Drug – bio-affecting and body treating compositions – Dentifrices
Reexamination Certificate
2001-03-16
2003-02-11
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
C424S052000, C424S057000
Reexamination Certificate
active
06517815
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a dentifrice in the form of a water-containing, paste-form or liquid cream containing 10 to 30% by weight of a combination of polishing agents and 20 to 50% by weight of a humectant,of which the cleaning performance has been further improved by an addition of condensed phosphates
Toothpastes are used in the daily cleaning of teeth by brushing with a toothbrush. Toothpastes are intended above all to support the removal from the tooth surfaces of food remains, discoloration, for example by tobacco or tea, and firmly adhering bacterial films, so-called plaque. This is mainly done by the polishing agents present in the toothpaste and, to a lesser extent, also by the surfactants present. In order to develop their cleaning and polishing effect, the polishing agents have to have a certain abrasiveness towards the tooth surface. However, it is extremely important that the abrasiveness towards dental enamel and dentin is kept at low levels to avoid damage to the tooth surface by the daily use of the toothpastes. Above all, the polishing agents used should not cause any deep scratches on the tooth surface. On the contrary, they should have a smoothing effect on any roughness present in the tooth surface.
Condensed phosphates are known from numerous publications as scale inhibitors and as demineralization inhibitors in dentifrices.
The cleaning effect of water-soluble pyrophosphate salts on teeth discolored by tea and coffee is also known from U.S. Pat. No. 4,822,599 A.
Dentifrices containing an abrasive mixture of a silica polishing agent and a calcined aluminium oxide are known as particularly effective tooth cleaning preparations from DE 27 58 548 C2. This document recommends the addition of certain inorganic electrolyte salts to prevent abrasion of the dental enamel. In spite of this, extremely high dentin abrasion values (RDA) and enamel abrasion values (REA) of 300 to 500 were obtained.
Although the abrasion values can be reduced by reducing or omitting the aluminium oxide polishing agent, cleaning performance is significantly impaired at the same time. Accordingly, there was a need to develop a dentifrice which would combine very low abrasiveness (RDA and REA values below 100) with a very good cleaning effect (CRS values of around 100).
DE 34 25 152 describes a combination of polishing agents consisting of a silica polishing agent and a lightly calcined aluminium oxide with which reduced abrasiveness can be combined with a good cleaning effect.
It has now been found that condensed phosphates are ideally suitable for increasing the cleaning performance of toothpastes containing a combination of silica polishing agents and aluminium oxide polishing agents to such an extent that the need stated above is satisfied without any significant increase in the abrasion values.
Accordingly, the present invention relates to dentifrices in the form of water-containing, paste-form or liquid dispersions containing 10 to 30% by weight of a combination of silica polishing agents and aluminium oxide in a ratio by weight of 10:(0.2-2) and 20 to 50% by weight of a humectant from the group consisting of sorbitol, glycerol, 1,2-propylene glycol or mixtures thereof, characterized in that they contain a condensed phosphate from the group consisting of tripolyphosphate, pyrophosphate, trimetaphosphate or mixtures thereof in the form of the alkali metal or ammonium salts in a quantity of 2 to 12% by weight in order to increase the cleaning effect.
Suitable silica polishing agents are, for example, silica gels which are obtained by reacting sodium silicate solutions with strong aqueous mineral acids to form a hydrosol, ageing the hydrosol to form the hydrogel, washing and drying. If drying is carried out under moderate conditions to water contents of 15 to 35% by weight, so-called hydrogel silicas, which are known for example from U.S. Pat. No. 4,153,680, are obtained.
Drying to water contents below 15% by weight results in irreversible shrinkage of the previously loose structure of the hydrogel to the dense structure of the so-called xerogel. Xerogel silicas are described, for example, in U.S. 3,538,230.
A second preferred group of silica polishing agents are the precipitated silicas. Precipitated silicas are obtained by precipitation of silica from dilute alkali metal silicate solutions by addition of strong acids under conditions where aggregation to the sol and gel cannot occur. Suitable processes for the production of precipitated silicas are described, for example, in DE-OS 25 22 486 and in DE-OS 31 14 493. Preferred precipitated silicas are, for example, those which have a mean particle size of 5 to 20 &mgr;m, a sieve residue (45 &mgr;m) of less than 1% by weight and a specific surface (BET) of 100 to 300 m
2
/g.
By virtue of the special combination of polishing agents, the dentifrices according to the invention have an excellent cleaning effect, even against discoloration of the teeth by tea and nicotine. At the same time, a good polishing effect (smoothing of roughness) is obtained despite only moderate dentin and enamel abrasion. In spite of the presence of a relatively hard polishing component, namely aluminium oxide, the dentifrices according to the invention have hardly any scratching effect.
A preferred aluminium oxide polish is a lightly calcined alumina with a content of at least 10% by weight of &agr;-aluminium oxide of various so-called &ggr;-aluminium oxide modifications.
Suitable lightly calcined aluminas are prepared by calcination from aluminium hydroxide. Aluminium hydroxide is converted by calcination into &agr;-Al
2
O
3
which is thermodynamically stable at temperatures above 1200° C. The thermodynamically unstable Al
2
O
3
modifications occurring at temperatures of 400 to 1000° C are known as &ggr;-forms (cf. Ullmann, Enzyclopädie der technischen Chemie, 4th Edition (1974), Vol. 7, page 298). The degree of calcination, i.e. the conversion into the thermodynamically stable &agr;-Al
2
O
3
, can be adjusted as required through the choice of the temperature and the duration of the calcination process. Light calcination gives an alumina with a &ggr;-Al
2
O
3
content which is lower, the higher the calcination temperature and the longer the calcination time. Lightly calcined aluminas differ from pure &agr;-Al
2
O
3
in the lower hardness of the agglomerates, in a larger specific surface and larger pore volumes.
The dentin abrasion (RDA) of the relatively lightly calcined aluminas to be used in accordance with the invention containing 10 to 50% by weight of &ggr;-Al
2
O
3
is only 30 to 60% of the dentin abrasion of a heavily calcined, pure &agr;-Al
2
O
3
(as measured in a standard toothpaste containing 20% by weight alumina as sole polishing agent).
In contrast to &agr;-Al
2
O
3
, &ggr;-Al
2
O
3
can be dyed red with an aqueous-ammoniacal solution of Alizarin S (1,2-dihydroxy-9,10-anthraquinone-4-sulfonic acid). The degree of dyeability can be used as a measure of the degree of calcination or rather the percentage content of &dgr;-Al
2
O
3
in a calcined alumina:
Ca. 1 g Al
2
O
3
, 10 ml of a solution of 2 g/l Alizarin S in water and 3 drops of an aqueous 10% by weight solution of NH
3
are introduced into a test tube and briefly boiled. The Al
2
O
3
is then filtered off, washed, dried and examined under a microscope or evaluated by colorimetry.
Suitable lightly calcined aluminas containing 10 to 50% by weight &ggr;-Al
2
O
3
can be colored pale to deep pink by this method.
Aluminium oxide polishing agents with various degrees of calcination, fineness and bulk densities are commercially obtainable, for example the “Poliertonerden (polishing aluminas)” of Giulini-Chemie and ALCOA.
A particularly suitable quality “Poliertonerde P10 feinst” has an agglomerate size below 20 &mgr;m, a mean primary crystal size of 0.5 to 1.5 &mgr;m and a bulk density of 500 to 600 g/l.
Sorbitol, xylitol, glycerol, propylene glycol or mixtures of these polyols may be present as humectants. Polyethylene glycols with molecular weights of 400 to 2000 may als
Leinen Hans-Theo
Wuelknitz Peter
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Murphy Glenn E. J.
Rose Shep K.
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