Dentistry – Prosthodontics – Preliminary casting – model – or trial denture
Reexamination Certificate
1998-04-06
2001-06-12
Lewis, Ralph A. (Department: 3732)
Dentistry
Prosthodontics
Preliminary casting, model, or trial denture
C433S223000, C106S038220
Reexamination Certificate
active
06244870
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an abutment tooth model and a method of manufacturing a prosthetic restoration to be formed on the abutment tooth model.
2. Description of the Prior Art
There are known prosthetic restorations. A prosthetic restoration is used by being attached to an abutment tooth which has been formed by giinding down a living tooth in the oral cavity. The prosthetic restoration is used by being bonded to and fixed on the abutment tooth with a dental cement.
Both (1) metals such as gold, silver and stainless steel and (2) ceramics such as zirconia, alumina and sapphire have been so far used as structural materials for such prosthetic restorations.
However, prosthetic restorations made of ceramic materials have a disadvantage in that they have lower toughness and therefore are liable to be damaged.
Furthermore, prosthetic restorations made of noble metals such as gold and silver are very expensive. Moreover, prosthetic restorations made of stainless steel have poor biocompatibility, so that they may have an adverse effect on the body such as the onset of metal allergies or the risk of carcinogenic actions due to the elusion of Ni and Cr in particular.
In view of the problems as described above, prosthetic restorations made of Ti (titanium) have been developed in recent years. Ti is light and very strong and has excellent corrosion resistance, and it does not give rise to adverse effects due to eluting materials as described above.
The prosthetic restorations made of Ti are manufactured as follows.
Firsts an abutment tooth model corresponding to the abutment tooth which has been prepared in the oral cavity is made from an ultra-hard plaster. Next, a compound containing Ti powder is built up onto the abutment tooth model to form a green body for a prosthetic restoration, and then the green body is subjected to a binder removal treatment. Thereafter, the green body is sintered together with the abutment tooth model. In this way, the prosthetic restoration comprised of a metal sintered body is obtained.
However, in the conventional manufacturing method for the prosthetic restorations, there is a disadvantage that the obtained prosthetic restoration is fragile and its mechanical strength is low, because Ti contained in the green body is reacted with the ultra-hard plaster during sinteling process so that an oxygen content at a portion of the prosthetic restoration to be in contact with the abutment tooth model increases.
Further, the prosthetic restoration is likely to be bonded to the abutment tooth model when being sintered due to the reaction between the Ti and the ultra- hard plaster As a result, there is a problem in that it becomes difficult to release the sintered prosthetic restoration from the abutment tooth model. Further, there is also a problem in that a reaction product is peeled off from the abutment tooth model and then it is attached to the prosthetic restoration, when the sintered prosthetic restoration is released from the abutment tooth model.
The attached reaction product causes changes in the property of the prosthetic restorations. Further, the reaction product is by nature unnecessary. Therefore, the reaction product is required to be removed. However, the removal operation of the reaction product is quite troublesome and the remainder thereof lowers the quality of the prosthetic restoration.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an abutment tooth model which can improve a mold releasable property of the prosthetic restoration (releasability from an abutment tooth model or a mold) and a method of manufacturing such a prosthetic restoration.
In order to achieve the object, the present invention is directed to an abutment tooth model used for manufacturing a green body for a prosthetic restoration to be attached to an abutment tooth. The green body is formed of a composition containing di powder or Ti alloy powder as its main component, and the abutment tooth model is adapted to be sintered together with the green body. The abutment tooth model has a portion to be in contact with said green body, and at least said portion of the abutment tooth model is formed of a material containing at least one oxide selected from the group comprising Zr, Y and Ca.
According to the invention as described above, it is possible to prevent reaction from being caused between Ti or Ti alloy in the green body and the abutment tooth model or the mold during sintering process, thereby enabling to improve a mold release property and to manufacture a high quality prosthetic restoration easily since no reaction product which is unnecessary by nature is attached thereto. Further, it is possible to provide a prosthetic restoration having excellent biocompatibility and bioaffinity, is light in weight, and has adequate mechanical strength and hardness.
In the present invention, the abutment tooth model may be formed of a material containing at least one oxide selected from the group comprising Zr, Y and Ca.
Further; the abutment tooth model may be provided with a surface layer which constitutes said portion of said abutment tooth model, and said surface layer is formed of a material containing at least one oxide selected fiom the group comprising Zr, Y and Ca as its main component. In this case, it it preferred that said surface layer has a thickness corresponding to a shrinkage which would occur when the green body is sintered.
When such a surface layer is formed on the abutment tooth model or the mold, the surface layer functions as a reaction preventing layer upon sintering. Further, the surface layer also functions as a spacer for compensating the shrinkage of the green body, so that it is not necessary to provide a spacer additionally, thus leading to easiness in manufacturing process.
The present invention is also directed to a method of manufacturing a prosthetic restoration. The method comprises the steps of: preparing an abutment tooth model; building up a green body for a prosthetic restoration which is to be attached to an abutment tooth onto said abutment tooth model, in which the green body being formed of a composition containing Ti powder or Ti alloy powder as its main component, and sintering the green body together with the abutment tooth model to manufacture the prosthetic restoration from the sintered body, wherein said abutment tooth model having a portion to be in contact with said green body, and at least said portion of the abutment tooth model being formed of a material containing at least one oxide selected from the group comprising Zr, Y and Ca.
In this method, it is preferred that the abutment tooth model is formed of a material containing at least one oxide selected from the group comprising Zr, Y and Ca.
Further, it is also preferred that the abutment tooth model includes a surface layer which constitutes said portion of said abutment tooth model, and said surface layer is formed of a material containing at least one oxide selected from the group comprising Zr, Y and Ca as its main component. In this case, it is also preferred that the surface layer has a thickness corresponding to a shrinkage that is caused when the green body is sintered.
Another aspect of the present invention is directed to a method of manufacturing a prosthetic restoration. This method comprises the steps of: preparing an inner mold and an outer mold for defining a cavity between said inner and outer molds; injecting a composition containing Ti powder or Ti alloy powder as its main component into said cavity to obtain a green body for a prosthetic restoration; and sintering the green body together with the inner and outer molds to manufacture the prosthetic restoration from the sintered body, wherein said inner and/or outer molds include a portion to be in contact with the green body, and at least the portion of said molds is formed of a material containing at least one oxide selected from the group comprising Zr, Y and Ca.
In this method, it is preferred that both the inner
Ito Michio
Sakata Masaaki
Shimodaira Kenichi
Bell Boyd & Lloyd LLC
Injex Corporation
Lewis Ralph A.
LandOfFree
Abutment tooth model and method of manufacturing a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Abutment tooth model and method of manufacturing a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Abutment tooth model and method of manufacturing a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2540505