Note: Descriptions are shown in the official language in which they were submitted.
Thls inventio~ a~es to a dentifrics and
in particular to a dentifrice containing an abrasive
having its abrasivity reduced b~ the addition of
certain particulate materials.
A basic requlrement of an effective denti-
frice is that it should clean the teeth by
reduc:ng the amount of, or removing9 deposits
of food debris, acquired pellicle, plaque and cal-
culus~ Accordingly, a satisfactory dentifrice
always includes an abrasive agent. The abrasive
agent must remove these dental deposits without
excessively abrading the underlying tooth material,
namely the tooth enamel and dentine. The abrasi-
vity of a particular cleaning agent is governed
by phy~ical propert~es SUC}l as size, shape, strength
and brittleness, in addition to hardness. Denti-
frice abrasives are chosen with combinations of
the~e properties ~hich result in the abrasion
necessary for the cleaning process, with the min-
imum abrasion of the tooth surface.
Price is second i~portant factor in the choice
of a dentifrice abrasive. Thus, fine modifications
of the physical properties of abrasive agents are
unacceptable as they produce dentifrice compositions
which are too expensive to be practical. For ex-
ample calcium carbonate, a commonly u~ed abrasive
is readily available is inexpensive and a suitable
basic abrasive to be widely used in toothpastes.
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10428~3
It is obtainable in different grades varying in
crystalline form, particle size, surface area, and
density. Its abrasive and cleaning properties can
be modified by blending different grades or mixing
with other abrasive materials such as phosphates,
but in general such methods of modifying cheap
materials like calcium carbonate, however, lead
to a very much more expensive product.
This invention is based on the discovery that
the abrasivity of a coarse grade of calcium car-
bonate drops dramatically when a surprisingly
small quantity of water-insoluble particulate
organic polymer which is less abras~ve and of
lower average density than the calcium carbonate
is added. The addition of such small quantities
of polymer has the added benefit of reducing the
scratch dept~ on dental enamel and hence improving
the polishing effect of the calcium carbonate on
teeth.
The present invention therefore provides a
dentifrice composition comprising a cleaning agent
which consists of from 75-99.9~ by weight of calcium
carbonate and from 0.1-25% by weight of a water-in-
soluble particulate polymeric material which is
(a) less abrasive and (b) of lower average density
than said calcium carbonate.
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The polymsric materials suitable for this
invention are o~ relatively lower abrasivity than
the calcium carbonate, as measured by the taly
surf method (see British Dental Journal Vol 13~,
No.2, pp 60-66, July 1972). In addition it is
preferred that the polymeric material has a Moh~s
hardness of 3 or less.
Preferred polymeric materials are thermo-
plastic resins, that is those which can be melted
and resolidified without losing their original
properties. The properties of such resins, being
of relatively low hardness and rigidity, make them
inef~ective alone as cleaning agents in ~enti-
frices, but ideal for the purposes of the present
lnvention. ~xamples of suitable thermoplastic
resins include acrylics such as polymethyl metn-
racrylate ~nd polyisobutyl methacrylate" cellu-
loBiCS such as acetates and butyrate, polyamides,
polyethylene, polypropylene, polystyrene, vinyls
such as polyvinyl chloride and co-polymers of
polyvinylchloride and polyvinyl alcohol.
Preferred materials are ~olymethyl methacry-
late and polystyrene.
Such polymeric materials are present in the
dentifrice in particulate form, i.e. the polymer
is present as discret~ pa~ticle~ not dissolved in
the body of the toothpaste and not substantially
agglomerated. The particles may be solid or composed
of a lattice of material, or may be hollow. ~Iollow
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particles or particles having cavities are par-
ticularly preferred as such structures provide a
less dense material. Preferred materials are
based on polystyrene or polymethymethacrylate.
The particles of polymeric material should
preferably hava a weight median diameter of not
greater than 100 microns. The weight median ~ -
diameter (W.M.D.) is that particle diameter
above which 50S~ by weight occur. The limit
,. :.,
of 100~ for the t~MD ensures that the particles
do not impart a noticably gritty taste to the
dentifrices. A preferred W.M.D. for the part-
icles is in the range of 0.01-50~.
The shape of the polymer particles is not ,
critical for the reduction of abrasivity of the '
calcium carbonate. Thus, spherical polymer part-
icles or irregular granules are equally as effective
in this respect.
This invention i~ particularly use~ul for ,'
coar~er, cheap forms of calcium carbonate which have
exceptionally good cleaning power, and low abrasivity
with respect to en~mel.
A further benefit is derived from the in-
corporation of polymer in calcium carbonate denti-
frice,which contain fluoride,either as fluorophos- -~
phate or as fluoride ion. It is well known that
fluorophosphate or ~luoride co~plexes with calcium
carbonate, thereby reducing the available fluoride
activity. Our own data indicates that when calcium
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104Z803 `
carbonate plus 25% or less o~ polymer particle~
is used as the abrasive agent in a fluor~de d~ntI-
frice, the fluoride activ$ty is enhanced relati~e
to the ~ame dentifrice containing calcium carbon-
ats alone as the abrasive.
To illustrate the invention, the accompanying
Fig 1 shows in graphical ~orm the abrasivity
measurements of toothpaste compositionscontaining
various proportions of waterworks ch~lk (W.M.D.-
15~.m.), In Fig l, the ordinate represents the
abrasivity o~ the mixture measured on an arbltrary
scale [taklng a~ 100% standard the abrasivity of
the cleaning agent present in the toothpaste
sold in the United Kingdom under the name "Macleans
Freshmint~].
The abscissa of Fig l represents the percentage
by weight of the waterworks chalk in the mlxture.
The line A shows the abrasivity variation
for mixtures by welght of waterworks chalk and a
precipitated calcium carbonate having a WMD of 4~.
The 4~ chalk u~ed in this test was supplied by
Sturge Ltd, under the name "Sturcal F" and ha~ a
density of 2.7g/cc. Thus lt can be seen that the
repl~cement in a cleaning agent by Sturcal F of
waterworks chalk causes a gradual reduction in the
abrasi~lty. In order to produce a mixture havir,g
an abrasivlty of lOO on this scale, a 50:50 mixture
of Sturcal F to waterworks rh~lk is required.
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104Z8~3
The curve B shows the abrasivity ~ariat~on
for mixtures of waterworks chalk and polymethyl
methacrylate, a polymeric material used in accord-
.
ance with this invention, on a weight basis. Thepolymer was supplied by I.C.I. as DV 400 grade
powder and had a W.M.D. of 40~ and a density of
1 . lg/cc .
The abrasivities for the waterworks
chalk/methacylate mixtures were tested on 6 dentine .
specimens by the Talysurf technique and the 1:
numerical results are shown in Table 1.
TABLE 1
% Chalk in Chalk/Acrylic Blend I Abrasivity as ~ Fre~hmlnt
I t
Gravimetric ¦ Volumetric ~ Mean + S.D. ~ Median
_ - I i
100 100 ~ 142 + 16 ~ 138 :
106 + 33 : 99
44 60 + 29 55
i 23 + 12 1 18
12.5 13 + 7 1 11
3.5 3 ~ 2 t 3 .
0 0 5 + 3 ~ 5
.,
10428Q3
It will be seen from Fig 1 that the substitution
of small proportions by weight of 40~ T~.M.Do
polymethyl methacrylate for waterworks chalk
produces large reductions in abrasivity. Thus
an abrasivity of 100 is achieved with a mixture
only 10% of methacrylate to O~S of waterworks
chalk.
The reason for this dramatic effect is
illustrated by the line C which represents mixture
of waterworks chalk and methacrylate measured
in ter~s of their proportions by volume. This
shows a linear decrease in abrasivity as a given
volume of chalk is replaced by that volume of
polymer.
From these results it can be seen that
inorder to obtain a curve of the type B, giving
a large initial reduction in abrasivity for a
small proportion by weij~ht of polymer, the poly-
mer must:-
(a) have a low abrasivity so that the abrasivity
at intercept Y is much lower than the initial
abrasivity X; and
(b) have a lower density than the chalk so that
a small percentage by weight will occupy a large
percentage by volume of the mixture.
In a separate experiment, abrasivities
were compared of mixtures containing waterworks
chalk and another polymer in accordance with this
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invention, viz. that sold under the name "Ponty-
bond" (Pontyclun Chemical Co. Ltd.). The material
used in this test, Pontybond 2150, has a W.M.D.
of about 15~. The particles are colourless,
homogeneous spheres, are chemically inert but
capable of absorbing small quantities of ali- ~
phatic liquids and rather larger amounts of -
aromatic liquids. Pontybond has a true density
of 1.005. The abrasivity results are shown in
Table 2 and graphically in ~ig 2.
TABLE 2
~ , , .
ADrasivlty as 5~ Freshmint ~ -
% Waterworks Chalk _
in blend by Weight Mean + S.D. Median j
.. . .. . ... '
100.0 131 - 6 130 ``
87.5 103 + 16 98 ?
75.0 ! 80 + 7 78
50.0 ! 50 + 6 49
~ .
25.0 j 20 + 7 20
- C 2 + 1 2 -~
These results demonstrate that by blending
the 15~ Pontybond material with waterworks chalk,
it is again possible to dramatically reduce the
abrasivity.
The method of reducing the abrasivity of a
dentifrice cleaning agent by the means descrlbed
in this specification appears to be due to the fact
that the polymeric material, occupies a large prop-
~aJc ~narl(
1042BQ3ortion (compared to its weight) of the active vol-
ume of the dentifrice from which the abrasive chalk
particles can be used. The action of the highly
abrasive particles is thereby hindered. It is9
however, not merely a dilution effect, caused
by there being proportionally less abrasive per
unit volume when abrasive is replaced by polymer.
This is proved by the curve D on Fig 1 which rep-
resents the variation of abrasivity of the denti-
frice caused by the mere removal of the water~orks
chalk from the dentifrlce, so that the weight of
abrasive per unit volume is gradually decreased.
No other abrasive or polymer is added to replace
it. It can be seen that there is a very slow
reduction in abrasivity until most of the chalk
has been removed. A similar effect is observed
if the chalk is replaced by a corresponding weight
of water.
~ The dentifrices of this invention may be in
any desired form, for example, pastes, liquids,gels,
ointments, emulsions, powders, tablets, dragees or
chewing gum, and comprise the additional ingred-
ients conventionally incorporated in such prep-
arations, mus a toothpaste; for instance, will
usually comprise, in addition to the abrasive
material as cleaning agent, a detergent, humectant,
binding agent, flavouring agent preservatives and
colou~r and sometimes a fluoride material such as
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1042803
stannous fluoride, ammonium fluoride or sodium
monofluorophosphate.
Commonly used dental detergents include
sodium lauryl sulphate, sodium N-lauroyl sarcosinate
and ricinoleate and sulphoricinoleate derivati~es.
Suitable humectants include glycerol and
sor~itol and also other polyalcohols such as
propanediol and/or butanediol.
Binding agents are also required in tooth- ;
pastes to prevent separation of ingredients on
storage. Such materials are, for example gum
tragacanth, sodium carragheenate, cellulose
derivatives such as carboxymethyl cellulose and -
cellulose ethers, polyacrylic acid and polyvinyl~
pyrrolidone.
The dentifrice may also contain the con-
~entional fla~ouring and swee~ening, substances
such as peppermint or spearmint oil, menthol or
oils of clove, wintergreen, eucalyptus, aniseed,
rose, lavander; saccharin and sodium cyclamate.
Examples of preservatives which may be in-
corporated into the dentifrice include p-hydroxy- .
benzaic acid esters; hexachlorophen; and known
surfactants.
If desired colour may be imparted to the
dentifrice by means of dyestuffs; or bleaches or
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1~)4Z~3
optical brigh;eners may be incorporated, such
as sodium perborate, magnesium peroxide, hydrogen
peroxide - urea compounds.
The invention is illustrated by the following
Examples of toothpaste for.mulations containing
abrasive materials according to the invention:
EXAMPLE 1 % w/w
Glycerin 3-00
Sodium Carboxy Methyl Cellulose 1.1
Sodium Saccharin 0.4
Calcium Carbonate (~n~D 10-15 microns) 45.0
Polymethyl methacrylate Granule~ DV400 5.0
(WMD 40 m~crons)
Sodium Lauryl Sulphate 1.5
Flavour q.s.
Water to 100.00
EXAMPLE_2 % w/w
Glycerin 30.00
Sodium Carboxy Methyl Cellulo~e 0.95
Calcium Carbonate (I~MD 10-15 microns) 35.00
Polymethyl ~ethacrylate Granules DV400 15.00
(WMD 40 microns)
Sodium Lauryl Sulphate 1.5
Flavour q.s.
Sodium Saccharin q.s.
Water to 100.00
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