CA1079644A - Effervescent solid denture cleanser - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Effervescent denture cleanser having excellent plaque-removing properties and which on mixing with water effervesces and dissolves in the water to form a solution for soaking dentures, the cleanser comprising substantially anhydrous trisodium phosphate, a water-soluble monopersulphate to react with the trisodium phosphate to cause effervescence with liberation of oxygen bubbles from the solution, which effervescence inhibits the tendency of the substantially anhydrous trisodium phosphate to form slowly soluble lumps on admixture with the water, the trisodium phosphate being present in an amount sufficient to give the solution a pH of at least 9, 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.

Description

. , , 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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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, o ~ .

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~

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, ~;
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~ 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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~079644 (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~

}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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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.

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 . ~ .

... .-- : . .: .. , : . . .
,, 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-.. . . . .

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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 .

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 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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Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A solid denture cleanser which on mixing with water effer-vesces and dissolves in the water to form a solution for soaking dentures, the cleanser comprising substantially anhydrous trisodium phosphate, a water-soluble monopersulphate to react with the trisodium phosphate to cause effer-vescence with liberation of oxygen bubbles from the solution, which effer-vescence inhibits the tendency of the substantially anhydrous trisodium phosphate to form slowly soluble lumps on admixture with the water, the tri-sodium phosphate being present in an amount sufficient to give the solution a pH of at least 9, and a chlorine compound which liberates hypochlorite chlor-ine 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.

2. A denture cleanser as claimed in claim 1 wherein the trisodium phosphate is present in amount sufficient to give the solution a pH of above 10.5.

3. A denture cleanser as claimed in claim 1 including a first colouring agent and a second colouring agent both of which are bleached by the action of the solution on standing but the first colouring agent being bleached more rapidly, the first colouring agent being present in such con-centration that its colour predominates in the solution initially and for several minutes thereafter, the colour of the second colouring agent becoming visible on standing for a period of less than one hour owing to loss of colour of the first colouring agent.

4. A denture cleanser as claimed in claim 1 containing from 0.01 to 1% by weight of a surfactant selected from anionic, nonionic, cationic and amphoteric surfactants capable of promoting foaming during effervescence.

5. A denture cleanser as claimed in claim 1 in tablet form, containing at least one tabletting aid selected from binders, lubricants and disintegrating aids substantially inert under the conditions of use of the cleanser, the total amount of the tabletting aid or aids being less than 50%

of the weight of the cleanser.

6. A denture cleanser tablet as claimed in claim 5 wherein the tabletting aid is selected from glucose, gum acacia, gelatin, sucrose, starches, talc, magnesium stearate and polyethylene glycol having a molecular weight in the range from 600 to 4000.

7. A denture cleanser tablet as claimed in claim 5 or claim 6 having a volume in the range from 1 to 5 c.c.

8. A denture cleanser as claimed in claim 1 in the form of a powder the particles of which have sizes such as to pass through a United States standard 10 mesh sieve but to be retained on a United States standard 40 mesh sieve.

9. A process for cleaning dentures which comprises mixing a denture cleanser as claimed in claim 1 with water to form a solution and soaking the dentures in the solution.

10. A process as claimed in claim 9 wherein the amount of water is such as to form a solution having a pH in the range from 10.6 to 11.5.

11. A process as claimed in claim 9 or claim 10 in which the active chlorine content of the solution is in the range from 400 to 1500 ppm.