Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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
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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
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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
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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
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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
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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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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
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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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