Interdental brush

Abstract

An interdental brush particularly suited for use to clean between adjacent teeth, comprising a handle having a body and an end portion and a brush portion. The brush portion comprises an elongate stem having a distal bristled portion including a plurality of bristles extending from the elongate stem and a proximal root portion to be embedded in the handle to secure the brush portion to the handle. The root portion of the elongate stem is embedded in the end portion such that the brush portion projects from the end portion of the handle. The end portion may be resiliently flexible to distribute bending deformation along the stem including the root portion of the stem within the neck during use of the interdental brush.

Description

INTERDENTAL BRUSHField

[0001] The present invention relates to dental brushes, and more particularly although not exclusively to interdental brushes.Background

[0002] Interdental brushes typically comprise a wound wire stem having a plurality of bristles projecting therefrom. The wire stem includes an end portion embedded in a handle so as to be fixed relative thereto. The handle typically comprises a plastics material, which is moulded about the end portion of the wire stem so that the wire stem is secured thereto. In some instances, an adhesive may be used to secure the end portion of the wire stem with respect to the handle. An example of such an interdental brush is disclosed in the Applicant’s earlier Australian Patent, Australian Patent No. 2020103663, the contents of which is incorporated by reference herein in its entirety.

[0003] A problem with certain interdental brushes is that, after repeated use, the wire stem may exhibit fatigue proximate its end portion, and more particularly, at or near a bending site located generally where the wire stem projects from the handle. When the wire stem is bent repeatedly (typically due to an adjustment or change in the bend angle during use of the interdental brush to better suit access to posterior teeth and for straightening to replace the brush cap), the stress concentration at the bend site causes localised deformation and the formation of small cracks in the wire stem. These small cracks may continue to grow with repeated use of the interdental brush until the wire stem fails. When the wire stem fails, the wire stem will typically separate from the handle.

[0004] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to at least provide a useful alternative thereto.

[0005] Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction, or that this prior art could reasonably be expected to be understood, regarded as relevant, and / or combined with other pieces of prior art by a skilled person in the art.Summary of Invention

[0006] In a first aspect the invention provides an interdental brush, comprising: a handle, said handle comprising a body and an end portion; a brush portion, said brush portion comprising an elongate stem having a distal bristled portion including a plurality of bristles extending from the elongate stem, and a proximal root portion to be embedded in the handle to secure the brush portion to the handle; wherein the root portion of the elongate stem is embedded in the end portion such that the brush portion projects from the end portion of the handle.

[0007] Preferably, the end portion is resiliently flexible.

[0008] Preferably, the body is overmolded about the elongate stem such that the elongate stem extends through the end portion.

[0009] Preferably, the body and the end portion are formed of a uniform composition or material.

[0010] Preferably, the body comprises a transition portion that tapers toward a neck forming the end portion.

[0011] Preferably, the elongate stem extends through the neck such that the neck provides a covering sheath around the stem with such covering having a sheath thickness of between 0.01 mm and 0.5 mm, preferably a thickness of between 0.1 mm to 0.3 mm and more preferably a thickness of between 0.1 mm to 0.2 mm. The thickness of the sheath covering surrounding the stem is selected depending on the gauge / thickness / diameter of the twisted wire stem to provide an appropriate deformation of the neck during deformation of the stem in use.

[0012] Preferably, the body and neck are formed of a material having a flexural modulus in the range of 300 MPa to 2700MPa and preferably in the range of 700MPa to 1300MPa more preferably around 900 MPa.

[0013] Preferably, the body and neck are formed of a thermoplastic polymer preferably a polypropylene.

[0014] Preferably, the stem is formed of a uniform composition.

[0015] Preferably, at least a portion of a length of the stem is treated to modify a physical property of said length.

[0016] Preferably, the stem includes a first portion and a second portion and wherein a physical property of the material of the first portion differs from the same physical property of the material of the second portion.

[0017] Preferably, the physical property of the material is one or more physical properties selected from the group comprising: flexural modulus; fatigue strength; fatigue resistance; yield strength, stiffness, modulus of elasticity; ductility.

[0018] Preferably, the stem includes a metal.

[0019] Preferably, the stem is formed of a metal wire.

[0020] Preferably, at least a portion of the metal of the stem is heat treated to enhance the fatigue strength of the metal.

[0021] Preferably, at least a portion of the metal of the stem is chemically treated or irradiated to enhance the fatigue strength of the metal.

[0022] Preferably, the metal wire has a tensile strength in the range of 600MPa to 2000MPa and preferably 750MPa to HOOMPa.

[0023] In a second aspect, the invention provides a method of manufacturing an interdental brush as disclosed above, said method comprising the steps of: forming the brush portion; forming the handle, wherein the root portion of the elongate stem is embedded in the end portion such that the brush portion projects from the end portion.

[0024] Preferably, the body is overmolded about the elongate stem such that the elongate stem extends through the end portion.

[0025] Preferably, the methods include the step of modifying at least a portion of a length of the stem to alter a physical property of said length.

[0026] In another aspect, the invention provides a method of manufacturing a dental brush, comprising a brush portion and a handle, said method comprising the steps of: forming the brush portion, said brush portion comprising an elongate stem having a distal bristled portion including and a plurality of bristles extending from the elongate stem, and a proximal root portion to be embedded in the handle to secure the brush portion to the handle; forming a handle comprising a body and an end portion, wherein the root portion of the elongate stem is embedded in the end portion such that the brush portion projects from the end portion.

[0027] Advantageously, the end portion of the handle is resiliently flexible so as to resiliently bend during use of the dental brush. Preferably, the end portion is configured to bend generally in the direction of bending of the elongate stem. Advantageously, the bendable end portion of the handle acts to increase the radius of curvature of the elongate stem and particularly the root portion during bending and thus reduce a bending stress concentration applied to the elongate stem during use of the dental brush, which in turn increases the useful life of the elongate stem and thus the dental brush.

[0028] Advantageously, by overmolding the body about the elongate stem, the dental brush is a one-piece or unitary construction. Advantageously this simplifies the construction and reduces manufacturing steps while the resiliently flexible end portion enhances durability of the interdental brush.

[0029] Preferably, the body comprises a generally circular transverse cross-section. Preferably, the body includes the end portion. Preferably, the end portion comprises a neck. The neck preferably comprises a generally circular transverse cross-section. The neck is preferably disposed about the elongate stem. Preferably, a longitudinal axis of the elongate stem is coincident with a longitudinal axis of the neck. In one embodiment, the neck has a constant diameter. Alternatively, in another embodiment, the neck may have a variable diameter. For example, the neck may taper generally toward its distal end. Preferably, the neck may taper by a conical taper angle a between about 1° and about 8° toward its distal end adjacent the brush. More preferably, the neck may taper by a conical taper angle a between about 1° and about 5°toward its distal end. Still more preferably, the neck may taper by a conical taper angle a of about 2° toward its distal end. Preferably, a diameter of the neck is less than a diameter of a major portion of the body. Preferably the diameter at the distal end of the neck is approximately 0.2 to 1.0 mm greater than the diameter of the elongate stem and preferably between approximately 0.2 to 0.4 mm greater than a diameter of the elongate stem at the distal end of the neck adjacent to the brush. Preferably, the neck has a length of between approximately 2.0 mm to 3.0 mm.

[0030] The body preferably comprises a transition portion, which transitions into the neck. The transition portion preferably converges toward the neck. In other words, the transition portion preferably decreases in diameter toward the neck. The transition portion may be generally frustoconical in overall form. Preferably, a diameter of a proximal end of the transition portion is similar to the diameter of the major portion of the body, and a diameter of a distal end of the transition portion is similar to the diameter of the neck. Advantageously, the reduced diameter of the neck as compared to the diameter of the major portion of the body allows for the neck to resiliently bend with respect to a remainder of the body. The neck is preferably bendable by up to 90° from a longitudinal axis of the handle. The elongate stem is preferably configured to withstanding a 45° bending force comprising a 500 g weight vertically loaded at a distal end of the brush for more than 20 bends. The dental brush advantageously complies with and exceeds the ISO standard for interdental brush bend resistance to breakage (ISO / 16409).

[0031] Preferably, the neck includes a distal end face, which distal end face is a distal end face of the body. Preferably, the distal end face is arranged generally perpendicularly with respect to a longitudinal axis of the body. The end face preferably defines a shoulder, which shoulder is a portion of the end face disposed about the elongate stem except where the shoulder width or thickness is zero in which case there is no shoulder.

[0032] Preferably, the elongate stem comprises a pair of wire strands, which pair of wire strands are wound about each other to form a wound or twisted wire stem. Preferably, each of the plurality of bristles are engaged by the pair of wire strands forming the elongate stem so as to secure the plurality of bristles to the elongate stem. Preferably, the shoulder has a width or thickness of approximately 0.1 mm to 0.2 mm about the wire stem. Preferably, the wound wire stem has a length from the distal end face of the neck to the distal end of the brush of between approximately 6 mm and 25 mm.

[0033] Preferably, the body has a diameter of between 4 mm and 8 mm. Preferably, the body has a length of between 20 mm - 60 mm. More preferably, the body has a length of approximately 50 mm. Preferably, the body includes one or more grooves and / or one or more ridges in an outer surface thereof to aid in gripping the handle. The one or more grooves and / or one or more ridges are preferably arranged generally parallel to a longitudinal axis of the body.

[0034] Preferably, the body comprises a semi resilient thermoplastic such as polypropylene or polyethylene. The body may be coloured.

[0035] Preferably, the body includes a circumferential ridge configured to seat a portion of a cover or cap, which cover is configured to cover the wound wire stem. The cover may comprise a tube having open opposite longitudinal ends. The tube is preferably frictionally seated against the circumferential ridge to cover the wound wire stem so as to protect the wound wire stem and bristles when the dental brush is not in use. More preferably, either one of the opposite longitudinal ends of the tube may be frictionally seated against the ridge to removably secure the cover to the body. The tube may be opaque, transparent or translucent.

[0036] In some embodiments the interdental body includes a brush extending from each opposite end of the elongate body. Such brushes may be the same or different sizes.

[0037] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude other additives, components, integers, or steps.Brief Description of Drawings

[0038] The invention will be more clearly understood from the following description of one or more embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:

[0039] Figure 1 is a perspective view of a dental brush according to an embodiment of the present invention;

[0040] Figure 2 is a side view of the dental brush of Figure 1 displaying deflection of the stem and neck;

[0041] Figure 3 is a side detail view of a portion A of the dental brush shown in Figure 2;

[0042] Figure 4 is similar to Figure 2 showing the neck and stem undeflected;

[0043] Figure 5 is a side detail view of a portion B of the dental brush shown in Figure 4;

[0044] Figure 6 is a perspective of the dental brush of Figure 1 with its distal end portion partially cutaway;

[0045] Figure 7 is a side view of the dental brush shown in Figure 6;

[0046] Figure 8 is a detail view of the portion C shown in Figure 6; and

[0047] Figure 9 is a detail view of the portion D shown in Figure 7.Description of Embodiments

[0048] Figure 1 illustrates an interdental brush 10 according to an embodiment of the present invention. The interdental brush 10 is particularly suited for use to clean between adjacent teeth.

[0049] The interdental brush 10 is a one-piece or unitary construction and comprises a handle 12 and a brush portion 14 projecting from a distal end of the handle 12. In particular, the handle 12 comprises an elongate body 16 that is generally circular in transverse cross-section and which transitions into an end portion 18 at a distal end thereof. Advantageously, according to the invention, the end portion 18 is resiliently flexible by virtue of a reduced diameter so as to resiliently bend or deflect due to deflection of the interdental brush stem during use of the interdental brush 10, as shown in Figure 2.

[0050] According to an aspect of the invention, the end portion 18 has reduced bending stiffness relative to the handle portion 12. More particularly the reduced diameter of the end portion 18 with respect to the handle 12 advantageously provides a reduced bending stiffness relative to the handle portion 12 for a given material. In a preferred embodiment handle 12 is formed of a material having a flexural modulus of 900 MPa which provides adequate rigidity to the handle while simultaneously providing adequate flexibility to the end portion 18, to reduce the stress concentration and fatigue failure where the brush 10 emerges from the end portion 18. However,the handle may be formed of materials having a flexural modulus in the range 300 MPa to 2700MPa and more preferably 700MPa to 1300MPa.

[0051] Referring to Figure 4 and detailed view Figure 5 for example, the brush portion 14 comprises an elongate stem 20 and a plurality of bristles 22 projecting outwardly therefrom in a direction generally perpendicular to a longitudinal axis 23 of the elongate stem 20. The elongate stem 20 is sized and configured to be inserted between adjacent teeth of a user’s dental arch, and the bristles 22 are configured to engage against and remove matter located between the adjacent teeth during use of the interdental brush 10. The elongate stem 20 has a length of 6 - 25 mm, and has a diameter of approximately 0.25-1.2mm. The stem 20 includes a bristled portion 24 at a distal end thereof and a root portion 26 to be embedded in the body, and more particularly the end portion 18 of the body thereby to secure the brush portion to the handle.

[0052] Referring again to Figure 5, in this embodiment the elongate stem 20 is formed from wire strands twisted together. Specifically, the embodiment shown comprises a pair of wire strands 30, which are wound or twisted about each other to form the wound wire stem 20. Each of the plurality of bristles 22 are at least partially engaged between the pair of twisted wire strands 30 so as to secure the plurality of bristles 22 to the elongate stem 20. Due to the twisted wire stem, the bristles 22 form a circular helix 32 projecting generally radially from the bristled portion of the elongate stem 20 as can be seen in Figure 5 however may, in other embodiments form generally circular discs or other configurations and arrays

[0053] The wire strands 30 are a stainless steel or a metal alloy selected to provide a balance between sufficient rigidity, so that the bristled portion 24 retains its shape in use, and toughness, to prevent failure due to work hardening, particularly where the wire stem 20 projects from the handle 12 and is subject to bending forces in use. The wire typically has a tensile strength in the range of 600MPa to 2000MPa and preferably 650MPa to 1 lOOMPa.

[0054] Referring to Figure 5, the end portion 18 of the body 16 of the handle 12 comprises a neck 34. The neck 34 is generally circular in transverse cross-section and is disposed about at least a portion of a length of the elongate stem 20 (see also Figure 8) such that the stem extends through the neck. As shown in Figure 5, the longitudinal axis 23 of the elongate stem 20 is preferably coincident with a longitudinal axis 36 of the neck 34. With reference to Figure 5, the neck 34 has a length, L, of approximately 2.0 mm - 3.0 mm, and, as best seen in Figure 9, adiameter, D equal to the twisted wire diameter plus a sheath provides a covering, surrounding the stem and having a sheath width or sheath thickness t.

[0055] In some embodiments the neck 34 may be of a consistent cross section and / or diameter D wherein the sheath thickness t is constant so as to provide a cylindrical neck. Preferably the sheath thickness t is between approximately 0.01 mm and 0.5 mm, preferably a thickness of between 0.1 mm to 0.3 mm and preferably between 0.1 mm to 0.2 mm. In this embodiment however, the neck 34 tapers toward its distal end by approximately 0.5° to 2.5° and preferably 1° from a longitudinal axis 36 of the neck 34 providing a conical taper angle a of approximately 1° to 5° and preferably 2° of the neck. Thus, the diameter D of the neck 34, and sheath thickness / , gradually decreases toward its distal end where the sheath thickness t is a minimum of between approximately 0.01 mm and 0.5 mm, preferably a thickness of between 0.1 mm to 0.3 mm and preferably between 0.1 mm to 0.2 mm excluding any chamfer or rounding of the neck at the distal end. At the proximal end of the neck adjacent the handle the sheath thickness t increases according to the taper angle and neck length.

[0056] The neck 34 defines a distal end extremity 38 where the stem emerges from the body, which corresponds to a distal end of the body 16. The distal end extremity 38 is arranged generally perpendicularly with respect to a longitudinal axis of the body 16 (which is coincident with the longitudinal axis 36 of the neck 34) as a distal end face. As is shown in Figures 5 and 8, the distal end face defines a shoulder 40, which appears annular or ring-like when viewed in transverse cross-section. The shoulder 40 is a portion of the end extremity 38 that is disposed about the elongate stem 20 where the elongate stem 20 projects from the end extremity 38. The shoulder 40 height h generally corresponds to the sheath thickness t, of between 0.01 mm and 0.5 mm, preferably a thickness of between 0.1 mm to 0.3 mm and preferably between approximately 0.1 mm and 0.2 mm.

[0057] As shown in Figure 5, the body 16 comprises a transition portion 42. The transition portion 42 is a portion of the body 16 that converges or tapers toward the neck 34. The transition portion 42 is frustoconical in overall form (see Figure 1) and provides a smooth transition between the portion of the body 16 that is generally circular in transverse cross-section and the neck 34. As shown in Figure 5 for example, a diameter of a proximal end 44 of the transition portion 42 is similar to a diameter of a major portion of the body 16, i.e., the portion of the body that is generally circular in transverse cross-section. Additionally, a diameter of a distal end 46of the transition portion 42 is similar to the diameter of the neck 34 depending on the degree of conical taper angle a. Advantageously, the reduced diameter of the neck 34 as compared to the diameter of the major portion of the body 16 allows for the neck to resiliently bend with respect to the remainder of the body 16.

[0058] As is shown in Figure 2, the neck 34 is configured to resiliently deflect or bend generally in the direction of bending of the elongate stem 20 under application of a lateral load indicated by arrow F. Advantageously, the bendable neck 34 of the body 16 therefore acts to distribute bending deformation along the stem including the root portion of the stem within the neck and thereby to allow for an increase of the radius of curvature, of the elongate stem 20 during bending, in comparison to a rigid neck 34 or end portion 18 which tends to concentrate loading and therefore bending deformation at the base of the stem, and thus reduce a bending stress concentration applied to the elongate stem 20 during use of the interdental brush 10. Accordingly the flexible stem may, in turn, reduce fatigue of the stem and increase the useful life of the elongate stem 20 and thus the interdental brush 10. That is to say, the bendable neck 34 is an advantageous improvement over certain prior interdental brushes that do not include a means to reduce a bending stress concentration applied to the elongate stem of the brush portion of the interdental brush during use. In these prior interdental brushes, the bending stress typically concentrates at a single position on the elongate stem, usually where the elongate stem projects from the handle. This concentration of the bending stress causes relatively greater localised deformation which may exceed the yield point of the stem so that it plastically deforms and may result in fatigue and / or work hardening of the stem material leading to relatively rapid formation of small cracks in the elongate stem at the aforementioned position. Ultimately, with repeated use of the interdental brush, the elongate stem fails and separates from the interdental brush at the aforementioned position relatively sooner as compared to the interdental brush 10 disclosed herein.

[0059] As noted previously, a load applied to the brush 14 and stem 20 may cause a deflection of the stem from its longitudinal axis 23, which in turn induces deflection of the surrounding flexible neck 34. The amount of deformation induced in the neck 34 is in part due to the flexibility of the neck 34 which is determined by its physical dimensions and material properties. For a given gauge / thickness of the stem wire, the material forming the neck and thickness t of the sheath surrounding the stem 20 are selected to provide sufficient induced deformation of the neck 34 in use. With reference to Figures 2 and 3, the neck 34 is configuredto deflect from the longitudinal neck axis 36 under a load applied to the brush and / or stem. Preferably the neck 34 is configured to deflect from the longitudinal neck axis 36 by an angle 0 of more than 8°, and preferably more than 20° when the stem at the stem tip is deflected to an angle c of 90° to the longitudinal stem axis 36, under application of a deflection force applied laterally to the stem at the tip of the stem indicated by arrow F. In one embodiment, the neck allows deformation of the stem to remain below the yield point of the neck material.

[0060] As shown in Figure 3, detail A, the angle c is measured between the unloaded longitudinal neck axis 36 and the deflected neck axis 36', or a line tangent thereto, taken at the distal end extremity 38 of the neck. The angle a is measured between the unloaded stem axis 23 which is typically coincident with the longitudinal stem axis 36, and the deflected stem axis 23', or a line tangent thereto, taken at the distal end extremity 38 of the stem.

[0061] Advantageously, whole handle 12 including the end portion 18 of the interdental brush 10 of the present disclosure is a one-piece or unitary construction. In particular, during manufacture of the interdental brush 10, the brush portion is first manufactured by twisting one or more length / s of wire to form the stem while capturing bristles of the brush therebetween. The bristled portion is disposed at one end of the stem. The root portion, absent of bristles extends to the other. The brush portion is then placed into a mold and the body 16 is overmolded about the root portion of the elongate stem 20 to thereby secure the elongate stem 20 (and thus the brush portion 14) to the handle 12. In other words, the brush portion is manufactured and the elongate stem 20 is secured to the handle 12 during overmolding of the body 16, and thus no separate adhesive or mechanical connection between the elongate stem 20 and the body 16 is required in order to secure the elongate stem 20 within the handle 12. As an alternative however, in some embodiments the handle is pre-molded and provided with an aperture extending longitudinally from the stem end, through the center of the stem along its axis and transition portion. The root portion of the stem of the premade brush portion is inserted into the aperture and then heat and / or pressure is applied to the body and / or neck and / or transition portion of the handle to secure the stem into the handle. In other embodiments the root portion of the stem of the premade brush portion is inserted into the aperture and then bonded with a cement or an adhesive to secure the stem into the handle. In still further embodiments, the root portion of the stem of the premade brush portion is inserted into the aperture and then whole or portions of the stem is heated (for instance by induction) to secure the stem into the handle.

[0062] A partial cutaway of the neck 34 is illustrated in Figures 8 and 9, which generally illustrates how the body 16 is overmolded about the elongate stem 20 such that a proximal end of the elongate stem 20 is embedded in the body 16. Advantageously, due to its one-piece or unitary construction, no assembly of separate components is required in order to manufacture the interdental brush 10 with a flexible tip of the same material as the handle 12 and body 10. Further advantageously, the body 16 of the interdental brush 10 comprises a single material, such as a thermoplastic polymer which may be polypropylene. In other embodiments the material may be polyethylene or any other semi-resilient polymer sufficiently rigid to act as a semi rigid handle and resilient enough to bend at the neck in use when the wire stem is bent approximately ninety degrees by finger force by the user. The body 16 has a length of approximately 50 mm.

[0063] In some embodiments, in accordance with another aspect of the invention, the stem includes a first portion and a second portion and wherein a physical property of the material of the first portion differs from the same physical property of the material of the second portion. The handle may not necessarily include a flexible end portion. In some embodiments, a portion of the material forming the stem 20 is treated to alter one or more physical properties of the stem in the treated portion. The physical property of the material may be selected from the group comprising: flexural modulus; fatigue strength; fatigue resistance; yield strength, stiffness, modulus of elasticity; ductility.

[0064] In another embodiment, where the stem is made from a metal such as stainless steel wire or metal alloy wire, at least a length of the metal forming the stem 20 is annealed, heat and / or chemically treated or irradiated to alter the physical properties of the metal in the treated portion to increase its fatigue strength.

[0065] In preferred embodiments at least a portion of the root portion 26 of the stem is subjected to localised heating of the wire before cooling, and the stem is subsequently overmolded into the handle. Advantageously, heat treating or annealing the wire over a portion of the stem provides the stem with different physical properties along its length. Preferably the heat-treated portion is provided with increased toughness and fatigue strength than the remainder of the stem making it more resistant to cold working failure. Comparatively the portions of the stem that are not treated remain relatively rigid to resist deformation in use. The process further advantageously allows a higher tensile strength wire to be used in forming the stem than which would betypically used, which provides a stiffer bristled portion to resist deformation, and the root portion may selectively be annealed or treated to enhance toughness and fatigue strength.

[0066] Treatment may be applied to any one or more whole or part sections of the stem. For instance, as can be seen with inspection of Figure 9, in this embodiment a portion of the stem is exposed between the bristled portion and the handle as the ‘shut-off portion 28, providing some separation between the bristled portion 24 and the end portion of the handle. Furthermore, as shown on Figure 9, the root portion 26 comprises a first zone 26a corresponding to the root portion 26 of the stem 20 passing through the neck 34, and a second zone 26b corresponding to the root portion 26 of the stem 20 extending through the transition portion 42 from the neck 34 to the proximal or handle end extremity of the stem 20 and embedded in the body of the handle. In this embodiment the bristled portion 24, root portion 26 and shut-off portion 28 may range between 4-20mm mm, 15-25 mm and 1-3 mm in length respectively.

[0067] One or more of the first zone 26a or the second zone 26b of the root portion 26, and or the shut-off portion 28 of the wire of the stem may be treated. Treatment of the stem however, may be preferably confined predominantly to the first zone 26a which corresponds to the flexible neck 34 of the handle. Furthermore, advantageously, treating the wire within the portions of the stem 20 that will be embedded or overmolded in the handle, will conceal those treated portions of the stem from view. For instance, the wire may include a coating or a plastic coating / sheath which may be marked or damaged during treatment. Embedding this portion of the wire not only improves the aesthetics of the brush by hiding the marked portion but also may act to replace the protective coating damaged or destroyed during the treatment process. While the stem wire will typically be heat treated after manufacture of the brush portion (wherein the wire strands 30 are wound or twisted about each other to form the wound wire stem 20 and brush) and prior to joining the stem and the handle, in some embodiments, the wire may be selectively treated prior to manufacture of the brush portion. In embodiments where exposed portions of the stem such as the shut off portion 28, are treated, those portion may be recoated to conceal any damage caused by the treatment process.

[0068] In some embodiments, as noted above, prior to the step of overmolding, and following manufacture of the brush portion, the stem of the brush portion is annealed to increase its toughness and flexibility and reduce stiffness and brittleness.

[0069] In other cases, where the root portion of the stem of the premade brush portion is inserted into the aperture and then whole or portions of the stem is heated to secure the stem into the handle, the step of heat treating the stem and heating to bond the stem to the handle are carried out simultaneously in a single step.

[0070] The body 16 also includes a plurality of longitudinally extending grooves 48 (Figure 1) in an outer surface thereof, which grooves 48 define respective ridges 50 at outer edges of the grooves 48. The grooves 48 and ridges 50 extend generally circumferentially about the body 16 and are configured to aid a user in securely gripping the handle 12 and to aid use with a separate extension handle or attachment.

[0071] While the embodiment of the invention shown in the figures includes a brush portion extending from one end of the elongate handle, in other embodiments the handle includes a brush portion extending from each end of the handle. A cap is provided at each end to selectively cover and uncover the respective brush in use. The cap engages with the handle by friction fit so that it may provide an extension of the handle. Furthermore, the caps may be nestable so that a cap from one end of the brush may be removed to expose the respective brush portion for use, and located on the other end to stack on the cap positioned covering the opposite end brush.

[0072] Advantageously, the present disclosure provides a one-piece or unitary interdental brush 10 with a resiliently bendable neck 20 that can also function as a rigid handle and is configured to reduce a bending stress applied to the elongate stem 20 of the brush portion 14 during use, and thus prolong the useful life of the interdental brush 10 as compared interdental brushes of the prior art.interdental brush 10 handle 12 brush portion 14 elongate body 16 end portion 18 elongate stem 20 bristles 22 bristled portion at a distal end 24 root portion 26 shut off portion, 28 pair of wire strands 30 circular discs 32 neck 34 longitudinal axis 36 of the neck 34 neck 34 has a maximum diameter, D length L, conical angle a distal end face 38 shoulder 40 height h, transition portion 42 proximal end 44 (of the transition portion) distal end 46 of the transition portion 42 longitudinally extending grooves 48 respective ridges 50

Claims

CLAIMS1. A interdental brush, comprising: a handle, said handle comprising a body and an end portion; a brush portion, said brush portion comprising an elongate stem having a distal bristled portion including a plurality of bristles extending from the elongate stem and a proximal root portion to be embedded in the handle to secure the brush portion to the handle; wherein the root portion of the elongate stem is embedded in the end portion such that the brush portion projects from the end portion of the handle.

2. The interdental brush according to claim 1 wherein the end portion is configured to distribute bending deformation along the stem including the root portion of the stem within the neck during use of the interdental brush.

3. The interdental brush according to claim 1 or 2 wherein the end portion is resiliently flexible.

4. The interdental brush according to any one of the preceding claims wherein the body is overmolded about the elongate stem such that the elongate stem extends through the end portion.

5. The interdental brush according to any one of the preceding claims wherein the body and the end portion are formed of a uniform composition or material.

6. The interdental brush according to any one of the preceding claims wherein the body and neck are formed of a material having a flexural modulus of in the range of 300 MPa to 2700MPa and preferably in the range of 700MPa to 1300MPa more preferably around 900 MPa.

7. The interdental brush according to any one of the preceding claims wherein the body and neck are formed of a thermoplastic polymer preferably a polypropylene or polyethylene.

8. The interdental brush according to any one of the preceding claims wherein the body comprises a transition portion that tapers toward a neck forming the end portion.

9. The interdental brush according to claim 8 wherein the elongate stem extends through the neck such that the neck provides a covering or sheath around the stem having a sheath thickness of between 0.01 mm and 0.5 mm, preferably a thickness of between 0.1 mm to 0.3 mm and more preferably a thickness of between 0.1 mm to 0.2 mm.

10. The interdental brush according to claim 8 or 9 wherein the neck is of substantially constant cross sectional diameter.

11. The interdental brush according to claim 8 or 9 wherein the elongate tapers toward the distal end adjacent the brush by a conical taper angle a between about 1° and about 8, preferably, by a conical taper angle a between about 1° and about 5°; more preferably, by a conical taper angle a of about 2°.

12. The interdental brush according to claim 8 or 9 wherein the neck is configured to deflect by an angle 0 of around 8° or more, and preferably around 20° or more when the stem is deflected to an angle c of 90° under application of a deflection force applied laterally to the stem.

13. The interdental brush according to claim 12 wherein the angle 0 is measured between the unloaded longitudinal neck axis and the deflected neck axis, or a line tangent thereto, at a distal end extremity of the neck.

14. The interdental brush according to claim 12 wherein the angle c is measured between the unloaded longitudinal stem axis and the deflected stem axis, or a line tangent thereto, at a distal end extremity of the stem.

15. The interdental brush according to any one of the preceding claims wherein the stem is formed of a uniform composition.

16. The interdental brush according to any one of the preceding claims wherein at least a portion of a length of the stem is treated to modify a physical property of said length.

17. The interdental brush according to any one of the preceding claims wherein the stem includes a first portion and a second portion and wherein a physical property of the material of the first portion differs from the same physical property of the material of the second portion.

18. The interdental brush according to claim 17 wherein, the physical property of the material is one or more physical property selected from the group comprising: flexural modulus; fatigue strength; fatigue resistance; yield strength, stiffness, modulus of elasticity; ductility.

19. The interdental brush according to any one of the preceding claims wherein the stem includes a metal.

20. The interdental brush according to any one of the preceding claims wherein the stem is formed of a metal wire.

21. The interdental brush according to claim 20 wherein at least a portion of the metal of the stem is heat treated to enhance the fatigue strength of the metal.

22. The interdental brush according to claim 20 wherein at least a portion of the metal of the stem is chemically treated or irradiated to enhance the fatigue strength of the metal.

23. The interdental brush according to any one of claims claim 20 to 22 wherein the metal wire has a tensile strength in the range of 600MPa to 2000MPa and preferably 750MPa to HOOMPa.

24. A method of manufacturing an interdental brush in accordance with any one of the preceding claims, said method comprising the steps of: forming the brush portion; forming the handle, wherein the root portion of the elongate stem is embedded in the end portion such that the brush portion projects from the end portion.

25. The method of manufacturing an interdental brush according to claim 24, wherein the body is overmolded about the elongate stem such that the elongate stem extends through the end portion.

26. The method of manufacturing an interdental brush according to any one of claims 24 or 25, including the step of modifying at least a portion of a length of the stem to alter a physical property of said length.

27. The method of manufacturing an interdental brush according to any one of claims 24 to 26, including the step of heat treating at least a portion of the metal of the stem to enhance the fatigue strength of the metal.

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