U.S. patent application number 13/724065 was filed with the patent office on 2013-05-16 for non-magnetic cobalt-palladium dental alloy.
This patent application is currently assigned to The Argen Corporation. The applicant listed for this patent is The Argen Corporation. Invention is credited to Paul J. Cascone, Arun Prasad.
Application Number | 20130121871 13/724065 |
Document ID | / |
Family ID | 39766385 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130121871 |
Kind Code |
A1 |
Prasad; Arun ; et
al. |
May 16, 2013 |
NON-MAGNETIC COBALT-PALLADIUM DENTAL ALLOY
Abstract
A non-magnetic cobalt based "noble" metal dental alloy is
provided. The alloy generally contains at least 25 wt. % palladium,
from 15 to 30 wt. % chromium and a balance of cobalt, where to
ensure the alloy is non-magnetic the concentration of chromium in
the alloy is at least 20 wt.%, or if the concentration of chromium
is less than 20 wt. % the combined concentration of chromium,
molybdenum, tungsten, niobium, tantalum vanadium and rhenium is
greater than 20 wt. %.
Inventors: |
Prasad; Arun; (Cheshire,
CT) ; Cascone; Paul J.; (Del Mar, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Argen Corporation; |
San Diego |
CA |
US |
|
|
Assignee: |
The Argen Corporation
San Diego
CA
|
Family ID: |
39766385 |
Appl. No.: |
13/724065 |
Filed: |
December 21, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12050006 |
Mar 17, 2008 |
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13724065 |
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60896182 |
Mar 21, 2007 |
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60941908 |
Jun 4, 2007 |
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60978828 |
Oct 10, 2007 |
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Current U.S.
Class: |
420/436 ;
420/588 |
Current CPC
Class: |
B33Y 70/00 20141201;
C22C 1/06 20130101; A61K 6/844 20200101; C22C 19/07 20130101; C22C
30/00 20130101; A61C 13/0003 20130101 |
Class at
Publication: |
420/436 ;
420/588 |
International
Class: |
C22C 19/07 20060101
C22C019/07; C22C 30/00 20060101 C22C030/00 |
Claims
1. A non-magnetic dental alloy comprising cobalt and further
comprising: at least 25 wt. % of a first material selected from the
group consisting of palladium, iridium, osmium, ruthenium,
platinum, rhodium, gold, and combinations thereof; 0 to 20 wt. % of
a second material selected from the group consisting of molybdenum,
tungsten, tantalum, niobium, rhenium, and combinations thereof; and
15 wt. % to 35 wt. % chromium; wherein palladium comprises a
majority of the first material; and wherein the dental alloy is
non-magnetic.
2. The dental alloy of claim 1, wherein the concentration of the
second material is dependent on the concentration of chromium in
accordance with the following: where chromium is at least 20 wt. %
then the second material is from 0 to 20 wt. %, and where chromium
is less than 20 wt. % then the sum of chromium and the second
material is greater than 20 wt. %.
3. The dental alloy of claim 1, wherein palladium is at least 24
wt. %.
4. The dental alloy of claim 1, comprising 30 wt. % to 60 wt. %
cobalt.
5. The dental alloy of claim 1, wherein the alloy further comprises
up to about 5 wt. % of at least one additive material selected from
the group consisting of aluminum, boron, cerium, gallium,
germanium, silicon, and combinations thereof
6. The dental alloy of claim 5, wherein the at least one additive
material is selected from the group consisting of up to 2 wt. %
gallium, up to 3 wt. % silicon, up to 1 wt. % boron, up to 3 wt. %
aluminum, up to 3 wt. % germanium, up to 1 wt. % cerium, and
combinations thereof.
7. The dental alloy of claim 1, wherein the alloy further comprises
less than 5 wt. % of at least one trace additive selected from the
group consisting of copper, nickel and iron.
8. The dental alloy of claim 1, wherein the sum of chromium and the
first and second materials is from 45 wt. % to 70 wt. %.
9. The dental alloy of claim 1, wherein the alloy has a thermal
expansion coefficient from about 13 to about
18.times.10.sup.-6.
10. The dental alloy of claim 1, wherein the alloy has a liquidus
temperature of below about 1350.degree. C.
11. A dental product comprising: a body for dental application,
said body being formed of a non-magnetic dental alloy comprising
cobalt and further comprising: at least 25 wt. % of a first
material selected from the group consisting of palladium, iridium,
osmium, ruthenium, platinum, rhodium, gold, and combinations
thereof; 0 to 20 wt. % of a second material selected from the group
consisting of molybdenum, tungsten, tantalum, niobium, rhenium, and
combinations thereof; and 15 wt. % to 35 wt. % chromium; wherein
palladium comprises a majority of the first material; and wherein
the dental alloy is non-magnetic.
12. The dental product of claim 11, wherein the concentration of
the second material is dependent on the concentration of chromium
in accordance with the following: where chromium is at least 20 wt.
% then the second material is from 0 to 20 wt. %, and where
chromium is less than 20 wt. % then the sum of chromium and the
second material is greater than 20 wt. %.
13. The dental product of claim 11, wherein palladium is at least
24 wt. %.
14. The dental alloy of claim 11, comprising 30 wt. % to 60 wt. %
cobalt.
15. The dental product of claim 11, wherein the alloy further
comprises up to about 5 wt. % of at least one additive material
selected from the group consisting of aluminum, boron, cerium,
gallium, germanium, silicon, and combinations thereof.
16. The dental product of claim 15, wherein the at least one
additive material is selected from the group consisting of up to 2
wt. % gallium, up to 3 wt. % silicon, up to 1 wt. % boron, up to 3
wt. % aluminum, up to 3 wt. % germanium, up to 1 wt. % cerium, and
combinations thereof.
17. The dental product of claim 11, wherein the alloy further
comprises less than 5 wt. % of at least one trace additive selected
from the group consisting of copper, nickel and iron.
18. The dental product of claim 11, where the sum of chromium and
the first and second materials is from 45 wt. % to 70 wt. %.
19. The dental product of claim 11, wherein the alloy has a thermal
expansion coefficient of from about 13 to about
18.times.10.sup.-6.
20. The dental product of claim 11, wherein the alloy has a
liquidus temperature of below about 1350.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 12/050,006, filed Mar. 17, 2008, which claims priority to U.S.
Provisional Application No. 60/896,182, filed Mar. 21, 2007, U.S.
Provisional Application No. 60/941,908, filed Jun. 4, 2007, and
U.S. Provisional Application No. 60/978,828, filed Oct. 10, 2007,
the disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The current invention is directed to an improved dental
alloy, and more specifically to a non-magnetic cobalt based dental
alloy containing at least 25% palladium, and where the combined
concentration of chromium, molybdenum, tungsten, niobium, tantalum
and rhenium is sufficient to ensure a non-magnetic material.
BACKGROUND OF THE INVENTION
[0003] Dental alloys employed in the porcelain-fused-to-metal
processing technique may be classified into several groups,
including gold based, palladium based, cobalt based, and titanium
based. One of the most important criteria in deciding which alloy
to use is the cost of the alloy. The cost of the alloy is dependent
upon the commodity prices of the alloy components. For example, in
March 2007, the cost of the major components of each the above
alloys was: [0004] Gold $730 per Troy ounce, [0005] Palladium $350
per Troy ounce, and [0006] Cobalt $2.23 per Troy ounce.
[0007] The economic advantage of the base metal cobalt is obvious,
but the functional characteristics of base metal alloys do not
compare with those of gold based or palladium based alloys, and for
this reason they are not generally used in dental products. For
example, in general cobalt base metal alloys are more difficult to
cast, grind and bond to porcelain.
[0008] There have been numerous attempts to improve the functional
characteristics of cobalt based alloys through the addition of gold
and the platinum group metals (the platinum group metals consist of
platinum, palladium, rhodium, iridium, osmium and ruthenium).
Examples from the prior art are listed in Table 1, below.
TABLE-US-00001 TABLE 1 SUMMARY OF PRIOR ART Author U.S. Pat. No.
Comments Prosen 4,253,869 Describes a cobalt chromium alloy with 7
to 15 wt. % ruthenium. Prosen 4,255,190 Describes a cobalt chromium
alloy with 7 to 15 wt. % ruthenium with gallium. Zwingmann
4,382,909 Describes a cobalt chromium alloy that with 1 to 70 wt.%
palladium. Prasad 4,459,263 Describes a cobalt chromium alloy with
5 to 15 wt. % ruthenium. Vuilleme 6,613,275 Describes a cobalt
chromium alloy with 0.5 to 4 wt. % gold. Prasad 6,656,420 Describes
an alloy with 25 to 60 wt. % gold and up to 2 wt. % ruthenium
balance cobalt. Prasad 6,756,012 Describes a cobalt chromium alloy
with up to 20 wt. % platinum or palladium, up to 10 wt. % gold and
up to 6 wt. % ruthenium.
[0009] In each case, some improvement in the functional
characteristics of the base metal alloy has been achieved through
the addition of gold and/or the platinum group metals. However, to
date no successful commercial formulation of a cobalt based high
palladium content alloy has been obtained that is consistent with
the American Dental Association (ADA) guidelines for "noble" alloys
required for use in dental products (i.e. alloys having at least
25% gold or palladium).
[0010] For example, although the Zwingmann patent discloses a wide
range of possible cobalt based palladium alloys, most of these have
strong magnetic properties. Likewise, Ivoclar Vivadent, Inc.
manufactures a cobalt based high palladium content alloy sold under
the tradename Calisto CP, which has a composition of 56 wt. %
cobalt, 30 wt. % chromium, 26.2 wt. % palladium, 3 wt. % tungsten
and 2 wt. % gallium. However, this alloy is also strongly magnetic
and therefore poses potential problems for use in dental
applications. Specifically, magnetic dental inserts and appliances
can make it difficult if not impossible to use advanced imaging
techniques such as Magnetic Resonance Imaging (MRI) on patients. In
addition, such magnetic materials can cause false positives when
individuals are scanned during security check-ins (for example, at
airports). Accordingly, a need exists for improved cobalt based
"noble" dental alloys that possess non-magnetic properties.
SUMMARY OF THE INVENTION
[0011] The invention is directed to improved cobalt based palladium
containing alloys that are rendered non-magnetic through the
additions of higher concentrations of other alloying elements.
[0012] In one embodiment, an exemplary cobalt based alloy in
accordance with the current invention has the following
composition: at least 25 wt. % palladium and 15 to 30 wt. %
chromium, where either at least 20 wt. % of the alloy must be
formed of chromium, or if the concentration of chromium in the
alloy is less than 20 wt. % then the total combination of additive
materials selected from the group consisting of chromium,
molybdenum, tungsten, niobium, tantalum, vanadium and rhenium must
be greater than 20 wt. %. An alternative statement of this
composition can take the form of the following equation:
Co.sub.1-y(Pd.sub.aCr.sub.bX.sub.c).sub.y
[0013] where X is a material selected from the group consisting of
chromium, molybdenum, tungsten, niobium, tantalum, vanadium and
rhenium; where y is at least 45 wt. %; and where a is at least 25
wt. %, b is from at least 15 wt.% to 30 wt. %, and c is dependent
on the concentration of b in accordance with the following: where b
is at least 20 wt. % then c is from o to 20 wt. %, and where b is
less than 20 wt. % then the sum of b and c is greater than 20 wt.
%. In an alternative of such an embodiment, y may range from at
least 45 wt. % to 70 wt. %.
[0014] In another embodiment, an exemplary alloy in accordance with
the current invention is formed having the following composition:
cobalt 44.75 wt. %, chromium 20 wt. %, palladium 25 wt. %,
molybdenum 10 wt. % and boron 0.25 wt. %.
[0015] In still another embodiment, the alloys in accordance with
the current invention may be modified with gallium up to 2 wt. %,
and/or silicon up to 3 wt. %, and/or boron up to 1 wt. %, and/or
aluminum up to 3 wt. %, and/or germanium up to 3 wt. %, and/or rare
earth elements such as cerium up to 1 wt. %.
[0016] In yet another embodiment, the alloys in accordance with the
current invention may include traces amounts of other compatible
materials, such as, for example, nickel, iron and copper.
[0017] In still yet another embodiment, indium and tin may be used
to substitute for other deoxidizing elements such as, for example,
gallium and aluminum.
[0018] The alloys in accordance with the current invention may be
cast and processed using standard dental laboratory equipment and
materials. Furthermore, they are also suitable for use with newer
CAD/CAM and powder metallurgical applications where no casting is
required.
BRIEF DESCRIPTION OF THE FIGURES
[0019] The above-mentioned and other features of this invention and
the manner of obtaining and using them will become more apparent,
and will be best understood, by reference to the following
description, taken in conjunction with the accompanying FIGURES.
The FIGURES depict only typical embodiments of the invention and do
not therefore limit its scope, wherein:
[0020] FIG. 1 provides a table (referenced hereinafter as Table 3)
containing a listing of exemplary alloy compositions in accordance
with the current invention and their properties, as well as alloy
compositions outside of the compositional ranges of the current
invention for comparison purposes.
DETAILED DESCRIPTION OF THE INVENTION
[0021] This invention provides a non-magnetic cobalt based dental
alloy capable of meeting the ADA requirements for a "noble" alloy
that comprises at least 25 wt. % palladium and an additive of at
least 15 to 30 wt. % chromium, where either at least 20 wt. % of
the alloy is chromium, or if the concentration of chromium is less
than 20 wt. % then the total combination of additive materials
selected from the group consisting of chromium, molybdenum,
tungsten, niobium, tantalum, vanadium and rhenium must be greater
than 20 wt. %.
[0022] As used herein, the term "non-magnetic" refers to materials
that possess only diamagnetic properties, that is, that demonstrate
neither ferromagnetic nor paramagnetic properties.
[0023] The inclusion of at least 25 wt. % palladium in the cobalt
based dental alloy of the current invention has both metallurgical
and economic benefits. Consider the price of gold and the platinum
group metals: [0024] Rhodium $6,200 per Troy ounce, [0025] Platinum
$1,360 per Troy ounce, [0026] Ruthenium $530 per Troy ounce, [0027]
Gold $730 per Troy ounce, [0028] Iridium $450 per Troy ounce,
[0029] Osmium $400 per Troy ounce, and [0030] Palladium $350 per
Troy ounce.
[0031] Based on this pricing, palladium is by far the lowest
costing element of the group so it is an economic advantage to
utilize palladium in place of gold and other platinum group
elements in the fabrication of a "noble" alloy.
[0032] From a metallurgical perspective, palladium and cobalt are
completely soluble in each other. Palladium also substitutes for
molybdenum, tungsten and chromium in cobalt based alloys, allowing
for the use of lower chromium concentrations. Palladium is also
very effective in lowering melting temperature, acts as an alloy
strengthener, is a thermal expansion adjuster for the alloys, and
improves the alloys' oxidation and corrosion resistance. However,
thus far a non-magnetic cobalt based alloy containing at least 25
wt. % palladium has not been formulated that meets all of the
requirements for use in dental products. In the current invention,
a non-magnetic low chromium cobalt-palladium alloy has been
formulated that meets the requirements for use in dental alloys.
The alloy has the following general composition [0033] 15 to 30 wt.
% chromium; [0034] from 0 to 20 wt. % molybdenum and/or tungsten,
tantalum, niobium, vanadium and rhenium; [0035] at least 25 wt. %
palladium; and [0036] the remainder cobalt; [0037] where to obtain
the non-magnetic properties necessary for dental applications
either the concentration of chromium must be at least 20 wt. % or
the where the concentration of chromium is less than 20 wt. % then
the combined concentration of chromium, molybdenum, tungsten,
niobium, tantalum, vanadium and rhenium in the alloy must be
greater than 20 wt. %.
[0038] Although not specified in the above formulation of the
alloy, it should be understood that in a preferred embodiment the
alloy contains a minimum concentration of cobalt of at least 30 wt.
%.
[0039] The alloy may also include other additives to improve
specific properties, such as the casting or grain refinement
properties. These additional materials include gallium, silicon,
boron, germanium, aluminum and cerium in concentrations of up to
5.0 wt. %. More specifically, the concentration compositional
ranges of these additional materials are: gallium up to 2 wt. %,
and/or silicon up to 3 wt.%, and/or boron up to 1 wt. %, and/or
aluminum up to 3 wt. %, and/or germanium up to 3 wt. %, and/or
cerium up to 1 wt. %.
[0040] Exemplary compositional ranges for alloys contain these
additional additives are provided in Table 2, below:
TABLE-US-00002 TABLE 2 EXEMPLARY ALLOY COMPOSITIONAL RANGES Element
Min Best Max Co bal bal bal Cr 15 20 30 Pd 25 25 30 Mo and/or W,
Ta, Nb, V, Re 0 10 20 Al 0 0.5 3 B 0 0.25 1 Ce 0 0.25 1 Ga 0 1 5 Ge
0 1 3 Si 0 0.5 3
[0041] The palladium content of at least 25 wt. %, and palladium's
general enobling effect, can in some embodiments reduce the need
for large additions of other materials such as chromium,
molybdenum, tungsten, etc. However, key to the current invention is
the requirement that the material as formed be non-magnetic. The
inventors of the current invention have discovered that alloying
cobalt with palladium and chromium within certain weight
percentages, and optionally with the addition of molybdenum,
tungsten, niobium, tantalum, vanadium, rhenium or other suitable
elements in specific amounts, renders these alloys nonmagnetic.
Specifically, it has been discovered that where the alloy has a
content of chromium of at least 20 wt. %, or where the alloy has a
content of chromium of at least 15 wt. % and the combined
concentration of chromium, molybdenum, tungsten, or other suitable
additive materials is greater than 20 wt. %, a non-magnetic
cobalt-palladium alloy may be reliably formed. The properties and
compositions of exemplary alloys formed in accordance with the
current invention, including an example outside the compositional
ranges of the current invention for comparison, are provided in
Table 3 in the attached FIGURE.
[0042] As shown in Table 3, alloys formed in accordance with the
present invention exhibit non-magnetic properties as previously
discussed; however, they also exhibit a wide variety of other
physical properties that make them particularly promising for use
in dental applications. For example, the alloys show liquidus
temperatures below 1400.degree. C. (typically below 1350.degree.
C.), which makes them adaptable for use with all standard casting,
molding and shaping processes, as well as with new non-casting
procedures. In addition, the alloy compositions of the current
invention can be ground using traditional dental laboratory
grinding media, making the alloy suitable for use with newer
CAD/CAM and powder metallurgical applications where no casting is
required. Substrates or final restorations can be milled from
blocks made from these alloys. As powders, these alloys can be used
either to create three dimensional performs utilizing appropriate
binders and then be sintered or directly be sintered/melted such as
for example, with a laser, to create substrate or final
restoratives. Exemplary disclosures of such processes can be found,
for example, in U.S. Pat. Nos. 7,084,370 and 6,994,549, the
disclosures of which are incorporated herein by reference. It
should be understood that while some prior art laser sintering
techniques specify a specific range of useable alloy particulate
sizes, the alloys of the current invention are contemplated for use
in laser sintering techniques over all possible particulate size
ranges.
[0043] Also, as shown in Table 3, in addition to the improved
castability of these materials, the alloys show a wide variety of
thermal expansion coefficients, namely from about 13 to about
18.times.10.sup.-6 (as measured from about 25 to 500.degree. C.).
Because of the wide range of thermal expansion coefficients
accessible by these materials, they can be used with all standard
porcelains on the marketplace, such as, for example, high fusing
conventional porcelains that have thermal expansion coefficients
from about 13 to 15.times.10.sup.-6, and low fusing porcelains that
have thermal expansion coefficients from about 15 to
16.times.10.sup.-6.
[0044] In addition to the main components, as previously discussed
the alloys of the current invention may also contain concentrations
of other additives to improve specific properties. For example,
small concentrations (up to .about.5 wt. %) of gallium, silicon,
boron, aluminum, germanium and cerium can serve to deoxidize, lower
the melting range, and improve the castability of the alloys.
Specifically, the addition of gallium can lower the melting range
of the alloy so that the material can be cast with a gas-oxygen
torch. Alternatively, small silicon and boron additions can also be
used to improve the alloy's thermal expansion and castability.
However, it should be understood that these additives are not
essential to the practice of the current invention. For example, if
the alloy is to be cast by induction heating, then the melting
range can be higher eliminating the need for any of these
additives. Regardless, based on its castability and non-magnetic
properties, one particularly preferred non-magnetic alloy in
accordance with the current invention is formed having the
following composition: cobalt 44.75 wt. %, chromium 20 wt. %,
molybdenum 10 wt. %, palladium 25 wt.%, and boron 0.25 wt. %.
[0045] It is appreciated that the above compositions suitable for
use with dental appliances are not exclusive. Those of skill in the
art will be aware that some of the materials can be substituted or
additional materials may be added without altering the key
properties of the alloys of the current invention. For example, it
is well known that small amounts of cobalt and palladium can be
substituted with copper, nickel and iron. Alternatively, small
concentrations (less than 5 wt. %) of these materials may also be
added or be found in the alloy as impurities without affecting the
properties of the overall composition.
[0046] To prove the utility of these alloys for dental products,
exemplar compositions were successfully bonded to several popular
dental porcelains. The inventors have fully tested the utility of
the materials for dental applications by fabricating both single
crowns and bridgework. In addition, they have shown that alloys in
accordance with the invention can be processed using standard
foundry processing techniques for cobalt alloys, indicating that
the alloys of the invention will be useable with typical mass
production casting and/or molding techniques.
[0047] Finally, biological testing has been completed on ruthenium
containing alloys in the past and has determined alloys of this
type to be non-cytotoxic. Although similar cytotoxicity tests have
not been completed for the alloys of the current invention, ion
release tests have been conducted for exemplary alloys, as shown in
Table 3. The results show that the alloys of the current invention
have very low ion release when subjected to immersion tests of the
ISO standard. These low ion release rates suggest that not only
will the alloys of the current invention be non-cytotoxic, but that
they also possess very high electrochemical resistance, which is
important in the oral environment.
[0048] Although the above description has focused on a range of
compositions for the alloys of the current invention, the invention
is also directed to a method of manufacturing a dental product
generally comprising the steps of providing an alloy having a
composition in accordance with the above description and then
shaping that alloy using any suitable means. As discussed above,
the alloy of the instant invention allows for the use of a number
of conventional shaping techniques, such as, casting and molding.
Moreover, the alloys of the current invention also allow for the
use of more recent advances in shaping technologies, such as, for
example, selective laser sintering. It should be understood that
any of these techniques or a combination thereof may be used with
the alloys of the current invention.
[0049] Those skilled in the art will appreciate that the foregoing
examples and descriptions of various preferred embodiments of the
present invention are merely illustrative of the invention as a
whole, and that variations in the relative composition of the
various components of the present invention may be made within the
spirit and scope of the invention. For example, it will be clear to
one skilled in the art that typical impurities and/or additives may
be included in the compositions discussed above that would not
affect the improved properties of the alloys of the current
invention nor render the alloys unsuitable for their intended
purpose. Accordingly, the present invention is not limited to the
specific embodiments described herein but, rather, is defined by
the scope of the appended claims.
* * * * *