Cleaning tablet for dentures and method for producing thereof.

0001The invention relates to a cleaning tablet for automa­tic cleaning of dentures in aqueous solution, subdivid­ed in two layers with different compositions, having a content of sodium hydrogen carbonate as the carbon dioxide producing agent, sodium polyphosphate as binder, further organic binders and acid carriers, potassium monopersulphate as oxidizing agent, surfac­tants in the form of alkyl or alkyl aryl sulphonates, hardened triglycerides and silicon dioxide as tablet­ting aids, polyethylene glycol with a molecular weight of approximately 20,000 as granulation medium, fatty acid esters of sugar as foam supporters and colouring and flavouring agents, as well as a method for produc­ing thereof.

0002The DE- Y-23 57 720 discloses a cleaning tablet that is subdivided in two layers with different compositions. These two layers are dissolving in water with very different rates, so that there is a two-phase cleansing of the denture. This solution shows a pH during the whole process of dissolving and cleansing of between 6.5 bis 7.0. Although this known cleaning tablet al­ready shows very good cleansing properties, there are still some problems especially with respect to the germ killing ability.

0003Thus, the problem of the invention is to provide a cleaning tablet for dentures that shows superior cleansing properties and superior germ killing ability than the known tablet.

0004According to the invention this problem is solved by a cleaning tablet of the above mentioned kind which is characterized by a change of the pH from acidic to alkaline during the dissolving process of the tablet in water.

0005The invention further relates to an improved method for producing a cleaning tablet according to the invention that is characterized in that sodium bicarbonate, so­dium perborate monohydrate, tartaric acid, sodium tri­polyphosphate, sulphamic acid, polyethylene glycol (20 M) and ethylene diamine tetraacetate are granulated; that the indicated quantities of such granulates and of the other ingredients are tumble-mixed to form one mixture for the first layer and one mixture for the second layer; that the mixture for the second layer is compressed at a low pressure and that then the mixture for the first layer is compressed to the second layer at a high pressure to form a two-phase tablet.

0006Preferred embodiments of the cleaning tablet and the method of producing thereof are subject of the respec­tive subclaims.

0007The cleaning tablet according to the invention shows a characteristic pH swing from acidic to alkaline and a greater generation of oxygen than the commercial two-­phase tablet.

0008The destaining, plaque removal and antimicrobial activ­ity of the cleaning tablet according to the invention has been compared with the commercial formulation in a series of tests. The improved tablet was at least twice as effective at stain removal than commercial tablets. Both tablets removed 43 % of artificial plaque by dry weight. In suspension tests, those tablets rapidly killed Staphylococcus aureus, Streptococcus mutans and Pseudomonas aeruginosa. The improved tablet was con­siderably more active against Escherichia coli and Candida albicans, which is of particular importance, since Candida albicans is the only resident oral micro­organism likely to be pathogenic to denture wearers. Against in vitro mixed plaques, the improved tablet was more active against Escherichia coli, Staphylococcus aureus and particularly Streptococcus mutans. Overall, the cleaning tablet according to the invention repre­sents significant improvement over the existing formu­la.

0009Moreover the composition and the method of producing according the invention leads to a tablet that is much more consistent with respect to manufacture at high speed and high pressure and to chemical composition.

0010Typically, a cleaning tablet according to the invention has the following composition in its first layer: 25 - 35 % by weight sodium bicarbonate, 20 - 30 % by weight tartaric acid, 10 - 20 % by weight potassium monopersulphate, 10 - 13 % by weight sulphamic acid, 3 - 15 % by weight disodium pyrophosphate, 3 - 5 % by weight sodium carbonate, 2 -4 % by weight polyethylene glycol (20 M) 0 - 3 % by weight sodium sulphate, 1 - 2 % by weight flavour blend, 1 -2 % by weight silicon dioxide, 0.3 - 0.8 % by weight sodium dodecyl benzene sulphonate and the following composition in its second layer: 25 - 45 % by weight sodium perborate monohydrate, 25 - 35 % by weight potassium monopersulphate, 10 - 25 % by weight sodium bicarbonate, 7 - 18 % by weight sodium tripolyphosphate, 2 - 4 % by weight ethylene diamine tetraacetate, 2 - 4 % by weight sodium carbonate, 2 - 3 % by weight polyethylene glycol (20 M), 1 - 3 % by weight silicon dioxide, 1 - 2 % by weight flavour blend, 1 - 2 % by weight fatty acid esters of sugar, 0.3 - 0.8 % by weight hardened triglycerides, 0.3 - 0.5 % by weight sodium dodecyl benzene sulphonate, 0.2 - 0.4 % by weight succinate detergents, 0.05 - 0.15 % by weight colouring agents.

0011Among the above mentioned ingredients present in both layers of the tablet according to the invention, sodium bicarbonate serves as gaseous carbon dioxide supply, while potassium monopersulphate is an oxidizing agent supplying gaseous oxygen to the solution.

0012The organic acids, i. e. tartaric acid and sulphamic acid in the first layer have an antimicrobial effect, detaching scale from dentures, and are provid­ing the acidity in the first phase of cleansing.

0013The content of ethylene diamine tetraacetate is soft­ening and demineralizing. Disodium pyrophosphate in the first layer and sodium tripolyphosphate in the second layer are detergent builders, attacking the denture plaque by their surface activity. Sodium dodecyl benzene sulphonate and the succinate detergents, both being effective surfactants, are improving the cleansing activity. The fatty acid esters of sugar are supporting the action of the surfactants.

0014Sodium perborate monohydrate is another oxidizing agent providing at the same time for the alkaline conditions in the second phase of the cleansing process.

0015Sodium carbonate is a stability aid, silicon dioxide as well as the hardened triglycerides are tabletting aids and sodium sulphate acts as a filler.

0016The preferred flavour blend consists of 20 - 25 % of a commercial peppermint oil carried on maltodextrin powder and the colouring agents in the second layer are preferably blue dyes.

0017The combination of ingredients causing the above mentioned pH swing according to the present invention is providing for an enhanced activity of each of the two layers compared to the two-phase tablet known from DE-Y-23 57 720.

0018A typical compressed tablet common in the pharmaceuti­cal industry would carry active substances within a compression base. Such bases are those that are known to compress well into hard, non friable tablets. Thus the technology of compression can be developed for the base, then active substances added. This cannot be in a tablet according to the invention that is expected to dissolve rapidly, generate and sustain a high rich foam, direct a pH swing, evolve carbon dioxide then oxygen, cleanse, wet and sanitise/deodorise.

0019Therefore many ingredients must fulfill at least two functions. As an example, the compounds chosen to pro­duce gaseous oxygen must be suitable to compression without brittleness, must evolve oxygen at an optimal delivery rate over a selected period and leave alkaline rendering residues to the solution. Another example is the use of silicon dioxide: firstly it acts as a gli­dant-lubricant such that powder flows via feed-tubes and hoppers to the tablet presses; secondly, within the tablet itself the dry, amorphous silicon dioxide acts to dry out sticky detergents which would otherwise cause sticking of tablets to hot compression punch metal faces. The content of the silicon dioxide must be chosen optimal, any increase causing brittle, chipping tablets and unacceptable cloudiness of the solution.

0020Producing cleaning tablets according to the invention is quite complex for the following reasons: <ul id="ul0001" list-style="none"><li>1. As mentioned above, the formulation does not permit the inclusion of pharmaceutical tabletting compression aids. Thus the tablet is formed by the skilled techno­ logy of compressing detergents, oxygen generators and phosphate builders.</li><li>2. Forming a solid, permanent union between the two layers is difficult to accomplish since the second, "blue" layer must be hard enough to survive as a pre-­tablet yet soft enough to allow key-binding of the following first, "white" layer. Therefore finely ba­lanced formulations and respective pressure are necessary.</li><li>3. Produced tablets must be sufficiently hard to sur­vive harsh packaging process yet sufficiently porous to rapidly dissolve in water.</li></ul>

0021Further features and advantages of the invention can be gathered form the following description of a perfor­mance example.

0022First of all, sodium bicarbonate, sodium perborate monohydrate, tartaric acid, sodium tripolyphosphate, sulphamic acid, polyethylene glycol (20 M) and ethylene diamine tetraacetate are separately granulated by fluid­ising in a hot air bed at 60 - 65 °C for 30 minutes. Such granulates are then tumble mixed with the other ingredients to produce a "first layer" mixture and a "second layer" mixture, wherein the "first layer" mixture has the following composition: <tables id="tabl0001" num="0001"><img file="EP0248936A1_D0001.tif" /></tables> and the "second layer" mixture has the following com­position: <tables id="tabl0002" num="0002"><img file="EP0248936A1_D0002.tif" /></tables>

0023A tablet is produced by compressing in a HORN rotary tabletting press of 39 stations. Compressing is in two stages: Initially the "second layer", blue mixture is compressed to very low pressure (10 kN per tablet by way of tamping. The "first layer", white mixture is then instilled and pressed to 70 kN per tablet. In this way a tablet of 4 grammes is produced being 2.7 grammes blue and 1.3 grammes white. Outputs are in the order of 45,000 tablets per hour.

0024The features disclosed in the foregoing description and in the following claims may, both separately and in any combination thereof, be material for realising the invention in diverse forms thereof.