METHOD FOR DETERMINING AN INTERNAL STRUCTURE OF A REPLACEMENT TOOTH, METHOD FOR MANUFACTURING A REPLACEMENT TOOTH, REPLACEMENT TOOTH, DEVICE FOR DATA PROCESSING, COMPUTER PROGRAM AND COMPUTER-READY MEDIUM

Description

[0001] The invention relates to a method for determining the internal structure of a replacement tooth.

[0002] Furthermore, the invention relates to a method for manufacturing a replacement tooth with a predetermined outer shell.

[0003] Furthermore, the invention relates to a replacement tooth, a data processing device, a computer program and a computer-readable medium.

[0004] In the field of tooth replacement, or more generally, in the field of dental prosthetics, it is common practice to manufacture replacement teeth, or comprehensive partial or complete dentures, from prefabricated plastic teeth. Prefabricated teeth with varying geometries, optical properties, and mechanical characteristics are available on the market. To achieve the most faithful reproduction possible, the prefabricated tooth that most closely resembles the tooth being replaced must be selected. The selected prefabricated tooth can then be further customized to the patient's specific needs. This is done manually.

[0005] It is also well-established to use digital manufacturing technologies to produce replacement teeth or, more generally, dental prostheses. For this purpose, so-called CAD / CAM systems are used. The replacement tooth, or a partial or complete denture encompassing the replacement tooth, is first created, i.e., designed, in the digital realm. This can be achieved using so-called tooth libraries, which provide outer shell data describing the outer surface of a multitude of different replacement teeth. The outer shell of the replacement tooth, partial, or complete denture can then be virtually and three-dimensionally adapted to the patient's specific situation. This is done using CAD software, i.e., in the digital realm. Such replacement teeth, partial dentures, or complete dentures can be manufactured using subtractive manufacturing processes, such as milling or grinding, or additive manufacturing processes, such as 3D printing.

[0006] In WO 2021 / 122013 A1, a method for defining at least one interface inside an artificial tooth element is shown.

[0007] The WO 2004 / 037112 A1 describes a dental prosthesis and a method for its manufacture.

[0008] The object of the present invention is to further improve the fidelity of replacement teeth, i.e., to achieve a natural-looking appearance of the replacement teeth. In other words, a way is to be created to produce replacement teeth that come as close as possible to natural teeth.

[0009] According to a first aspect of the invention, a method for determining the internal structure of a replacement tooth is provided. The method comprises: Obtain from outer shell data describing an outer shell of the replacement tooth, define or obtain a first reference geometry information describing a first reference geometry that virtually divides the outer shell of the replacement tooth into a first shell section and a second shell section, create a first compression shell by virtually compressing the first shell section in a direction to the first reference geometry by a first compression measure, where the first reference geometry represents a compression basis, and derive at least one subvolume of the replacement tooth as a volume bounded by the first compression shell.

[0010] The inventive method is based on the observation that the fidelity of replacement teeth depends not only on an outer shell that is as true to life as possible, but also on the internal structure of the replacement tooth. Similar to a natural tooth, whose internal structure can essentially be subdivided into a root, a dentin core, and an incisal edge, the natural appearance of a replacement tooth also depends on the interplay of various sections or layers that exhibit different optical properties, in particular different translucencies. The entirety of these different sections or layers constitutes the internal structure of the replacement tooth. The inventive method takes this insight into account, enabling the determination of an internal structure for the replacement tooth that results in an extremely natural appearance.At the same time, the method according to the invention is comparatively simple and can be easily implemented, in particular, within CAD or CAM software. The method steps constitute a set of rules that can be implemented automatically within the CAD or CAM software. The input data used is outer shell data, which, as already mentioned, can originate from a known tooth library and / or can be adapted or modeled within dental CAD or CAM software. Furthermore, reference geometry information and a first compression dimension are required as input data. In this context, the reference geometry information can optionally be derived from the outer shell data. The compression dimension can be specified absolutely, e.g., in mm, or relatively, e.g., as a percentage.The reference dimension can be a dimension of the outer shell or a dimension of a so-called bounding box of the replacement tooth, i.e., a cuboid that encloses the replacement tooth. During upsetting, the distance of each point of the geometry to be upset from the reference geometry, measured along an upsetting direction, is reduced by a factor defining the upsetting. In other words, each of these distances is multiplied by an upsetting factor less than one. This results in the smoothing of peaks and depressions during upsetting, which distinguishes upsetting from parallel translation or proportional scaling of the outer shell. In a simple numerical example, a peak of the geometry to be upset lies 10 mm above an upsetting base, a midsection of the geometry to be upset lies 5 mm above the upsetting base, and a depression of the geometry to be upset lies 3 mm above the upsetting base.A compression with a compression factor of 0.8 thus results in the apex being located at 8 mm, the middle section at 4 mm, and the depression at 2.4 mm in the compressed geometry. In the context of the inventive method, a compression base is understood as a fixed geometry against which the compression takes place. The compression of the first shell section to create a compression shell, from which a subvolume of the replacement tooth can be derived, has the particular advantage that subvolumes, e.g., in the form of layers, can be created that exhibit a thickness gradient. In other words, a subvolume created in this way, e.g., in the form of a layer, can have a variable thickness. The thickness can be influenced by selecting the compression factor. The fact that the compression is performed virtually means that the first shell section of the outer shell described by the outer shell data is compressed in digital space.Therefore, no physical compression of a physical object takes place. By compressing the first segment of the outer shell, which describes a three-dimensional geometry of the replacement tooth, a further three-dimensional geometry is generated, referred to here as the compression shell. The compression base or reference geometry subdivides the outer shell into two outer shell segments. The compression base or reference geometry is chosen such that, due to the compression in the direction of the reference geometry, the compression shell lies inside the outer shell described by the outer shell data. In this way, various subvolumes of the replacement tooth can be defined by the compression shell and the segments of the outer shell. As will be explained below, such a generated subvolume can serve to replicate a tooth incisal edge or a dentin core.In particular, one subvolume may be limited by the first outer shell section and the first compression shell. Another subvolume may be limited by the second outer shell section and the first compression shell. The subvolumes form an internal structure of the replacement tooth, giving it a natural appearance.

[0011] In one example, the first compression dimension is chosen such that a maximum distance of 0.5 mm to 10 mm is achieved along the compression direction between the first shell section and the first compression shell. Preferably, this distance is 0.5 mm to 2.5 mm. In another variant, this distance is 3.5 mm to 6 mm, e.g., 5 mm.

[0012] The method according to the invention is carried out in particular automatically, semi-automatically and / or computer-aided. This means that the internal structure can be determined essentially without human intervention. In this context, the method steps constitute a set of rules that are executed by computer.

[0013] The inventive method for determining the internal structure of a replacement tooth can therefore be a computer-implemented method.

[0014] It is understood that in connection with the method according to the invention, terms such as "first" and "second" serve only for the simplest explanation and do not imply any quantities or numbers.

[0015] Although the inventive method has been explained for a replacement tooth, it is understood that the inventive method can also be used for partial or complete dentures that include such replacement teeth.

[0016] According to one embodiment, the method further comprises: creating a second compression shell by virtually compressing the first shell section or the first compression shell in a direction to the first reference geometry by a second compression measure, wherein the first reference geometry represents a compression basis, and deriving at least one subvolume of the replacement tooth as a volume bounded by the second compression shell.

[0017] Two compressions are performed, using the same compression base. Optionally, a different compression measure is used. Alternatively or additionally, a different initial geometry is used to create the second compression shell than to create the first. In one example, the first shell segment is compressed to different degrees in the two compressions. In another example, the first compression shell, itself defined by a virtual compression, is compressed again. In this way, two compression shells can be determined very simply and efficiently. These each subdivide an outer shell defined by the outer shell data into subvolumes. For example, one subvolume is bounded by the second compression shell and the first shell segment. Another subvolume can be bounded by the second compression shell and the second shell segment.A further subvolume can be limited by the first compression layer and the second compression layer. Consequently, a finely structured internal structure of the replacement tooth can be determined simply and efficiently, with its subvolumes taking the form of layers, for example. Such an internal structure closely resembles that of a natural tooth.

[0018] It is understood that the method according to the invention is not limited to two compression operations with different compression dimensions but using the same reference geometry. Naturally, three, four, five, or even more compression operations can also be performed using the same reference geometry, each with different compression dimensions.

[0019] The procedure may also include: define or obtain a second reference geometry information that describes a second reference geometry which is different from the first reference geometry and which virtually divides the outer shell of the replacement tooth into a third shell section and a fourth shell section, create a third compression shell by virtually compressing the third shell section or the first compression shell or the second compression shell in a direction to the second reference geometry by a third compression measure, wherein the second reference geometry represents a compression basis, and derive at least one subvolume of the replacement tooth as a volume bounded by the third compression shell.

[0020] According to this example, the method comprises at least two virtual compressions, with a different reference geometry used as the compression basis for each of the at least two virtual compressions. Furthermore, this example covers three alternatives, each involving different initial geometries for the virtual compression. The initial geometries include the third shell segment, the first compression shell, and the second compression shell. In this way, at least two compression shells can be determined very simply and efficiently. These each subdivide an outer shell of the replacement tooth, defined by the outer shell data, into subvolumes. For example, one subvolume might be bounded by the third compression shell and the third shell segment. Another subvolume might be bounded by the third compression shell and the fourth shell segment.It is also conceivable that a subvolume is bounded by the third compression layer and the first compression layer. Likewise, it is possible that a subvolume is bounded by the third compression layer and the second compression layer, provided a second compression layer is present. Consequently, a finely structured internal structure of the replacement tooth can be determined simply and efficiently. The subvolumes can be formed as layers. Such an internal structure closely resembles that of a natural tooth.

[0021] It is understood that the method according to the invention is not limited to the use of two reference geometries as compression bases. Naturally, three, four, five or more reference geometries can also be used, and a corresponding number of compressions can be performed using these reference geometries.

[0022] It is understood that in embodiments of the inventive method for determining the internal structure of the replacement tooth, in which two or more subvolumes are derived, the derivation of subvolumes also includes the application of Boolean operations to the subvolumes. Thus, two or more subvolumes can be combined during the derivation of at least one subvolume. Alternatively or additionally, subvolumes can be sectioned, i.e., common sections of two or more subvolumes can be defined as a new subvolume. In this way, a particularly lifelike internal structure for the replacement tooth can be determined.

[0023] Preferably, the internal structure of the replacement tooth comprises two to five subvolumes. In particular, the internal structure comprises three subvolumes. Such an internal structure represents a good compromise between a simple internal structure, i.e., as few subvolumes as possible, and a high degree of fidelity to the original tooth, i.e., the most natural appearance possible.

[0024] In one variant, the procedure further includes assigning material information, color information, translucency information, and / or anatomical information to one or more of the subvolumes. This means that each subvolume can be assigned material information, color information, translucency information, and anatomical information. In this way, the internal structure of the replacement tooth is defined more precisely. Multiple subvolumes can also be assigned the same material information, color information, translucency information, and / or anatomical information. For example, the anatomical information "dentin core" is assigned to one or more subvolumes. This single subvolume or these multiple subvolumes thus replicate the dentin core within the replacement tooth.In this example, all subvolumes assigned the anatomical information "dentin core" can be assigned the same material information, color information, and translucency information. It can be taken into account that the dentin core within the replacement tooth is comparatively opaque and dark. In another example, the anatomical information "cervical margin" is assigned to one or more subvolumes. This one or more subvolumes thus replicate the cervical margin within the replacement tooth. In this example, all subvolumes assigned the anatomical information "cervical margin" can be assigned the same material information, color information, and translucency information. It can be taken into account that the cervical margin within the replacement tooth is comparatively opaque and dark.In another example, the anatomical information "incisal edge" or "tooth incisal edge" is assigned to one or more subvolumes. This single subvolume or these multiple subvolumes thus replicate the incisal edge within the replacement tooth. In this example, all subvolumes assigned the anatomical information "incisal edge" can be assigned the same material information, the same color information, and the same translucency information. It can be taken into account that the incisal edge within the replacement tooth is comparatively light and translucent. It goes without saying that the aforementioned examples can also be combined. Overall, the internal structure of the replacement tooth can be defined in detail in this way, so that the replacement tooth has a lifelike appearance.

[0025] According to one embodiment, at least one reference geometry is defined by an equator line of the outer shell of the replacement tooth. Alternatively, at least one reference geometry is defined by a plane that includes a center of mass and / or center of volume of the outer shell of the replacement tooth. A further alternative is at least one reference geometry defined by a plane that includes an extremum of the outer shell of the replacement tooth. In this context, an equator line is understood to be a line that runs along the largest circumference of the replacement tooth. The reference line for this is a tooth axis that passes through a center of mass or center of volume of the replacement tooth and is oriented along a tooth height direction, i.e., in a direction from the tooth root to the tooth crown.The creation of the equator line can be visualized as follows: a straight circular cylinder, whose central axis runs parallel to the tooth axis, is rolled along the outside of the tooth. The line along which the cylinder touches the tooth as it rolls is the equator line. Such an equator line is also referred to as the anatomical tooth equator. In contrast, a prosthetic tooth equator is determined with reference to the insertion direction of the prosthesis. The prosthetic tooth equator can therefore be determined in the same way as the anatomical tooth equator, but using the insertion direction instead of the tooth axis. Thus, the equator line is not necessarily straight in either case. Furthermore, an extreme point of the outer shell is understood to be, for example, the highest or lowest point of the outer shell of the replacement tooth.The equator, center of mass, center of volume, and / or an extreme point can be determined using the method according to the invention. Such reference geometries can be determined simply and reliably. At the same time, they allow for virtual compressions that lead to realistic internal structures.

[0026] The procedure can also include ignoring portions of at least one compression sheath that lie outside the outer sheath of the replacement tooth. Specifically, all portions of compression sheaths located outside the outer sheath of the replacement tooth are ignored. This can be achieved through simple Boolean operations. Thus, the outer sheath of the replacement tooth remains intact in all compressions.

[0027] The direction of compression can run along the vertical axis, the horizontal axis, or the vertical axis of the replacement tooth. In other words, the direction of compression coincides with the vertical axis, the horizontal axis, or the vertical axis. Alternatively, the direction of compression can be oriented parallel to the vertical axis, the horizontal axis, or the vertical axis.

[0028] For this purpose, a tooth-specific coordinate system can be used. The origin of this coordinate system lies at the center of volume of the outer shell of the replacement tooth. The orientation and position of the replacement tooth in the human jaw are considered to determine the direction of the X-axis. If several teeth are present in the jaw, the corresponding center of volume of the outer shell can be determined for each tooth. Connecting all the centers of volume of all teeth in the jaw results in a so-called dental arch. The shape of the dental arch resembles a parabola, with one vertex of the parabola located between the central incisors. In this context, the X-axis runs tangentially to the dental arch. It is understood that, strictly speaking, the dental arch is only defined if the position and orientation of the teeth adjacent to the tooth under consideration are also known.However, a specialist can also determine the relevant section of the dental arch based solely on the outer surface of the replacement tooth. The X-axis runs parallel to the width of the tooth. The Z-axis is perpendicular to the X-axis and oriented towards occlusion. This means that the Z-axis points towards the apex or away from the root. In other words, the Z-axis is parallel to the vertical dimension of the tooth. The Y-axis is perpendicular to both the X-axis and the Z-axis and points towards the tongue or palate. The Y-axis is therefore parallel to the depth of the tooth.

[0029] The procedure can also include: determining the tooth type of the replacement tooth based on the outer shell data, or obtaining tooth type information that describes a tooth type of the replacement tooth, and selecting the compression dimension and / or the reference geometry depending on the tooth type. For example, tooth type information can be obtained in the form of metadata from the outer shell data. Alternatively or additionally, a tooth type can be determined based on the size of a bounding box around the relevant tooth. This can take into account both absolute dimensions of the bounding box in different dimensions and ratios of the dimensions of the bounding box in different dimensions. Thus, absolute values ​​of the dimensions of the bounding box along the X-axis, Y-axis, and Z-axis of a tooth-specific coordinate system, and their ratios to each other, can be considered.The edges of the bounding box are oriented along the axes of the tooth-specific coordinate system. Similarly, the position of the replacement tooth on a dental arch can provide a reference point for a tooth type. Examples of tooth types are incisors, canines, and molars. The molars are also referred to as back teeth. Incisors and canines can also be combined into a single tooth type for the inventive method. Incisors and canines are often collectively referred to as anterior teeth. If the compression dimension and / or the reference geometry are selected depending on the tooth type, the internal structures of different types of replacement teeth can be determined differently. In this way, a particularly lifelike reconstruction of the replacement teeth is achieved.

[0030] In one variant, the procedure additionally includes: determining a tooth property of the replacement tooth based on the outer shell data, or obtaining tooth property information that describes a tooth property of the replacement tooth, and selecting the compression dimension and / or the reference geometry depending on the tooth property. In this context, a tooth property refers to any characteristic that describes the replacement tooth. In particular, replacement teeth of the same tooth type can also be distinguished based on the tooth property. In other words, replacement teeth of the same tooth type can be individualized based on the tooth property. An example of a tooth property is the size of the replacement tooth. This can include both absolute dimensions in different dimensions and ratios of the dimensions of the replacement tooth in different dimensions.Absolute values ​​of the dimensions of the replacement tooth along the X-axis, Y-axis, and Z-axis of a tooth-specific coordinate system, and their relationships to one another, can be considered. As previously explained, a bounding box can be used for this purpose. Consequently, the compression dimension and / or the reference geometry can be selected depending on the size of the replacement tooth. Thus, different compression dimensions and / or reference geometries can also be used for replacement teeth of the same tooth type. Another example of a tooth property is the position of the replacement tooth on the jaw. Therefore, the compression dimension and / or the reference geometry can be selected depending on the position of the replacement tooth on the jaw. In this way, a particularly lifelike appearance of the replacement tooth can be achieved.

[0031] Furthermore, the process may include providing internal structure information that describes at least one geometry and / or location of a subvolume. If multiple subvolumes are planned, the internal structure information naturally describes the geometry and / or location of all subvolumes within the outer shell of the replacement tooth. Such structure information is particularly important for machines and systems used to manufacture the replacement tooth. A 3D printer is one example of such a machine. This allows for the efficient and reliable production of the replacement tooth with the specified internal structure.

[0032] In the event that a replacement tooth with an internal structure generated by the inventive method is to be manufactured using an additive manufacturing process, for example, 3D printing, a layered structure can be defined for the replacement tooth with the internal structure generated by the inventive method using known methods, so that this replacement tooth can be manufactured layer by layer. In this context, for example, materials with different properties are used for the different subvolumes of the internal structure. Accordingly, multi-material or multi-color 3D printing processes are particularly suitable for manufacturing a replacement tooth with an internal structure defined by the inventive method.

[0033] According to a second aspect of the invention, a method for manufacturing a replacement tooth with a predetermined outer shell is provided. The method comprises: Determining an internal structure of the replacement tooth with at least one subvolume using the inventive method for determining an internal structure of a replacement tooth, and manufacturing the replacement tooth with the determined internal structure using materials that differ in at least one selected aspect of material, color and translucency.

[0034] Thus, different materials are used to fabricate the internal structure of the replacement tooth, varying in material, color, and / or translucency. Such a replacement tooth is characterized by an extremely natural appearance. At the same time, the method according to the invention is comparatively simple and can be easily implemented, in particular, within a CAD / CAM workflow.

[0035] According to a third aspect of the invention, a replacement tooth is provided with an outer shell and an internal structure. The internal structure is determined using the inventive method for determining the internal structure of a replacement tooth. As already mentioned, the fidelity of replacement teeth depends not only on an outer shell that is as true to life as possible, but also on the internal structure of the replacement tooth. Similar to a natural tooth, whose internal structure can essentially be subdivided into a root, a dentin core, and an incisal edge, the natural appearance of a replacement tooth also depends on the interaction of various sections or layers that exhibit different optical properties, in particular different translucencies. The entirety of these different sections or layers constitutes the internal structure of the replacement tooth.Such a replacement tooth is therefore characterized by an extremely natural appearance.

[0036] According to a fourth aspect of the invention, a data processing device is provided. The data processing device comprises means for carrying out the inventive method for determining the internal structure of a replacement tooth. As already mentioned, the inventive method for determining the internal structure of a replacement tooth can be used to determine an internal structure for a replacement tooth that gives the replacement tooth an extremely natural appearance. By using an inventive data processing device, such an internal structure for a replacement tooth can be determined simply and reliably.

[0037] According to a fifth aspect of the invention, a computer program is provided. This computer program comprises commands which, when executed by a computer, cause the computer to perform the inventive method for determining the internal structure of a replacement tooth. As already mentioned, the inventive method for determining the internal structure of a replacement tooth can be used to determine an internal structure that gives the replacement tooth an extremely natural appearance. By using a computer program according to the invention, such an internal structure for a replacement tooth can be determined simply and reliably.

[0038] According to a sixth aspect of the invention, a computer-readable medium is provided. This computer-readable medium comprises commands which, when executed by a computer, cause the computer to perform the inventive method for determining the internal structure of a replacement tooth. As already mentioned, the inventive method for determining the internal structure of a replacement tooth can be used to determine an internal structure for a replacement tooth that gives the replacement tooth an extremely lifelike appearance. By using a computer-readable medium according to the invention, such an internal structure for a replacement tooth can be determined simply and reliably.

[0039] It is understood that the aforementioned examples and embodiments can be combined independently of the aspect of the present invention in which they were explained.

[0040] It should be noted that both the terms opacity and translucency have been used here. Opacity is the reciprocal of translucency, and vice versa. High opacity is therefore synonymous with low translucency, and low opacity with high translucency. Opacity and translucency can be converted into one another.

[0041] The invention is explained below with reference to various embodiments shown in the accompanying drawings. These show: Figure 1 shows a data processing device according to the invention, comprising a computer-readable medium and a computer program according to the invention, wherein the data processing device is configured to execute a method according to the invention for determining the internal structure of a replacement tooth, and wherein the data processing device is coupled to a manufacturing device so that a replacement tooth according to the invention can be manufactured using a method according to the invention for manufacturing a replacement tooth. Figure 2 shows a replacement tooth according to the invention according to a first embodiment and steps of a first embodiment of the method for determining the internal structure of a replacement tooth. Figure 3 shows a replacement tooth according to the invention according to a second embodiment and steps of a second embodiment of the method for determining the internal structure of a replacement tooth.Figures 4 to 8 show an internal structure of a replacement tooth according to the invention in accordance with a third embodiment and steps of a third embodiment of the method for determining an internal structure of a replacement tooth; Figures 9 and 10 show an internal structure of a replacement tooth according to the invention in accordance with a fourth embodiment and steps of a fourth embodiment of the method for determining an internal structure of a replacement tooth.

[0042] Figure 1 shows a device 10 for data processing.

[0043] This includes a storage unit 12 and a computing unit 14.

[0044] The storage unit 12 has a computer-readable medium 16.

[0045] A computer program 18 is stored on the computer-readable medium 16, i.e. also on the storage unit 12.

[0046] The computer program 18 and thus also the computer-readable medium 16 comprise instructions which, when the computer program 18 is executed by the computing unit 14 or, more generally, by a computer, cause the computing unit 14 or the computer to execute a procedure for determining an internal structure of a replacement tooth.

[0047] Consequently, the storage unit 12 and the computing unit 14 constitute means 20 for carrying out the procedure for determining an internal structure of a replacement tooth.

[0048] In the example of the Figure 1 The data processing device 10 is furthermore coupled to a manufacturing device 22 via communication technology. The manufacturing device 22 is configured to produce a replacement tooth 24 which has an internal structure that was determined using the method for determining the internal structure of the replacement tooth 24.

[0049] For this reason, in the illustrated embodiment, the storage unit 12 additionally includes a computer program 26 for controlling the manufacturing device 22. In other words, the computer program 26 includes instructions which, when the computer program 26 is executed by the computing unit 14 or, more generally, by a computer, cause the computing unit 14 or the computer to control the manufacturing device 22.

[0050] In the example of the Figure 1 The manufacturing device 22 is designed to produce the replacement tooth 24 additively or generatively. In simplified terms, the manufacturing device 22 can therefore be described as a 3D printer.

[0051] Figure 2 Figure 1 shows a first embodiment of the replacement tooth 24. In this example, the replacement tooth 24 is designed to replace a back tooth or molar.

[0052] The replacement tooth 24 has an outer shell 28 and an inner structure 30.

[0053] The internal structure 30 was determined using the procedure for determining the internal structure 30 of the replacement tooth 24, as will be explained in detail below.

[0054] In order to be able to carry out the procedure using the device 10 for data processing and also to simplify the explanation of the procedure, a tooth-specific coordinate system is first defined.

[0055] The origin of this coordinate system lies in the center of volume of the outer shell 28 of the replacement tooth 24.

[0056] To determine the direction of the X-axis, the orientation and position of the replacement tooth 24 in the human jaw are considered. If several teeth are present in the jaw, the corresponding centroid of volume of the outer shell can be determined for each tooth. Connecting all the centroids of volume of all teeth in the jaw results in a so-called dental arch. In this context, the X-axis runs tangentially to the dental arch.

[0057] It is understood that, strictly speaking, the dental arch is only defined when the position and orientation of the teeth adjacent to the tooth under consideration are also known. However, a person skilled in the art can determine the relevant section of the dental arch based solely on the outer surface 28 of the replacement tooth 24. This is because, based on the geometric features of the outer surface 28, a person skilled in the art can deduce the orientation and arrangement of the tooth in the jaw.

[0058] The Z-axis runs perpendicular to the X-axis and is oriented towards occlusion. This means that the Z-axis points towards the tooth tip or away from the tooth root.

[0059] The Y-axis is perpendicular to both the X-axis and the Z-axis and is positive in the direction towards the tongue or palate.

[0060] Even though the origin of this coordinate system lies in the center of volume of the outer shell 28, the coordinate systems are always shown outside the associated replacement tooth 24 in the figures for the sake of clarity.

[0061] In a first step S1 of the procedure for determining the internal structure 30 of the replacement tooth 24, outer shell data are obtained that describe the outer shell 28 of the replacement tooth 24.

[0062] In the illustrated embodiment, the outer shell data is obtained from a so-called tooth library, in which a large number of outer shell data for different replacement teeth 24 are stored. The outer shell data for each replacement tooth 24 is stored in a separate file, which can also be referred to as a volume file.

[0063] The dental library is stored on storage unit 12.

[0064] In other words, the outer shell data is obtained from the tooth library on storage unit 12. This outer shell data also includes so-called metadata, which in the example shown comprises tooth type information describing the tooth type of the replacement tooth 24.

[0065] The tooth type in question is a molar, or back tooth.

[0066] It is emphasized that the outer shell data contains no information whatsoever about the internal structure 30 of the replacement tooth 24.

[0067] In a second step S2, a first reference geometry information is defined, which describes a first reference geometry B1. The first reference geometry B1 virtually divides the outer shell 28 into a first shell section 28a and a second shell section 28b.

[0068] In the example from Figure 2 The first reference geometry B1 is a so-called equator line. The use of the equator line as the first reference geometry B1 is linked to the tooth type, which in this case is molar. In other words, the reference geometry B1 is chosen depending on the tooth type.

[0069] Subsequently, in a third step S3, a first compression shell 32 is defined.

[0070] This is achieved by compressing the first hull section 28a in the direction of the first reference geometry B1, opposite to the direction defined by the positive Z-axis, i.e., in the negative Z-direction, by a first compression dimension M1. The first reference geometry B1 represents a compression base that is immobile. The second hull section 28b also remains unchanged.

[0071] The first compression measure M1 is also defined depending on the tooth type, i.e., for molars. In this context, a compression measure indicates the degree of virtual compression. The compression measure can be specified absolutely or relatively, e.g., as a percentage, i.e., in relation to the height or width of the tooth.

[0072] Consequently, based on the first shell section 28a, the second shell section 28b and the first compression shell 32, a first subvolume 34 and a second subvolume 36 can be derived in a fourth step S4.

[0073] The first subvolume 34 is bounded by the first compression shell 32 and the first shell section 28a of the outer shell 28.

[0074] The second subvolume 36 is bounded by the compression shell and by the second shell section 28b of the outer shell 28.

[0075] Furthermore, in a fifth step S5 a second compression shell 38 is generated.

[0076] For this purpose, the first reference geometry B1 is used again and the first hull section 28a is virtually compressed along the negative Z direction towards the first reference geometry B1.

[0077] Now a second compression dimension M2 is used, which in the example shown is smaller than the first compression dimension M1.

[0078] The second compression measure M2 is also determined depending on the tooth type, i.e. for molars.

[0079] Consequently, in a sixth step, S6 can be derived again as subvolumes.

[0080] A third subvolume 40 is bounded by the second compression shell 38 and by the first shell section 28a.

[0081] A fourth subvolume 42 is bounded by the second compression shell 38 and the second shell section 28b.

[0082] A fifth subvolume 44 is bounded by the second compression shell 38 and by the first compression shell 32.

[0083] In a seventh step (S7), each of the subvolumes is then assigned anatomical information, a material information, a color information, and a translucency information. This means that each of the following subvolumes—first subvolume 34, second subvolume 36, third subvolume 40, fourth subvolume 42, and fifth subvolume 44—is assigned anatomical information, a material information, a color information, and a translucency information.

[0084] It is understood that the defined subvolumes are not non-overlapping and that each volume element of the replacement tooth 24 can only be assigned a single piece of anatomical information, a single piece of material information, a single piece of color information and a single piece of translucency information.

[0085] In the example shown, the anatomical information "tooth incisal edge" is assigned to the third subvolume 40. This means that the third subvolume 40 is intended to replicate a tooth incisal edge. Accordingly, a tooth incisal material, a tooth incisal color, and a tooth incisal translucency are assigned to the third subvolume 40.

[0086] In the example shown, the third subvolume 40 has a thickness of approximately 0.5 mm to approximately 2.5 mm, where the thickness is measured along the z-axis.

[0087] In this context, the tooth cutting material can be a zirconium oxide ceramic, which has a comparatively high yttrium content.

[0088] The color of the incisal edges of the teeth is, for example, white or yellowish-brown, or a mixture of white and yellowish-brown.

[0089] The incisal translucency is preferably high.

[0090] Alternatively, a filled photopolymer based on methacrylates and / or acrylates can be used as the tooth cutting material.

[0091] In this context, a mixture of a light-colored, low-opacity polymer (e.g., 55%) and a dark-colored, high-opacity polymer (e.g., 85%) can be used for the incisal edge of the tooth. The proportion of the light-colored polymer in the mixture is much higher than the proportion of the dark-colored polymer.

[0092] The fifth subvolume 44 is assigned the anatomical information of a dentin core. This means that the fifth subvolume 44 is intended to replicate a dentin core. Accordingly, a dentin core material, a dentin core color, and a dentin core translucency are assigned to the fifth subvolume 44.

[0093] In this context, the dentin core material can be a zirconia ceramic with a low or medium yttrium content. The yttrium content of the dentin core material is lower than the yttrium content of the incisal edge material.

[0094] The dentin core color, for example, is a mixture of white, pink, grey, yellow and yellowish-brown.

[0095] Dentin core translucency is preferably low, especially lower than incisal edge translucency.

[0096] Alternatively, a filled photopolymer based on methacrylates and / or acrylates can be used as the dentin core material.

[0097] In this context, a mixture of a polymer with a light tooth color and high opacity, e.g. 85%, and a polymer with a dark tooth color and high opacity, e.g. 85%, can be used for the dentin core.

[0098] Furthermore, the anatomical information of the tooth neck is assigned to the second subvolume 36. Accordingly, the second subvolume 36 is intended to replicate a tooth neck.

[0099] Therefore, the second subvolume 36 is assigned a cervical material, a cervical color, and a cervical translucency.

[0100] In this context, the cervical material can be a zirconia ceramic with a low or medium yttrium content. The yttrium content of the cervical material is lower than the yttrium content of the dentin core material and consequently also lower than the yttrium content of the incisal edge material.

[0101] The cervical color of the tooth, for example, is a mixture of white, pink, gray, yellow, and yellowish-brown. However, the cervical color is darker than the dentin core color.

[0102] Cervical translucency is preferably low, especially lower than dentin core translucency.

[0103] Alternatively, a filled photopolymer based on methacrylates and / or acrylates can be used as the tooth neck material.

[0104] In this context, a mixture of a light-colored, high-opacity polymer (e.g., 85%) and a dark-colored, high-opacity polymer (e.g., 85%) can be used for the cervical area of ​​the tooth. The proportion of the light-colored polymer is lower than that used for the dentin core, and the proportion of the dark-colored polymer is higher than that used for the dentin core.

[0105] In simplified terms, the method for determining the internal structure 30 of the replacement tooth 24 allows subvolumes to be defined within an outer shell 28 of the replacement tooth, each intended to replicate an anatomical section of a tooth.

[0106] In principle, it is conceivable that the second subvolume 36, the third subvolume 40 and the fifth subvolume 44 differ in terms of their material, color and translucency.

[0107] Thus, the material, color and translucency can be selected for each of the second subvolume 36, third subvolume 40 and fifth subvolume 44, resulting in a natural appearance for the replacement tooth 24.

[0108] In an eighth step S8, internal structure information is therefore provided, which describes a geometry and position for each of the subvolumes, but at least for the second subvolume 36, the third subvolume 40 and the fifth subvolume 44.

[0109] In the illustrated embodiment, the internal structure information is provided to the computer program 36, which serves to control the manufacturing device 22. Consequently, the replacement tooth 24 with the internal structure 30 defined by the method can be manufactured using the manufacturing device 22.

[0110] In summary, this can also be described as a method for manufacturing the replacement tooth 24 with the specified outer shell 28. This method comprises, on the one hand, determining the internal structure 30 of the replacement tooth 24 with at least one subvolume using the described method. On the other hand, the method comprises fabricating the replacement tooth 24 with the specified internal structure 30 using materials that differ in at least one selected characteristic: material, color, and translucency. In this case, the incisal material, the dentin core material, and the cervical material are used.

[0111] In detail, the computer program 36 generates layer data describing the replacement tooth 24. The replacement tooth 24 is thus virtually sectioned into layers that are oriented, for example, perpendicular to the Z-direction.

[0112] Each layer can comprise one or more sections from one or more of the second subvolume 36, third subvolume 40 and fifth subvolume 44.

[0113] Therefore, in each layer, material information, color information, and translucency information must be assigned to each of these sections.

[0114] This data is provided for manufacturing device 22.

[0115] Two exemplary data formats for providing this information are the 3MF format and the OBJ format.

[0116] Figure 3 Figure 2 shows a second embodiment of the replacement tooth 24. As before, the replacement tooth 24 has an outer shell 28 and an inner structure 30.

[0117] In this example, too, the replacement tooth 24 is designed to replace a back tooth or molar.

[0118] The internal structure 30 was determined using a second embodiment of the method for determining the internal structure 30 of the replacement tooth 24. The following discussion focuses solely on the differences compared to the first embodiment of the method for determining the internal structure 30 of the replacement tooth 24.

[0119] The difference lies in the first reference geometry B1, which is used as the basis for compression.

[0120] While in the first embodiment the first reference geometry B1 is defined by the equator line, in the second embodiment the first reference geometry B1 is defined according to Figure 3 The line is formed by a plane parallel to the XY plane, encompassing the point on the equator that has the highest horizontal tangent. A horizontal tangent is defined as one parallel to the XY plane. The height is measured along the Z-axis.

[0121] Furthermore, reference can be made to the explanations for the first example embodiment.

[0122] The Figures 4 to 8 Figure 24 shows a third embodiment of the replacement tooth 24. In this example, the replacement tooth 24 is designed to replace a front tooth, i.e., an incisor or a canine tooth.

[0123] As before, the replacement tooth 24 has an outer shell 28 and an inner structure 30.

[0124] Furthermore, the tooth-specific coordinate system defined above is used.

[0125] Even though the origin of this coordinate system lies in the center of volume of the outer shell 28, for the sake of clarity the coordinate systems are always shown outside the associated replacement tooth 24 in the figures.

[0126] As in the examples already explained, in a first step S1 outer shell data is obtained, which describe the outer shell 28 of the replacement tooth 24.

[0127] In the third embodiment, the outer shell data is also retrieved from the tooth library stored on the storage unit 12. This outer shell data again includes metadata, which contains tooth type information describing the tooth type of the replacement tooth 24.

[0128] The tooth type in question is a front tooth. This means it refers to either an incisor or a canine tooth.

[0129] In the second step S2, a first reference geometry information is defined again, which describes a first reference geometry B1. The reference geometry virtually divides the outer shell 28 into a first shell section 28a and a second shell section 28b.

[0130] In the third embodiment, the first reference geometry B1 is defined by a plane formed by the YZ plane.

[0131] This plane therefore also includes the center of volume of the replacement tooth, i.e., the center of volume of the outer shell 28. The center of volume corresponds to the center of mass if a uniform mass distribution is assumed.

[0132] In the third step S3, the first compression shell 32 is defined by compression on both sides. This compression on both sides is subsequently described as a single step. Strictly speaking, however, it consists of two sub-steps.

[0133] This means that the one in the Figure 4 and in the Figure 5 The first shell section 28a shown on the right is compressed in the direction of the first reference geometry B1, contrary to the positive direction of the X-axis.

[0134] Furthermore, the one in the Figure 4 and in the Figure 5 The second hull section 28b shown on the left is compressed along the positive X-axis to the first reference geometry B1.

[0135] Both compressions use the first compression measure M1, which is again determined depending on the tooth type, i.e., here for front teeth.

[0136] Consequently, based on the first shell section 28a, the second shell section 28b and the first compression shell 32, a sixth subvolume 46, a seventh subvolume 48 and an eighth subvolume 50 can be derived in the fourth step S4.

[0137] It is understood that the designations of the subvolumes as sixth subvolume 46, seventh subvolume 48, and eighth subvolume 50 serve only for the sake of simplicity. The number of subvolumes is not implied by these designations.

[0138] The sixth subvolume 46 is bounded on all sides by the first compression shell 32.

[0139] The seventh subvolume 48 is bounded by the first compression shell 32 and by the first shell section 28a of the outer shell 28.

[0140] The eighth subvolume 50 is bounded by the first compression shell 32 and by the second shell section 28b of the outer shell 28.

[0141] In a subsequent fifth step S5, a second reference geometry information is defined, which describes a second reference geometry B2 that is different from the first reference geometry B1.

[0142] The second reference geometry B2 virtually divides the outer shell 28 of the replacement tooth 24 into a third shell section 28c and a fourth shell section 28d.

[0143] Furthermore, the second reference geometry B2 divides the first compression shell 32 into a first compression shell section 32a and a second compression shell section 32b (see in particular Figure 5 ).

[0144] The second reference geometry B2 relates to a plane that runs parallel to the X-axis and includes a top point 52 of the outer shell 28 of the replacement tooth 24 and a bottom point 54 of the outer shell 28 of the replacement tooth 24 (see in particular Figure 6 ).

[0145] Based on this, in a sixth step S6, a third compression shell 56 is defined by virtually compressing the first compression shell section 32a of the first compression shell 32 in the direction of the second reference geometry B2. A third compression dimension M3 is used (see Figure 6 ).

[0146] The second compression shell section 32b and the second reference geometry B2 are fixed.

[0147] The compression therefore occurs along a positive direction of the Y-axis.

[0148] Optionally, as part of the sixth step S6, it would also be possible to virtually compress the second compression shell section 32b in the direction of the second reference geometry B2. However, this is not shown in the figures.

[0149] Consequently, in a seventh step, based on the first compression shell section 32a, the second compression shell section 32b and the third compression shell 56, a ninth subvolume 58 and a tenth subvolume 60 can be derived.

[0150] The ninth subvolume 58 is bounded by the first compression shell section 32a and the third compression shell 56.

[0151] The tenth subvolume 60 is bounded by the second compression shell section 32b and the third compression shell 56.

[0152] For better illustration, the third compression sleeve 56 is shown with a dashed line in this context. Figure 5 drawn, although in the representation according to Figure 5 Actually, no compression of the first compression shell 32 has yet taken place.

[0153] In a subsequent eighth step S8, a third reference geometry information is defined, which describes a third reference geometry B3 that is different from the first reference geometry B1 and the second reference geometry B2.

[0154] The third reference geometry B3 virtually divides the outer shell 28 of the replacement tooth 24 into a fifth shell section 28e and a sixth shell section 28f.

[0155] Furthermore, the third reference geometry B3 divides the third compression shell 56 into a first compression shell section 56a and a second compression shell section 56b. Likewise, the second compression shell section 32b is divided into two parts.

[0156] In other words, the third reference geometry B3 divides the tenth subvolume 60 into two parts.

[0157] The third reference geometry B3 relates to a plane that runs parallel to the XY plane and encompasses a maximum circumference of the outer shell 28 around the Z-axis.

[0158] In an alternative, not shown in detail, an equator line can be used as the third reference geometry B3.

[0159] Based on this, in a ninth step S9 a fourth compression shell 62 is created by virtually compressing the first compression shell section 56a of the third compression shell and the section in the Figure 6 The section of the first compression shell 32 lying above the third reference geometry is defined.

[0160] The compression therefore occurs along a negative direction of the Z-axis.

[0161] A fourth compression dimension M4 is used (see in particular Figures 7 and 8 ).

[0162] Then, in a tenth step S9, a fifth compression shell 64 is created by virtually compressing the first compression shell section 56a of the third compression shell and the section in the Figure 6 The section of the first compression shell 32 lying above the third reference geometry is defined. In contrast to the previous approach, however, a fifth compression dimension M5 is used, which is larger than the fourth compression dimension M4.

[0163] This compression also occurs along a negative direction of the Z-axis.

[0164] It is therefore possible to derive an eleventh subvolume 66, which is bounded by the fifth compression shell 64 and by the sections of the first compression shell 32 lying below the third reference geometry.

[0165] Furthermore, a twelfth subvolume 68 can be derived, which is bounded by the fifth compression shell 64 and the fourth compression shell 62.

[0166] Furthermore, a thirteenth subvolume 70 can be derived, which is defined as the difference between a volume enclosed by the outer shell 28 and the eleventh subvolume 66 and the twelfth subvolume 68. In other words, those sections of the volume enclosed by the outer shell 28 that belong neither to the eleventh subvolume 66 nor to the twelfth subvolume 68 constitute the thirteenth subvolume 70.

[0167] In the following eleventh step S11, as already explained, each of the subvolumes is assigned anatomical information, material information, color information, and translucency information.

[0168] In the example shown, the anatomical information "tooth incisor" is assigned to the thirteenth subvolume 70. This means that the thirteenth subvolume 70 is intended to replicate a tooth incisor. Accordingly, a tooth incisor material, a tooth incisor color, and a tooth incisor translucency are assigned to the thirteenth subvolume 70.

[0169] The twelfth subvolume 68 is assigned the anatomical information of a dentin core. This means that the twelfth subvolume 68 is intended to replicate a dentin core. Accordingly, a dentin core material, a dentin core color, and a dentin core translucency are assigned to the twelfth subvolume 68.

[0170] Furthermore, the anatomical information of the tooth neck is assigned to the eleventh subvolume 66. Accordingly, the eleventh subvolume is intended to replicate a tooth neck. Therefore, a tooth neck material, a tooth neck color, and a tooth neck translucency are assigned to the eleventh subvolume 66.

[0171] In simplified terms, the method for determining the internal structure 30 of the replacement tooth 24 allows subvolumes to be defined within an outer shell 28 of the replacement tooth, each intended to replicate an anatomical section of a tooth.

[0172] In principle, it is conceivable that the eleventh subvolume 66, the twelfth subvolume 68 and the thirteenth subvolume 70 differ in terms of their material, color and translucency.

[0173] Thus, the material, color and translucency can be selected for each of the eleventh subvolume 66, twelfth subvolume 68 and thirteenth subvolume 70, resulting in a natural appearance for the replacement tooth 24.

[0174] Regarding the provision of the internal structure information and the procedure for manufacturing the replacement tooth, reference can be made to the explanations in the preceding examples.

[0175] The Figures 9 and 10 show a fourth embodiment of the replacement tooth 24.

[0176] Again, replacement tooth 24 is designed to replace a front tooth, i.e., an incisor or a canine.

[0177] As before, the replacement tooth 24 has an outer shell 28 and an inner structure 30.

[0178] Furthermore, the tooth-specific coordinate system defined above is used.

[0179] Even though the origin of this coordinate system lies in the center of volume of the outer shell 28, for the sake of clarity the coordinate systems are always shown outside the associated replacement tooth 24 in the figures.

[0180] As in the examples already explained, in a first step S1 outer shell data is obtained, which describe the outer shell 28 of the replacement tooth 24.

[0181] In the fourth embodiment, the outer shell data is also retrieved from the tooth library stored on the storage unit 12. This outer shell data again includes metadata, which contains tooth type information describing the tooth type of the replacement tooth 24.

[0182] In this case, the tooth type is again an anterior tooth. This tooth type therefore refers to an incisor or a canine. In the illustrated embodiment, the replacement tooth according to the fourth embodiment is identical to the replacement tooth according to the third embodiment with respect to its outer shell 28.

[0183] In the second step S2, a first reference geometry B1 is defined again, and in the third step S3, a virtual compression is performed. These steps correspond to the second step S2 and the third step S3 according to the third embodiment, which was already described in the Figures 4 to 8 was explained. In particular, reference can be made in this context to the Figures 4 and 5 be referred.

[0184] In contrast to the third embodiment, no compression using the second reference geometry B2 takes place. These steps are omitted in the fourth embodiment.

[0185] The subsequent steps of the fourth embodiment then correspond again to the third embodiment.

[0186] In a fifth, simplified embodiment, S1 outer shell data is obtained in a first step, as before.

[0187] In the second step S2, a bounding box is placed around the outer hull 28 to define at least one first reference geometry B1. The bounding box can have two parallel interfaces parallel to the XY plane, two parallel interfaces parallel to the XZ plane, and two parallel interfaces parallel to the YZ plane.

[0188] In the subsequent virtual compressions, one or more of the interfaces can be used as the reference geometry. As already explained, several virtual compressions can also be performed using the same reference geometry, i.e., the same interface, but with different compression measures.

[0189] In this context, it can happen that part of the compressed section of the outer shell penetrates the original outer shell to the outside.

[0190] This is not desired, so such sections of compression sleeves, also known as extruding sections, are ignored.

[0191] In the present embodiments, fixed compression dimensions M1, M2, M3, M4, and M5 were always used. This is advantageous because the virtual compressions can thus be performed completely automatically. In this context, the compression dimensions M1, M2, M3, M4, and M5 can, for example, be fixed for specific tooth types or tooth groups. The compression dimensions M1, M2, M3, M4, and M5 can also be defined as a function of the outer dimensions of the outer shell 28. These outer dimensions can, for example, be described by a so-called bounding box. This means that a cuboid is virtually placed around the outer shell 28, which is just large enough to accommodate the outer shell 28. The edges of the bounding box are oriented parallel to the axes of the tooth-specific coordinate system.

[0192] Optionally, the device 10 can also be equipped with the option for a user to manually enter and / or change one or more of the compression dimensions M1, M2, M3, M4, M5 for data processing. This allows the user to selectively influence the derived subvolumes. Reference symbol list

[0193] 10 Data processing device 12 Storage unit 14 Computing unit 16 Computer-readable medium 18 Computer program 20 Means of carrying out a method for determining an internal structure of a replacement tooth 22 Manufacturing device 24 Replacement tooth 26 Computer program 28 Outer shell 28a First shell section 28b Second shell section 28c Third shell section 28d Fourth shell section 28f Fifth shell section 28f Sixth shell section 30 Internal structure 32 First compression shell 32a First compression shell section 32b Second compression shell section 34 First subvolume 36 Second subvolume 38 Second compression shell 40 Third subvolume 42 Fourth subvolume 44 Fifth subvolume 46 Sixth subvolume 48 Seventh subvolume 50 Eighth subvolume 52 Top point 54 lowest point 56 third compression shell 58 ninth subvolume 60 tenth subvolume 62 fourth compression shell 64 fifth compression shell 66 eleventh subvolume 68 twelfth subvolume 70 thirteenth subvolume B1 first reference geometry B2 secondReference geometry B3 third reference geometry M1 first compression dimension M2 second compression dimension M3 third compression dimension M4 fourth compression dimension M5 fifth compression dimension S1 first step S2 second step S3 third step S4 fourth step S5 fifth step S6 sixth step S7 seventh step S8 eighth step S9 ninth step S10 tenth step S11 eleventh step

Claims

1. Method for determining an internal structure (30) of a replacement tooth (24), comprising: - obtaining outer shell data describing an outer shell (28) of the replacement tooth (24), - defining or obtaining first reference geometry information describing a first reference geometry (B1) which virtually divides the outer shell (28) of the replacement tooth (24) into a first shell portion (28a) and a second shell portion (28b), characterised by - creating a first compression shell (32) by virtually compressing the first shell portion (28a) in one direction with respect to the first reference geometry (B1) by a first degree of compression (M1), the first reference geometry (B1) forming a compression basis, and - deriving at least one sub-volume (34, 36) of the replacement tooth (24) as a volume bounded by the first compression shell (32).

2. Method according to claim 1, further comprising: - creating a second compression shell (38) by virtually compressing the first shell portion (28a) or the first compression shell (32) in one direction with respect to the first reference geometry (B1) by a second degree of compression (M2), the first reference geometry (B1) forming a compression basis, and - deriving at least one sub-volume (40, 42, 44) of the replacement tooth as a volume bounded by the second compression shell (38).

3. Method according to either claim 1 or claim 2, further comprising: - defining or obtaining second reference geometry information describing a second reference geometry (B2), which is different from the first reference geometry (B1) and virtually divides the outer shell (28) of the replacement tooth (24) into a third shell portion (28c) and a fourth shell portion (28d), - creating a third compression shell (56) by virtually compressing the third shell portion (28c) or the first compression shell (32) or the second compression shell (38) in one direction with respect to the second reference geometry (B2) by a third degree of compression (M3), the second reference geometry (B2) forming a compression basis, and - deriving at least one sub-volume (58, 60) of the replacement tooth (24) as a volume bounded by the third compression shell (56).

4. Method according to any of the preceding claims, further comprising: assigning material information, colour information, translucency information and / or anatomy information to one or more of the sub-volumes (34, 36, 40, 42, 44, 58, 60).

5. Method according to any of the preceding claims, wherein at least one reference geometry (B1, B2, B3) is defined by an equator line of the outer shell (28) of the replacement tooth (24), or wherein at least one reference geometry (B1, B2, B3) is defined by a plane which includes a centre of mass and / or centre of volume of the outer shell (28) of the replacement tooth (24), or wherein at least one reference geometry (B1, B2, B3) is defined by a plane which includes an extremum (52, 54) of the outer shell (28) of the replacement tooth (24).

6. Method according to any of the preceding claims, further comprising: ignoring portions of at least one compression shell (32, 38, 56) which are outside the outer shell (28) of the replacement tooth (24).

7. Method according to any of the preceding claims, wherein a compression direction extends along a tooth height direction of the replacement tooth (24), a tooth width direction of the replacement tooth (24) or a tooth depth direction of the replacement tooth (24).

8. Method according to any of the preceding claims, further comprising: determining a tooth type of the replacement tooth (24) on the basis of the outer shell data or obtaining tooth type information describing a tooth type of the replacement tooth (24), and selecting the degree of compression (M1, M2, M3) and / or the reference geometry (B1, B2, B3) as a function of the tooth type.

9. Method according to any of the preceding claims, further comprising: determining a tooth property of the replacement tooth (24) on the basis of the outer shell data or obtaining tooth property information describing a tooth property of the replacement tooth (24), and selecting the degree of compression (M1, M2, M3) and / or the reference geometry (B1, B2, B3) as a function of the tooth property.

10. Method according to any of the preceding claims, further comprising: providing internal structure information describing at least a geometry and / or position of a sub-volume (34, 36, 40, 42, 44, 58, 60).

11. Method for producing a replacement tooth (24) with a predetermined outer shell (28), comprising: - determining an internal structure (30) of the replacement tooth (24) with at least one sub-volume by the method according to any of the preceding claims, and - manufacturing the replacement tooth (24) with the determined internal structure (30) using materials which differ in at least a selected one of material, colour and translucency.

12. Replacement tooth (24) with an outer shell (28) and an internal structure (30), wherein the internal structure (30) is determined by the method according to any of claims 1 to 10.

13. Data processing device (10) comprising means (20) for carrying out the method according to any of claims 1 to 10.

14. Computer program (18) comprising commands which, when the computer program (18) is executed by a computer, cause said computer to carry out the method according to any of claims 1 to 10.

15. Computer-readable medium (16) comprising commands which, when executed by a computer, cause said computer to carry out the method according to any of claims 1 to 10.