Note: Descriptions are shown in the official language in which they were submitted.
10~54~3
This invention relates to dentifrices and to a process for pre-
paring them.
Conventional dentifrices used in the daily brushing and cleaning
of teeth heretofore have not provided the desired degree of polishing action.
This has been largely due to the difficulty in selecting suitable abrasives
which will afford maximum removal of difficult stains and debris without
damaging the enamel surfaces of the teeth. It is consequently desirable to
formulate a composition which not only cleans teeth but also polishes teeth
to a high lustre, for aesthetic reasons as well as for oral hygiene. Highly
polished tooth surfaces appear to be less receptive to the retention of
plaque and oral debris.
The polishing of teeth occurs when an abrasive planes off irregul-
arities of the enamel tooth surfaces, the resulting smooth surfaces appearing
highly polished.
The function of an abrasive substance in dentifrices is to remove
various deposits, including pellicle film from the surface of the teeth.
Pellicle film is a tightly adherent film which often contains brown or yellow
pigments and imparts an unsightly appearance to the teeth. A typical
abrasive material for incorporation into a dentifrice is calcium pyrophos-
phate, but it can cause abrasion of the hard tooth tissues.
Most commercial dentifrices presently on the market have an
REA value of up to about 300, and as low as 50. Calcium pyrophosphate
abrasive commonly can provide dentifrices in which it is incorporated with
an REA value as high as 450 or more. Even when the REA value is lower than
400, it is desirable to ameliorate the enamel abrasivity of calcium
pyrophosphate.
The radioactive enamel abrasion value ~REA value) and radioactivedentin abrasion value (RDA value) referred to herein are ascertained by the
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following techniques.
RDA and REA values are obtained by first irradiating extracted
teeth in a neutron flux to make them radioactive and then brushing the
dentin or enamel surface of the tooth under standard conditions of brushing
and determining the radioactivity of the slurry surrounding the teeth after
their removal.
The RDA values are determined using the dentin portions separated
from human cuspids and subjecting the said dentin to 1000 reciprocal brush
strokes. This radioactive technique is more fully described in the liera-
ture; Stookey, C. K. and Muhler, J. C., J. Dental Research 47 524-538 (1968).
Similarly to the REA values, the RDA value must not be high, in order to
prevent or minimize oral hard tissue damage.
According to the invention a dentifrice possessing superior polish-
ing action without undue enamel abrasivity comprises from 7.5% to 75% by
weight of calcium pyrophosphate having a mean particle diameter in the range
from 1 to 15 microns and which has been pretreated with a non-toxic zinc com-
pound in an amount to provide at least 0.0065% by weight zinc to the dentifrice,
the amount of the zinc compound in the dentifrice being up to 1% by weight,
to reduce enamel abrasivity.
Zinc compounds which have been found to be particularly effective
in reducing the REA value include zinc oxide, zinc sulphate, zinc chloride,
and mixtures thereof, in amounts from as low as 0.01% up to 1% by weight of
the total denti-frice. Although the zinc compounds substantially reduce
enamel abrasion, they have li~tle effect on dentin abrasion.
The preferred particle size range of the calcium pyrophosphate
is from 2 to 10 microns.
The particle diameters given are determined by conventional methods.
Thus, the standard liquid sedimentation technique may be used. The calcula-
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lO~S4Z3
tion of particle diameter from the sedimentation data being made (as is
conventional) on the basis of Stokes' Law, disregarding the particular shape
of the particles.
The proportion of calcium pyrophosphate in the dentifrice is at
least 7.5% and not more than 75% for instance, in the range from 20% to 75%
preferably from 40% to 50%, such as about 40%. These and other proportions
given herein are by weight of the dentifrice, unless otherwise specified.
Parts are by weight.
As well as calcium pyrophosphate, an additional dental abrasive
may be included which is softer in abrasiveness on enamel. The additional
soft abrasive may be, for instance, any of those conventionally employed
in toothpastes, such as hydrated alumina, anhydrous dicalcium phosphate,
insoluble sodium metaphosphate, dicalcium phosphate dihydrate, calcium
carbonate, silica xerogels of the high density or intermediate density types
~such as those sold under the designation "Syloid 63" or "Syloid 72" or
"Syloid 74" - Syloid is a trade mark), alkali metal or alkaline earth metal
aluminosilicates (such as those having a refractive index in the range from
1.44 to 1.47 and containing at least 70% by weight of silica, up to 10% by
weight of alumina, up to 20% by weight of moisture and up to 10% by weight
of sodium oxide, the moisture content preferably being in the range from 10
to 20% by weight measured by loss at 1000C, and the typical content of
sodium oxide being in the range from 5 to 10% by weight), kappa-alumina (such
as described in United States patent 3,003,919); synthetic resins ~such as
described in British patent specification 995,351); composite abrasive
particles in which a hard mineral is coated with, or embedded in, a synthetic
resin (the mineral being, for instance, crystalline silica, e.g. quartz, grit
(SiC), anhydrous alumina, haematite, or zirconium silicate, and the coating
being, for instance, an impervious cross-kinked thermoset synthetic resin such
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as melamine-formaldehydes, urea-formaldehyde, phenol-formaldehyde or epoxy
resins, or polymers or copolymers of compo~mds having two or more polymeriz-
able ethylenically unsaturated groups e.g. diallyl phthalate polymers, such
as described in United States patent 3,151,027).
The soft dental abrasive may have a particle size in the range from
2 to 40 microns and may be present in the form of relatively large agglomerates
(of the individual particles) of such size as to be visible to the naked
eye but easily reduced to the fine impalpable particle size upon being sub-
jected to toothbrushing in the mouth. Such agglomerates may be agglomerated
with or without a binding agent, which may be water-soluble or water-insoluble.
For most purposes it is preferable that the soft dental abrasive
has a particle size of less than 20 microns to avoid any gritty feel.
The proportion of such soft additional dental abrasive in the
dentifrice is usually in the range from 10% to 50%, and is preferably such
that when calcium pyrophosphate is omitted from the dentifrice, the RDA value
is in the range from 100 to 600, preferably from 100 or 200 to 450. Typically,
this proportion of dental abrasive is in the range from 5% to 70% of the
dentifrice, such as 10% to 50%.
To make toothpastes or dental creams, the calcium pyrophosphate
abrasive, pretreated with the zinc compound, and any other dental abrasive
which may be present are dispersed in a dental vehicle which preferably con-
tains a liquid which is water and/or a humectant such as glycerine, sorbitol,
propylene glycol or polyethylene glycol 400, including suitable mixtures
thereof. It is usually advantageous to use a mixture of water and one or two
humectants. Polyethylene glycols of higher moecular weight, e.g., polyethylene
glycol 600, may also be present. The total liquid content is generally well
over 20% by weight of the vehicle (sorbitol, generally present in admixture
with water, is considered as a liquid for this purpcse). The preferred hum-
10~;423~
ectants are glylcenine and sorbitol. Typically, the vehicle contains 0 to
80% of water.
To pretreat the calcium pyrophosphate with a water-soluble zinc com-
pound such as zinc chloride or æinc sulphate, the water-soluble zinc compound
is preferably dissolved in an aqueous solution and stirred with the calcium
pyrophosphate, or with the calcium pyrophosphate and the soft abrasive,
if both are used in the dentifrice. The solids are then isolated and washed
with water. The pretreated abrasive is then incorporated into a dental
vehicle.
In the case of an insoluble zinc compound, such as zinc oxide, the
calcium pyrophosphate is pretreated by mixing it with the zinc oxide prior
to incorporation in the dentifrice. The reduction in enamel abrasiveness is
the result of the pretreatment of the calcium pyrophoshate by the zinc com-
pound. When the calcium pyrophosphate is pretreated with zinc chloride
or zinc sulphate substantially similar large reductions in enamèl abrasivity
of the finished dentifrices are observed with varying concentrations of zinc
in the dentifrices. When the abrasives and the zinc compound, particularly
zinc oxide, are first mixed together to pretreat the abrasive with the zinc
compound before being incorporated into the dentifrices, redllctions in
enamel abrasivity are increased with greater concentrations of zinc in the
dentifrices.
The vehicle usually also contains a thickening or gelling agent,
such as a natural or synthetic gum or gum-like material, such as Irish Moss~
gum tragacanth, alkali metal ~e.g. lithium, potassium or sodium) carboxy-
methyl cellulose and hydroxymethyl carboxyethyl cellulose, polyvinyl pyrroIi-
done, starch, water-soluble hydrophilic colloidal carboxyvinyl polymers
such as those sold under the designations "Carbopol 934" and "Carbopol 940"-
Carbopol is a trade mark hydroxyethyl cellulose, Indian gum, acacia gum, agar
10~?~42~
agar, locust bean gum, "Laponite CP" or "Laponite SP", which are synthetic
inorganic complex silicate clays - Laponite is a trade mark, and pectin,
or inorganic thickeners such as colloidal silica, e.g. synthetic finely divided
silicas including those sold under the designations "Cab-O-Sil M5", "Syloid
244", "Syloid 266", and "Aerosil D200" - Cabosil, Syloid and Aerosil are
trade marks. The solid portion of the vehicle is typically present in an
amount up to 10% by weight of the toothpaste and preferably in the range from
0.5 to 8% by weight.
Fine particles of thermoplastic resign may also be present, such
as particles of solid polymer having a molecular weight above 100 (preferably
above 10,000, e.g. about 10,000 to lOO,OOO or more) and a mean diameter less
than 50 microns (preferably in the range from 0.5 to 50 microns, e.g. 10 to
30 microns). The polymer particles may be prepared directly by emulsion
or suspension polymerization or by grinding the polymer in bulk, and may be
present in amount of up to 60% or more by weight of the dentifrice, e.g. in
the range from 20 to 60%, such as 20 to 50%, for instance 30 to 50% in a
toothpaste. Examples of thermoplastic resins are polymerized ethylenically
unsaturated compounds, such as polyolefines (e.g. polyethylene or polypropy-
lene); vinyl or vinylidene resins such as polyvinyl chloride, polystyrene,
vinyl chloride-vinyl acetate copolymers, styrenebutadiene copolymers and
polyvinylidene chloride; polylamides such as Nylon ~e.g. Nylon 6); and cell-
ulosics such as cellulose acetate.
The dentifrice may also contain a surface-active agent, e.g. to
achieve increased prophylactic action, and to assist in achieving thorough
and complete dispersion of the dentifrice throughout the oral cavity. The
surface-active agent may be anionic, nonionic, ampholytic or cationic in
nature, and its agent a detersive material which imparts to the composition
detersive and foaming properties. Suitable types of such detergents are
10!?~423
water-soluble salts of higher fatty acid monoglyceride monosulphates, such
as sodium salt of the monosulphated monoglyceride or hydrogenated coconut
oil fatty acids, higher alkyl sulphates such as sodium lauryl sulphate, alkyl
aryl sulphonates, such as sodium dodecyl benzene sulphonate, higher alkyl
sulphoacetates, higher fatty acid ester of 1, 2 hydroxy propane sulphonates,
and substantially saturated higher aliphatic acyl amides of lower aliphatic
amino carboxylic acid compounds, having 12 to 16 carbons in the higher fatty
acid, alkyl or acyl radicals. Examples of the last-mentioned amides are
N-lauroyl sarcosine, and the sodium, potassium and ethanolamine salts of
N-lauroyl, N-myristoyl or N-palmitoyl sarcosinates, which should be substant-
ially free from soap or similar higher fatty acid material which tends to
substantially reduce the effect of these compounds. The use of these sar-
cosinate compounds in dentifrices ofthe present invention is particularly
advantageous since these materials exhibit a prolonged and marked effect
in the inhibition of acid in the oral cavity due to carbohydrates, in
addition to exerting some reduction in the solubility of tooth enamel in acid
solutions.
Other suitable surface-active materials include nonionic agents
such as condensates of sorpitan monostearate with approximately 60 moles
of ethylene oxide, condensates of ethylene oxide with propylene oxide conden-
sates of propylene glycol ("Pluronics" - Pluronic is a trade mark) and cationic
surface-active germicides and antibacterial compounds such as di-isobutylphen-.
oxyethyldimethyl - dimethylbenzyl ammonium chloride, benzyl dimethyl stearyl
ammonium chloride, tertiary amines having one fatty alkyl group (of from 12 to
18 carbon atoms) and two (poly) oxyethylene groups attached to the nitrogen
~typically containing a total of from 2 to 50 ethenoxy groups per molecule)
and salts thereof with acids, and compounds of the structure:
~0~542;~
~CH2cH2o~zH (CH2CH20)xH
R - N CH2 CH2CH2CH2N
(cH2cH2o)yH
where R is a fatty alkyl group containing from 12 to 18 carbon atoms, and
x, y and z total 3 or higher, as well as salts thereof with mineral organic
acids, may also be used. It is preferred that the total amount of surface-
active agents be at least 0.05% by weight, preferably 1 to 3%, by weight of
the dentifrice.
Various other adjuvant materials may be incorporated in the denti-
frices of this invention. Examples thereof are colouring or whitening agents
such as titanium doixide, preservatives, silicones, chlorophylcompounds,
ammoniated materials such as urea and diammoniumphosphate, and mixtures
thereof. Each of these adjuvants typically may be incorporated in the
dentifrices in amounts up to 5%.
The dentifrices may also contain antibacterial agents, generally
in amounts in the range from 0.01 to 5% by weight. Typical examples
of such agents are guanidines, biguanides and amines such as: -
Nl _ (4 - chlorobenzyl) - N5 - 2,4 - ~dichlorobenzyl) biguanides;
p - chlorophenyl biguanide;
4 - chlorobenzhydrylbiguan~de;
4 - chlorobenzhydarylguanylurea;
Nl - 3 - lauroxypropyl _ N5 - p - chlorobenzyl biguanide;
1,6 - di - p - chlorophenylbiguanidohexane;
1 - (lauryldimethylammonium) - 8 - tp - chlorobenzyldimethyl - ammonium)
octane dichloride;
5,6 - dichloro - 2 - guanidinobenzimidazole;
Nl _ p - chlorophenyl - N5 - laurylbiguanide;
5 - amino - 1j3 - bis(2 - ethylhexyl) - 5-- methylhexahydropyrimidine;
and their non-toxic acid addition salts.
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Suitable flavouring and sweetening agents may be employed in
formulating a flavour for the dentifrice of the invention. Examples of
suitable flavouring constituents include flavour-oils, e.g. oils of spear-
mint, peppermint, winter-green, sassafras, clove, sage, eucalyptus, marjoram,
cinnamon, lemon and orange, and methyl salicylate. Suitable sweetening
agents include sucrose, lactose, maltose, sorbitol and saccharin. Suitably,
flavour and sweetening agent may together constitute from 0.01 to 5% or
more of the dentifrice. Preferably the amount of flavouring oil is above
0.5% and below 2%. Strongly flavoured toothpastes contain above 1% of
flavouring oil, e.g. 1.2 to 1.5%.
The dentifrices of the invention may also include a fluorine-con-
taining compound having a beneficial effect on the care and hygiene of the
oral cavity, e.g. diminution of enamel solubility in acid and protection
of the teeth against decay. Examples thereof include sodium flouride,
stannous fluoride
~SnF2.KF),
sodium hexafluorostannate, stannous chlorofluoride, sodium fluorozirconate
and sodium monofluorophosphate. These materials, which dissociate or release
fluorine-containing ions in water, may be present in an effective but non-
toxic amount, usually in the range from 0.01 to 1% by weight of the dentifrice,
calculated on the water-soluble fluorine content thereof.
The pH of the dentifrices is generally in the range of from 4
to 10, e.g. from 5 to 8.
The dentifrice may be prepared by suitably mixing the ingredients.
For instance, in making a toothpaste, a gelling agent such as sodium car-
boxymethyl cellulose or "Carbopol 934" and a preservative such as sodium
benzoate, if employed, is dispersed with a humectant such as glycerine. Water
may also be present. Additional humectant and water, e.g. as an aqueous 70%
_g_
~09542~
sorbitol solution, may then be mixed with the dispersion and a paste, gel
or cream formed. The pretreated calcium pyrophosphate and other abrasive,
if any, surface-active agent and flavour are then added. The toothpaste
is then thorughly deaerated ~e.g. in vacuo) and packed in tubes.
Dentifrices embodying the invention have been found useful as
prophylactic dental pastes to be applied professionally, preparations for use
on dentures and preparations for daily use on the teeth.
The following Example illustrates the invention.
EXAMP LE
A toothpaste of the following formulation is prepared and by
analysis is observed to have an REA value of 278 and an RDA value of 398.
Ingredients Parts by
weight
Glycerine 9.8
Sorbitol 11.9
Sodium carboxymethyl cellulose 1.4
Sodium silicate 0.3
Water 30-5
Calcium pyrophosphate 40.1
Sodium lauryl sulphate 0.8
Sodium coco-monoglyceride sulphonate 1.3
Stannous fluoride 0.4
Stannous pyrophosphate 1.0
When 0.4 parts by weight of zinc oxide are used to pretreat ~he cal-
cium pyrophosphate by mixing these two compounds together before mixing them
with the other ingredients of the toothpaste the REA value is substantially
reduced.
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