Dentifrice for hypersensitive teeth

A dentifrice for hypersensitive teeth containing at least 15% by weight of an apatite having an average particle size of less than 8 .mu.m and an abrasion value (RDA) of less than 30 as the sole crystalline and polishing substance. No further soluble mineral salts are present in the dentifrice. The dentifrice may also contain a local anesthetic.

BACKGROUND OF THE INVENTION 
The present invention relates to a dentifrice for hypersensitive teeth 
containing an apatite having an average particle size of less than 10 
.mu.m and, optionally, a local anesthetic. 
DESCRIPTION OF THE PRIOR ART 
German Patent Specification No. 21 34 862 describes dentifrices for 
hypersensitive teeth. However, the dentifrice recipes additionally 
contained an osmotically effective salt combination comprising sodium 
hydrogencarbonate, sodium chloride, magnesium carbonate, magnesium 
chloride, potassium sulfate, etc. 
U.S. Pat. No. 3,122,483 discloses adding strontium chloride to dentifrices, 
since this substance is believed to influence the stimulus conduction in 
the pulp. From the view of dental medicine influencing the pulp is hardly 
desired and may involve other negative consequences. 
A further means for treating hypersensitivities is by local application of 
amine fluoride solutions. However, this treatment has the drawback of that 
it can only be carried out in the dentist's office and, with conventional 
dental care, will only last for a short time. 
EVENTS LEADING UP TO THE PRESENT INVENTION 
Extensive experimental work directed to improving the commercial product 
described in the German Patent Specification No. 21 34 862 has led to the 
surprising result that the addition of strontium chloride did not improve 
the effect. Rather, it was found that the efficacy could be improved to a 
significant extent by omitting all soluble mineral salts and employing an 
apatite having an average particle size of less than 8 .mu.m as the sole 
crystalline and polishing substance. Moreover, such an apatite has a 
substantially lower abrasion value (measured as RDA; cf. Radioactive 
Dentine Abrasion, J. J. Hefferren, J. Dental Research 55, No. 4,563-573 
(1976)) of less than 30. The amount of the apatite used must be higher 
than that of the commercial product, namely at least 15% by weight instead 
of 9% as used in commercial products to date. 
These results were not foreseeable and also cannot be readily interpreted 
afterwards either. However, the findings suggest that there is some 
polishing effect. Namely, in the course of polishing there is always 
formed a continuous vitreous glossy layer at the tooth surface, which 
layer consists of the base substance of the polished material, on the one 
hand, and of the polishing agent, on the other hand. In the polishing 
procedure these two (the base substance and the polishing agent) are 
closely mechanically attached to each other and fused. Thus, the polishing 
agent is mechanically rubbed in between the microscopic microcrystalline 
to atomic unevennesses and roughnesses of the surface and fused with same 
due to local overheating and formation of an eutectic mixture. If this 
concept is transferred to the tooth surface, then this could mean that by 
treatment with large amounts of the finely-divided apatite, the latter is 
pressed into the exposed small dentin channels. Since the material is the 
same as that of the hard substance of the tooth, the existing damages can 
heal if no interfering alien minerals will inhibit the fusion process. 
Furthermore, the amount of offered apatite must be large enough, and care 
must be taken to prevent the polished surface being torn open again and 
destroyed by other abrasive materials. 
Further investigations have shown that an increased remineralization 
occurs, more specifically so with particle sizes of the apatite of less 
than 4 .mu.m. After 20 applications in vitro, there was already observed a 
reduction in diameter of the dentin channels by about 50%. 
Independently of this subsequent theoretical explanation, it has been 
established that the desired effect is obtained only if all of the 
conditions according to the present invention have been fulfilled. 
SUMMARY OF THE INVENTION 
Thus, it is the object of the present invention to provide a dentifrice for 
hypersensitive teeth containing an apatite having an average particle size 
of less than 10 .mu.m and optionally a loal anesthetic, which dentifrice 
is characterized in that it contains an amount at least 15% by weight of 
an apatite having an average particle size of less than 8 .mu.m and an 
abrasion value (RDA) of less than 30 as the sole crystalline and polishing 
substance, no further soluble mineral salts being present.

DETAILED DESCRIPTION OF THE INVENTION 
The apatite to be used in the present invention may be hydroxylapatite, 
fluoroapatite, or a mixture thereof. It is essential that the amount, 
particle size, and abrasion value will be observed and maintained and that 
no other soluble mineral salts can exert any interfering effect. 
Silicic acid has been proven to be a non-interfering substance which can be 
added in an amount of up to 10% by weight without adversely affecting the 
efficacy of the dentifrice. 
The dentifrices according to the present invention of course may 
additionally contain a local anesthetic such as benzocain, p-aminobenzoic 
acid ethylester. In addition to glycerol and water, the dentifrices 
according to the present invention further contain wetting and foaming 
agents, flavoring agents, and aroma ingredients. If desired, any other 
additive may be used as long as it is not a soluble mineral salt. 
The apatite used in the present invention and having an average particle 
size of less than 8 .mu.m and an abrasion value (RDA) of less than 30 is 
known in the art as so-called amorphous hydroxylapatite, fluoroapatite or 
a mixture thereof. The bulk density of the apatite is preferably less than 
180 g/l and mostly in the range of around 150 g/l. 
The dentifrice according to the present invention is further illustrted by 
the following Example and Comparative Examples and Abrasion Tests. 
EXAMPLE 
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Tooth-paste (Recipe A) 
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Amorphous silicic acid Aerosil 200 
2.40% 
Carboxymethylcellulose 1.00% 
Sodium laurylsulfate 2.75% 
Glycerol (99%) 20.80% 
Wetting agent (Hostapon KTW) 
0.90% 
p-Hydroxybenzoic acid methylester-Na 
0.20% 
Saccharin--Na 0.25% 
Tricalcium hydroxylapatite 
17.00% 
Water 50.699% 
S--Erythrosin 76 E 127 0.001% 
Aroma 1.50% 
Propylene glycol 2.50% 
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The tooth-paste consisting of the above components was subjected to the 
abrasion test (RDA). The abrasion value was found to be 24. 
Clinical examinations of this tooth-paste showed a significant improvement 
already after 3 to 8 days, and all of the users were found to be pain-free 
after 15 days at the latest. 
COMATIVE EXAMPLES 
For comparison, the formulations according to the recipes B through G as 
set forth in the following Table were prepared. 
TABLE 
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B C D E F G 
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Amorphous silicic acid Aerosil 200 
3.00 
2.85 
10.00 
3.00 
2.40 
2.40 
Carboxymethylcellulose 
1.00 
1.00 
1.00 
1.00 
1.00 
1.00 
Sodium larylsulfate 
2.75 
2.75 
2.75 
2.75 
2.75 
2.75 
Glycerol (99%) 20.80 
20.80 
20.80 
20.80 
20.80 
20.80 
Wetting agent (Hostapon KTW) 
0.90 
0.90 
0.90 
0.90 
0.90 
0.90 
p-Hydroxybenzoic acid methylester-Na 
0.20 
0.20 
0.20 
0.20 
0.20 
0.20 
Saccharin--Na 0.25 
0.25 
0.25 
0.25 
0.25 
0.25 
Tricalcium hydroxylapatite 
-- -- -- 9.00 
17.00 
17.00 
Water 49.499 
49.499 
60.99 
49.499 
49.699 
44.699 
S--Erythrosin 76 E 127 
0.001 
0.001 
0.001 
0.001 
0.001 
0.001 
Aroma 1.50 
1.50 
1.50 
1.50 
1.50 
1.50 
Propylene glycol 2.50 
2.375 
2.50 
2.375 
2.50 
2.50 
Potassium sulfate 0.175 
-- -- 0.175 
-- -- 
Magnesium carbonate 
1.25 
-- -- 1.25 
-- -- 
Sodium hydrogencarbonate 
6.25 
-- -- 6.25 
-- -- 
Sodium chloride 0.175 
-- -- 0.175 
-- -- 
Titanium dioxide 0.75 
0.75 
-- 0.75 
-- -- 
Dicalcium phosphate .times. 2 H.sub.2 O 
9.00 
17.00 
-- -- -- -- 
Benzocain -- 0.125 
-- 0.125 
-- -- 
Strontium chloride .times. 6 H.sub.2 O 
-- -- -- -- 6.00 
5.00 
Cetylamine hydrogenfluoride 
-- -- -- -- -- 1.00 
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Recipe E conforms to that of the commercial product of German Patent 
Specification No. 21 34 862. Recipe B conforms to that of the commercial 
product of Recipe E; however, Recipe B does not contain hydroxyl apatite. 
Recipe C conforms to Recipe B, but contains benzocain added thereto. 
Recipe D is a placebo containing no active ingredient at all. Recipes F 
and G conform to Recipe A according to the invention; however they 
additionally contain strontium chloride.times.6H.sub.2 O or cetylamine 
hydrogenfluoride, respectively. 
As a result of the clinical examination, Recipe A (a dentifrice according 
to the present invention) was found to be substantially more efficient 
than the commercial product and some other recipes, although the latter 
were superior to the placebo. 
ABRASION TESTS 
The abrasion values (RDA) were determined of the materials according to 
Recipes A and F and of some known commercial products. It was determined 
that the abrasion value of Recipe F was already 61. The respective values 
for the commercial products Blend-a-med, Lacalut, Theramed and Causamed 
were between 85 and 95.