Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
lOSZ598
This invention relates to dental alloys and dental
constructions fabricated from such alloys.
The alloys are particularly suitable for use in the
preparation of bridges, crowns and the like and for dental
applications generally where a workable metal having good physi-
cal strength, corrosion resistance and ability to bond to
porcelain are required. The dental alloys have a base cost of
substantially less than gold but are equal to or better than
gold for many dental applications the same also being use~ul
where veneering is employed, of either plastic or porcelain to
metal and in the preparation of metal inlays and onlays.
The dental alloys are composed primarily of nickel,
chromium and silicon and contain, on a weight percent basis, 65
to 75% nickel, 15 to 23.5% chromium and 3.5 to 6.0% silicon. In
one embodiment, the alloy may contain 15 to 20% chromium. In the
preferred alloy compositions, small amounts of molybdenum are
also included either alone or together with boron or manganese.
Where used, the molybdenum is present within the range of 3.0
to 5.0%. Where manganese is used with the molybdenum, it is
present in amounts of up to 1% and where boron is used with
the molybdenum, it is used in amounts of 0.2 to 2.0%.
The percentages, where given, are percent by weight
based on the total amount of nickel, chromiumi silicon,
molybdenum, manganese and boron present in the alloy. The
alloys have excellent physical properties for dental application
the same having a fusion temperature within the range of 2250
to 2350F., good corrosion resistance as compared to similarly
cast gold or other commercial nonprecious metal dental alloys
and good oxidation resistance. They also have as casted a
tensile strength of at least 90,000 p.s.i., an elongation of
- 1 -
lO5Z598
about 0.5 to 5.0% and a Rockwell B hardness within the range of
about 94 to 110.
According to the invention, there is provided a
dental alloy consisting essentially of, on a percent by weight
basis, 100 to 90% nickel, chromium and silicon in amounts Qf
65 to 75% nickel, 15 to 23.5% chromium, and 3.5 to 6.0~/o
silicon in the absence of beryllium and 1.5 to 6.0% silicon
in the presence of beryllium, 0 to 1.5% beryllium, 0 to 5.0%
molybdenum, 0 to 2.0% boron and 0 to 1.0% manganese, said
alloy having a fusion temperature within the range of 2250
to 2350F., a tensile strength of at least 90,000 p.s.i., and
the ability to bond well to dental porcelains.
According to another aspect of the invention, there
is provided a dental construction comprising a rigid metal
body formed of a dental alloy of the invention, having bonded
thereto material simulating tooth enamel in appearance.
:- - 2 -
.~,
105Z598
PROBLEMS IN THE PRIOR ART
AND OBJECTS OF THE INVENTION
Gold has been ~sed for many years as the basic structural
metal ln dentistry for the preparlng o~ teeth, bridges,
crowns and the llke. Because of its high cost, many attempts
have been made to make nonprecious metal alloys which
could be used in place of the gold. Such compos~tions
are illustrated, for example, by the patents, U.S.
No. 1,736,053; 2,089,587; 2,156,757; 2,134,423; 2,162,252;
2,631,095; 3,121,629; 3,464,817 and 3,544,315. Gold,
however, has many advantageous properties where used as
a dental alloy and many of the nonprecious metal alloys
which have heretofore been prepared have proved to be
unsatisfactory from various aspects particularly when
compared to the conventionally used gold metal.
One of the problems encountered where attempt~
have been made to prepare nonprecious alloys to be used
for dental work in place of gold is that many of these
alloys have been hard to cast because the melting rPnge
has been too high. In order to be accepted generally by
dental laboratory technicians the melting temperature of
the alloy should not be much in excess of 2400F. and
should preferably be within the range Or about 2200 to
2350F. A practical reason for this is that many dental
laboratories use torches of the gas oxygen type which will
not heat to much above 2500F. so that lf higher melting
alloys are used then special heating equipment such as
oxygen-acetylene torches must be obtained for working the
metal.
Another problem with many of the heretofore generally
known nonprecious metal dental alloys is one of corrosionO
CER. 11
~o5zs98
The alloys generally are not as reslstant as gold wlth
respect to corrosion ln mouth acids. It has, ror
example, been proposed to add berylllum to lower the
fuslon temperature Or dental alloy~. However~ the
result has rrequently been to still further reduce the
res$stance to corrosion of the resulting nonpreciouæ
metal alloy. A stlll further problem experlenced in
attempts to make nonprecious metal dental alloys is that
the alloys cause porcelains to discolor when the
L0 porcelain 18 fused to the metal base ln the preparation
i o~ porcelain Jackets, crowns, bridges, and the like. Thus,
~or example, where cobalt or copper are included in the
alloy ln any appreciable amount the same tend to discolor
the porcelain when rused to the nonprecious metal alloy.
.5 A still further serlous obJection to the generally available
nonprecious metal alloys prepared for dental application is
that these nonprecious metal alloys cannot be soldered readily
to themselves or to gold by using the conventlonal dental
solders which are readi~y available to and used by dental
laboratory personnel. Also, nonprecious metal dental alloy
materials heretofore designed for use as ~tructural metals
ln place Or gold are frequently found to be substantially
h~der than gold with the result that greater time and effort
are necessary for grinding the metals for prec1se fit after
casting the same.
CE;R. 11
1 05 ~5 9 8
The present lnvention ls dlrected to nonpreclous met~l
dental alloys and the preparation of the s~me which are
free from the ob~ectlons mentioned above. The preparation
of such a nonprecio~s metal dental alloy is one of the
ob~ects of the present invention. Another object is to
prepare a nonprecious metal dental alloy which not only
uses materials which are substantially less costly than gold
but which also has other advantages over gold where used as
a structural metal for dental application. A still further
ob~ect is the preparation of nonprecious metal dental
alloys that can be used by dental laboratory personnel in
place of gold without the necessity of appreciably changing
presenttechniques or equipment presently used when working
with gold.
The nonprecious metal dental alloys of the present
invention, although not quite as corrosion resistant as
gold, have excellent corrosion resistance properties closely
approaching that of gold and are substantially more corrosion
resistant than the nonprecious metal dental alloys generally
avallable. In use, for many appllcations, the nonprecious
metal dental alloys of the present lnvention are superior to
gold in that they are substantially lighter than gold but
3tlll have a higher tensile strength than gold. Alsos
the dental alloys of the present invention are slightly
harder than gold but not suff~ciently hard to cause any
appreciable difficulty in grinding. Also, the dental alloys
of the present invention have the property that the same can
be recast without apparently in any way a~ecting their
mechanical properties, properties of soLdering and corrosion
resistance.
l~SZ598
It has now been discovered that the heretofore
mentioned problems can be avoided and the heretofore men-
tioned objects accomplished by preparing dental metal alloys
from nickel, chromium, and silicon in the proportions and
manner hereinafter more fully described with the preferred
alloys also containing small amounts of molybdenum together
with boron or manganese.
The alloys of the present invention contain 65
to 75 percent nickel, 15 to 23.5 percent chromium and 4 to
5,5 percent silicon. The preferred compositions also con-
tain 3.0 to 5.0 percent molybdenum together with boron or
manganese with the boron being present in amounts of 0.5
to 2.0 percent and the manganese being present in amounts
up to 1.0 percent.
All percentages are on a weight basis, based on
the total nickel, chromium, silicon, molybdenum, boron and
manganese content in the alloy. These alloys have a fusion
temperature within the range of 2250 to 2350F,, good
corrosion resistance, good oxidation resistance, a tensile
strength of at least 90,000 psi, a percent elongation of
about 0.5 to 5.0 and a Rockwell B hardness within the range
of about 94 to 110.
The dental alloys of the present invention are
ideal for use as a structural metal in doing dental work,
They have a fusion temperature within the range in which
dental laboratories are usually accustomed to work and for
which they are generally equipped. They bond readily to porce-
lain without staining or straining and have a coefficient of
expansion such that the bond is maintained. They can be
CER. 11
1~5'~5g8
used with the dental solders presently generally employed
by dental laboratory technlcians when working with gold.
They can also be remelted a~d cast without loss of thelr
excellent physical properties. As to their physical
propertles, they have good strength, hardness and corros~on
and oxidation resistance, while being llghter, stronger,
and harder than gold. They can be used in place of gold for
most dental applicatlons. They are deslgned to be used where
gold is presently employed and can be soldered, ground and
worked in the s~me manner as gold requir$ng no change in
equipment or technique.
It is recognized that the term good is relative, but
as u~ed herein it means good for the purposes of use in
dentistry ~or whlch the material is specified. Thus good
corroæion resistance would be resistance to etching by
hydrochloric acid superior to that shown by pre~ently
commercially available nonprecious metal dental alloys and
resistance to etching with NaCl aqueous solution c~mparable
to that shown by conventionally used dental gold alloys.
Also~ good oxldation resistance would be ~uch that the surface
of the metal would not oxidize during working to the degree
that the same could not be readily bonded to p~rcelain. A
good strength and hardness would be a tensile strength and
hardness above that of the gold alloys presently available
with the hardness being pre~erably below about 120 Rockwell B
80 that the ca~ting~ can be readily ground for rinishing.
Gold alloy~ presently used have a tensile strength o~ about
6s,ooo p~i and a Rockwell B hardness of about 86.
,, , . CER. 11 .
105ZS98
Good dental alloys have been prepared ln accordance
wlth the present lnvention which contaln essentl~lly only
nlckel, chromlum and sllicon in proportions within the
range indicated. Suc~ an alloy, rOr example, 18 a nickel,
chromium, sillcon dental alloy containing 71.4~ nickel,
23.2% chramium and 5% ællicon. These alloys, however, can
be improved ln their corrosion resistance and their ability
to bond to porcelain by lncluding small amounts of molybdenum
either alone or together with boron or manganese. The boron
` 10 containing preierred composltions are those consisting
essentlally of 67 to 74% of nlckel, lô.5 to 23.5% chrom~um,
4.0 to 5.5~ sllicon, 4.0 to 4.5~ molybdenum and 1 to 1.5%
boron and the manganese containing preferred compositions
wo~id be those consistlng essentlally of 67 to 74~ nickel,
18.5 to 23.5% chromlum, 4.0 to 5.5% sllicon, 4.0 to 4.5%
molybdenum and .5 to 1.0% manganese.
Although small amounts of molybdenum may be lncluded
alone with the baslc nlckel, chromlum, sllicon alloy metal,
the molybdenum 18 prererably used to~ether with elther the
manganese or boron. The manganese should, howe~er, not be
lncluded ln the alloy without some molybdenum belng present
as lt will otherwise tend to decrease the corrosion resistance.
Also, the boron,where molybdenwm 18 not present, should not
generally be included in amounts in excess Or about 2% by
welght of the total alloy compositlon.
.....
CER. 11
105Z598
Inclusion oi the boron or manganese together with the
molybdenwm in the alloy compositions Or the present invention
also improves somewhat the bonding strength between the alloy
and porcelain where porcelain ~s ~used to the alloy such~ ior
example, as in the pFeparation of ~ackets, crowns, bridges, and
the like.
The addition of the molybdenum alone to the nickel,
chromium and æilicon has little bene~icial erfect on bonding;
but as previously indicated, the corrosion resistance is
improved. Where added together with the boron or manganese
other physical properties of the alloy are also improved.
As previously indicated, the sllicon is generally present
ln the range of about 4.0 to 5.5. Where used in amounts
much below 4.~%, the fusion temperature of the alloy is found
to be above 2400F., which is generally too high, as previously
indicated. When the silicon content is increased to much above
5.5% the alloy tends to become too brittle and the mechanlcal
strength drop~. The silicon content can be reduced to below
the 4.0% without appreciably raislng the iusion te~perature
o~ the alloy if small amounts oi beryllium are added. Howevcr,
the additlon Or beryllium is generally undeslrable as berylliu~
18 considered by many to be a toxic metal and should, thereiore,
preferably not be lncluded in an alloy to be used in dental
work partlcularly where the alloy ~ay be used in de~tal
laboratories not equipped wlth adequate exhaust ventllation.
.
_g_
CER. 11
1 OSZ598
If berylllum i~ adde~ to the alloy, however, the lower
limlt of the silicon could be decreased to as low as
1.5% while stlll maintaining the fusion temperature of
the alloy below 2400F. The addition of berylllum,
however, is al80 generally ob~ectlonable in that it has a
tendency to form a eutectic with the sllicon which
eutectic has a relatlvely low meltlng point and is apt
to cause gassing where the alloy 18 heated while under
vacuum, a condition encountered in the preparation of
porcelain crowns and bridges. Accordingly, l~ beryllium
is used in the alloy it should only be used in small amount6
generally within the range o~ about 0 to 1.5% by weight as
based on the total weight of the nlckel, chromium, silicon,
manganese and molybdenum present.
When the chronium content with respect to the nlckel
i8 permitted to become too high, the thermal expansion of
the alloy is ~ound to be too low to obtain good matching
wlth porcelaln. Where the chramium content becomes too low
the alloy is generally found to have substantially poorer
oxldation and corrosion resistance than i~ deslrable.
The dental alloy compositions of the pre~ent invention
can contain small amounts of other materlals such as
tit~nium, tin, zinc, magnesium and aluminum. However~ where
present tltanlwm should not be present in amounts greater
than about 1%, tin and aluminum in amounts greater than about
2%, zinc in amounts greater than about 0.4~ and ~agneslum
in amount6 greater than about 0.5%~ None Or the3e are
.
~ .
-10-
CER. ll
lO~Z598
consldered, however, a~ essential materlals in the dental
alloy composltions of the present inventlon and may or
may not be included as indlcated. Accordingly, the alloy
compositlons of the present inventlon consist essentially,
as heretofore indicated~ of nickel, chromium and silicon
ln the proportions speclfied and in the preferred compositlons
of nickel, chromium, silicon and molybdenum with boron or
manganese.
The dental alloys of the present in~ention have many
uses includ~ng the replacement of the heavier and more
expenslve gold which has been t~e conventional structural
metal used for dental purposes. The alloys are ideally
suited for use where bonding of the alloy to a porcelaln
le required, as in the preparation of artificial teeth,
crowns, bridges and the like. The alloy may al~o be u~ed
ln the preparation of veneers, both plastlc as well as
porcelain. Their physlcal propertles al~o make the alloyfi
hlghly useful for the preparation of metal crowns where the
metal acts to c~mpletely cover the prepared tooth and for
the preparation of lnlays and onlays. In auch ufiage the
dental alloys of the present lnvention are found to be not
- only as good a~ the gold which has heretofore been used but
ln many respects superior to such gold.
The practice of the inventlon i~ further illustrated
by the following examples which are gi~en for the purpose
Or illu~tration only, the ln~ention not to be llmited th~reto.
~ .
c~
105i~598
EXAMPLE 1
.
Into a fused alumlna crucible, 1~ added 1.4 gr~ms
o~ boron powder, 4.1 gram~ of particulated sllicon in
the form of small blocks, 4.2 grams of molybdenum and
19.O grams o~ chromlum in plate form. There ls then
added 71.3 grams of nickel shot. The cruclble ls then
heated by inductlon heat in an argon atmosphere to prevent
oxidatlon. The c-ontents are broug~t to a temper&ture of
about 1600C. The melt is then permitted to cool to about
500C. at which time t~e solid alloy i8 removed.
Test bars of this alloy are cast and are found to
have an Ultimate Tensile Strength of 132,000 pounds per
square inch, a Yielding Strength Or 110,000 pound~ per
square inch, a Modulus of Elasticity of 25X106 per square
lnch, a perce~t of Elongation of 1.45% and a Rockwell B
hardness of 106 RB . The alloy also has a Thermal Expan~ion
Coefficient of 79x10-6 in/inC, a mel~lng temperature within
the range of 2250 to 230Q F, and a casting tamperature Or
24OoF.
Portions of the alloy prepared in the abo~e manner
are tested for its castlng characterlstics UBing standard
Lost Wax Technlque casting procedures. The alloy 18
found to cast well.
Using standard techniques, portion~ Or the alloy are
used ln the preparation of metal crowns and bridges; and
porcelaln bonded crown~ and bridges where the porcelain
18 fused to the metal. No dlscoloration Or porcelaln 18
obserYed and good bonding is obtalned.
-12-
, _ .,_ .. . ...
OE R. ll
1[)5;~598 -
The alloy m~y also be u~ed for plastlc bonded crowns
and brldges using the c~nventlonal techniques employed in
maklng the same.
When working the alloy, it i8 preferred to use an
oxygen-gas flame for meltlng rather than an oxygen-acetylene
flame although the latter ~an be employed if care i8 taken.
EXAMPLE 2.
Employlng the same tec~nique as described in Example l,
a dental alloy 18 prepared having the cGmposltion in, percent
by weight,of: Nickel 67.8
Chromium 22.0
- Molybdenum 4.2~
Sllicon 5.0%
Manganese 1.0%
This alloy has an Ultimate Tenslle Strength of 118,500
pounds per square lnch, a Yieldlng Strength of 8s,ooo pounds
per square lnch, a Modulus of Elastlcity Or 24X106 per sguare
lnch, a percentage Or Elongation of 3.5% and a Rockwell B
hardne88 Or 98 ~B
The alloy i8 ~180 found to cast well uslng the Lo~t
Wax Technique ~nd ~ound to handle well in the preparation Or
metal crowns and brlages, porcelain bonded crowns and brldges,
the preparatlon of lnlays and onlays, and in the preparation
o~ plastlc bonded crowns and bridges~ No staining 18 noted
Or the porcelaln wh~re porcelain and mQtal b~nds are made.
Al~o, excell~nt bond etrengths are obtalned.
~r
-13-
CER. 11
, 1~5Z5~8
. . 1~
Using the technlque deccrlbed ln Example 1 a
dental alloy compositlon i8 prepared comprising:
71.4~ Nickel
23.2% Chromlum
5.0% Silicon
0.4~ Boron
Thls alloy has an Ultimate T~nsile Strength o~
107,000 pounds per square lnch; a Yielding Strength of
75,000 pounds per square lnch; a Modulus of Ela~ticlty Or
23X106 pound~ per square inch, a percentage o~ Elongatlon
Or 3.2~, and a Rockwell B hardness of 95 RB .
: The alloy is cast uslng the Lo~t Wax Technlque, the
alloy handles well when used in the preparatlon Or metal
crowns and bridges, porcelain crown~ and bridges, lnlay and
onlays and in the preparation Or plastic bonded crowns and
bridges. Where metal to porcelain bonds are made, no stalnlng
i8 observed o~ the porcelain and excellent bonding of the
porcelain to the alloy i8 obtalned.
.
,
\ . -14-~ ~
CER. 11
lOSZ598
EXAMPLE 4,
Usi~g the process Or Example 1, alloys are prepared
havlng th~ composi~ions set forth in the rollowing
Table 1. These alloys are used for the applicstion~
lndicated in the column identified "Applications".
In each use the alloy 1~ observed tg perrorm well when used
by standard accepted dental laboratories technlques.
~ ,.
-15-
~oszs9~
o o o o o
H 1--1 H H H
* ~ _ ~ ~
v~ m m m mmmm m m
o ~ ~ ~ ~~~~ ~ ~
~ m m m mmmm m m
u t~ c~ ~ uc~
Q, m m m m m m m m m
~ ~:
In
o ~ ~Lna~ o
o ~
m o ~ ,~
: ~8
. .
m ~: o o
a)
E~ ~ ~q
o ~ ~ ~ ~ O O u~
~ o n ~ ~ cn ~ m ,~
.", ........ ~ ~
m ~ ra
o o ~ ao ~ i~
o
d' d' ~ ~ ~ d' 3 C ) o O
O ~ C)
-rl
o
o o o ~ ~ ~ C~ ~ U ~ ~
' ' IJ h )11 ~1
~ ~ O~ ~ ~ ~ (~ 0 0 a) o
U ~ ~-1 ~ ~ ~ ~~,_J ~ P.l .C4 H
:n ~a;~ m
o ~ o ~ ~ m m ~ o
rl r-l fY- O O r~ r~l r-l O O ~ ~ P~ H
--16--
. ~ .,,.. , .. . , .. " . ", . i .. i . . . .
CER. ll
lOSZS98
The alloys Or Table 1 have the phy8ic81 proportles -
set ~orth ln Table II.
--17--
OER. 11
~ 05'~598
. ..
~ ~ . .
~o ~ N ~ n N U~ N
O O O O O O O O ~ O O
~1 O O U~ 0 ~5 0 0
tr) t~7 N N CU N CU N CU N C~l
Cq 2. C~ N N C~l CU N C~.l N N C~l
~q
C~ '
~ h'--a ~ ~ ~ ~ ~ ~ ~ ~ ~
H C ~; O ~ o o ~O o o
~ .,~ , .
H ~rl
H ~0_ ~ O
li3 ~ R Ir~ o ~
_ ~ ~ t ~ i 0
O O O O O C) O O O O O
_ O O O O O O O O O O O
CQ 0 O O O O O O O O O O O
o a~ o Ir~ t cO C~7 0
co ~ ~ u~
. o 8 o o g 8 g 8 g 8
CQ-- O O ~ O O O g ~
. ,, .. ., ~ ,. ~ .. . .... .. .~ ..
;~ Q O ~ O ~r) ~)
o p.~ O O ~ O O N r~ l H ~1 0
p _
~ ~ ~ .
_ ~ ~ ~ ~ ~ ~ ~ ~ ~ o,~
~a 0 li:, 0 ao ~ OQ li4 CO 00
~r ~rl IIS IIS ~ ~ d o
~ ~ c) c~c~ C) C) ~ 8
Q~ a~ 0 ~ m
--18--
CER. 11
105~5~8
EXAMPLE ~
The following Tables ITI and IV set forth d~ta
comparing the corroslon resistance and oxidation reslstance
of alloys o~ Examples 1 and 2 with the corrosion reslstance
and oxidation re~lstance of representat~ve pre~ently
commercially available materials. In order that unifor,m
comparative re~ults be obtained, all samples used in the
oxidation and corrosion tests are prep~red in the same
manner. The samples are heated to their castlng temperatures
and then cast in air in accordance with standard Lost Wax
Technique. The ca~tings a~ter cooling to room temperature
are ground with Buehler's AB HANDIMET* Grinding Papers to
600 grits, then pollshed on Buehler's SELVYT Cloths (cotton
cloth~ using 0.3~Lm alumina polishing powders.
For te~ting oxidatlon resistance, Table rv, the pollshed
samples are then washed in water followed by wa~hlng in
acetone. The same are then heated in air to 1,000F. and
then placed in a :de~ccator .On cooling the samples are
' welghed and welght recorded. The samples are then placed
ln a small furnace, 3x3xll/2 inches and heated at
20 ' a temperature of 1800F. for 5 minutes. The furnace is
eguated to the 1800F. temperature before insertlon Or
samples. A~ter the fl~e minute heatlng, the ~amples are
removed and again placed in a desiccat~and cooled. The
samples are then weighed and the weight recorded with the
dif~erence in weight indicatlng the degree o~ oxldation.
.,, ,~. .
--19--
CE~. 11
lOSZS98
For testing for corrosion resi~tance, Table III,
the pollshed samples are washed ln water, followed by
washing ln acetone. The samples are then heated in alr
to l,000F and then placed ln ad~s~ccatOr ~o cool. The
s~mple~ are then welghed, and the welght recorded. The
samples are then placed in aqueous solutions of the
concentration lndlcated and remain lmmersed in such
æolution at ambient temperature for 20 days. The samples
are then dried, weighed, and the 10~8 in welght calculated.
In Table I, Corrosion Resistance, values are glven
~or human tooth enamel, dental amalgam, and a copper zlnc
dental alloy. The values for these three metal~ are those
publlshed by Kazuo Nagai ln the JOURNAL OF NIHON UNIVERSITY
SCHOOL OF DENTISTRY, Tokyo~ Japan, Volume 11, No. 4 Issue,1969.
Mr Nagai in describing his method of sample preparation stated
that the sRmples were cast and then pollshed in accordance
with the manufacturer's in~tructions.
,.
,.
-20-
1052S98
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