JP2003093408A - Magnetic attachment for dental prosthesis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of a magnetic attachment and the direction of magnetization of a magnet with little reduction of the attraction force when a gap is produced between the magnet structure and a keeper. SOLUTION: The split pole type magnetic attachment has a three-layer structure comprising a cylindrical permanent magnet 2, an upper yoke 1, and a lower yoke 3. The direction of magnetization of the permanent magnet is parallel to the center axis of the permanent magnet and opposite by 180 deg. to the plane passing the center axis. The upper yoke 1 is made of a cylindrical soft magnetic material formed on the top of the permanent magnet. The lower yoke 3 has a rectangular parallelepiped spacer made of a non-magnetic material held between crescent board-shaped soft magnetic materials from both sides.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dental prosthesis characterized in that even if a magnetic gap (hereinafter referred to as a gap) is generated between a magnet structure and a keeper, a decrease in attraction force is small. The present invention relates to a structure of a magnetic attachment. 2. Description of the Related Art A magnetic dental attachment (hereinafter referred to as a magnetic attachment) differs from a conventional method using mechanical force or adhesive force in that there is almost no lateral pressure on the remaining teeth and no palate. It has features that are not available in conventional maintenance devices, such as possible things. Used for the maintenance of dental prostheses such as dentures and jaw prostheses. The magnetic attachment is composed of a magnet structure buried in the denture and a keeper cast in contact with the root plate, and uses a magnetic attraction between the magnet structure and the keeper to maintain the prosthesis. . FIG. 5 shows a diagram in which a magnetic attachment is used for maintaining a denture. [0003] However, a small gap may be generated between the magnet structure and the keeper, which constitute the magnetic attachment, due to a change in the ridge due to aging or a change over time due to long-term use of the denture. Since the magnetic attachment uses a magnetic attractive force as a force for maintaining the prosthesis, the small gap greatly reduces the attractive force. As a result, when using the denture, the user may feel uncomfortable or inconvenience the occlusion, and in the worst case, it may be difficult to maintain the denture. If the denture in which the inconvenience occurs can be reused by modification, it is reused after repair. However, if it cannot be used, it must be newly manufactured, and in any case, much time and cost are required. The magnetic attachments currently in practical use are of a cup type and a sandwich type. FIG. 6 shows the flow of magnetic flux when there is no gap between the magnet structure and the keeper, taking the cup-type magnetic attachment as an example. The magnetic flux coming out of the permanent magnet passes through the side yoke and flows almost perpendicularly into the keeper, so that the large magnetic flux is effectively converted into a magnetic force and becomes a large attractive force. FIG. 7 shows the flow of magnetic flux when a gap is generated between the magnet structure and the keeper. Since the magnetic flux from the side yoke has a gap between the magnet structure and the keeper, this becomes a large resistance or magnetic resistance that impedes the flow of the magnetic flux, and the magnetic flux flows in a direction of the cover yoke with a small magnetic resistance and flows in. . Therefore, the magnetic flux flows into the keeper at an angle. Further, the number of magnetic fluxes flowing into the keeper decreases due to short-circuiting of the magnetic flux from the side yoke to the cover yoke. For these reasons, the attractive force is rapidly reduced by the small gap between the magnet structure and the keeper. Further, one of the basic structures of the magnetic attachment is
There is a split pole type shown in FIG. It has a three-layer structure in which the upper and lower surfaces of two semi-cylindrical permanent magnets are sandwiched between an upper yoke and a lower yoke, respectively. The direction of magnetization of these permanent magnets is parallel to the central axis of the permanent magnet and 180 ° opposite to the plane passing through the central axis. The flow of magnetic flux in this structure is shown in FIGS. FIG. 9 shows the flow of magnetic flux when there is no gap between the magnet structure and the keeper. FIG. 10 shows a case where there is a gap. Due to this gap, the number of magnetic fluxes flowing into the keeper decreases, so that the attraction force further decreases. [0006] The structure of the magnet structure in which the attraction force is unlikely to decrease even if a gap is formed means that even when there is a gap, the magnetic flux is at an angle close to perpendicular to the keeper and many more. The purpose is to find a structure into which magnetic flux flows. SUMMARY OF THE INVENTION The present inventors have solved the above-mentioned problem by providing an angle of magnetization of a permanent magnet of a magnet structure with respect to a plane passing through a central axis of the permanent magnet. Pour more magnetic flux into the keeper over a wide area,
We have developed a magnetic attachment with a magnet structure that allows more magnetic flux to flow into the keeper at a more perpendicular angle. This structure is called an oblique magnetization split pole type magnetic attachment and is shown in FIG. The flow of magnetic flux in these structures is shown in FIG.
And FIG. FIG. 11 shows the flow of magnetic flux when there is no air gap between the magnet structure and the keeper. The magnetic flux flows from the cover yoke to the keeper and from the keeper to the cover yoke at an almost vertical angle. FIG. 12 shows a case where there is a gap. In this state, the magnetic flux reaches a wider range at the lower part of the magnet structure at a more perpendicular angle to the keeper than in the case of the magnet structure of another structure, and even if a gap is generated between the magnet structure and the keeper. A lot of magnetic flux will flow into the keeper. For this reason, a structure in which the suction force is hardly reduced even when a gap is generated. To verify this, attraction force analysis was performed on two types of commercially available structures, an improved split pole type and an obliquely magnetized split pole type magnetic attachment, using three-dimensional magnetic field analysis software by the moment method. The analysis conditions were the same, such as the outer shape of the material used. That is, the diameters of the magnet structure and the keeper are set to 4.0.
mm, the height of the magnet structure was 1.5 mm, and the thickness of the keeper was 1.0 mm. 1.3T magnetization of permanent magnet
And the saturation magnetic flux density of the soft magnetic material was set to 1.6T. The analysis results are shown in FIGS. FIG. 13 shows the suction force for each mold with respect to the thickness of the gap. FIG. 14 shows the ratio of the suction force when the gap is generated to the suction force when the gap is 0 mm, as a percentage. From this graph, it is shown that by giving an angle to the magnetization, the structure has a larger attraction force than the split pole type in which the magnetization angle is 0 °, and the attraction force is hardly reduced. According to the magnetic attachment of the present invention, the suction force is not easily reduced even if a gap is formed. Therefore, the inconvenience when using the denture due to the aging of the ridge or the denture or the denture due to the reduction of the suction force is reduced. Can be expected to be less likely to fall off. In addition, long-term use of the dental prosthesis becomes possible. Furthermore, even a person who has difficulty moving his / her fingers can accurately and easily mount a denture utilizing the attraction force due to a large magnetic force. Further, the improved split pole type uses three permanent magnets having different directions as shown in FIG. 15, so that it is complicated and costly to manufacture. However, the obliquely magnetized split pole type has two permanent magnets, and thus has a structure. Although simple and easy to manufacture, a restoring force close to that of the improved split pole type can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of an obliquely magnetized split pole type magnetic attachment. FIG. 2 is a diagram of an upper yoke of an obliquely magnetized split pole type magnetic attachment. FIG. 3 is a view of a magnet portion of an obliquely magnetized split pole type magnetic attachment. FIG. 4 is a view of a lower yoke of the obliquely magnetized split pole type magnetic attachment. FIG. 5 is a sectional view of a magnetic attachment mounted. FIG. 6 is a diagram showing a flow of magnetic flux when there is no cup-shaped air gap. FIG. 7 is a diagram showing the flow of magnetic flux when there is a cup-shaped air gap. FIG. 8 is a view of a split pole type magnetic attachment. FIG. 9 is a diagram showing a flow of a magnetic flux when there is no air gap in the split pole type magnetic attachment. FIG. 10 is a diagram showing the flow of magnetic flux when there is a gap in the split pole type magnetic attachment. FIG. 11 is a diagram showing the flow of magnetic flux when there is no air gap in the obliquely magnetized split pole type magnetic attachment. FIG. 12 is a diagram showing the flow of magnetic flux when there is a gap in the obliquely magnetized split pole type magnetic attachment. FIG. 13 is a graph showing a magnitude of a suction force with respect to a gap of various magnetic attachments. FIG. 14 is a graph showing a ratio of a suction force to a gap of various magnetic attachments. FIG. 15 is a view of a split pole improved magnetic attachment. [Description of Signs] 1 Upper yoke (soft magnetic material) 2 Permanent magnet 3 Lower yoke (soft magnetic material) 4 Cover (non-magnetic material) 5 Spacer (non-magnetic material) 6 Permanent magnet magnetization direction 7 Keeper (soft magnetic) 8) root 9 magnetic attachment 10 magnet structure 11 denture 12 root plate 13 side yoke (soft magnetic material) 14 cover yoke (soft magnetic material) 15 ring spacer (non-magnetic material)

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yosuke Kiuchi             2-1-1, Minamijomishima-cho, Tokushima City, Tokushima Prefecture             Shima University Faculty of Engineering Department of Electrical and Electronic Engineering (72) Inventor Yoshikawa Tegawa             1-24 No.7 Minamisako, Tokushima City, Tokushima Prefecture (72) Inventor Masahiko Mukai             2-15-10 Hirohoncho, Kure City, Hiroshima Prefecture

Claims (1)

Claims: 1. A cylindrical permanent magnet having a magnetization direction parallel to a central axis of the permanent magnet and 180 ° opposite to a plane passing through the central axis. An upper yoke made of a soft magnetic material having a columnar shape on the upper surface of the permanent magnet (FIG. 2) having a pair of permanent magnets (FIG. 2), and a spacer made of a nonmagnetic material having a rectangular parallelepiped formed on the lower surface of the permanent magnet on both sides. The magnetization direction of the permanent magnet of the split-pole type magnetic attachment having a three-layer structure using a lower yoke (FIG. 4) sandwiched by a soft magnetic material having a meniscus shape from the surface is oriented at an angle with respect to a plane passing through the central axis of the permanent magnet. Dental prosthesis maintenance device with permanent magnets turned on and magnetized.