Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
1999-10-05
2001-03-20
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
C433S189000
Reexamination Certificate
active
06203325
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a dental magnetic attachment which is embedded in a denture to stabilize the denture on abutment teeth in the oral cavity using magnetic attractive force.
DESCRIPTION OF THE PRIOR ART
Up to the present, a dental magnetic attachment which strongly stabilize the denture on abutment teeth by magnetic attractive force is well known. Its force is acted between a magnetic assembly in a denture and a keeper made from a soft magnetic material embedded in a root cap.
However conventional types of dental magnetic attachment have a week point to give damage to an abutment tooth with a keeper when they are applied to dentures. Each biting makes nearly equal pressure to any artificial teeth of the denture. In the case of free saddle denture shown as
FIG. 22
, the parts on the abutment tooth marked as A shows only small sinking depth of about 0.02 mm, on the other hand the parts on gingiva marked as B shows large scale sinking depth of about 0.2 mm. It means that the sinking depth of the part B is ten times larger than that of the part A. This difference about sinking depth between the part A and the part B concentrates the biting force on the abutment teeth. This concentration is apt to injure the abutment teeth. In some cases the difference makes denture to be leaned so that the denture is put out of the place.
For solving this problem, Japanese Patent application Laid Open(KOKAI) No.7-246208 discloses a cushioned type of dental magnetic attachments shown in FIG.
23
. That has a cap made of an elastic material which is attached to the top of the magnetic assembly by self curing adhesive. U.S. patent application Ser. No. 4,626,213 discloses another cushioned type of dental magnetic attachments shown in FIG.
24
. That also has a cap made of an plastic material which covers the magnetic assembly with a circular side.
The former patent describes that the magnetic attachment has a cushion ability to relief a biting force which is loaded to the denture by means of the elasticity of the cap. But shrinking of the cap toward the vertical direction is accompanied by extention of the cap toward the traverse direction due to the elastic property of the cap material which is expressed by the constant of Poisson ratio. Therefore when it is designed to get the considerably large shrinking, it must have large extension. This large extension makes large stress or gap between the side of the magnetic assembly and its periphery. This gap is apt to cause some trouble that something such as dregs of food is put into the gap and is rotten in it. This elastic motion makes separation or some gap between the magnetic assembly and the cap which are attached by self curing adhesive.
On the contrary when the cap of this type is designed to make the traverse extension to be small, vertical shrinking inevitably comes to be small. In the case, enough vertical shrinking for practical use is not obtained. That is, there remains the large difference of sinking depth between the parts on the abutment teeth and the parts on gingiva, which makes the denture to be inclined and sometimes to be put out of the place.
The latter patent describes that the magnetic attachment has a rotary ability which is given by the seesaw motion of the cap on the magnetic assembly. This motion is made by sliding the cap along the circular side of the magnetic assembly. The seesaw motion can solve the problem that denture is put out of the place due to leaning the denture But it does not show an enough cushion ability to the vertical pressure caused by biting force. Because its mechanics can make only small vertical motion between the magnetic assembly and the cap. When biting, the pressure is concentrated on the abutment teeth to injure them. So it is concluded that this type gives not enough solution on the drawback of conventional types of magnetic attachment, especially when it is applied to free saddle denture.
THE PROBLEMS TO BE SOLVED BY THE INVENTION
The first object of the invention is to provide a dental magnetic attachment which has a cushion cap for protecting the abutment toeth from harmful biting force and for keeping the denture firmly on the abutment teeth to be free from shaking or leaning. This cap makes enough sinking depth on biting so that there is no concentrration of the biting force on the abutment teeth. It is resulted that the denture is free from leaning so as to be kept firmly on the keeper embedded into the root cap. Moreover it is necessary that this cap is kept as a body with the magnetic assembly.
The second object of the invention is to offer the method and instrument for fixing the magnetic assembly with the above mentioned cushion cap to the denture.
When the vertical pressure is loaded on the magnetic attachment, he cap placed on the top of the magnetic assembly can slide along the side of the magnetic assembly in the vertical direction. If the maximum of the biting force is loaded, the cap can sink about 0.20 mm until the front of the sleeve reaches to the bottom surface of the magnetic assembly which is magnetically attached to the top surface of the keeper. If not loaded, the cap is placed on the beginning position. The mechanics which can slide the cap about 0.20 mm, needs a space of 0.20 mm in height around the magnetic assembly.
The magnetic assembly with the cap is used to be embedd into the denture. As for the setting method, first it is placed in the hollow of the denture base made of resin and next is fixed by self curing adhesive. Here since controlling the volume of the adhesive at the optimum is difficult, it is popular that much volume of the resin more than necessity is used. If the volume of resin is less than necessity, enough adhesive strength can not be got. In this case, we would meet with a big problem that the magnetic assembly will drop out of the denture.
From above reason, much resin more than necessity is used when the magnetic assembly is set. As there is the space around the magnetic assembly for sliding, the excess of the self curing adhesive is apt to fill up the space. It means that the space for sliding decreases or disappeares.
The present invention offers the method how to fix the magnetic assembly with the cushion cap to the denture together with a spacer to keep the above mentioned space.
SUMMARY OF THE INVENTION
A dental magnetic attachment disclosed by the present invention is united with a magnetic assembly and a cushion cap. The dental magnetic attachment which is embedded into the denture retains the denture on the abutment teeth by the magnetic force acting between the magnetic assembly and the keeper placed on the teeth root. The characteristic of the present attachment is that the magnetic assembly is covered with a cap made of elastic material and the cap can slide in the vertical direction along the side of the magnetic assembly. The cap is designed to hp united with a core and a sleeve. The core is placed at the designated distance of about 0.20 mm over the top of the magnetic assembly. When the biting force is loaded, the core is dislocated until touching to the top of the magnetic assembly. The sleeve formed around the core can slide down from the beginning position to the bottom of magnetic assembly on loading. However the sleeve is tightly fit to the magnetic assembly so as not to take off.
The present attachment with the cushion cap has capability to sink until the core would touch to the top of the magnetic assembly due to the biting force on biting. Applying the present attachment to the denture, the cushion mechanics can make sinking at the parts on the abutment teeth as much as that at the parts on the gingiva when biting. Uniformly sinking is related that the denture is supported by the abutment teeth and the gingiva impartially. In other words the biting force on the denture is dispersed to gingiva in stead of concentrating on the abutment teeth, so that the abutment teeth is protected from too large biting force. This cushion mechanics also makes the seesaw motion of the cap on the co
Arai Kazuo
Honkura Yoshinobu
Kimura Kazunari
Aichi Steel Works Ltd.
Jacobson Price Holman & Stern PLLC
Lucchesi Nicholas D.
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