Note: Descriptions are shown in the official language in which they were submitted.
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Title
Low Friction Toothbrush
Field of the Invention
The present invention relates to a toothbrush and a
method of cleaning teeth. In particular, the invention relates to
the use of a composition containing a thermoplastic polymer and
a slip agent to prepare a filament for use as a bristle in a
toothbrush.
Background of the Invention -
Bristles for use in a toothbrush have conventionally
been manufactured from a filament that is prepared from a
thermoplastic polymer. There is a continuing need to improve
the cleaning efficacy of toothbrush bristles manufactured from
such polymeric filaments. This invention relates to a method of
iinproving the cleaning efficacy of such a toothbrush bristle by
reducing the coefficient of friction that the bristle experiences
when in contact with a tooth. It has been found that a useful
means of reducing the coefficient of friction experienced by a
toothbrush bristle when in contact with a tooth is to manufacture
the bristle from a filament prepared from a composition
containing a thermoplastic polymer and a slip agent.
US 5,462,798 ("Gueret") discloses a brush used as an
applicator for thick liquid cosmetic products such as nail varnish
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or mascara. The bristles or hairs of the brush are made from a
plastic that contains a slip agent. The presence of the slip agent
reduces the wettability of the hairs of the applicator, and limits
the attachment of the product to the hairs. This condition
enhances the tendency of the product to remain on the substrate
to which applied, rather than on the hair, and facilitates
distribution of a thicker layer of the product on the substrate.
There is no mention in Gueret of the use of such a hair
or bristle for cleaning teeth. We have found, however, that the
use of a bristle manufactured from a filament prepared from a
composition of a thermoplastic polymer and a slip agent does
reduce the coefficient of friction experienced by the bristle when
in contact with a tooth to such an extent that the cleaning
efficacy of the bristle is improved.
Summary of the Invention
In one aspect, this invention involves a brush for use
in cleaning teeth having bristles that are prepared from a
composition containing a thermoplastic polymeric resin in
admixture with a slip agent.
In another aspect, this invention involves a method of
cleaning teeth by (a) providing brush that has bristles that are
prepared from a composition containing a thermoplastic
polymeric resin in admixture with a slip agent, and (b) applying
the brush to the surface of one or more teeth to clean the teeth.
The toothbrush of this invention has been found to
possess superior cleaning efficacy, particularly for cleaning
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between the teeth, because of the presence of a slip agent in the
filament from which the toothbrush bristles are manufactured.
Brief Description of the Drawinas
Fig. 1 shows a side elevation of a toothbrush.
Fig. 2 shows an end elevation of a toothbrush.
Fig. 3 shows a plan view of a toothbrush.
Fig. 4 shows a side elevation of a toothbrush.
Fig. 5 shows a side elevation of a toothbrush.
Fig. 6 shows a twisted bristle toothbrush.
Fig. 7 shows a wrapped bristle toothbrush.
Fig. 8 shows an end view of a wrapped bristle
toothbrush.
Fig. 9 shows a boundary frictometer.
Detailed Description of the Invention
The filaments used in this invention for brush bristle
manufacture can be produced from a wide variety of well known
thermoplastic polymers including polyamides, polyesters,
polyolefins, fluoropolymers, polyurethane, polyvinylchloride,
polyvinylidene chloride, styrenic polymers and copolymers, and
any compatible combination thereof. Polyamides are preferred,
and some of those include nylon 6, nylon 11, nylon 6,6, nylon
6,10, nylon 10,10, and nylon 6,12. Polyesters useful for
filament production include polybutylene terephthalate and
polyethylene terephthalate, and blends thereof. Of the many
polyolefins, polypropylene is preferred. Of the above, nylon 6,12
is most preferred.
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The polymer(s) from which a filament is produced in
this invention, for example nylon, may have an inherent viscosity
of about 0.9 to about 1.5 when measured in m-cresol according to
ASTM D-2857.
A slip agent for use in this invention is any substance
that, when added to a polymer to form a composition from which
a filament is produced, will reduce the coefficient of friction
experienced by that filament in contact with a tooth when the
filament is used as a bristle in a toothbrush. Slip agents useful
for preparation of such a composition include, for example, a
fluorinated olefin polymer, boron nitride, molybdenum disulfide,
graphites, fullerene and talc. Of these, a fluorinated olefin
polymer such as poly(tetrafluoroethylene) is preferred. A slip
agent is used in the composition in an amount of about 0.5 or
more, preferably about 1 or more, and more preferably about 2 or
more, and yet about 10 or less, preferably about 6 or less, and
more preferably about 4 or less, weight percent based on the total
weight of the composition of polymer plus slip agent.
Filament production may be accomplished by the use
of an extruder, many varieties of which, such as a twin-screw
extruder, are available from manufacturers such as Werner and
Pfleiderer. A polymer in the form of granules is fed from a feeder
unit into the extruder either volumetrically or gravimetrically. A
slip agent is fed from a separate feeder into the extruder through
a side-arm port, and is blended with the polymer in the extruder
at a temperature of 150-285 C. Alternatively, the slip agent can
be pre-compounded or pre-blended with the polymer so that a
separate feed system is not required. The polymer and slip agent
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are mixed as a melt in the extruder, and the resulting
composition is then metered to a spin pack having a die plate.
The composition is filtered, and filaments of various shapes and
sizes are produced by extrusion through the holes in the die plate.
The cross-sectional shape of the filament is
determined by the shape of the holes in the die plate, and may be
any shape such as round, oval, rectangular, triangular, or the
shape of any regular polygon; or the filament may be an
irregular, non-circular shape. The filament may be solid, hollow
or contain multiple longitudinal voids in its cross sections. Each
run of the extruder can produce any combination of cross-
sectional shapes by using a die plate with various shaped holes.
Filaments of one or more diameters may be made at the same
time by varying the size of the holes in the die plate. In the
toothbrush of this invention, use of a solid, round, single-strand
filament, having a substantially uniform cross-sectional
dimension, is preferred.
Alternatively, the filament used in this invention
may be produced by melt or solution spinning.
In the extrusion process, after a filament strand exits
the die plate, it is solidified in a water quench bath, and is then
transported through a series of draw rolls for stretching in an
amount of 1.5 to 6 times the original length. The filament is
drawn in accordance with a repetitive schedule of linear rates
involving a period of acceleration and deceleration, and a period
of uniform withdrawal. Orientation and stretching is performed
between two roll sets, by running the second roll set faster than
the first roll set, to improve longitudinal strength of the filament.
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The oriented filament may then be heated to induce partial
crystallization, rendering good bend recovery. The heat setting
is typically carried out in a gas, such as by blowing hot air over
the filament for a period of about 30 to about 120 seconds, or in a
liquid bath, such as by passing the filament through a bath of oil
for a period of about 2 to about 10 seconds. The filament is then
wound on a winder such as a drum or a spool.
Another aspect of this invention involves the use of a
sheath/core filament in which the sheath is produced from
polymer admixed with slip agent, but the core is produced from a
polymer neat, to which no slip agent has been added. By placing
the slip agent in the sheath, more of the slip agent is present at
or near the surface of the filament to provide the desired effect of
reducing friction. The sheath surrounds the core in a coaxial or
concentric configuration. The polymer used in the core and the
sheath may be the same or different, but must be compatible
since there must be adequate adhesion between the core and the
sheath. Nylon 6,12 is preferred as a sheath material.
A sheath/core filament is typically produced by
coextrusion using two extruders sharing a common spin pack.
The polymer used to make the core is channeled from a first
extruder to the center of the spin plate holes, and the composition
used to make the sheath is channeled from a second extruder to
the outside of the spin plate holes.
A sheath/core filament, which is built from multiple
sources of flowable polymer or polymeric composition, as
described above, may be distinguished from a filament that is
only a single strand because it is produced from a single source of
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flowable polymeric composition. Such a single-source, single-
stranded filament may be referred to as a monofilament.
Although a filament for use in this invention may be either a
sheath/core filament or a monofilament, a monofilament is
preferred.
A filament for use in this invention may be straight,
curved, looped or arched; and may be tapered, feathered, tipped
or flagged. A straight filament with a smooth, rounded or blunt
end is preferred.
A filament for use in this invention has a diameter, or
maximum cross-sectional dimension, of about 1 or more,
preferably about 2 or more, and more preferably about 2.5 or
more, and yet about 15 or less, preferably about 10 or less, and
more preferably about 5 or less, mils. A mil is 0.025 mm.
A filament for use in this invention has (1) a tensile
modulus of about 100 to about 1000 kpsi, and preferably about
400 to about 700 kpsi, as measured by ASTM D-638; (2) a tensile
strength of about 10 to about 100 kpsi, and preferably about 40 to
about 80 kpsi, as measured by ASTM D-638; (3) an elongation of
about 1 to about 100%, and preferably about 10 to about 50%, as
measured by ASTM D-638; and (4) a bend recovery of about 80 to
about 100%, and preferably about 92 to about 100%, as measured
by the mandrel bend method as described in Bend Recovery of
Tynex and Herox Nylon Filaments, in Tynex Nylon Filament
Technical Data Bulletin No. 5, September, 1971, available from
E.I. du Pont de Nemours and Company.
A filament for use in this invention may contain other
additives or have coatings provided that they do not interfere
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with the operation of the slip agent. For example, the filament
may contain anti-microbial additives or therapeutic agents.
A filament is used in this invention as a bristle in a
toothbrush. A toothbrush may be made by techniques known in
the art, including the staple set, ferrule and filament, metal strip,
fusion, or sub-assembly techniques. In a toothbrush, filaments
are often grouped together as bristles to form a bristle tuft.
Filaments of different colors, diameters, polymer compositions,
lengths and shapes can be combined in one tuft to achieve a
specific brush characteristic or appearance.
Bristle color is often important in a toothbrush. A
filament used in this invention may have any desired color
obtained by adding a pigment, dye or colorant to the composition
from which the filament is made provided that the operation of
the slip agent is not impeded. Bundles of filaments may be
produced that contain randomized variations of color and shade.
Bristle tufts may thus be manufactured with color or shade
variation within a tuft and/or from tuft to tuft, and this allows
manufacture of a brush having an attractive visual effect, or in
which shade differences are chosen to highlight specific end-
product features.
The term toothbrush refers herein to any type of
device in any shape that enables the use of bristles to clean a
tooth. In Figs. 1-3, a typical manual toothbrush 2 is shown in
which at least one tuft 4 of bristles 6 is affixed to and extends out
in a generally perpendicular direction from a brush head 8, which
is a planar, or essentially planar, surface. A tuft 4 will have a
plurality of bristles 6 prepared according to this invention, and
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the head 8 will typically have a plurality of tufts 4. The head 8 is
in turn attached to a brush handle 10, and the head 8 and handle
make up brush body 12. The configuration of the tufts 4 and
head 8 can vary and may be oval, convex curved, concave curved,
5 flat trim, serrated "V", or any other desired configuration. The
toothbrush in Fig. 1 contains tufts that are oriented in straight
rows and columns, but the tufts may be arrayed in any manner,
for example with a diagonal orientation or with each succeeding
row or column offset from the previous. While the illustrated
10 embodiment shows that the length of the bristles are
substantially the same, the bristles can be cut to any desired
length, to differing lengths, to other shapes, such as grooved, or
other configurations as desired. The length of the portion of the
bristles protruding from the brush head will typically be
substantially uniform, and will be between about 5 to about
15 mm, and preferably between about 8 to about 14 mm.
Additionally, the axes of the head 8 and the handle 10 may be on
the same or a different plane. A brush such as shown in Fig. 1
may also be adapted to electrically mechanized operation.
Alternatively, a toothbrush of this invention may
have a rounded or cylindrical shape in which bristles extend
radially out from a central axis in multiple directions toward a
circumferential perimeter about the central axis. For example,
as shown in Figs. 4 and 5, a cylindrical brush body 14 has first
and second opposite axial ends 16 and 18 and a generally
cylindrical sidewall 20. A spiral groove 22 is formed in the
cylindrical sidewall 20 and extends from end 16 to end 18.
Bristles 24 are secured within the spiral groove and extend from
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the cylindrical sidewall. Multiple spiral grooves, which may
optionally be truncated, could also be used for this purpose.
Although not shown, a variation on this embodiment would be to
cut longitudinal grooves in the cylindrical sidewall, parallel to the
central axis, and secure bristles in each of those longitudinal
grooves. The grooves as described above may be machined into a
solid, cylindrically-shaped brush body, or, if the brush body is
hollow, bristles as seated in the grooves may be secured from the
inside of the brush body.
Alternatively, in a toothbrush of this invention
having a rounded or cylindrical shape, securing means other than
a brush body may be used to secure bristles that extend radially
out from a central axis in multiple directions toward a
circumferential perimeter about the central axis. For example,
as shown in Fig. 6, a cylindrical brush 26 may be formed by
twisting, plying or wrapping together two or more bristle sub-
assemblies, such as bristle sub-assemblies 28, 30 and 32. A
twisting machine 34 of any appropriate design can be used to
twist together the bristle sub-assemblies. Twisted bristle sub-
assemblies may be bonded together by a fast setting adhesive or
solvent applied by device 36 at the junction of the converging
bristle sub-assemblies. Other fastening techniques may be
employed, such as extrusion of a polymeric material, heat fusion
and frictional interlocking.
Fig. 7 shows a variation of the embodiment of Fig. 6,
in which a brush 38 is made by spiral wrapping two strands of
securing material 40 and 42 with bristles 44. A twisting device
46 takes the three separate feeds, creates a retaining device from
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the securing niaterial, for example wire, clasps the bristles with
the retaining device, and produces the spiral-wrapped brush 38.
An end view of the brush 38 is shown in Fig. 8. An end view of
the brush 26 would have a similar appearance. This type of
toothbrush is sometimes referred to as an inter-dental or inter-
proximal brush.
In a toothbrush of this invention that has a rounded
or cylindrical shape in which bristles extend radially out from a
central axis in multiple directions toward a circumferential
perimeter about the central axis, the portion of the bristles
protruding from the central axis may have a length of about 0.5
to about 6, and preferably about 1 to about 4, mm. The term
toothbrush is not limited herein to any of the particular
embodiments illustrated or discussed above, and may for example
be made from a bristle subassembly.
The advantageous effects of this invention are
demonstrated by a series of examples, as described below. The
embodiments of the invention on which the examples are based
are illustrative only, and do not limit the scope of the invention.
The significance of the examples is better understood by
comparing these embodiments of the invention with certain
controlled formulations, which do not possess the distinguishing
features of this invention.
The compositions tested in the examples were
prepared by blending nylon 6,12 with a masterbatch in which
nylon 6,12 had been modified by the addition of a slip agent such
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as poly(tetrafluoroethylene) ("PTFE"). The PTFE used was
Teflon MP1400 or MP1600 Micropowder from DuPont, and was
used at a content level of 30 weight percent of the masterbatch.
Teflon MP1400 Micropowder has an average particle size in the
range of 7 to 12 microns, and Teflon MP1600 Micropowder has
an average particle size in the range of 4 to 12 microns. The
controls involved testing of nylon 6,12 to which there was no
addition of a slip agent.
In the case of both the examples and the controls, the
blended composition, or the nylon itself, was melted and mixed in
an extruder, and was then metered by a melt pump and forced
through a spin pack and spinneret plate to form round strands.
The strands were quenched in water, then heated above the glass
transition point of the nylon and stretched between 3 to 5 times
the initial length to give an oriented filament. The filament was
then heat set in air at between 150 and 180 C in order to impart
the type of bend recovery required for a toothbrush filament.
The filament was subsequently coated with a surface lubricant
and then packaged.
Filaments made in the manner described above were
tested to determine coefficient of friction by the boundary friction
test described below, and were also used as the bristles from
which a toothbrush was made. Each toothbrush was a 44 tuft,
flat trim toothbrush made by the staple set process, and was
similar to that shown in Fig. 1.
The filament size and content of the compositions
tested in the examples are shown in Table 1, in which the amount
of Teflon MP1400 or MP1600 Micropowder in the final
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composition is shown, the remainder of each composition being
nylon 6,12. As Controls A and B were each made from with
nylon without the addition of any slip agent, they are shown in
Table 1 as containing no Teflon Micropowder.
Table 1
Amount of Teflon Micropowder
and filament size in Examples 1-7 and Control A and B
Type of Weight Percent Filament
micropowder of micropowder size
Example 1 MP1400 2% 8 mil
Example 2 MP1400 4% 8 mil
Example 3 MP1600 2% 8 mil
Example 4 MP1600 4% 8 mil
Control A None None 8 mil
Example 5 MP1600 1% 7 mil
Example 6 MP1600 2% 7 mil
Example 7 MP1600 4% 7 mil
Control B None None 7 mil
The filaments in Examples 1-7 and Controls A and B
were tested to determine coefficient of friction by the boundary
friction test. Friction is the resistance to relative motion of two
bodies in contact caused by inequalities in the surfaces of the
respective materials from which the bodies are made. The ratio
of (i) the force required to maintain a uniform velocity of one body
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with reference to the other to (ii) the perpendicular pressure
between the surfaces is the coefficient of friction, which is a
unitless value. Coefficient of friction by the boundary friction
test is determined by use of a boundary frictometer.
A boundary frictometer is shown in Fig. 9. It
measures the coefficient of friction when material (in this case
filament) is in contact with material, and when material
(filament) is in contact with a polished chrome surface. When a
filament/filament measurement is made, a sample of the filament
is wound onto a paper core or tube 48 that is mounted on a
rotating mandrel 50. A loose filament 52 made from the same
material is draped over the filament-covered core 48. One end of
the draped filament 52 is attached to a strain gauge 54, such as a
Statham transducer, and the other end is attached to a weight
56. The weight may be any amount that is effective to hold the
draped filament in tight contact with the core 48, but that does
not distort the performance of the draped filament or overload the
strain gauge. Thirty grams is a typical amount of such weight.
The filament-covered core 48 rotates at speeds of 0.0016 cm/s to
32 cm/s. The tension generated by the movement of the
filament-covered core 48 across the draped filament 52 is
measured by the strain gauge, and the value of the coefficient of
friction is calculated from the tension data. When a
filament/metal measurement is made, the same procedure as
described above is followed except that the loose filament 52 is
draped over a polished chrome surface on the mandrel instead of
over the filament-covered core 48.
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The results of the filament/filament boundary friction
test for Examples 1-4 and Control A are shown below in Table 2.
In Table 2, the speeds shown are the different speeds of the
mandrel in centimeters/sec (cm/s) at which the measurement was
performed. These results show that at each speed at which the
measurement was made, the filaments used in Examples 1-4,
containing a slip agent, experienced a lower coefficient of friction
than the filament used in Control A, which did not contain a slip
agent. The lower coefficient of friction indicates that, because of
the presence of the slip agent in the filaments used in Examples
1-4, there was less friction between the draped filament and the
filament-covered core than there was in the case of Control A, in
which a filament was used that contained no slip agent.
Table 2
Results of Filament/Filament
Boundary Friction Test
0.0016 0.0032 0.0320 0.3200 3.200 32.0000
cm/s cm/s cm/s cxn/s cm/s cm/s
Example 1 0.25 0.25 0.24 0.24 0.23 0.26
Example 2 0.23 0.22 0.22 0.22 0.22 0.24
Example 3 0.24 0.24 0.23 0.22 0.22 0.24
Example 4 0.21 0.20 0.20 0.20 0.20 0.22
Control A 0.38 0.40 0.56 0.50 0.36 0.40
The results of the filament/metal boundary friction
test for Examples 1-4 and Control A are shown below in Table 3.
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In Table 3, the speeds shown are the different speeds of the
mandrel in centimeters/sec (cm/s) at which the measurement was
performed. These results show that at each speed at which the
measurement was made, the filaments used in Examples 1-4,
containing a slip agent, experienced a lower coefficient of friction
than the filament used in Control A, which did not contain a slip
agent. The lower coefficient of friction indicates that, because of
the presence of the slip agent in the filaments used in Examples
1-4, there was less friction between the draped filament and the
metal surface than there was in the case of Control A, in which a
filament was used that contained no slip agent.
Table 3
Results of Filament/Metal
Boundary Friction Test
0.0016 0.0032 0.0320 0.3200 3.200 32.0000
cm/s cm/s cm/s cm/s cxn/s cm/s
Example 1 0.22 0.21 0.22 0.23 0.26 0.34
Example 2 0.21 0.22 0.22 0.22 0.23 0.31
Example 3 0.21 0.21 0.21 0.23 0.24 0.32
Example 4 0.20 0.20 0.21 0.23 0.24 0.32
Control A 0.32 0.31 0.33 0.37 0.47 0.69
The results of the filament/metal boundary friction
test for Examples 5-7 and Control B are shown below in Table 4.
In Table 4, the speeds shown are the different speeds of the
mandrel in centimeters/sec (cm/s) at which the measurement was
performed. These results show that at each speed at which the
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measurement was made, the filaments used in Examples 5-7,
containing a slip agent, experienced a lower coefficient of friction
than the filament used in Control B, which did not contain a slip
agent. The lower coefficient of friction indicates that, because of
the presence of the slip agent in the filaments used in Examples
5-7, there was less friction between the draped filament and the
metal surface than there was in the case of Control B, in which a
filament was used that contained no slip agent.
Table 4
Results of Filament/Metal
Boundary Friction Test
0.0016 0.0032 0.0320 0.3200 3.200 32.0000
cm/s cm/s cm/s cm/s cm/s cm/s
Example 5 0.12 0.11 0.11 0.13 0.16 0.34
Example 6 0.12 0.11 0.12 0.12 0.14 0.33
Example 7 0.11 0.10 0.10 0.10 0.11 0.23
Control B 0.14 0.13 0.14 0.16 0.24 0.44
A toothbrush was made, using the filaments of
Examples 5-7 and Controls A and B, respectively, as the bristles
of the brush. Each brush was tested to determine the
interproximal access efficacy ("IAE") of the brush stroke. The
testing equipment was fabricated according to the design of
Nygaard-Ostby, Edvardsen and Spydevold as described in Access
to Interproxirraal Tooth Surfaces by Different Bristle Designs and
Stiffnesses of Toothbrushes, Scand. J. Dent. Res. 1979: 87: 424-
430. The testing technique to evaluate brushing efficacy
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involved independent evaluations of each toothbrush in both a
vertical and horizontal brushing motion, on tooth shapes
simulating anterior and posterior teeth, and at a brushing weight
of 250 grams. All brushes were stored at a temperature of 67-
70 F for a minimum of 48 hours before testing. Brushing was
conducted with the bristles placed at a 90 angle to the tooth
surface. The brushing apparatus was set to brush 15 seconds at
two strokes per second with a 50 mm stroke. The maximum
width or IAE of the brushing stroke was recorded on pressure-
sensitive paper placed around the simulated anterior or posterior
teeth. The various tests on each brush were repeated four times.
The results of the test to determine IAE are shown
below in Table 5. In Table 5, the four types of tests are labeled
AV, PV, AH and PH. AV is anterior vertical (i.e. a vertical stroke
on an anterior tooth surface), PV is posterior vertical, AH is
anterior horizontal, and PH is posterior horizontal. For each
example or control, the mean and standard deviation ("S.D.") of
the four repetitions of each type of test are reported, as are an
overall score that is calculated by taking the mean and standard
deviation of all sixteen tests performed on a particular brush.
The reported results are measured in mm, and are in each case
the width of the area cleaned by the particular brush stroke.
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Table 5
IAE Test Results
AV PV AH PH Overall
Mean S.D. Mean S.D. Mean S.D. Mean S.D. Mean S.D.
Example 5 0.83 .05 1.11 .03 0.67 .05 0.51 .03 0.78 .23
Example 6 0.87 .05 1.11 .02 0.68 .04 0.61 .05 0.82 .20
Example 7 0.85 .06 1.13 .03 0.70 .04 0.78 .12 0.86 .17
Control A 0.75 .04 1.09 .03 0.68 .04 0.56 .08 0.77 .21
Control B 0.82 .06 1.10 .02 0.69 .05 0.56 .05 0.79 .21
The results in Table 5 show that, with very few
exceptions, the brushes containing bristles made from the
composition of nylon and a slip agent (Examples 5-7) cleaned a
wider area than the brushes in which the bristles contained no
slip agent (Controls A and B). The brushes of Examples 5-7
were able, in a stroke of the same size, to clean a wider area than
the brushes of Controls A and B because the slip agent present in
the bristles of the brushes of Examples 5-7 reduced the friction
experienced by those bristles in contact with the tooth, enabling
the bristles to move further in each stroke. The greater width of
cleaned area attained by the brushes of Examples 5-7 also
results in their attainment of a higher IAE score, indicating that
they would have greater cleaning efficiency, particularly
interproximal efficiency, than the brushes with bristles that
contain no slip agent.
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