Note: Descriptions are shown in the official language in which they were submitted.
1079644
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This application is a division of Canadian patent No. 1,047,405
issued January 30, 1979.
This invention relates to effervescent denture cleansers, particu-
larly suitable for the removal of the plaque which forms on dentures when they
are worn in the mouth. In using the denture cleansers of this invention the
denture may be simply soaked for a relatively short period of time in water ~,in which the denture cleanser, in tablet or powder form, has been placed. No
mechanical stirring is required; the effervescence of the composition is suf-
ficient to effect sufficient agitation and rapid dissolution of the solid
composition in the water.
Effervescent denture cleansers have long been known in the art.
Most of those presently on the market derive their cleansing efficiency main-
ly from peroxy compounds which provide active oxygen. While the active oxy-
gen does show a good bleaching action, e.g. on certain dyes, it has relatively
poor plaque-removing properties. Various peroxygen type denture cleansers
are described in ~'nited States Patents 2,498,343; 2,498,344; 2,931,776; and
3,243,377.
Another type of denture cleanser on the market uses strong acidic
solutions. This too has poor plaque removing properties.
Still another type of denture cleanser, described in United States
Patent 3,113,111, derives its cleansing efficacy mainly from an active chlor-
ine source and has good plaque-removing properties. It is not, however
effervescent and has a relatively slow rate of dissolution unless stirred
mechanically.
Effervescent denture cleansers made with sodium perborate mono-
hydrate and sodium dichloroisocyanurate have been suggested (as in the
bulletins of the FMC Corp., which is a supplier of both these ingredients).
These cleansers contain, for instance, 9 to 12% of the perborate and 2-4% of
the diisocyanurate together with certain alkaline ingredients (to give a pH
of about 7.3-8.1) and are used in amount to provide about 200 ppm active oxy-
gen and substantially no hypochlorite chlorine. Like other conventional per-
oxygen-type denture cleansers they have poor plaque-removing properties.
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107964g
In accordance with one aspect of this invention there is pro-
vided a solid denture cleanser composition which, on addition to waterJ
effervesces and dissolves quickly giving a solution which is highly effective
for the removal of plaque from dentures soaked therein for relatively short
periods of time. The solid composition, in dry powder or tablet formJ is
substantially stable on storage. According to this aspect the invention is
a solid denture cleanser which on mixing with water effervesces and
dissolves in the water to form a solution for soaking denturesJ the cleanser
comprising substantially anhydrous trisodium phosphateJ a water-soluble
monopersulphate to react with the trisodium phosphate to cause effervescence
with liberation of oxygen bubbles from the solutionJ which effervescence
; inhibits the tendency of the substantially anhydrous trisodium phosphate
to form slowly soluble lumps on admixture with the waterJ the tri-sodium
phosphate being present in an amount sufficient to give the solution a
pH of at least 9J and a chlorine compound which liberates hypochlorite
chlorine on contact with water, present in an amount such as to provide
at least 100 ppm of active chlorine in the solution after effervescence has
ceased.
The concentration of active chlorine in the water is preferably
at least about 100 ppm (preferably above about 400 ppm such as in the range
of 500 to 1500 ppm) and the pH of the water is preferably at least 10, more
preferably above 10.5; a particularly suitable range is about 10.6 - 11.5.
The concentration of active chlorine in the water can be readily measured by
conventional chemical analysis such as by addition of potassium iodide to
the solution and titration for the amount of iodine(the latter being liberated
from the KI by the action of the active chlorine); this analysis can be
made conveniently just after bubbling substantially ceases.
The alkalinity of the composition may be provided by the
inclusion therein of a suitable amount of any suitable alkaline material such
as an anhydrous alkaline alkali metal salt.
A particularly suitable chlorine compound which liberates
~ - 2 -
: . .
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hypochlorite chlorine on contact with water is a heterocyclic N-chloro imide,
e.g. a chloroisocyanurate such as sodium dichloroisocyanurate, potassium
dichloroiso-
,' .
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.1 .
- 2a -
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- . , . , ,.:
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1079644
cyanurate, or trichloroisocyanuric acid, or a complcx salt of two or more of
these materials, e.g. [(mono-trichloro)-tetra-~monopotassium-dichloro)] penta-
isocyanurate. Other N-chloro imides which may be used are sodium p-toluene-
sulfonchloramide, N,N-dichloro-p-toluenesulfonamide, sodium benzenesulfonchlor-
amide, N,N-dichlorobenzenesulfonamlde, N-chlorosuccinimide. Sti~ other com-
pounds which liberate hypochlorite chlorine on contact with water are other
imides such as N-chloro malonimide, N-chloro phthalimide and N-chloro naphthal-
; imide, the hydantoins such as 1,3-dichloro-5,5-dimethyl hydantoin; N-monochloro-
C,C-dimethylhydantoin; methylene-bis (N-chloro-C,C-dimethylhydantoin; 1,3-
dichloro-5-methyl-5-isobutyl-hydantoin; 1,3-dichloro-5-methyl-5-ethylhydantoin;
1,3-dichloro-5,5-diisobutylhydantoin; 1,3-dichloro-5-methyl-5-n-amylhydantoin;
and the like. Other hypochlorite-liberating agents are trichloromelamine and
dry, particulate, water-soluble anhydrous inorganic salts such as lithium
hypochlorite and calcium hypochlorite. It will be understood that two or more
of the chlorine compounds may be employed in admixture.
The peroxygen compound is one which yields active oxygen on admixture
with water. It may, for example, be a peroxyhydrate or hydrogen peroxide addi-
tion co~pound as described, for instance in Kirk-Othmer Encyclopedia of
Chemical ~echnology first edition Vol. 10, published 1953, pages 49ff, which
may comprise a borate, carbonate or phosphate. Particularly suitable compounds
of this type are sodium perborate monohydrate and sodium carbonate peroxyhyd-
rate (such as Na2C03 1 1/2 H202) Other very suitable peroxygen compounds are
monopersulfates such as potassium monopersulfate, KHS05. Other pcroxygen com-
pounds which may be present are, for instance, succinic acid peroxide, sodium
peroxide and calcium peroxide.
Particularly suitable materials to provide the alkalinity of the
composition are trisodium phosphate ta compound ~hich in dilutc aqueous solution,
e.g. at 0.1-1% concentration, has a pll of 11.5-11.9) or sodium carbonate
(whose dilute aqueous solutions have a pH which is gcnerally above 11).
Another highly alkaline salt is sodium metasilicate. Less alkaline salts,
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such as NaHC03, Na2 HP04, pentasodium tripolyphosphate and tetrasodium pyro-
phosphate may also~be present in admixture with the more alkaline compounds.
The alkalinity, or a portion thereof, may also be provided by suitable hydr-
oxides or peroxides, e.g. NaOH or sodium peroxide.
The ingredients of the composition are preferably of sufficiently
low water content that the composition is stable on storage, e.g. it retains
over 90% of its active oxygen and chlorine contents, and preferably over 95% -
thereof, on storage for 30 days at room temperature (e.g. 25~C) in a sealed
container; preferred compositions retain over 95% of said contents for at least
180 days under these~conditions. To this end the alkalinity-imparting material
employed, and the other components, are preferably substantially anhydrous.
The denture cleansers of the invention are typically intended for
use in concentrations of about 2 to 5 grams (preferably about 3 to 4 grams)
per 120 ~1. of water.
In the ~ost preferred forms of the invention, the metallic cations
present in the compositions are substantially entirely sodium and/or potassiu~.
-
These ~ay be replaced, at least in part, by other appropriate cations (such
as ~g, ~i, Ca, Sr, Ba3, it being preferred that compounds which are water-
soluble be employed.
In one form of the invention the peroxygen compound is one which
reacts with the chlorine compound and is decomposed by that reaction to
liberate oxygen gas, causing effervescence. For example the reaction of sodium
dichloroisocyanurate and a hydrogen peroxide addition compound such as sodium
perbora*e monohydrate in the presence of trisodium phosphate may be represented
by the followin~ equation:
C ~ N~C ~ 2NaBO 1122+2Na3P4-- C
N N ll I+ 2NaOCl+2Na2HP
Cl 1I Cl C +2NaB02+02
:, - O
01~
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In that equation the two molecules of sodium perborate are cquivalent to two
atoms of active oxygen and the one molecule of sodium dichloroisocyanurate is
equivalent to two atoms of active chlorine, so that there is a 1:1 ratio of
active chlorine to active oxygen in the components. It is preferred that this
ratio be greater than 1:1 in the components, such as at least 1.1:1. For
best results, in terms of vigorous effervescence providing rapid dissolution
and rapid homogeneous mixing with high plaque removal e~fectiveness, it is
preferred that this ratio be about 2:1 to 3:1 or more; that is, the preferred
amounts provide at least about two atoms (and more preferably about 2.2 atoms)
of hypochlorite chlorine, from the chlorine compound, for each atom of active
oxygen.
The preferred proportions are such as to provide sufficient efferves-
cence that the composition (in the form suppliéd, e.g. as a tablet or as
granulcs) dissolves substantially completely in water ~e.g. in 120 ml of water
at 4~C, using about 3-~ grams of composition) in well bolow 10 minutes, and
generally less than 5 minutes, e.g. about 2 to 4 minutes, without mechanical
stirring. It should be noted that, in the absence of the effervescent effect,
certain water-soluble materials present in the dry composition do not go into
solution quickly; for instance, anhydrous trisodium phosphate powder wllen
b~ought into contact with water tends to hydrate and form clumps or lumps
which are slow to dissolve. The peroxygen compound is preferably present in
an amount having an active oxygen content of more than 0.1% of the total com-
position, such as in the range of about 0.2 to 2% (e.g. about 0.4 to 1.3o)
acti~e oxygen.
As indicated above, effervescence can be produced by the rcaction of
the chlorine compound and a hydrogen peroxide addition product. No efferves-
cing reaction takes place when a simple blend of a monopersulfate (such as
potassium monopcrsulfatc) and the chlorine compound is placed in water. l~'hen,
however, the trisodium phosphate is present in admixturc with this blend
vigorous effervesccnce occurs. ~lis is bclieved to be due to a reaction be~-
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ween the trisodium phosphate and the monopersulfate yielding oxygen gas; itis within the broader scope of this invention to employ this reaction for
forming other effervescent denture cleansers, such as cleansers having no
active chlorine. Vigorous effervescence also occurs when a carbonatc such as
sodium carbonate is present in admixture with such a blend ~of monopersulfate
and chlorine compound); in that case it is believed that the gas is, at least
in part, carbon dioxide. In any case, in the preferred cleansers the effer-
vescence is substantially complete in less than 10 minutes, such as about one
to five minutes.
The chlorine compound is preferably present in an amount having an
active chlorine content of over 0.2% (e.g. about 1-10%, more preferably about
2 to 8%) of the total composition in addition to any amount of active chlorine
that is consumed in the effervescent reaction.
In one preferred form of the invention the composition contains a
plurality of oxidizable dyes which are oxidized at different rates to serve as
a time lapse indicator to enable the user to know how long the denture has -
been soaking and thus to know when to remove it from the soak solution if
longer term soaking is not desired. One dye, whose color predominates initial-
; ly, is of a type which is more rapidly bleached than the other. For instance, ~;
Bl.~ `
~ 20 the composition may contain a blue dye (such as FD~C 6~ee~ ~3) mixed with a
; smaller amount Gf a more oxidation-resistant red dye ~such as FD~C Red ~3). -~
~he solution-is initially blue when the tablet is dropped into warm water
(e.g. at 120Fj 49C~; after 7 minutes the color changes to purple, because
the blue dye has been so bleached that the effective concentrations of blue
and red are now similar, giving a purple appearance; after 3 more minutes
the blue has been practically all bleached out and the solution is thus pink
in color, owing to the continued presence of the red dye; after about 35 more
minutes (i.c. a total of about 45) the solution has become colorless. The
usc of a plurallty of dycs in this manner constitutcs another ~eature of this
invention and, in its broader aspccts, this-feature may bc uscd in othcr
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denture cleanser compositions, such as known non-effervescent compositions
providing active chlorine or even known compositions providing other bleaching
species such as active oxygen. Usually the proportion of dye or other color-
ing agent is less than 1%, preferably less than 1/2% of the composition. The
time periods at which color changes occur can be controlled by the proportions
of the dyes; e.g. an increase in thc amount of the readily bleachable blue dye
in the composition causes the color change to occur after a longer soaking
time. Preferably the proportions are such that a color change occurs within
several minutes, but less than one hour, from the time that the cleanser and
10 water are brought together.
The denture cleanser may also contain a surfactant in amount sufficient
to promote foaming during effervescence (e.g. about 0.01 to 1%, such as about
0.1%~. The surfactant may be of any of the well known types (e.g. anionic,
nonionic, cationic, amphoteric); thus it may be an anionic surfactant having
a long hydrophobic alkyl chain (e.g. of about 8-20 carbon atoms) attached to
a hydrophilic ionic portion such as sulfate or sulfonate radical (e.g., sodium
lauryl sulfate). See U.S. patent 2,498,344 of February 21, 1950, column 6,
for a discussion of the use of wetting agents in effervescing denture cleansers.
The composi*ion may be conveniently formed into tablets, by conventional
20 techniques, as by mixing the powders together and subjecting them to tablett-
ing pressure. The compositions may contain conventional tabletting aids,
such as binders and/or lubricants and/or disintegrating aids for this puryose.
Examples of these materials, which are preferably substantially inert under
the conditions to which the compositions are subjected, are well ~nown in the
~; art. Thus, one may employ the materials listed in "Rcmington's Practice o~
Pharmacy" by Martin and Cook, 12th edition (published 1961 by Mack Publishing
Company, Easton, Pennsylvania), and the tabletting techniques describcd there,
~-- as ?* P- 443-454. Among thcse matcrials are, for instance, glucose, gum
~ acacia, gelatin, sucrose, starclles, talc, magncsium stear3te, polyethylene gly-
- 30 col of various average molecular weights (e.g. G00 or 4000), etc. The tablet-
ting aids are generally present in total amount which is less thall half
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(usually ~cll below 40u) of thc total weight of thc composition. The si~e
of the tablct ma~ vary, gcnerally its volume is in the rangc of about 1 to 5
cc, such as about 3 cc.
Thc composition may also be in the form of a powder, e.g. small
granules having particle sizes within the range such as to pass througl- a 10
or 20 mesh sieve and be retained on, say a 40 mesh sieve (all sieve sizes
herei~ b~ir.g U.S. Sta~dard~. It is preIerable that most of the granules have
substantially the same overall composition, so that the individual granules
h-ill be effervescent. To this end the granules may be produced by thoroughly
mixi~g finely po~dered ingredients, forming the uniform mixturc into tablets,
then breaking up the tablets mechanically, and screening to obtain the desired -
si_~s of granules. Other ~nown techniqucs for forming granules of substant-
ially uniform composition may be employed.
The following Examples are given to illustrate this invention
further. Unless other~:ise stated, all proportions in this application are by
height. Trade ~larks are in quotation marks.
Exam])les 1-5
The following are formulations for making suitable effervescent
denture cleaning tablets.
; 20 1 2 3 4 5
.:
Fragrance 1.0000~ 1.500% 1.0000o1.0000~o 1.0000
Amaranth (FD4C Red X2~ - - - - O.0200
Erythrosin (FD~C Red #3) 0.0025 0.0025 0.0025 0.0025
Fast Green (FD4C Green ~3) 0.0200 0.0200 0.02000.0200
Violet s~e (I:D~C Violet #1) - - - - -~
Sodium lauryl sulfate O.IOOO 0.1000 0.1000 0.1000 0.1000
"Polyox l~;SR N-10"* 1.0000 2.0000 10.000010.0000 10.0000
Sodi UD pcrbor~te monohy~rate 7. ooon 7.0000 7.0000
Sodium dichloroisoc~nuratc 17.0000 17.000017.0000 5.0000
~otassium dichloroisocyanuratc - - - - 9.0000
* 1rade Mar~
1079644
}I)~droly_ed Cereal Solids - - 15.0000 15.0000 15.0000
Potassium monopersulfate - - - 16.0000 16.0000
Sodium pero.~ide - - - - 1.0000
Anhydrous sodium earbonate - - - - 47.879;
Anhydrous trisodium phospahte 73.8775 72.3775 49.8775 49.8775
The tablets are made by intimately mi~ing fine pouders of the ma-
terials ~partiele size such that 950 or more of each powder passes through a
100 mesh sieve) and pressing the mixture in a rotary tabletting press, using
na~ . pres~ure oflo,ooo lbs/in2 to a hardness of about 10 to 12 Strong-
Cobb units. The mass of each tablet is about 3.6 grams and its volume isabout 3ec (e.g. a round flat tablet 1 ineh in diameter and about 3/8 inch in
thic~ness). The "Polyox l~'SR N-lO"*is a water-soluble solid ethylene oxide
pol)~_r of molecular ~eight about 100,000 hich acts as a binder, lubricant
and disintegrant; the hydrolyzed cereal solids, which serves as a disintegrant,
is a t.ater-soluble material sold as "1918 ~ior-Re~"*by CPC International Inc.
; eontaining polysaecharides (about 4O di-, 5% tri, 4% tetra-, 4O penta-, 82%
hexa- and above) and 1% glucose. The dry conmpositions contain small amounts
of ~ater; thus the manufacturer's specifications for the hydrolyzed cereal
solids, as sold, indicate that it contains up to about 5% l~ater; eommercial
... . . . .
anhydrous trisodium phosphate has up to 1 1/2% water; comr.lercial anhydrous sod-
um carbonate has up to 1% water; the manufacturer's specifications for the
Pol~-ox material indicate it has up to 5% water.
Iihen the tablet of Example 3 is placed in 120 ml water at 49C and
the 3.6 g tablet is permitted to effervesce eompletely in the water the pH of
the resulting solution is 11.35; the pll does not ehange materially during soak-
- ing of the denture therein. Measurements of active chlorine content of the
solution (using the tablet of Exan~ple 3) are as follows: the time period
after the tablet is dropped into the water being indicated in parentl,eses:
720 ppm (1~ minutes), 711 (20 minutes), 693 (0.5 hour),-677 (1.5 hours),
677 (2 hours), 391 (IS hours), 32() ppm (24 llours) ~.S ppm (141 hours); the
* Trade Mark
_ g _
;
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1079644
active chlorine content at the outset (c.g. aftcr thc 14 minute period) is in
the neighborhood of 80o of the active chlorine content calculated from the
proportions of diisocyanuratc and sodium perborate, taking into account the
equation, given above~ for the reaction of these components, thus indicating
~ that some of the active chlorine is consumed in reactions with other components
of the tablet.
It will be noted that Example 5 contains also sodium peroxide to
proYide an active oxygen source of greater al~alinity in view of the loss of
sodium carbonate by reaction with the potassium monopersulfate. Even with
this addition the pH of the solution is only about 10.25 and the product is
not preferred.
Examples 6-10
; The following are formulations for making suitable effervescent
denture cleansers, in granular form.
6 7 8 9 10
Fragrance 1.0000% 1.0000% 1.0000% 1.0000% 1.0000%
.
Erythrosin ~PD~C Red #3) 0. 0025 - 0. 0025
Fast Green (F~C Creen #3) 0.0200 ~ ~ ~ 0.0200
Amaranth (FD~C Red #2) - 0. 0040
~alachite Green - 0.1000 - 0.1000
; Violet 5~B(FD~C Yiolet #1) - ~ 0.4000 0.0400
"Polyox WSR N-10" 5.0000 5.0000 5.0000 5.0000 5.0000
` Sodium perborate monohydrate 4.9000 3.0000 ~ ~ 4.0000
Sodium dichloroisocyanurate 11.7000 8.0000 ~ ~ 4.0000
Potassium dichloroisocyanurate - - 9.0000 9.0000
Hydrolyzed cereal solids 10.0000 10.0000 10.0000 10.0000 10.0000
Potassium monopcrsulfate - 10.0000 10.0000 10.0000
Anhydrous sodium carbonate - - 64.5975
Anhydrous trisodium phosphate 67.3775 62.8960 ~ 64.8600 69.9800
Trichloroisocyanuric Acid - ~ ~ ~ 6.0000
. ~ .
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Example 11
A tablet is prepared, as in Examples 1-5, from a mixture of powders
of the following ingredients: 3% sodium carbonate peroxyhydrate (14.19%
active oxygen content); 14% sodium dichloroisocyanurate, 15% of the hydrolyzed
~ cereal solids of Examples 3-10; 10% of the ethylene oxide polymer of Examples
1-10; 0.1% sodium lauryl sulfate;-1% fragrance; 0.02% FD~C Green #3; 56.88%
anhydrous trisodium phosphate. A solution formed from the tablet, as in
Example 1, shows an active chlorine content (measured about 20 minutes after
the tablet is added to the water) of about 1270 ppm.
Example 12
Example 11 is Tepeated but the content of sodium carbonate per-
.oxyhydrate is increased to 4.5% and the trisodium phosphate content is
correspondingly reduced to 55.38%. The active chlorine content of the solution
measured as in Example 11 is about 850 ppm.
Example 13
Example 11 is repeated but the content of sodium carbonate per-
,,,,~i5 oxyhydrate is increased to 6% and the trisodium phosphate content is corres-
pondingly reduced to 53.88%. The active chlorine content of the solution
measured as in Example 11 is about 640 ppm.
The pH values of the solutions formed from the tablets of Exam?les
` 11 to 13 (using a 3.6g tablet in 120 ml of water) are in the range of about
11.2 to 11.3. For the solutions formed from thc compositions of Examples 6
~ and ~ (using the same concentrations) the pl~ values are 11.5 and 10.45.
:~ Example 14
The denture cleanser of this Example is a mixture of dry fine powders,
comprising 7% powdered sodium perborate monohydrate, 17% powdered sodium di-
chloroisocyanurate and 76% powdered anhydrous trisodium phosphate. In use,
2 grams of the mixture is placed in a vessel and 60 ml of warm tap water (at
4~C) is added without stirring. Vigorous effervescence occurs. The rcsult-
ing solution, having a pll of about 11.4 to 11.5 and containing in thc neigh-
.. . . . .
1079644
.:
borhood of 1560 ppm of active chlorine, is very suitable for cleaning dentures
by soaking.
Example 15
The denture cleanser of this Example is a mixture of dry fine
powders, comprising 7.7% powdered sodium perborate monohydrate, 18.7% powdered
sodium dichloroisocyanurate, 65.2% powdered Na2HP04 and 8.4% powdered anhydr-
ous trisodium phosphate. In use, 4.5 grams of the mixture is placed in a
vessel and 120 ml of warm tap water (at 43C) is added without stirring.
Vigorous effervescence occurs. The resulting solution, having a pH of about
9.0, is effective for cleaning dentures by soaking. ~luch better results are
obtained when the relative proportions of Na2HP04 and Na3P04 are varied (to
change the weight ratio of these components to 0.87:1) so as to give a pH of
.
10~6
r
On standing, the solutions formed from the compositions of
Examples 1-4 and 6 (which contain Erythrosin and Fast Green) show the color
changes described earlier. The solutions of Example 5 and 8 change from
~- violet to purple to pink; the solution-of Example 7 changes from green to
gray to pink.
` The denture cleanser of this invention form soaking solutions which
.~;, .
are safe and non-toxic and can be removed readily from the denture, by simple
rinsing with ~unning water.
The content of active chlorine can be determined by conventional
analysis as follows: Cool the solution to room temperature, then add (to 120
ml of the solution) one gram of potassium iodide; this causes the solution to
turn brown owin~ to the liberation of iodine by the action of the active
chlorine. Then titrate with 0.1 N aqueous solution of sodium thiosulfate until
the brown color just disappears, then acidify with 3 ml of 50% aqueous solution
of 1l2SO4 (which causes the solution to turn brown again), continue titrating
with the sodium thiosulfate until the solution becomcs light ycllow, then add
starch which causcs the solution to turn blue (owing to thc reaction of the
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reaction of the starch with the remaining iodine) and then titrate with the
sodium tlliosulfate until the blue color disappears. The calculation of the
ppm of active chlorine based on the volume of sodium thiosulfate solution
used fos titration is conventional.
The plaque removal and bleaching actions of denture cleansers may
be measured in the following manner: A denture worn by a person for 16-24
hours withoutcleaning is rinsed in water to remove saliva and the loose food
particles. It is then stained in a 1% aqueous solution of a red dye
(erythrosin~ for 2 minutes to disclose the location and amount of oral deposit
~plaque) on the denture. The plaque is stained in red color. The deeper the
red color of the denture, the heavier the plaque accumulation. The stained
denture is passed through seven rinses of water to remove the excessive dye - '
not adhering to the plaque. The denture may then be photographed (e.g. with
color slide transparency) for the purpose of recording its appearance. For a
i bleaching efficacy test, the stained denture is cleaned with the particular
denture cleanser yroduct according to its instructions, the denture is then
passed ~llrough seven rinses of water to remove the residual cleansing ingred-
ients and photographed. The lighter the red color of the denture, the
greater the bleaching efficacy of that denture cleanser being tested. For
cleansing efficacy (plaque removal) test the denture is stained once again
for 2 minutes in 1% erythrosin solution and passed through seven rinses of
water and then photographed. The lighter the red color on the denture, the
greater the cleansing (plaque-removing) efficacy of that denture cleanser
product.
A typical denture cleanser of this invention will remove ylaque
from a denture which llas been worn, say, about 16 hours, to the following
extcnt: about 85~ of the plaq~e is removed if the denture is soaked for about
7 minutes in a wa~n (110-120F, 43-49C) solution of the denture cleallser
(using about 4 grams of cleanser in 120 ml water); at total soaking periods
of 10, 15 and 30 minutes the percentages of plaque removal are 90%, 93u and
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100%, respectively. IYith the multicolor changes (owing to the use of two
different dyes) described above, the denture wearer can obtain the degree of
cleaning he desires consistent with the available soa~ing time. Conventional
effervescent denture cleansers based on active oxygen show very much lower
_ plaqueremoval.
Conventional dentures are composed of porcelain or organic plastic
teeth (e.g. of acrylic resin) set into an organic plastic base (e.g. of an
acr~lic r-,ir. ,~ch as polymerized methyl methacrylate) which is colored pink - r
to simulate the gums of the wearer. The plaque accumulates on the teeth and
on the base as well.
As is well known in the art, certain combinations of active
chlorine and nitrogen compounds ~e.g. ammonium salts, urea peroxide) yield
nitrogen chloride which is a toxic gas. It is of course preferable to use
such ingredients and proportions that formation of significant amounts of
nitrogen chloride is avoided.
It is understood that the foregoing detailed description is given
merely by hay of illustration and that variations may be made therein without
departing ~ro~ the spir~t of the invention.
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