Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
2000-07-13
2001-10-16
Wilson, John J. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
C433S220000
Reexamination Certificate
active
06302694
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a keeper for dental magnetic attachments so as to fix a denture base by magnetic attraction, and a method for removing the body of the keeper from the tooth root.
2. Discussion of the Background
Dental magnetic attachments to fix denture by magnetic attraction are being developed in the dental field. A known dental magnetic attachment
9
is as shown in FIG.
8
. It is composed of a magnetic assembly
91
and a keeper
92
embedded in a root cap
82
to be attracted by said magnetic assembly
91
. A magnetic attractive force is generated between said keeper
92
and said magnetic assembly
91
. A dental magnetic attachment having the structure mentioned above requires that keeper
92
is incorporated into the root cap
82
by a casting method.
This process in which the keeper
92
is incorporated into the root cap
82
requires precise control of casting conditions at an elevated temperature to maintain the good quality of the keeper
92
. This casting process requires a lot of time and is apt to cause various problems. As a result the cost of keeper preparation is increased significantly. It also prolongs the period for medical treatment to the patients.
Therefore, at the present time, the keeper is cemented directly on the root surface with the application of advanced dental resin. In this case, the keeper
92
, consisting of a body of keeper
921
and a post
922
, is fabricated by machining, as shown in FIG.
9
and FIG.
10
.
However the keeper
92
mentioned above faces following difficulties. First, as seen in FIG.
9
and
FIG. 10
, said post
922
has rather large diameter because of the limitation of machining capability. The thick post requires enlargement of the tooth canal, which makes the root fragile. Furthermore, the shape of said post
922
has no resistance against the post becoming dislodged from the root canal. Second, in the situation where the root surface is inclined against root canal, while the root cap in which a keeper is incorporated by casting can be fitted to such surface inclination, a keeper with the post
922
made by machining can not be adjusted to the inclination. Third, said keeper
92
requires a great deal of time to be removed in case of diagnosing by MRI (magnetic resonance imaging).
The keeper
92
is made of soft magnetic materials, and the material causes an undesirable influence on an MRI image. In the case where patients need to get an MRI diagnosis, both the body
921
and post
922
should be removed from the tooth root to avoid having an adverse influence on MRI image. Thus, removing of the body and post requires a great deal of time and labor.
Considering these difficulties, the present invention provides a keeper for the dental magnetic attachment which is superior in fitting to the tooth root shape, as well as being easier to be removed from tooth root when necessary. The present invention also offers the method to remove the keeper from the tooth root.
SUMMARY OF THE INVENTION
The present invention is directed to a keeper of dental magnetic attachments so as to be attracted by a magnetic assembly embedded in a denture base. This keeper includes a body made of soft magnetic material and a post made of non-magnetic material jointed together at the bottom of the body of the keeper. The post has a bendable part
21
.
One of the most notable points of said keeper is that each part, namely a body of the keeper and a post jointed to said body, is of a different material, the body being soft magnetic material and the post being non-magnetic material, and that the post has the bendable part
21
.
In following section the effects of present invention are described.
The keeper of the present invention has a post on the bottom, so that it can be fixed directly in the root canal with dental resin, without fabricating a costly cast root cap in which the keeper would be incorporated. In the keeper, the body of the keeper is joined together with said post. Therefore it can be fixed directly on a tooth root without using root cap but rather with the use of dental resin. Such reduces the cost and simplifies the manufacturing process by omitting a aforementioned casting process.
The post has the bendable part
21
so that the angle of the post against the body
10
of the keeper
1
can be adjusted to be desired degree. For example, in the case that the root surface is inclined against the axis of the root, said post can be adjusted with respect to the angle of the root axis by bending said bendable part. Therefore the keeper of the present invention has high adaptability to the variety of root surface conditions.
The body of the keeper is made of a different material from that of the post which is made of non-magnetic material. Thus, when MRI diagnosis is needed after embedding this keeper in the tooth root, only the body of the keeper needs to be removed before MRI diagnosis. Such therefore makes preparation for MRI diagnosis easier and requires less time than a conventional keeper, the entirety of which is made of soft magnetic material. Therefore, the present invention provides a keeper of dental magnetic attachment that is adjustable to various shape of the tooth root and relatively easy to remove.
It is preferable that said bendable part is located just under the bottom of the body of the keeper and has a smaller diameter than the other parts of the post. The smaller diameter makes the bending stiffness moderately lower and makes bending easy to accomplish. Also, a smaller diameter bendable part permits the step at the end of the part to have a bigger diameter. This step improves the anchoring effect and strengthens the stability of the keeper from detachment.
It is preferable that the diameter of said bendable part should be within a range of 0.2-0.8 mm. In case the diameter of bendable part is less than 0.2 mm, the stiffness is too low. On the other hand, in case the diameter is more than 0.8 mm, the bending stiffness becomes too high to bend.
The present invention includes a method for taking said keeper after it is fixed in the tooth root with dental resin, wherein, said body of the keeper is removed by cutting said part off from the post together with said dental resin around said body of the keeper.
One of the most notable points of the present invention is that in case of removing the keeper, said body of the keeper made of soft magnetic material is separated from the post made of non-magnetic material and that only the body of the keeper is removed.
In this situation the time required for such work is greatly reduced. Therefor, in case MRI diagnosis is needed without delay, such can be accomplished.
It is preferable to cut off the body at the bendable part. The bendable part not only has lower bending stiffness than any other part has, but also the part is easy to cut, so the work of cutting the post become much easier.
REFERENCES:
patent: 4729736 (1988-03-01), Weissman
patent: 5316478 (1994-05-01), Chalifoux
patent: 5755573 (1998-05-01), LeBlanc
patent: 4-071551 (1992-03-01), None
patent: 7-136190 (1995-05-01), None
patent: 11-146886 (1999-06-01), None
patent: 11-276505 (1999-10-01), None
patent: 11-299807 (1999-11-01), None
patent: 2000-024004 (2000-01-01), None
Arai Kazuo
Hiranuma Kenji
Honkura Yoshinobu
Kimura Kazunari
Mizutani Hiroshi
Aichi Steel Corporation Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wilson John J.
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