JP7125686B1 - magnetic denture attachment - Google Patents

Abstract

A magnetic attachment having a high attraction force of about 800 g and a small thickness of 0.5 mm to 1 mm, and capable of being applied to a bridge using a pulped tooth as an abutment tooth is developed. The shield plate of the magnet structure is composed of a plurality of 18Cr-8Ni stainless steel magnets with a residual magnetism of 6 kG or more, and the cap has a plurality of cup-shaped hole portions and a permanent magnet is inserted into each. , to improve the magnetic attraction force by using a composite magnet. [Selection drawing] Fig. 3

Description

TECHNICAL FIELD The present invention relates to a cap-shaped thin magnetic denture attachment used to maintain and fix dentures by utilizing 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 are expected as maintenance devices for digital dentures.

A current magnetic denture attachment consists of a magnet structure and a keeper, as shown in FIG. Both are attracted by magnetic force via the attracting surface and the attracting surface of both. The combined thickness of the magnet structure and keeper is between 2 mm and 4 mm.
Therefore, when trying to apply the current magnetic denture attachment to a crown bridge with a pulp tooth as an abutment tooth, the thickness must be 1.0 mm or less as shown in Fig. 9. The thickness is as large as 2 to 4 mm, and cannot be used for the treatment of pulped teeth.

In addition, the structure of the magnet structure of the current magnetic denture attachment is, as shown in FIG. forming When the thickness of the part was reduced to 0.5 to 1.0 mm while maintaining this structure, the adsorption force was greatly reduced, and a sufficient holding force could not be secured.

Therefore, in the present invention, the attraction area of the magnet structure is 1.7 to 20 mm ² , which is even smaller than the current product, and the thickness is 0.3 to 1.0 mm. It realizes a thin magnetic denture attachment.

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

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

Conventional magnetic denture attachments have the disadvantage that the attracting force is greatly reduced when the thickness is reduced, as shown in FIG. The present invention overcomes this drawback.

As a result of intensive research by the present inventors on the relationship between the attractive force and the thickness, firstly, when the plate material is replaced with Cr-based magnetic stainless steel and replaced with a Cr--Ni-based stainless magnet, as shown in FIG. It was found that the attractive force increases in proportion to the strength of the residual magnetism of the Cr--Ni stainless steel magnet.

Secondly, the number of magnets installed in the magnet structure was increased from 1 to 4, and the shape and size of the magnet structure and keeper were changed to similar shapes. A magnetic structure was fabricated by arranging and combining four magnets in the horizontal direction, and the relationship between the attractive force and the thickness was investigated.
As a result, as shown in FIG. 3, when the attraction area is constant, the number of magnets is changed to 2, 3, and 4, and the height is 1/2, 1/3, and 1/4, In the case of the Cr—Ni stainless steel magnet plate, the attracting force (gf) hardly decreases even if the thickness is reduced. On the other hand, in the case of the Cr magnetic stainless steel plate, it can be seen that the attracting force is greatly reduced as the thickness is reduced.

The configuration of the thin magnetic denture attachment based on the above findings is as follows.
A magnetic denture attachment consists of a magnetic structure arranged on the denture and a keeper made of a soft magnetic material arranged on the abutment tooth. When they are brought into contact with each other, they are attracted to each other by self-attractive force due to magnetic force.
The magnet structure consists of a cap, permanent magnets, and a shield plate. The cap has a cup-like shape with a plurality of openings, and its bottom and side parts are made of Cr-based magnetic stainless steel. The same number of permanent magnets as the openings of the cap are accommodated in the recesses of the cap, and the same number of the shield plates as the openings of the cap cover the openings of the cap.
The shield plate is a single thin plate made of Cr-Ni stainless steel and having the same shape as the opening. -Made of a composite magnetic material of Ni-based stainless steel magnet, and the boundary between the outermost part of the side of the cap and the shield plate is joined by welding, and the welded part forms a smoothed attraction surface. .
The keeper is made of Cr-based soft magnetic stainless steel.

Here, the magnet structure preferably consists of a thin plate having an attraction area of 1.7 to 20 mm ² and a thickness of 0.3 to 1 mm. Further, the Cr--Ni stainless steel magnet preferably has a saturation magnetization of 13 kG or more, a coercive force of 50 to 200 Oe, and a residual magnetism of 6 kG or more.

TECHNICAL FIELD The present invention relates to a thin magnetic denture attachment that is small, thin, and has a high magnetic attractive force. It is expected that it will be useful for manufacturing removable magnetic crowns and bridges using pulped teeth as abutment teeth.

FIG. 4 is a diagram showing the relationship between the magnetic attraction force and the residual magnetism strength of a Cr—Ni stainless steel magnet; It is a figure which shows the relationship between the magnetic adsorption force and thickness of a current magnet-type denture attachment. It is a figure which shows the influence of the plate material and the number of magnets which act on magnetic attraction force. It is a cross-sectional view of Example 1 (four-piece type) of the present invention. It is a top view (a) and a cross-sectional view (b) of a hole portion of a cap that accommodates four permanent magnets. 1 shows a shield plate (A) of the plate of Example 1 of the present invention and a composite shield plate (B) having a non-magnetically modified portion. FIG. 4 is a view showing the joint state between the endmost portion of the cap side portion and the boundary portion formed of the non-magnetically modified portion of the composite shield plate at the welded portion of the present invention. FIG. 10 illustrates the use of a magnetic denture attachment as a retainer. FIG. 3 is a diagram showing the thinness of a magnetic denture attachment for a magnetic bridge using a pulp tooth as an abutment tooth. 1 is a diagram showing a cross-section of a magnetic denture attachment; FIG.

A first embodiment of the present invention is as follows.
The magnetic denture attachment of the present invention is
It comprises a magnetic structure arranged on the denture and a keeper made of a soft magnetic material arranged on the abutment tooth, and 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 a plurality of openings, the bottom and side portions of which are formed of a cap made of Cr-based magnetic stainless steel and the same number of openings to be accommodated in the recesses of the cap. and the same number of shield plates as the openings covering the openings of the cap,
The shield plate is a single thin plate made of Cr--Ni stainless steel and having the same shape as the opening. made of a composite magnetic material of a Cr-Ni stainless steel magnet,
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 attracting surface,
The keeper is made of Cr-based soft magnetic stainless steel.

The structure and function of the magnetic denture attachment will be explained using the example of four magnets shown in FIGS. 4 and 5. FIG.
A magnetic denture attachment 1 is composed of a magnet structure 10 and a keeper 20 . The magnet structure 10 is arranged on the denture base and exerts a magnetic attraction force. On the other hand, the keeper 20 is made of a soft magnetic material arranged on the abutment tooth. The relation between the two is that one is provided with the attracting surface 130 on the magnet structure 10, and the other is provided with the attracting surface 200 on the keeper 20, and the attracting surface 130 and the attracting surface 200 are in contact with each other. Both are attracted to each other by a magnetic attraction force, and are attracted to each other.

First, the structure of the magnet structure 10 will be described.
The magnet structure 10 is composed of four permanent magnets 11, a cap 12 having four holes 11H for accommodating the permanent magnets, and four shield plates 13 covering the openings of the cap.

The permanent magnet 11 is preferably a rare earth magnet such as an Nd--Fe--B magnet (Nd magnet). For Nd magnets, the larger the maximum energy product, the better, and the BHmax should be 40 to 55 MGOe. Sufficient magnetic attractive force cannot be obtained with BHmax less than 40 MGOe. As a general-purpose Nd magnet, the upper limit is BHmax55MGOe.

The cap 12 is made of Cr-based magnetic stainless steel. The shape includes a circular shape including an ellipse, a rectangular shape such as a square and a rectangular shape, and a rectangular shape having rounded corners. Also, the shape of the hole portion of the cap is the same. In FIG. 4, the shape of the cap 12 and the holding portion 11H is square and has rounded corners.
Its characteristics are a magnetic permeability of about 2000 and a saturation magnetization Bs of about 116 kG. It is preferable to increase the magnetic permeability and saturation magnetism by reducing the amount of Cr and Mo to the extent that the corrosion resistance is not impaired, thereby improving the magnetic attractive force.

The shield plate 13 is a thin Cr--Ni stainless steel plate having the same shape as the hole portion 11H. A Cr--Ni stainless steel magnet is magnetized in the thickness direction, and has a saturation magnetization of 13 kG or more, a coercive force of 50 to 200 Oe, and a residual magnetism of 6 kG or more. In particular, as the residual magnetism increases, the magnetic attractive force increases, so it is important to secure 6 kG or more.
As a result, the Cr--Ni stainless steel magnet forms a composite magnet together with the permanent magnet 11 accommodated in the hole portion 11H of the cap 12, thereby realizing a large magnetic attraction force.
At the same time, the shield plate 13 welds the boundary with the cap to protect the permanent magnet 11 from saliva in the oral cavity and from corrosion. Furthermore, the non-magnetic portion of the shield plate 13 magnetically isolates the composite magnet from the cap, preventing a decrease in the magnetic attraction force.

Here, there are the following methods for manufacturing the stainless magnet depending on the shape of the shield plate 13 .
First, in the case of a disk-shaped shield plate,
a) A shield having a fibrous structure in the thickness direction by cold drawing an austenite phase Cr-Ni stainless steel bar to cause a martensite transformation of 80% or more, and cutting a thin plate from it into a predetermined shape. A plate 131 (FIG. 6(A)) is produced.
(a) A Cr--Ni stainless steel sheet in the austenite phase is subjected to cold working to cause martensite transformation of 50% or more, and then punched into a predetermined shape to produce a shield plate 131 (FIG. 6(A)).
Next, in the case of a rectangular shield plate,
c) Austenite phase Cr--Ni stainless steel thin plate is subjected to cold working to cause martensite transformation of 50% or more, and the shield plate 131 (FIG. 6A) is produced by punching out into a predetermined shape.
In addition, in (a), it may be manufactured by cold drawing into a square deformed bar.

The outer peripheral portion of the shield plate 131 in the martensite transformation state is heated to return to the austenite phase, thereby non-magnetically modifying the Cr--Ni stainless steel. 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 132 (FIG. 6(B)) made of a semi-hard magnetic material in the central portion and a non-magnetic material (non-magnetic portion) in the outer peripheral portion is produced.
After installing the Nd magnet in the cap, cover with this composite shield plate and weld, then 30,000 Oe
With the above magnetic force, the magnetic attachment is magnetized in the thickness direction together with the Nd magnet to form a permanent magnet.

A Cr stainless steel cap is produced by punching a soft magnetic Cr stainless steel plate such as 18Cr stainless steel or 18Cr-2Mo stainless steel into a predetermined shape, and drawing it to produce a cylindrical container. It may be used as it is, or may be used after heat treatment.

The method of manufacturing the magnet structure includes inserting four permanent magnets 11 into a cap 12 made of Cr-based magnetic stainless steel, and inserting Cr--Ni-based stainless steel and Cr--Ni-based stainless steel into the opening of the cap 12 as a lid. A composite shield plate 132 made of a magnet is press-fitted to assemble the magnet structure. Next, the boundary between the composite shield plate 132 and the cap 12 is welded together.

As for welding, as shown in FIG. 6, the surface side of the boundary (joint) between the Cr-based magnetic stainless steel cap 12 and the ring-shaped Cr—Ni-based stainless steel 131b of the composite shield plate 132 is laser-welded. . In the welded portion 133 formed by laser welding, a small amount of δ ferrite phase is 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 131b. So the magnetic isolation can be perfect.
The size of the welded portion 133 is preferably a width of 0.10 mm and a tolerance of 0.01 mm. The welding depth is the same as the thickness of the shield plate, preferably 0.05 mm to 0.10 mm.
The welded portion 133 is then polished to a flat surface.

The keeper 20 is produced by punching a Cr-based soft magnetic stainless steel plate into a predetermined shape and size. In terms of size, the thickness is preferably 0.05 mm to 0.2 mm, and the attraction area is preferably the same as or slightly wider than the attraction surface of the magnet structure, 1.7 to 24 mm ² . As a keeper, it is preferable that the upper surface, which is the surface to be attracted to the magnet structure, be smoothed by polishing so that the unevenness is 1 μm or less. The hardness of the keeper is Hv200 or more when used in a cold-formed state, and Hv200 or less when heat-treated.

As for the size of the magnet structure, it has a thin plate shape with an attraction area of 1.7 to 20 mm ² and a thickness of 0.3 mm to 1 mm. These dimensions and shapes are applicable to bridges using pulped teeth as abutment teeth.

A Cr--Ni stainless steel magnet has a saturation magnetization of 13 kG or more, a coercive force of 50 to 200 Oe, and a residual magnetism of 6 kG or more. In particular, by setting the residual magnetism to 6 kG or more, the magnetic attractive force (adsorption force) can be strengthened.

Furthermore, as a second embodiment, the hardness of the keeper is increased to Hv 250 or higher by cold forming to improve wear resistance.
It was confirmed that the attractive force does not decrease even if the magnetic permeability of the raw material is reduced from 2000 in the heat-treated state to about 200 by hardening the material by cold forming. The reason for this is that the magnetic S pole and the N pole on the attracting surface of the keeper are very close to each other and have a large demagnetizing field coefficient. Presumably because it doesn't change. Alternatively, in the case of the magnet structure of the present invention that employs a Cr--Ni stainless steel magnet, even if the magnetomotive force is increased and the magnetic resistance of the keeper portion is slightly increased, it is considered that the attracting force is not affected.

[Example 1]
A magnetic denture attachment and a manufacturing method thereof according to the present invention will be described with reference to FIGS.
The magnetic denture attachment 1 of this example is composed of a magnet structure 10 and a keeper 20. The magnet structure 10 is a container having permanent magnets 11 and four hole portions 11H for accommodating the four permanent magnets 11. and four shield plates 13 serving as lids for openings of recesses in the cap 12 .

A configuration of the magnet structure 10 will be described.
The permanent magnet 11 is an Nd-based magnet with a BHmax of 52MGOe and an Ms of 1.33T. The size is 1.5 mm in diameter and 0.45 mm in height, and rounded corners are formed.
The cap 12 is made of 18Cr-2Mo stainless steel and has a magnetic permeability of 2000 Oe and a saturation magnetic flux density Bs of 16 kG. The size is rectangular, 6×6 mm, and 0.6 mm high.
The manufacturing method is a container having a 4 × 4 mm square shape and four depressions (hole part 11H) with a depth of 0.4 mm by a cold press method from an 18Cr-2Mo stainless steel plate with a thickness of 0.2 mm. It is.

The shield plate 13 is a rectangular thin plate, the outer edge of which is non-magnetic, and the portions other than the outer edge are made of 18Cr-8Ni stainless steel magnets. The 18Cr-8Ni stainless steel magnet is magnetized in the thickness direction, and has a saturation magnetization of 13 kG or more, a coercive force of 50 to 200 Oe, and a residual magnetism of 6 kG or more.

The 18Cr-8Ni stainless steel magnet forms a composite magnet with the permanent magnet 11 housed in the cap 1 to achieve a large magnetic attractive force.

At the same time, the four shield plates 13 are welded at their boundaries with the cap 12 to protect the permanent magnets 11 from saliva in the oral cavity and corrosion. Furthermore, the non-magnetic portion 131b of the shield plate 13 magnetically isolates the composite magnet from the cap 12, thereby preventing a decrease in the magnetic attraction force.

Four permanent magnets 11 are inserted into the cap 12, then four shield plates 13 serving as lids are press-fitted into the openings of the recesses of the cap 1, and the cap 12 made of Cr-based magnetic stainless steel and the four shield plates are assembled. The surface side of the joint with the 18Cr-8Ni stainless steel 131b of 13 is laser-welded. The welded portion 133 had a width of 0.15 mm and a depth of 0.05 mm.

The cap 12 is made of 18Cr-2Mo stainless steel and has a magnetic permeability of 2000 and a saturation magnetic flux density Bs of 16 kG. The keeper 20 was also made of 18Cr-2Mo stainless steel with a magnetic permeability of 1000 and a hardness of Hv230.

The magnetic denture attachment of Example 1, which is composed of a Cr-based magnetic stainless steel cap 12 and 18Cr-8Ni-based stainless magnets, is compared with a conventional denture attachment composed of a soft magnetic stainless steel cap and a seal plate. . Assuming that the keepers were the same, a comparison test of the adsorption force was carried out. 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, compared to the conventional denture attachment of 600 gf, the magnetic denture attachment was 820 gf, which was an improvement of 36% in attracting force.

[Example 2]
In Example 1, the keeper 20 has a hardness of Hv 270, a thickness of 0.10 mm, an attraction area of 16 mm ² which is the same as the attraction surface of the magnet structure, and the upper surface, which is the attraction surface of the magnet structure, smoothed by polishing. Therefore, the unevenness is set to 1 μm or less.
As a result, an attractive force of 820 g, which is the same as that of the magnetic denture attachment of Example 1, was obtained.

The present invention employs a Cr-Ni stainless steel magnet for the shield plate and employs a plurality of magnets to improve the attractive force to 600 g or more and to reduce the thickness of the magnetic denture attachment to 1 mm or less. It can be applied to bridges using pulped teeth as abutment teeth, and is expected to be widely used.

1; Magnetic denture attachment 10; Magnet structure 11; Permanent magnet 11H; Hole part (permanent magnet insertion part)
12; cap 13; shield plate (composite magnetic material)
130; Attraction surface 131; Shield plate 131a; Other than outer edge/central part made of semi-hard magnetic material (magnetic Cr--Ni stainless steel)
131b; Outer edge/ring part made of non-magnetic material (non-magnetic Cr--Ni stainless steel)
132; composite shield plate 20; keeper 200; surface to be attracted 4; magnetic bridge 41; magnetic attachment 42;

Claims (4)

It comprises a magnet structure arranged on the denture and a keeper made of a soft magnetic material arranged on the abutment tooth, and the attracting surface of the magnet 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 a plurality of openings, the bottom and side portions of which are formed of a cap made of Cr-based magnetic stainless steel and the same number of openings to be accommodated in the recesses of the cap. and the same number of shield plates as the openings covering the openings of the cap,
The shield plate is a single thin plate made of Cr--Ni stainless steel and having the same shape as the opening. made of a composite magnetic material of a Cr-Ni stainless steel magnet,
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 attracting surface,
A magnetic denture attachment, wherein the keeper is made of Cr-based soft magnetic stainless steel. In claim 1,
A thin magnetic denture attachment, wherein the magnet structure is in the form of a thin plate having an attraction area of 1.7 mm ² to 20 mm ² and a thickness of 0.3 mm to 1 mm. In claim 1 or 2,
A magnetic denture attachment, wherein the Cr--Ni stainless steel magnet has a saturation magnetization of 13 kG or more, a coercive force of 50 to 200 Oe, and a residual magnetism of 6 kG or more. In any one of claims 1 to 3,
A magnetic denture attachment, wherein the keeper has a thickness of 0.05 mm to 0.2 mm, an attraction area of 1.7 mm ² to 24 mm ² , and a hardness Hv of 250 or more on the surface to be attracted.

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