US3900951A - Porcelain covered dental bridge, crown and the like - Google Patents

Abstract

A dental crown, bridge or the like is disclosed having a glazed porcelain coating baked on a non-precious metal alloy that is nontoxic and whose major ingredients include iron, nickel and chromium.

Description

United States Patent Bentman [4 1 Aug. 26, 1975 PORCELAIN COVERED DENTAL BRIDGE,

CROWN AND THE LIKE [76] Inventor: David M. Bentman, 315 S. 16th St.,

Philadelphia, Pa. 19102 [22] Filed: June 27, 1974 [21} Appl. No.: 483,755

[52] US. Cl. 32/5 {51] Int. Cl. l. A61C 13/22 [58] Field of Search 32/8, 12,5

[56] References Cited UNITED STATES PATENTS 3,413,723 12/1968 Wagner et a1. 32/8 Primary Examiner-R0bert Peshock Attorney, Agent, or Firm-Seidel, Gonda & Goldhammer [57] ABSTRACT A dental crown, bridge or the like is disclosed having a glazed porcelain coating baked on a nonprecious metal alloy that is nontoxic and whose major ingrediems include iron, nickel and chromium.

6 Claims, 1 Drawing Figure PORCELAIN COVERED DENTAL BRIDGE, CROWN AND THE LIKE BACKGROUND For many years heretofore it has been conventional to use precious metals when making a dental crown, bridge, and the like. The substantial increase in the price of gold has required the industry to find accept able non-precious metals as a substitute for gold and its alloys.

For an example of a non-gold base metal alloy, see U.S. Pat. No. 3,121,629. while the alloy in said patent is a non-gold alloy, it is still a precious metal alloy in view of the inclusion of a preferred platinum family metal of approximately 21%. Further, the alloy disclosed in said patent is unsuitable for baking conventional dental porcelain onto the alloy in view of the inclusion of beryllium which under certain conditions may be toxic. It is essential for the purposes of the present invention that the alloy be nontoxic, by nonprecious, and free from beryllium.

In accordance with the present invention, a glazed dental porcelain coating is baked on an opaque base with an oxidized, nontoxic, non-precious metal alloy substrate which has been cast into an appropriate shape and having the following properties. The tensile strength is between 72,000 and 80,000 psi and preferably approximately 76,600 psi. The yield strength is between 30,000 and 42,000 psi, preferably approximately 33,600 psi. The percentage elongation is between 21.5 and 22.5%, and preferably uniform at 22%. Uniformity of elongation is important so that the metal alloy does not change its external dimensions after it has been fitted to a master working model. The melting temperature of the alloy is between 2300F. and 2400F. with no flux being used in the melt. The hardness of the alloy is about 195-225, and preferably has a mean hardness value of about 212 on the Vickers scale. The thermal coefficient of expansion of said alloy is preferably 90140 l0 /C.

If the alloy tensile strength is too high, and the coefficient of expansion does not lie in the range of 90-l60 l0 /C, dental porcelains with a fusing range of between 1650F and 1850F in the form of an opaque base coating fused over with body and translucent incisal coatings will fracture and/or flake away. Further, the alloy will be too hard to give or stretch when pressed into close fitting conditions. If the yield strength is too high, it is extremely difficult to burnish at the sub-gingiva area. Because of toxicity and difficulty of applying the porcelain coating, the alloy should have no beryllium and no cadmium should be used in soldering alloys.

The non-precious alloy, in addition to being non toxic, should have properties whereby porcelain of a commercially available formula will readily adhere thereto and capable of being baked thereon Without crazing or fracturing. The present invention is particularly adapted for use in connection with permanent dental crowns, bridges, and the like. The word permanent is intended to mean that the dental component is primarily nonremovable. The present invention may be custom fitted by use of conventional dental stretching pliers.

It is an object of the present invention to provide a porcelain covered non-precious metal alloy dental bridge, crown, inlay, transfer, and the like.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

The drawing illustrates two molar crowns mounted on a common substrate to form a dental bridge.

Referring to the drawing in detail, wherein like numerals indicate like elements, there is shown a dental bridge designated generally as 10. The bridge 10 comprises a pair of molar crowns on adjacent tooth preparations 12 and 14 with a common substrate 16 to form a bridge. The portion of substrate 16 associated with the tooth preparation 14 has a translucent porcelain coating 18 over an opaque porcelain base coating 17. As shown in the drawing, porcelain coating 18 is a full coating in that it overlies upper and side faces of substrate 16. The portion of substrate 16 associated with tooth preparation 12 has a translucent porcelain coating 18, over an opaque porcelain base coating 17.

The bridge 10, for the purposes of the present invention is conventional in structure in that it involves a porcelain coated metal substrate. Per se the porcelain material may be conventional and is preferably a commercially available ready mixed dental porcelain of the type adapted to be baked onto the substrate 16 over the opaque base 17. Suitable ready mixed dental porcelain materials are sold commercially under the trademarks Ceramco, Biobond, Vita, etc.

The substrate 16 is preferably a nontoxic, nonprecious metal alloy which after processing has the following characteristics. The tensile strength is between 72 and 80,000 psi and preferably approximately 76,600 psi. The yield strength is between 30 and 42,000 psi, and preferably approximately 33,600 psi. The percent elongation is between 21.5 and 22.5%, and preferably uniform at 22%. The hardness of the alloy is about 210-215, and preferably about 212 on the Vickers scale.

A preferred alloy in accordance with the present invention has the following percentage of ingredients:

Carbon .2 max Silicon l.0 max Manganese 1.0 max Chromium 20-23 Iron l7 20 Molybdenum 8-l0 Cobalt .5-2.5 Tungsten .2-l Nickel balance The alloy is free from beryllium, cadmium, or a toxic ingredient.

The characteristics of the substrate 12 as set forth above are after processing the bridge which involves multiple firings during which time the porcelain layers are baked onto the substrate at temperatures between l650 and 1850F. The properties of the alloy before processing are different from those set forth above and would be as follows:

lngot stage, cold, tensile strength about 71,000

psi

Ingot stage, cold, yield strength about 44,000 psi lngot stage, cold, Vickers hardness mean value lngot stage, cold, elongation 22% Due to the change in the properties of said alloy after firing, from the ingot stage to a casting in the form of the substrate 16, the alloy will cast as a clean virgin metal without fracturing or crazing the porcelain fused thereon. At all times, the specific gravity of the alloy remains at 8.23 em The alloy cast into the form of substrate 12 is easily polished to a high lustrous finish.

The commercially available dental porcelain mixtures referred to above each has a different fusing temperature within the range of l650F.l850F. Also, each said dental porcelain mixture has a coefficient of expansion in the range of 90l25 l0 C. The fusing time for such dental porcelain mixtures during each firing is three to five minutes.

The dental porcelain mixtures identified above are unique in that their coefficient of expansion is independent of the maturing and fusing cycle. The range of the coefficient of expansion of said metal alloy is slightly higher than the corresponding range for said dental porcelains. The coefficient of expansion of said dental porcelains may be adjusted so as to be slightly lower by adding about 6% opaque porcelain into the mixture. This will add to the opaqueness of the color when desired. It is desired that there should be a match of the coefficient of expanof said alloy and the dental porcelain through the various stages of vitrification and up to the glazed end product. The porcelain fused onto said alloy in the end product desirably has characteristics of translucency, semi-opacity, strength, insolubility, resistance to oxidation, maturity and impact strength.

The alloy is cast into the desired dental shape of the substrate 12 for a crown, bridge, etc. The casting is permitted to cool slowly on a fired brick. This anneals the metal preparing it for high speed machining and fitting. The cooled casting is then cleaned by a blast with a noncontaminating material such as quartz grit. No acids are used. Sand or other contaminating material cannot be used for the blasting. The casting is then machined to cut off sprues, dress down the casting, is burnished, and then fitted. The casting is now ready for oxidation.

The alloy casting is then oxidized in a furnace for about three minutes at a temperature of about l100l850F. The color of the alloy should be dullblack for proper oxidation and porcelain acceptance. The alloy casting is then cleaned in a soap solution which is preferably agitated by ultrasonic energy for a period of time of about five minutes. The alloy casting is then dried.

The clean casting at this point may be further cleaned by emersion in acetone for about five minutes. Thereafter, the casting may be removed and dried so that layers of dental porcelain may be applied thereto. At this point, the casting is only handled by tools such as pliers. The alloy casting with a base layer of opaque porcelain coating 17 thereon is then baked or fired at a temperature of about l650l850F. depending upon the instructions of the manufacturer of the dental porcelain mixture. Thereafter, the body and incisal translucent porcelain coating 18 is applied over coating 17 and baked, removed, and air cooled. The alloy casting will turn black inside and at exposed surfaces since this is the nature of the alloy. No change is noticed in the porcelain coating 18 and there is no green staining, bleeding, or black edges. The porcelain coating 18 may be dressed over, and then the baking or firing is repeated a plurality of times such as four more times.

After the porcelain coated casting has been thusly fired and processed, the exposed metal surfaces of the casting are finished and polished. The alloy casting surprisingly has very good affinity for the porcelain fused thereon and has an even finishing line between polished metal and fused porcelain. A glaze may be applied to the final porcelain coating 18 or the porcelain coating itself may be of the self glazing type.

Two or more separate crowns may be made as described then metallurgically bonded to one another to form a bridge using high temperature fusing solder, conventional welding rods, or silver solder. No cadmium or acids are used. A special flux may be used and boiled away with water.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

1 claim:

1. A dental bridge, crown and the like comprising a glazed dental porcelain coating fired onto a nontoxic metal alloy substrate having about the same coefficient of heat expansion, said coating including a translucent porcelain over an opaque porcelain, and said substrate having a tensile strength of 72-80,000 psi, yield strength of 3042,000 psi, elongation of 22-23%, and hardness of about 200-225 on the Vickers scale, said alloy having the following major ingredients:

chromium 20-23% iron 1 7-20% molybdenum 8- l 0% nickel 45-59%.

2. An article of manufacture in accordance with claim 1 wherein said translucent porcelain coating is shaped in the form of a human tooth, and said alloy being free from beryllium.

3. An article of manufacture in accordance with claim 1 wherein said translucent porcelain coating is a full coating.

4. An article of manufacture in accordance with claim 1 wherein said alloy consists essentially of said major ingredients and:

Carbon .2 max Silicon 1.0 max Manganese 1.0 max Cobalt .5-2.5 Tungsten .2 l O.

5. A method of making a permanent dental bridge, crown, or the like comprising the steps of baking a material simulating the color of a tooth on a non-precious metal alloy, using a nontoxic alloy having the following percentage of ingredients:

Carbon .2 max Silicon 1.0 max Manganese 1.0 max Cobalt .5-2.5 Tungsten .2-l .0

Chromium 20-23% Iron 17-20% Molybdenum 8-l0% Nickel Balance and which is free from beryllium or cadmium.

6 6. Amethod in accordance with claim 5 wherein said L88 allo has about the followin ercenta e of in redients- Tungsten y g p g g Chromium 22 Iron l7.9 Molybdenum 8.89 5 Nickel Balance. garhon .(I)() ilicon 5 Manganese 1.0 max

Claims (6)

1. A DENTAL BRIDGE, CROWN AND THE LIKE COMPRISING A GLAZED DENTAL PORCELAIN COATING FIRED ONTO A NONTOXIC METAL ALLOY SUBSTRATE HAVING ABOUT THE SAME COEFFICIENT OF HEAT EXPANSION, SAID COATING INCLUDDING A TRANSLUCENT PORCELLAIN OVER AN OPAQUE PORCELAIN, AND SAID SUBSTRATE HAVING A TENSILE STRENGTH OF 72-80,000 PSI, YIELD STRENGTH OF 30-42,000 PSI, ELONGATION OF 22-23%, AND HARDNESS OF ABOUT 200-225 ON THE VICKERS SCALE, SAID ALLOY HAVING THE FOLLOWING MAHOR INGREDIENTS:

2. An article of manufacture in accordance with claim 1 wherein said translucent porcelain coating is shaped in the form of a human tooth, and said alloy being free from beryllium.

3. An article of manufacture in accordance with claim 1 wherein said translucent porcelain coating is a full coating.

4. An article of manufacture in accordance with claim 1 wherein said alloy consists essentially of said major ingredients and:

5. A method of making a permanent dental bridge, crown, or the like comprising the steps of baking a material simulating the color of a tooth on a non-precious metal alloy, using a nontoxic alloy having the following percentage of ingredients:

6. A method in accordance with claim 5 wherein said alloy has about the following percentage of ingredients:

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