Note: Descriptions are shown in the official language in which they were submitted.
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Interdental brush
Technical field
The invention relates to an interdental brush in which
filaments (or bristles) are held between two wire
sections which are twisted with one another. The
invention also relates to a method for producing such
brushes.
Prior art
Cleaning the spaces between the teeth with the aid of
interdental brushes has long been an indispensable part
of good dental hygiene. These interdental brushes
essentially comprise two thin, twisted pieces of wire
between which the bristles or synthetic filaments are
secured. Whereas the wire ends of the small brushes
previously had to be inserted into a handle by the user
(see US 4,222,143, Tarrson), modern interdental brushes
have a plastic part which can easily be fitted in the
handle (see, for example, EP 0 001 044 A1, Georg;
EP 0 203 082 B1, Curaden AG). Large or small brushes
are required depending on the width of the spaces
between the teeth. There is therefore a range of
brushes with different wire diameters and bristle
diameters. Systems which allow the patient to determine
the correct interdental brush easily and quickly are
also already known (see, for example, EP 0 892 625 B1,
Curaden AG).
It is repeatedly found to be the case in practice that
the fine interdental brushes, i.e. the brushes for the
narrow spaces between the teeth, are problematic to
use, i.e. they easily bend during use and, in some
circumstances, even break.
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Disclosure of the invention
The object of the invention is to make available an
interdental brush which belongs to the technical field
mentioned in the introduction and which is stable even
if the wire has a small diameter.
The object is achieved by the features of Claim 1.
According to the invention, the twisted wire sections
have a diameter of 0.3 mm or less and are made of a
nickel-free or low-nickel steel. In the context of the
invention, "nickel-free" or "low-nickel" refers to a
steel when the nickel content in the alloy is less than
0.05 by weight.
Interdental brushes according to the invention are
distinguished by an increased rigidity and an improved
restoring force. If the brushes, during use, are
introduced, for example, obliquely into the space
between the teeth and strike against something with the
tip or bend, then the twisted section will not deform
so easily, or, if it does deform, it is not so easily
subjected to permanent deformation. The properties of
thin brushes in particular can thus be appreciably
improved for the user. Using nickel-free wire also
increases the biocompatibility of the brush, without
any protective coatings being necessary.
The wire used preferably has a diameter of 0.15 mm or
more. This is because practical tests have shown that
the smallest interdental brushes which are customary
today, with a diameter of 0.15 mm to 0.30 mm, can be
used to good effect. Thick wires obviously result in
more stable brushes than do thin ones. In some cases,
however, it is advantageous if the wires are not chosen
to be as thick as possible. Thinner wires result in
more flexible brushes. A preferred wire diameter is in
the range of 0.18 - 0.27 mm.
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The wire used preferably has a tensile strength of
1000 N/mmz or more. In most cases, the tensile strength
need not be greater than 1200 N/mm2. Such wires do not
just result in a brush with a low risk of breakage;
they also permit processing in high-speed machines
involving pronounced bending. In the case of excessive
strength, processing may be made more difficult because
the wires can break. Surprisingly, it has been found
that the wires according to the invention can be
processed even if they have a tensile strength of
1000 N/mm2 and more. This is not the case with nickel-
containing wires.
It is preferable, but not absolutely necessary, for the
wires to comprise an austenite. Tests have shown that
the robustness of the filament support, which is formed
by the twisted wires, is favourably influenced as a
result. In addition, the corrosion resistance ensures
that brushes which have been stored for a long period
of time or are left lying around do not result in
problems for the user during use (because of corrosion
having occurred in the meantime).
Stretching or drawing out and twisting the wires during
processing in brush production increases the tensile
strength. The processed wires are to some extent
stiffer than those in the unprocessed state.
In mechanical and automated production of an
interdental brush, filaments are introduced in a manner
known per se between two wire sections, and the wire
sections are twisted with the filaments. According to
the invention, however, the wire used is not a
conventional nickel-containing wire, but instead a
nickel-free one. The wire sections can be formed by the
two halves of a single piece of wire. However, it is
also possible for them to be formed by two separate
wires.
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Further advantageous embodiments and combinations of
features of the invention will become evident from the
following detailed description and from the patent
claims taken in their entirety.
Brief description of the drawings
In the drawings used to explain the illustrative
embodiment:
Fig. 1 shows a schematic representation of the twisted
wire;
Fig. 2 shows a schematic representation of a cross
section.
In the figures, the same parts are basically provided
with the same reference labels.
Embodiments of the invention
In outward appearance, the interdental brushes
according to the invention are of the same design as
those in the prior art mentioned in the introduction.
Fig. 1 shows how the wire sections la, lb are twisted
with one another. The filaments are not depicted in
Fig. 1. They are firmly secured between the two wire
sections la, lb. It can be seen that the wire sections
1a, lb are bent to a relatively pronounced extent. They
as it were form the filament support.
Fig. 2 shows a cross section through the filament
support. The wire sections 1a, lb have a certain
diameter D. The filaments 2 are held between them. The
diameter D is defined in such a way that, on the one
hand, the filament support has a desired rigidity and,
on the other hand, the interdental brush is adapted for
a certain ease of movement. The ease of movement can be
determined, for example, by a probe, as is known from
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EP 0 892 625 B1, mentioned in the introduction. Among
other things, the diameter D and width B and the wire
material used (or its flexibility) are relevant for the
ease of movement.
Interdental brushes made of a nickel-free steel
(nickel-free in this context means a nickel content of
below 0.05 by weight) of the following composition
were successfully produced (weight measurements rounded
off; impurities not mentioned):
17$ by weight chromium
14~ by weight manganese
2$ by weight molybdenum
0.5$ by weight nitrogen
0.25$ by weight silicon
0.11$ by weight carbon
0.04 by weight nickel
0.02 by weight phosphorus
0.006$ by weight titanium
Remainder iron
The wire had a diameter of 0.23 mm and a tensile
strength of at least 1100 N/mm2 and not more than
1300 N/mm2. Further tests were carried out with a wire
having a diameter of 0.27 mm and made of the same
alloy. The tensile strength was at least 1000 N/mm2 and
not more than 1200 N/mm2.
The interdental brush provided with the new wire
withstands three times more frequent loading under
rotary bending than the traditional brush. (In this so
called rotary bending, the plastic part is clamped in
place, and a device rotates the tip of the brush in a
circle.)
It is of course possible to vary the above alloy
composition. The content of Cr and Mn may in each case
be changed, for example, by 3~ by weight. If the
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biocompatibility is particularly important, the content
of Ni is preferably also chosen lower.
It has surprisingly been found that the wire according
to the invention, in particular one with an alloy of
the preferred composition, holds the filaments better
than the wires known from the prior art. The filaments
(which, for example, have a diameter of 0.06 - 0.08 mm
and are typically made of polyamide) are in fact not
bonded to the wire, but instead are just secured firmly
between the two wire sections. In practice, the
interdental brushes are repeatedly bent in one
direction or another. Whereas, in conventional wires,
this leads to the spirals loosening and to some
filaments falling out (and possibly catching in the
gums of the user), the brush with the wire according to
the invention remains compact.
It has further been found that, using a wire with the
alloy according to the invention, 10$ to 20$ smaller
wire diameters than a prior art are sufficient for
achieving the same brush stability or brush rigidity.
This is of course an advantage, because the ease of
movement of the interdental brush can be improved in
this way. Preferred examples for wire diameters are
0.27 mm instead of 0.30 mm, or even 0.23 mm instead of
0.30 mm.
In conclusion, it may be stated that the invention
makes available an interdental brush with a small
diameter of the filament support and, consequently,
good ease of movement in the narrow spaces between the
teeth. Even in the case of fine wire diameters, the
interdental brush is highly robust.
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List of refer~ace labels
la, lb wire sections
2 filaments
B width
D diameter
