Method for producing moldings, in particular dental moldings

Abstract

The present invention relates to a method for producing a molded part, in particular a dental molded part (210), from a sinterable mixed compound (200) using a cold casting mold (100) having a cavity (110) geometrically corresponding to the molded part, in particular a dental molded part (210) and at least one opening (111, 112) opening into the cavity (110), wherein the cold casting mold (100) is additively constructed from a starting material (150) by an additive material construction method, in particular a 3D printing method using a 3D printer, and the cavity (110) is produced by a digital data set, in particular a spatial model of a patient's oral cavity. The object of the present invention is to enable the production of molded parts (210), in particular dental molded parts, at lower cost and more suitable for mass production compared to the prior art. The object is to fill the cavity (110) of the cold casting mold (100) with a sinterable mixed compound (200) through at least one opening (111, 112) and to harden and / or solidify the sinterable mixed compound (200) in the cavity (110) of the cold casting mold (100), so that the gas and / or liquid contained and / or trapped in the sinterable mixed compound (200) is removed at least. The problem is solved by discharging the cold casting mold (100) from the cavity (110) through both openings (111, 112), thermally and / or thermochemically decomposing the cold casting mold (100) at a temperature in the range of 200°C to 2500°C, and sintering the sinterable mixed compound (200) at a temperature in the range of 900°C to 2500°C until a molded part (210), in particular a dental molded part (210) such as a dental restoration, is obtained.

Description

[Technical field]

[0001] The invention relates to a method for producing a molded part, in particular a dental molded part, from a sinterable mixed compound using a cold casting mold having a cavity geometrically corresponding to the molded part, in particular a dental molded part, and at least one opening opening into the cavity, in which the cold casting mold is additively built from a starting material by an additive material building method, in particular a 3D printing method using a 3D printer, and the cavity is created by means of digital data sets, in particular on the basis of a spatial model of a patient's oral cavity.

[0002] The production of mouldings by computer-aided manufacturing (CAD / CAM) is known in various technical fields. Dental mouldings, in particular dental restorations such as crowns and bridges, but also parts related to orthodontics such as dental implants and dentures or brackets, are already produced by computer-aided manufacturing (CAD / CAM) in many dental clinics and dental laboratories. In this case, a digital spatial model of the patient's oral cavity is first created. The required dental restoration is designed by means of software and the created data set is transferred, for example, to a milling machine, which cuts out the finished dental restoration from the blank. The blank is generally produced according to a cold casting method, in which a mixed compound is first produced from ceramic or metal powders suitable for dental technology. As mixed compound, for example, a paste-like substance, a slurry, a suspension or even a "dry" bulk powder can be used. A method for producing dental restorations from dental metal powder is known from EP 2 470 113. In this case, CrCo dental metal powder is mixed to a slurry, which is cold-filled into a casting mould and dried therein. The binder added to the slurry gives it sufficient shape retention after drying, so that the dried slurry is removed from the cold casting mould as a green compact and milled by a milling machine into the desired spatial shape based on the transmitted digital data set. Final (dense) sintering gives the dental restoration the required hardness and density. The material properties required for approval as a dental moulding are strictly regulated by national and / or international standards. Such cold casting methods are only suitable for the production of blanks. The fine and complex shape of the actual dental restoration is subsequently machined out of the blank by machining. Teachings on metal or ceramic slurries for dental technology are prior art and can be found, for example, in EP 1658018, EP 1047355, WO 2013007684, EP 1558170 and EP 1885278, and information regarding their preparation can be found in DE 102005023727 A1 and DE 19801534 A1.The performance of the final compaction or final sintering is also well described in the prior art, and corresponding methods and sintering furnaces can be found in EP 2765950, EP 2844412 and WO 2011020688.

[0003] When using bulk powder as the mixed compound, in order to obtain sufficient shape retention, it is generally necessary to carry out an additional process, isostatic pressing. In this case, the mixed compound is subjected to high pressure uniformly from all directions. Corresponding methods for producing ceramic dental restorations from ceramic powders, for example zirconium oxide, are also well known from the prior art. A method for producing dental parts from ceramic powders is described in WO 2008 / 114142.

[0004] Digital spatial models of the oral cavity are also used to manufacture temporary prostheses out of plastic: in this case, the dataset created for the dental restoration is transferred to a 3D printer, and the temporary prosthesis is built up layer by layer from the plastic starting material by additive material building methods (3D printing).

[0005] In the field of additive material construction, besides plastics, inorganic substances can now also be used as starting materials. Additive material construction methods such as SLM (Selective Laser Melting), extrusion methods such as FDM (Fused Deposition Molding) and FFF (Fused Filament Manufacturing) are known. Likewise additive material construction methods are known that exploit the photocuring properties of the starting materials, for example SLA or STL (Stereolithography), DLP (Digital Light Processing) and LCM (Lithography-based Ceramic Manufacturing).

[0006] Therefore, first attempts to manufacture dental restorations from metal or ceramic using additive material construction methods have already begun. A method for manufacturing dental crowns from zirconia using additive material construction methods is known from WO 2018 / 065856. However, 3D printers for metal or ceramic objects are very expensive and / or the printed mouldings do not meet the high material requirements for approval for dental use. In particular, additive material construction methods require a very high proportion of binder in the starting material (about 30%), so that the required final density or final hardness cannot be achieved or is achieved at a very high cost. The economic viability of printing dental mouldings from ceramic or metal is not in sight.

[0007] Another possibility of using digital spatial data of the oral cavity for the production of densely sintered dental restoration parts of complex shape by means of a 3D printer is disclosed in WO 2019 / 210285. For this, it is preferable to print a self-collapsing casting mold by means of a 3D printer, rather than a dental restoration. As starting material for the printing process, a two-component powder mixture is used, consisting of a sinterable alumina powder and a powdered binder with a high coefficient of thermal expansion (WAK). The printed casting mold is filled with sinterable dry zirconia bulk powder as a mixed compound. The casting mold is then sealed with a lid printed from the same material, and the (two-part) casting mold together with the zirconia bulk powder in it is isostatically pressed at a pressure of 400 MPa. The decisive factor in this method is that the bulk powder is binder-free to allow uniform pressing. The bulk powder is compressed together with the casting mold and subsequently sintered without removing the casting mold. The casting mold bursts due to the expansion of the binder contained in the casting mold during sintering. In order to remove the finished sintered part from the casting mold, the sintering temperature of the casting mold must be higher than that of the bulk powder. A disadvantage of the disclosed method is, on the one hand, the high costs associated with 3D printing of the ceramic starting material and isostatic pressing at extremely high pressures of 400 MPa. However, the use of ceramic starting materials with a higher sintering temperature than the bulk powder is crucial for the described method. On the other hand, the applicability of the method is also limited. The mixed compound used must be binder-free in order to achieve a uniform pressing. Furthermore, compression pressing methods, especially isostatic pressing, where it is desirable to apply pressure uniformly from all directions to the part, are not suitable for mixed compounds with a moisture content of more than 7%. Liquids are almost incompressible. To perform isostatic pressing, the bulk powder must be completely confined inside the closed casting mold. This ensures that any moisture contained in the mixed compound cannot escape.

[0008] The object of the present invention is therefore to provide additively constructed, in particular 3D printed, cold casting moulds which allow the production of dental moulds with complex anatomical shapes, such as those found in crowns, bridges, dental implants, abutments, dentures etc., at lower cost and in a more mass-production-friendly manner compared to the prior art. At the same time, it is desirable to broaden the application possibilities. In particular, the use of various mixed compounds made of sinterable metallic and / or ceramic materials in dry powder form or as slurries, suspensions or paste-like substances is possible.

[0009] This problem is solved by a method for producing a dental molding according to claim 1.

[0010] A method for producing moldings, in particular dental moldings, of the type described in more detail at the beginning is characterized by the following method steps: - filling the cavity of the cold casting mould with a sinterable mixed compound through at least one opening, - curing and / or solidifying the sinterable mixed compound in a cavity of the cold casting mould, allowing gas and / or liquid contained and / or trapped in the sinterable mixed compound to escape from the cavity through at least one opening, - thermally and / or thermochemically decomposing the cold casting mould at a temperature in the range of 200°C to 2500°C, - sintering the sinterable mixed compound at a temperature in the range of 900 ° C to 2500 ° C until the final hardness is reached, in particular until a dental part, such as a dental restoration, is obtained.

[0011] For this reason, according to the present invention, it is intended to use additively constructed, especially 3D printed, preferably one-piece cold casting mold for the production of molded products, especially dental molded products, which can be decomposed or dissolved by pyrolysis or combustion, preferably in one working step, thermally or thermochemically, when sintering the mixed compound into a finished molded product, especially dental molded products.In this way, damage to dental molded products, which often have a delicate structure with small wall thickness, due to the destruction or bursting of the cold casting mold or the action of other forces on the cold casting mold can be avoided.After the end of sintering, the cold casting mold is completely or almost completely decomposed thermally or thermochemically, so that additional working steps that require the cold casting mold and molded product to be separated from each other are avoided.

[0012] According to the method according to the invention, the cavity of the cold casting mould is filled, preferably after completion, selectively under pressure with a sinterable mixed compound and hardened or solidified in the cold casting mould. In particular during filling and / or hardening or solidification, and also throughout the entire process, gas and / or liquid contained and / or trapped in the mixed compound can be discharged or escape from the cavity via at least one opening. Advantageously, for this purpose, the at least one opening is likewise not sealed or remains open throughout the entire process.

[0013] The thermal and / or thermochemical decomposition of the cold casting mold can begin already during the hardening or solidification of the mixed compound or, alternatively, only after the mixed compound has completely hardened, in particular to green hardness. Preferably, the decomposition begins in the temperature range of 200°C to 650°C and is completed during final sintering at temperatures in the temperature range of 900°C to 2500°C.

[0014] The curing or solidification of the mixed compound in the cavity can be achieved in various ways, in particular by chemical reaction, which can in particular be achieved by means of a binder or a two-component binder, and depending on the choice of binder, the reaction can be initiated by different triggers, for example irradiation with a light source, in particular an ultraviolet source, the action of heat, removal of moisture, etc.

[0015] According to an advantageous variant of the method, the mixed compound is present as a slurry and / or pasty substance and comprises a diluent, in particular water, the mixed compound is allowed to harden and / or solidify by drying in the cavity of the cold casting mould, and the liquid part of the mixed compound and / or the water is allowed to exit the cold casting mould by means of at least one opening, in particular to be removed from the mixed compound.

[0016] In particular when slurries or wet / pasty substances are used as mixed compounds, but also for bulk powders, according to an advantageous design of the method at least one first opening opening into and / or leading out of the cavity and at least one second opening opening into and / or leading out of the cavity are additionally constructed in the cold casting mould, the cavity of the cold casting mould is filled via the first opening and gas, in particular trapped air and / or liquid, in particular diluent, contained and / or trapped in the sinterable mixed compound is evacuated from the cavity via the second opening.

[0017] Thus, in addition to the at least one first opening, which is provided for filling the cavity with the mixed compound, at least one second opening can be formed, which is provided for draining the fluid contained in the mixed compound. In principle, it is conceivable to form, in particular drill, the first and / or second openings after the additive construction of the cold casting mold is completed. However, it is advantageous to form the first and / or second openings directly during the additive material construction, thereby avoiding additional work steps. By forming at least one second opening, not only can the cold casting mold additively constructed according to the method according to the invention be used for mixed compounds with any moisture content, but the at least one second opening also allows evacuation, which can be assisted, for example, by shaking, when using bulk powders. In a development of this design, at least one wall bounding the cavity of the cold casting mold is additionally constructed with a number of second openings passing through this wall, which open into and / or out of the cavity for the discharge of gas, in particular trapped air and / or liquid, in particular diluent, in whole or in part.

[0018] A plurality of adjacent second openings may be pierced through one or more walls of the cold casting mold to form a sieve-like surface that allows the passage of liquids and gases while retaining solids. Preferably, the diameter of each second opening is smaller than the particle size of the powders contained in the mixed compound, such as metal powders, ceramic powders or glass-ceramic powders, and / or the size of the resulting particle agglomerates. The plurality of second openings may also be formed as pores and / or capillaries penetrating the wall, so that the wall is wholly or partially porous and / or hygroscopic.

[0019] Such a design has the advantage that moisture contained in the mixed compound is trapped or absorbed by the adjacent porous and / or hygroscopic walls and is preferably expelled from the inside towards the atmosphere surrounding the cold casting mold. This effect can be assisted by increasing the ambient temperature surrounding the cold casting mold or other measures to reduce the ambient air humidity, resulting in drier ambient air.

[0020] Thus, a variant of the method provides for the mixed compound to be cured and / or solidified in the cavity of the cold casting mold under the action of heat, in which the cold casting mold filled with the mixed compound is placed in a drying cabinet or sintering furnace, setting a temperature in the range of 30° C. to 120° C. If necessary, the surrounding air humidity can also be set to the desired value. For careful, uniform and at the same time rapid drying, an air humidity in the range of 1% to a maximum of 50% has been found to be advantageous.

[0021] The action of heat and, if necessary, the reduction of air humidity can accelerate the hardening of the mixed compound, for example in the case of a drying process. In particular, drying the surroundings, i.e. the atmosphere or ambient air present in the drying or climatic cabinet or sintering furnace, allows the moisture and / or liquid contained in the mixed compound to be rapidly expelled from the cavity to the surroundings. This effect can have a considerable influence on the drying time, in particular if the wall of the cold casting mold is designed with a porous and / or hygroscopic surface through which a plurality of second openings penetrate like pores and / or capillaries.

[0022] Usually, the volumetric shrinkage or sintering shrinkage of the molded part caused by the compression of the mixed compound occurs during the curing and / or solidification of the mixed compound and during sintering. Preferably, the digital data set based on the spatial model of the patient's oral cavity for the geometric design of the cavity of the cold casting mold includes the volumetric shrinkage caused by the sintering and / or hardening of the mixed compound.

[0023] Depending on the mixed compound used, the corresponding volume shrinkage during hardening and / or sintering of the mixed compound must be taken into account and the cavity of the cold casting mold must be formed with a correspondingly adapted (larger) initial shape. For example, sintering shrinkages in the range of 25% to 50% must be taken into account for mixed compounds containing ceramic powders, 50% to 95% for mixed compounds containing sol and zirconium oxide nanoparticles, and 8% to 25% for mixed compounds containing metal powders, respectively, relative to the initial shape. For hardening of the mixed compound by light and / or drying, a volume shrinkage of about 2% to 20% relative to the initial shape must be taken into account. For the cold casting mold itself, a volume shrinkage in the range of 1% to 10% relative to the initial shape can also be taken into account during the production of molded articles, in particular dental molded articles. The cold casting mold produced according to the method according to the invention allows for the low-cost production of molded articles, in particular dental molded articles, from a variety of mixed compounds.

[0024] In order to ensure that sufficient mixed compound is always available for the production of molded articles, especially dental molded articles, especially when volumetric shrinkage occurs, in a development, at least one compensation volume for holding the mixed compound is connected in fluid communication with the cavity of the cold casting mold, possibly via a filling channel. Preferably, the compensation volume is also integrally constructed with the cold casting mold. In particular, when using mixed compounds with a higher water content and / or when there is trapped air, the compensation volume acts as a kind of reservoir and allows the mixed compound to flow or drip in order to compensate for the volume reduction caused by the escape of gas and / or liquid from the cavity through at least one second opening.

[0025] By using organic materials, in particular organic polymers, waxes or plastics, preferably with a melting or decomposition temperature in the temperature range of 40° C. to 300° C. as starting materials for the additive construction of the cold casting mold, it is advantageous for the method if the cold casting mold is plasticizable and / or thermally and / or thermochemically decomposable. For example, waxes are a group of materials with particularly low heat resistance. By using organic materials containing wax, softening or plasticization of the cold casting mold can already be achieved at a temperature of about 35° C.

[0026] Organic materials such as waxes and / or polymers and / or plastics can be used much more easily and therefore at lower cost in additive material construction methods, for example 3D printing. Due to the relatively low heat resistance of plastics, cold casting molds additively constructed from organic materials can be plasticized or even decomposed thermally and / or thermochemically, in particular by pyrolysis and / or combustion. Advantageously, starting materials with a lower melting point, for example waxes, can be used for structures and / or walls of the cold casting mold that do not bound the cavity or are not directly connected thereto, in particular support structures, filling channels, compensation volumes, etc., than for walls that bound the cavity of the cold casting mold and are additively constructed, for example from polymers or plastics. In this way, stresses that are generated, in particular by heat, during plasticization or decomposition of the cold casting mold, which could cause damage to the molded part, can be reduced or even completely avoided. Other properties of the cold casting mold, such as water solubility, color, transparency, etc., can also be made different from each other in different areas by additive construction, in particular 3D printing, with different starting materials. Small amounts of inorganic materials may be added to the organic starting materials. For example, it is common to mix plastics with inorganic additives, however the proportion of organic components always exceeds the proportion of inorganic components.

[0027] According to a preferred method design, the mixed compound comprises a metal powder, in particular a CrCo powder, or a ceramic powder, in particular an aluminum oxide powder and / or a zirconium oxide powder, and / or a glass-ceramic powder, in particular a lithium disilicate powder, and a binder.

[0028] The mixed compound containing the binder can be hardened in the cold casting mold, in particular to green hardness, simply by drying without pressure. The use of the binder therefore makes it possible to dispense with the expensive isostatic pressing known from the prior art. In this case, however, in contrast to the methods also described in the prior art, the hardening of the mixed compound must be carried out in an open cold casting mold (without a "lid") so that the fluid can be discharged from the cavity of the cold casting mold through at least one opening. Many types of binders are known from the prior art, mostly consisting of organic substances such as resins, surfactants or waxes that provide a relatively low melting point.

[0029] In order to achieve a careful release of the cold-casting mould from the mixed compound before debinding or before the binder starts to melt, according to a variant of the method, the heat resistance and / or thermal form stability of the cold-casting mould, in particular the melting point and / or decomposition temperature of the cold-casting mould, is below the melting point of the binder and / or below the sintering temperature of the mixed compound, in particular of the metal or ceramic powder.

[0030] It is therefore preferred to allow the mixed compound to harden in the cavity of the cold casting mold, and especially to green hardness, before decomposition of the cold casting mold begins or is complete.

[0031] According to one method configuration, decomposition of the cold casting mold can be initiated or even completed by the action of heat at temperatures in the range of 200° C. to 650° C. before the mixed compound is sintered to its final hardness.

[0032] Advantageously, for this purpose the melting point and / or decomposition temperature of the cold-casting mould may be below the sintering temperature of the metal or ceramic powder.

[0033] In a development of this method, it is provided that the organic material used for the additive construction of the cold casting mold is first plasticized by the action of heat at a temperature in the range of 35°C to 300°C and then decomposed thermally by pyrolysis at a temperature in the range of 200°C to 650°C and / or thermochemically by combustion.

[0034] To facilitate the release of the mixed compound contained therein from the walls that bound the cavities, the cold casting mold filled with the mixed compound is placed in a drying or climatic cabinet or a sintering furnace, where the temperature is set in the range of 35°C to 300°C. The material properties of the organic material or plastic can be utilized here: before the melting point of the cold casting mold is reached, the organic material, especially the plastic, starts to soften, making the cold casting mold plastifiable or plastically deformable. By appropriately blowing in compressed air, the soft and deformable cold casting mold can be released from the mixed compound, which is preferably already hardened (to green hardness).

[0035] Advantageously, the thermal and / or thermochemical decomposition of the cold-casting mould is carried out in a sintering furnace, the cold-casting mould being placed in the sintering furnace together with the mixed compound therein.

[0036] In an optional method step, it is contemplated that the mixed compound is pre-sintered before the actual sintering, in particular at a temperature in the range of 650° C. to 1300° C., to remove the binder portion before compressing the molded part to its final hardness.

[0037] In this case, the thermal and / or thermochemical decomposition can be continued until completion and / or at high temperatures in the sintering temperature range of 900°C to 2500°C, thereby allowing a residue-free or at least almost residue-free decomposition of the cold-cast mold due to the action of heat.

[0038] According to a method variant, the decomposition of the cold casting mould is carried out thermally, in particular pyrolytically, under oxygen-free conditions, or thermochemically, in particular by combustion, under an oxygen supply.

[0039] In the pyrolysis of the cold casting mold under oxygen-free conditions, the cold casting mold together with the mixed compound contained therein is placed in a sintering furnace capable of sintering under vacuum and / or protective atmosphere (oxygen-low or oxygen-free). This method variant is particularly suitable for the production of metallic dental molds, for example made of CrCo alloys, to avoid damage to the molds by oxidation.

[0040] According to another process variant, however, decomposition of the cold casting moulds is also possible by combustion under an oxygen supply, in particular to obtain ceramic mouldings, in particular dental mouldings.

[0041] Finally, according to a method variant, the cold casting mould, in particular the walls bounding the cavity of the cold casting mould, can be coated with a coating agent before filling with the mixed compound, in order to avoid frictional and / or material bonds between the cold casting mould and the mixed compound.

[0042] It is conceivable that the cold casting mould is submerged in a bowl of an organic oily liquid, for example petroleum, shortly before or immediately before filling with the mixed compound, or alternatively rinsed with an organic oily liquid, for example petroleum. In this way, a heat-resistant protective layer can be easily and simply formed between the walls bounding the cavity of the cold casting mould and the mixed compound, without closing the first and / or second openings.

[0043] For dental mouldings such as crowns, bridges, dental implant parts and / or dentures, delicate thin-walled structures are often required. For the production of dental mouldings, especially from ceramics or metals, high sintering temperatures are required. In order to avoid damage to the mouldings due to the thermal expansion of the cold casting mould, the linear thermal expansion of the cold casting mould is advantageously at most 10%, preferably at most 3%, particularly preferably at most 0.8% relative to its initial shape, and the maximum thermal expansion of the cold casting mould is achieved at temperatures of 240°C or less, preferably at most 200°C, further preferably at most 150°C, particularly preferably at most 100°C. Preferably, the thermal expansion coefficient (WAK value) of the mixed compound can be adapted to the WAK value of the cold casting mould by the proportion of polyelectrolyte and binder (polymer), taking into account the respective WAK values ​​of the metal, ceramic or glass-ceramic powders used, so that the cold casting mould and the mixed compound undergo similar or identical thermal expansion. Additionally or alternatively, the mechanical stability of the mixed compound (in the green state) can be increased by increasing the proportion of binder.

[0044] In order to achieve the dimensional stability of the cold casting mold, which is required especially for dental moldings, even in the pressure-filling method, the cold casting mold has a Shore hardness of at least 15 according to Shore-A and / or at least 10 according to Shore-D, and an elastic modulus of at least 5 MPa. The walls that bound the cavity of the cold casting mold preferably each have a wall thickness of at least 0.01 mm. Shore hardness is a material parameter of elastomers and plastics and is specified in the standards DIN EN ISO 868, DIN ISO 7619-1 and ASTM D2240-00. The elastic modulus, also called tensile modulus or Young's modulus, is determined for plastics in particular according to DIN EN ISO 527-1:2019-12.

[0045] An exemplary prototype of a cold casting mold according to the invention, suitable for the production of molded articles, in particular dental molded articles, was produced according to the stereolithographic 3D printing method and has the following physical characteristics: ASTM Method Property Description Metric English D638M Tensile modulus 2100MPa 305000psi D638M Breaking strength 44.9MPa 6500psi D638M Breaking elongation 6.1% 6.1% D790M Flexural strength 74.3MPa 10770psi D790M Flexural modulus 2200MPa 329000psi D224 Hardness (Shore D) 85 85 D256A Izod Impact Strength 0.23J / cm 0.46ft lb / in D570-98 Water absorption rate 0.7% 0.7% D648 HDT at 0.46MPa (66psi) 59°C 138°F D648 HDT 50°C 122°F at 1.82MPa (264psi) It is manufactured in.

[0046] Further details, features, (sub)feature combinations, advantages and effects according to the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings. [Brief description of the drawings]

[0047] [Figure 1] 1 is a flow chart of an exemplary progression of a method according to the invention for producing a moulding, here a dental moulding, by way of example. [Diagram 2] FIG. 2 is a schematic diagram of a cold casting mold whose cavity corresponds to the shape of the dental restoration. [Diagram 3] FIG. 2 is a schematic perspective view of an embodiment of a cold casting mold with a fill channel and a compensation volume. [Figure 4] FIG. 4 is a cross-sectional view of the cold casting mold of FIG. [Diagram 5] FIG. 2 is a schematic perspective view of a second embodiment of a cold casting mold according to the invention, comprising two filling channels; [Figure 6] FIG. 2 is a schematic perspective view of a molded product produced using a cold casting mold according to the present invention.

[0048] The drawings are merely illustrative and are intended merely to aid in the understanding of the invention, and like elements are generally described only once, with like reference numbers being used.

[0049] FIG. 1 shows a flow diagram of an exemplary progression of the method according to the invention for producing a dental moulding 210. In this case, first a cold casting mould 100 is produced (1). The cold casting mould 100 is constructed by additive material construction methods, for example by means of a 3D printer, the cold casting mould 100 being constructed so as to have at least one opening 111, 112. As starting material 150, preferably a thermally and / or thermochemically decomposable plastic is used. Optionally, the cold casting mould 100 may be coated with a coating agent 220 before being filled with a mixed compound 200 (1.1). Petroleum is suitable as the coating agent 220, for example, in which case the cold casting mould 100 is preferably submerged in a bowl of petroleum. The cold casting mould 100 is then filled with the mixed compound 200 (2). Depending on the desired moulding 210, the mixed compound 200 comprises a ceramic or metal powder 209 suitable for producing dental mouldings. Preferably, the respective powder 209 is mixed with a diluent 205, for example water or an organic solvent, to form a slurry or paste-like substance, which is then mixed with a binder 206 and conditioned before use. The mixed compound 200 is filled into the cavity 110 of the cold casting mould 100 via at least one opening 111, 112. Already during filling, fluids 207, in particular the diluent 205 or entrapped air 208 contained in the mixed compound 200, can escape via the at least one opening 111, 112. After filling, the mixed compound 200 hardens or solidifies (3) inside the cold casting mould 100, more precisely in its cavity 110. To accelerate the hardening or solidification, the cold casting mould 100 is placed, for example, in a drying or climatic cabinet for adjusting the desired surrounding air humidity and exposed to heat 230, which results in a rapid drying or evaporation of the liquid components of the mixed compound 200. In this case, the fluid 207, diluent 205 or trapped air 208 can further escape via at least one opening 111, 112. In the production of a ceramic or metal dental part 210, hardening in the cold casting mold 100 is preferably carried out to green hardness. The stability of the green compact can be achieved by the use of a binder 206.

[0050] After hardening or solidification, the cold casting mold 100 with the hardened mixed compound 200 therein can be preferably first softened in a sintering furnace at a temperature ranging from 35°C to 300°C, and then "inflated", e.g., by blowing compressed air into it, so that it can be peeled away from the mixed compound 200.

[0051] Advantageously, before or during the hardening of the mixed compound 200 to the final hardness, the cold casting mold 100 is thermally or thermochemically decomposed (4). For this, thermal decomposition, i.e. under the exclusion of oxygen, or thermochemical decomposition, i.e. combustion with oxygen, of the cold casting mold 100 in a sintering furnace is started at a temperature in the range of 200° C. to 650° C., at which the starting materials 150 are completely or almost completely melted. The mixed compound 200 can optionally be pre-sintered (4.1) at a temperature in the range of 650° C. to 1300° C., during which the binder 206 evaporates. In the final final or dense sintering (5), the mixed compound 200 is compressed to the final hardness at a temperature in the range of 900° C. to 2500° C., and can be removed from the sintering furnace as the finished dental mold 210. Possible residues of the cold casting mold 100 that are not yet completely decomposed are also decomposed during the pre- or final sintering.

[0052] FIG. 2 shows an exemplary embodiment of the invention in which the cold casting mold 100 has a cavity 110 corresponding to the shape of the dental molding 210. A printing nozzle 310 of a 3D printer 300 is also shown diagrammatically in the figure, by means of which the cold casting mold 100 is additively built up from the starting material 150. The cold casting mold 100 has a first opening 111 fluidly connected to a filling channel 130 via a compensation volume 131. Through the filling channel 130, the cavity 110 is filled with a mixed compound 200 by a filling means 400, here exemplarily an injection syringe 420. Fluid 207 contained in the mixed compound 200 or trapped air 208 occurring during filling is discharged from the cavity 110 via a number of second openings 112. The second openings 112 are here formed as capillaries or pores in the outer wall 121 and therefore cannot be seen by the naked eye. The plurality of second openings 112 creates a porous or hygroscopic surface that channels fluid 207 or moisture contained in the mixed compound 200 from the cavity to the outside environment.

[0053] 3 and 4 respectively show an embodiment of a cold casting mould 100 in a schematic perspective view or in a cross-section. The cold casting mould 100 is exemplarily produced here in the form of a test piece, the cavity 110 of which has typical geometrical characteristics for a dental moulding 210, with a wall thickness of the moulding 210 in the range of 0.30 mm to 10 mm. The cavity 110 of the cold casting mould 100 is defined by an outer wall 121 and an inner wall 122 of the cold casting mould 100, so that the finished moulding 210, for example a crown, has an internal cavity 211 (see FIG. 6) which corresponds for example to the shape of an abutment, so that the crown can be fitted to the abutment. The inner wall 122 is cylindrical or frusto-conical for this purpose. A first opening 111 opens into the cavity 110 through one of the outer walls 121 which articulates against the dental moulding 210. The cavity 110 is filled with the mixed compound 200 through the first opening 111. The inner wall 122 is perforated with a number of second openings 112, which allow for example the fluids 205, 207 and / or the trapped air 208 contained in the mixed compound 200 to escape already during filling. After filling, the fluids 205, 207, 208 can optionally also leak out through the first opening 111. The number of second openings 112 may be perforated in the inner shell surface of the cavity 110 in the manner of a sieve, as exemplarily shown here. Alternatively, the number of second openings 112 can be made in the manner of pores and / or capillaries, forming a porous and / or hygroscopic surface.

[0054] A filling channel 130 having a compensation volume 131 is fluidly connected to the first opening 111. To the filling channel 130, a filling means 400, for example an injection syringe 420, in particular a low-pressure injection syringe (see FIG. 2), or a conduit such as a hose 410, can be connected to facilitate the filling of the cavity 110 with the mixed compound 200. The compensation volume 131 serves as a kind of reservoir for the mixed compound 200, so that the volumetric loss of the fluids 205, 207, 208 escaping from the second opening 112 can be compensated by the mixed compound 200 held in the compensation volume 131. In the illustrated embodiment, the cold casting mold 100 is manufactured integrally with the filling channel 130 and the compensation volume 131.

[0055] In Fig. 5 a schematic perspective view of a second embodiment of a cold casting mould 100 according to the invention is shown. This cold casting mould 100 corresponds to the first embodiment shown in Figs. 1 and 2, except that the filling channel 130 is formed without the (optional) compensation volume 131 and the channel-like second opening 112 opens integrally into the mating outer wall 121. The filling channel 130 can be implemented alternatively integrally or as an additional part of the cold casting mould 100, with its first opening 111 opening into the cavity 110. In this variant, the first opening 111 passes concentrically through the second opening 112. If necessary, a separate compensation volume 131 can be connected to the filling channel 130, in particular as a component of the filling means 400.

[0056] The mixed compound 200, hardened to the final hardness required for the dental mould 210, can be seen in FIG. 6 as the finished mould 210 produced using the cold casting mould 100 formed as a test piece. The mould 210 has a wall thickness in the range of 0.3 mm to 10 mm. In the lower tip part of the mould 210, a recess 211 is formed, the shape of which corresponds to the shape of the dental mould 210, for example an abutment for mounting a crown. Due to the plurality of second openings 112 penetrating the inner wall 122 of the cold casting mould 100 in a sieve-like structure (see FIG. 4), the inwardly facing wall of the recess 211 is provided with a noppenartigen surface 212. The noppenartigen surface 212 improves the retention between the dental mould 210, for example a crown, and for example an abutment. [Explanation of symbols]

[0057] 100 Cold casting mold 110 Cavity or tool shape 111 First opening 112 Second Opening 120 Wall 121 Exterior Wall 122 Inner wall 130 Filling Channel 131 Compensation volume section 140 Support structure 150 Starting materials 200 Mixed Compound 205 Diluent 206 Binder 207 Fluid 208 Air 209 Powder 210 Molded products 211 Recess 220 Coating Agent 230 Heat / Air Humidity 231 light 300 3D Printer 310 Printing nozzle 400 Filling means 420 Injection syringes, especially low pressure injection syringes Method process: 1. Cold casting mold manufacturing 1.1 Coating of cold cast moulds 2. Filling the cold casting mold with the mixed compound 3. Hardening and / or solidification of the mixed compound in the cold casting mold 4. Thermal or thermochemical decomposition of cold cast molds 4.1 Pre-sintering 5 Sintering / Final Sintering

Claims

1. A method for producing a molded part (210), in particular a dental molded part (210), from a sinterable mixed compound (200) using a cold casting mold (100) having a cavity (110) that corresponds geometrically to the molded part, in particular a dental molded part (210), and at least one first opening (111) that opens into said cavity (110) and / or leads from said cavity (110) to the outside, comprising the following method steps: (1) manufacturing the cold casting mold (100) from a starting material (150) by additive material construction, in particular by 3D printing using a 3D printer (300), creating the cavity (110) based on a digital data set, in particular on a spatial model of the patient's oral cavity; (2) filling the cavity (110) of the cold casting mold (100) with the sinterable mixed compound (200) through the at least one first opening (111); (3) curing and / or solidifying the sinterable mixed compound (200) in the cavity (110) of the cold casting mold (100), the cold casting mold (100) has at least one second opening (112) opening into and / or out of the cavity (110); Allowing gas and / or liquid contained and / or trapped in the sinterable mixed compound (200), particularly during steps (2) and (3), to leave the cavity (110) through the at least one second opening (112); (4) thermally and / or thermochemically decomposing the cold casting mold (100) at a temperature in the range of 200°C to 2500°C; (5) sintering the sinterable mixed compound (200) at a temperature in the range of 900°C to 2500°C to a final hardness, until a molded part (210), in particular a dental molded part (210) such as a dental restoration, is obtained.

2. 2. The method according to claim 1, characterized in that the mixed compound (200) is present as a slurry and / or pasty substance and comprises a diluent (205), in particular water, the mixed compound (200) is allowed to harden and / or solidify by drying in the cavity (110) of the cold casting mould (100), and the liquid part and / or water of the mixed compound (200) is allowed to exit the cold casting mould (100) by means of the at least one opening (111, 112), in particular removed from the mixed compound (200).

3. The method described in claim 1 or 2, characterized in that the gas contained and / or trapped in the mixed compound (200) and discharged from the cavity (110) through the second opening (112) is trapped air (208) and the liquid is the diluent (205).

4. 4. The method according to claim 3, characterized in that at least one wall (121, 122) bounding the cavity (110) of the cold casting mold (100) is additionally constructed, in whole or in part, with a plurality of said second openings (112) penetrating said wall (121, 122), opening into and / or leading out of said cavity (110) for the evacuation of said gas, in particular said trapped air (208) and / or said liquid, in particular said diluent (205).

5. 5. The method according to claim 1, characterized in that the mixed compound (200) is hardened and / or solidified in the cavity (110) of the cold casting mould (100) under the action of heat, during which the cold casting mould (100) filled with the mixed compound (200) is placed in a drying cabinet, a climatic cabinet or a sintering furnace, setting a temperature in the range of 30° C. to 120° C. and / or an air humidity in the range of 1% to 50%.

6. 6. The method according to claim 1, characterized in that the digital data set, in particular based on a spatial model of the patient's oral cavity for the geometrical design of the cavity (110) of the cold casting mold (100), includes volumetric shrinkage due to sintering and / or hardening of the mixed compound (200).

7. 7. The method according to claim 1, characterized in that organic materials, in particular organic polymers and / or waxes and / or plastics, preferably having a melting or decomposition temperature in the temperature range of 40° C. to 300° C., are used as the starting material (150) for the additive construction of the cold casting mold (100), such that the cold casting mold (100) is plasticizable and / or thermally or thermochemically decomposable.

8. 8. The method according to claim 1, characterized in that the mixed compound (200) comprises a metal powder (209), in particular a CrCo powder, or a ceramic powder (209), in particular an aluminum oxide powder and / or a zirconium oxide powder, and / or a glass-ceramic powder, in particular a lithium disilicate powder, and a binder (206).

9. The method of claim 8, wherein the melting and / or decomposition temperature of the cold casting mold (100) is below the melting or decomposition temperature of the binder (206).

10. 10. The method according to claim 1, characterized in that the mixed compound (200) is hardened to green hardness in the cavity (110) of the cold casting mold (100) before decomposition of the cold casting mold (100) begins or is completed.

11. 11. The method according to claim 1, characterized in that before the mixed compound (200) is sintered to the final hardness, the decomposition of the cold casting mold (100) is initiated or completely carried out by the action of heat at a temperature in the range of 200°C to 650°C.

12. 9. The method according to claim 8, characterized in that the melting point and / or decomposition temperature of the cold casting mould (100) is below the sintering temperature of the mixed compound (200), in particular the metal powder (209) or the ceramic powder (209).

13. 13. The method according to claim 1, characterized in that the thermal and / or thermochemical decomposition of the cold casting mold (100) is carried out in a sintering furnace, in which the cold casting mold (100) is placed together with the mixed compound (200) therein.

14. 14. The method according to claim 1, wherein the decomposition of the cold casting mold (100) is carried out thermally, in particular pyrolytically, under oxygen-free conditions or thermochemically, in particular by combustion, under oxygen supply.

15. 15. The method according to claim 1, characterized in that the cold casting mold (100), in particular the walls (121, 122) bounding the cavity (110) of the cold casting mold (100), are coated with a coating agent (220) before filling with the mixed compound (200), in order to avoid frictional and / or material bonds between the cold casting mold (100) and the mixed compound (200).

Images