GB2272640A - Oral compositions - Google Patents

Abstract

Oral compositions contain a particulate massaging material, the particles of which are friable under conditions of use. A suitable particulate material is an agglomerated thickening silica e.g. commercially available Zeosyl, Sorbosil, Tixosil or Silox.

Description

ORAL COMPOSITION The present invention relates to oral compositions, particularly to massaging compositions such as toothpastes for use in the mouth, especially on the teeth and gums.

Conventional toothpaste compositions are used generally for the removal of pellicle, plaque and food debris from tooth surfaces and are applied by brushing which has the additional benefit of massaging the gums and adjacent mouth parts. In order to perform their cleaning function, known toothpastes contain abrasive materials, the particles of which are sufficiently hard to provide abrasive action but have a sufficiently small particle size for the composition not to give an unwanted gritty feel in the mouth when used. Polishing agents having smaller particle sizes than abrasives as such are also frequently used in known toothpaste compositions.

In recent times there has tended to be a trend towards toothbrushes having softer bristles than hitherto, because of the potential damage to the gums and other delicate intraoral membranes which can easily occur when brushing with toothbrushes having hard bristles, which have often been preferred over softer bristles for reasons of efficiency of abrasive cleaning of the teeth. With this increased trend towards softer bristles, however, it is increasingly difficult to achieve adequate massage of the gums and other mouth parts which is desirable for oral health, and this deficiency is not remedied by the abrasive and/or polishing particles of known toothpastes because of the too small particle size.

Moreover, a simple increase in the particle size of abrasive particles present in dental products is an unacceptable solution to the problem, because of the resulting permanent grittiness experienced by the user, which is undesirable for reasons of an aesthetically acceptable product, as well as being more likely to cause permanent damage to delicate intraoral surfaces during brushing.

There are known abrasive materials which are insoluble under saturation conditions in a given product, but which dissolve on aqueous dilution, for example potassium sulphate. However, such materials give only transient abrasive/massaging effects and often result in unpleasant tastes when delivered from a toothpaste composition for example.

It was therefore an aim of the present inventors to devise a massaging oral product which has good massaging properties on the teeth, gums and other mouth parts, whilst avoiding the inherent grittiness and potential damaging effects of large particle size abrasive materials.

Surprisingly, it has now been found that the above object may be fulfilled by using as the massaging material said particles which are friable under the conditions of use of the composition.

Accordingly, in a tirst aspect the present invention provides a massaging oral composition including a particulate massaging material, characterised in that the particles of the material are friable under conditions of use of the composition.

Compositions of the invention may, for example by use of a particulate material having suitable physical properties, be useful not only in providing a massaging effect on the gums or other surfaces inside the mouth, but also in aiding the removal from the teeth of pellicle, plaque and food debris as in conventional tooth cleaning or polishing. In the context of the present invention, therefore, the term "massaging" is not limited to a non-abrasive surface massaging effect, but may also embrace soft or mild abrasive/polishing action. The cleaning/polishing effect of compositions of the invention may if desired be enhanced by the optional use of conventional abrasive, polishing or other cleaning materials used in known toothpastes or other dental care compositions.

The invention will now be described in detail.

In accordance with the invention, when an oral composition such as a toothpaste is massaged in the mouth, preferably with brushing, the shear and/or crush forces which are created are sufficient to cause the particles of massaging material to break up after a period of time, preferably a short period of time, whereby the gritty feel experienced by the user is eliminated.

Preferably, the particles of massaging material are friable under shear and/or crush forces of a magnitude near or towards an upper limit of those created during a normal brushing regime of the oral composition in which the particles are incorporated.

Since the forces created at any particular location during such a regime are constantly varying and may only rarely reach a maximum, this may have the effect of delaying the onset of break up of the particles, so that there is a period at the beginning of the use regime when the particles remain whole and are able to perform their massaging function with maximum effect. Thus, the massaging power of the colposition may be controlled to some extent by the physical strength of the particles.

More generally however, it is likely to be sufficient for the massaging particles to be friable merely within the range of shear and/or crush forces normally produced in the relevant brushing regime, since the considerably variable forces produced at a particular location over time enable at least some of the particles to survive intact long enough to perform their massaging function to a satisfactory degree.

It is even possible to tailor the breakdown time of the particles, such as to control the contact time for a given duration of brushing of the composition, by controlling the average crush strength of the particles, for example by selecting a particular type or source of the particulate material and/or the manner in which any structural modification is carried out in the manufacturing process (as discussed further below).

Time and pressure related loss of palpability of the particles may provide the further advantage of an intraoral signal that sufficient brushing has taken place, and thus encourage good or even improved brushing practice and efficiency.

The strength of the particles may be measured as single particle crush strengths or by uniaxially confined compaction techniques. In the latter method, average particle strengths can be expressed as the Ltidde and Kawakita Relationship, as described in Powder Tech.

(1970/71), 4, 61-68, "Some considerations on powder compression equations", K. Kawakita & K. -H. Ludde (the disclosure of which is incorporated herein by reference).

We have found that particles exhibiting Lüdde and Kawakita strengths in the range of from about 5 to about 40 MPa (at 50% relative humidity and 294K), for example, more preferably in the rarge of from about 10 to about 35 MPa, are suitable for use in the present invention.

The particle size of the material may be any size which results in a satisfactory massaging effect on the teeth, gums and/or other intraoral surfaces. Particle sizes in the range of fror about 0.03 to about 3 mm are preferred, more preferably from about 0.05 to about 2 mm, even more preferably from about 0.1 to about 1 mm.

When the massaging particles break up under the action of shear and/or crush forces, the resulting average particle size (diameter) will typically be less than about 40 microns. Such reduced particle sizes will generally avoid any feeling of grittiness in the mouth.

Although not wishing to be bound by theory, it may also be possible in certain cases that even when broken up to this order of particle size, the material still retains some massaging function if continued to be massaged or worked by further brushing for example, and indeed may possibly even act as a polishing agent once it has fulfilled its primary massaging function.

The particulate material used in the invention may be any material which is sufficiently hard to perform a massaging function, yet has a structure which exhibits friability and enables the particles to break up under conditions of normal use of the composition in which they are incorporated.

Suitable materials include certain silicas, aluminas and other crystalline or amorphous materials having abrasive and/or massaging properties.

Particularly preferred are certain amorphous silicas, such a material generally being considered as inert and therefore suffering from no or only few safety problems.

One preferred massaging particulate material suitable for use in the invention is a structurally modified thickening silica, for example derived from the thickening silica sold under the trade mark Sident 22S (ex Degussa). Other suitable silicas include for example Zeosyl 200 (ex Zeofinn), Sorbosil TC 15 (ex Crosfield Chemicals), Tixosil 333 (ex Rhone-Poulenc), Silox 15X (ex W.R. Grace).

For use in the present invention, these commercially available particulate silicas may be structurally modified by pre-agglomeration, for example by exposure to moisture e.g. water, and subsequent drying.

A characteristic feature of these amorphous silicas which makes them suitable for pre-agglomeration in this manner is their very low primary particle size which is typically in the range of from about 0.01 to 0.2 microns, more usually from about 0.01 to 0.1 microns and most typically in the region of about 0.05 microns, and also their high pore volumes, typically in the range of from about 1 to 3 cm3/g, more usually in the region of about 2 cm3/g (as measured by mercury porosimetry and BET nitrogen techniques). Surface areas, measured for example by nitrogen adsorption, may preferably be in the range of from about 100 to about 300 m2g-1, more preferably in the region of about 250 m2g-l.

Owing to the porous nature of the agglomerated silica particles, it is possible for them to act as delivery vehicles for various substances such as colouring pigments, flavours, perfumes or other cosmetic or therapeutic dental and/or oral actives e.g. fluoride compounds, antibacterial agents, anti-caries agents, etc. Such substances may be contained within the pores of the material (e.g. introduced therein by conventional techniques) and, as the particles break up during use of the composition, released therefrom when the composition is used in the mouth, e.g. upon brushing.

Without intending to be limited by theory, it is believed that the above-mentioned pre-agglomeration under exposure to water entails, inter alia, the formation of some siloxane bridges (by condensation) and/or hydrogen bonds between adjacent silica particles, both of these resulting from the presence of exposed hydroxyl groups on the silica surface.

Subsequent drying of the modified structure thus formed produces particles of a considerably larger size, but which are friable under relatively low shear forces so as to break up into smaller constituent parts by breaking of the siloxane bridges and/or hydrogen bonds formed in the pre-agglomeration step.

Suitable industrial processes for forming structurally modified particulate massaging materials such as that described above include: spray drying from a body of the particulate material wetted with a suitable amount of water or other volatile liquid; granulation, of a similar nature to that used in the preparation of solid detergents in granular form; and pressure compaction. Such processes are well known in the art. One preferred example however, for the purpose of illustration only, is as follows: Approximately 1000 cm3 of Sident 22S is placed in a double bladed high speed mixer. Then, with the motor running, water is added until a critical point is reached when the silica changes from a free flowing powder to agglomerated particles. The volume of water required varies, depending on the initial moisture content of the silica.The range of about 170 to about 240 cm3 of water may be typical for 1000 cm3 of Sident 22S. The agglomerated particles are then dried.

In the massaging oral compositions according to the present invention, the level of particulate material may be wide ranging, for example depending upon the physical form of the desired end product.

Compositions according to the invention may be solids, e.g. similar in form to conventional tooth powders, or pastes, creams or gels, e.g. like conventional toothpastes, or possibly even liquids.

Particularly preferred compositions of the invention are in the form of pastes, gels, creams or liquids, the exact physical properties of which may be controlled for example by suitable adjustment of the solid to liquid ratio and/or the viscosity of the liquid phase, e.g. by selecting appropriate contents of adjunct components, as described further below.

In the particularly preferred compositions of the invention the particulate massaging material should be insoluble in the medium of the composition into which it is incorporated. In this context, "insoluble" means having sufficient insolubility at ambient temperature that the solid particles of material remain undissolved or substantially undissolved in the composition such that their friability under the conditions of use of the composition and thus their ability to perform their massaging function are not deleteriously affected.

Preferably, the level of insolubility of the particulate material extends to its insolubility in the oral environment in which the composition is used, which may frequently contain higher levels of water than for example a toothpaste, owing to the presence of saliva and added water frequently used in the brushing regime.

In preferred embodiments of the invention, the particulate material is present in the compositions in an amount of from about 1 to about 99% by weight, more preferably from about 2 to about 60%, even more preferably from about 3 to about 40%. In liquid compositions the latter preferred range is particularly suitable. In paste compositions of the invention, the particulate material is preferably present in an amount of from about 1 to about 10% by weight, more preferably from about 1 to about 5%, sven more preferably from about 2 to about 4%.

The massaging oral compositions of the invention may contain one or more additional components, as will now be described.

Oral compositions of the invention preferably comprise one or more surfactants, preferably selected from anionic, nonionic, amphoteric and zwitterionic surfactants, and mixtures thereof, all being suitable for dental and/or oral use.

Suitable anionic surfactants may include soaps, alkyl sulphates, alkyl ether sulphates, alkaryl sulphonates, alkanoyl isethionates, alkyl succinates, alkyl sulphosuccinates, N-alkoyl sarcosinates, alkyl phosphates, alkyl ether phosphates, alkyl ether carboxylates, and alpha-olefin sulphonates, especially their sodium, magnesium, ammonium and mono-, di- and triethanolamine salts. The alkyl and acyl groups generally contain from 8 to 18 carbon atoms and may be unsaturated. The alkyl ether sulphates, alkyl ether phosphates and alkyl ether carboxylates may contain from one to 10 ethylene oxide or propylene oxide units per molecule, and preferably contain 2 to 3 ethylene oxide units per molecule.

Examples of preferred anionic surfactants may include sodium lauryl sulphate, sodium dodecylbenzene sulphonate, sodium lauroyl sarcosinate and sodium coconut monoglyceride sulphonate.

Nonionic surfactants which may be suitable for use in compositions of the invention include sorbitan and polyglycerol esters of fatty acids.

Amphoteric surfactants which may be suitable for use in compositions of the invention include betaines and sulphobetaines, for example.

The surfactant(s) may be present in the oral compositions of the invention in a total amount of up to about 30% by weight, preferably from about 0.1 to about 10% by weight, more preferably from about 1 to about 3% by weight.

Water is another preferred component of the oral compositions of the invention and may be present in an amount of from about 1 to about 90% by weight, preferably from about 10 to about 50%, more preferably from about 15 to about 40%.

Toothpastes and creams of this invention may also contain humectants, for example polyols such as glycerol, sorbitol syrup, polyethylene glycol, lactitol, xylitol and hydrogenated corn syrup. The total amount of humectant, if present, may be for example in the range of from about 10 to about 85% by weight of the composition.

In the oral compositions of the present invention it is particularly preferred that one or more thickening agents and/or suspending agents are included, in order to give the composition the desired physical properties (e.g. whether a paste, cream or a liquid) and in order that the particulate material remains stably dispersed throughout the composition.

A particularly preferred means for thickening the oral compositions of the invention is by the inclusion of conventional thickening materials such as thickening silicas, examples of which have already been mentioned above in the context of a raw material from which may be derived the massaging particles which characterise the invention.

Other suitable suspending/thickening agents are well known in the art and include for example polyacrylic acid, copolymers and cross-linked polymers of acrylic acid, copolymers of acrylic acid with a hydrophobic monomer, copolymers of carboxylic acidcontaining monomers and acrylic esters, cross-linked copolymers of acrylic acid and acrylate esters, esters of ethylene glycol or esters of polyethylene glycol (e.g. fatty acid esters thereof), heteropolysaccharide gums, and cellulose derivatives such as sodium carboxymethyl cellulose.

Particularly suitable thickening agents are heteropolysaccharide gums such as xanthan gum and guar gums.

The thickening agent and/or suspending agent (which may be used singly or as mixtures of two or more such materials) may be present in the composition in a total amount of from about 0.1 to about 50% by weight; preferably from about 5 to about 15% for silica thickening agents; preferably from about 0.1 to about 5% for polymer suspending agents.

The compositions of the invention may contain one or more other components conventionally found in oral compositions. Suitable additional ingredients include: flavouring substances, e.g. peppermint, spearmint; artificial sweeteners; perfume or breath freshening substances; pearlescing agents; peroxides, e.g.

hydrogen peroxide; opacifiers; pigments and colourings; preservatives; moisturising agents; fluoridecontaining compounds; anti-caries agents; anti-plaque agents; therapeutic agents such as zinc citrate, Triclosan (ex Ciba Geigy); proteins; salts; pH adjusting agents; polishing agents, such as abrasive silicas, chalks, hydrated aluminas, calcium phosphates, titanium dioxide; etc.

Compositions in accordance with the present invention may be made by conventional methods of preparing oral compositions. Pastes and creams may be prepared by conventional techniques using high shear mixing systems under vacuum, for example, with the particulate material which characterises the invention being added to the pre-mixed base composition in a secondary step comprising dispersing/mixing in thereof under low shear conditions.

It is generally important in the preparation of compositions in accordance with the invention that any mixing step carried out is done at a sufficiently low shear and/or speed such that the particulate material of the invention does not experience forces sufficiently great to cause the particles to fracture.

The massaging oral compositions of the invention may be used in a similar way to conventional oral compositions such as toothpastes, i.e. a suitable amount of the composition is applied to a brush, or even directly into the mouth, if necessary with the addition of some water, and the slurry worked on the teeth, gums and/or other mouth parts as necessary or desired, so as to exert the massaging properties of the particulate material onto the intended intraoral surfaces. Owing to the friability of the particulate material, any grittiness experienced by the user will soon, perhaps rapidly, disappear, so that once the particulate material has performed its massaging function, the composition is left free for further massaging or working in, as necessary, for example for delivering one or more additional benefits attributable to other components in the composition. Finally, the mouth may be rinsed with water, as with normal oral products. This application procedure may be repeated as many times as desired.

The invention is further illustrated by the following Examples.

Examples Example 1 (Toothpaste) Ingredient %wt Abrasive silica gel(1) 4.0 Thickening silicae 2 ) 10.0 Massaging particles of the invention (150-500p) 3.0 Sorbitol (70% syrup) 45.0 PEG 1500 5.0 Sodium lauryl sulphate 1.5 Xanthan gum 1.0 Sodium monofluorophosphate 0.8 Saccharin 0.2 Titanium dioxide 1.0 Peppermint flavour 1.0 Water to 100 (1) Gasil 200TP ex Crosfield Chemicals (2) Sorbosil TC15 ex C; ;ssfield Chemicals Example 2 (Toothpaste) Ingredient %wt Thickening silica 3 ) 11.5 Abrasive/massage particles of the invention (500-700p) 2.5 Sorbitol (70% syrup) 45.0 PEG 1500 5.0 Sodium lauryl sulphate 1.5 Xanthan gum 1.5 Sodium monofluorophosphate 0.8 Saccharin 0.2 Titanium dioxide 1.0 Spearmint flavour 1.0 Water to 100 (3) as in Example 1

Claims (16)

1. CLAIMS 1. A massaging oral composition including a particulate massaging material, characterised in that the particles of the material are friable under conditions of use of the composition.
2. 2. An oral composition according to claim 1 which is in the form of a toothpaste or dental cream, wherein the particles of the said material are friable under conditions of brushing the composition on the teeth, gums or other mouth parts.
3. 3. An oral composition according to claim 1 which is in the form of a powder, wherein the particles of the said material are friable under conditions of brushing of the composition on the teeth, gums or other mouth parts.
4. 4. An oral composition according to claim 1 which is in the form of a liquid product, wherein the particles of the said material are friable under conditions of brushing of the composition on the teeth, gums or other mouth parts.
5. 5. An oral composition according to any one of claims 1 to 4, wherein the particles of the said material are friable and have a Ltidde & Kawakita strength (as herein defined) in the range 5 to 40 MPa at 50% relative humidity and 294K.
6. 6. An oral composition according to any preceding claim, wherein the said particulate material has a particle size in the range 0.03 to 3 mm.
7. 7. An oral composition according to any preceding claim, wherein the particies of the said material break up, under the conditions of use of the composition, into particles having an average size of less than 40 microns.
8. 8. An oral composition according to any preceding claim, wherein the said particulate material is a silica.
9. 9. An oral composition according to claim 8, wherein the said particulate material is a structurally modified thickening silica obtained by pre-agglomeration and subsequent drying.
10. 10. An oral composition according to any preceding claim, wherein the said particulate material is that obtained by any of the following: spray drying from a body of particulate material wetted with a suitable amount of water or other volatile liquid; granulation; pressure compaction.
11. 11. An oral composition according to any preceding claim, wherein the said particulate material is present in the composition in an amount of from 1 to 99% by weight.
12. 12. An oral composition according to any preceding claim, wherein the particulate material is insoluble in the composition and/or the oral environment in which the composition is used.
13. 13. An oral composition according to any preceding claim, further comprising one or more surfactants selected from anionic, nonionic, amphoteric and zwitterionic surfactants, and mixtures thereof.
14. 14. An oral composition according to any preceding claim, further comprising one or more additional ingredients selected from: thickening agents, suspending agents, humectants, polishing agents and other substances conventionally found in oral compositions.
15. 15. A method of massaging the teeth, gums and/or other intraoral surfaces, comprising applying thereto and massaging or working thereon an oral composition according to any preceding claim.
16. 16. Use as an oral massaging material of a particulate material of which the particles are friable under conditions of use of the composition.