Dentistry – Prosthodontics – Holding or positioning denture in mouth
Patent
1996-08-27
1999-08-03
Lucchesi, Nicholas D.
Dentistry
Prosthodontics
Holding or positioning denture in mouth
A61C 13235
Patent
active
059316764
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to dental attachments which utilize magnetic attractive force to retain a denture on tooth roots, specifically to the ones which have thin disk shape with smaller cross section than that of tooth root.
BACKGROUND ART
As shown in FIG. 23, an existing method to attach a denture on the gingiva by a dental magnetic attachment is as follows. Root cap 102 is set on the tooth root 101 in the gingiva to form an abutment tooth for the denture 110. A keeper 103 made of corrosion-resisting soft magnetic alloy is embedded in the center of top surface of root cap 102. A dental attachment 111 is embedded in the center of bottom face of the denture so as to face the keeper 103. The attachment 111 attracts the keeper 103 magnetically, thus the denture 110 is fixed on the root surface 102.
Japanese patent application Laid-Open (Kokai) No. 1-303145, 2-295557, 2-295558 disclose a dental attachment 111 of which exploded view is shown in FIG. 24, sectional view in FIG. 25. This existing attachment consists of a block of magnet 112, a spacer 113 made of corrosion resisting non-magnetic alloy to cover one face of the magnet, a pair of yokes 114, 115 that made of corrosion resisting soft magnetic alloy to sandwich the magnet 112 and the spacer 113 in between, and a cap 116 made of corrosion resisting non-magnetic alloy to cover whole other parts. This dental attachment has a magnet 112 with the N-S direction parallel to the keeper 113. A magnetic circuit is formed in which the magnetic flux generated at the magnet 112, passes through the yoke 114, keeper 103, then the other yoke 105, finally returns to the magnet 112. This closed magnetic circuit gives relatively strong attractive force.
Japanese patent application Laid-Open (Kokai) No. 57-164054 disclose a dental attachment 121 of which magnet arrangement is shown in FIG. 26. The attachment in the denture is shown in FIG. 27. This dental attachment consists of plurality of pairs of permanent magnet 122 and soft magnetic part 123. The permanent magnets 122 and the soft magnetic parts 123 are arranged alternatively so that the like magnet poles face each other. When a soft magnetic body, so called attachment keeper, is placed in contact with the attachment 121, almost all magnetic flux pass along the keeper so that it is attracted to the attachment 121 quite firmly.
DISCLOSURE OF THE INVENTION
There is considerable demand for dental magnetic attachments to have an acceptable combination of stronger attractive force (more than 500 gram force) and small height (below 1.5 mm). The demand requires advanced technique in magnetics that improves the magnetic attractive force per unit volume F/V, that is, reduce the height without increasing the sectional area of the dental magnetic attachment. Since F/V in a given magnetic structure is determined by the characteristics of the material, it is difficult to improve F/V.
This invention is offered to solve the above mentioned problem, and offers an attachment with a combination of small height and strong attractive force, in other words, offers the means to increase the attractive force per unit volume F/V drastically.
First the structure of the invented attachment is described. Here `height` is defined as a length taken along the direction of attraction, and `thickness` is defined as a length taken along the direction normal to attraction.
The invented attachment consists at least three yokes and at least two pieces of magnet. The yokes are made of soft magnetic material, and a face of the yokes attaches to said keeper by magnetic attraction.
The magnets are sandwiched by the yokes. Their magnetization direction are parallel to the thickness-direction and the poles of each magnet which contact to the central yoke has like polarity. Each magnet form mutually independent magnetic circuit in which the magnetic flux generated at one pole of the magnet pass through one of two yokes in contact with the magnet, said keeper, and the other of said yokes and returns into the other pole of the magnet.
The r
REFERENCES:
patent: 5425763 (1995-06-01), Stemmann
patent: 5678998 (1997-10-01), Honkura et al.
patent: 5788493 (1998-08-01), Tanaka et al.
Fujii Hideki
Honkura Yoshinobu
Tanaka Yoshinobu
Yokoyama Takashi
Aichi Steel Works Ltd.
Lucchesi Nicholas D.
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