CA1215669A

CA1215669A - Producing prosthetic teeth by plating metal ceramic composite solution and applying ceramic layer method

Info

Publication number: CA1215669A
Application number: CA000389936A
Authority: CA
Inventors: Masato Ueno; Mitsuyuki Tasaka; Tatsuro Naito; Masayoshi Sato
Original assignee: Kyoto Ceramic Co Ltd; Four Brain Co Ltd
Current assignee: Kyoto Ceramic Co Ltd; Four Brain Co Ltd
Priority date: 1980-11-12
Filing date: 1981-11-12
Publication date: 1986-12-23
Also published as: DE3144859A1

Abstract

ABSTRACT OF THE DISCLOSURE
A composite solution having metal ions and fine ceramic particles dispersed therein; and a method of using same to firmly bond metal and ceramics whereby the composite solution is applied to a metal base wherein a plurality of fine ceramic particle project protrude above the composite layer solution, and further applying a ceramic layer and firing same.

Description

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1 BACKGROUND OF TO _ INVENTION
1. Field of the Invention This invention relates to a method of firmly bonding metal and ceramics, prosthetic teeth produced by the practical application of such method an composite plating materials for use in such bonding method.

2. Description of the Prior art In the past, the ceramics were directly coated on the surface of the metal and then fired to fuse them. However because this method attained only poor bonding strength, a method is generally employed, in which the surface of the metal is roughened by etching and then the ceramics are fired on the roughened surface to fuse them, in order to obtain their higher bonding strength. This method has also disadvantages in that sufficient bonding strength cannot be obtained because of great difference in the physical properties between metal and ceramics, and the ceramics are separated from their bonding portion by small stress.
Therefore, these conventional methods could not be used, when the bonded products were to ye thereafter subjected to severe vibration, repeated heating and cooling or excessive load. Namely, these methods had only restricted fields of their application and insufficient reliability.
A method of producing prosthetic teeth, especially cast metal crowns fused to porcelain, which is conventionally used in a dental field, comprises coating cast metal crowns with opaque porcelain and after firing, with dental crown colored porcelain in order to hide the color of the metal and improve the bonding to the dental crown colored porcelain in the upper layer. However, this method has a problem of weak ~Z3~56Ç~g3 1 bonding of cast metal crowns to opaque porcelain as detailed below. One is now forced to use a nickel-chromium alloy due to a sudden rise in prices and a shortage of non-oxidizable noble metals such as gold or palladium which are ideal as a material for the cast metal crowns. When the opaque porcelain coated on a ni~kel-chromium alloy is fired at a temperature ranging from 940C to 960C, the alloy is oxidized and gas is evolved and remains within the opaque porcelain, so that the firm bonding cannot be obtained and defects such as breakaway and discoloration 0 of the opaque porcelain occur.

In order to eliminate these defects one will consider that a non-oxidizable metal such as gold, palladium, nickel, chromium and the like is plated on the surface of the cast metal crown of nickel-chromium alloy. Only by plating the non-oxidizable metal, however, the surface of the cast metal crown can be prevented from the oxidation, but the inorganic opaque porcelain cannot be firmly bonded.
Thus, it is an object of this invention to provide a novel method of firmly bonding metal and ceramics.
It is another object of this invention to provide composite plating materials used for firmly bonding metal and ceramics.
It is still another object of this invention to pro-vise prosthetic teeth in which porcelain is firmly bonded to metal crowns and is not broken away and discolored.
SUMMARY OF THE INVENTION
This invention provides a novel method of firmly bonding metal and ceramics which comprises plating a composite plating material consisting of a metal plating composition incorporate I in fine particles of ceramics on a surface of the metal to _;~_ . ;

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1 which ceramics are to be bonded, a metal plating layer being formed on the surface of which has partially protruding fine particles of ceramics, and then firing ceramics to be bonded on the surface of the metal plating layer in order to fuse them.
This invention provides, in another aspect, composite primary plating materials consisting of a metal plating composition incorporating fine particles of ceramics for use in such method of bonding metal and ceramics.
Furthermore, this invention provides prosthetic teeth produced by plating a composite plating material consisting of a petal plating composition incorporating with fine particles of ceramics on the surface of a metal crown for prosthetic teeth, a metal plating layer being formed on the surface ox which has protruding fine particles of the ceramics and firing dental opaque porcelain on the surface of the metal plating layer to fuse them, GRIEF DESCRIPTION OF THE DRAWINGS
Fig, 1 is an enlarged cross-sectional view of the metal base having thereon the metal plating layer on the surface of which has partially projected fine particles of the ceramics, Fig. 2 is an enlarged cross-sectional view of the metal vase having the ceramics bonded according to this invention, Fig. 3 is a cross-sectional view for illustrating the process of plating on the surface of the metal crowns for prosthetic teeth in the method of this invention, Fig. 4 is a cross-sectional view of an embodiment of the prosthetic tooth produced according to the method of this invention, and each of Figs. 5, 6, 7, and 8 represents a ready-made prosthetic tooth produced according to the method of this :~Z~S~9 1 inventor In each of these drawings, a left hand view (at I
a front view of the tooth/ central view (blue I a central cross sectional view of the toot hand a right-hand vacua) us a perspec-live view of the tooth., ETAILED:~ESCRIPT;ION: OF THE REFRIED EMBODIMENT
A method of bonding metal and ceramics. according to this invention will now-be more specifically described by the aid of the accompanying drawings As is shown in Fig, 1, on the surface of thy metal base 1, erg, iron beset to be bonded to the ceramics the metal plating layer 4 is formed by plating a composite plating material consist-in of a metal plating composition incorporating fine jar-tides 3 of the ceramics according to the known plating method.
Thereby, the fine particles 3 of the ceramics are fixed by the' metal plating slayer 4 and protruding from its surface.
As the' metal plating composition, the well known plating solutions can be used from which a metal swishes nickel chromium gold, palladium etch or on alloy such as nickel chromium alloy, gold-pallad~um alloy etc. can be dopiest. For example' there may be use a solution containing a mixture of nickel sulk fate, nickel chloride and boric acid in case of nickel plating, and a solution containing a mature of palladium di,am,i~noni;tx~te~
ammonium nitrate and sodium nitrite in case of palladium plating, . The fine particles of the ceramics, which are incorporated into the metal plating composition described above, should have, as one of their properties, a physical and/or equal bonding easiness with the ceramics to be fused to them by foreign Yost desirably, the fine particles of the ceramics should be identical in composition with the ceramics to be fused thereon. If the fine particles of the ceramics are not identical ion composition i - t ``" 1;2~56~9 1 with the latter ceramics, it is desirable for the purpose of attaining the firm bond and preventing the ceramics to be fused by firing from its break-away that the thermal expansion factor of the former be as close to that of the latter as possible.
In general, alumina (Aye), silicon dioxide (Sue), magnesium oxide (Moo), titanium dioxide (Tao) and the Composite thereof or a ceramic material containing the above oxide or composite as the main component are useful as the fine particles I of the ceramics. The grain size of the fine particles of the ceramics used ranges usually from 5 microns to 100 microns. The amount of the fine particles of the ceramics in the metal plating composition may depend on an application field of the product and is usually 500 - 900 g, preferably 650 - 850 g, per liter of the composition.
If the thickness of the metal plating layer 4 is below 1/2 of the average diameter of the fine particles of the used ceramics, the fine particles 3 cannot be firmly fixed to the plating layer 4. On the other hand, if thy thickness of the metal plating layer 4 is above two thirds of the average diameter of the fine particles 3 of the used ceramics, the particles 3 have a reduced area of contact with the ceramics to be fused by firing and cannot be firmly bonded to the latter ceramics.
Therefore, it is preferable that the thickness of the metal plating layer ranges from one half to two thirds of the average diameter of the fine particles of the used ceramics.
Thereafter, slurry-like ceramics 2 are coated on the metal plating layer 4 formed on the base 1 at a desired coating thickness. After drying, the ceramics are fired at a temperature, at which the ceramics are fused to the metal, for example, at 12~56~g 1 940 - 970C. Thus, the ceramics 2 are firmly bonded to the metal base 1 as is shown in Fig 2.
This firm bond appears to ye based on the integral structure formed by fusing the fine particles of the ceramics fixed to the metal plating layer 4 and protruding there-on and the slurry-like costed ceramics during firing, and on thy physical structure, in which the ceramics applied in the form of the slurry are engaged with the projections of the fine par-tides of the ceramics so as to prevent from the break-away.
The thus resulting bond according to the method of this invention and the bond according to the prior art method in which the ceramics are directly fused to the metal were compared with regard to the bonding strength. The following rev sults-of the comparative tests were obtained, Comparison of Bonding Strength (Kg/cm ) (Test method: Shearing test by means of Instron type universal tester) Method of this invention Prior art method . ._ .
sty test 351 kg/cm2 90 Kim end test 356 133 Average 353.5 111,5 .

As is apparent from the above data, the bond-according to the method of this invention was a bonding strength of three times or more of that of the bond according to the prior art method. Furthermore, the prior art method results in a large and wide scattering of the bonding strength data (numerical data, while the scattering of the bonding strength data according to the ~2~5~

1 method of this invention occurs only in a narrow scope an is constant. In addition, the bonding strength data according to the method of this invention do not depend on the type ox character of the matrix metal 1.
The production of the prosthetic teeth according to the method of this invention is described hereinafter.
First, a metal crownforaprosthetic tooth is prepared by pressing or casting. This metal crown is made of a metal or alloy, such as gold, palladium, gold-palladium alloy, nickel-chromium alloy and the like.
In this embodiment, the metal crown is prepared from anickel-chromium alloy consisting of 82% of nickel, 10% of cry-mum, 5% of molybdenum, 1.8% of beryllium and 1.2% of the other metals.
Then, as is shown in Fig. 3, a palladium plating material containing the fine particles 3 of the ceramics is charged into a plating tank 9. The plating is carried out by connecting a pole plate 7 to an anode and the metal cast crown 8 to a cathode, respectively. As is shown in Fig 4, the number-out fine particles 3 of the ceramics are adhered to the surface of the cast metal crown 8; and palladium is deposited in the space between the fine particles 3 of the ceramics thereby in-creasing the thickness of the plating layer over time in order to fix the fine particles 3 of the ceramics.
When the plating layer 4 reaches the thickness about one half to two third of the average diameter of the fine particles

3 of the ceramics, the plating is stopped and the cast metal crown 8 is removed from the plating tank 9 and washed. By washing, only the fine particles of the ceramics directly fixed I to the surface of the cast metal crown 8 through the plating ;
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layer 4 are kept from amongst the numerous fine particles of the ceramics adhered to it, so that the heads of the fine particles 3 are sufficiently protruding from the plating layer, while the other fine particles 3 of the ceramics are washed out. In the plating, a part of the crown in which the plating is not no-squired, is protected my application of an insulating coating similarly to the case of the conventional plating.
Thereafter, the opaque porcelain 10 is coated on the thus resulting primary plating layer and fired, as is shown in I Fig. 4 in the partial cross-sectional view of the finished article.
The depressions between the projections of the fine particles ox the above ceramics over the plating layer 4 are filled with the opaque porcelain 10. The opaque porcelain is thus engaged with the projections to produce a firm bond physically, and also chum-icily, if at least some of the fine particles of the ceramics are of the same type as the opaque porcelain 10 the coating and firing of the dental crown colored porcelain 11 and the enamel ceramics 12 on the surface of the opaque porcelain 10 are carried out in a similar manner to the conventional one. Since each of the opaque porcelain 10, the dental crown colored porcelain 11 and the enamel porcelain 12 consists of ceramics of-the same type containing alumina and silicon dioxide as the main part, their bonded surface cannot break-away.
When particles of alumina having a thermal expansion factor of 7 x 10 6/C - 14 x 10 6/C are used as the fine par-tides of the ceramics incorporated into the metal plating come position the firm bond can be obtained without effects caused by the thermal expansion and the contraction, since the above opaque porcelain 10 has generally a thermal expansion factor 12 x 10 6 /C - 13 x 10 6/C.

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so 1 The method of bonding metal and ceramics according to this invention can be applied to prosthetic teeth with various shapes other than those shown in Fig. 4.
For example, Fig. 5 to Fig. 8 each represents a different embodiment of so-called ready-made prosthetic teeth which are standardized in size and shape. In these cases, a metal material is pressed or cast to form the metal crown 21 having depressions and projections integral therewith, which are used to set it. The dental crown colored porcelain 23 is fused to the formed metal crown 21 by firing.
In order to firmly bond the dental crown colored port Solon 23, i.e. an inorganic material to the metal crown 21, the surface of the plating layer 22 of a non-oxidizable metal such as gold or palladium is roughened by embedding numerous fine particles of the ceramics such as alumina, from one half to one third of the average diameter of which particles is protruding over the surface of the plating layer 22, and thereon the dental opaque porcelain (not shown) and the dental crown colored port Solon 23 are successively coated, and subsequently fired at atmospheric pressure or under reduced pressure of 65 - 70 cmHg in an electric furnace. Thus, both physical and chemical bonds are attained and therefore the firm bond can be obtained.
The material suitable for a metal crown 21 is a non-oxidizable metal such as gold, palladium. However, since these noble metals are very expensive and short of stock, a nickel-chromium alloy is used in order to produce prosthetic teeth at low expenses.
The above prosthetic teeth of the invention have the following advantages:
(1) The bond of a metal crown and a ceramics has a bonding ~5~6~

1 strength of three times or more of that of the bond according to the prior art method, and the prosthetic teeth can be semi-permanently used without break-away of the ceramics.
(2) The prosthetic teeth are strong and not easily damaged, since porcelain is fused in a thin and uniform layer to a metal crown.
I The prosthetic teeth are very light in weight, since their thickness is reduced to lo-5 - lo 7 mm, while that of the prior art is 4 - 5 mm. Particularly in case of complete or full upper denture, the denture is rarely dislocated, because there is less of a tendency for a light denture to be dislocated

(4) Processing or fabrication can be easily carried out, since the prosthetic teeth have excellent strength

(5) So-called staining (or dying) for altering the color of the teeth can be easily carried out and the individual color can be easily adjusted.

(6) A metal crown can be produced at low expenses by using a nickel-chromium alloy.
I The prosthetic teeth have excellent service durability, since they can be firmly fitted to a dental plate by depressions and 20 projections which are integrally wormed to a metal crown.
(8) Dental work can be easily carried out, since thin prosthetic teeth can be produced.
While the invention has been shown and described with reference Jo a preferred embodiment thereof, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the in mention as defined by the following claims.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of firmly bonding metal and ceramics comprising the steps of:
plating a metal base with a plating composition containing metal ions and fine ceramic particles dispersed therein to form a composite layer on the metal base, said composite layer compris-ing a metal layer on the surface of the metal base having a plur-ality of fine ceramic particles embedded in the metal layer and protruding above the metal layer;
applying a ceramic layer to the composite layer; and firing the ceramic layer to fuse it to the composite layer and thereby to the metal base.

2. A method according to claim 1, wherein the thickness of the metal plating layer ranges from one half to two thirds of the average diameter of the fine particles of the ceramics.

3. A method according to claim 1, wherein the thermal ex-pansion factor of the fine particles of the ceramics approximates that of the ceramics to the bonded.

4. A method according to claim 1, wherein the fine particles of the ceramics are selected from alumina, silicon dioxide, magnesium oxide, titanium dioxide and mixtures thereof or a ceramic material containing one of said oxides or a mixture thereof as the main part.

5. A method according to claim 1, wherein the metal of the plating layer is selected from gold, palladium, gold-palladium alloy, nickel, chromium and nickel-chromium alloy.

6. A method according to claim 1, wherein the metal base is a metal crown for prosthetic teeth, and the ceramic to be bonded is a dental opaque porcelain.

7. A method according to claim 6, wherein the thermal expansion factor of the fine particles of the ceramics approximates that of the dental opaque porcelain.

8. A method according to claim 6, wherein the metal crown for the prosthetic teeth is made of a nickel-chromium alloy.

9. A method according to claim 6, wherein the metal crown for the prosthetic teeth has depressions or projections for fit-ting.

10. Prosthetic teeth produced according to the method of claim 6.

11. Prosthetic teeth produced according to the method of claim 7.

12. Prosthetic teeth produced according to the method of claim 8.

13. Prosthetic teeth produced according to the method of claim 9.

14. A method of firmly bonding metal and ceramics comprising the steps of:
plating a metal base with a plating composition com-prised of a metal containing plating composition having fine ceramic particles of 5 to 100 microns in grain size dispersed therein to form a metal plating layer on the surface having protruding fine particles of ceramic;
applying a ceramic layer to the metal plating layer;
and then firing the ceramic layer to fuse it to the metal.