A DENTURE CLEANING APPARATUS

Abstract: The invention relates to a denture cleaning apparatus consisting essentially of: a) a container for holding cleaning fluid; b) a basket, for holding a denture, removably disposed within the container; and c) a cover for the container; characterised in that the container has a side wall comprising thermal insulation means selected from: i) a cavity wall; ii) a cellular foam wall; and iii) a thermally insulating jacket attached to and enclosing the container side wall. The invention further relates to a method of cleaning a denture comprising soaking the denture in an aqueous solution at a temperature of greater than 50 DEG C, the solution comprising a cleaning agent and being contained within a denture cleaning apparatus having a Thermal Efficiency Indicator selected from a Heat Loss Value of less than 7.5 DEG C and a Touch Temperature of less than 40 DEG C. The apparatus and method of the invention provide for improved denture cleaning without discomfort to a user when handling the apparatus.

Description: A DENTURE CLEANING APPARATUS Technical Field The present invention relates to a cleaning apparatus for dentures orthodontic brackets and the like. In particular, the invention relates to a cleaning apparatus for holding a hot fluid, the apparatus comprising thermal insulation means to retard heat loss from the fluid. By maintaining the fluid at a high temperature, improved cleaning is obtained. Background A common method for cleaning a denture is to immerse the denture in a warm or hot solution of a cleaning product, the solution being contained within an apparatus which may be a glass or a beaker but will often be a purpose designed receptacle. Such purpose designed receptacles are well known and typically comprise a container, a lid and a basket for suspending the denture in the container. Typical examples of such receptacles are described in DE 19 09 545, BE 898,818, US 5,275,185 and US 5,184,718. More elaborate cleaning receptacles employing electrical stirrers or other agitation means are also known, for example those described in EP-A-28,672 and FR 2,738,479. Typical usage instructions for denture cleaning tablets and granules are to dissolve the product in water at about 40 to 50°C, this often corresponding to the temperature of a domestic hot water supply. Heat loss at such temperatures is not generally high and would not usually be such as to make the outside of the cleaning receptacle uncomfortable to handle. With cleaning compositions comprising active oxygen bleaches however, cleaning activity is rather slow at this temperature. One of the methods used to compensate for this is to use a bleach activator, as is now well known in the denture cleansing art. Nevertheless it remains preferable, for improved cleaning performance, to maintain a bath temperature at its designed level, since the kinetics of bleach decomposition are such that even small falls in temperature can lead to significant reductions in bleach activity. When a very hot cleaning fluid is employed, one also needs to avoid the cleaning receptacle becoming uncomfortably hot to handle. This can be a particular risk where additional microwave heating has been employed to boost the cleaning fluid temperature, such as described in US 5,201,411 and US 5,314,543. Despite the foregoing it seems that relatively little attention has been paid to the design of denture cleaning apparatus in order either to minimise heat loss from the bath or to facilitate safe employment of very hot cleaning fluids. Accordingly, it is an object of this invention to provide a denture cleaning apparatus that is better able to retain the heat of a warm or hot cleaning fluid. It is a further object of this invention to provide a denture cleaning apparatus that can be comfortably handled when containing a very hot fluid. It is yet a further object of this invention to provide a heat retaining denture cleaning apparatus that is simple to manufacture. It is a still further object of this invention to improve the cleaning performance of a denture cleaning fluid. Summary of the Invention The invention provides a denture cleaning apparatus consisting essentially of: a) a container, for holding cleaning fluid, having a container bottom and a container side wall, the container bottom and the container side wall defining a first compartment; b) a basket, for holding a denture, removably disposed within the first compartment, the basket having a basket bottom and a basket side wall, the basket bottom and the basket side wall defining a second compartment, the basket having one or more holes or slots in the basket bottom or the basket side wall to allow communication of the fluid between the first and second compartments; and c) a cover for the container; characterised in that the container side wall comprises thermal insulation means selected from: i) a cavity wall, ii) a cellular foam wall; and iii) a thermally insulating jacket attached to and enclosing the container side wall. The invention further provides a denture cleaning apparatus comprising: a) a container, for holding cleaning fluid, having a container bottom and a container side wall, the container bottom and the container side wall defining a first compartment; b) a basket, for holding a denture, removably disposed within the first compartment, the basket having a basket bottom and a basket side wall, the basket bottom and the basket side wall defining a second compartment, the basket having one or more holes or slots in the basket bottom or the basket side wall to allow communication of the fluid between the first and second compartments; and c) a cover for the container; characterised in that the container side wall comprises thermal insulation means selected from: i) a cavity wall, ii) a cellular foam wall; and iii) a thermally insulating jacket attached to and enclosing the container side wall, and that the apparatus has a Thermal Efficiency Indicator selected from a Heat Loss Value of less than 7.5°C and a Touch Temperature of less than 40°C. The invention yet further relates to a method of cleaning a denture comprising soaking the denture in an aqueous solution at a temperature of greater than 50°C, the solution comprising a cleaning agent and being contained within a denture cleaning apparatus having a Thermal Efficiency Indicator selected from a Heat Loss Value of less than 7.5°C and a Touch Temperature of less than 40°C. The apparatus and methods of the invention provide for improved denture cleaning without discomfort to a user when handling the apparatus. All percentages and ratios herein are by weight, unless otherwise indicated. Detailed Description of the Invention The apparatus and methods herein are for cleaning a denture. By "denture" is meant any device that is designed to be worn within the mouth, for the purpose of replacing or supporting a person's teeth, over a period of several days or more but that may be temporarily removed from the mouth by the wearer for the purpose of cleaning or hygienic treatment. This includes artificial teeth and also orthodontic brackets, bridges and the like. The apparatus of the invention is preferably made by standard moulding techniques such as injection moulding, including gas-assisted injection moulding and foamed injection moulding, blow moulding and vacuum forming. Highly preferred is injection moulding. Accordingly, preferred materials from which the apparatus is manufactured are those suitable for the method, including polypropylene, poly- ethylene, polystyrene and styrene-acrylonitrile. Preferred for its ease of injection moulding, impact resistance, low thermal conductivity and low cost is polypropylene. A preferred material for vacuum- forming is polystyrene. In a first aspect of the invention the denture cleaning apparatus consists essentially of: a) a container, for holding cleaning fluid, having a bottom and a thermally insulating side wall; b) a basket for holding a denture; and c) a cover for the container. By "consists essentially of or "consisting essentially of is meant that the apparatus does not comprise electrical or mechanical agitating devices such as motors or the like. The denture cleaning apparatus in this first aspect can include appendages such as feet, handles, labels or the like. The container has a container bottom and a container side wall such that it can contain a fluid. It has an open top and is generally in the shape of a cup. Whilst the shape and size of the container are not critical, it is preferably designed to avoid having a large surface area that might otherwise lead to excessive heat loss. The cross-sectional area of the container, measured in the horizontal plane is generally in the range from about 20 to about 100, more usually from about 40 to about 70 cm^. The container can have a circular, regular polygonal or irregular cross-section. It should of course be suitable for its intended purpose of accommodating a denture- holding basket. The container preferably has an internal volume of from 200 to 400 mis, more preferably from 250 to 350 mis. The basket, removably disposed within the first compartment, has a basket bottom and a basket side wall, the basket bottom and the basket side wall defining a second compartment. In use the denture is held within the second compartment. . The basket can be lifted out of the first compartment for the purpose of safely removing the denture after cleaning. The basket has one or more holes or slots in the basket bottom and/or the basket side wall to allow communication of the fluid between the first and second compartments. Preferably the basket bottom has one or more holes or slots therein to provide for drainage of the cleaning fluid as the basket is lifted away from the container. The basket preferably has an internal volume of from 180 to 300 mis, more preferably from 220 to 280 mis. The container has a cover to prevent dirt falling into the container and to prevent splashing of the cleaning fluid whilst it is moved. The cover also acts to reduce heat loss from the cleaning fluid. It should preferably cover the whole of the top of the container. The cover can be a separate, completely removable item or it can be fastened to the container. Suitably it is hinged to the container to prevent it from being lost and at the same time allowing easy access to the container so that the basket, denture or cleaning fluid can be added or removed. Alternatively, and preferably, the cover can be hinged to the basket. In this way the cover can be used to help lift the basket out of the container. The cover can have knobs or flanges attached for this purpose. In this first aspect of the invention the container side wall comprises thermal insulation means selected from: i) a cavity wall, ii) a cellular foam wall; and iii) a thermally insulating jacket attached to and enclosing the container side wall. Preferably the container side wall comprises a cavity wall. By a cavity wall is meant a double wall, having an inner and outer wall, with a gap between the two walls. The cavity wall preferably extends over at least 75% of the height of the container and around at least 75% of the periphery of the container. More preferably, the cavity extends around the whole of the container such that the entire container side wall is a double wall. The inner wall is preferably integrally constructed with the outer wall. The outer wall can be attached to the inner at any point. Preferably it is continuously attached at the top or bottom of the container to facilitate moulding. In a preferred embodiment the outer wall is attached to the inner wall at the top of the container and the outer wall extends below the bottom of the container such that the container rests on the bottom edge of the outer wall when it is placed on a flat surface, with the bottom of the container, which is integrally constructed with the inner wall, being held above the surface. The inner and outer walls can be parallel but are preferably sufficiently divergent to allow for easy ejection of the container from a mould. The gap between the two walls can be completely closed or it can be open. Preferably it opens adjacent to the bottom of the container. If the gap between the inner and outer walls is closed it can contain a vacuum or a gas. In a highly preferred embodiment the entire container is constructed in a single injection moulding step. The thermal insulation means can also be a cellular foam wall. This is suitably made by gas-assisted or foamed injection moulding as is known in the art. By a cellular foam wall is meant a continuous wall including a plurality of gas bubbles. The volume ratio of bubbles to plastic is preferably at least 2:1, more preferably at least 3:1. The thermal insulation means can also be a thermally insulating jacket attached to and enclosing the container side wall. The jacket can be chemically attached to the container side wall, such as by adhesive, or it can be physically attached, for example by being shrink-wrapped onto it. Examples of this approach are described in US 5,469,983 which discloses laminated insulating sleeves for drink containers. Of course the container can comprise two or more different insulation means, such as a double wall and a jacket, and the cover for the container can comprise the same insulation means as the container side wall. In preferred embodiments the thermal insulation means are such that the apparatus has a Thermal Efficiency Indicator selected from a Heat Loss Value of less than 7.5°C and a Touch Temperature of less than 40°C. The Thermal Efficiency Indicator is a means of measuring the effectiveness of the thermal insulation means. The Heat Loss Value is measured by filling the apparatus with 200 mis of 65 °C water and covering the container with the cover of the apparatus. The temperature of the water in the centre of the apparatus is measured using a digital thermometer after a period of 10 minutes, when the apparatus has been left to stand in still air at a temperature of 22°C. The difference between the initial temperature value (65°C) and the value after 10 minutes is the Heat Loss Value which is preferably less than 7.5°C, more preferably less than 7°C and especially less than 7.5°C. The Touch Temperature is the temperature of the exterior of the container side wall, in the same test, after 5 minutes, measured at a point half way down the wall and average over four readings taken at equally spaced points around the periphery (such as at North, South, East and West). The Touch Temperature is preferably less than 40°C, more preferably less than 35°C and especially less than 30°C. The Touch Temperature is conveniently measured with temperature indicating strips pressed against the side of the container. The invention also relates to a method of cleaning a denture comprising soaking the denture in an aqueous solution at a temperature of greater than 50°C, the solution comprising a cleaning agent and being contained within a denture cleaning apparatus having a Thermal Efficiency Indicator selected from a Heat Loss Value of less than 7.5°C and a Touch Temperature of less than 35°C. Suitably, the aqueous solution is prepared by dissolution or dispersion in water of a concentrated composition such as a concentrated liquid, paste or a solid, granular or tablet composition. In preferred embodiments herein the aqueous solution is prepared by dissolution in water of a tablet which effervesces on contact with water. Tablets provide a convenient unit dosage form and the effervescence helps disperse the tablet components. The composition can be a thermogenic composition such as described in US 4,115,293. The cleaning agent can comprise a surfactant, a bleaching agent or an enzyme, or mixtures thereof. Suitable surfactants are selected from anionic surfactants, nonionic surfactants, amphoteric surfactants and mixtures thereof. The surfactant used in the denture cleansing compositions of the invention can be selected from the many available that are compatible with the other ingredients of the aqueous solution. The cleaning agent preferably comprises a bleaching agent. The bleaching agent acts to clean and sterilise the denture. The bleaching agent is preferably selected from any of the well-known persalt bleaching agents known for use in denture cleansers such as the alkali metal and ammonium persulfates, perborates, percarbonates and perphosphates and the alkali metal and alkaline earth metal peroxides. Examples of suitable bleaching agents include potassium, ammonium, sodium and lithium persulfates and perborate mono- and tetrahydrates, sodium pyrophosphate peroxyhydrate and magnesium, calcium, strontium and zinc peroxides. Of these, however, the alkali metal persulfates, perborates and mixtures thereof are preferred for use herein, highly preferred being the alkali metal perborates. Suitable perborate salts are the alkali metal perborates, particularly sodium perborate. Sodium perborate is preferably used as the monohydrate or anhydrous form, although the tetrahydrate can also be used. Especially preferred is the monohydrate or mixtures of the monohydrate and anhydrous forms of sodium perborate. Suitably the ratio of anhydrous to monohydrate is from 0:100 to about 30:70. Enzymes can also optionally be used in the compositions of the present invention. Suitable enzymes include proteases, alkalases, amylases, lipases, dextranases, mutanases and glucanases. Aqueous solutions employed in the methods of the invention can be supplemented by other usual components of such formulations, especially additional effervescence generators, bleach activators, desiccants, chelating agents, enzymes, flavours, physiological cooling agents, antimicrobial compounds, dyestuffs, sweeteners, foam stabilisers such as the fatty acid sugar esters, and preservatives. Enzymes can also optionally be used in the compositions of the present invention. Suitable chelating agents and enzymes are described in WO 96/19563. A typical volume for an aqueous solution of the present invention is from about 150 to about 350 mis. The denture is preferably allowed to soak for a period of from one minute to twenty- four hours, preferably from ten minutes to one hour and more preferably for about fifteen minutes. Description of the preferred embodiments The invention will now be described by way of example only, and with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a denture cleaning apparatus , comprising a container, a basket, and a cover, according to the present invention. The figure shows the basket partially inserted into the outer container. Fig. 2 is a vertical cross-section through line A-A of the container shown in Figure 1. Fig. 3 is a part perspective view from below of the container shown in Figure 1. Figs. 3, 4 and 5 are vertical cross-sections through alternative container embodiments of the invention. Referring now to Figures 1, 2 and 3, a denture cleaning apparatus comprises a container 1 having a container bottom 2 and container side wall 3, the side wall being a double wall comprising inner wall 4 and outer wall 5 with a gap between. The double wall acts to reduce heat loss from hot fluid in the apparatus and also means that the outer wall 5 is comfortable to touch even when the container holds a very hot fluid. The apparatus further comprises a basket 6 which fits inside the container and is supported on its upper rim. The basket 6 has holes 7, in the form of elongated slots, formed in the basket side wall 8 and basket bottom 9 to allow passage of the cleaning fluid between the interiors of the basket and the container. The dimensions of the container and the basket are such that, when the basket is fully inserted into the container, there is a clearance between the basket bottom and the container bottom sufficient to accommodate a denture cleansing tablet. The basket 6 further comprises a cover 10 for the apparatus which articulates on the basket via two living hinges 11. When the basket is fully inserted into the outer container and cover 10 is closed, the cover completely covers container 1. An undercut 12 on the outer wall 5 of the container assists the user in lifting the lid, if required, whilst the basket is inserted in the container. To further assist removal of the basket, the basket is provided with grip tabs 13 which depend from extensions of the upper rim of the basket and lie approximately parallel to the basket side wall. The tabs 13 mate with corresponding recesses 14 in the container side wall, so that when the basket is fully inserted into the container the tabs fit flush with the container peripheral wall. The tabs can optionally be provided with undercuts or surface decoration, such as the chevrons 15 indicated, to provide additional grip. The internal dimensions of the container are such that, when the basket is fully inserted and contains a full denture, a volume of the composition in the range from about 130 to about 185 mis will fully cover the denture, depending on its size. The holes 7 in the basket can be of any size and shape provided that they allow fluid communication between the outer container 1 and the interior of the basket 6. In practice, there also needs to be sufficient material in the basket to give it sufficient rigidity to retain its shape. In Figure 4, an alternative embodiment of a cavity wall is shown in which the inner wall 4 and outer wall 5 completely enclose a gas-filled gap 16. The container can be made by gas-assisted injection moulding. In Figure 5, the container has a cellular foam side wall 3 enclosing gas bubbles 17. The container can be made by foamed injection moulding, employing a CO 2 generating foaming agent in the plastic wall material. In practice the gas bubbles can occupy a much larger proportion of the wall volume. In Figure 6, the side wall 3 of the container has an insulating jacket 18 shrink- wrapped onto it.

Claims: WHAT IS CLAIMED IS: 1. A denture cleaning apparatus consisting essentially of: a) a container, for holding cleaning fluid, having a container bottom and a container side wall, the container bottom and the container side wall defining a first compartment; b) a basket, for holding a denture, removably disposed within the first compartment, the basket having a basket bottom and a basket side wall, the basket bottom and the basket side wall defining a second compartment, the basket having one or more holes or slots in the basket bottom or the basket side wall to allow communication of the fluid between the first and second compartments; and c) a cover for the container; characterised in that the container side wall comprises thermal insulation means selected from: i) a cavity wall, ii) a cellular foam wall; and iii) a thermally insulating jacket attached to and enclosing the container side wall. 2. A denture cleaning apparatus according to Claim 1 wherein the thermal insulation means is a cavity wall. 3. A denture cleaning apparatus according to Claim 1 wherein the entire container is constructed in a single injection moulding step. 4. A denture cleaning apparatus comprising: a) a container, for holding cleaning fluid, having a container bottom and a container side wall, the container bottom and the container side wall defining a first compartment; b) a basket, for holding a denture, removably disposed within the first compartment, the basket having a basket bottom and a basket side wall, the basket bottom and the basket side wall defining a second compartment, the basket having one or more holes or slots in the basket bottom or the basket side wall to allow communication of the fluid between the first and second compartments; and c) a cover for the container; characterised in that the container side wall comprises thermal insulation means selected from: i) a cavity wall, ii) a cellular foam wall; and iii) a thermally insulating jacket attached to and enclosing the container side wall, and that the apparatus has a Thermal Efficiency Indicator selected from a Heat Loss Value of less than 7.5°C and a Touch Temperature of less than 40°C. 5. A denture cleaning apparatus according to Claim 4 wherein the entire container is constructed in a single injection moulding step. 6. A denture cleaning apparatus according to Claim 4 wherein the apparatus has a Touch Temperature of less than 40°C. 7. A denture cleaning apparatus according to Claim 6 wherein the apparatus has a Touch Temperature of less than 30°C. 8. A method of cleaning a denture comprising soaking the denture in an aqueous solution at a temperature of greater than 50°C, the solution comprising a cleaning agent and being contained within a denture cleaning apparatus having a Thermal Efficiency Indicator selected from a Heat Loss Value of less than 7.5°C and a Touch Temperature of less than 40°C. 9. A method according to Claim 8 wherein the solution comprises a persalt bleaching agent. 10. A method according to Claim 9 wherein the persalt bleaching agent comprises an alkali metal perborate.

Inventors: WILLIAMS MICHAEL KEVIN, WILLIAMS, MICHAEL, KEVIN
Applicants: PROCTER & GAMBLE, WILLIAMS MICHAEL KEVIN, THE PROCTER & GAMBLE COMPANY, WILLIAMS, MICHAEL, KEVIN
Application year: 1998
Main classification: A61C17
IPC codes: A61C17