Patent Application
20090053676
The present invention generally relates to dental restorations. More particularly, the invention relates to a restoration, such as a “porcelain fused to metal” (PFM) restoration, the intaglio of which is plated in gold.
Various compositions for crowns are known. Typically, crowns have lingual collars, i.e. a band of polished alloy on the outside of the restoration or crown, as shown in
There are problems associated with crowns having lingual collars. It is well known that lingual collars made of chromium alloys (containing some percentage of nickel) cause an allergic reaction in a number of patients. When the patient's tissue contacts the alloy, the area may become inflamed and irritated. This is the same common allergic reaction that some individuals have to costume jewelry made of nickel, which can irritate and inflame the skin at the point of contact. Lingual collars are also not aesthetically pleasing to some patients because the polished metal band is visible in the mouth.
Ceramic crowns have been made without lingual collars, such that the entire outside of the restoration or crown is ceramic, and has a cast metal intaglio (so-called porcelain-fused-to-metal or “PFM” crowns). These crowns have been made with solid castings such as: chrome cobalt with nickel; a “noble” metal, i.e., palladium with a small amount of gold; or a “high noble” or half-gold metal. Full ceramic exterior crowns also suffer from problems. Like crowns with a lingual collar, ceramic crowns made of chromium alloy castings also cause an allergic reaction in a number of patients, as the alloy intaglio of the solid coping touches the patient's gum tissue. Further, castings made of gold, while not causing the same allergic reaction, may be cost-prohibitive.
It would be advantageous to create a ceramic crown that avoids causing allergic reactions and that is also aesthetically pleasing and affordable.
The following terms are used in the claims of the patent as filed and are intended to have their broadest meaning consistent with the requirements of the law. Where alternative meanings are possible, the broadest meaning is intended. All words used in the claims are intended to be used in the normal, customary usage of grammar and the English language.
“Building” means the process of applying layers of ceramic material such as porcelain to the coping.
“Coping” means an alloy, made from either a lost wax technique or using CAD/CAM technology, that mimics the shape of the prepared tooth. The structure resulting from the lost wax process may also be referred to as a “casting.”
“Full ceramic exterior” means that the exterior portion of the crown is completely covered in a ceramic material such as porcelain.
“Gold plated” means a thin layer of gold (e.g., 24-carat gold) alloy covering the intaglio.
“Intaglio” means the interior surface portion of the crown, adjacent the human tooth which the crown covers. It is the portion of the alloy casting that is exposed and not covered by porcelain.
“Lingual collar” means a band that is located on the outside portion of the crown. It is generally made of the alloy that makes up the intaglio or solid casting.
“Nickel-chromium alloy” means a metal alloy with substantial amounts of nickel (e.g., 79%) and chromium (e.g., 11%), and possibly including lesser amounts of other metals (e.g., molybdenum, aluminum, beryllium, etc.).
“Opaquing” means the process of applying a first layer of ceramic material such as porcelain to the coping.
“Porcelain fused to metal” (PFM) means a type of restoration that uses an alloy casting as a base and a ceramic material such as porcelain which is layered and baked thereon to create a restoration that is made of ceramic and metal in one cohesive piece.
The objects mentioned above, as well as other objects, are solved by the present invention, which overcomes disadvantages while providing new advantages not previously obtainable with such crowns.
In a preferred embodiment, a crown is made from a metallic coping by coating it entire exterior with a ceramic material such as porcelain, and by gold-plating its interior surface or intaglio. The resulting crown covers any patient exposure to the underlying metallic coping (e.g., a nickel-chromium alloy) along the gum line, as only ceramic and gold plating are in contact with the patient's mouth, sealing the mouth from exposure to the alloy, thus avoiding allergic reactions caused from patient exposure to the metallic coping. The crown appears like a natural tooth, and may be economically manufactured. Additionally, no metal can be seen in the patient's mouth and the crown may be made to appear like a natural tooth, so that the crown is aesthetically pleasing to patients both before (ceramic crown with gold intaglio visible) and after (ceramic crown exterior only visible) placement.
The novel features which are characteristic of the invention are set forth in the appended claims. The invention itself however, together with further objects and attendant advantages thereof, will be best understood by reference to the following description taken in connection with the accompanying drawings, in which:
The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention.
Set forth below is a description of what are believed to be the preferred embodiments and/or best examples of the invention claimed. Future and present alternatives and modifications to this preferred embodiment are contemplated. Any alternatives or modifications which make insubstantial changes in function, in purpose, in structure, or in result are intended to be covered by the claims of this patent.
A coping 10, which may be made of an alloy, such as nickel/chromium alloy, is first made to mimic the prepared human tooth using an appropriate lost wax technique or CAD/CAM technology, as is well known in the art. Then, a ceramic material such as porcelain may be applied to the exterior of coping 10.
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The above description is not intended to limit the meaning of the words used in the following claim that define the invention. For example while preferred embodiments involving full porcelain crowns with gold plated intaglios have been described above, persons of ordinary skill in the art will understand that a variety of other designs still falling within the scope of the following claims may be envisioned and used. It is contemplated that future modifications in structure, function, or result will exist that are not substantial changes and that all such insubstantial changes in what is claimed are intended to be covered by the claims.
