Method for producing a removable dental prosthesis, and removable dental prosthesis produced according to the method

Abstract

The invention relates to a method for producing a first connection element of a removable dental prosthesis, said connection element being suitable for a sliding connection between a first fit surface of the first connection element and a second fit surface of a second connection element of the removable dental prosthesis. The invention is characterized in that the first connection element is produced by connecting a stability-granting material and a ductile material which forms the first fit surface in an additive multi-material manufacturing method.

Description

[0001] Method for producing removable dentures and removable dentures produced by the method

[0002] The invention relates to a method for producing a first connecting element of a removable dental prosthesis, which is suitable for a sliding connection between a first fitting surface of the first connecting element and a second fitting surface of a second connecting element of the removable dental prosthesis, and to a removable dental prosthesis produced according to this method.

[0003] Removable dentures represent a key treatment solution in the event of tooth loss, due to their ease of cleaning, expandability, ease of handling and high level of comfort, among other things. Telescopic crowns, also called double crowns, are a particularly aesthetic treatment solution. For example, an inner telescope (primary part) is firmly cemented in the mouth, while the outer telescope (secondary part) is removable. The complete denture is connected to the secondary part. Different bonding mechanisms, primarily friction and adhesion, are responsible for the secure fit of the secondary parts to the primary parts and prevent accidental loosening of the denture. The functionality and ease of use of the double crown as a denture depends largely on the fit between the primary and secondary parts, which primarily represents a production-related challenge.Attachment and bar attachment prostheses use the same adhesion principle, but differ from telescopic prostheses in the geometry of the connecting elements (primary and secondary part).

[0004] Precious metal alloys are particularly suitable for the production of double crowns, attachments, or bar attachments because the materials are both biocompatible and ductile, resulting in minimal deformation when the primary and secondary components are joined, ultimately enabling a smooth transition fit and thus frictional adhesion. Another option for producing double crowns is so-called "adhesion telescopes." These are not based on the principle of friction, but rather on the principle of adhesion. This requires an extremely high degree of fit between the primary and secondary components. Currently, a very thin secondary component made of pure gold is often deposited directly onto the primary component using electroplating technology to produce adhesion telescopes.Since the wafer-thin fine gold secondary parts are very sensitive, they must be glued into a so-called tertiary structure made of a strength-giving material, often cobalt-chromium alloys, which requires considerable manual effort and high overall costs.

[0005] Due to the high price of precious metals and the considerable manual effort required, attempts are often made to fabricate double crowns, attachments, or bar attachments, as well as their restorations, without precious metal secondary components, i.e., to use exclusively non-precious metal alloys. The primary and especially the secondary components are often manufactured using casting techniques, laser beam melting, or machining from appropriate blanks (“CAD / CAM manufacturing”). Regardless of the manufacturing process, the fit between the primary and secondary components must be achieved using machining (hybrid manufacturing). However, due to the high elastic moduli of non-precious metal alloys or ceramics suitable for dental technology, as well as the overall manufacturing accuracies currently achievable, it is only possible to manufacture telescopic crowns, attachments, and bar attachments with the required fits with extremely high costs.Commercially available telescopic crowns, attachments, and bar attachments made of non-precious metal alloys or ceramics therefore exhibit poorer and less consistent bonding properties than telescopic crowns, attachments, or bar attachments with precious metal content. For this reason, additional retention elements, such as the Marburg double crown, are often used.

[0006] In contrast, the object of the invention is to provide a more advantageous method for producing removable dental prostheses, in particular telescopic, sliding and bar-type dental prostheses, as well as a removable dental prosthesis produced by this method.

[0007] According to the invention, this object is achieved in a method of the type mentioned at the outset in that the first connecting element is produced by joining a strength-providing material and a ductile material forming the first fitting surface in an additive multi-material manufacturing process.

[0008] The term "connecting element" is to be understood here as referring to both embodiments in which the fitting surfaces are aligned parallel to the sliding axis, and embodiments in which the fitting surfaces are inclined relative to the sliding axis at an angle often referred to as a "cone angle." Furthermore, the term "primary part" refers to the first or second connecting element intended for attachment in the mouth, while the term "secondary part" refers to the removable first or second connecting element. Furthermore, the term "connecting element" includes, in particular, telescopic parts of telescopic dentures and / or double crowns, as well as attachment or bar attachment parts of attachment or bar attachment dentures.

[0009] With the additive multi-material manufacturing method used in the invention, using powder-bed-based melting of metals, several materials can now be processed simultaneously in a single process. The materials initially exist as separate powders. During the manufacturing process, a workpiece is created from the various powders, whereby, in principle, each voxel can be assigned a separate material. This offers significant advantages in terms of design freedom and makes it possible to combine the inherent properties of different materials, thus producing more powerful, functionally adapted workpieces.

[0010] The manufacturing process according to the invention solves current challenges by combining various manufacturing technologies for the production of removable dental prostheses with the use of different materials. The use of additive and subtractive processes is expanded to include the possibility of additive multi-material manufacturing of metals.

[0011] Specifically, this means that after data acquisition and processing, the primary and secondary parts are constructed in a single production job using additive multi-material manufacturing from a strength-providing material and a material with a sufficiently low modulus of elasticity, which allows for a suitable transition fit while taking into account the achievable manufacturing accuracies of the entire process chain. The ductile material required for the transition fit is used on the fitting surfaces and is built up with an oversize so that these surfaces can then be subtractively and precisely remachined using CNC milling technology. Strength-providing, durable materials should be used for all areas of the primary and secondary parts that do not directly constitute the fitting surface.

[0012] By combining strength-providing materials and materials with suitable elastic moduli, which allow for the optimal adjustment of the functional principle of the transition fit (friction), it is now possible for the first time to produce double crowns with the desired adhesion mechanism using digital manufacturing processes. Furthermore, compared to electroplating, the use of additive multi-material manufacturing reduces the number of components of the overlay structure from two to one. According to the invention, the secondary structure contains a second material, which, taking into account possible manufacturing accuracies, enables the desired transition fit through machining.

[0013] In particular, the invention enables a secondary structure with a geometrically defined, local arrangement of the second material, thus enabling the integrated production of the secondary and tertiary structures. In addition to the secondary part, the primary part can also be manufactured using the method according to the invention, i.e., with a core made of a strength-providing material and a coating made of a material with a sufficiently low modulus of elasticity. Although this is less relevant for cost reasons, it is technically conceivable.

[0014] The two materials are preferably bonded together using a material fit. However, a (micro) form fit can also be achieved.

[0015] The material pairing of the strength-giving and the ductile material particularly includes a structural material that provides the entire product with its strength. Suitable materials for medical applications include cobalt-chromium alloys (CoCr), titanium (Ti) and titanium alloys (e.g., Ti6AI4V), stainless steels (e.g., 1.4404), ceramics, and high-performance plastics. A CoCr alloy is preferred.

[0016] The material pairing also includes a functional material that, due to its lower modulus of elasticity or compression modulus and the associated greater ductility, can be machined more easily and with greater precision, enabling a high degree of fit between the primary and secondary structures. Generally, gold and other precious metals or their alloys, low-oxygen pure titanium (e.g., Ti Grade 1), copper and copper alloys, or polymers (e.g., PEEK) are suitable. A high-gold alloy is preferred.

[0017] Optionally, a third material can be used between the structural and functional materials to optimize the bond between the two materials. While this is preferably avoided and not desirable, it may be advantageous from a manufacturing perspective.

[0018] Due to the high demands placed on component resolution, powder bed fusion (PBF) is the preferred additive multi-material manufacturing process. The energy source for PBF is preferably a laser beam. Alternatively, an electron beam can be used.

[0019] The functional material is preferably applied in individual tracks using a powder application nozzle. The powder bed is freed of structural and / or third material using a suction nozzle, then thin powder tracks are deposited locally using a powder application nozzle and subsequently solidified. The structural material can be applied using a surface or local mechanism.

[0020] If the process sequence according to the invention is divided into a pre-process, an in-process and a post-process, the following process sequence preferably results:

[0021] After grinding the abutment teeth and / or placing the implants, these and their position in the mouth are digitally recorded using an intraoral scanner. The tooth- and / or implant-supported primary structure and the secondary structure are then designed using suitable CAM software. The arrangement of the functional material is implemented in the CAD model as separate areas (separate STL model or corresponding information in extended data formats such as 3MF or AMF). Interpenetration of the two (or three) materials is possible. Alternatively, analog jaw impressions can be created, which are then cast in plaster. Both the impressions and the plaster jaw models can be digitally recorded using a dental laboratory scanner.

[0022] The penetration or overlap of the materials, measured by the distance between the different scan vectors, is expediently between -1 mm (gap) and +1 mm (overlap). Preferably, the penetration is between -0.3 and +0.3 mm, although the penetration can vary depending on the orientation in 3D space. The overlap can be achieved by appropriately positioning the powder materials, by the position of the scan vectors of the respective solidification strategy, or a combination of both. For the functional material in the secondary part (formerly the secondary coping), an allowance for the removal of fine machining is expediently provided on fit-relevant surfaces.

[0023] In the in-process, the powders are preferably applied over a large area, and the structural material is vacuumed away either over a large area or selectively. The functional material and other materials are applied over a large area or selectively and also vacuumed away over a large area or selectively. The energy input in the transition or penetration region of the materials preferably lies between the energy inputs of the individual materials used in the monomaterial region. A red laser (wavelength approximately 1064 nm) is preferred as the laser source. However, lasers with other wavelengths (e.g., blue or green) or electron beams can also be used.

[0024] In the post-process following completion of the build job and depowder removal, an optional heat treatment can be performed to reduce residual stresses in the product (stress relieving) and / or improve the ductility of the functional material. The fit between the primary part and the functional material of the secondary part can then be achieved using suitable machining processes. Due to the high demands on fit accuracy, machining processes with geometrically defined cutting edges (e.g. milling) are particularly well suited. The recording of the actual geometry after the additive manufacturing process ("as built"), the comparison with the target geometry, and the corresponding adjustment (especially shifting) of the data for machining from the pre-process can be carried out tactilely or optically and with the aid of appropriate software.In a practical embodiment, the connection is made by material bonding or form-fitting or a combination of both types of connection of the two materials.

[0025] In a further expedient embodiment, the additive multi-material manufacturing process is carried out as a powder bed-based melting process with a directed laser beam or a directed electron beam.

[0026] In a further expedient embodiment, the powder bed-based melting process is carried out using a powder deposition strategy in which powder layers of the different materials are deposited in the area of ​​the joint either at a mutual distance, adjacent to one another, or overlapping one another. The powder layers of the different materials in the area of ​​the joint can be deposited simultaneously or sequentially. In particular, the powder deposition can take place before and after laser exposure. In particular, a powder layer is deposited, a portion is solidified, and then the next powder layer is deposited and likewise solidified. Furthermore, the overlapping deposition can take place such that the powder layers completely overlap. Furthermore, the materials can also be deposited over a large area and then vacuumed away again.During solidification, the laser defines where each material is ultimately located.

[0027] In another advantageous embodiment, the powder-bed-based melting process is carried out with a solidification strategy in which the different scan patterns of the beams irradiated onto the powder particles of the different materials are arranged in the bonding area either at a mutual distance, adjacent to each other, or overlapping. In all cases, the exposure parameters and scan patterns can be specifically adapted to the respective powder materials and / or their overlap.

[0028] In another expedient embodiment, the fitting surface of the first connecting element produced by multi-material manufacturing is subtractively or formatively reworked to set a so-called transition fit with respect to the second connecting element.

[0029] In all embodiments of the method according to the invention, the first connecting element can be a secondary part and the second connecting element a primary part of a removable dental prosthesis, and / or the first connecting element can be a primary part and the second connecting element a secondary part of a removable dental prosthesis.

[0030] In all embodiments of the method according to the invention, the first attachment part can be a secondary part and the second attachment part a primary part of an attachment dental prosthesis, and / or the first attachment part can be a primary part and the second attachment part a secondary part of an attachment dental prosthesis.

[0031] In all embodiments of the method according to the invention, the first bar attachment part can be a secondary part and the second bar attachment part a primary part of a bar attachment dental prosthesis, and / or the first bar attachment part can be a primary part and the second bar attachment part a secondary part of a bar attachment dental prosthesis.

[0032] In terms of the product, the object underlying the invention is achieved by a telescopic, sliding or bar-type attachment dental prosthesis with a first telescopic, sliding or bar-type attachment part which is suitable for a telescopic, sliding or bar-type attachment connection between a first fitting surface of the first telescopic, sliding or bar-type attachment part and a second fitting surface of a second telescopic, sliding or bar-type attachment part fastened in the mouth, wherein the first telescopic, sliding or bar-type attachment part is made of a multi-material material from a strength-providing material and a ductile material connected thereto, forming the first fitting surface.

[0033] In an expedient embodiment, the fitting surfaces are inclined relative to the telescope axis at an angle which is less than or equal to 10 degrees, in particular less than or equal to 6 degrees or in particular equal to zero.

[0034] The invention further extends to a telescopic, attachment or bar attachment dental prosthesis obtained by manufacturing prefabricated dental prostheses according to the method according to the invention.

[0035] The invention is explained below by way of example with reference to the attached figures.

[0036] In it show

[0037] Fig. 1 The in-process of additive multi-material manufacturing using powder bed-based melting and

[0038] Fign. 2a, b possible multi-material powder application mechanisms and Fig. 3 possible relative powder deposition positions and

[0039] Fig. 4 possible relative positions of the consolidation strategies and

[0040] Figs. 5a, b the product according to the invention in context.

[0041] Referring to Figures 1 and 2a, b, sections of the additive multi-material manufacturing process of the method according to the invention are shown. Only telescopes are shown as examples, since the functional principle of adhesion is identical for attachments and bar attachments.

[0042] Fig. 1 shows the integral production of a secondary part 3 of a telescopic crown, consisting of material A with a more ductile inner layer 4 made of material B. In this case, material A makes up the powder bed 1 and material B was selectively applied only where it is to be subsequently solidified. It is particularly advantageous if the inner layer 4 is materially bonded to the secondary part 3 and thus becomes an integral part of the telescopic crown. The left half of the image shows the areas of the product that have already been melted and solidified by the energy source 5. The right half of the image shows the areas 1 and 2 of the product that are still unsolidified in the layer shown. The process preferably takes place on a build platform 6, but would also be conceivable in principle “free floating” in the powder bed.

[0043] Different variants are possible for multi-material powder application. Figures 2a and b show conceivable approaches. In principle, flat application mechanisms 7 and 10 and selective application mechanisms 9 can be combined. Powder delivery from above 10 or from below via a dosing platform 8 can be used equally well. However, it is advantageous if the material with the highest volume fraction in the final product is applied flatly. For high-priced materials, it is advantageous if they are applied selectively. In principle, however, it would also be conceivable to apply all materials selectively. For this application, it is particularly advantageous if the functional material is deposited selectively in the form of individual tracks using a movable powder application nozzle. If necessary, it may be advantageous to remove unsolidified powder from one material using a (possibly local) powder extraction nozzle before applying a second material.Furthermore, other multi-material powder deposition systems, as described in DE 10 2019 119 113 A1 and WO 002019185626 A1, are also applicable. Referring to Figures 3 and 4, possible relative powder deposition locations (Fig. 3) and possible positions of the strategies for solidifying the components (Fig. 4) are shown. Figure 3 shows the powder particles of materials A and B of powder beds 1 and 2. Only two materials are shown as examples. However, the concept is transferable to other materials. Fig. 3 shows a distance 11 between the powder deposition locations, a discrete transition 12 between the powder materials, and an area 13 in which both materials are present. The illustration refers only to the relative position of the powders to one another. The powder materials can be deposited, solidified and removed consecutively, so that they may not mix even though they are applied at the geometrically identical location, in area 13.These relative powder positions can occur in all spatial directions. Fig. 4 shows relevant arrangements of the powder solidification strategies in relation to one another, whereby solidification strategy A 14 is to be used for material A 1 and solidification strategy B 15 is to be used for material B 2. In addition, any further solidification strategies that differ from solidification strategies A and B and are exemplified by solidification strategy C 19 can be applied to the materials at any position and at any time. Overall, any solidification sequences can be used. The solidification strategies can also be identical. However, for the invention, it is advantageous if each material and component area is assigned a separate solidification strategy. Any relative sequences of powder deposition and solidification strategies can be used.Depending on the desired transition between the materials in the product, the powder deposits and solidification strategies can have any relative position to one another. Furthermore, the contours of the powder deposits and the exposure strategies can have any shape. Figures 3 and 4 show straight contours as examples. However, these can be wavy, circular, or interlocked. If, for example, a form fit is to be achieved between the materials 3 and 4 used after solidification without material-to-material mixing, a distance 11 can be set between powder deposits 1 and 2 and a distance 16 between exposure strategies 14 and 15, whereby the center lines of the distances 11 and 16 are congruent and the outer contours of the powder deposits 11 and 12 and of the exposure strategies 14 and 15 have an interlocking dovetail structure in the transition area.However, it is advantageous for the invention if a material-to-material bond is achieved between the materials and the powders 1 and 2 have no distance 12 or a slight overlap 13, wherein the overlap 13 should be between 0 pm and 1 mm, but in particular between 0 pm and 500 pm. Furthermore, it is advantageous to use an overlap 18 of the exposure strategies 14 and 15, wherein it is again advantageous if the center line of the overlap region 18 of the exposure strategies 14 and 15 is congruent with the center line of the overlap region 13, or the discrete transition 12, of the powder deposition, and the overlap 18 has a width between 0 pm and 1 mm, but in particular between 0 pm and 500 pm.

[0044] Referring to Figures 5a and b, a product variant is shown in the context of the application. The product of the manufacturing process according to the invention, consisting of the secondary part 3 with functional surface 4, is shown in an exploded diagram (Fig. 5a). The prosthesis can be integrated implant-supported 20, on a ground abutment tooth 21, or any combination thereof with any number of implants and abutments. As an example, a monolithic primary part 22 above the gum 23 was shown for the abutment 21. Monolithic primary parts, or primary parts manufactured using the method according to the invention, consisting of a structural material 24 and a correspondingly bonded outer layer 25, can also be used on implants. From a cost perspective, conventionally manufactured, monolithic primary parts are advantageous.The inventive product 3 with 4 can also be veneered with a corresponding structure 26. Figure 5b shows the exemplary prosthesis in its inserted form. From the outside, this closely resembles natural teeth 27. The precisely adjusted fit between the inner surfaces 4 of the secondary part 3 and the surfaces 22 and 25 ensures a firm hold of the prosthesis and prevents it from accidentally falling out. The retention forces can be adjusted to allow for targeted, manual removal, e.g., for cleaning.

[0045] List of reference symbols

[0046] 1 : Unsolidified powder of material A (structural material)

[0047] 2: Unsolidified powder of material B (functional material)

[0048] 3: Secondary crown made of solidified material A

[0049] 4: Inner layer of the secondary crown made of solidified material B

[0050] 5: Energy source for melting and solidifying the metal powder

[0051] 6: Construction platform

[0052] 7: Squeegee for applying powder to a material

[0053] 8: Dosing platform for feeding a powder material from below

[0054] 9: Selective powder application mechanism for other powder materials

[0055] 10: Coating system for (optionally selective) surface powder application of different powder materials with powder feed from above

[0056] 11 : Distance between the powder storage positions

[0057] 12: Discrete, immediate transition of the powder deposit positions

[0058] 13: Overlap of powder deposition positions in which several materials are present

[0059] 14: Hardening strategy for material A

[0060] 15: Hardening strategy for material B

[0061] 16: Distance between the consolidation strategies

[0062] 17: Discrete, immediate transition of consolidation strategies

[0063] 18: Overlap of the solidification strategies in which the materials are melted several times

[0064] 19: Further consolidation strategies that differ from consolidation strategies A and B

[0065] 20: Dental implant

[0066] 21 : Ground tooth abutment

[0067] 22: Primary crown on abutment

[0068] 23: Gums

[0069] 24: Primary crown on implant

[0070] 25: Outer layer of the primary crown

[0071] 26: Blindness

[0072] 27: Healthy tooth

Claims

Patent claims 1. A method for producing a first connecting element of a removable dental prosthesis, which is suitable for a sliding connection between a first fitting surface of the first connecting element and a second fitting surface of a second connecting element of the removable dental prosthesis, characterized in that the first connecting element is produced by joining a strength-providing material and a ductile material forming the first fitting surface in an additive multi-material manufacturing process.

2. Method according to claim 1, characterized in that the connection of the materials is made by material bonding or by form bonding or a combination of both types of connection.

3. Method according to claim 1 or 2, characterized in that the additive multi-material manufacturing process is carried out as a powder bed-based melting process with a directed laser beam or a directed electron beam.

4. The method according to claim 3, characterized in that the powder bed-based melting process is carried out with a powder deposition strategy in which powder layers of the two materials are deposited in the region of the joint either at a mutual distance, adjacent to one another, or overlapping one another.

5. The method according to claim 3 or 4, characterized in that the powder bed-based melting process is carried out with a solidification strategy in which the scan patterns of the beams irradiated onto the powder particles of the materials are arranged in the region of the connection either at a mutual distance, adjacent to one another, or overlapping one another.

6. Method according to one of claims 1 to 5, characterized in that the fitting surface of the first connecting element produced by the multi-material production is subtractively or formatively reworked to set a predetermined transition fit with respect to the second connecting element.

7. Method according to one of claims 1 to 6, characterized in that the first connecting element is a secondary part and the second connecting element is a primary part of a removable denture, and / or the first connecting element is a primary part and the second connecting element is a secondary part of a removable denture.

8. Removable dental prosthesis with a first connecting element which is suitable for a connection between a first fitting surface of the first connecting element and a second fitting surface of a second connecting element fastened in the mouth, characterized in that the first connecting element is multi-material manufactured from a strength-providing material and a ductile material connected thereto, forming the first fitting surface, in particular by multi-material manufacturing according to one of claims 1 to 7.

9. Removable dental prosthesis according to claim 8, characterized in that the fitting surfaces are inclined relative to the sliding axis at an angle which is less than or equal to 10 degrees, in particular less than or equal to 6 degrees or in particular equal to zero.

10. Manufactured removable dental prosthesis according to claim 8 or 9, characterized by production using a method according to one of claims 1 to 7.

Images