Note: Descriptions are shown in the official language in which they were submitted.
3~
8SI-1384A
IMPROVED SILICONE DENTAL IMPRESSION COMPOSITIONS
.
This application is a division of
Canadian Application Serial Number 254,987,
filed June 16, 1976.
The present invention relates to
improve silicon compositions for making
detailed impressions of the mouth, gums and
- teeth. More particularly, it concerns two-
part room-temperature vulcanizing silicone
10 compositions, one part being a metallic
salt of a monocarboxylic acid as a catalyst .
and the second part being the base compound.
In one embodiment, the base compound consists
of a diorganopolysiloxane, an organosilicon
for cross-linking and a new improved filler,
which is an admixture of zinc oxide, calcium
carbonate and pumice. In a second embodiment,
the base compound consists of a diorganopoly-
siloxane, an organsilicon cross-linker
20 mineral oil and, as an improved filler, a low
oil absorption calcium carbonate.
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.~
8SI-1384A
~33~
BACKGROUND OF T~E INVENTION
Room-temperature-vulcanizing silicone rubber
has enjoyed increasingly wider use in dentistry as a
molding medium in the preparation of artificial dentures.
The material is used as a paste into which a curing agent
is mixed before use. It then changes from a pasty
consistency to a rubber-elastic state upon curing at
body temperature. Because of its elasticity, the cured
silicone can be removed from the mouth easily and can
then be used for casting a working model, such as with
plaster of paris, from which the permanent dental
piece is made.
Silicone rubber compositions offer several
advantages over materials formerly used as a dental
replica material, e.g., plaster, alginate, etc. As
compared with plaster, silicone rubber is more elastic,
has better resistance to breakage and offers good
release from the jaw. As compared with alginates,
silicone rubber is not sensitive to loss of water
(which may cause shrinkage) and possesses better
molding accuracy. Silicones also provide good dimensional
stability which is retained even on prolonged storage
in ~he air ~For reference, see "Chemistry and Technology
of Silicones", Walter Noll~ Academic Press, New York,
1968, p. 623.~
Elastomeric compositions have been utilized
in two main areas of dental impression work - one,
crown and bridge work and, two~preparation of ~ull
dentures. Crown and bridge work requires a custom
tray which is usually prepared by first making an
impression with alginate of the area of the mouth to
be repaired. A cast of this impression is then made by
~ 8SI-1384A
pouring dental stone into the hardened alginate and
curing it. The cast is then wrapped with asbestos
and a form is built up around the wrapped casting
using methyl methacrylate or some other suitable
polymeric material (e.g.) polyethylene, polyvinyl
chloride, polyepoxide, etc.). After the methyl
methacrylate has been cured, it is removed from
around the dental stone casting and used as the custom
tray for the silicone rubber impression that will be
made.
The methyl methacrylate custom tray is first
coated with a primer. Then a silicone of pasty
consistency is mixed with a curing agent and some
suitable catalyst, placed into the tray, and the tray
is inserted into the patient's mouth where curing
takes place. After this initial impression has cured,
it is removed and trimmed to eliminate undercuts and
thin-walled sections. Then a silicone compound of
lower viscosity is catalyzed and inserted into the
patient's mouth directly over the area to be reparied.
The custom tray containin~ the cured silicone rubber
initial impression is pressed firmly into place over
the catalyzed silicone until curing is complete. This
part of the procedure is then finished, and now
highly detailed impression of the patient's mouth is
forwarded to a laboratory for the making of a bridge.
For the preparation of full dentures, the
silicones are utilized in much the same manner, except
that a reusable metal perforated tray is used instead
of a custom tray made of polymeric materials. The
high viscosity silicone compound is placed into the
tray as before, inserted into the mouth to make a first
~ 8SI~1384A
impression, and this is followed by the use of a
lower viscosity silicone compound to make a more
detailed impression of the area of the mouth to be
repaired, st~stantially as described above.
An elastic silicone composition which can
be used to obtain room temperature vulcanizing dental
impressions as described above is disclosed in Nitzsche
et al, U.S. Patent No. 3,127,363, issued March 31, 1964.
Nitzsche et al disclose organopolysiloxane elastomeric
compositions that are vulcanizable at room temperature
and are taught as being useful for a variety of
purposes, including the making of casts of the mouth
and teelh. However, these compositions are not
specifically adapted to some of the requirements
relating uniqueIy to the making of dental impressions.
Lampe, U.S. Patent No. 3,6~6,090, issued
October 3, 1972, di~scloses a room temperature ctlrable
silicone rubber composition which can be used making
ear plugs. However, relatively small amounts of
filler (10-50%~ must be employed or the composition
is difficult to mold.
There have now been discovered new improved
two-part silicone rubber compositions which are
vulcanized at room temperature and are adapted for
making dental impressions. The present compositions
provide desired properties such as moderately fast
"pot life", putty-llke consistency, good shelf
stability, low linear shrinkage, and low-toxicity.
Vulcanization of the compositions of the present
invention is not inhibited by materials from which the
custom trays are made, e.g., polyarcylics, polyethylene,
polyvinylchlorides, epoxies, and the like.
8S-[-1384A
The compositions achieve greater hardness
(duro-meter build-up) within a shorter time after
cure, and can be formulated to cure to a smooth, non-
grainy appearance.
In addition, the need for custom tray
fabrication by the dentist is eliminated because the
compositions of the present invention can be employed
both as the custom tray material and as the high
viscosity compound which is inserted into the tray to
make dental impressions. ~oreover, bit registration,
which usually requires a separate operation with either
a custom tray made of methyl methacrylate or the like
or a metal perforated tray, can now be obtained with
the present silicone putty tray material at the same
time as the dental impression.
The detailed compositions are not disclosed
in the pripr art, and the remarkable properties, as
; dental impression materials, are not obvious from
anything disclosed or remotely suggested in the prior
........ .
art.
In accordance with one aspect of the invention
there is provided a two-part room temperature vulcani2ing
silicone dental impression composition which, before
curing, consists essentially of from about 0.3 to
about 0.7 parts by weight of a metallic salt of a
monocarboxylic acid as a catalystt to about 100 parts
of a base compound consisting essentially of:
(a) from about 25 to about 35~ by weight
of a fluid diorganopolysiloxane containing terminal
silicon-bonded hydroxy groups and having a viscosity
of from 2,000 to 250,000 cps. at 25C.;
(b) from about 60 to about 75% by weight of
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8SI-138~A
a fillex composition consisting essentially ~f an
admixture of zinc oxide, calcium carbonate and pumice;
(c) from about 0.05 to about 2% by weight
of an organosilicon cross-linker having the general
formula
OR
RO - Si ~ R
O~
wherein R is a radical selected from the group consisting
: 10 of alkyl, alkenyl and aryl xadicals and R] i~ a member
of the group consisting o~ alkyl, alkenyl, aryl and
alkoxy radicals.
In accordance with another aspect of the invention
there is provided a room temperature vulcanizing silicon
dental impression composition which, before curing,
consists essentially of from about 0.3 to about 0O7
parts by weight of a metallic salt of a monocarboxylic
acid as a catalyst to about l00 parts of a base
composition consisting èssentially of:
(a) from about 25 to about 35% by weigh~
of a fluid diorganopolysiloxane containing terminal
silicon-bonded hydroxy groups and having a viscosity
of rom 2,000 to 250,000 cps. at ~5C.;
(b) from about 63 to about 75% by weight o~
a filler composition consisting essentially of an
admixture of zinc oxide, calcium carbonate and pumice,
.
the zinc oxide and calcium carbonate each being present
in at least a sufficient amount to provide bulking
and whitening and said pumice being present in at least
a sufficient amount to provide putty-like consistency;
(c) from about 0.05 to about 2% by weight
of an organosilicon cross-linker having the general
~33~ 8SI-1384A
formula:
~R
RC - Si-- R
OR
wherein R is a radical selected from the group
consisting of alkyl, alkenyl, and aryl radicals and R
is a member of the group consisting of alkyl, alkenyl,
aryl and alkoxy radicals.
According to the present invention there are
provided two-part room temperature vulcanizing silicone
compositions for taking dental impressions. Before
curing, the compositions consist essentially~-of rom
about 0.3 to about 0.7 parts by we.ight of a metallic
salt of a monocarboxylic acid to 100 parts of a base
compound cosisting essentially of:
(a) a fluid diorganopolysiloxane,
(b) a filler therefor,
(c) an organo silicon cross-linker having the
general formula (Ro)3SiRl where R is a radical selected
from the group consisting of alkylr alkenyl and aryl
radicals and Rl is a member of the group consisting of
alkyl, alkenyl, aryl and alkoxy radicals, the filler
being selected from
(i) an admixture of zlnc oxide, calcium
carbonate and pumice, the zinc oxide and calci.um
carbonate each being present in at least a sufficient
amount to provide bulking and whitening, and said
pumice being present in at least a sufficient amount
to provide a putty-l:ike consistency,
(ii) a low oil and sorption calcium
carbonate, said fluid diorganopolysiloxane being
selected from
~33~ 8SI-1384A
(iii) fluid diorganopolysiloxanes containing
terminal silicon-bonded hydroxy groups and having a
ViSC05 ity of from about 2,000 to 250,000 cps. at 25C, and
(iv) diorganopolysiloxanes containing terminal
silicon~bonded hydroxy groups and having a viscosity of
from about 15,000 to about 35,000 cps. at 25C with the
proviso that when said filler is of type (i) said fluid
diorganopolysiloxane is of type (iii) and said base
consists of by weight about 25 to about 35% (a), about
63 to about 75% (b) and about 0.05 to about 2% (c); and
when said filler is of type (ii), said fluid dirogano-
polysiloxane is of type (iv) and said base consists of by
weight about 15 to about 25% (a), about 70 to about 85%
(b) and about 0.05 to about 2% (c) and additionally about 3
to about 8% of a mineral oil.
The preferred silicone fluid of type (iii) for
the base compound is a silanol-stopped dimethylpolysiloxane
(i.e., having terminal silicon bonded hydroxy groups)
with a viscosity of from 3,000 to 200,000 cps. at 25C.,
and especially preferably a viscosity o~ ~rom 3,000 to
120,000 cps. at 25C. When polysiloxanes of 80,000
to 120,000 cps. are used, a low molecular weight silanol
stopped polydimethylsiloxane containing 5 to 10
dimethyl disiloxane units and about 7% by weight of
hydroxyl groups is employed in small but effective
amounts to slow curing time. An especially effective
amount of this low molecular weight silicone is from
0.05 to 2% by weight of the total base compound.
When a polyorganosiloxane of a lower viscosity
value is employed, e.g., 2,500 to 3,500 cps. at 25 C.,
the base compound has high flow and is tacky to the
touch prior to catalyzing and non-tacky after catalyzing.
3 ~3~
8SI-1384A
When a polyorganosiloxaneOf a relatively higher
viscosity is used, e.g., 80,000 to 120,000 cps. at
25C., the base compound has low flow and is non-tacky
to the touch prior to catalyzing.
The amount of catalyst employed with the
base compound will vary depending upon the viscosity
of the latter. When diorganopolysiloxanes having a
viscosity of from 80,000 to 120,000 cps. at 25C. are
employed in the base compound, a weight ratio of about
0.5 parts of catalyst to 100 parts of the base compound
is preferred. With polysiloxanes of much lower viscosity,
e.g., 2,500 to 3,500 cps., a lower amount of catalyst
is used, such as about 0.4 parts of catalyst to lO0
parts of the base compound.
The filler of type (i) which is incorporated
into the silicone fluid of type (iii) consists of an
admixture to 3 to 15 parts, preferably 5 to 10, of
zinc oxide, 5 to 25 parts, preferably lO to 20,
of calcium carbonate and 45 to 65 parts, preferably
20 50 to 60, of pumice (A12O3-SiO2), based on lG0 parts
by weight of the base. The various components of the
filler work in combination. Calcium carbonate and
zinc oxide are used as bulking as well as whitening
agents. Pumice is used to provide a putty-like
consistency to the composition. Pumice is also
more easily wetted into the formulation and thus
assures more consistency from batch to batch than other
types of filler. Surprisingly, it has also been found
that when pumice is used as a component of the filler,
greater hardness is obtained with the composition
within a relatively short time after addition of the
catalyst and curing. All three components of the
filler must be present to produce the advantageous
~33~
8SI-1384A
results achieved with this embodiment.
The preferable cross-linking agents are
conventional organosilicon compounds used for this
purpose having the general formula
OR
~'
RO - Sl - R
OR
wherein R is a radical selected from the group
consîsting of alkyl, alkenyl and aryl radicals and
Rl is a radical selected from the group consisting of
alkyl, alkenyl, aryl and alkoxy radicals.
Some preferred cross-linking agents are
phenyl triethoxy silane, vinyl triethoxysilane,
n-propyl silicate and condensed ethyl orthosilicate.
Especially preferred is condensed ethyl orthosilicate.
Generally, from about 0.05 to about 2~ by
weight of the ~otal base compound of the organo-
silicon crosslinker is employed. Amounts less thanthis are generally insufficient to react with the
organopolysiloxane to form the cured silicone rubber,
; and amounts larger than this tend to reduce the
elasticity of the cured rubber.
Catalysts suitable for the present dental
impression compositions are conventional and well
known. Metal salts of monocarboxylic acids have been
found to be effective. Various acid radicals and
metal ions are suitable as components in the metal
salts. Some preferred acid radicals are the linoleate,
stearate, oleate, acetate, butyrate and octoate. Tin
is especially preferred for the metal ion because of
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~33~ 8SI-1384A
its low toxicity. Some preferred metal salts are tin
oleate, tin butyrate and tin actoate. Especially
preferred is tin oct~ate.
In a second embodiment there is provided a
room temperature vulcanizing silicone dental impression
composition which is non-sticky, or at most, slightly
tacky and which cures to a smooth high durometer
composition which does not have a "grainy", "gritty",
or coarse feel. This embodiment, before curing,
consists essentially of from about 0.~ to about 0.7
parts by weight of a tin salt of a monocarboxylic
acid to 100 parts of a base compound consisting
essentially of:
(a) from about 15 to about 25% by weight
of a fluid diorganopolysiloxane of type (lv) containing
terminal silicon-bonded hydroxy groups and having a
viscosity of about 15,000 to about 25,000 cps at
25C .,
tb) from about 70 to about 85~ by weight
of a filler of type (ii) consisting essentially of
low oil absorption calcium carbonate;
(c) from about 3 to about 8% by weight of
mineral oil; and
(d) from about 0.05 to about 2% by weight
of an organo-silicon cross-linker having the general
formula
OR
I
RO - Si
OR
wherein R is a radical selected from the group
~ 8SI-1384A
consisting of alkyl, alkenyl and aryl radicals and
Rl is a member of the group consisting of alkyl,
alkenyl, aryl and alkoxy groups, said composition
having a non-sticky, or at most a slight "tacky"
feel before curing, and a smooth, non-grainy feel
after curing. Some embodiments have a slight "gritty"
feel, which is not necessarily disadvantageous.
The diorganopolysiloxane of this embodiment
; is preferably a dimethylpolysiloxane having a
10 viscosity of from 15,000 to 35,000 cps. at 25 C.
and/ especially preferably, a viscosity of from about
20~000 to about 30,000 cps. at 25C.
Effective as cross-linking agents are the
same organo-siliconcompounds mentioned above as
suitable for the compositions of the first embodiment.
A relatively small amount of mineral oil
is added to reduce or eliminate any stickiness in the
base compound and facilitate its handling during the
making of dental impressions. Suitable mineral oils
will be the physio]ogically-acceptable bland fluids
available from a number of commercial sources. One
suitable mineral oil is the heavy white oil known as
Kaydol TM Mineral Oil avaliable from Sonneborn Division
of Witco Chemical Co.
For the catalyst, the same conventional
metal salts of monocarboxylic acids mentioned above
as suitable for the compositions of the first
embodiment are also suitable for these compositions.
~ he filler is a low oil absorption calcium
carbonate, which has been found to aid in providing
a smooth, non-grainy appearance and feel to the cured
silicone composition. Suitable grades of low oil
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~33~ 8SI-1384A
absorption calcium carbonates and their suppliers, are
Camel Kote* (Harry T. Campbel and Sons Co., Towson,
Maryland), Gamma Sperse* 255, Wingdale Whlte* and No.
10 White (Georgia Marble Company, Calcium Products
Division, Tate, Georgia), Duramite* (Thompson, Weinman
and Company, Montclair, New Jersey), and Micro White*
75 (Sylacauga Calcium Products Co., Sylacauga, Alabama).
Especially preferred is Camel Kote calcium carbonate.
The present invention is illustrated by the
examples given below, which are not intended to
limit the scope of the invention.
EXAMPLES 1-2
. _ .
~hese examples are illustrative of the
preparation and properties of the compositions of
the first embodiment referred to above. All proportions
are on a percent by weight basis.
The base compound of Mixture A (Example 1)
is prepared by thoroughly mixing 30.67 parts of
silanol~stopped polydimethylsiloxane having a viscosity
20 of about 3,000 cps. at 25C., 12.26 parts of calcium
carbonate reinforcing filler (Albacar*), 6.15 parts
of zinc oxide filler (XX-78) 50.02 parts of pumice
filler (Airfloat* 2599, commercially available from
James H. Rhodes and Co., Long Island City, New York)
and 0.90 parts of condensed ethyl orthosilicate. The
blend is worked until a putty consistency is obtained.
This is high flow and tac~y to the touch. 5tamous
octoate catalyst in the amount of about 0.4 parts per
100 parts of base compound is then worked into the putty
to yield Mixture A, which cures at room temperature.
Mixture B (Example 2) is similarly prepared.
The base compound of B is ~irst obtained by mixing
*TM
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~33~ 8SI-1384A
thoroughly 30.43 parts of silanol-stopped polydimethyl-
siloxane having a viscosity of about 120,000 cps. at
25 C., 12.16 parts of calcium carbonate filler ~Albacar3,
6.11 parts of zinc oxide filler (XX-78), 49.63 parts of
pumice filler (Airfloate 2599), 0.89 parts of condensed
ethyl orthosilicate, and to slow pot life, 0.78 parts
of low molecular weight silanol-stopped polydimethyl-
siloxane having about 7% by weight of hydroxy groups.
This composition is low flow and non-tacky to the touch.
10 To the resulting putty is added to about 0.6 parts of
stannous octoate per 100 parts of base compound to obtain
Mixture B, which cures at room temperature.
The properties of the compositions are surnmar-
ized in Table 1:
TABLE 1: ROOM-TEMPERATURE VULCANIZING
DENTAL IMæ~ESSION COMPOSITIONS
Example (Mixture) l(A)2(B)
Application Rate at 90 P.S.I.
in gm./min. 50-1500-30
20 Cure Time (sec.) 100-16090-150
Properties:
Specific Gravity 1.57-1.62 1.57-1.62
Linear Shrinkage
(ADA Spec. 19) 0.2-0-3% 0.2-0.3
Shore A Hardness
10 Min. 60-7060-70
20 ~in. 70-8065-75
60 Min. 75-8570-80
~ Elongation 50 59
Tear Die (lb./in.) 61 59
Color Gray Gray
The foregoing properties indicate that
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~3~ 8SI-1384A
extremely useful dental impression compositions have
been provided.
The base compounds of example 1 and 2 exhibit
good shelf aging properties for 6 months or more,
based on accelerated aging at 50C.
Neither Mixtures A or B (Example 1 and 2)
display any cure inhibition when used with custom
trays made of polyvinylchloride, polyethylene, methyl
methacrylate or epoxy materials.
The two examples given above represent
compouns made of relatively high and low viscosity
polyorganosiloxanes within the range of viscosities
possible with the present compositions. Other blends
of course, are possible, such as blends of Mixtures
A and ~ to achieve properties between the two.
EXAMPLE 3
_
This example is illustrative of the preparation
and properties of a composition of the second embodiment
which is non-tacky and produces a very smooth cured
vulcanizate. All proportions are on a percent by
weight basis.
~- The base compound cosists of a mixture of
17 parts of silanol stopped polydimethylsiloxane having
a viscosity in the range of 20,000 to 30/000 cps.
at 25C./ 5.2 parts of mineral oil (Wittco Chemical's
Kaydol)/ 77 parts of low oil absorption calcium
carbonate filler (Camel Kote), and 0.8 parts of 40~
condensed ethyl orthosilicate. The Camel Kote Filler
has an estimated oil absorption value of about 10
30 lbs. oil/100 lbs. clacium carbonate, ASTM D-281-31.
The base compounds before catalyzation, has a putty-
like consistency and exhibits good handling character-
istics, being non-tacky and non-gritting to the touch.
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8SI-1384A
This compound has a specific gravity of 1.85-1.90.
To initiate curing, starmous octoate
catalyst is added and worked into the base compound
in the ratio of 0.5 parts of catalyst per 100 parts
of base compound. The resulting catalyzed dental
impression composition has a work life of about 55
seconds at room temperature. After about 55 seconds
has elapsed, the composition becomes difficult to
handle or manipulate.
EXAMPLE 4
This example compares physical properties
of toom-temperature vulcanizable dental impression
compositions according to the present invention, using
various low oil absorption calcium carbonates as the
filler in the base compound. -;
Base compounds are prepared according to
the procedure of Example 3 using a differen-t calcium
carbonate filler in each case. The calcium carbonates
employed, together with their corresponding oil
absorption values, are summarized in Table 3.
TABLE 3: CALCIUM CARBONATE FILLERS
Oil Absorption
Fillerlbs. oil/100 lbs. ~iller (ASTM D-281-31)
Camel Kote* 10
Gamma Sperse* 255 10-12
No. 10 White7- 9
Wingdale* White 11-13
Duramite* 5- 6
Micro White* 75 10-12
The initial work life of the base compounds
using each of the above fillers is measured after
catalyzing a portion of each base compound according to
*TM
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8SI-1384A
~33~
the procedure of Example 3. The Shore A hardnesses of
the cataly~ed compounds are also measured at intervals
of 5 and 10 minutes a~ter cat~lygation. These properties
are summarized in Table 4.
To measure the stabillty of the various base
compounds, the uncatalyzed portions of each of the
compounds are shelf aged at 50C. for given time
intervals (shown in Table 4), then catalyzed as above,
and the work life and Shore A hardnesses are measured.
These properties are also summarized in Table 4.
TABLE 4: COMPARISON OF BASE COMPOUNDS USING ~ARIOUS
LOW OIL ABSORPTION CALCIUM CARBONATE FILLERS
Filler Work Life 5 min. 10 min.
(Secs.) Shore A Hardness
Camel Kote*
Initial 55 66 63
After 245 days aging 55 76 73
Gamma Sperse* 255
Initial 50 70 80
After 233 days aging 55 60 72
No. 10 White
Initial 60 70 73
After 217 days aging 60 37 50
Wingdale White*
Ini~ial 70 65 77
After 217 days aging 95 43 60
Duramite*
Initial 45 79 81
After 233 days aging 35 30 42
30 Microwhite* 75
Initial 60 68 75
After 217 days aging 60 53 68
*TM
--17--
~ ~ ,33~
8SI-138~A
The compositions employing Gamma Sperse*
~55 or Duramite* as the filler have a slightly gritty
feel. The compositions which employ Wigndale White*
or Micro White* 75 are smooth but exhibit slight tack.
The composition containing No. 10 White exhibits
a slight tack and has a slight gritty feel. The
composition using Camel Kote* filler provides good
handlingr i.e., non-tacky and non-gritty. It should
be noted that these properties, i.e., "tack" and
"gritty", are somewhat dependent on the subjective
judgmenk of the individual who is doing the handling~
Although, all the above calcium carbonate
fillers display acceptable properties, including
handling, Camel Kote* calcium carbonate appears to
give the best overall performance. This appears
to be due in parts to the particle size distribution
~ of Camel Kote* calcium carbonate, which is unique in
; that it contains substantiall~ no particles above
30 microns in size. Thus while the oil absortion
values of Camel Kote* and No. 10 White are about the
same, Camel Kote* displays better handling character-
istics, apparently because of the differences in
particle size distribution between these two calcium
carbonates.
It is to be understood that conventional
additives may also be added to the present dental
impression compositions, e.g., low-toxicity pigments
and flavors.
O-ther compositions will suggest themselves
30 to those skilled in the art in view of the above- -
detailed descriptions. All such obvious variations
are within the full intended scope of the invention,
which is de~ined in the appended claims.
*TM
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