Patent Description:
Accumulation or build-up of dental plaque may lead to gingivitis. A toothbrush is the most widely used implement for controlling plaque. Toothbrushes serve to clean the teeth by removing plaque and debris from the surfaces which includes the curved outer surfaces and the interdental surfaces which are between the teeth. It is believed that toothbrushes having multilevel bristle contour allow better interdental penetration by the bristles to thereby ensure effective plaque removal.

The following is a brief account of the attempts made at designing of toothbrushes with respect to configuration and placement of bristles or tufts of bristles on the brush head, in order to improve the cleaning.

One such attempt was made in <CIT>) which discloses a bristle pattern for penetrating into the interproximal spaces between the teeth and for enhanced cleaning of the teeth surfaces. It discloses a bristle pattern including a trim profile in the form of an inverted "V" with its apex at the centre of the head.

<CIT>) discloses a toothbrush having a bristle profile for improved cleaning action and access to the teeth and gums. The bristle configuration includes a convex group of bristles located at the heel of the head, the teeth engaging ends of which lie in a convex line, another convex group of bristles located at the toe of the head and a group of concave bristles intermediate the two convex group of bristles and having its teeth engaging ends which lie in a concave line.

Other attempts were concerning the shape and configuration of the bristles. Bristles are also referred to as filaments.

<CIT>discloses the use of filaments having a non-circular cross-section. The filaments have a trilocular, tetralocular, trilobular, rectangular or hexagonal cross section. These toothbrushes are better at plaque removal.

<CIT>) discloses bristles having a spiral groove along their longitudinal axis to increase the abrasiveness and expand the surface area of the bristle used in cleaning. The bristles have shallow spiral groove along its longitudinal axis on account of which the entire bristle, including the tip of the bristle and its longitudinal axis, functions as a part of the cleaning surface of the bristle. The surface area of the bristle used in cleaning is expanded. The diameter of each groove is approximately one fourth of the diameter of the bristle.

<CIT>) discloses a toothbrush that cleans effectively without contact of distal ends of bristles with the teeth. Plurality of circular recesses are dispersively formed on the outer surface of wires of the bristles. When the wires are brought into contact with the surface of teeth they are elastically deformed and inserted into gaps between the teeth, so that the gaps are brushed. Edges of the recesses project to the surface of the teeth when the wires are deformed, and the sharp edges rub the surface of the teeth along the reciprocation of the toothbrush as if scraping off the stain by a scraper, so that the stain on the surface of the teeth can be securely removed in a short period of time. grooved bristle is combined into tufts and mounted on a suitable platform so that when the surface to be cleaned is scrubbed with a toothbrush having the improved bristle of the invention the bristles twist and bend and in the process the shaft of the bristle scrapes on the surface to be cleaned and agitates the fluid in and around the area to be cleaned thereby increasing the cleaning ability of the brush.

<CIT>) discloses a makeup brush bristle material constituted by S-twisted or Z-twisted monofilaments made of a synthetic resin. Cross-section of the monofilaments in a direction orthogonal to an axis of fiber has a cocoon shape. The cocoon shape refers to a rice bale shape resembling a cocoon spun by a silkworm; oblong with a gradual constriction at the center portion (mid body portion).

It is known that the teeth often contact with a variety of staining agents which include many food and beverage preparations. Most of the times, this contact cannot be avoided, as a result the teeth get stained over a period.

The problem of stains can be addressed by use of specially formulated toothpastes. Alternatively, there are toothbrushes meant for this purpose.

For example, <CIT>) discloses the use of core-&-sheath bristles.

<CIT> discloses a cosmetic brush that has a longitudinal stem and a plurality of bristles, each bristle extending from a base associated with the stem and terminating with a free end, each bristle having external walls and a longitudinal axis. Each bristle has at least one external depression oriented in a direction substantially parallel to the longitudinal axis of the selected bristle.

<CIT>discloses a filament for an oral care implement that has a longitudinal axis and a substantially cross-shaped cross-sectional area extending in a plane substantially perpendicular to the longitudinal axis. The cross-shaped cross-sectional area has four projections and four channels. The projections and channels are arranged in an alternating manner. Each channel has a concave curvature formed by neighboring and converging projections. The concave curvature has a radius, and each projection is end-rounded thereby forming a curvature.

We have determined that the problems of stains could be better addressed by use of oral care implements that comprise filaments in accordance with the present invention. Filaments are also interchangeably referred to as bristles.

An object of the present invention is to provide an oral care implement which can provide better stain removal, preferably better removal of at least some of the stains such as tea, coffee, wine amongst other stains commonly associated with teeth.

In accordance with a first aspect of the invention disclosed is a filament <NUM> made of a material suitable for use as bristles of an oral care implement, where said filament has non-circular cross-section in the direction orthogonal to its axis, where axis means the longitudinal axis of the filament, characterised in that the cross-section is shaped like a double-concave lens having non-linear edges that define the maximum width of said filament, wherein said non-linear edges are curved and represent arcs of a circle of radius (r) and the total breadth of the filament is represented by (t) where (t) is the diameter of the same circle of radius (r), and wherein area of said cross-section is constant along the length of the filament.

In accordance with a second aspect of the invention disclosed is brush head for a toothbrush comprising filaments of the first aspect.

In accordance with a third aspect of the invention disclosed is a toothbrush comprising filaments of the first aspect.

<FIG> is a cross-sectional view of an embodiment of a filament in accordance with the invention.

<FIG> is a cross-sectional view of an embodiment of a filament in accordance with the invention. The filament (<NUM>) is made of a material suitable for use as bristles of an oral care implement. The filament has a non-circular cross-section in the direction orthogonal to its axis. By axis is meant the longitudinal axis of the filament. The cross-section is shaped like a double-concave lens having non-linear edges (<NUM>, <NUM>) that define the maximum width of the bristle. The non-linear edges are curved and represent arcs of a circle of radius (r). The total breadth of the filament is represented by (t) and (t) is the diameter of the same circle of radius (r). The maximum width is indicated as (w).

As used herein the term "comprising" encompasses the terms "consisting essentially of" and "consisting of". Where the term "comprising" is used, the listed steps or options need not be exhaustive. Unless otherwise specified, numerical ranges expressed in the format "from x to y" are understood to include x and y. In specifying any range of values or amounts, any particular upper value or amount can be associated with any particular lower value or amount. Except in the examples and comparative experiments, or where otherwise explicitly indicated, all numbers are to be understood as modified by the word "about". All percentages and ratios contained herein are calculated by weight unless otherwise indicated. As used herein, the indefinite article "a" or "an" and its corresponding definite article "the" means at least one, or one or more, unless specified otherwise. The various features of the present invention referred to in individual sections above apply, as appropriate, to other sections mutatis mutandis. Consequently, features specified in one section may be combined with features specified in other sections as appropriate. Any section headings are added for convenience only and are not intended to limit the disclosure in any way. The invention is not limited to the embodiments illustrated in the drawings. Accordingly, where features mentioned in the claims are followed by reference numerals, such numerals are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting to the scope of the claims. The examples are intended to illustrate the invention and are not intended to limit the invention to those examples per se.

The filament of the invention is made of a material suitable for use as bristles of an oral care implement. The filament has non-circular cross-section in the direction orthogonal to its axis. The term axis means the longitudinal axis of the filament. The term filament and bristles are used interchangeably in this specification.

Usually the filaments of a toothbrush or other oral care implements have a circular cross-section. In the direction orthogonal to its axis implies the direction perpendicular (at right angle) to the longitudinal axis of the filament.

In the filament of the present invention, the cross-section is shaped like a double-concave lens having non-linear edges that define the maximum width of said bristle. The concept of lenses is discussed in Physics. A double concave lens is symmetrical across both its horizontal and vertical axis. The two faces of a double concave lens can be thought of as originally being part of a sphere. In a typical double concave lens, the edges that define the maximum width are linear. However, in the filament according to the present invention, the cross-section is shaped like a double-concave lens having non-linear edges that define the maximum width of the bristle. The non-linear edges are curved and represent arcs of a circle of radius (r) and the total breadth of the filament is represented by (t) where (t) is the diameter of the same circle of radius (r). The area of the cross-section is constant along the length of the filament. The filament is preferably devoid of a S-twist or Z-twist along its axis. Filaments having S- and Z-twists are disclosed in <CIT>.

Preferably the oral care implement of the invention is a toothbrush, an interdental brush, a toothpick or floss. The toothbrush is preferably a manual toothbrush. Alternatively, it is an electric toothbrush.

It is preferred that the material is a natural material, a synthetic polymer or a biopolymer.

When the material is a synthetic polymer it preferably is a thermoplastic material selected from poly-oxymethylene , polyethyleneglycol , polypropyleneglycol, polytetramethyleneglycol, polyethyleneoxide, polypropyleneoxide , polytetrahydrofuran, polytetramethyleneetherglycol , a polyalkene, a polyalkane, a polypeptide, a polyamide, a polyamine or a polyester.

It is preferred that the polyester is polyethylene terephthalate (PET), polyethylene furanoate (PEF), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polyethylene naphthalate (PEN), Poly (<NUM>-hydroxy butyrate- co-<NUM>-hydroxyvalerate) (PHBV), and a polycondensate of <NUM>- hydroxybenzoic acid and <NUM>-hydroxynaphthalene-<NUM>-carboxylic acid (VECTRAN).

It is preferred that the polyamide is nylon <NUM> or nylon <NUM>,<NUM>. A preferred brand of nylon is <NUM>, <NUM> nylon available from E. Du Pont de Nemours and Company marketed under the tradename of TYNEX®.

The filament preferably has a thickness (breadth) of <NUM> to <NUM>, more preferably <NUM> to <NUM>, still preferably <NUM> to <NUM> and still more preferably <NUM> to <NUM>. The filament may be of any colour.

It is preferred that the filament comprises a benefit agent or an active agent. A benefit agent is usually added for a marketing claim purpose, such as a claim directed to enhanced cleaning, which need not be substantiated.

An active agent is usually included in quantities sufficient for a desired effect that can be proven scientifically with clinical studies or similar tests. The same material may be included in quantities sufficient to call it a benefit agent or an active agent, depending on the level or wt% of incorporation into the bristles. A variety of methods are known that enable the inclusion of one or more of such agents in filaments.

A wide variety of anti-microbial active compounds may be employed. These actives may generally be classified as halogenated hydrocarbons, quaternary ammonium salts and sulfur compounds. Halogenated hydrocarbons include halogenated derivatives of salicylanilides, carbanilides, bisphenols, diphenyl ethers, anilides of thiophene carboxylic acids and chlorhexidines. Quaternary ammonium compounds include alkyl ammonium, pyridinum, and isoquinolinium salts. Sulfur active compounds include thiuram sulfides and dithiocarbamates.

Among the halogenated salicylanilides there may be mentioned the following derivatives:.

The bis-phenols are represented by the following:.

Examples of quaternary ammonium compounds are:.

Examples of the thiocarbamates and the thiuram sulfides are:.

From the viewpoint of safety and effectiveness the preferred antibacterial agents are as follows:.

Most preferred among the halogenated hydrocarbons is <NUM>,<NUM>,<NUM> 'trichloro-<NUM>-hydroxydiphenyl ether (known generically as) triclosan and among the quaternary ammonium salts is cetyl pyridinium chloride. Indeed, combinations of both of these active substances allow for a broad range of anti-microbial activity in the toothbrushes of the present invention.

In accordance with a second aspect disclosed is a brush head for a toothbrush comprising filaments of the first aspect. A brush head may comprise said filaments wherein a certain group of filaments in a so-called tuft having a cross-section as disclosed herein. In such embodiments of the invention, the bristles may be used to clean a user's teeth and mouth. Different embodiments of the invention may include different bristle designs to achieve different types of cleaning, e.g., standard, sensitive or whitening. The user may interchange heads with different bristle designs to achieve different types of cleaning while using the same handle. Therefore, the invention may allow a user to have greater flexibility in their teeth-cleaning habits without having to own multiple different toothbrushes.

In accordance with a third aspect disclosed is a toothbrush comprising filaments of the first aspect. Toothbrushes according to the present invention may have a wide variety of shapes and designs. A typical toothbrush is characterized by a head having bristles, in the form of tufts, a neck with first and second ends and a handle with front and rear ends. The brush may or may not comprise additional features like elastomeric members for better cleaning, grip-enhancing features, and tongue cleaner at the back of the head. A suitable tongue cleaner has been described in <CIT>).

All parts of toothbrushes according to the invention are preferably unitarily constructed together from an identical plastic material. The most preferred plastic material is polyolefin such as low-density polyethylene. Advantageously the plastic material will have a Melt Index greater than <NUM>, preferably from <NUM> to <NUM>, optimally from <NUM> to <NUM>/<NUM> minute.

The dimensions of a toothbrush according to the invention are maintained such that the toothbrush preferably has a length in the range <NUM> to <NUM>, the width of the handle is in the range <NUM> to <NUM> and the thickness is in the range <NUM> to <NUM>. Thus the surface area to the volume ratio which is an important parameter in determining the ergonomic properties of the toothbrush is maintained similar or superior to that of a standard quality toothbrush. The surface area to the volume ratio of the toothbrush according to the present invention is preferably in the range <NUM> to <NUM> whereas the ratio for standard quality brushes known in the art is upto <NUM>.

The plastic materials that are used to form the toothbrush is preferably selected from various grades of polypropylene, styrene acrylonitrile, polymethyl methylacrylate, acrylonitrile butadiene styrene or thermoplastic elastomers. The most preferred materials are polypropylene and thermoplastic elastomers.

An oral care implement can be made by any process which is generally understood by those skilled in the art. The bristle or filaments may be implanted in the bristle bearing face of the head in tufts using either typical staple technology or by means of fusion. In a staple set bristling process, a small group of bristles is folded over a nickel silver staple and forced into a cylindrical hole in the brush which forms a bristle tuft. After bristling, the tufts are polished by a series of sanding discs which removes any burrs or sharp edges. The toothbrush head in which the bristles are anchored using staple set bristling process requires deeper hole and comparatively thicker head. Alternatively the bristles may be anchored to the bristle bearing face of the head using other non-staple technology. One such process involves fusing the bristle tufts into the bristle bearing face of the head by heating both the bristle tufts and the head which are then brought together. In another known process the ends of the bristle tufts are pre- positioned in an injection mold prior to the introduction of the material forming the toothbrush head, the material is subsequently injected about the ends of the bristle tufts, locking the bristle tufts in place in bristle bearing face of the head. After tufting the bristles are cut to the desired profile in a trimming step followed by rounding the tip free end of the bristles. The toothbrush is then packaged.

Claim 1:
An oral care implement which is a toothbrush, an interdental brush, a toothpick or floss ,comprising a filament (<NUM>) made of a material suitable for use as bristles of an oral care implement, where said filament has non-circular cross-section in the direction orthogonal to its axis where axis means the longitudinal axis of the filament, characterized in that the cross-section is shaped like a double-concave lens having non-linear edges (<NUM>, <NUM>) that define the maximum width (w) of said filament, wherein said non-linear edges are curved and represent arcs of a circle of radius (r) and the total breadth of the filament is represented by (t) where (t) is the diameter of the same circle of radius (r) and wherein area of said cross-section is constant along the length of the filament.