (c) 33-90% by weight of ceramic particles and / or glass particles and / or glass ceramic particles The process described in any one of the preceding items, wherein a slurry containing is used to produce each of the green bodies. 10. The process described in any one of the preceding items, wherein a slurry containing lithium disilicate glass ceramic particles and / or glass particles for lithium disilicate glass ceramics is used to produce each of the green bodies. 11. The following composition: SiO257.0~80.0wt% Al2O30~5.0wt% La2O30.1~6.0wt% MgO 0-5.0% by weight, especially 0.1-5.0% by weight ZnO 0~8.0wt% K2O 0~13.5wt% Li2O 11.0~19.0wt% P2O50~11.0wt% Color component 0~8.0% by weight Additional ingredients 0~6.0% by weight A slurry containing glass or glass ceramic powder having the following properties is used to produce each of the green bodies: Al2O3 + La2O3 is present in a concentration of 0.1 to 7.0% by weight. The amount of MgO + ZnO is 0.1 to 9.0% by weight. The following amounts of color components: Glass colored oxide 0-5.0% by weight and Colorant: 0-5.0% by weight A process according to any one of the preceding items, formed from a glass-colored oxide and / or colorant. 12. The method according to any one of the preceding items, wherein the glass coloring oxide (one or more) is selected from TiO2, CeO2, and / or Fe2O3, and / or the colorant (one or more) is selected from doped spinel and / or doped ZrO2, and / or the additional component (one or more) is selected from B2O3, F, Na2O, ZrO2, BaO, and / or SrO. 13. The process described in any one of the preceding items, wherein a slurry containing a mixture of glass and glass ceramic powders is used. 14. A process according to any one of the preceding items, comprising using a slurry containing, as a free radical polymerizable monomer (a), aliphatic urethane diacrylate, HEA phthalate, diHEA pyromellitic acid, bisphenol A di(meth)acrylate, bis-G(M)A (addition product of (meth)acrylic acid and bisphenol A diglycidyl ether), ethoxylated or propoxylated bisphenol A di(meth)acrylate, UD(M)A, triethylene glycol di(meth)acrylate (TEGD(M)A), tricyclodecanedimethanol di(meth)acrylate, ethoxylated or propoxylated trimethylolpropane tri(meth)acrylate, tripropylene glycol diacrylate, or a mixture thereof. 15. As photoinitiators (b), a combination of camphorquinone (CAS No. 10373-78-1) and ethyl 4-(dimethylamino)benzoate (CAS No. 10287-53-3), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (CAS No. 75980-60-8), ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (CAS No. 84434-11-7), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (CAS No. 162881-26-7), bis(2,6-difluoro-3-( The process described in any one of the preceding items, comprising using a slurry containing 1-hydropyrrole-1-yl)phenyl)titanocene (CAS No. 125051-32-3), 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (CAS No. 119313-12-1), 1-butanone-2-(dimethylamino)-2-(4-methylphenyl)methyl-1-4-(4-morpholinyl)phenyl (CAS No. 119344-86-4), bis(4-methoxybenzoyl)diethylgermanium, or a mixture thereof. [Brief explanation of the drawing]

[0125] [Figure 1] Figure 1 shows a computer-designed core structure of an anterior tooth crown with mamelons in a front view.

[0126] [Figure 2] Figure 2 shows a rear view of the shell structure that fits the core structure shown in Figure 1.

[0127] [Figure 3] Figure 3 shows the printed, debindered, and separately sintered shell structure (left) and core structure (right). The shell and core structures were sintered separately to more clearly show the color difference.

[0128] [Figure 4] Figure 4 shows another view of the shell (left) and core (right) structures shown in Figure 3.

[0129] [Figure 5] Figure 5 shows an anterior crown composed of separately printed core (dentin) and shell (incisal edge) structures. The printed parts were joined in a green state and then debindered and sintered together.

[0130] [Figure 6] Figure 6 shows the anterior tooth crown after polishing and glazing, as shown in Figure 5. [Examples]

[0131] Example 1 Fabrication of core and shell structures for anterior tooth crowns A crown for an incisor was designed on a computer using standard CAD software (EXOCAD v3.2; exocad GmbH, Rosa-Parks-Str.2, D-64295 Darmstadt, Germany). The dataset was then divided into two sub-datasets. The first sub-dataset defines the core structure of the crown shown in Figure 1, and the second sub-dataset defines the integrated shell structure shown in Figure 2. A 35 μm wide junction gap was created between the core and shell structures. Both the core and shell structures have cusps that mimic natural mamelons. These structures facilitate the joining of the core and shell structures and give the dental restoration a natural appearance after joining.

[0132] The partial datasets were separately converted into processing data for a stereolithography printer (Prograprint PR5; Ivoclar Vivadent AG) using standard CAM software (PrograPrint CAM software V1.2, Ivoclar Vivadent AG, Bendererstr.2, 9494 Schaan, Liechtenstein). To ensure slurry fluidity, the printer was operated in a climate chamber at 40°C. The core and shell structures were then printed separately under computer control. The slurry composition used was as follows: [Table 1] 1) According to EP0 827 941 A1 2) Particle size range: 500 nm~50 μm

[0133] The printed green material was washed by rinsing with water and dried by blowing compressed air. Next, the resulting green material was debindered by heating it in a furnace (Nabertherm L9 / 11 BO; Lilienthal Bremen, Germany) to 500°C at a heating rate of 0.2 K / min for 30 minutes, and then sintered in a sintering furnace (Programat P510; Ivoclar Vivadent AG; Schaan, Liechtenstein) to 890°C at a heating rate of 10 K / min for 5 minutes. The sintered structure is shown in Figures 3 and 4. Example 2 Fabrication of anterior tooth crowns

[0134] Anterior tooth crowns were designed using the method described in Example 1 and fabricated using the slips shown in the table below. [Table 2] 1) According to EP 0 827 941 A1 2) Particle size range: 500 nm~50 μm

[0135] The printed green material was cleaned by rinsing with water and dried with compressed air. The support structure at the cutting edge was removed using a rotary cutting disc (a standard dental tool). Next, bonding slip was applied to the joint surfaces of the core and shell, and after pressing the two molds together to form a mating shape, the excess bonding slurry was removed.

[0136] The bonded green material was then photocured using a dental light-curing unit (PrograPrint Cure, Program Wax, Ivoclar Vivadent AG) to increase its degree of polymerization. The bonding slurry was also cured.

[0137] Next, the obtained green body was debindered by heating it to 500°C at a heating rate of 0.2 K / min for 30 minutes in a furnace (Nabertherm L9 / 11 BO, Lilienthal Bremen, Germany), and then sintered by heating it to 890°C at a heating rate of 10 K / min for 5 minutes in a sintering furnace (Programat P510; Ivoclar Vivadent AG; Schaan, Liechtenstein). The resulting crown is shown in Figure 5. Subsequently, the crown shown in Figure 5 was polished. The finished crown is shown in Figure 6.

[0138] The slurry used to manufacture the shell structure had a slightly lower packing density than the slurry used to manufacture the core. Consequently, it exhibited a slightly higher sintering shrinkage than the core slurry, which led to improved bonding between the core and shell structures during sintering. The packing level of the bonding slip was between that of the core slurry and the shell slurry, resulting in good transition between the core and shell.

Claims

1. A process for manufacturing all-ceramic dental restorations having an integrated core structure and a single-part or multi-part shell structure, In the first step, a digital construction model of the dental restoration is constructed, and then the CAD dataset of the restoration obtained in this manner is divided into at least two separate CAD sub-datasets, the first sub-dataset defining the contour of the core structure, and the second sub-dataset defining the contour of the shell structure. Next, the dental restoration is manufactured using the generated data record, and the process is as follows: In a subsequent step, the first slurry is hardened by locally irradiating it with radiant energy using the first CAD partial data set to form the geometric shape of the core structure, thereby producing the green body of the core structure of the restoration. In a further step, the second slurry is hardened by locally irradiating it with radiant energy using the second CAD partial data set to form the geometric shape of the shell structure, thereby producing the green body of the shell structure of the restoration. In a subsequent step, the core structure and the shell structure are combined in a green state to obtain the green body of the dental restoration. In a further step, the green body of the dental restoration is subjected to heat treatment to remove the binder (de-binder) and obtain the brown body of the dental restoration. Next, a process characterized by sintering the Brown body of the dental restoration to obtain the completed dental restoration.

2. The process according to claim 1, wherein the CAD partial dataset of the shell structure is divided into two or more CAD shell structure partial datasets, each of which includes a portion of the contour of the shell structure, and a second slip is hardened by locally introducing radiant energy using the first CAD shell structure partial dataset to form the geometric shape of the first component of the shell structure, and separately, a further slip is hardened by locally irradiating radiant energy using the second CAD shell structure partial dataset to form the geometric shape of the second component of the shell structure, and this step is repeated according to the number of CAD shell structure partial datasets, with each repetition producing one green body of further components of the shell structure, and then the core structure and the components of the shell structure are joined in a green state to obtain the green body of the dental restoration.

3. The process according to claim 2, wherein the components of the shell structure are manufactured using the same slurry, or preferably different slurries, particularly preferably differently colored slurries are used to manufacture each component of the shell structure.

4. The process according to any one of claims 1 to 3, wherein a slurry having different color and opacity but otherwise identical composition is used to manufacture the core structure and the shell structure.

5. The process according to one of claims 1 to 3, wherein a slurry containing ceramic, glass, and / or glass-ceramic particles (c) in a minimum lower or minimum higher content than that of the slurry used to manufacture the core structure is used to manufacture the shell structure.

6. The process according to any one of claims 1 to 3, wherein the green bodies of the core structure and the shell structure are joined using a bonding slip, and the bonding slip is cured by polymerization after joining.

7. The process according to any one of claims 1 to 3, wherein the green body of the dental restoration is debindered by heating it to a temperature of 90°C to 600°C to remove the binder.

8. The process according to any one of claims 1 to 3, wherein the Brownian body is sintered at a temperature of 650°C to 1800°C.

9. In each case, with respect to the total mass of the slurry, (a) 5 to 65% by weight of at least one free radical polymerizable monomer, (b) 0.001 to 1.0% by weight of at least one photoinitiator, and (c) 33 to 90% by weight of ceramic particles and / or glass particles and / or glass ceramic particles The process according to any one of claims 1 to 3, wherein the slurry containing is used to produce each of the green bodies.

10. The process according to claim 9, wherein a slurry containing lithium disilicate glass ceramic particles and / or glass particles for lithium disilicate glass ceramics is used to produce each of the green bodies.

11. The following composition: SiO ２ 57.0–80.0% by weight Al ２ O ３ 0–5.0% by weight La ２ O ３ 0.1–6.0% by weight MgO 0-5.0% by weight, especially 0.1-5.0% by weight ZnO 0-8.0% by weight K ２ 0~13.5% by weight Li ２ O 11.0~19.0% by weight P ２ O ５ 0–11.0% by weight Color component 0-8.0% by weight Additional ingredients 0-6.0% by weight A slurry containing glass or glass ceramic powder having the above is used to produce each of the green bodies. Al ２ O ３ +La ２ O ３ However, it is 0.1 to 7.0% by weight. The amount of MgO + ZnO is 0.1 to 9.0% by weight. The aforementioned color components are in the following amounts: Glass colored oxide 0-5.0% by weight and Colorant: 0-5.0% by weight The process according to claim 10, formed from a glass-colored oxide and / or colorant.

12. The glass coloring oxide (one or more types) is TiO ２ , CEO ２ , and / or Fe ２ O ３ Selected from and / or the chromogen (one or more types) is doped spinel and / or doped ZrO ２ Selected from, and / or the additional components (one or more) are B ２ O ３ , F, Na ２ O, ZrO ２ The process according to claim 11, selected from BaO and / or SrO.

13. The process according to claim 9, wherein a slurry containing a mixture of glass and glass ceramic powders is used.

14. The process according to claim 9, wherein the free radical polymerizable monomer (a) is a slurry containing aliphatic urethane diacrylate, phthalic acid HEA ester, pyromellitic acid diHEA ester, bisphenol A di(meth)acrylate, bis-G(M)A (addition product of (meth)acrylic acid and bisphenol A diglycidyl ether), ethoxylated or propoxylated bisphenol A di(meth)acrylate, UD(M)A, triethylene glycol di(meth)acrylate (TEGD(M)A), tricyclodecanedimethanol di(meth)acrylate, ethoxylated or propoxylated trimethylolpropane tri(meth)acrylate, tripropylene glycol diacrylate, or a mixture thereof.

15. As photoinitiators (b), a combination of camphorquinone (CAS No. 10373-78-1) and ethyl 4-(dimethylamino)benzoate (CAS No. 10287-53-3), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (CAS No. 75980-60-8), ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (CAS No. 84434-11-7), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (CAS No. 162881-26-7), bis(2,6-difluoro- The process according to claim 9, comprising using a slurry containing 3-(1-hydropyrrole-1-yl)phenyl)titanocene (CAS No. 125051-32-3), 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (CAS No. 119313-12-1), 1-butanone-2-(dimethylamino)-2-(4-methylphenyl)methyl-1-4-(4-morpholinyl)phenyl (CAS No. 119344-86-4), bis(4-methoxybenzoyl)diethylgermanium, or a mixture thereof.

16. The process according to claim 12, wherein the at least one free radical polymerizable monomer (a) is selected from aliphatic urethane diacrylate, phthalic acid HEA ester, pyromellitic acid diHEA ester, bisphenol A di(meth)acrylate, bis-G(M)A (addition product of (meth)acrylic acid and bisphenol A diglycidyl ether), ethoxylated or propoxylated bisphenol A di(meth)acrylate, UD(M)A, triethylene glycol di(meth)acrylate (TEGD(M)A), tricyclodecanedimethanol di(meth)acrylate, ethoxylated or propoxylated trimethylolpropane tri(meth)acrylate, tripropylene glycol diacrylate, or a mixture thereof.

17. The at least one photoinitiator (b) is a combination of camphorquinone (CAS No. 10373-78-1) and ethyl 4-(dimethylamino)benzoate (CAS No. 10287-53-3), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (CAS No. 75980-60-8), ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (CAS No. 84434-11-7), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (CAS No. 162881-26-7), bis(2 The process according to claim 16, selected from ,6-difluoro-3-(1-hydropyrrole-1-yl)phenyl)titanocene (CAS No. 125051-32-3), 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (CAS No. 119313-12-1), 1-butanone-2-(dimethylamino)-2-(4-methylphenyl)methyl-1-4-(4-morpholinyl)phenyl (CAS No. 119344-86-4), bis(4-methoxybenzoyl)diethylgermanium, or a mixture thereof.

18. The process according to claim 17, wherein the slurry comprises a mixture of glass particles and glass ceramic particles as component (c).

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