Method for producing large polymerized dental material blocks

Abstract

A method for producing a three-dimensional dental material block from a dental, polymerizable material, wherein the material block is suitable for the production of dental prosthetic parts in a material-absorbing process, comprising the steps: a) optionally: adjusting the viscosity; b) transferring the polymerizable dental material into a radiolucent three-dimensional casting or pressing mold; c) planarizing at least one surface of the dental material in the three-dimensional casting or pressing mold to form a defined three-dimensional geometry of the material, wherein the planarizing is carried out by applying a transparent film or a planar transparent disc to the material to be polymerized in a three-dimensional casting or pressing mold open on one side, and subsequently applying pressure to the film or disc with a punch to planarize the surface.and / or d) Applying pressure to the polymerizable material in the three-dimensional casting or pressing mold by subjecting the polymerizable material to a pressure of 1.5 to 5 bar, e) Irradiating the polymerizable dental material substantially from all sides with light in the UV / Vis range, forming polymerized outer surfaces of the dental material in the form of a solid outer shell of the dental material, wherein the shell is in the defined three-dimensional geometry of the material, while the inner area of ​​the material is not polymerized or is partially polymerized, f) Optionally, removing the dental material with a dimensionally stable shell having a defined three-dimensional geometry from the casting or pressing mold, g) Heating the material with a solid shell having a defined three-dimensional geometry to 60 °C to 150 °C for at least 90 minutes, h) Optionally: Cooling the fully polymerized material,i) Obtaining a dental, polymerized material block with a defined three-dimensional geometry.

Description

The subject of the invention is a method for stress-free polymerization of larger three-dimensional dental material blocks according to claim 1, suitable for the production of dental prosthetic parts in a material removing process and obtaining a material block which is substantially free of voids and is obtained substantially while maintaining the three-dimensional geometry set before the polymerization, in particular the substantially complete polymerization.Small material blocks with a base area of 1 cm 2 and approximately a length of 3 to 4 cm are known from the prior art, which are hardened for a few seconds on the two longitudinal sides. Alternatively, photo-curing in a water bath over a longer period of time is disclosed.When producing composite milling disks from highly filled composites such as, for example, Charisma, Venus Diamond, Signum Cerami or Venus Pearl, which are light-hardening, it is to be expected that cracks and cracks often occur in the case of pure hot hardening due to stresses in the material, in particular when blocks of a certain size are produced. Light curing is not considered because of the large layer thickness of the milling blank and the insufficient curing depth of the light-curing composite.It is an object of the invention to develop a method which allows the production of dental material blocks or material plates of a certain dimension, which can be divided or cut into a multiplicity of small material blocks from which dental prostheses or parts thereof can be produced by means of a material-removing method. Likewise, a method should be developed with which substantially stress-free dental material blocks can be produced which are preferably free of stress-induced defects such as cracks. Furthermore, a method for producing composite dental prosthetic milling blanks, in particular with a filler content of 50 to 95 wt %, should be developed, in which stress-induced defects such as voids, cracks and cracks do not occur in the milling block during the production process.WO2011 / 041182A1 relates to the production of multilayer dental articles in different casting moulds. DE699 22 413 T2 relates to milling blanks in which detected cracks and discontinuities are less than 1 mm and to a method for producing these. DE 601 30 139 T2 relates to a method in which filling material reacts with a second mould component and a chemical bond is produced and to a milling blank arrangement with holder. US 2013 / 0049241 A1 discloses a dental shaped part and its production.The objects have been achieved by a method according to claim 1 and by the dental material blocks obtainable by the method according to claim 9 and by the use of a casting or press mould in this method according to claim 10 and by the use of the dental material blocks according to claim 11.The objects have been achieved according to the invention by placing a polymerizable dental material, such as preferably a dental composite, in a casting or compression mold that is transparent at the wavelength of the photoinitiator / photoinitiators and curing it there in a combined process of specific light-induced polymerization and a defined thermal polymerization according to claim 1. It is advantageous if the dental material, such as a composite, is heated to a temperature at which the viscosity of the material is significantly reduced before it is introduced into the casting or compression mold. As a result of this measure, the dental material can flow better into the casting or press mold and can fill the mold more completely. The temperature chosen must be below the temperature at which thermally induced polymerization starts. Therefore, the temperature to adjust the viscosity is selectable depending on the thermal polymerization initiator used. When dibenzoyl peroxide is used, for example, the dental material can be used at a maximum of about 60-65° C. over a period of max. 2 hours.After flowing into the transparent three-dimensional casting or press mold, in particular into the hollow mold of the casting or press mold, the surface is planarized or smoothed by careful pressing of the surface with a planar punch, so that the material acquires a defined three-dimensional geometry. Subsequently, the polymerizable material can be irradiated in the transparent casting or press mold for 6 min from all sides with a suitable light source, such as a laboratory light lamp, preferably in a light furnace, such as an egg plant light furnace. The material is surface-polymerized or partially cured by irradiation with UV / Vis light. The light curing corresponds to a pre-curing process in which an outer polymerized closed shell is formed in the dental material. The polymerized, cured shell of the dental material has a thickness of polymerized material of about 3 to 5 mm. However, the core of the dental material is still soft. Subsequently, the dental material with closed outer shell is preferably removed from the mold. In a next step, the dental material, in particular the composite material, is thermally polymerized for about 8 hours in an oven, such as a drying cabinet, at about 90° C., in order to complete the thermal curing and thus the through curing of the milling block. The available material block is preferably fully polymerized.The invention relates to a method for producing a three-dimensional dental material block, in particular a dental composite block, from a dental, polymerizable material, and a material block obtainable by the method, wherein the material block is suitable for producing dental prosthetic parts in a material-removing method, and the method comprises the steps of a) optionally: adjusting the viscosity, in particular in order to obtain a flowable material, b) transferring the polymerizable dental material into a radiation-transmissive three-dimensional casting or press mold, in particular with a hollow shape, in particular into a PMMA or polycarbonate casting or press mold, preferably with a wall thickness of at least 5 mm to 30 mm, preferably of 5 to 10 mm wall thickness, and preferably with formation of a defined three-dimensional geometry of the material, c) Planarization of at least one surface of the dental material in the three-dimensional casting or press mold, in particular in a one-sidedly open mold, forming a defined three-dimensional geometry of the material, wherein the planarization takes place by applying a transparent film or a planar transparent disk to the material to be polymerized in a one-sidedly open three-dimensional casting or press mold, and the film or the disk is subsequently impinged on by a stamp under pressure for planarization of the surface, and / or d) application of pressure to the polymerizable material in the three-dimensional casting or press mold, in particular the material is impinged on by a gas or gas mixture at a pressure of 1.5 to 5 bar, e) irradiation of the polymerizable dental material from all sides with light in the UV / visible range, In particular, the material is irradiated simultaneously from all sides with light, forming polymerized outer surfaces of the dental material in the form of a solid outer shell of the dental material, wherein the shell is present in the defined three-dimensional geometry of the material, in particular step b) or c), while the inner region of the material is not polymerized and / or partially polymerized, f) optionally removing the dental material with a dimensionally stable shell with defined three-dimensional geometry from the casting or press mold, g) heating the material with a solid shell and defined three-dimensional geometry to 60° C. to 150° C. for at least 90 minutes, in particular at 70 to 95° C. for 6 to 10 hours, h) optionally cooling the fully polymerized material, i) obtaining a dental, polymerized block of material with defined three-dimensional geometry. The polymerized block of material is preferably fully polymerized.In step b), the polymerizable dental material is preferably transferred into a radiation-transmissive three-dimensional casting or press mold, wherein the casting or press mold preferably has at least one first edge length or a diameter of greater than or equal to 90 mm and at least one second and / or third edge length of greater than or equal to 20 mm of the mold for producing the material block, molds of at least 148 x 210 mm, preferably of at least 210 x 297 mm and for producing a material thickness / height of at least 20 mm, preferably 30 mm, 90 to 200 mm being preferred.In step e), the light source and / or the casting or press mould can rotate in order to enable uniform irradiation from all sides of the mould. The irradiation in step e) can preferably be carried out without separate cooling in a medium such as water. Irradiation is preferably carried out simultaneously from all sides for at least 5 minutes to 60 minutes, and irradiation is preferably carried out simultaneously from all sides for 5 to 15 minutes. The pretreatment according to the invention makes it possible to expose the radiation to cracks without simultaneous cooling. The shell obtained in step e) generally has a wall thickness of 3 to 5 mm, so that after the irradiation in step e) the shell is present in the defined three-dimensional geometry of the material, while the inner region of the material is not polymerized or partially polymerized. In step e), a dimensionally stable dental material with a shell in a defined three-dimensional geometry is preferably obtained.The material blocks according to the invention should be readily cuttable on the one hand and also be suitable for producing dental prosthetic parts in a material-removing method, such as a milling method and / or grinding, drilling, a material removal by means of laser energy, such as laser milling, by means of chipping off the material, and / or CAD / CAM milling and / or a method comprising various material-removing method steps. It is particularly preferred if the material-removing methods are CAD / CAM methods in which the material-removing machining is carried out automatically.In order to convert the material blocks into an optimum geometry before the polymerization, it has proven advantageous to planarize polymerizable material transferred into the casting or compression mold open on one side on the open, in particular upper side. Therefore, preferably in step c), the planarization takes place by applying a film or a planar pane, both of which are preferably transparent, to the material to be polymerized in the three-dimensional casting or press mold open on one side. The film or the disk is then acted upon by a die under pressure for planarization of the surface. The die with which the planarization is carried out is preferably pressed onto the material at a pressure of at least 1 bar, preferably under a pressure of 1.2 to 5 bar, more preferably the planarization is carried out by means of a die at a pressure of 2 to 5 bar. For this purpose, the punch preferably has a geometry with a planar underside adapted to the casting or press mold.To homogenize the dental polymerizable material prior to the light-induced polymerization, the material is pressurized with a gas or gas mixture. Accordingly, it is preferred if, in step d), the polymerizable material is subjected to a pressure, in particular of a gas or gas mixture, of 1.5 to 5 bar in the three-dimensional casting or press mold; preference is given to a pressure of 2 to 5 bar, particularly preferably of 2 to 3 bar. The polymerizable material is treated with a gas or gas mixture under elevated pressure to minimize or eliminate gaseous microinclusions present in the material, e.g., from air or gas. Preferred gases or gas mixtures for treating the material under pressure include air, helium and argon, with air being particularly preferred.According to a particularly preferred embodiment of the invention, the irradiation of the polymerizable dental material takes place substantially from all sides with light in the UV / Vis range in the range of approximately 380 nm-500 nm, preferably as dual irradiation in the UV and Vis range, preferably the irradiation takes place simultaneously from all sides of the three-dimensional geometry, for a period of greater than or equal to 4 minutes to 4 hours, in particular greater than or equal to 5 minutes, preferably 5.5 minutes to 15 minutes.The invention likewise relates to a method in which the irradiation of the polymerizable dental material takes place as dual irradiation and the at least two intensity maxima of the light of the radiation source(s) lie in the UV and in the Vis range, in particular irradiation takes place with intensity maxima of the radiation source(s) of 350 nm to 390 nm and of 420 nm to 500 nm, particularly preferably with intensity maxima around 380 nm and 450 nm, preferably + / - 20 nm. In order to obtain a particularly good and uniform polymerization of the outer shell of the invention, dual irradiation is particularly suitable. It is further particularly preferred here if the irradiation takes place in a light furnace, in particular in an internally mirrored light furnace, particularly preferably in a light furnace in the two to 20 radiation sources, preferably 4 to 15 radiation sources, with at least two intensity maxima of the radiation source(s) of 350 nm to 390 nm and of 420 nm to 500 nm, particularly preferably with intensity maxima around 380 nm and 450 nm. Particularly suitable radiation sources in an internally mirrored light furnace are: 2-20 radiation sources each having 9 W (450 nm) and 2-20 radiation sources each having 9 W (380 nm).The irradiation in step e) forms a preferably outer, closed shell of the polymerized material in the three-dimensional geometry of the dental material. The dental material with a shell is preferably dimensionally stable and has a defined three-dimensional geometry which corresponds approximately to the casting or press mould. The sleeve preferably has a thickness of greater than or equal to 2 to 15 mm, the sleeve preferably has a thickness of polymerized material of greater than or equal to 2 to 10 mm, particularly preferably of 3 to 6 mm, further preferably of 3 to 4 mm.In a method step, for example f), the dental material with a dimensionally stable shell and with a defined three-dimensional geometry is preferably removed from the casting or press mould. According to an alternative, the subsequent thermal treatment can also take place in the casting or press mould.In a method step, for example j), the dental, polymerized material block obtained in i) having a defined three-dimensional geometry is divided into greater than or equal to 50 milling blocks, each having at least one edge length of greater than or equal to 10 mm, in particular to less than or equal to 25 mm, preferably to less than or equal to 20 mm. Preferably, two to three edge lengths of the cuboid milling blocks are greater than or equal to 10 mm. The dividing can be effected by cutting, laser cutting, sawing or other measures known to the person skilled in the art. It is particularly preferred here if the material block is divided into greater than or equal to 90 milling blocks, preferably greater than or equal to 160 milling blocks, each having at least one edge length of greater than or equal to 10 mm, and in particular less than or equal to 20 mm, preferably less than or equal to 25 mm. The milling blocks are preferably in the form of cuboids. Preferably, all edge lengths of the cuboids are greater than or equal to 10 mm, in particular greater than or equal to 12 mm, and less than or equal to 25 mm. Milling blocks in the form of cuboids with an area of 14 x 14 mm, or of 15 x 15 mm and a height of 17 to 18 mm can thus be produced.In process step g), the solid shell material of step e) having a defined three-dimensional geometry is heated to 60° C. to 150° C. for at least 90 minutes. The thermal polymerization is preferably carried out in the temperature range from 70° C. to 100° C., preferably from 70 to 95° C., particularly preferably from 80° C. to 95° C., further preferably from 85 to 95° C., preferably around 90° C.+ / - 2.5° C. The thermal polymerization is carried out in the aforementioned temperature range for greater than or equal to 2 hours, preferably from 2 to 12 hours. More specifically, to 70°C to 95°C for 2 to 12 hours. In order to produce particularly stress-free material blocks, in particular material blocks having an edge length of greater than or equal to 90 mm and at least one second edge length of greater than or equal to 20 mm, a thermal treatment of 80 to 95° C. has proven to be carried out for 5 to 12 hours, in particular for 7 to 9 hours, preferably for 8 hours at 90° C.+ / - 2.5° C. According to a particularly preferred alternative, the dental material is heated in step g) to 70° C. to 95° C. for 2 to 12 hours, in particular the dental material is heated in step g) in an oven. Following the thermal polymerization step, in step h) the material can cool in the furnace for a defined time. For the production of particularly stress-free material blocks, it is preferred if the cooling takes place in the furnace which is switched off after step g has been carried out). Preferably, the furnace is turned off and the material is allowed to cool slowly in the furnace.The optional adjustment of the viscosity before transferring the dental polymerizable material into the casting or press mold can be effected by heating the material to 60 to 65° C. In any case, however, the temperature for adjusting the viscosity should be below the temperature at which the thermally induced polymerization is started. Preferably, the temperature is at least 10° C. below the temperature at which the thermally induced polymerization starts. The dental material can preferably have the following viscosity or be adjusted to a following viscosity with η of 1 • 10 5 Pa • s to 5.0 • 10 8 Pa • s, a viscosity of η of 5 • 10 5 Pa • s to 2.0 • 10 8 Pa • s, particularly preferably of η of 8 • 10 5 Pa • s to 2.0 • 10 8 Pa • s. The storage modulus of the polymerizable material can be between G*=2 • 10 3 to 10 • 10 5 in this case.To produce the material blocks according to the invention, casting or compression molds, in particular with a hollow mold, made of PMMA (polymethyl methacrylate) or polycarbonate (PC), are preferably used. For this purpose, the molds can be cylindrical PMMA moulds or press moulds open on one side at the top, in particular with a hollow mold, with a PMMA base, for example in the form of cylindrical shells made of PMMA. Likewise, the shapes may have rectangular or square dimensions in plan view. Suitable examples are, for example. Casting or press moulding having at least one hollow mould which is in the form of a cuboid in which two surfaces are greater than or equal to DIN A5, in particular greater than or equal to DIN A4, and the remaining edge length is at least 20 mm, preferably greater than or equal to 30 mm, greater than or equal to 40 mm, 50 mm, greater than or equal to 60 mm. It is likewise possible to produce cuboids in which at least four surfaces are greater than or equal to DIN A5, in particular greater than or equal to DIN A4. Likewise suitable geometries for the hollow mold in casting or compression molds are cylindrical, rod-shaped or cube-shaped geometries. Alternatively, the casting or compression mold may be made of another transparent material such as polycarbonate.The hollow shape can preferably correspond to the three-dimensional defined geometry of the shell with defined three-dimensional geometry of the material, preferably to the geometry of the dental, polymerized material block with defined three-dimensional geometry. It is particularly preferred if the material block with a defined three-dimensional geometry has a volume shrinkage of less than or equal to 1-3 vol % with respect to at least one edge length of the hollow shape.The method is particularly preferably carried out with casting or compression molds with a transparency of greater than 95%, in particular made of PMMA or polycarbonate or also glass, such as quartz glass or commercially available glass. According to a particularly preferred alternative, the method according to the invention is carried out with casting or compression moulds, the material of which has a refractive index of 1.3 to 1.8, in particular of 1.48 to 1.50.The wall thickness of the casting or compression molds used in the method should preferably be in the range from 5 to 30 mm, preferably from 5 to 10 mm. The irradiation is preferably carried out directly in the PMMA or polycarbonate casting or press mould, in particular without the use of a water bath, without water cooling of the casting or press mould or of another cooling medium surrounding the casting or press mould.According to the method according to the invention, material blocks with a defined three-dimensional geometry can be produced or are obtainable which substantially do not have gaseous micro inclusions or voids which are greater than 0.05 mm, the voids or gaseous micro inclusions preferably being less than or equal to 100 μm, particularly preferably less than or equal to 50 μm, further preferably less than or equal to 20 μm.The polymerized material blocks with a defined three-dimensional geometry produced or obtainable by the process according to the invention preferably have at least one first edge length or a diameter of greater than or equal to 90 mm and preferably have at least one second edge length of greater than or equal to 20 mm, in particular greater than or equal to 90 mm to 200 mm. In particular, cuboids can be obtained in which two surfaces are greater than or equal to DIN A 5 (21 cm x 14.8 cm) or greater than or equal to DIN A4 (21 cm x 29.7 cm) and the remaining edge lengths are greater than or equal to 20 mm, preferably greater than 30 mm, preferably greater than 40 to 60 mm.In the method according to the invention, a composite material which comprises(i) from 50 to 95% by weight of inorganic fillers which comprise a) silicon dioxide, preferably silica; zirconium dioxide and / or mixtures comprising at least the two abovementioned oxides, and b) dental glasses whose average particle sizes are in the range from 0.2 to 10 μm,(ii) from 5 to 50% by weight of monomer mixture,(iii) 0 to 2% by weight of initiators comprising photoinitiators, at least one thermally activatable free-radical initiator, such as peroxides,(iv) 0 to 2 wt.% of stabilizers, additives, wherein the total composition is 100 wt.%.According to a preferred alternative, the dental glasses can be present with at least two different fractions of mean particle sizes in the range of 0.2 to 10 μm.The invention likewise relates to a dental material block which does not have any voids, cracks or cavities which have an extent of greater than or equal to 0.05 mm in one dimension; they are preferably less than or equal to 100 μm, particularly preferably less than or equal to 50 μm, further preferably less than or equal to 20 μm. The invention likewise relates to a material block which has at least one first edge length or a diameter of greater than or equal to 90 mm and has at least one second edge length of greater than or equal to 20 mm. Preferred are material blocks of 148 x 210 mm, preferably 210 x 297 mm and a material thickness / height of at least 20 mm, preferably 30 mm, 90 to 200 mm.The polymerized material block is further characterized in that it has substantially the same defined geometry as the polymerizable dental material in the casting or press mold, in particular in step c), d) and / or e), in particular in step c) or d). Thus, the polymerized block of material preferably has approximately the same geometry as the depression of the casting or press mold, wherein the height of the block of material on the side on which the planarization took place can vary.As a result of the long photo-curing according to the invention, preferably simultaneously from all sides for at least 4 minutes, the polymerizable dental material is provided with a solid outer dimensionally stable shell which is already present in the defined three-dimensional geometry of the material. Therefore, the dental material with the solid shell can be removed from the casting and / or press mould according to the invention and subsequently thermally treated in the furnace.Preferably, the polymerized material block has, in relation to the polymerizable dental material in the defined geometry in step c) or d), a shrinkage of less than 1-3% by volume with respect to the first edge length or a diameter of 90 mm. Likewise preferred is a shrinkage of less than or equal to 1-3 vol % with respect to the second edge length of greater than or equal to 20 mm.The invention likewise relates to the use of a polymerized material block having at least one edge length or a diameter of greater than or equal to 90 mm and at least one second edge length of greater than or equal to 20 mm for producing at least two smaller material blocks, in particular by the material block being divided at least once, preferably cut, sawn or divided by other measures known to the person skilled in the art. According to the method of the invention, DIN A5 or DIN A4 large plates with a thickness of 10 to 50 mm, preferably of 20 to 50 mm, can be produced, which can then be divided, for example, into milling blocks in the form of cuboids with a surface area of 14.times.14 mm, or 15.times.15 mm and a height of 17.times.18 mm. Thus, from a DIN A4 large plate, more than 200 smaller material blocks can be produced for use as a milling block, for example more than 200 smaller material blocks or milling blocks can be cut.The material blocks produced according to the invention or the material blocks produced from them can subsequently be processed in an abrasive process to form dental prosthetic parts or parts thereof; in particular, composite blocks can be produced and processed in a CAD / CAM process by milling, drilling and / or by means of a laser in an abrasive process, such as laser milling.Exemplary embodiments illustrate the invention in more detail without restricting the invention to these subject matters. FIG. 1 : A light-transmissive PMMA casting or press mould according to the invention. FIG. 2 : PMMA mold filled with polymerizable dental material. FIG. 3 : Planarization of the surface of the material FIG. 4 : All-round light curing with formation of the shell in the polymerizable material. FIG. 5 : Polymerized material block. FIG. 6 : bridge milled from the material block FIGS. 7a and 7b: Material blocks of the same material which were purely thermally cured, not according to the invention. FIG. 8 : Representation of a cut material block according to the invention with different magnifications of the cut surface.FIG. 1 shows a PMMA casting or press mould according to the invention, which is open at one end at the top in order to allow the polymerizable dental material to flow in or to be introduced as a kneadable paste. In FIG. 2, the PMMA mold is shown filled with a polymerizable dental material. In FIG. 3, the dental material in the PMMA mold is planarized on the upper side with a stamp by pressing the stamp onto the surface of the polymerizable material with a defined pressure. Preferably, a transparent film or a transparent planar pane, preferably made of PMMA, is located between the die and the surface of the polymerizable material. Subsequently, a gas or gas mixture is applied to the material in a pressure vessel in order to remove gaseous micro inclusions. The overall light curing is shown in FIG. 4. After light curing, the thermal polymerization according to the invention is carried out at 90° C. for 8 hours. The resulting polymerized block of material is shown in Figure 5 and Figure 6.FIGS. 7 aand 7 b : Material blocks, not according to the invention, of the same material which was cured by annealing the material at 90° C. for 8 h. The cured material has large cracks or voids of a size above 0.5 cm. Overall, it also arises that the polymerized material blocks do not have the original defined geometry after the tempering, but are rather greatly distorted in themselves. In the plan view, it can be easily seen that the material blocks no longer have the originally circular geometry.FIG. 8 shows a cut material block and various cut-outs 1, 2, 3, 4 and 5 at 200x magnification and a larger cut-out at 5x and 20x magnification. Figures 1 to 5 show the scale for 200 micrometers. The enlargements show that the material block cured by the method according to the invention, despite its large dimension of over 90 mm width, does not exhibit any distortions or gaseous inclusions or voids, while the purely thermally cured blocks of the same dimensions are distorted and have large cracks and voids.Example:According to the invention, the object is achieved in that the composite is placed in a form which is transparent at the wavelength of the photoinitiator. Advantageously, the composite is previously heated to a temperature at which the viscosity of the material is significantly reduced in order to allow better flow into the mold. However, the temperature must not yet be so high that the thermally induced polymerization starts. This is dependent on the thermal polymerization initiator used. When dibenzoyl peroxide, for example, is used, maximum temperatures of about 60-65° C. have been found for a period of max. 2 hours have been found to be suitable.After flowing into the transparent mold and planarizing the surface by careful pressing, the material in the mold is irradiated on all sides in a suitable laboratory light lamp, such as, for example, an egg-plant light furnace, for 6 minutes and surface-hardened. After this pre-hardening process, the material is coated with a hardened "skin" of about 5 mm, but the core is still soft. The dimensionally stable photocured composite material is removed from the PMMA mold and then placed in a drying cabinet at about 90° C. for about 8 hours in order to complete the thermal curing and thus the through curing of the milling block.UV / Vis: 380 nm to 500 nm for 6 minutes, at 23° C. RT; 5 tubes Osram dulux S-Blue 71 blue 9W (450 nm) and 5 tubes Osram dulux S-Blue 78 blue 9W (380 nm), in particular in an internally mirrored light furnace; thermal polymerization: in the preheated furnace at 90° C. for 8 hours. Cooling was done in the oven which was turned off. Comparison of Material Parameters Comparison of Material ParametersCharismaCharisma + peroxideFlexural strength [MPa]144145Modulus of Elasticity [MPa]954311747Curing: Curing8 Palatray CU on both sides.6 min. Ambient light oven and drying cabinet 90° C. for 8 hThe respective test specimen sizes conform to the specifications of DIN 4049. The flexural strength [MPa] and the modulus of elasticity [MPa] were determined in accordance with DIN 4049.

Claims

A method for producing a three-dimensional dental material block from a dental, polymerizable material, wherein the material block is suitable for producing dental prosthetic parts in a material removing method, comprising the steps of a) optionally: adjusting the viscosity, b) transferring the polymerizable dental material into a radiation-transmissive three-dimensional casting or press mold, c) planarizing at least one surface of the dental material in the three-dimensional casting or press mold to form a defined three-dimensional geometry of the material, wherein the planarizing is carried out by applying a transparent film or a planar transparent pane to the material to be polymerized in a three-dimensional casting or press mold open on one side, and the film or the pane is subsequently acted on with a stamp under pressure to planarize the surface, and / or d) applying pressure to the polymerizable material in the three-dimensional casting or press mold by applying a pressure of 1.5 to 5 bar to the polymerizable material, e) irradiating the polymerizable dental material with light in the UV / Vis range substantially from all sides, forming polymerized outer surfaces of the dental material in the form of a solid outer shell of the dental material, wherein the shell is present in the defined three-dimensional geometry of the material, while the inner region of the material is not polymerized or partially polymerized, f) optionally removing the dental material with a dimensionally stable shell with a defined three-dimensional geometry from the casting or press mold, g) heating the material with a solid shell which is present in a defined three-dimensional geometry, Optionally, cooling to 60° C. to 150° C. for at least 90 minutes, h): cooling of the fully polymerized material, i) obtaining a dental, polymerized material block with defined three-dimensional geometry.Method according to claim 1, characterised in that I) the irradiation of the polymerisable dental material takes place substantially from all sides with light in the UV / Vis range for a period of time greater than or equal to 4 minutes to 4 hours, in particular greater than or equal to 5 minutes, and / or II) the shell in step e) has a thickness of greater than or equal to 2 to 15 mm, preferably of greater than or equal to 2 to 10 mm, particularly preferably of 3 to 6 mm, further preferably of 3 to 4 mm.Method according to claim 1 or 2, characterised in that the irradiation of the polymerisable dental material takes place as dual irradiation with intensity maxima of the light of the radiation source in the UV and in the Vis range, in particular irradiation takes place with intensity maxima of the radiation source of 350 nm to 390 nm and of 420 to 500 nm, preferably with intensity maxima around 380 nm and 450 nm.Method according to one of Claims 1 to 3, characterized in that the polymerizable dental material is transferred into a radiation-transmissive, three-dimensional casting or press mould having a hollow shape, the hollow shape having the shape of a cuboid in which two surfaces are greater than or equal to DIN A5 (21 cm x 14.8 cm), in particular greater than or equal to DIN A4 (21 cm x 29.7 cm), and the remaining edge lengths are at least 20 mm.Method according to any one of claims 1 to 4, characterised in that in step g) the solid shell material, which is in a defined three-dimensional geometry, is heated to 70 °C for at least 90 minutes.Method according to one of Claims 1 to 3, characterized in that the polymerized material block having a defined three-dimensional geometry a) has at least one first edge length or a diameter of greater than or equal to 90 mm and at least one second edge length of greater than or equal to 20 mm, or b) is in the form of a cuboid in which two surfaces are greater than or equal to DIN A5, in particular greater than or equal to DIN A4, and the remaining edge length is at least 20 mm.Method according to one of Claims 1 to 6, characterized in that the three-dimensional casting or moulding die is made of polymethyl methacrylate.Method according to one of Claims 1 to 7, characterized in that the dental, polymerized material block obtained with a defined three-dimensional geometry is divided into greater than or equal to 50 milling blocks which have at least one edge length of greater than or equal to 10 mm.Dental material block obtainable by a method according to any one of claims 1 to 7, wherein the material block does not have any voids, cracks or cavities which have an extent in one dimension of greater than or equal to 0.05 mm, wherein the material block has at least one first edge length or a diameter of greater than or equal to 90 mm and at least one second edge length of greater than or equal to 20 mm.Use of a three-dimensional casting or compression mould in a method according to one of Claims 1 to 8 in the form of a hollow mould made of polymethyl methacrylate or polycarbonate for producing a dental material block cured by means of radiation, in particular by means of UV / Vis radiation, and at elevated temperature.Use of a polymerized material block obtainable according to any of Claims 1 to 7 or according to Claim 8, which has at least one edge length or a diameter of greater than or equal to 90 mm and at least one second edge length of greater than or equal to 20 mm for producing at least two smaller material blocks, in particular by the material block being divided at least once.

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