US20120272469A1

US20120272469A1 - Toothbrush and manufacturing method thereof

Info

Publication number: US20120272469A1
Application number: US13/545,660
Authority: US
Inventors: Young-Jun Kwon; Sung-Wook Kwon
Original assignee: BEST HWASUNG CO Ltd
Current assignee: BEST HWASUNG CO Ltd
Priority date: 2002-12-03
Filing date: 2012-07-10
Publication date: 2012-11-01

Abstract

A toothbrush includes a head and a plurality of bristles. Each bristle includes a first end exposed outside the head of the toothbrush, and a second, opposite end being placed in the head of the toothbrush. The second ends of the bristles are fused together, in bundles, to be thermally attached directly to the head of the toothbrush and/or to define a continuous layer in which at least some of the bundles are also fused together.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. Ser. No. 11/586,631, filed on Oct. 26, 2006 which is a divisional of U.S. Ser. No. 10/627,913, filed on Jul. 28, 2003 which, in turn, is based on and claims priority from Korean Patent Application No. 2002-76349 filed on Dec. 3, 2002. The above listed applications, in their entirety, are incorporated herein by reference.

BACKGROUND

1. Technical Field
The present disclosure relates generally to a toothbrush and a manufacturing method thereof.
2. Description of the Related Art
Since the introduction of a toothbrush tufted with tapered bristles for effective plaque removal and prevention of damage to gums during teeth brushing, its verified effectiveness has recently made this toothbrush popular.
For fabrication of such a traditional toothbrush, 28 to 33 mm long bristles, which are needle-shaped on one end t and non-needle-shaped on the other end n, are folded over such that the needle-shaped portion is longer than the non-needle-shaped portion, as illustrated in FIGS. 1A and 1B. The folded portions are picked up by means of a cut wire and fixedly inserted into fixing holes in the head of the toothbrush. The toothbrush manufacturing method is disclosed in Japanese Patent Open-Laid No. Sho 61-10495.
As illustrated in FIG. 2, another traditional toothbrush is made by folding needle-shaped bristles, which are 28 to 33 mm long and tapered 4 to 8 mm on both ends, in two equal halves and planting them in the above-described manner. This toothbrush manufacturing technique is disclosed in Japanese Patent Open-Laid No. Hei 5-15834.
In Korea Patent No. 311360, the present inventor disclosed a toothbrush tufted with ordinary bristles tapered on both ends and at least one 1 to 10 mm longer bristle 62 of the same shape.
The above techniques, though they have their own benefits and drawbacks, commonly boast excellent plaque removal and improved health of gums.
The following shortcomings are observed by the present inventor(s) in terms of one or more of complex manufacturing, high inferior goods rate, and thus high production cost, for the following reasons.
(1) In order to shape ordinary polyester bristles into needles, the tips of the bristles are treated with a chemical such as caustic soda or sulphuric acid. During this process, the total length and tapered length of the bristles are difficult to control, thereby resulting in many inferior bristles. (2) In the case of a today's popular needle-shaped toothbrush tufted with bristles tapered on both ends, both tips of the bristles are treated in the above-described manner, for needle shaping. Even if one tip of a bristle is successfully tapered, the failure of the other tip leads to the whole failure of the bristle. (3) There are no appropriate applications for utilizing bristles having wrong lengths.
Besides, the traditional toothbrush bristles are planted in simple patterns and not tightly fixed, as illustrated in FIG. 4. As a result, the bristles often fall out of the brushes. The cause is identified that the bristles are folded by half, picked up with a wire, and pushed into fixing holes 10 by inserting the wire itself.

SUMMARY

BRIEF DESCRIPTION OF THE DRAWINGS

Several exemplary embodiments of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1A is a side view of a folded 23 to 33 mm long bristle which is needle-shaped on one end and non-needle-shaped on the other end, before planting;

FIG. 1B is a partial enlarged view of bristles as illustrated in FIG. 1A planted in a toothbrush head;

FIG. 2 is a side view of a folded 28 to 33 mm long bristle which is tapered 4 to 8 mm on both ends like needles, before planting;

FIG. 3 is a schematic view illustrating a toothbrush tufted with ordinary both-end tapered bristles and 1 to 10 mm longer ones;

FIG. 4 is a plan view of a traditional bristle planting pattern for a toothbrush;

FIG. 5 is a side view of a needle-shaped bristle tapered only on one end according to one or more embodiments of the present invention;

FIG. 6 is a perspective view of needle-shaped bristles as illustrated in FIG. 5 vertically loaded in a cylindrical container;

FIG. 7 is a side sectional view of a primary bristle holder for use in manufacturing a toothbrush according to one or more embodiments of the present invention;

FIG. 8 is a side sectional view of a secondary bristle holder for use in manufacturing the toothbrush according to one or more embodiments of the present invention;

FIG. 9 is a side sectional view of a head insert for use in manufacturing the toothbrush according to one or more embodiments of the present invention;

FIG. 10 is a side sectional view of a pusher having inserting poles matching through holes formed in the primary bristle holder;

FIG. 11 is a view illustrating transfer of the needle-shaped bristles from the primary bristle holder to the secondary bristle holder and the head insert;

FIG. 12 is a view illustrating thermal fusion of the needle-shaped bristles together and/or to the head insert;

FIG. 13 is a perspective view of a toothbrush handle before the head insert is attached;

FIG. 14 is a perspective view of the toothbrush tufted with the bristles tapered only one end;

FIG. 15 is a view illustrating attachment of the head insert to the toothbrush handle by injection molding;

FIG. 16 is a view illustrating partial thermal fusion of the bristles;

FIG. 17A is a schematic top view of bristles thermally attached to the head insert in accordance with one or more embodiments, and FIG. 17B is a cross-sectional view taken along line 17-17 in FIG. 17A;

FIG. 18A is a schematic top view of bristles thermally attached to the head insert in accordance with one or more embodiments, and FIG. 18B is a cross-sectional view taken along line 18-18 in FIG. 18A; and

FIG. 19 is a schematic top view showing various bundle configurations in accordance with an exemplary embodiment.

DETAILED DESCRIPTION

Several exemplary embodiments of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail for the sake of simplicity.
As used herein, two originally separate elements are “thermally fused” or “thermally fused together” or “fused together” or “fused” when they are joined by melted and then solidified materials (including but not limited to plastics, especially polyester) of both elements. The term “fusion” or “thermal fusion” or “fused portion” means a structure resulted from several elements being fused together.
As used herein, two originally separate elements are “thermally attached” when a melted material (including but not limited to plastics, especially polyester) of at least one element adhered to the other element and then solidified. The term “thermal attachment” means a structure resulted from several elements being thermally attached with each other. Accordingly, the term “thermally attached” and “thermal attachment” cover “thermally fused” and “fused portion” respectively.
A toothbrush according to one or more embodiments of the present invention is comprised of one-end tapered bristles formed of polyester resin to be 13 to 18 mm in total length and 4 to 8 mm in tapered length. To manufacture the toothbrush, the non-tapered portions of the bristles are pushed down into through holes arranged in a planting pattern in a bristle holder. Portions of the bristles protruding beyond the bottom of the bristle holder are thermally fused to thereby fix, at least temporarily, the bristles to the bristle holder. The bristle holder is then attached to the head of the toothbrush.
FIG. 5 is a side view of a single needle-shaped bristle 60 which is 13 to 18 mm in length and 4 to 8 mm in tapered length according to one or more embodiments of the present invention. As compared to a traditional both-end tapered bristle, the bristle 60 is tapered only on one end and shorter by half with the same tapered length. The one-end tapering diminishes a bristle failure rate involved with tapering.
Since the bristle 60 is planted 5 to 6 mm deep in a toothbrush head, it is then 7 to 13 mm high from the surface of the toothbrush head.
The tapered tip of the bristle 60 is 0.01 to 0.08 mm thick. The tapered tip thickness is preferably 0.01 to 0.03 mm to allow the bristles to reach deep between teeth and into gum pockets, and 0.03 to 0.08 mm for thorough cleansing. Both features can be obtained by planting the two types of bristles in combination, or grinding bristles by means of a mesh paper (i.e. sandpaper) after planting, which will be described later.
In some embodiments, it is preferable to form the bristles of polyester resin, specifically PET (Polyethylene Terephthalate) or PBT (Polybuthylene Terephthalate) resin. Other materials, such as Nylon, acryl, and PP (Polypropylene) resin, are not excluded and may be used in other embodiments (especially where non-tapered bristles are used), although such materials are inferior in terms of water resistance, durability, and strength, and bristles formed of such a material may be entangled when they are immersed in a strong acid or alkaline solution, for tapering, resulting in difficult processing.
FIG. 6 is a view illustrating the bristles 60 loaded vertically in a cylindrical plastic container 61. The loaded bristles 60 are held in a primary bristle holder 20 as illustrated in FIG. 7, transferred to a secondary bristle holder 30 as illustrated in FIG. 8, and then transferred to a head insert 50 as illustrated in FIG. 9. The primary bristle holder 20, the secondary bristle holder 30, and the head insert 50 include through holes 21 of the same shape. The primary and secondary bristle holders 20 and 30 are formed of a metal, whereas the head insert 50 is preferably formed of plastic though a metal can be used.
Since the primary and secondary bristle holders 20 and 30 function to transfer the bristles 60 to the head insert 50, they are of a metal due to its excellent durability. The head insert 50 is formed of plastic because it is attached to a toothbrush body 70, with the bristles 60 planted therein.
The bristles 60 are held in the primary bristle holder 20 by pushing the bristles 60 into the primary bristle holder 20 with a pusher 40 having inserting poles 41 matching the through holes 21 of the primary bristle holder 20, as illustrated in FIG. 10.
Referring to FIG. 11, the bristles 60 are then transferred from the primary bristle holder 20 to the head insert 50 through the secondary bristle holder 30 by pushing the bristles 60 held in the primary bristle holder 20 to the secondary bristle holder 30 and then the head insert 50 with the pusher 40, while matching the through holes 21, in alignment, of the primary and secondary bristle holders 20 and 30 and the head insert 50. Here, the non-tapered portions n of the bristles 60 are upward.
Referring to FIG. 12, the bristles 60 protruding from the head insert 50 are thermally fused together into one or more fused portions 135, each of which is directly attached to the head insert 50. Each fused portion 135 includes protruding portions of bristles 60 which have been melted and then solidified into a single body. While being melted, the protruding portions of the bristles 60 flow or deform around the respective through holes 21. As a result, the subsequently formed fused portion 135 is larger than the dimension of the respective through hole 21, thereby preventing the bundle of the bristles 60 from falling off the head insert 50 during subsequent processing.
In some embodiments, a portion of the head insert 50 is also thermally fused into one or more fused portions 135 of the bristles 60. That is, while the bristles 60 protruding from the head insert 50 are being melted, the adjacent portion of the head insert 50 is also melted, at least partially. Upon solidification, the at least partially melted adjacent portion of the head insert 50 and the melted portions of the bristles 60 together form a common fused portion.
In some embodiments, one or more fused portions 135 bristles 60 and an adjacent portion of the head insert 50 are thermally attached to each other. That is, while the bristles 60 protruding from the head insert 50 are being melted, the adjacent portion of the head insert 50 is not melted. Upon solidification, the melted portions of the bristles 60 together form a fused portion 135 which, while still in the melted or soften state, adheres to the adjacent portion of the head insert 50 to form a thermal attachment with the head insert 50.
Whether or not the bristles 60 and the head insert 50 are fused together or are thermally attached depend on the respective materials of the bristles 60 and head insert 50 as well as on the conditions, such as temperature, duration, pressure, etc., in the process disclosed above with respect to FIG. 12. Subsequent processing and/or packaging and/or use of the tooth brush may subject the common fused portion or the thermal attachment between the bristles 60 and the head insert 50 to an appropriate force that separates the head insert 50 from the fused portion(s) 135. However, the larger size of the fused portion(s) 135 compared to the respective through holes 21 prevents the bundle(s) of the bristles 60 from falling off.
During the process disclosed above, the length of the bristles 60 is controllable to some extent. That is, short bristles 60 are thermally fused while they are protruded to a short length, for example, 1 mm or less, and long bristles 60, while they are protruded to a long length, for example, about 3 mm. In the case of very long bristles, they are thermally fused in the above manner and then their tips are cut, followed by grinding with a mesh paper. Therefore, an available length range for the one-end tapered bristles 60 is widened.
When the bristles differ in length after planting, the tips of longer ones are cut and ground by a mesh paper. Thus, the length and tip thickness of the bristles are controlled. In this case, bristles having a tip thickness of 0.01 to 0.03 mm coexist with ones having a tip thickness of 0.03 to 0.08 mm. As a result, the bristles reach deeper between teeth and into gum pockets and clean the surfaces of the teeth thoroughly.
To reach deeper into the gum pockets, the bristles can be planted such that they differ in length by 1 to 10 mm. That is, the planting of long bristles and short bristles with a 1 to 10 mm length difference makes the longer ones reach further between teeth or into gum pockets.
The head insert 50 having the bristles 60 fixed thereto is attached to the head of the toothbrush body 70 by one or more of adhesive, mechanical engagement, ultrasonic bonding or high frequency bonding.
Considering product yield, the ultrasonic or high frequency boding is more preferable. In this case, a head insert opening 51 is preferably formed in the head of the toothbrush body 70, so that the head insert 50 can be mounted in the head insert opening 51, as illustrated in FIG. 13. The thus-completed toothbrush is illustrated in FIG. 14.
An alternative way of fixing the head insert 50 with the bristles 60 to the toothbrush body 70 is, as illustrated in FIG. 15, to combine a lower metal mold 90 to an upper metal mold 80 with the bottom of the head insert 50 fixed thereto, injecting resin into the lower metal mold 90 through an inlet 91, so that the head and handle of the toothbrush are integrally formed and at the same time, the head insert 50 is tightly combined with the toothbrush head. This fixing method advantageously enables manufacture of various types of toothbrushes using metal molds for the toothbrush head and handle of different shapes, increases process efficiency, prevents introduction of foreign materials due to formation of no junction gaps, and makes it possible to reduce the thickness of the toothbrush head, thus allowing easy thorough teeth brushing.
Another way of planting the bristles 60 in a toothbrush body is that the non-tapered portions of the bristles 60 are inserted into through holes in the lower metal mold 90, protruding 2 to 5 mm from the metal mold 90, these protrusions are thermally fused, an upper metal mold (not shown) is combined with the lower metal mold 90, and then resin is injected so that the bristles 60 are attached directly to the toothbrush body, as illustrated in FIG. 16. This method also offers the benefits that the toothbrush head is integrated into the toothbrush handle, product yield is increased, no junction gaps are produced to thereby prevent introduction of foreign materials, and reduces the thickness of the toothbrush head.
In some embodiments, the bristles 60 protruding from the head insert 50 are thermally fused into fused portions 135 as exemplarily illustrated in FIGS. 12, 17A, 17B and also denoted in FIGS. 17A, 17B. Like the embodiment exemplarily illustrated in FIG. 12, the fused portions 135 have a larger diameter than the holes in the head insert 50, thereby preventing the bundles of bristles 60 from falling off the head insert during subsequent processing. Like the embodiment exemplarily illustrated in FIG. 12, the fused portions 135 may or may not be thermally attached to or fused with the head insert 50, depending on the material of the head insert 50 and/or the fusion temperature of the bristles 60.
As exemplarily illustrated in FIGS. 17A, 17B, several fused portions 135 are separated or spaced from each other, while other fused portions 135 are further fused together into a continuous layer 136 that extend across, i.e., covers, multiple holes of the head insert 50. The bundles joined by the continuous layer 136 are more firmly attached, mechanically and/or thermally, to the head insert than the other, separated bundles. Thus, the cleaning effect(s) of the bundles joined by the continuous layer 136 may be different from the cleaning effect(s) of the other, separated bundles.
The formation of the continuous layer 136 depends on various factors, including but not limited to, the fusion conditions, the length and material property of the protruding portions of the bristles 60, the density (i.e., number of holes per unit area) of the through holes in the head insert 50 etc. By varying one or more of the disclosed and/or any other factors, the number, position, size, shape, thickness etc. of the continuous layer 136 can be varied, resulting in various cleaning effects of the toothbrush.
FIGS. 18A and 18B show an embodiment in which all bundles are fused together into a continuous layer 136 that extend across, i.e., covers, all holes of the head insert 50. In the particularly illustrated embodiment, the continuous layer 136 covers the entire bottom of the head insert 50 and further engages the side walls of the head insert 50, to more firmly fix the bundles to the head insert 50.
In some embodiments, the bristles in the fused portions 135 and continuous layer 136 no longer retain their original shapes and cannot be separated from each other. In some embodiments, the thermal attachment of the fused portions 135 and continuous layer 136 with the head insert 50 may be broken, resulting in potential slight movements of the bundles relative to the head. Such potential slight movements, if indeed exist, are greatly limited by the manner the bundles are joined together by the continuous layer 136 (especially in the embodiment disclosed with respect to FIGS. 18A, 18B), and/or by a cover (not shown) that is fit to the head insert 50 (from above in FIGS. 12, 17B, 18B) to cover the fused portions 135 and continuous layer 136.
It should be noted that since thermal attachment or fusion is used for fixing the bristles 60 to the head insert 50, the bundles of the bristles 60 is easily configurable to be of any shape and/or size and/or position and/or bristle density (bundle strength), thereby permitting various designs of such bundles to be made with great flexibility in size, shape, position, bristle density, not to mention length and taperness as disclosed above. The result is that cleaning effects of the toothbrush can be enhanced and/or customized as desired. An example of possible bundle configurations is given in FIG. 19 which is a top view of a tooth brush in accordance with an exemplary embodiment. In FIG. 19, bundles 191-196 of various sizes, shapes, positions are included in a tooth brush. Although shapes such as rectangle, oval, triangle, trapezoid etc. are depicted any other shapes are within the scope of the instant application. Further, bundles of the same or similar shapes are positionable in any desired directions as exemplarily illustrated at 191 and 192, or have any desired sizes as exemplarily illustrated at 193 and 194. As noted herein, color, length, taperness, material, density (number of bristles per unit area) of bristles 60 are variable from bundle to bundle and/or within the bundle(s) itself/themselves.
The above disclosed “free design” feature is hardly obtainable, if at all, with the known technique of fixing bristles 60 via folding and clipping etc. The reason is that a folded bundle generally has a symmetrical configuration about the folding line, and is difficult to fit in holes of certain sizes and shapes (such as 195, 196 in FIG. 19) which, in turn, may cause the bundle to be loose or fall off easily. A tooth brush with such loosely fixed bristles might cause discomfort to the user or can even hurt the user's gum and tissues in use.
In contrast, in embodiments of the instant application, simply by varying sizes, shapes, positions of the through holes 21, bundles of corresponding configurations are easily obtainable with numerous advantages discussed herein, e.g., enhanced plaque removal effects and/or aesthetic appearance (when bundles of multiple colors and/or shapes are included).
The structures disclosed above with respect to FIGS. 17A-19 are applicable not only to the method of manufacturing toothbrushes exemplarily disclosed with respect to FIG. 12, but also to all other manufacturing methods disclosed herein, especially with respect to FIGS. 15-16.
As described above, the toothbrush according to one or more embodiments of the present invention is tufted with needle-shaped bristles tapered only on one end, as compared to the traditional toothbrush having both-end tapered bristles. Therefore, an inferior goods rate is remarkably dropped and thus product cost can be reduced by 30% or more.
However, it is within the scope of the present invention to provide toothbrushes that, according to some other embodiments, are tufted with bristles that are not tapered at either end. Toothbrushes according to further embodiments of the present invention are tufted with a mix of one-end-tapered bristles and non-tapered bristles.
Furthermore, a bristle planting pattern and the number of the needle-shaped bristles can be freely controlled, thereby enabling the bristles to clean away hard-to-reach plague. The use of thermal fusion instead of a cut wire leads to tighter fixing of the bristles. Even needle-shaped bristles which are failed in length control can be utilized for fabrication of the toothbrush.
Thus, one or more embodiments provide a toothbrush tufted with needle-shaped and/or non-tapered bristles, which is manufactured in a simplified process at a diminished failure rate.
One or more embodiments provide a method of utilizing bristles having wrong lengths for manufacture of a toothbrush.
One or more embodiments provide a method of fixing bristles more tightly in a toothbrush.
One or more embodiments provide a method of freely designing a bristle planting pattern and adjusting the number of bristles for a toothbrush.
While exemplary embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A toothbrush, comprising:

a head; and

a plurality of bristles, each of said bristles comprising a tapered first end exposed outside the head of the toothbrush, and a second, opposite end being placed in the head of the toothbrush,

wherein the second ends of the bristles are fused together, in bundles, to be thermally attached directly to the head of the toothbrush.

2. The toothbrush of claim 1, wherein

the head of the toothbrush further comprises a head insert which comprises

opposite first and second surfaces, and

a plurality of through holes extending from the first surface to the second surface of said head insert; and

each of said bundles comprises several said bristles received in one of the through holes, with the respective second ends of the bristles protruding beyond the second surface of the head insert and defining a fused portion which is larger than a diameter of the respective through hole and which is thermally attached to the head insert.

3. The toothbrush of claim 2, wherein

several of said bundles are fused together at the respective fused portions to define a continuous layer that extends across the respective through holes in which said several bundles are received.

4. The toothbrush of claim 3, wherein

all of said bundles are fused together at the respective fused portions to define a continuous layer that extends across all said through holes.

5. The toothbrush of claim 2, further comprising a handle having a head insert opening in which said head insert is mounted.

6. The toothbrush of claim 1, wherein, said bristles are polyester resin bristles.

7. The toothbrush of claim 1, wherein

each said bristle is tapered only on said first end thereof and further comprises a first non-tapered portion positioned between the tapered first end and the head of the toothbrush; and

in each said bristle:

the tapered first end has a length of from 4 mm to 8 mm and a tip thickness of 0.01 mm to 0.08 mm;

the first non-tapered portion has a thickness of 0.1 mm to 0.2 mm along a length thereof; and

a total length of the first non-tapered portion and the tapered first end is from 7 mm to 13 mm.

8. The toothbrush of claim 7, wherein

said bristles comprise first bristles and second bristles;

in each of said first bristles, the tip thickness of the tapered first end is 0.01 to 0.03 mm; and

in each of said second bristles, the tip thickness of the tapered first end is 0.03 to 0.08 mm.

9. The toothbrush of claim 7, wherein, in each of at least some of said bristles, the tip thickness of the tapered first end is 0.01 to 0.03 mm.

10. The toothbrush of claim 7, wherein, in each of at least some of said bristles, the tip thickness of the tapered first end is 0.03 to 0.08 mm.

11. The toothbrush of claim 7, wherein the bristles differ in length by 1 to 10 mm.

12. The toothbrush of claim 1, wherein

each said bristle is tapered only on said first end thereof, and the tapered first end defines the entire length of the bristle that is exposed outside the head of the toothbrush; and

in each said bristle:

the tapered first end has a length of 7 mm to 8 mm and a tip thickness of 0.01 mm to 0.08 mm.

13. The toothbrush of claim 2, further comprising:

a toothbrush body;

wherein the fused portions of the bundles of the bristles and the head insert are molded together with the toothbrush body.

14. The toothbrush of claim 1, further comprising:

a toothbrush body having said head;

wherein the fused second ends of the bristles are directly molded together with the head of the toothbrush body.

15. A tooth brush made by a method comprising the steps of:

inserting a plurality of bristles into each of a plurality of through holes defined between an upper surface and a lower surface of a head insert, said lower surface being near to a bottom of the head insert, each of said bristles defining a non-tapered portion at a first end and a tapered portion at a second end opposite to the first end thereof, said non-tapered portion being received into the through hole; and

maintaining the tapered portions of the bristles outside and away from the upper surface of the head insert and the non-tapered portion of the bristles to protrude from the lower surface of the head insert;

thermally fusing the non-tapered portion of the bristles protruding from the lower surface of the head insert, thereby fixing the bristles to the head insert;

attaching the bottom of the head insert to an upper metal mold; combining the upper metal mold with a lower metal mold; and

injecting resin into the lower metal mold through an inlet, thereby attaching the head insert to a head of the toothbrush.

16. A tooth brush made by a method comprising the steps of:

inserting a plurality of bristles into each of a plurality of through holes defined between a top part and a bottom part of a lower metal mold, each of said bristles defining a non-tapered portion at a first end and a tapered portion at a second end opposite to the first end, said non-tapered portion being received into the through hole to protrude 2 to 5 mm from the bottom part of the lower metal mold; and

maintaining the tapered portion of the bristles outside and away from the top part of the lower metal mold; thermally fusing the protruded non-tapered portion of the bristles;

combining an upper metal mold with the lower metal mold; and injecting resin into the upper and lower metal molds, thereby fixing the bristles directly to a head of the toothbrush.

17. A toothbrush, comprising:

a head; and

wherein

the head of the toothbrush further comprises a head insert which comprises

opposite first and second surfaces, and

a plurality of through holes extending from the first surface to the second surface of said head insert;

several said bristles are received in each of the through holes to form a bundles of the bristles, with the respective second ends of the bristles protruding beyond the second surface of the head insert and being fused together into a fused portion which is larger than a diameter of the respective through hole; and

at least some of said bundles are also fused together at the respective fused portions to define a continuous layer that extends across the respective through holes in which said at least some bundles are received.

18. The toothbrush of claim 17, wherein

19. The toothbrush of claim 17, wherein

the fused portions of at least some of said bundles are thermally attached to the head insert.

20. The toothbrush of claim 17, wherein

each said bristle is tapered only on said first end thereof.

21. The toothbrush of claim 17, wherein

in each said bristle:

22. The toothbrush of claim 1, wherein

said bundles have different shapes selected from the group consisting of rectangle, triangle, circle, oval, and trapezoid.