JP7125684B1 - magnetic denture attachment - Google Patents

Abstract

A welded portion having a high magnetic attractive force, sufficient magnetic shielding properties, and excellent welding strength, and simplification of the process. A cap 1 containing a permanent magnet 2 is made of Cr-based magnetic stainless steel, and a shield plate 3 serving as a lid for an opening of a recess in the cap 1 is made of 18Cr-8Ni stainless steel in a portion other than the outer edge of the magnet and its outer edge. Reference numeral 32 is a non-magnetic portion of 18Cr-8Ni stainless steel modified to be non-magnetic, and a boundary portion between the cap 1 and the shield plate 3 is laser-welded to form a welded portion. The keeper 102 is made of Cr-based soft magnetic stainless steel, and a Cr diffusion layer is formed on the surface to be attracted. [Selection drawing] Fig. 1

Description

TECHNICAL FIELD The present invention relates to a cap-shaped magnetic denture attachment that is used to maintain and fix dentures using magnetic attraction force in the field of dentistry.

In recent years, dentures have been developed by diagnosing the condition of the dentition in the oral cavity using an X-ray image analysis device and 3D shape measurement, designing the dentures with a computer, and printing the digital data with a 3D printer. are beginning to be produced. In other words, dentures are changing from precision cast dentures to digital dentures.
Magnetic denture attachments have been used in precision casting dentures as a tooth-friendly maintenance device, but in the production of digital dentures, the self-attractive force of magnets is used to precisely stabilize the dentures on the abutment teeth. It is expected to be a device that effectively maintains Therefore, an increase in adsorption force is required.

Conventionally, examples of denture attachments using magnetic attraction are shown in FIGS. 5 and 6 disclosed in Patent Document 1. According to FIG. 5, a root plate 62 is embedded in a root portion 61 of a human body, and a keeper 6 is embedded in the root plate 62 in order to wear the denture 50 . The denture 50 consists of a denture attachment 5 provided so as to face the keeper 6, a resin bed 63 enclosing it, and an enameled artificial tooth 64. - 特許庁
As denture attachments, various types of structures such as a cap type and a sandwich type are known, but the present invention is intended to improve the performance of the cap type that can reduce the height of the magnet structure.
A cap-shaped magnetic denture attachment is disclosed in Patent Document 2.

This device is required to be as small as possible and have a strong adsorption force. Furthermore, when a rotational force is generated on the dentures during occlusion and the dentures are tilted due to the rotational force, there is a drawback that the attraction force is rapidly reduced and the dentures are easily dislodged. Therefore, there has been a demand for prevention of reduction in magnetic force when a gap is generated in the attracting surface. Furthermore, it is difficult to shield the magnets which are easily rusted in the magnetic circuit, and improvement of the method has been demanded.
As shown in FIG. 6, the magnetic structure of the denture attachment includes a magnet body 51 made of a cylindrical permanent magnet magnetized in a direction in which the magnetic flux intersects the attracting surface in contact with the keeper 6; It has a recess 56 for housing the body 51 and a box-shaped cap 52 made of soft magnetic material. It also has a shield plate 53 and a shield ring 54 arranged in the opening 560 of the cap 52 so as to enclose the magnet 51 . A combination of the shield plate 53 and the shield ring 54 is called a shield plate 55 . All of the above members are made of corrosion-resistant material.
The magnetic stainless steel keeper on the tooth root side is attracted to the keeper, and the magnet structure and the keeper are integrated to form a magnetic circuit, which greatly enhances the attraction force. Further ideas for improving this adsorption force have been sought.

As another serious problem, in the method of manufacturing the denture attachment described above, the abutting portions of the cap 52 and the outer periphery of the shield ring 54, and the inner periphery of the shield ring 54 and the outer periphery of the shield plate 53 are laser-welded. .
However, when such double welding is performed, a gap is generated at the abutting portion between the cap 52 and the outer circumference of the shield ring 54 due to distortion due to heat during welding. Therefore, it is difficult to laser-weld the butt portion between the inner circumference of the shield ring 54 and the shield plate 36, and there is a disadvantage that weld cracks are likely to occur.

Non-Patent Document 1 discloses a manufacturing method in FIGS. 7A and 7B in order to solve these problems.
As for the manufacturing method, first, a Ni film 74 is provided on the outer circumference of the shield plate 73 in advance. After the shield plate 73 is placed in the opening of the recess of the cap 72 containing the magnet 71 and the lid is closed, the cap 72 and the outer periphery of the shield plate 74 are welded.
During this welding, the Ni film 74 is melted and melted between the cap 72 and the shield plate 73 . This demagnetizes the fusion zone 75 (FIG. 7(B)). As a result, since only one laser welding is required, one welding operation can be omitted, and the associated problems can be solved. However, in addition to the quality problem, the process was complicated and economical.

However, this manufacturing method has the following drawbacks.
At the time of welding, as shown in FIG. 7B, when the Ni film 74 is melted between the cap 72 and the shield plate 73 to form a molten portion 75, the melting depth of the molten portion 75 is must be formed by the thickness of the shield plate 73 as indicated by the solid line D in FIG. 7(B). Thereby, demagnetization between the cap 72 and the shield plate 73 can be achieved.

However, at this time, if the welding depth of the melted portion 75 becomes deep and the magnet body 71 melts as shown by the dashed line E in the figure, the magnet body 71 will be damaged and the magnetic attractive force will decrease. .
On the other hand, in order to avoid this danger, if the welding depth is made shallow as shown by the dotted line F in FIG. 73, a short circuit of magnetic flux will occur, and the magnetic attractive force will decrease.
As described above, it is very difficult to form a non-magnetic region between the cap 72 and the shield plate 74 in the manufacturing method described above. In addition to the quality problem, the process was complicated and economical.

Patent document 2 discloses a manufacturing method in FIG. 8 in order to solve the above problem.
The manufacturing method forms a seal plate 85 comprising a shield plate 83 made of a soft magnetic material and a non-magnetic ring 84 made of a non-magnetic material joined to the outer periphery of the shield plate. After placing the shield plate 85 in the recessed opening of the cap 82 made of a soft magnetic material containing the magnet body 81 and closing the lid, the shield plate 83 (soft magnetic material) and the non-magnetic ring portion 84 (non-magnetic material) are attached. material) and the cap 82 (soft magnetic material) are integrally welded on the surface side to form a welded portion 86 .
As a result, the non-magnetic region can be reliably formed, but the process is complicated and economical.

JP-A-4-227253 JP 2004-154596 A

Summaries of Lectures by the Japan Institute of Metals and Materials (September 29, 1996, p.408)

However, the invention according to Patent Document 2 has an insufficient adsorption force of 600 g when the diameter is 4 mm, and there has been a strong demand for improvement. Also, as a shield method for protecting the magnet, a composite of a non-magnetic ring and a soft magnetic shield plate is formed, and three parts, the non-magnetic ring, the shield plate and the cap, are welded at once.
This manufacturing method had three problems. First, the assembly of the non-magnetic ring and the shield plate is complicated; Since the δ-ferrite phase is generated in the welded portion, the second drawback is that the magnetic shielding is not sufficient, and the third drawback is that the strength of the welded portion is unstable.

SUMMARY OF THE INVENTION The present invention provides a magnetic denture attachment that solves the drawbacks of conventional products, namely, low attractive force, difficulty in welding, and unstable quality.

The present inventors have developed a new idea that the magnetic attraction force can be improved by replacing the conventional magnetic circuit using soft magnetic stainless steel with a Cr—Ni stainless steel magnet for the shield plate portion. I came up with Therefore, the effectiveness of this new concept for the attracting force of magnet-type magnetic attachments was earnestly investigated.

The size of the magnet structure is 4.0 mm in diameter and 1.3 mm in height. The built-in permanent magnet is a NdFeB magnet of 52 MGOe with a diameter of 3.4 mm and a height of 0.9 mm.
Cr-based magnetic stainless steel, which is a conventional soft magnetic stainless steel, was used for the cap, and Cr-based stainless steel having a coercive force of 0 to 50 Oe or less was used for the keeper as a magnetic material.
The shield plate is made of non-magnetic Cr--Ni stainless steel in the outer edge, and has a fibrous structure in the thickness direction other than the outer edge, and is a Cr--Ni-based stainless magnet saturated and magnetized in that direction. . The residual magnetism of the Cr—Ni stainless steel magnet was changed from 0 to 10,000 G, and the effect of the attractive force was investigated. As a result, as shown in FIG. 2, the magnetic attractive force is proportional to the strength of the residual magnetism. I found out. Also, the magnetic attraction force when the magnet structure and the keeper are separated by 0.1 mm showed an improvement compared to the conventional product.

By adopting a composite magnet with a Cr--Ni stainless steel magnet in addition to the NdFeB magnet, it is possible to increase the magnetic energy contained in the magnet structure and improve the magnetic attraction force. As the Cr--Ni stainless steel magnet, a magnet having a saturation magnetization of 8,000 G or more, a coercive force of 100 Oe to 200 Oe, an anisotropic magnetic field of 800 G or more, and a residual magnetism of 6,000 G or more was adopted.
A magnet having a saturation magnetization of 8,000 to 12,000G, an anisotropic magnetic field of 800 to 1,300G, and a residual magnetism of 6,000 to 10,000G is preferred.

Next, we studied the simplification of the manufacturing method.
Regarding the structure of the shield plate, change from two parts consisting of a shield plate made of soft magnetic material and a ring made of non-magnetic material to one part consisting of a Cr-Ni stainless steel magnet and a non-magnetic outer edge. made it
The manufacturing method of the shield plate is as follows. First, a Cr--Ni stainless steel bar is cold-drawn to cause a martensite transformation of 80% or more, a fiber structure is formed in the longitudinal direction, and tension heat treatment is applied. A disc was cut from the wire. The tension heat treatment was performed at a temperature of 450° C. to 570° C. under a tension load of 0 to 30 kg/mm ² . Next, the outer edge (periphery) of the disk in the martensitic transformation state was subjected to high-frequency heating to perform non-magnetic reforming to restore the austenite phase. As a result, a composite magnetic disk was produced in which the outer peripheral portion was made of a non-magnetic material and the portions other than the outer peripheral portion (other than the outer edge portion) were made of a semi-hard magnetic material. Note that the heating of the outer peripheral portion may be performed by laser heating.

The magnetization of this composite magnetic plate disc was carried out by applying a magnetic field of 30,000 Oe or more in the thickness direction together with the NdFeB magnet after welding. As a result, it was possible to obtain a shield plate comprising a ring-shaped outer peripheral portion made of non-magnetic material Cr--Ni stainless steel and a portion other than the disk-shaped outer peripheral portion made of Cr--Ni stainless steel magnets.

The cap was manufactured by punching a disc from a Cr-based stainless steel plate made of a magnetic material and drawing it into a cylindrical shape. It may be used as cold-formed, or may be used after heat treatment.

A magnet structure manufacturing method includes inserting a permanent magnet into a cap made of Cr-based magnetic stainless steel, and placing a shield plate made of Cr--Ni-based stainless steel and a Cr--Ni-based stainless magnet as a lid in the opening of the cap. Press fit to assemble the magnet structure. The interface between the shield plate and the cap is then welded together. The welded boundary portion (weld portion) becomes a weak magnetic portion due to the precipitation of the δ ferrite phase due to the alloy in which the soft magnetic Cr-based stainless steel and the non-magnetic Cr--Ni-based stainless steel are melted. Therefore, by making the width of the non-magnetically modified portion of the outer peripheral portion larger than that of the melted-in portion of the boundary portion, it is possible to complete the magnetic shielding.

Next, the configuration of the keeper, which is the surface to be attracted with respect to the magnet structure, which is the attracting surface, is as follows.
The keeper is made of Cr-based magnetic stainless steel. The keeper attraction surface is required to have oxidation resistance, wear resistance, and soft magnetism. Conventionally, Cr plating has been performed, but at that time, a non-magnetic film is formed, which is one of the causes of reduction in magnetic attractive force. Therefore, in the present invention, the Cr diffusion layer is formed so that the hardness is about Hv400, preferably Hv450 or higher. It is necessary to prevent wear of the surface to be attracted by the keeper and the surface to be attracted by the shield plate by making it hard, especially by making the hardness of the surface to be attracted by the keeper harder than that of the shield plate (martensite structure) to prevent wear of the keeper. .

The present invention achieves a high magnetic attraction force by adopting a Cr—Ni stainless steel magnet for the shield plate. In addition, by using a shield plate consisting of a non-magnetic portion in the outer peripheral portion (outer edge portion) and a magnet in the other portion (other than the outer edge portion), the manufacturing method is simplified, and the welded portion is made of a soft magnetic material for the cap. It is possible to increase the strength of the welded portion by setting only one boundary portion with.

1 is a diagram showing a cross-section of a magnetic denture attachment; FIG. FIG. 4 is a diagram showing the relationship between the residual magnetism of a Cr—Ni stainless steel magnet and the magnetic attraction force. FIG. 10 is a diagram showing a shield plate; FIG. 4 shows a welded portion of the magnet structure; It is a figure explaining the denture in a conventional example. It is a figure which shows the cross section of the dentures attachment in a conventional example. FIG. 10 is a cross-sectional view of a denture attachment in another conventional example; FIG. 10 is a diagram showing a cross section of a denture attachment in another conventional example;

A first embodiment of the present invention is as follows.
The magnetic denture attachment of the present invention is
Provided with a magnetic structure arranged on the denture and a keeper made of a soft magnetic material arranged on the abutment tooth, the attracting surface of the magnetic structure and the attracting surface of the keeper are brought into contact with each other. In a magnetic denture attachment configured so that both are attracted to each other by self-attractive force due to magnetic force,
The magnet structure has a cup-like shape with an opening, the bottom and side portions of which are made of Cr-based magnetic stainless steel with a cap, a permanent magnet housed in the recess of the cap, and a lid on the opening of the cap. consisting of a shield plate and a
The shield plate is made of non-magnetic Cr-Ni stainless steel at the outer edge, has a fibrous structure in the thickness direction except for the outer edge, and is made of a Cr-Ni stainless steel magnet saturated and magnetized in that direction,
and a boundary portion between the endmost portion of the cap side portion and the shield plate is joined by welding, and the welded portion forms a smoothed attraction surface,
The keeper is made of Cr-based soft magnetic stainless steel.

A magnetic denture attachment will be described with reference to FIGS.
The magnetic denture attachment 10 is composed of a magnet structure 101 and a keeper 102 . The magnet structure 101 is arranged on the denture base and exerts a magnetic attraction force. On the other hand, the keeper consists of a soft magnetic material arranged on the abutment. The relationship between the two is as follows: one is provided with an attracting surface on the magnet structure, and the other is provided with an attracting surface on the keeper. are configured to attract and be attracted to each other by.

First, the magnet structure 101 will be described.
A magnet structure 101 is composed of a permanent magnet 2, a cap 1 that accommodates the permanent magnet, and a shield plate 3 that covers the opening of the cap.
The permanent magnet 2 is preferably a rare earth magnet such as an Nd—Fe—B system magnet (NdFeB magnet). For NdFeB magnets, the larger the maximum energy product, the better, and the BHmax should be 35 to 55 MGOe. Sufficient magnetic attractive force cannot be obtained with BHmax less than 35MGOe. As a general-purpose NdFeB magnet, the upper limit is BHmax55MGOe.
The cap 1 is made of Cr-based magnetic stainless steel. Preferably, the coercive force Hc is 50 Oe or less and the Bs is 1.3 T or more. This makes it possible to obtain a sufficient magnetic attractive force.

The shield plate 3 is disc-shaped, has a non-magnetic extension, and is made of a Cr--Ni stainless steel magnet other than the extension. A Cr-Ni stainless steel magnet has a fibrous structure in the thickness direction and is magnetized in that direction. 800 G or more and residual magnetism of 6,000 G or more. In particular, as the residual magnetism increases, the magnetic attractive force increases, so it is important to secure 6,000 G or more. A composite magnet composed of a Cr--Ni stainless steel magnet 3 and a permanent magnet 2 housed in a cap 1 is formed to realize a large magnetic attraction force.
At the same time, the shield plate 3 welds the boundary with the cap to protect the permanent magnet 2 from saliva in the oral cavity and from corrosion. Furthermore, the non-magnetic portion of the shield plate 3 magnetically isolates the composite magnet from the cap, preventing a decrease in the magnetic attraction force.

Here, the manufacturing method of the Cr--Ni stainless magnet is as follows.
First, as shown in FIG. 3, a Cr--Ni stainless steel plate magnet is produced by cold drawing a Cr--Ni stainless steel bar in the austenitic phase to produce martensite transformation of 80% or more. , and sliced from it to produce a shield plate 31 (A) having a fibrous structure in the thickness direction.
Next, the outer peripheral portion of the shield plate 31 in the martensitic transformation state is laser-heated to perform non-magnetic reforming to restore the Cr—Ni stainless steel 32 of the austenite phase. Its width is preferably 0.15 to 0.3 mm, and its thickness is preferably 0.05 to 0.10 mm. As a result, a composite shield plate (B) having a central portion made of a magnetic material and an outer peripheral portion made of a non-magnetic material (non-magnetic portion) is produced.
Magnetization of this composite shield plate is performed by applying a magnetic field of 3,000 to 4,000 Oe in the thickness direction of the disk using an electromagnet to form a permanent magnet. Alternatively, the shield plate and the NdFeB magnet may be overlapped and pulse-magnetized together.
The method of manufacturing the plate magnet is not limited to the above method as long as it is a method that ensures a residual magnetism of 6,000 G or more.

A magnet structure manufacturing method includes inserting a permanent magnet into a cap made of Cr-based magnetic stainless steel, and placing a shield plate made of Cr--Ni-based stainless steel and a Cr--Ni-based stainless magnet as a lid in the opening of the cap. Press fit to assemble the magnet structure. The interface between the shield plate and the cap is then welded together. The welded boundary portion (weld portion) becomes a weak magnetic portion due to the precipitation of the δ ferrite phase due to the alloy in which the soft magnetic Cr-based stainless steel and the non-magnetic Cr--Ni-based stainless steel are melted. Therefore, by making the width of the non-magnetically modified portion of the outer peripheral portion larger than that of the melted-in portion of the boundary portion, it is possible to complete the magnetic shielding.

Next, for the Cr stainless steel cap, a soft magnetic Cr stainless steel plate such as 18Cr stainless steel or 18Cr-2Mo stainless steel is punched into a disk shape, and the disk is drawn to form a cylindrical container. It may be used as it is, or may be used after heat treatment.
For assembly, a cap 1 made of Cr-based magnetic stainless steel is loaded with a permanent magnet 2 made of an NdFeB-based magnet, and then a shield plate 3 serving as a lid for the cap 1 is press-fitted.

As for welding, as shown in FIG. 4, the surface side of the boundary (joint) between the cap 1 made of Cr-based magnetic stainless steel and the ring-shaped Cr--Ni-based stainless steel 32 of the shield plate 3 is laser-welded. The welded portion 33 formed by laser welding has a δ ferrite phase precipitated in an alloy in which Cr-based magnetic stainless steel and Cr--Ni-based stainless steel are dissolved, but does not reach the non-magnetic portion 32, so it is magnetic. Target block can be complete. The size of the welded portion 33 is preferably 0.10 mm in width, 0.08 mm in depth, and a tolerance of 0.01 mm.
The welded portion 33 is then polished to a flat surface.

The keeper 102 is produced by punching a Cr-based soft magnetic stainless steel plate into a disc of a predetermined size. As the keeper, various shapes such as the root keeper are commercially available.

A second embodiment is characterized in that the magnet structure has a cylindrical shape with a diameter of 1.5 to 5 mm and a height of 0.8 to 2 mm. These dimensions are adapted to the shape of the artificial tooth. If it is too large, the denture will crack easily, and if it is too small, sufficient adsorption force cannot be obtained.

As the third embodiment, a Cr--Ni stainless steel magnet having a saturation magnetization of 8,000 G or more, a coercive force of 100 Oe to 200 Oe, an anisotropic magnetic field of 800 G or more, and a residual magnetism of 6,000 G or more was adopted. In particular, by setting the residual magnetism to 6,000 G or more, the magnetic attractive force can be increased.

Furthermore, the fourth embodiment is characterized in that the surface of the keeper to be attracted has a Cr diffusion layer.
As a result, it is possible to improve the oxidation resistance and wear resistance of the keeper and ensure the soft magnetic properties of the keeper. Cr plating is not preferable because it forms a non-magnetic film.
In order to improve wear resistance, the hardness is set to about Hv400, and the hardness of the Cr diffusion layer is preferably Hv450 or higher. By making it hard, it is possible to prevent wear between the keeper on the attracting surface and the shield plate on the attracting surface. At this time, it is necessary to prevent wear of the keeper by making the keeper harder than the shield plate.

[Example 1]
A magnetic denture attachment and a manufacturing method thereof according to the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 3, the magnetic denture attachment 10 of this example has a magnet structure 101 comprising a permanent magnet 2, a cap 1 which is a container for housing the permanent magnet 2, and a concave opening of the cap 1. It consists of a shield plate 3 serving as a lid, and is constructed together with a keeper 102 .

A configuration of the magnet structure 101 will be described.
The permanent magnet 2 is composed of an NdFeB system magnet, and has a BHmax of 52MGOe and an Ms of 1.33T. The size is 3.0 mm in diameter and 0.8 mm in height, and rounded corners are formed.
The cap 1 is made of 18Cr-2Mo stainless steel and has a coercive force Hc of 30 Oe and a saturation magnetic flux density Bs of 1.6T. The size is 3.8 mm in diameter and 1.3 mm in height.

The manufacturing method was as follows: 18Cr-2Mo stainless steel plate with a thickness of 0.3 mm was punched into a disc with a diameter of 6.4 mm. be.

The shield plate 3 is disc-shaped, has a non-magnetic outer edge, and is made of a Cr--Ni stainless steel magnet except for the outer edge. A Cr—Ni stainless steel magnet has a fibrous structure in the thickness direction and is magnetized in that direction. 800G or more and residual magnetism of 6,000G or more. The Cr--Ni stainless steel magnet 3 and the permanent magnet 2 housed in the cap 1 form a composite magnet to realize a large magnetic attractive force.
At the same time, the shield plate 3 welds the boundary with the cap to protect the permanent magnet 2 from saliva in the oral cavity and from corrosion. Furthermore, the non-magnetic portion of the shield plate 3 magnetically isolates the composite magnet from the cap, preventing a decrease in the magnetic attraction force.

A permanent magnet 2 is inserted into the cap 1, then a shield plate 3 serving as a lid is press-fitted into the opening of the recess of the cap 1, and a ring-shaped Cr—Ni magnet consisting of the cap 1 made of Cr-based magnetic stainless steel and the shield plate 3 is assembled. The surface side of the joint with the stainless steel 32 is laser-welded. The welded portion 33 had a width of 0.3 mm and a depth of 0.08 mm.

Next, the cap 1 and keeper 102 are made of 18Cr-2Mo stainless steel with a coercive force of 1G and a saturation magnetic flux density Bs of 1.6T.

Regarding the magnetic denture attachment composed of the Cr-based magnetic stainless steel cap and the Cr—Ni-based stainless steel magnet of the present invention and the conventional denture attachment composed of the soft magnetic stainless steel cap and the seal plate, magnetic attraction A force comparison test was performed. Both have the same size, permanent magnets, etc., and the only difference is whether it is a magnet type or a soft magnetic stainless steel type.
As a result, the conventional denture attachment was 600 gf, while the magnetic denture attachment was 820 gf, which was an improvement of 36% in magnetic attraction force.

[Example 2]
As a result of forming a Cr diffusion layer with a thickness of 5 μm on the keeper 102, a hardness of Hv 500 was obtained.

In the present invention, by adopting a Cr--Ni stainless steel magnet for the shield plate, the magnetic attractive force is improved, and at the same time, the welding of the joint between the cap and the shield plate is simplified, and the stability of quality can be improved. In addition, the structure is simple and economical. This is expected to spread widely.

10: Magnetic denture attachment 101: Magnet structure 102; Keeper 1; Cap 2; Permanent magnet 3; Shield plate 31;
32; outer edge (non-magnetic portion of Cr—Ni stainless steel)
33; welded part

Claims (4)

Provided with a magnetic structure arranged on the denture and a keeper made of a soft magnetic material arranged on the abutment tooth, the attracting surface of the magnetic structure and the attracting surface of the keeper are brought into contact with each other. In a magnetic denture attachment configured so that both are attracted to each other by self-attractive force due to magnetic force,
The magnet structure has a cup-like shape with an opening, the bottom and side portions of which are made of Cr-based magnetic stainless steel with a cap, a permanent magnet housed in the recess of the cap, and a lid on the opening of the cap. consisting of a shield plate and a
The shield plate is made of non-magnetic Cr-Ni stainless steel at the outer edge, has a fibrous structure in the thickness direction except for the outer edge, and is made of a Cr-Ni stainless steel magnet saturated and magnetized in that direction,
and a boundary portion between the endmost portion of the cap side portion and the shield plate is joined by welding, and the welded portion forms a smoothed attraction surface,
A magnetic denture attachment, wherein the keeper is made of Cr-based soft magnetic stainless steel. In claim 1,
A magnetic denture attachment, wherein the magnet structure has a cylindrical shape with a diameter of 1.5 to 5 mm and a height of 0.8 to 2 mm. In claim 1 or 2,
The Cr—Ni stainless steel magnet has a saturation magnetization of 8,000 to 12,000 G, a coercive force of 100 to 200 Oe, an anisotropic magnetic field of 800 G or more, and a residual magnetism of 6,000 to 10,000 G. A magnetic denture attachment. In any one of claims 1 to 3,
A magnetic denture attachment, wherein the surface of the keeper to be attracted has a Cr diffusion layer.

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