Method for manufacturing inner crown and outer crown that form dental prosthesis, dental prosthesis, maintenance method for dental prosthesis, inner crown, member for dental prosthesis, and method for manufacturing same

Abstract

Provided is a dental prosthesis comprising: a fixture that is embedded in an alveolar bone; an abutment that is attached to the fixture with a screw member and has an upper part serving as an inner crown; an outer crown that is detachably fitted onto the inner crown of the abutment; and a crown structure that is fixed to the outer crown.

Description

Method for manufacturing inner and outer crowns constituting dental prostheses, dental prostheses, method for maintaining dental prostheses, inner crowns, dental prosthesis components and methods for manufacturing the same

[0001] The present invention relates to a method for manufacturing an inner crown and an outer crown that constitute a dental prosthesis, a dental prosthesis, a maintenance method for a dental prosthesis, an inner crown, a component for a dental prosthesis, and a method for manufacturing the same.

[0002] A dental prosthesis consisting of an inner crown, an outer galvanic crown, and a crown structure (so-called AGC (Auro Galvano Crown)) is known. AGCs have been manufactured by skilled dental technicians through long manual labor.

[0003] Patent Document 1 discloses a method for producing a dental prosthesis by printing a denture base onto an artificial tooth. Patent Document 2 discloses a dental implant comprising a fixture, an abutment, and a prosthetic crown, with the abutment and the prosthetic crown bonded with cement. Patent Document 3 discloses a structure for attaching a keeper to an inner crown. Patent Document 4 discloses an auxiliary retention device for a crown prosthesis.

[0004] Japanese Patent No. 6469865 Japanese Patent Application Laid-Open No. 2016-220722 Japanese Patent No. 4126641 Japanese Patent Application Laid-Open No. 2003-52722

[0005] An object of the present invention is to provide a method for manufacturing an inner crown and an outer crown that constitute a novel dental prosthesis, a dental prosthesis, a maintenance method for a dental prosthesis, an inner crown, a dental prosthesis component, and a method for manufacturing the same.

[0006] The invention as defined in each claim is provided.

[0007] 1 is a schematic vertical cross-sectional view showing an example of an inner crown 10 and an outer crown 20 that constitute a dental prosthesis; FIG. 2 is a schematic vertical cross-sectional view showing another example of an inner crown 10 and an outer crown 20 that constitute a dental prosthesis; FIG. 3 is a schematic vertical cross-sectional view showing yet another example of an inner crown 10 and an outer crown 20 that constitute a dental prosthesis; FIG. 4 is a block diagram showing a manufacturing system for an inner crown 10 and an outer crown 20 according to an embodiment; FIG. 5 is a flowchart showing a manufacturing method for an inner crown 10 and an outer crown 20 according to an embodiment; FIG. 6 is a diagram explaining preparation; FIG. 7 is a diagram explaining the shaping of an inner crown member 10a and an outer crown member 20a using a metal layer deposition 3D printer; FIG. 8 is a diagram explaining the fabrication of an inner crown 10 and an outer crown 20; FIG. 9 is an exploded view of a dental prosthesis; FIG. 10 is a schematic diagram showing a state in which a dental prosthesis is in use; FIG. 11 is a schematic diagram showing a state in which an outer crown 3 has been detached from an inner crown 22; FIG. 12 is a schematic diagram showing a state in which an abutment 2 has been detached from a fixture 1; FIG. 13 is a schematic diagram showing a modified example of an abutment 2; FIG. 14 is a schematic diagram showing an abutment 2 and an outer crown 3 that are removable using a jig 6; 19A , 19B, 19C, 19D, 19E, 19F, 19G, 19H, 19G, 19H, 19I, 19J, 19K ...

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0009] (First embodiment) The first embodiment relates to a method for manufacturing inner and outer crowns that constitute a dental prosthesis. The objective of the first embodiment is to provide a method that allows even non-expert dental technicians to manufacture inner and outer crowns that constitute a dental prosthesis, and to provide a dental prosthesis that can be manufactured in this manner. In the first embodiment, the following solution is provided as an example.

[0010] [1] A method for manufacturing an inner crown constituting a dental prosthesis and an outer crown detachable from the inner crown, comprising: a first step of acquiring three-dimensional CAD data based on intraoral scan data; a second step of using a metal layering three-dimensional printer to set the inner crown opening at the bottom and the outer crown opening at the top, and molding a metal inner crown member that will become the inner crown and a metal outer crown member that will become the outer crown on a single base based on the three-dimensional CAD data; a third step of milling the outside of the inner crown member and the inside of the outer crown member that have been molded on the single base based on the three-dimensional CAD data; and a fourth step of fabricating the inner crown and the outer crown from the inner crown member and the outer crown member, respectively, which includes cutting the inner crown member and the outer crown member from the single base.

[0011] [2] The method according to [1], wherein the inner and outer crown members are made of titanium.

[0012] [3] The method according to [1] or [2], wherein in the second step, the inner and outer crown members are shaped so that no gap is formed between the inner and outer crowns when the outer crown is placed on the inner crown; and in the third step, milling is performed on the outside of the inner crown member and the inside of the outer crown member so that no gap is formed between the inner and outer crowns when the outer crown is placed on the inner crown.

[0013] [4] The method according to [1] or [2], wherein in the second step, the inner and outer crown members are shaped so that a gap is formed between the inner and outer crowns when the outer crown is placed on the inner crown; and in the third step, a milling process is performed on the outside of the inner crown member and the inside of the outer crown member so that a gap is formed between the inner and outer crowns when the outer crown is placed on the inner crown.

[0014] [5] The method according to [4], wherein in the second step, the inner crown member and the outer crown member are shaped so that a gap is formed between at least a part of the upper surface of the inner crown and the outer crown when the outer crown is placed on the inner crown; and in the third step, milling is performed on the outside of the inner crown member and the inside of the outer crown member so that a gap is formed between at least a part of the upper surface of the inner crown and the outer crown when the outer crown is placed on the inner crown.

[0015] [6] The method according to [4], wherein in the second step, the inner and outer crown members are shaped so that a gap is formed between at least a part of the side surface of the inner crown and the outer crown when the outer crown is placed on the inner crown; and in the third step, milling is performed on the outside of the inner crown member and the inside of the outer crown member so that a gap is formed between at least a part of the side surface of the inner crown and the outer crown when the outer crown is placed on the inner crown.

[0016] [7] The method according to [6], wherein in the second step, the inner crown member and the outer crown member are shaped so that the inner crown has a large diameter portion and a small diameter portion, and when the outer crown is placed on the inner crown, at least a part of the large diameter portion of the inner crown comes into contact with the outer crown, and a gap is formed between the small diameter portion of the inner crown and the outer crown; and in the third step, milling is performed on the outside of the inner crown member and the inside of the outer crown member, so that the inner crown has a large diameter portion and a small diameter portion, and when the outer crown is placed on the inner crown, at least a part of the large diameter portion of the inner crown comes into contact with the outer crown, and a gap is formed between the small diameter portion of the inner crown and the outer crown.

[0017] [8] The method according to [1] or [2], wherein in the second step, the metal layered three-dimensional printer is used to set the inner crown opening at the bottom and the outer crown opening at the top, and a first metal support, the inner crown member supported on the single base by the first support, a second metal support, and the outer crown member supported on the single base by the second support are formed; and in the fourth step, the method includes cutting the first support to separate the inner crown member from the single base, and cutting the second support to separate the outer crown member from the single base.

[0018] [9] A dental prosthesis comprising: a titanium inner crown connected to an abutment; and a titanium outer crown removably fitted over the inner crown.

[0019] According to the first embodiment, even if a dental technician is not an experienced dental technician, the inner crown and outer crown that constitute the dental prosthesis can be manufactured.

[0020] The first embodiment will be specifically described below with reference to the drawings.

[0021] First, an example of a dental prosthesis will be described. Fig. 1A is a schematic vertical cross-sectional view showing an example of an inner crown 10 and an outer crown 20 that constitute a dental prosthesis. The dental prosthesis of the present invention can be composed of an inner crown 10 and an outer crown 20, and can be applied to both natural teeth and implants. The outer shapes of the inner crown 10 and the outer crown 20 are, for example, truncated cones.

[0022] The inner crown 10 is fitted over an intraoral abutment (not shown), such as a natural tooth or an implant, and is also called a primary structure. The inner crown 10 is intended to be attached to the abutment using cement or the like, and is not intended to be removed from the abutment. There are no particular limitations on the shape of the inner crown 10, but for example, the vertical cross section is a downward U-shape inclined at an angle of 2 to 6 degrees relative to the vertical direction. The inner diameter A is approximately 2 to 8 mm, and the height B is approximately 4 to 8 mm.

[0023] The outer crown 20 is fitted over the inner crown 10 and is also called a secondary structure. The outer crown 20 is intended to be detachable from the inner crown 10. Being able to detach the outer crown 20 from the inner crown 10 facilitates maintenance of the inner crown 10 and the outer crown 20. There are no particular limitations on the shape of the outer crown 20, but for example, the outer crown 20 may have an inner surface shape that does not leave a gap between it and the inner crown 10. Although not shown in FIG. 1A , the dental prosthesis may be configured to include a tertiary structure that is fitted over the outer crown 20.

[0024] As shown in Fig. 1A, there may be no gap between the inner crown 10 and the outer crown 20, or there may be a gap between them. For example, as shown in Fig. 1B, there may be a gap 15 between (at least a portion of) the upper surface of the inner crown 10 and the outer crown 20. Also, as shown in Fig. 1C, there may be a gap 15 between (at least a portion of) the side surface of the inner crown 10 and the outer crown 20. As a more specific example, the inner crown 10 may have a lower large-diameter portion 11 and an upper small-diameter portion 12, and there may be a gap 15 between the small-diameter portion 12 and the outer crown 20. During use, moisture enters the gap 15, generating surface tension, improving the adhesion between the inner crown 10 and the outer crown 20.

[0025] 2 is a block diagram showing a manufacturing system for an inner crown 10 and an outer crown 20 according to one embodiment. This manufacturing system includes a preparation device 31, a scanner 32, and a terminal device 33. These devices are installed, for example, at the chairside and used by a dentist. The manufacturing system also includes a terminal device 41 and a conversion device 42. These devices are installed, for example, at the laboratory and used by a dental technician. The manufacturing system also includes a terminal device 51, a metal layer 3D printer 52, a milling device 53, and a cutting device 54. These devices are used, for example, by a medical device manufacturer.

[0026] Figure 3 is a flowchart illustrating a method for manufacturing an inner crown 10 and an outer crown 20 according to one embodiment. This figure shows an example in which a natural tooth is used as an abutment. First, a dentist prepares the wearer's natural tooth using a preparation device 31 to form an abutment (Step S1). As shown schematically in Figure 4, the surface of the natural tooth 70 is prepared into a desired shape through preparation, and an abutment 71 is formed according to the inner surface shape and size of the inner crown 10 to be fabricated (see Figures 1A to 1C). Note that this step can be omitted if an implant is used as the abutment.

[0027] Next, the dentist uses the scanner 32 to scan the inside of the oral cavity (step S2). This generates scan data. It can also be said that the scanner 32 generates the scan data. This scan data includes data indicating the shape and size of the abutment 71 in the oral cavity. Since the inside of the oral cavity of the wearer is scanned, an appropriate inner crown 10 and outer crown 20 can be created for each wearer.

[0028] Then, the dentist uses the terminal device 33 to transmit the scan data to the terminal device 41 of the dental technician (step S3). In other words, the terminal device 33 transmits the scan data to the terminal device 41.

[0029] The dental technician receives the scan data transmitted from the dentist's terminal device 33 by using the terminal device 41 (step S11). It can also be said that the terminal device 41 receives the scan data from the terminal device 33.

[0030] The dental technician then uses the conversion device 42 to convert the scan data into 3D CAD data corresponding to the shapes of the inner crown 10 and outer crown 20 to be fabricated (step S12). It can also be said that the conversion device 42 generates the 3D CAD data from the scan data. This 3D CAD data is in a format that can be used by the metal layering 3D printer 52 used by the medical device manufacturer, and includes data indicating the shape of the abutment 71 in the oral cavity and the shapes of the inner crown 10 and outer crown 20 to be fabricated.

[0031] Then, the dental technician uses the terminal device 41 to transmit the three-dimensional CAD data to the terminal device 51 of the medical device manufacturer (step S13). In other words, the terminal device 41 transmits the three-dimensional CAD data to the terminal device 51.

[0032] The medical device manufacturer receives the 3D CAD data transmitted from the dental technician's terminal device 41 via the terminal device 51 (step S21). It can also be said that the terminal device 51 receives the 3D CAD data from the terminal device 41. As a result, 3D CAD data that can be used by the metal layered 3D printer 52 is obtained based on the intraoral scan data.

[0033] Then, based on the 3D CAD data, the medical device manufacturer uses a metal layer printer 52 to simultaneously form the metal inner crown member 10a that will become the inner crown 10 and the metal outer crown member 20a that will become the outer crown 20, for example, by setting the opening of the inner crown 10 at the bottom and the opening of the outer crown 20 at the top (step S22). It can also be said that the metal layer printer 52 simultaneously forms the inner crown member 10a and the outer crown member 20a based on the 3D CAD data. "Simultaneously" here means that the inner crown member 10a and the outer crown member 20a are formed on a single base 80 (plate), as shown in FIG. 5 .

[0034] When manufacturing the inner crown 10 and outer crown 20 as shown in FIG. 1A, the inner crown member 10a and the outer crown member 20a are shaped so that no gap is formed between the inner crown 10 and the outer crown 20 when the outer crown 20 is placed on the inner crown 10.

[0035] When manufacturing the inner crown 10 and outer crown 20 as shown in FIG. 1B or 1C, the inner crown member 10a and the outer crown member 20a are shaped so that a gap 15 is formed between the inner crown 10 and the outer crown 20 when the outer crown 20 is placed on the inner crown 10.

[0036] In particular, when manufacturing the inner crown 10 and outer crown 20 shown in FIG. 1B, the inner crown member 10a and the outer crown member 20a are shaped so that a gap 15 is formed between at least a portion of the upper surface of the inner crown 10 and the outer crown 20 when the outer crown 20 is placed on the inner crown 10.

[0037] On the other hand, when manufacturing the inner crown 10 and outer crown 20 shown in FIG. 1C , the inner crown member 10 a and the outer crown member 20 a are shaped so that a gap 15 is formed between at least a portion of the side surface of the inner crown 10 and the outer crown 20, more specifically, so that at least a portion of the large diameter portion 11 of the inner crown 10 contacts the outer crown 20 and so that a gap 15 is formed between the small diameter portion 12 of the inner crown 10 and the outer crown 20.

[0038] The material for the inner and outer crown members 10a and 20a may be any metal, but titanium is particularly suitable. Titanium has fewer adverse effects on the human body (such as allergies), is harder than other metals such as gold, and is less likely to deform over time. Titanium also has the advantage of being lightweight and inexpensive.

[0039] In step S22, as shown in Fig. 5, in addition to the inner and outer crown member 10a and 20a, columnar metallic supports 10b for the inner and outer crown member 10a and supports 20b for the outer crown member 20a may be formed. That is, the support 10b is formed so that its lower end is fixed to the base 80, and the inner crown member 10a is formed at the upper end of the support 10b (the peripheral edge of the inner crown member 10a is connected to the upper end of the support 10b). In this way, the inner crown member 10a supported on the base 80 by the support 10b is formed. Similarly, the support 20b is formed so that its lower end is fixed to the base 80, and the outer crown member 20a is formed at the upper end of the support 20b (the lower surface (upper surface in Figs. 1A to 1C) of the outer crown member 20a is connected to the upper end of the support 20b). In this way, the outer crown member 20a supported on the base 80 by the support 20b is formed. This makes it easier to remove the inner and outer crown members 10a and 20a from the base 80.

[0040] However, the metal layered three-dimensional printer 52 cannot always accurately form the shapes of the inner and outer crown members 10a and 20a. For example, the outer surface shape of the inner and outer crown members 10a and 20a may not match, resulting in a mismatch between the two and an unintended gap between them.

[0041] Therefore, the medical device manufacturer performs a milling process on the inner and outer crown members 10a and 20a, which are formed on the base 80, using a milling device 53 based on the 3D CAD data (step S23 in FIG. 3). Specifically, the simultaneously formed inner and outer crown members 10a and 20a are set on the base 80 in the milling device 53, and the inner and outer crown members 10a and 20a are milled. The milling targets are the outer surface of the inner crown member 10a and the inner surface of the outer crown member 20a. It is assumed that the inner crown 10 will be bonded to the abutment with cement or the like. Therefore, it is desirable to leave the inner surface of the inner crown 10 rough, as formed by the metal layer 3D printer 52, rather than smoothing it by milling. It can also be said that the milling device 53 mills the inner and outer crown members 10a and 20a based on the 3D CAD data.

[0042] When manufacturing the inner crown 10 and outer crown 20 as shown in FIG. 1A, milling is performed on the outside of the inner crown member 10a and the inside of the outer crown member 20a so that no gap is formed between the inner crown 10 and the outer crown 20 when the outer crown 20 is placed on the inner crown 10.

[0043] When manufacturing the inner crown 10 and outer crown 20 as shown in FIG. 1B or 1C, milling is performed on the outside of the inner crown member 10a and the inside of the outer crown member 20a so that a gap 15 is formed between the inner crown 10 and the outer crown 20 when the outer crown 20 is placed on the inner crown 10.

[0044] In particular, when manufacturing the inner crown 10 and outer crown 20 shown in FIG. 1B, milling is performed on the outside of the inner crown member 10a and the inside of the outer crown member 20a so that a gap 15 is formed between at least a part of the upper surface of the inner crown 10 and the outer crown 20 when the outer crown 20 is placed on the inner crown 10.

[0045] On the other hand, when manufacturing the inner crown 10 and outer crown 20 shown in FIG. 1C , milling is performed on the outside of the inner crown member 10a and the inside of the outer crown member 20a so that a gap 15 is formed between at least a portion of the side surface of the inner crown 10 and the outer crown 20; more specifically, so that at least a portion of the large diameter portion 11 of the inner crown 10 contacts the outer crown 20 and so that a gap 15 is formed between the small diameter portion 12 of the inner crown 10 and the outer crown 20.

[0046] By such milling process, the outer surface of the inner crown member 10a and the inner surface of the outer crown member 20a are appropriately cut, and the shapes of the inner crown member 10a and the outer crown member 20a are adjusted, so that they can be easily attached and detached.

[0047] In this embodiment, the milling process is performed while the inner crown member 10a and the outer crown member 20a are still shaped on the base 80, so cutting can be performed with higher precision than, for example, attaching them to a milling holder with wax and then performing the milling process.

[0048] Next, the medical device manufacturer separates the inner crown member 10a and the outer crown member 20a from the base 80 to prepare the inner crown 10 and the outer crown 20 (Step S24). This process may be performed by cutting the connection between the inner crown member 10a and the support 10b and the connection between the outer crown member 20a and the support 20b to separate the inner crown member 10a and the outer crown member 20a from the base 80, thereby preparing the inner crown 10 and the outer crown 20. Alternatively, this process may be performed in two steps as described below.

[0049] That is, in the first step, the medical device manufacturer uses a cutting device 54 to cut the supports 10b, 20b at any position (for example, near the center) in the state shown in Fig. 5. As a result, the inner crown member 10a and the outer crown member 20a are separated from the base 80, as shown on the left side of Fig. 6. In this state, a portion 10c of the support 10b is connected to the inner crown member 10a, and a portion 20c of the support 20b is connected to the outer crown member 20a.

[0050] Therefore, in the second step, the medical device manufacturer removes the portion 10c of the support 10b from the inner crown member 10a, and removes the portion 20c of the support 20b from the outer crown member 20a, thereby producing the inner crown 10 and the outer crown 20.

[0051] As described above, the use of the metal layered 3D printer 52 and milling device 53 reduces manual work, allowing even those who are not skilled dental technicians to accurately manufacture the inner crown 10 and outer crown 20 in a short time and at low cost. Note that the division of roles between dentists, dental technicians, and medical device manufacturers described above is merely an example. One or more parties (businesses) may perform any required process.

[0052] [Explanation of symbols in Figs. 1 to 6] 10 Inner crown 10a Inner crown member 10b Support 10c Part of support 10b 11 Large diameter portion 12 Small diameter portion 15 Gap 20 Outer crown 20a Outer crown member 20b Support 20c Part of support 20b 31 Preparation device 32 Scanner 33 Terminal device 41 Terminal device 42 Conversion device 51 Terminal device 52 Metal layered three-dimensional printer 53 Milling device 54 Cutting device 70 Natural tooth 71 Abutment 80 Base

[0053] Second Embodiment The second embodiment relates to a dental prosthesis and a maintenance method thereof. The object of the second embodiment is to improve the maintainability of the dental prosthesis. In the second embodiment, the following solution is provided as an example.

[0054] [1] A dental prosthesis comprising: a fixture to be embedded in alveolar bone; an abutment with an inner crown at the top that is attached to the fixture with a screw member; an outer crown that is detachably fitted onto the inner crown of the abutment; and a crown structure that is fixed to the outer crown.

[0055] [2] The dental prosthesis according to [1], wherein the abutment is removable from the fixture.

[0056] [3] The dental prosthesis described in [2], wherein the screw member is exposed when the outer crown is removed from the inner crown, thereby enabling the screw member to be removed and the abutment to be removed from the fixture.

[0057] [4] The dental prosthesis according to any one of [1] to [3], wherein the abutment is inclined relative to the fixture.

[0058] [5] The dental prosthesis according to any one of [1] to [4], wherein a recess is provided on the upper surface of the inner crown, into which a jig for removing the outer crown from the inner crown can be inserted, and the outer crown has a hole through which the jig can be passed, at a position corresponding to the recess when the outer crown is fitted into the inner crown.

[0059] [6] A maintenance method for a dental prosthesis comprising: a fixture embedded in alveolar bone; an abutment attached to the fixture with a screw member and having an inner crown at its upper end; an outer crown detachably fitted to the inner crown of the abutment; and a crown structure fixed to the outer crown, the method comprising: a first step of removing the outer crown from the inner crown; and a second step of removing the abutment from the fixture by unscrewing the screw member.

[0060] [7] The maintenance method described in [6], wherein a recess is provided on the upper surface of the inner crown, into which a jig for removing the outer crown from the inner crown can be inserted, and the outer crown has a hole through which the jig can be passed, at a position corresponding to the recess when the outer crown is fitted into the inner crown, and the first step includes inserting a jig into the recess through the hole in the outer crown, and removing the inner crown from the outer crown using the jig.

[0061] According to the second embodiment, the maintenance of the dental prosthesis is improved.

[0062] The second embodiment will be specifically described below with reference to the drawings.

[0063] Fig. 7 is an exploded view of a dental prosthesis according to one embodiment, and Fig. 8 is a schematic diagram showing the dental prosthesis in use. This dental prosthesis includes a fixture 1 (artificial tooth root), an abutment 2 (connecting part), an outer crown 3, and a crown structure 4.

[0064] The fixture 1 is embedded in the alveolar bone 11 covered with gums (not shown), and is preferably fixed so as not to come off (see FIG. 8 ). As an example, a male screw is provided on the outer surface of the fixture 1. An embedding hole with a female screw provided on the inner surface is formed in the alveolar bone 11. The fixture 1 is embedded in the alveolar bone 11 by screwing the fixture 1 into the embedding hole in the alveolar bone 11. A recess 1a is formed on the upper surface of the fixture 1. A screw hole 1b extending vertically downward from the upper surface of the fixture 1 is provided, and a female screw is formed on the inner surface of the screw hole 1b.

[0065] The abutment 2 has a base 21 for attachment to the fixture 1 and an inner crown 22 (primary structure) provided on the upper part of the base 21. The base 21 is fitted into the recess 1a of the fixture 1. The abutment 2 also has a threaded hole 2a that penetrates vertically from the top surface to the bottom surface, and a female thread is formed on its inner surface. The abutment 2 is attached to the fixture 1 by screwing a screw member 5, which has a male thread on its outer surface, through the threaded hole 2a of the abutment 2 and into the threaded hole 1b of the fixture 1 (see FIG. 8).

[0066] The outer crown 3 (secondary structure) is provided with a recess 3a having a shape corresponding to the inner crown 22 of the abutment 2, and is detachably fitted to the inner crown 22. In this way, one of the features of this embodiment is that the outer crown 3 and the inner crown 22 are detachable. Note that there may be a gap between the outer surface of the inner crown 22 and the inner surface of the outer crown 3, or they may be in close contact with each other without any gap.

[0067] The crown structure 4 (third structure) is placed over the outer crown 3 and fixed thereto using, for example, cement. It is not intended that the crown structure 4 be removed from the outer crown 3.

[0068] It is possible to fix the outer crown 3 to the abutment 2 by using cement or the like so that it does not come off. However, if this is done, since the outer crown 3 cannot be removed, the abutment 2 below it cannot be removed from the fixture 1. This makes maintenance of the abutment 2 and fixture 1 difficult.

[0069] In contrast, in this embodiment, the outer crown 3 (to which the crown structure 4 is fixed) can be removed from the inner crown 22 of the abutment 2 ( FIG. 9 ). When this is done, the screw member 5 passing through the screw hole 2a becomes exposed from the upper surface of the abutment 2. This makes it possible to remove the screw member 5, and the abutment 2 can be removed from the fixture 1 ( FIG. 10 ). Because the fixture 1 is exposed by removing the abutment 2, maintenance of the fixture 1 becomes easier. Furthermore, being able to remove the abutment 2 also makes maintenance of the abutment 2 easier.

[0070] It is desirable to manufacture the abutment 2 for each patient, taking into consideration the shape of the patient's alveolar bone 11, the type of teeth, etc. One possible manufacturing method is to scan the patient's oral cavity with a scanner and use the data to manufacture the abutment with a three-dimensional printer that uses titanium as its raw material. Depending on the patient's wishes, the top of the abutment 2 may be inclined relative to the fixture 1, as shown in Figure 11, for example. Even in this case, the screw hole 2a needs to extend on an extension line of the screw hole 1b of the fixture 1, so that the screw member 5 can be easily inserted and removed.

[0071] Although the outer crown 3 is detachable from the inner crown 22, it must be fitted (joined) with a certain degree of strength to prevent unintentional removal. This may make it difficult to remove the outer crown 3 from the inner crown 22. Therefore, a removal jig may be used to remove the outer crown 3 from the inner crown 22.

[0072] An example of such a configuration is shown in Figure 12. As shown in Figure 12(a), a recess 2b is provided on the upper surface of the inner crown 22. As shown in Figure 12(b), a hole 3b is provided in the outer crown 3, penetrating from its outer surface to its inner surface. The hole 3b is located at a position corresponding to the recess 2b of the inner crown 22 when the outer crown 3 is fitted onto the inner crown 22. The recess 2b of the inner crown 22 and the hole 4b of the outer crown 3 are provided, for example, inside the oral cavity.

[0073] 12(c) shows a front view, a side view, and a top view of the removal jig 6. The removal jig 6 has a tip 61 having a shape that fits into the hole 3b and the recess 2b, and a handle 62 extending from one end thereof.

[0074] To remove the outer crown 3 from the inner crown 22, the tip 61 is passed through the hole 3b of the outer crown 3 and inserted into the recess 2b of the inner crown 22, and the handle 62 is rotated in the axial direction. This causes the tip 61 to push the outer crown 3 upward, thereby easily removing the outer crown 3 from the inner crown 22.

[0075] [Explanation of symbols in Figs. 8 to 12] 1 fixture 1a recess 1b screw hole 2 abutment 21 base 22 inner crown 2a screw hole 3 outer crown 3a recess 4 crown structure 5 screw member 11 alveolar bone

[0076] (Third to Fifth Embodiments) The third to fifth embodiments relate to an inner crown and a method for manufacturing the same, a dental prosthesis, and a component for a dental prosthesis and a method for manufacturing the same. The objective of the third to fifth embodiments is to enable a suitable fit between an inner crown and an outer crown in a dental prosthesis, or to provide a novel technology that differs from the inventions described in the above-mentioned prior art documents. The third to fifth embodiments provide the following solutions as examples.

[0077] [1] An inner crown for a dental prosthesis, comprising: a lower structure; and an upper structure extending upward from the lower structure, wherein the upper structure has a slit extending downward from its upper surface, and in a vertical cross section, the angle between the horizontal plane and the outer surface of the upper structure is larger than the angle between the horizontal plane and the outer surface of the lower structure.

[0078] [2] The inner crown according to [1], wherein the slits allow the upper structure to function as a spring structure.

[0079] [3] The inner crown according to [1] or [2], wherein when an outer crown is fitted onto the inner crown, the upper structure is deformed so as to narrow the slit.

[0080] [4] The inner crown according to any one of [1] to [3], wherein when the outer crown is fitted onto the inner crown, the upper structure is deformed so that the angle between the horizontal plane and the outer surface of the upper structure in a vertical cross section becomes smaller.

[0081] [5] The inner crown according to any one of [1] to [4], wherein the superstructure has a shape in which a vertically extending cylinder is divided by the slits.

[0082] [6] The inner crown according to any one of [1] to [5], wherein the substructure has a truncated cone shape.

[0083] [7] The inner crown according to any one of [1] to [6], wherein the substructure has a screw hole for attachment to an abutment.

[0084] [8] The inner crown according to any one of [1] to [7], wherein the outer surfaces of the substructure and the superstructure are milled.

[0085] [9] A dental prosthesis comprising: an abutment attached to a fixture that is embedded in alveolar bone; an inner crown according to any one of [1] to [8] attached to the abutment; and an outer crown fitted onto the inner crown.

[0086]

[10] The dental prosthesis according to [9], wherein the inner surface of the outer crown is milled.

[0087]

[11] A dental prosthesis component comprising: an abutment portion attached to a fixture that is embedded in the alveolar bone; and an inner crown portion integral with the abutment portion, wherein the inner crown portion comprises: a lower structure; and an upper structure extending upward from the lower structure, wherein the upper structure is provided with a slit extending downward from its upper surface, and in a vertical cross section, the angle between a horizontal plane and the outer surface of the upper structure is larger than the angle between a horizontal plane and the outer surface of the lower structure.

[0088]

[12] A dental prosthesis comprising: a dental prosthesis member according to

[11] ; and an outer crown fitted to an inner crown portion of the dental prosthesis member.

[0089]

[13] A method for manufacturing an inner crown for a dental prosthesis, comprising: a lower structure; and an upper structure extending upward from the lower structure, wherein the upper structure has a slit extending downward from its upper surface, and in a vertical cross section, the angle between a horizontal plane and the outer surface of the upper structure is larger than the angle between a horizontal plane and the outer surface of the lower structure, the manufacturing method comprising: a step of producing an inner crown using a 3D printer; and a step of milling the outer surface of the inner crown.

[0090]

[14] A method for manufacturing a dental prosthesis component, the method comprising: a step of producing, by a 3D printer, a dental prosthesis component comprising: an abutment portion attached to a fixture to be embedded in alveolar bone; and an inner crown portion integrated with the abutment portion, the inner crown portion comprising: a lower structure; and an upper structure extending upward from the lower structure, the upper structure having a slit extending downward from its upper surface, wherein, in a vertical cross section, the angle between a horizontal plane and the outer surface of the upper structure is larger than the angle between a horizontal plane and the outer surface of the lower structure; and a step of milling the outer surface of the inner crown portion.

[0091] The third to fifth embodiments will be specifically described below with reference to the drawings.

[0092] 13 is a schematic diagram showing a state in which a dental prosthesis according to a third embodiment is used. This dental prosthesis includes a fixture 91 (artificial tooth root), an abutment 92 (connecting portion), an inner crown 1, an outer crown 2, and a crown structure 93.

[0093] The fixture 91 is embedded in the alveolar bone 94 covered by the gums (not shown) and is preferably fixed so as not to fall out. An abutment 92 is attached to the fixture 91. An inner crown 1, also called a primary structure, is attached to the abutment 92. An outer crown 2, also called a secondary structure, is fitted onto the inner crown 1. A crown structure 93, also called a tertiary structure, is fitted onto the outer crown 2.

[0094] As an example, the fixture 91 and the abutment 92 are joined by a screw 95. The abutment 92 and the inner crown 1 are connected by welding. The outer crown 2 is removably fitted over the inner crown 1. The crown structure 93 is fitted to the outer crown 2 using cement or the like, and is not intended to be removed from the outer crown 2.

[0095] 14A is a schematic vertical cross-sectional view of the inner crown 1 without the outer crown 2. As shown in the figure, the inner crown 1 includes a substructure 11 and an upper structure 12.

[0096] The outer surface of the lower structure 11 is shaped like a truncated cone, and is inclined so that the diameter increases downward.

[0097] The upper structure 12 extends upward from the lower structure 11. One or more slits 13 extending downward from the top surface are provided in the upper structure 12. The upper structure 12 can also be said to have multiple pillars 14 separated by the slits 13. For ease of understanding, the slits 13 are depicted as being wider in Figure 14A and other figures. The diameter B of the upper end of the upper structure 12 is smaller than the maximum diameter (diameter at the lower end) A of the lower structure 11.

[0098] FIG. 14B is a schematic diagram of the superstructure 12 as viewed from above, and FIG. 14C is a schematic diagram of the superstructure 12 as viewed from diagonally above. The dashed lines in FIG. 14B correspond to FIG. 14A. In this example, the superstructure 12 is a cylinder extending vertically as a whole, divided by three slits 131-133 extending downward from the top surface. In other words, the superstructure 12 is composed of pillars 141-143 whose horizontal cross section is a sector with a central angle of approximately 120 degrees. However, the shapes (thickness, height, width, etc.) of the pillars 141-143 are arbitrary, and a sector shape is not essential. Note that in each figure, the symbols slit 13 and pillar 14 may be used to represent them.

[0099] Returning to Figure 14A, in a vertical cross section when the outer crown 2 is not attached to the inner crown 1, the angle between the horizontal plane and the outer surface of the substructure 11 is defined as α, and the angle between the horizontal plane and the outer surface of the superstructure 12 is defined as β. Here, angle α is an angle formed on the inside of the inner crown 1, and α≦90 degrees. Furthermore, angle β is an angle formed on the inside of the inner crown 1, and β≦90 degrees. When the outer crown 2 is attached to the inner crown 1, α<β. As an example, β is slightly smaller than 90 degrees, and β-α=approximately 2 degrees.

[0100] As shown in Figure 14D, the provision of the slits 13 allows the superstructure 12 to function as a spring structure. That is, when an inward external force indicated by the arrow in Figure 14D(a) is applied, the pillar 14 (particularly its upper part) deforms in the direction narrowing the slit 13, as shown in Figure 14D(b). This reduces the angle β between the horizontal plane and the outer surface of the superstructure 12. When the external force is removed, the pillar 14 returns to its original position. In this way, the superstructure 12 is elastically deformable.

[0101] Figure 15 is a schematic cross-sectional view of the outer crown 2. As shown in Figure 15, a space 21 is formed inside, with an open bottom. The inner and outer surfaces of the outer crown 2 are inclined so that the diameter increases downward. The inclination angle of the inner surface is approximately equal to the angle α (Figure 14A). The maximum diameter C (diameter at the lower end) of the space 21 is approximately equal to the maximum diameter A of the substructure 11 in the inner crown 1 and is larger than the diameter B at the upper end of the superstructure 12. The minimum diameter D of the space 21 (i.e., the diameter at the upper end) is smaller than the diameter B at the upper end of the superstructure 12 in the inner crown 1.

[0102] 16 is a schematic vertical cross-sectional view showing the state in which the outer crown 2 is attached to the inner crown 1. As shown in the figure, the inner crown 1 is fitted into the space 21 inside the outer crown 2. At this time, the superstructure 12 of the inner crown 1 is subjected to an external force from the inner surface of the outer crown 2, and is deformed so as to narrow the slit 13. More specifically, as described in FIG. 14D, the pillar 14 is deformed in the direction narrowing the slit 13, and the angle between the horizontal plane and the outer surface of the superstructure 12 becomes smaller, for example, to an angle β' that is approximately equal to the angle α.

[0103] In the inner crown 1 and outer crown 2 described above, the maximum diameter C of the space 21 in the outer crown 2 is larger than the diameter B of the upper end of the superstructure 12 in the inner crown 1 (C>B), and the diameter of the space 21 gradually narrows toward the top (see FIGS. 14A and 15 ). This facilitates the task of fitting the inner crown 1 into the space 21 in the outer crown 2 from below. Furthermore, the minimum diameter D of the space 21 is smaller than the diameter B of the upper end of the superstructure 12 (D<B). Therefore, the spring structure causes the superstructure 12 to press against the inner surface of the outer crown 2, ensuring that the inner crown 1 and outer crown 2 fit together with an appropriate force. As such, this embodiment allows the inner crown 1 and outer crown 2 to be fitted together appropriately.

[0104] The inner crown 1 and outer crown 2 can be manufactured using, for example, a 3D printer. Their materials may be, for example, titanium. The outer surface of the inner crown 1 may or may not be milled. The inner and / or outer surfaces of the outer crown 2 may also or may not be milled. For example, for hygienic reasons, the outer surface of the inner crown 1 (the substructure 11 and superstructure 12 therein) and the inner surface of the outer crown 2 may be milled to smoothen them. For another example, to firmly bond the inner crown 1 and the outer crown 2, the outer surface of the inner crown 1 (the substructure 11 and superstructure 12 therein) and the inner surface of the outer crown 2 may be left rough without milling. Since the outer surface of the outer crown 2 comes into contact with the mouth, it is desirable to mill it to smoothen it.

[0105] (Fourth Embodiment) In the third embodiment described above, the abutment 92 and the inner crown 1 are separate components. In the fourth embodiment described below, the two are integrated to form a dental prosthesis component. The following will focus on the differences from the third embodiment.

[0106] 17 is a schematic cross-sectional view of a dental prosthesis component according to the fourth embodiment. This dental prosthesis component includes an abutment portion 92' and an inner crown portion 1', which are integrated together. The abutment portion 92' corresponds to the abutment 92 in the third embodiment and is the portion that is embedded in the alveolar bone. The inner crown portion 1' corresponds to the inner crown 1 in the third embodiment and has a similar configuration.

[0107] An outer crown is fitted onto the inner crown portion 1' of this dental prosthesis component to form a dental prosthesis. This embodiment also achieves the same effects as the third embodiment. As with the third embodiment, the dental prosthesis component can be manufactured using a 3D printer, and the outer surface of the inner crown portion 1' may or may not be milled.

[0108] (Fifth Embodiment) In the third embodiment described above, it was assumed that the inner crown 1 is attached to the abutment 92 by welding. In contrast, the third embodiment described next relates to an inner crown 10 that is intended to be attached to the abutment 92 with a screw. Below, a description of the points in common with the third embodiment will be omitted, and differences will be mainly described.

[0109] 18 is a schematic diagram showing a dental prosthesis according to the fifth embodiment in use. This dental prosthesis includes a fixture 91 (artificial tooth root), an abutment 92 (connecting portion), an inner crown 10, an outer crown 20, and a crown structure 93. In this embodiment, the fixture 91, the abutment 92, and the inner crown 10 are joined together by a screw 95.

[0110] Figure 19A is a front view of the inner crown 10 without the outer crown 20. Figure 19B is a view of the inner crown 10 from a direction 90 degrees different from that of Figure 19A. As shown, the inner crown 10 includes a substructure 11' and a superstructure 12'. Figure 19C is a view of the superstructure 12' from above.

[0111] The upper structure 12' has slits 13a', 13b', and 13c' extending downward from the upper surface. As shown in FIGS. 19B and 19C, the upper structure 12' has three pillars 14a' separated by two slits 13a'. As shown in FIG. 19C, the upper structure 12' has three pillars 14b' separated by two slits 13b'. As shown in FIGS. 19A and 19C, a slit 13c' is located between the pillars 13a' and 13b' at both ends. The two slits 13a' and the two slits 13b' have the same width. Meanwhile, the slit 13c' is wider than the slits 13a' and 13b'. However, the present invention is not limited to the above, and the number, shape, and arrangement of the pillars are arbitrary, as are the number and width of the slits.

[0112] By forming the pillars 14a' and 14b' to be sufficiently thin, a screw hole 15' penetrating from the upper structure 12' to the lower structure 11' can be provided at approximately the center of the inner crown 10.

[0113] In this embodiment, too, if the angle between the horizontal plane and the outer surface of the substructure 11' is α and the angle between the horizontal plane and the outer surface of the superstructure 12' is β, then α<β when the outer crown 20 is attached to the inner crown 10. The provision of the slits 13a'-13c' allows the superstructure 12' to function as a spring structure, thereby ensuring a proper fit between the inner crown 10 and the outer crown 20.

[0114] In this embodiment, too, the abutment portion 92' and the inner crown portion 10' may be integrated into one body to form a dental prosthesis component, as shown in FIG.

[0115] [Explanation of symbols in Figs. 13 to 20] 1, 10 Inner crown 1' Inner crown portion 11 Substructure 12 Superstructure 13, 131 to 133 Slit 14, 141 to 143 Post 15 Screw hole 2, 20 Outer crown 21 Space 91 Fixture 92 Abutment 92' Abutment portion 93 Crown structure 94 Alveolar bone 95 Screw

[0116] Based on the above description, a person skilled in the art may be able to conceive additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the individual embodiments described above. For example, inventions that extract only a part of each embodiment or inventions that combine multiple embodiments are naturally envisioned. Various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present invention, which can be derived from the content defined in the claims and their equivalents.

[0117] For example, what is described in this specification as a single device (or component, the same applies hereinafter) (including what is depicted as a single device in the drawings) may be realized by multiple devices. Conversely, what is described in this specification as multiple devices (including what is depicted as multiple devices in the drawings) may be realized by a single device. Alternatively, some or all of the means or functions included in one device may be included in another device.

[0118] Furthermore, not all of the features described in this specification are essential requirements. In particular, features described in this specification but not included in the claims can be considered optional additional features.

[0119] It should be noted that the applicant is merely aware of the inventions disclosed in the documents listed in the "Prior Art Documents" section of this specification, and the present invention does not necessarily aim to solve the problems of the disclosed inventions. The problem that the present invention aims to solve should be determined by taking into consideration the entire specification. For example, if this specification states that a specific configuration achieves a certain effect, it can also be said that the present invention solves a problem that is the reverse of that effect. However, it is not necessarily intended that such a specific configuration be an essential requirement.

Claims

1. An inner crown for a dental prosthesis, comprising: a lower structure; and an upper structure extending upward from the lower structure, wherein the upper structure has a slit extending downward from its upper surface, and in a vertical cross section, the angle between the horizontal plane and the outer surface of the upper structure is greater than the angle between the horizontal plane and the outer surface of the lower structure.

2. The inner crown according to claim 1, wherein the slits allow the upper structure to function as a spring structure.

3. The inner crown according to claim 1 or 2, wherein when an outer crown is fitted onto the inner crown, the upper structure is deformed so as to narrow the slit.

4. An inner cap as described in claim 1 or 2, wherein when an outer cap is fitted onto the inner cap, the upper structure is deformed so that the angle between a horizontal plane and the outer surface of the upper structure in a vertical cross section becomes smaller.

5. The inner crown according to claim 1 or 2, wherein the upper structure has a shape of a vertically extending cylinder divided by the slits.

6. An inner crown according to claim 1 or 2, wherein the substructure is frustoconical in shape.

7. An internal crown as claimed in claim 1 or 2, wherein the substructure is provided with a screw hole for attachment to an abutment.

8. The inner crown according to claim 1 or 2, wherein the outer surface of the substructure and the outer surface of the superstructure are milled.

9. A dental prosthesis comprising: an abutment attached to a fixture that is embedded in alveolar bone; an inner crown according to claim 1 or 2 attached to the abutment; and an outer crown fitted onto the inner crown.

10. The dental prosthesis of claim 9, wherein the inner surface of the outer crown is milled.

11. A dental prosthesis component comprising: an abutment portion attached to a fixture that is embedded in the alveolar bone; and an inner crown portion integral with the abutment portion, wherein the inner crown portion comprises a lower structure and an upper structure extending upward from the lower structure, wherein the upper structure is provided with a slit extending downward from its upper surface, and in a vertical cross section, the angle between a horizontal plane and the outer surface of the upper structure is greater than the angle between the horizontal plane and the outer surface of the lower structure.

12. A dental prosthesis comprising: a dental prosthesis component according to claim 11; and an outer crown fitted onto the inner crown portion of the dental prosthesis component.

13. A method for manufacturing an inner crown for a dental prosthesis, comprising: a lower structure; and a superstructure extending upward from the lower structure, wherein the superstructure has a slit extending downward from its top surface, and in a vertical cross section, the angle between a horizontal plane and an outer surface of the superstructure is greater than the angle between a horizontal plane and the outer surface of the lower structure, the method comprising the steps of: producing an inner crown using a 3D printer; and milling the outer surface of the inner crown.

14. A method for manufacturing a dental prosthesis component, the method comprising: producing, using a 3D printer, a dental prosthesis component comprising: an abutment portion attached to a fixture to be embedded in alveolar bone; and an inner crown portion integral with the abutment portion, the inner crown portion comprising: a lower structure; and a superstructure extending upward from the lower structure, the superstructure having a slit extending downward from its upper surface, wherein in a vertical cross section, an angle between a horizontal plane and an outer surface of the superstructure is greater than the angle between a horizontal plane and the outer surface of the lower structure, the method comprising: milling the outer surface of the inner crown portion.

15. A method for manufacturing an inner crown constituting a dental prosthesis and an outer crown that is detachable from the inner crown, comprising: a first step of acquiring three-dimensional CAD data based on intraoral scan data; a second step of forming a metallic inner crown member that will become the inner crown and a metallic outer crown member that will become the outer crown on a single base using a metal layered three-dimensional printer based on the three-dimensional CAD data; a third step of milling the inner crown member and the outer crown member that have been formed on the single base based on the three-dimensional CAD data; and a fourth step of producing the inner crown and the outer crown from the inner crown member and the outer crown member, respectively, the fourth step including separating the inner crown member and the outer crown member from the single base.

16. The method of claim 15, wherein said inner and outer crown members are made of titanium.

17. A method according to claim 15 or 16, wherein in the second step, the inner crown member and the outer crown member are shaped so that no gap will be formed between the inner crown and the outer crown when the outer crown is placed on the inner crown, and in the third step, a milling process is performed on the inner crown member and the outer crown member so that no gap will be formed between the inner crown and the outer crown when the outer crown is placed on the inner crown.

18. A method according to claim 15 or 16, wherein in the second step, the inner crown member and the outer crown member are shaped so that a gap will be formed between the inner crown and the outer crown when the outer crown is placed on the inner crown, and in the third step, a milling process is performed on the inner crown member and the outer crown member so that a gap will be formed between the inner crown and the outer crown when the outer crown is placed on the inner crown.

19. The method according to claim 18, wherein in the second step, the inner crown member and the outer crown member are shaped so that a gap is formed between at least a portion of the upper surface of the inner crown and the outer crown when the outer crown is placed on the inner crown, and in the third step, a milling process is performed on the inner crown member and the outer crown member so that a gap is formed between at least a portion of the upper surface of the inner crown and the outer crown when the outer crown is placed on the inner crown.

20. The method according to claim 18, wherein in the second step, the inner crown member and the outer crown member are shaped so that a gap is formed between at least a portion of a side surface of the inner crown and the outer crown when the outer crown is placed on the inner crown, and in the third step, a milling process is performed on the inner crown member and the outer crown member so that a gap is formed between at least a portion of a side surface of the inner crown and the outer crown when the outer crown is placed on the inner crown.

21. The method according to claim 20, wherein in the second step, the inner crown member and the outer crown member are shaped so that the inner crown has a large diameter portion and a small diameter portion, and when the outer crown is placed on the inner crown, at least a part of the large diameter portion of the inner crown comes into contact with the outer crown and a gap is formed between the small diameter portion of the inner crown and the outer crown; and in the third step, the inner crown member and the outer crown member are milled so that the inner crown has a large diameter portion and a small diameter portion, and when the outer crown is placed on the inner crown, at least a part of the large diameter portion of the inner crown comes into contact with the outer crown and a gap is formed between the small diameter portion of the inner crown and the outer crown.

22. The method according to claim 15 or 16, wherein the second step uses the metal layered three-dimensional printer to form: a first support made of metal; the inner crown member supported on the single base by the first support; a second support made of metal; and the outer crown member supported on the single base by the second support; and the fourth step includes: separating the inner crown member from the single base by cutting the first support at a predetermined position; creating the inner crown by removing the first support connected to the inner crown member; separating the outer crown member from the single base by cutting the second support at a predetermined position; and creating the outer crown by removing the second support connected to the outer crown member.

23. A dental prosthesis comprising: a titanium inner crown bonded to an abutment; and a titanium outer crown removably fitted over the inner crown.

24. A dental prosthesis comprising: a fixture to be embedded in alveolar bone; an abutment having an inner crown at an upper portion which is attached to the fixture with a screw member; an outer crown which is removably fitted onto the inner crown of the abutment; and a crown structure which is fixed to the outer crown.

25. The dental prosthesis of claim 24, wherein the abutment is removable from the fixture.

26. The dental prosthesis of claim 25, wherein removal of the outer crown from the inner crown exposes the threaded member, thereby allowing the threaded member to be unscrewed and the abutment to be removed from the fixture.

27. A dental prosthesis according to any one of claims 24 to 26, wherein the abutment is inclined relative to the fixture.

28. A dental prosthesis as described in any one of claims 24 to 26, wherein the upper surface of the inner crown is provided with a recess into which a jig for removing the outer crown from the inner crown can be inserted, and the outer crown is provided with a hole through which the jig can be passed at a position corresponding to the recess when the outer crown is fitted onto the inner crown.

29. A maintenance method for a dental prosthesis comprising: a fixture embedded in alveolar bone; an abutment with an inner crown at an upper portion attached to the fixture with a screw member; an outer crown removably fitted onto the inner crown of the abutment; and a crown structure fixed to the outer crown, the method including a first step of removing the outer crown from the inner crown; and a second step of removing the abutment from the fixture by removing the screw member.

30. A maintenance method as described in claim 29, wherein the upper surface of the inner cap is provided with a recess into which a jig for removing the outer cap from the inner cap can be inserted, and the outer cap is provided with a hole through which the jig can be passed, at a position corresponding to the recess when the outer cap is fitted into the inner cap, and the first step includes inserting a jig into the recess through the hole in the outer cap and removing the inner cap from the outer cap using the jig.

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