AU2008250913B2 - Toothbrush bristle with a tapering part and toothbrush with such bristles - Google Patents

Description

-1 Toothbrush bristle with a tapered part and toothbrush with such bristles Technical Field 5 Embodiments generally concern a toothbrush bristle with a tapered part and a toothbrush containing such bristles. Background 10 Customary bristles suitable for toothbrushes exhibited a cylindrical cross section. Since such bristles had an insufficient cleaning performance in the interdental space and tended to injure the gingiva, it was begun in some instances in the nineties of the last 15 century to provide the bristles with a pointed end (see e.g. EP-A-0 596 633). By virtue of the reduced diameter at the pointed end the cleaning performance in the interdental space improved; simultaneously the bristle became more flexible thereby, which lowered the risk of 20 injury. On the other hand the cleaning performance on the tooth surfaces deteriorated. In Korean patent KR 261658 (corresponds to US-A 6090488) a toothbrush bristle with a tapered end was 25 described, whereby the bristle had at the end of the tapering part a diameter of 0.04 to 0.08 mm. The tapered part of this bristle was thus not "pointed" anymore in the aforementioned sense. In the later EP-A-1 234 525 of the same inventor, however, a bristle with a tapered part is 30 described in which the diameter at the end of the tapered part is now only 0.02 mm or less (this bristle therefore again resembles more the pointed bristles about according to EP-A-0 596 633). As the justification for having re lowered the diameter at the end of the bristle the 35 inventor states that the removal of calculus from -2 periodontal pockets is difficult with the bristles of KR 261658. Any discussion of documents, acts, materials, 5 devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed 10 before the priority date of each claim of this application. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be 15 understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 20 Summary Embodiments generally aim to provide an improved bristle with a tapered part. Some embodiments relate to a bristle for a 25 toothbrush, comprising: a) a cylindrical part with a maximum, constant cylinder diameter Dzy 1 ; b) adjacent to the cylindrical part a first tapered part with a bristle end and an end face delimiting the 30 bristle end, whereby the first tapered part tapers towards the bristle end; and c) an imaginary central axis which runs through the cylindrical part and the first tapered part and which pierces the end face at a piercing point; whereby the 35 first tapered part has a length L of 10 mm or less and at -3 least 3 mm, as measured on the central axis starting from the piercing point; wherein the first tapered part has a diameter D of 95 to 140 pm, as measured on the central axis starting from 5 the piercing point at a distance X being equal to the cylinder diameter Dzyi. It was surprisingly found that the bristles according to described embodiments have a higher service life than 10 the prior art pointed bristles: The tapered ends do, according to the finding of the applicant, bend over under the pressing force occurring during tooth brushing, which leads over time to a fatigue break of the bristle tip; this is avoided by the bristle ends which according to 15 described embodiments are only tapered (not pointed). Simultaneously it was found that the bristles according to described embodiments are mechanically so stable that they have on the buccal tooth surfaces a cleaning performance, which is similar or even superior to one of the 20 cylindrical bristles. The bristles according to described embodiments are furthermore better suited for cleaning interdental spaces and approximal tooth surfaces than bristles with non-tapered filament ends, since the bristles according to described embodiments can reach 25 approximal tooth surfaces better. Preferably D is in the range of 100 to 130 ptm, more preferably in the range of 100 to 125 pm. Also preferably the first tapered part of the bristle has a diameter of 30 120 to 165 ptm, as measured on the central axis at a distance of 1 mm starting from the piercing point, and a diameter of 90 to 135 prm at a distance of 0.1 mm, as measured in the same way.

-4 The bristle according to some embodiments has essentially (or to the technically possible extent) a rotationally symmetrical shape around the central axis. 5 The profile line of the tapered part of the bristle (i.e. the diameter of the tapered part as a function of decreasing distance from the piercing point of the central axis through the end face) runs preferably in a monotonically declining way towards the end face. The term 10 "monotonically declining" has in the context of the present application the usual mathematical meaning. More preferably the profile line of the tapered part is strictly monotonically declining in the mathematical sense. 15 The length of the tapered part (or, in the case of a bristle according to the invention bent in a U-shape and having two tapered parts, the length of both tapered parts) is preferably in the range of 6 to 10 mm. 20 The end face of the end of the first tapered part has at the said piercing point a surface normal which is preferably inclined by not more than 300 against the said central axis. This is generally automatically fulfilled if 25 the end face has been formed by trimming of a pointed end (see herein below) ; it may also be brought about by a suited, rounding-off treatment of the end face and its edges which are adjacent to the mantle surface of the tapered part (see herein below). 30 Three particularly preferred types of bristles according to various embodiments are as follows: i) a bristle with a cylindrical part, to which is 35 adjacent exactly one essentially rotationally symmetrical tapered part of a length of 10 mm or less (i.e. this -5 bristle is analogous to a bristle being tapered on only one end); ii) a bristle with a cylindrical part and exactly two 5 essentially rotationally symmetrical tapered parts which are adjacent on opposing sides to the cylindrical part, each being of a length of 10 mm or less (i.e. this bristle is analogous to a bristle being pointed on both ends), in particular whereby the two tapered parts are essentially 10 of the same profile, and iii) a bristle with a cylindrical part, an essentially rotationally symmetrical tapered part of a length of 10 mm or less and an essentially rotationally 15 symmetrical pointed end, whereby the tapered part and the pointed end are adjacent on opposing sides to the cylindrical part. In all embodiments of the bristle, the edges, which 20 may occur between the end face and the tapered part, may be removed by rounding off, as is customary for cylindrical bristles. The rounding off may be carried out by means of customary known processes, e.g. by using a grit paper. 25 Particularly preferred profile lines of the first tapered part are approximately according to the following profile tables 1 to 4. These indicate the diameters in function of the distance from the piercing point of the 30 central axis through the end face (mean values with standard deviation from 6 specimens of each of these bristles). In the right outermost column of each table the maximal diameter of the cylindrical part (Dsyl) of the bristle is indicated. In line with the measuring 35 definition for the diameter D of the first tapered part, -5a each table also indicates at a distance X = Dzyi the corresponding diameter value. Furthermore the profile tables 1 to 4 also indicate the diameter values at a distance of 0.1 mm from the end face, in order to 5 exemplify the preferred profile of the first tapered part near the end face.

LD 0~m 0 - 0 0 0 0 CQ 0 CD C 0 0 0; n 0m U-) 0' 0 n CD CDN 0 o C) (N 00 0 -4 0 Cn a 10 0) 0 .0 0) 0 10 0 0) CO 0 0 CD0 00 0 0 0 0 0) 0 0: o 0 a)1 -I (~0N Ln d~*0 0 L~ 0 OD 0c lc 0 0 N 0 -4 0) r, 0 0 ( 0 00( 0)~~~ o )a C o C (N 0 C -. (N 0 0C 0% W 0 0- 0D L 0D 0) W 0 0 (N0 0o 0 .0 0 C) 0 C c -4 Ln 0 0D LA 0 .0 ol 0 oA 0 m r, on 0 0) CC 0 LA 0 M4 0 0 0 m OD (N LAC)n C 9 0n 00 C0 I Cr0 0 C) -4 C00m 0 ~* 0 0; r. (N Ln 0 IA 0 N- 0 A 4 0) .4 0 N 0 0 0 0) C; 0 0 C4 -0 -00 0- 00 N 4 0 - 0 qw 1 (N 1* "1 0~ 0 0 C) 0 0 N0 0 CN -r0 a 0C C. C 0 0 1 1- 0 0 C; 0 0 0 '0 0 C C 0 0 oD oo 0 0D 0 m 0 m LA C) 01 C;0 0 .4 .40 . 0 -4 , CD o, 0 C 0 0C 1 0 mo w400 a, 0, 0 E 0 0 C: 0 a 0 0 0 0 0 0 1- 41 II)- 4 )U E W41) )U1 'u Q) Q ) U 0) Q ) U w u U Q -H D d) (a Q) a) a) + kW 4-) E) EE4 - 4 0 -)' r 0 E) m- 0 E -aD)'0 L4-4 C w -4 C: w- C: 4 -4 a -A 4 (N N -7 It may happen that in some embodiments of the bristle the diameter at the end face and at a small distance from the end face cannot be measured reasonably anymore. This is the case when the bristle end of the tapered part has 5 been subject to a subsequent rounding off. This rounding off may in some instances bring about at the end of the bristle irregular and jagged shapes and uneven surfaces, which makes the direct measurement of the diameter near the end face impossible. It was now also surprisingly 10 found for the described bristles that in these cases the diameter near the end face or at the end face may be determined approximately by a parabolic extrapolation, whereby the diameters of the bristle at distances of 1, 2 and 3 mm from the end face are taken as the support points 15 for the parable. These support points are indicated in bold in the above tables. To prove that this works the above tables indicate at a distance of zero from the end face both the original, actually measured diameters of the bristle (as they were after trimming of the end but before 20 the rounding off) and, immediately below in parentheses, the diameters determined by that extrapolation. The deviation between the actual diameter and the diameter determined by the extrapolation is minimal. Such a simple extrapolation is possible for the bristles because the 25 curvature of the tapered end is less pronounced than with the prior art bristles. The described bristles may consist of a plastic suitable for toothbrush bristles. They may preferably be, 30 on the one hand, of a polyester, in particular of a polyester obtainable from a (C 2

-C

4 )-l,o-alkylene glycol and terephthalic acid. More preferably the polyester is polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), and particularly preferred is PBT. On -8 the other hand they may be of a polyamide, in particular of a polyamide obtainable from a (C 2 -CO)-l,o-diamine and a

(C

2

-C

8 )-1l,o-dicarboxylic acid; particularly preferred is here polyamide-6,6 (e.g. nylon). 5 For the production of the described bristle one may start from commercially available bristles being pointed on one end or on both ends, or from cylindrical bristles. At the time of filing the instant application producers of 10 such bristles were e.g. Pragma, Shinyoung, Wessen, Hylon, Sogo, Best Whasung or Cheil Jedang. Bristles according to described embodiments, which have exactly one first tapered part, may e.g. be obtained 15 from a commercially available bristle being pointed on only one end by trimming of the pointed end, with simultaneous formation of the tapered end and the end face. In order for the overall bristle to have a length suitable for toothbrush bristles the other, cylindrical 20 end of the bristle may be cut appropriately to size. Bristles according to described embodiments which have, besides the first tapered part, either a second tapered part or a pointed part, may generally be prepared 25 from commercially available cylindrical bristles of appropriate length by chemical etching of the ends to the suited tapered or pointed shape. This etching process has been known in the field of pointed bristles for a long time. Here again the tapered end may optionally be trimmed 30 in order to achieve a useful overall length of the bristle. On the other hand doubly pointed bristles are commercially available which only need to be appropriately -9 trimmed on both ends in order to arrive at a bristle having two tapered parts and having a length suitable for toothbrushes (see example 1). 5 In the chemical etching process the bristles may firstly be trimmed to a uniform length. Then they may be etched by immersing them perpendicularly into an etching liquor of typically 80 to 150 0 C. Examples for etching liquors are inorganic solutions, such as a strongly 10 alkaline etching solution (e.g. a 25-50 percent by weight aqueous solution of NaOH or KOH) or a strongly acidic etching solution (e.g. a 60-98 percent by weight aqueous solution of sulphuric acid). Examples for etching liquors are also organic solvents such as m-cresol, 15 trifluoroacetic acid, o-chlorophenol, trichlorophenol, DMSO, DMF and a mixture of phenol and tetrachloroethane. The duration of the immersion may typically be 10 to 20 minutes, whereby during this time the bristles may optionally be withdrawn gradually from the etching liquor 20 at an arbitrarily chosen constant speed or speed which varies over time, whereby the profile of the etched end (i.e. the monotony of the profile line) may be influenced. After the etching the ends may be washed, depending on the etching liquor, with water, dilute base, dilute acid or a 25 suited solvent at typically ambient temperature, and dried. The etching conditions (type and temperature of the etching liquor, duration of the immersion) may on the one hand be chosen such that the diameter D of the tapered 30 part is after the etching already within the range according to described embodiments, which is 100 to 140 pm. For this the etching is carried out for a shorter time than the etching of a prior art pointed bristle. On the other hand the conditions of the etching may be chosen -10 such that firstly a pointed end is formed, which is then trimmed with obtention of the end face and the tapered part. 5 If desired the ends of the bristles may, after having been etched in an alkaline or acidic solution, additionally be trimmed before rounding off the ends. Whether the ends need to be trimmed may simply be determined by examining the state of the ends by means of 10 a magnifying glass, after the ends have been taken out of the solution. The bristles according to at least some embodiments may be inserted into the bristle carrier of a toothbrush 15 in a way which is analogous to the way used for prior art single or doubly pointed bristles. Here, bristles according to at least some embodiments with two tapered parts or with one tapered part and a pointed part are preferably inserted into the bristle carrier in an U-bent 20 shape using anchor plates. Bristles with only one tapered part on the other hand are preferably inserted in an unbent shape into the bristle carrier using a process, which is known in the art as "AFT process" (anchor free tufting). 25 Brief Description of the Drawings The embodiments are now further illustrated with reference to the example and figures, whereby in the figures 30 - Fig. 1 shows a cross-sectional view of a bristle according to some embodiments, whereby measuring parameters are also indicated; - I1 - Fig.'s 2, 3 and 4 show three embodiments of bristles; and - Fig.'s 5 and 6 show tests for in vitro cleaning 5 performance on blackened, then TiO 2 -coated teeth with bristles according to described embodiments and conventional cylindrical bristles. Detailed Description of the Drawings 10 Example 1: Preparation of bristles with two equal tapered ends according to above profile tables 1 to 4 As the starting bristles were used four commercially available, doubly tapered bristles which were as follows: 15 starting bristles trimmed at a To obtain the distance from profile of above the end [mm] table No. Pragma 0.18 x 28 mm 2 1 033004 A-BBC Pragma 0.19 x 28 mm 1 2 033004 A-BBC Shinyoung 0.20 x 28 mm 2 3 Wessen 0.18 x 24 mm 2 4 Each of the starting bristles was trimmed at both 20 pointed ends at the distances as indicated in the middle column of the above table. The ends of the tapered parts of the bristles so obtained were rounded off with a TR89 Bristle 25 -12 Rounding Machine (manufactured by Tsujimura Co., Japan) using a grit paper of 240 mesh. 5 Figure 1 shows an end with a tapered part of a bristle. On the right side is shown the cylindrical part 1, the constant diameter of which simultaneously means the maximal diameter Dzy 1 of the bristle. Adjacent to the cylindrical part 1 is a tapered part 21, the tapering of 10 which starts at a distance L from the piercing point 6 of the central axis 5 through the end face 4, and which extends in a strictly monotonically declining way to the end 3. The end face 4 of the end 3 is shown here after an idealized rounding off, i.e. in an approximately 15 hemispherical shape; due to the trimming and subsequent real rounding off this end face could as well be rather planar, but with more or less irregular or jagged edges. Also shown is that the diameter D which is essential for the invention is measured at a distance X from the 20 piercing point 6, whereby the distance X is equal to the said maximal diameter Dzyi of the cylindrical part. Figures 2-4 show three bristles. In all these figures the bristle is shown bent in an U-shape, in which shape 25 the bristles particularly of figures 2 and 3 would be inserted into the bristle carrier of a toothbrush. The bending over is done in the cylindrical part 1, which is then itself bent in an U-shape. Figure 2 shows a bristle with two tapered parts 21, 22; figure 3 shows a bristle 30 with a first tapered part 21 and a pointed end 7; and figure 4 shows a bristle with only one tapered part 21, whereby the remainder of the bristle is formed of a cylindrical part 1. This latter bristle could, in -13 deviation from figure 3, also be inserted in an unbent shape into the bristle carrier of a toothbrush head. Figures 5 and 6 show tests for cleaning performances, 5 which were obtained on blackened, then TiO 2 -coated teeth. Tested were: (A) Brushes with bristles having two tapered ends, being rotationally symmetrical and which were inserted in an U 10 bent shape into the brush (see figure 2) having a bristle field with a height of 11.5 mm; the bristles had a maximal diameter Dzyi of about 0.21 mm and a diameter D at a distance X = Dy 1 of about 0.104 mm (these bristles corresponded approximately to the profile exemplified in 15 above table 3); and (B) Brushes with conventional cylindrical bristles which were inserted in an U-bent shape into the brush and which had a diameter Dzyi of 0.175 mm; the height of the bristle 20 field was 11.5 mm. In these tests the teeth of a model of a sextant of an upper jaw (with three molars, three premolars and one cuspid) were firstly coloured black and then whitewashed 25 in white with a TiO 2 paste (25 g in 75 ml 26% aqueous ethanol). After one standardised brushing step of 1 min duration with the bristle field to be tested and with an applied pressure weight of 250 g the fraction of the teeth surfaces, which had been cleaned from the TiO2 paste, was 30 determined. This procedure was used in a standardised way for each of the bristle fields to be tested, using for each a horizontal, vertical and a rotatory cleaning movement, which procedure was repeated four times for each bristle field to be tested and each cleaning movement. In -14 the horizontal cleaning (indicated in the figures with white bars) the standardised brushing step consisted of 60 forward and backward movements with an amplitude of 30 mm; in the vertical cleaning (indicated in the figures with 5 hatched bars) it consisted of 60 upward and downward movements with an amplitude of 8 mm; and in the rotatory cleaning (indicated in the figures with dotted bars) it consisted of 60 circles with radius of 4 mm with simultaneous 16 horizontal forward and backward movements 10 with an amplitude of 30 mm. The measured cleaning performances, i.e. the fraction of removed TiO 2 , are indicated in the figures 5 and 6 in arbitrary units. Figure 5 shows the sum of the mean values of the 15 cleaning performances after horizontal, vertical, and rotatory cleaning movements with the bristles according to described embodiments (bar A) and with the conventional cylindrical bristles (bar B) on buccal tooth surfaces. 20 Figure 6 shows the sum of the mean values of the cleaning performances after horizontal, vertical, and rotatory cleaning movements with the bristles according to described embodiments (bar A) and with the conventional cylindrical bristles (bar B) on mesial/distal tooth 25 surfaces, i.e. on the tooth surfaces facing the interdental spaces. It can be seen from figure 5 that the bristles according to described embodiments are, despite a lower 30 mechanical rigidity, slightly better on buccal tooth surfaces with horizontal and vertical cleaning movements than the conventional bristles. It can be seen from figure 6 that the bristles according to described embodiments are clearly better than the conventional bristles in -15 particular in the horizontal and vertical cleaning movements on mesial/distal tooth surfaces.

Claims (12)

1. A bristle for a toothbrush, comprising: a cylindrical part with a maximum, constant cylinder 5 diameter Dzyi; adjacent to the cylindrical part a first tapered part with a bristle end and an end face delimiting the bristle end, whereby the first tapered part tapers towards the bristle end; and 10 an imaginary central axis which runs through the cylindrical part and the first tapered part and which pierces the end face at a piercing point; whereby the first tapered part has a length L of 10 mm or less and at least 3 mm, as measured on the central 15 axis starting from the piercing point; wherein the first tapered part has a diameter D of 95 to 140 pm, as measured on the central axis starting from the piercing point at a distance X being equal to the cylinder diameter Dzyi. 20

2. A bristle for a toothbrush according to claim 1, wherein D is in the range of 100 to 130 pm, preferably of 100 to 125 pm. 25

3. A bristle for a toothbrush according to claim 1 or 2, wherein the first tapered part has a diameter of 120 to 160 pm, as measured on the central axis at a distance of 1 mm from the piercing point, and has a diameter of 90 to 135 pm at a distance of 0.1 mm, as measured in the same 30 way.

4. A bristle for a toothbrush according to any one of claims 1 to 3, wherein the bristle has a second tapered part adjacent to the cylindrical part on the side opposed 35 to the first tapered part. 17

5. A bristle for a toothbrush according to claim 4, wherein the second tapered part has essentially the same shape as the first tapered part. 5

6. A bristle for a toothbrush according to any one of claims 1 to 3, wherein the bristle has a pointed end adjacent to the cylindrical part on the side opposed to the first tapered part. 10

7. A bristle for a toothbrush according to any one of claims 1 to 6, wherein Dayi is in the range of 150 to 170 pm or in the range of 180 to 210 pm.

8. A bristle for a toothbrush according to one of claims 15 1 to 7, consisting of a polyester or a polyamide.

9. A bristle for a toothbrush according to any one of claims 1 to 8, consisting of polyethylene terephthalate, polybutylene terephthalate or polyamide-6,6. 20

10. A toothbrush comprising one or more bristles according to any one of claims 1 to 9.

11. A bristle substantially as hereinbefore described 25 with reference to the accompanying drawings.

12. A toothbrush comprising bristles substantially as hereinbefore described with reference to the accompanying drawings. 30