Dentistry – Prosthodontics – Tooth construction
Patent
1995-05-01
1997-12-16
Lucchesi, Nicholas D.
Dentistry
Prosthodontics
Tooth construction
4332281, A61C 1308, A61C 500
Patent
active
056977859
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to dental prostheses, and to composite materials for making them.
Before describing the invention, it is appropriate to explain the terminology used in the present text including terms used by the person skilled in the art.
Dental care essentially comprises the field of repairing and reconstructing teeth proper, and the field of prosthetic reconstructions. Repairs cover fillings (classes I to V), inlays and onlays, and facings.
Prosthetic reconstructions cover both fixed prostheses and removable prostheses. Such reconstructions have a metal portion and usually involve several teeth, but they may also concern one tooth only. They are fixed to one or more teeth. They may also be fixed to one or more implants. Such reconstructions are also referred to as "prostheses" in the present text.
2. Statement of the Prior Art
The invention relates to prosthetic reconstructions of the fixed type. Such fixed type reconstructions generally comprise a metal support made by casting a metal or an alloy, and a reconstruction mass fixed to the support and which may be made out of various different materials. The materials most commonly used for such fixed reconstructions are ceramics. Plastics are also used, and sometimes also composites.
All such fixed reconstructions suffer from drawbacks.
Ceramics reconstructions are very rigid and have insufficient bending strength. They must be fixed on teeth that have been thoroughly consolidated. Nevertheless, when people are fitted with such a reconstruction that is large in size, they generally have and continue to have problems with the periodontium (alveolysis) with or without thickening of the periodontal ligament, and frequently with more or less pronounced mobility of the teeth. Installing such a ceramic reconstruction on teeth consolidated in this way leads to a high failure rate.
Reconstructions made of plastics are most advantageous from the point of view of rebuilding teeth since once such a prosthesis has been worn for a certain amount of time, it is observed that tooth mobility is reduced, as is alveolysis and the periodontal space. It is sometimes even possible to make a ceramic prosthesis on teeth that have been consolidated in this way by carrying a plastics prosthesis for a certain length of time. However, such a plastics prosthesis wears very quickly, and therefore cannot constitute a long-term solution, but merely a solution that is provisional or temporary.
Between these two extremes of behavior, attempts have already been made to use other materials having wear rates that are smaller than those of plastics while still being less rigid and more flexible than ceramics.
Thus, French patent No. 2 427 357 is concerned with the poor properties of hardness, bending strength, and resistance of the synthetic materials that were in use at that time (1978). That patent suggests using a thermosetting composition designed for dental purposes and suitable for use in "certain prostheses". The composition includes a "reinforcing filler" constituted by glass fibers or glass microspheres. The quantity of the reinforcing filler used lies in the range 1% to 50%, and preferably in the range 15% to 40%. The mechanical properties obtained are only a little better than those of the synthetic materials on their own.
Subsequently, composite materials have been used for these purposes, i.e. materials comprising a polymer binder containing an inorganic filler, and serving to make reconstructions. One of the substances giving the best results at present is sold under the trademark "Dentacolor" (Heraeus-Kulzer). However, these substances are too rigid, and it is common for them to fracture, in the same manner as can happen with reconstructions made of ceramics. In addition, their wear resistance is insufficient for very long duration reconstructions. They have therefore been used very little for reconstructions.
European patent application No. 102 199 relates to dental repair compositions stated to have excelle
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