JP2018051116A - Dental magnetic attachment keeper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dental magnetic attachment keeper having excellent corrosion resistance and improved adhesiveness and abrasion resistance.SOLUTION: The dental magnetic attachment keeper that is installed at a root cap implanted in a dental root for holding an artificial tooth by magnetic attraction force of a permanent magnet, includes: a plate-like body part composed of corrosion-resistant soft magnetic ferritic stainless steel; and a surface part formed at least at a lateral face of the body part and composed of austenitic stainless steel with the thickness of 10-120 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a keeper for a dental magnetic attachment that holds a denture using a magnetic attraction force by a permanent magnet.

  Dentures using dental magnetic attachments can be attached to and removed from the root using the magnetic attraction of permanent magnets, and are easy to handle and hygienic. Therefore, the number of application examples is rapidly increasing in place of the conventional mechanical fixing means. As shown in FIG. 1, a dental magnetic attachment includes a magnetic attachment magnet structure 1 (hereinafter simply referred to as a magnet structure 1) and a disc for holding a denture by the magnetic attraction force of the magnet structure 1. A magnetic attachment keeper 2 (hereinafter simply referred to as a keeper 2) is used, with the magnet structure 1 fixed to a denture and the keeper 2 fixed to a root face plate 3 embedded in a root 4.

  Japanese Patent Laid-Open No. 9-253096 (Patent Document 1) is a magnetic attachment keeper made of a magnetic material, and has an oxide, carbide, nitride, carbonitride of at least one element of Group 4 and Al on the surface. Keeper with excellent corrosion resistance having a coating layer (for example, TiN layer, (Ti, Al) N layer) made of one or more selected from oxycarbonitrides It is described that the layer can be formed by an ion plating method, a plasma CVD method or the like, and is excellent in adhesion to the base material of the keeper and wear resistance.

  However, a magnetic attachment using a keeper having such a coating layer may crack in the TiN layer when it is repeatedly bitten by long-term use, and it does not necessarily have sufficient adhesion and wear resistance. I wasn't doing it. Therefore, it is desired to develop a keeper for a magnetic attachment that has excellent corrosion resistance and improved adhesion and wear resistance.

Japanese Patent Laid-Open No. 9-253096

  Accordingly, an object of the present invention is to provide a keeper for dental magnetic attachment that has excellent corrosion resistance and improved adhesion and wear resistance.

  As a result of earnest research in view of the above object, the present inventors have formed a surface layer portion of austenitic stainless steel having excellent corrosion resistance and wear resistance by dissolving nitrogen on the surface of a plate made of ferritic stainless steel. The present inventors have found that the surface layer portion has excellent adhesion because it is integrated with a main body portion made of ferritic stainless steel, and have arrived at the present invention.

That is, the keeper for dental magnetic attachment of the present invention is a keeper that is installed on a root face plate embedded in a tooth root, and holds a denture by a magnetic attractive force of a permanent magnet,
It has a plate-like main body portion made of corrosion-resistant soft magnetic ferritic stainless steel, and a surface layer portion made of austenitic stainless steel having a thickness of 10 to 120 μm formed on at least a side surface of the main body portion. .

  You may have a surface layer part of thickness 0-50 micrometers in the main surface of the said main-body part.

  The main surface of the main body may not have a surface layer.

  The surface layer portion preferably comprises a nitrogen solid solution phase.

  The nitrogen content in the surface layer is preferably 0.5 to 4.5% by mass.

  The keeper of the present invention preferably has a Ni content of 0.2% by mass or less.

  The keeper of the present invention preferably has a Cr content of 17 to 32% by mass.

  The keeper for dental magnetic attachment of the present invention has excellent corrosion resistance and has a surface layer portion having excellent adhesion and wear resistance, and can be used without replacement for a long period of time. Can be reduced.

It is a schematic cross section which shows the state which mounted | wore the keeper installed in the root face plate embed | buried under the root with the denture which has a magnetic attachment magnet structure. It is a schematic cross section which shows an example of a magnetic attachment. It is a schematic cross section which shows the example of the keeper for magnetic attachments of this invention. 2 is an optical micrograph showing a cross section of the magnetic attachment keeper of the present invention obtained in Example 1. FIG. 4 is an optical micrograph showing a cross section of the magnetic attachment keeper of the present invention obtained in Example 2. FIG. 4 is an optical micrograph showing a cross section of the magnetic attachment keeper of the present invention obtained in Example 3. FIG. It is a schematic diagram which shows the apparatus for performing the occlusion test of the keeper for magnetic attachments of this invention.

[1] Magnetic attachment
(1) Overall structure As shown in FIG. 1, the dental magnetic attachment is embedded in the magnetic attachment magnet structure 1 (hereinafter simply referred to as magnet structure 1) embedded in the denture base 6, and embedded in the tooth root 4 part. A plate-like magnetic attachment keeper 2 (hereinafter simply referred to as a keeper 2) disposed on the upper surface of the root surface plate 3 to be held, and dentures are held by a magnetic attractive force between the magnet structure 1 and the keeper 2. FIG. 1 shows an example in which a root face plate 3 is embedded in a tooth root 4. However, if the root root 4 is lost, a root face plate may be attached to an artificial tooth root by an implant, and the present invention includes such a case.

  The magnet structure 1 has, for example, a cylindrical outer shape, and is adhesively fixed to the bottom of a resin-made denture base 6 on which artificial teeth 5 are fixed. The keeper 2 is made of a disk-shaped magnetic material, and the remaining roots For example, it is fixed on the root face plate 3 embedded in 4 by a casting method. A magnetic attraction force acts between the magnet structure 1 and the keeper 2 by the permanent magnet 102 disposed inside the magnet structure 1, and the denture is attracted and fixed to the tooth root 4 side. On the other hand, the denture can be removed by applying a force greater than the magnetic attractive force. The root face plate 3 placed on the tooth root 4 is made of a corrosion-resistant nonmagnetic material such as a gold alloy and has a function of covering and protecting the tooth root 4 part. The keeper 2 needs to have good soft magnetic properties and high corrosion resistance in order to generate a required magnetic attractive force with the magnet structure 1.

(2) Magnet structure As shown in FIG. 2, the magnet structure 1 includes a soft magnetic stainless steel cup yoke 101 and a soft magnetic stainless steel disk yoke 103 and a nonmagnetic metal shield ring as shown in FIG. 104 is arranged concentrically, and has a structure in which the permanent magnet 102 is sealed by welding the entire circumference between the disk yoke 103 and the shield ring 104 and between the shield ring 104 and the cup type yoke 101. Since the cup type yoke 101 and the disk yoke 103 are made of soft magnetic stainless steel and the shield ring 104 is made of a nonmagnetic metal, if the permanent magnet 102 is magnetized in the axial direction (direction perpendicular to the surface of the disk yoke 103), the magnetic field lines Passes through the cup-shaped yoke 101, bypasses the shield ring 104, and enters the disk yoke 103. Since the magnetic flux generated by the permanent magnet 102 is distributed in the space on the disk yoke 103 side of the magnet structure 1 (between the cup-type yoke 101 and the disk yoke 103), when the magnetic keeper 2 is brought closer, the keeper 2 is sucked to the disk yoke 103 side.

  The magnet structure 1 is preferably made of stainless steel that does not substantially contain Ni, and is particularly preferably made of corrosion-resistant soft magnetic ferritic stainless steel (SUS447J1, SUSXM27, SUS444, etc.). The Cr content of the ferritic stainless steel is preferably 17 to 32% by mass, more preferably 24 to 32% by mass.

  The outer shape of the magnet structure 1 is not limited to a cylindrical shape, and may be an ellipse or a polygon such as a quadrangle. In this case, the shape of the permanent magnet 2 may be changed according to the outer shape of the magnet structure 1 as necessary.

  As the permanent magnet 102, it is preferable to use a neodymium magnet having a residual magnetic flux density Br larger than that of other permanent magnets and capable of obtaining a larger attractive force. Since the residual magnetic flux density Br of the neodymium magnet needs to saturate the magnetic circuit, it is preferably 1.3 T or more, and more preferably 1.35 T or more. The permanent magnet 2 is magnetized after being incorporated into the magnet structure.

(3) Keeper As shown in FIG. 2, the keeper 2 of the present invention has a double structure comprising a main body portion 21 and a surface layer portion 22 having a thickness of 10 to 120 μm formed on the surface of the main body portion 21. Have. The main body 21 is made of corrosion-resistant soft magnetic ferritic stainless steel, and the surface layer 22 is made of austenitic stainless steel. The keeper 2 having such a configuration can be manufactured by dissolving nitrogen in the surface layer portion of a plate made of ferritic stainless steel. The nitrogen content of the surface layer portion 22 varies depending on the Cr content of the stainless steel, but is preferably 0.5 to 4.5% by mass.

  Ferritic stainless steels such as SUSXM27 (26 wt% Cr, 1 wt% Mo and the balance Fe), SUS447J1 (29 wt% Cr, 2 wt% Mo and the balance Fe) used as a keeper for dental magnetic attachment Nitrogen is dissolved at a temperature of 1100 ° C or higher, and the α phase of the body-centered cubic lattice structure is transformed into the γ phase of the face-centered cubic lattice structure. Nitrogen solid solution γ phase (nitrogen content: about 0.5 to 4.5 mass%) has a Vickers hardness of about 350 HV, which is 1.5 times the hardness of the α phase (ferrite phase) Vickers hardness (about 200 HV). Therefore, when the nitrogen solid solution γ phase is formed on the surface layer portion of the main body portion made of α phase (ferrite phase), the surface layer portion of the γ phase is Although it is elastically deformed with the main body, plastic deformation hardly occurs. Therefore, the keeper formed by forming the nitrogen solid solution phase in the surface layer in this way is excellent in corrosion resistance and wear resistance, is strong against plastic deformation due to stress, and can keep its surface in good condition.

  The Cr content of the corrosion-resistant soft magnetic ferritic stainless steel is preferably 17 to 32% by mass, more preferably 24 to 32% by mass. The Ni content of the ferritic stainless steel is preferably 0.2% by mass or less, and more preferably 0.1% by mass or less. It is preferable that the ferritic stainless steel does not substantially contain Ni. As the ferritic stainless steel, SUS447J1, SUSXM27, SUS444 or the like is preferably used.

  The outer shape of the keeper 2 is not limited to a circle (disk shape), and may be an ellipse or a polygon such as a quadrangle. The outer shape of the keeper 2 is preferably set according to the outer shape of the magnet structure 1.

  As shown in FIG. 3 (a), the keeper 2 has a structure in which the surface layer portion 22 is formed almost uniformly on all surfaces of the main body portion 21, that is, the side surface 21a and the main surface (surface orthogonal to the axial direction) 21b. Alternatively, as shown in FIG. 3 (b), the surface layer portion 22a formed on the side surface 21a of the main body portion 21 may be thicker than the surface layer portion 22b formed on the main surface 21b. When the magnet structure 1 and the keeper 2 are in contact with each other, the stress applied to the rim of the keeper 2 facing the edge of the magnet structure 1 is large, so that the surface layer 22 formed especially on the rim is thick. Is preferred. The thickness of the surface layer portion 22a formed on the side surface 21a of the main body portion 21 is preferably 20 μm or more thicker than the surface layer portion 22b formed on the main surface 21b. Further, as shown in FIG. 3 (c), the surface layer portion 22 may be formed only on the side surface 21a of the main body portion 21, and the surface layer portion 22 may not be formed on the main surface 21b. Also in this case, it is preferable that the surface layer portion 22 of the side surface 21a is formed thick. The surface layer 22 is formed on the side surface 21a of the main body 21 and the surface of the main surface 21b facing the magnet structure 1, and the surface 21b of the main surface 21b is opposite to the side facing the magnet structure 1. A configuration (not shown) in which the surface layer portion 22 is not formed on the surface (the side fixed to the root plate 3) may be employed. The surface layer portion 22 formed on the side surface 21a of the main body portion 21 preferably has a thickness of 10 to 120 μm, and the surface layer portion 22 formed on the main surface 21b preferably has a thickness of 0 to 50 μm.

(Nitrogen solution treatment)
The keeper 2 can be produced by subjecting a corrosion-resistant soft magnetic ferritic stainless steel plate (for example, a disc) to a nitrogen solid solution treatment to form a nitrogen solid solution phase on the surface layer portion and austenitize it. The nitrogen solid solution treatment is performed by heat-treating ferritic stainless steel in a nitrogen atmosphere (50 kPa or more) and at 1150 to 1250 ° C., for example, in a vacuum heating apparatus. The inside of the vacuum heating device is preferably a nitrogen atmosphere at about atmospheric pressure, and a nitrogen atmosphere of about 80 to 120 kPa is preferable. In order to prevent the formation of oxides, it is preferable that the nitrogen gas used does not contain oxygen or water. When the temperature of the heat treatment is lower than 1150 ° C, it is difficult to sufficiently dissolve nitrogen, and when it is higher than 1250 ° C, it is difficult to control the nitrogen solid solution rate, and the thickness of the surface layer portion 22 (nitrogen solid solution) It becomes difficult to keep the depth of molten austenitic stainless steel constant. Nitrogen solute austenitic stainless steel needs to contain enough nitrogen to sufficiently austenitize the ferrite phase. Preferably there is. The lower limit of the nitrogen content is more preferably 0.5% by mass.

  Nitrogen solid solution treatment includes (a) a method in which ferritic stainless steel is previously installed in the heating chamber of the furnace, and (b) a method in which ferritic stainless steel is inserted into the heating chamber of the furnace after reaching a predetermined temperature. There is no problem. In the case of the method of heating after pre-installing stainless steel, the heating rate should be about 5 to 20 ° C / min so that the ferritic stainless steel placed in the heating chamber is heated and heated uniformly. preferable. Nitrogen gas may be charged into the furnace from the start of heating, or may be charged after reaching a predetermined temperature.

  The time for the heat treatment (holding time at the maximum temperature) is appropriately adjusted depending on how deep the ferritic stainless steel is austenitized by nitrogen solid solution treatment. For example, austenitization to a depth of about 100 μm can be performed by performing a heat treatment for about 60 minutes under a nitrogen atmosphere at atmospheric pressure and 1200 ° C.

  As shown in FIG. 3 (c), the keeper 2 in which the surface layer portion 22 is formed only on the side surface 21a of the main body portion 21 is subjected to a nitrogen solid solution treatment on a round bar material made of ferritic stainless steel, so that a constant amount is obtained from the surface. It can be obtained by austenizing the part up to the depth, cutting it into a circle and cutting out the disc.

  Further, as shown in FIG. 3 (b), the keeper 2 configured such that the surface layer portion 22a formed on the side surface 21a of the main body portion 21 is thicker than the surface layer portion 22b formed on the main surface 21b After producing the keeper 2 (see FIG. 3 (c)) in which the surface layer portion 22 is formed only on the side surface 21a of the portion 21, a second nitrogen solid solution treatment is performed to obtain a certain depth from the surface. It can be obtained by austenitizing the part.

  In order to maintain the structure of the austenite phase formed by the nitrogen solid solution treatment even at room temperature, the high-temperature stainless steel after the nitrogen solid solution treatment is rapidly cooled. When the stainless steel after the nitrogen solid solution treatment is gradually cooled, the structure of the austenite phase produced is transformed into a structure in which the ferrite phase or a mixture of the ferrite phase and Cr nitride is mixed. As a method of rapidly cooling stainless steel, a cooling unit is installed in the heating device, the material after the nitrogen solid solution treatment is moved to this cooling unit, and a cooling gas such as nitrogen gas or a rare gas is blown into the cooling unit for air cooling. A method of cooling the cooling unit with water is exemplified.

  Prior to the nitrogen solid solution treatment, it is desirable to treat the ferritic stainless steel material in a hydrogen gas atmosphere at 700 ° C. or higher and below the nitrogen solid solution treatment temperature and atmospheric pressure to remove oxides on the surface. If there are oxides or the like on the surface of the material, they serve as a barrier for penetration of nitrogen gas, and the speed of the nitrogen solid solution treatment decreases, and the depth of the nitrogen solid solution treatment may not be uniform.

  When the preheating treatment is performed at the solid solution treatment temperature for 1 to 3 hours before the nitrogen solid solution treatment, the material grows and an austenite phase with a uniform thickness can be formed. Since the preheating treatment time depends on the size of the crystal grains of the material, it may be set according to the material.

  FIG. 4 shows a photograph of the cross section of the keeper 2 obtained by the method in which nitrogen solid solution treatment is performed and the portion from the surface to a certain depth is austenitized, and observed with an optical microscope. The etching treatment was performed by immersing the sample as a positive electrode in a saturated oxalic acid aqueous solution at room temperature and applying a voltage of 1 to 1.2 V for 10 to 15 seconds. In the keeper 2 shown in FIG. 4, the upper part is an adsorption surface to the magnet structure 1, and the left side is a side surface. The lower part is a surface not subjected to nitrogen solid solution treatment. As is clear from FIG. 4, the boundary between the main body portion 21 made of ferritic stainless steel and the surface layer portion 22 made of austenitic stainless steel is not actually a straight line but is a curved line that is somewhat complicated. Accordingly, the thickness of the surface layer part 22 is drawn from 10 straight lines in the depth direction from the surface, and in each straight line part, the length L1 to the point intersecting the main body part 21 of the ferritic stainless steel from the surface L10 is measured and calculated as an average value thereof.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1
A SUSXM27 round bar (diameter: 4.0 mm) was cut into a circle of O.9 mm, polished on both sides with # 2000 abrasive grains to a thickness of O.8 mm, and then mirror polished by barrel polishing To make a disk-shaped plate. This disk was kept in nitrogen at 1200 ° C. and 1 atm for 20 minutes, and subjected to nitrogen solid solution treatment to produce a disk-shaped keeper. FIG. 4 shows a photograph obtained by etching a cross section of the obtained keeper and observing with an optical microscope. When the nitrogen content of the cross-section of the obtained keeper was measured using EPMA JXA-8900 manufactured by JEOL, as shown in Fig. 3 (a), nitrogen was removed from the surface to an average depth of 20 μm. A solid solution γ phase (surface layer portion) was formed. The nitrogen content of the surface layer portion was 3.5% by mass, and the surface hardness (Vickers hardness, load 50 g) was 350 HV.

  The durability of the obtained keeper was evaluated by an occlusion test with a hyper slim magnet structure 4013 (manufactured by NEOMAX Engineering Co., Ltd.). As shown in FIG. 7, the occlusal test apparatus 200 for performing the occlusion test is provided with a lower sample stage 201 for attaching the magnet structure 1 and a keeper 2 disposed to face the lower sample stage 201. An upper sample stage 202, a lower plate 203 for holding the lower sample stage 201, an upper plate 204 for holding the upper sample stage 202, a shaft 205 fixed to the upper plate 204, A bearing 206 provided on the lower plate 203 to hold the shaft 205 slidably, and the upper plate 204 is pushed down at a constant pressure toward the lower plate 203 to obtain the magnet structure 1 and the keeper 2 as desired. And a spring 208 for pushing up the upper plate 204 upward when the pressure of the pressure bar 207 is released.

  A keeper and a hyper slim magnet structure 4013 were attached to the occlusion test apparatus 200, and an occlusion test was performed by repeatedly applying a load of 30 kg at a cycle of 2 seconds / time. As a result, surface roughness was observed in the magnet structure after 1 million tests, but surface roughness and deformation were not observed in the keeper.

Example 2
A round bar (diameter 4.0 mm) made of SUSXM27 was kept in nitrogen at 1200 ° C. and 1 atm for 20 minutes to perform a nitrogen solid solution treatment. When the nitrogen content in the cross section of the round bar after the treatment was measured using EPMA JXA-8900 manufactured by JEOL, a nitrogen solid solution γ phase (surface layer portion) was formed with a thickness of 20 μm from the surface. After cutting this round bar to a thickness of O.9 mm, both sides were polished with # 2000 abrasive grains to a thickness of O.8 mm, and then mirror-finished by barrel polishing, as shown in Fig. 3 (c) As shown, a disk-shaped keeper having a nitrogen solid solution γ phase (surface layer portion) formed only on the side surface of the disk was manufactured. FIG. 5 shows a photograph obtained by etching the cross section of the obtained keeper and observing with an optical microscope. The surface layer portion had a nitrogen content of 3.4 mass% and a surface hardness (Vickers hardness) of 350 HV.

  When the occlusion test was performed in the same manner as in Example 1 using the obtained keeper and the hyper slim magnet structure 4013, surface roughness was seen in the magnet structure after 1 million tests. The keeper did not show surface roughness or deformation.

Example 3
A round bar (diameter: 4.0 mm) made of SUSXM27 was held in nitrogen at 1200 ° C. and 1 atm for 45 minutes to perform nitrogen solid solution treatment. After cutting this round bar to a thickness of O.9 mm, both sides were polished with # 2000 abrasive grains to a thickness of O.8 mm, and then mirror-finished by barrel polishing to produce a disk-shaped plate . This disk was kept in nitrogen at 1200 ° C. and 1 atm for 15 minutes and again subjected to nitrogen solid solution treatment to produce a disk-shaped keeper. FIG. 6 shows a photograph obtained by etching the cross section of the obtained keeper and observing with an optical microscope. When the amount of nitrogen in the cross-section of the obtained keeper was measured using EPMA JXA-8900 manufactured by JEOL, as shown in Fig. 3 (b), the side surface of the disk was fixed with nitrogen to an average depth of 100 μm from the surface. A dissolved γ phase (surface layer portion A) was formed, and a nitrogen solid solution γ phase (surface layer portion B) was formed on the main surface from the surface to a depth of 20 μm. The nitrogen content of the surface layer part A is 3.5% by mass and the surface hardness (Vickers hardness) is 350 HV. The nitrogen content of the surface layer part B is 3.5% by mass and the surface hardness (Vickers hardness) is 350 HV. Met.

  When the occlusion test was performed in the same manner as in Example 1 using the obtained keeper and the hyper slim magnet structure 4013, surface roughness was seen in the magnet structure after 1 million tests. The keeper did not show surface roughness or deformation.

1 ... Magnetic attachment magnet structure
2 ... Keeper for magnetic attachment
3 ... Root plate
4 ... tooth root
5 ... Artificial teeth
6 ... Denture base
21 ... Main body
21a ・ ・ ・ Side
21b ・ ・ ・ Main surface
22, 22a, 22b ... surface layer
101 ・ ・ ・ Cup type yoke
102 Permanent magnet
103 ・ ・ ・ Disc yoke
104 ... Shield ring
200 ・ ・ ・ Occlusal testing device
201 ... Lower sample stage
202 ... Upper sample stage
203 ... Lower plate
204 ... Upper plate
205 ... Shaft
206 ・ ・ ・ Bearing
207 ... Pressure bar
208 ・ ・ ・ Spring

Claims (7)

A keeper for a dental magnetic attachment that is installed on a root face plate embedded in a tooth root and holds a denture by a magnetic attractive force of a permanent magnet,
It has a plate-like main body portion made of corrosion-resistant soft magnetic ferritic stainless steel, and a surface layer portion made of austenitic stainless steel having a thickness of 10 to 120 μm formed on at least a side surface of the main body portion. Keeper for magnetic attachment.   2. The magnetic attachment keeper according to claim 1, further comprising a surface layer portion having a thickness of 0 to 50 μm on a main surface of the main body portion.   3. The magnetic attachment keeper according to claim 1, wherein the main surface of the main body portion does not have a surface layer portion.   4. The magnetic attachment keeper according to claim 1, wherein the surface layer portion is formed of a nitrogen solid solution phase.   5. The keeper for a magnetic attachment according to claim 4, wherein the nitrogen content of the surface layer portion is 0.5 to 4.5% by mass.   6. The magnetic attachment keeper according to claim 1, wherein the Ni content is 0.2% by mass or less.   The keeper for a magnetic attachment according to any one of claims 1 to 6, wherein the Cr content is 17 to 32% by mass.