US3060098A

US3060098A - Dentifrice

Info

Publication number: US3060098A
Application number: US696953A
Authority: US
Inventors: Sol D Gershon
Original assignee: Lever Brothers Co
Current assignee: Lever Brothers Co
Priority date: 1957-11-18
Filing date: 1957-11-18
Publication date: 1962-10-23
Anticipated expiration: 1979-10-23
Also published as: GB840161A

Description

United States Patent 3,060,098 DENTIFRICE Sol D. Gershon, West Engiewood, NIL, assignor to Lever Brothers Company, New York, N.Y., a corporation of Maine No Drawing. Filed Nov. 18, 1957, Ser. No. 696,953 8 Claims. (Cl. 167-93) This invention relates to a dentifrice capable of giving a high luster to teeth and more particularly to a dentifrice having high luster-producing characteristics comprising tat-alumina in admixture with a polishing agent having a Mohs hardness below about 6.

Probably the most important single ingredient of a dentrifice is the polishing agent. This ingredient is in large measure responsible for the scouring and polishing action of the dentifrice. Securing is essential to remove the more closely adherent matter and to produce a good tooth luster. In order to obtain an optimum luster effect, however, it is necessary to balance carefully the abrasive and polishing characteristics of the polishing agent. An ingredient which is quite hard will be excessively abrasive, may tend to produce grooving of the teeth, and will re move excessive amounts of enamel. On the other hand, a polishing ingredient which is too soft does not have an adequate scouring and polishing power, and will not give good tooth luster because of this deficiency. All commonly used polishing agents cause microscopic pits and scratches in the enamel, to varying degrees.

Many ingredients have been proposed as scouring and polishing agents, including calcium carbonate, the various cmcium phosphates and particularly dicalcium and tricalcium orthophosphates, pumice, silica, kaolin, magnesium oxide and hydroxide, and various aluminas and alumina hydrates. The harder ingredients such as pumice tend to scratch the teeth. Aluminas in general are too abrasive and produce undue grooving and scratching. Other ingredients such as magnesium oxide may have adequate scouring power but have a disagreeable taste. It has been proposed heretofore to use microcrystalline aluminum hydroxide in major amount mixed with other somewhat harder materials, but this is relatively soft, too soft to give the desired scouring and polishing effect. None of these is entirely satisfactory from the standpoint of tooth luster.

The standardized luster test to evaluate ability to improve tooth luster in accordance with the invention. is carried out as follows:

The labial surface of an extracted human central incisor is smoothed with sandpaper, ending with fine grade sandpaper, followed by levigated alumina, and then dulled by bufiing with a slurry of chalk. The enamel surface then contains pits characteristic of a chalk-dulled surface. The degree of dullness is carried to a uniform low reflectance level as measured by a standardized light sourcephotocell assembly. The tooth is then brushed with the test composition on a standardized brushing machine for a period of two hours, following which the luster is again measured. The luster increase represents the difference between the prebrushing luster figure and the figure obtained after brushing with the test dentifrice, and is the average of the luster increase obtained on three different teeth. The measurement of luster of any one tooth is accurate within one unit. The same three teeth are used in any comparative test series.

The test dentifrice is evaluated for its tendency to pit and scratch and groove by brushing with the test dentifrice three human central incisors whose surfaces have been made absolutely pitand scratch-free by polishing with silica.

The dentifrice composition of the instant invention comprises an a-alumina having an average particle size with- 3,0509% Patented Oct. 23, 1962 ice in the range from about 0.05 to about 5 microns, preferably from 0.2 to 1.5 microns, and a Mohs hardness of about 9, in an amount Within the range from about 0.1 to about 40%, preferably 0.5 to 5%, of the total polishing agent, in combination with from 99.9 to 60%, preferably 9915 to of one or more additional polishing agents having a Mohs hardness below about 6. Dicalcium orthophosphate dihydrate is preferred. The a-alumina polishing agent of the invention is characterized by smoothly surfaced particles having rounded edges, i.e., free from sharp corners.

The polishing agent mixture in accordance with the invention gives a balanced scouring and polishing action when the tat-alumina and the supplemental polishing agent are present in proportions within the ranges stated. In fact, mixtures having these proportions give an optimum enamel surface substantially free from grooves, scratches and pits. The a-alumina alone is very abrasive and produces very heavy enamel grooving. Dicalcium phosphate is a substance of relatively low abrasive properties, but it nonetheless can give heavy scratching and light pitting of the enamel. The mixture of both in accordance with the invention also produces an optimum luster increase or superior to that obtainable with (it-alumina alone.

There are many crystalline forms of alumina and it is important to distinguish these. a-Alumina is anhydrous, of the formula A1 0 and has a melting point of 2050 C. it is distinguished by its X-ray diffraction pattern from other aluminas, including B-alumina and 'y-alurnina, and from their hydrates. Bayer process alumina is the octrihydrate (page 5, Technical Paper No. 10, entitled Alumina Properties, by Allen A. Russell, published by the Aluminum Company of America, and Industrial and Engineering Chemistry 37, 796802 (1945)). The Bayer process alumina described in the Atkins Patent No. 2,010,910 is a calcined a-trihydrate, probably having a water content within the range Al O -0.5H O to Al O -3H O. Aluminum hydroxide is another name for the a-trihydrate, an antecedent before calcining of a: and y-alumina. Calcining the a-trihydrate for one hour at about 1150 C. produces ot-alumina, and calcining at 450 C. produces 'y-alumina which is hygroscopic.

An especially preferred tat-alumina for use in accordance with the invention is Linde Type A a-alumina abrasive. This material is an a-alumina available commercially, having an approximate average particle size of 0.3 micron, an apparent density of 0.3 to 0.6 g. per c., and a melting point of 2050 C., and is characterized by smooth-surfaced particles having round edges. It has a hardness of 9 on Mohs scale, corresponding to co. rundum. Linde Type C is the same as Type A but has an average particle size of 1 micron.

The a-alumina employed in the compositions of the invention is obtainable by calcining ammonium aluminum sulfate, usually in the form of ammonium alum, its dodecahydrate, at temperatures in excess of 1150 C. but well below the fusion point of tat-alumina, preferably about 1175 C. Calcining at such temperatures avoids fusion of the mass and yields a powdered product of the desired particle size, namely, within a range from 0.05 to 5 microns, and the particles have rounded edges, whereas pulverization produces particles having sharp edges.

In addition to the oz-alumina, which is present in only a small amount, there is employed another polishing agent having a Mohs hardness below about 6. The preferred supplemental polishing agent is dicalcium orthophosphate dihydrate. There can also be used tricalcium orthophosphate and calcium pyrophosphate, as well as an insoluble sodium polymetaphosphate, calcium carbonate, magne sium oxide and magnesium carbonate. These can be used alone or in admixture; the insoluble sodium polymetaphosphate would usually be used with a calcium or magnesium phosphate or carbonate.

The dentifrice usually will contain from about 20% to about 99.5% total of the polishing agent, depending upon the physical state of the dentifrice. Preferably from 40 to 60% is used in a tooth paste and from 88 to 98% in a tooth powder; of this, from 0.1 to 40% will be a-alu-mina and from 99.9 to 60% other polishing agents.

'In addition to the polishing agent, the dentifrice can contain as optional ingredients a soap or synthetic detergent as a surface tension depressant, flavoring materials, oxygen-releasers, such as perborates, buffers, sweeteners, such as saccharin, harmless coloring materials, in proportions to give any desired reflect. These are conventional components of dentifrices, and materials suitable for this purpose need not be enumerated, for they are well known to those skilled in the art.

In a preferred embodiment of the invention, the dentifrice is in the form of a paste, and in this event it will contain a carrier and softener and a binder in amounts to give the dentifrice a smooth texture and good flowa-bility. Glycerin and sorbitol are preferred carriers and softeners, but ethyl alcohol, mineral oil, syrup, glucose and invert sugars, glycols and honey can also be employed. As binders there can be used gum tragacanth, sodium carboxymethylcellulose, Indian gum, lrish moss and its derivatives, starch, acacia gums, agar agar, locust bean gum, pectin and petrolatum. Those skilled in the art know other carriers and softeners, and binders The dentifrice also can contain therapeutic agents such as tryothrycin, chlorophyllins, hexachlorophene, the sarcosides, and water-soluble ionizable fluoride compounds, and the amount is not critical but will be enough to obtain a beneficial effect. Usually an amount within the range from about 0.01 to about 2% by weight of the dentifrice is suificient. The fluoride content is calculated as fluoride ion. The alkali metal fluorides are conveniently available and would ordinarily be employed. Sodium fluoride, sodium fiuostannite, lithium fluoride, stannous fluoride, stannous chlorofluoride, potassium fluoride and ammonium fiuoride are typical of the members of this class.

The following are general formulations of tooth pastes and powders coming within the scope of the invention:

TOOTH PASTE Percent by weight Permissible Preferred range range Tot-a1 polishing agent 20 to 80 40 to 60.

aumina 0.25 to 2.5. Other polishing agen 39.75 to 57.5. Carrier and softener 15 to 40. Binder 0.7 to 5. Miscellaneous... 15 to 40. lavor 0.8 to 2. Water 15 to 30. Surface tension depressant- .5 to 3.5.

rs 1 to 2. Preservative 1 to 0.3.

TOOTH POWDER Percent by weight Permissible Preferred range range Total polishing agent 88 to 98. lamina .5 to v I Other polishing agent 7.5 to 93. Miscellaneous .5 mas.

The following examples represent in the opinion of the inventor preferred embodiments of his invention:

Examples 1 to 12 A group of dicaloium phosphate dentifrices was made up according to the following formulation:

Parts by weight Ingredients Control Examples Diealciurn phosphate dihydrate 47. 57 47. 07

rat-Alumina as stated in Table I 0.50

Sodium earragheenate 1. 00 1.00

Aqueous sorbitol solution, 70%., 20. 6-1 20. 64

Polyethylene glycol 400 4. 26 4. 26

Glycerin a 4. 38 4. 38

Distilled Water s a 19.88 10. 88

Sodium lauryl sulfate 1. 17 1. 17

Flavor 1.10 1. 10

These dentifnces were sub ected to the luster test with the following results. Surface eifects evaluation was done by microscopic examination at a magnification of 57x:

Table I Example Abrasive X-ray analysis Luster Surface efieets N0. increase Control A- Diealcium phos- 33 Heavy scratchphate. ing, light pitting.

1 Linde Type A u-Alumina.-. 53 Light scratching, slight pitting.

2 Alcoa A5 do 37 Heavy scratching, very heavypitting, moderate grooving.

3 Alcoa A10 do 38 Heavy scratching, very heavypitting, moderate grooving.

4 Alcoa A14 "do 36 Heavy scratching, heavy pitting, modcrate grooving.

5 Alcoa A302 do 36 Very heavy scratching, moderate grooving.

6 Alcoa T60 do 32 Very heavy grooving.

7 Alcoa T61 do 31 Very heavy scratching, heavypitting, very heavy grooving.

8 Norton 600X.. --d0 39 Very heavy scratching.

9 Norton 38600X do 38 Very heavy scratching, very heavy grooving.

10 Norton 38900.... do 37 Very heavy scratching, very heavy pitting, heavy grooving.

11 Kaiser alumina Q-Trihydrate 42 Heavy pitting,

hydrate. heavy groov- 12 Reynolds alufi-Trihydrata 42 Heavy pitting,

mina hydrate. moderate grooving.

The table shows the improvement in tooth luster-producrng 6iTCflV6I1SS of the dicalcium phosphate dentifrices which result from the addition of 0.5% of the alumina given in the table. The dentifrice containing the Llnde Type A u-alumma abrasive in accordance with the invention gave an almost glass smooth tooth surface, free from grooves and practically free of pits and scratches,

and a luster increase of 53. The other dentifrices tested were markedly inferior, giving a tooth surface marked with a multitude of microscopic pits, scratches, and grooves, and a luster increase as low as 31, well below Control A.

Examples 13 to 16 Four dicalcium phosphate tooth paste formulations were prepared using from 0.25 to 1% a-alumina having the following formulation:

Example No. Ingredients Linde Type A a-alumina 0.25 0.50 1.00 Dicalciurn phosphate dihydrate 47. 57 47. 32 47. 07 46. 57 Sodium carragheenate 1.00 1.00 1.00 1. 00 Aqueous sorbitol solution, 70%.. 20. 64 20.64 20.64 20.64 Polyethylene glycol 400."- 4. 26 4. 26 4. 20 4. 26 Glycerin 4. 38 4. 38 4. 38 4. 38 Distilled water-.. 19. 89 19. 89 19.89 19. 89 Sodium lauryl sulfate 1.17 1.17 1.17 1.17 Flavor 1.09 1. 09 1.09 1. 09

The luster increase was as follows:

Ex. Abrasive Luster No. increase 13.... Dicalcium phosphate 33 14 Mixture of dicalcium phosphate and Linda Type A 53 a-alumina, 0.25%. 15 Mixture of dicalcium phosphate and Linde Type A 56 a-alumina, 0.5 16"--. Mixture of di alcium phosphate and Linde Type A 57 a-alumina, 1.0%.

Example 17 Two dicalcium phosphate formulations were prepared as follows:

Percent by weight Ingredients Linde Type a-alumina 0.10 Dicalciurn orthophosphate dihydrate.. 49.63 49.63 Sodium earragheenate" 0.95 0. 95 Aqueous sorbitol solution, 70% 19. 72 19. 72 Polyethylene glycol 400 4.07 4.07 Glycerin 4. 38 4. 38 Distilled water 19. 01 19. 01 Sodium lauryl sulfate 1. 17 1. 17 Flavor- 1.07 1.07

Formulation B gave a luster increase of 49, as compared to 37 for formulation A.

Teeth brushed with the dentifrice containing a-alumina had a smoother surface than the teeth brushed with the control paste which did not contain a-alumina. Moreover, the tooth surfaces brushed with the or-alumina dentifrice were relatively free from microscopic scratches and pits characterizing tooth surfaces brushed with the control dentifrice.

Example 18 The following is an example based on a mixture of dicalcium phosphate dihydrate and dicalcium phosphate anhydrous as the supplemental polishing agents:

Percent by weight Ingredients Dicalciurn phosphate dihydrate 42. 72 41. 72 Dieaicium phosphate, anhydrous. 5.00 5.00 zit-Alumina, Linde Type A 1.00 Sodium earragheenate 1.00 1. 00 Aqueous sorbitol solution, 70%.- 20.64 20. 64 Polyethylene glycol 400. 4. 26 4. 26 Glycerin- 4. 27 4. 27 Distilled wa 19. 19. 90 Sodium lauryl s 1.13 1. 13. Flavor. 1. 08 1. 08

In the following example tricalcium phosphate is used as the supplemental polishing agent:

Percent by weight Ingredients Triealeium phosphate 36 20 35. 20 a-Alurnina, Linde Type A 1. 00 Gum tragacanth. 1. 00 Glycerin 23. 60 Distilled water 29. 29 29. 29 Urea. 3. 00 3. 00 Diammonium phosphate 5.00 5. 00, Sodium lauryl sulfate 0.96 0. 96 Flavor- 0. 0. 95

Formulation A gave a luster increase of 43, whereas formulation B gave a luster increase of 54, 11 points higher.

Teeth brushed with the dentifrice containing lit-alumina had a smoother surface than the teeth brushed with the control powder containing no zit-alumina. Moreover, the tooth surfaces brushed with the a-alumina dentifrice were relatively free from the microscopic scratches and pits characterizing tooth surfaces brushed with the control dentifrice.

Example 20 A calcium carbonate type formula was made up as follows:

Percent by weight Ingredients Calcium carbonate (chalk, light U.S.P.) 46. 98 46.48 a-Alumina, Linde Type A- 0. 50 Glycerin. 31.39 31. 39 Distilled wate 18. 40 18. 40 Sodium lauryl s 1.01 1.01 Sodium oarraaheenare 1. 20 1. 20 Flavor- 1. 02 1. 02

Formula A gave a luster increase of 26, and formulation B a luster increase of 51, an increase of 25 points. Teeth brushed with the dentifrice containing (It-31111111118. had a smoother surface than the teeth brushed With the 7 control powder containing no a-alumina. Moreover, the tooth surfaces brushed with the tat-alumina dentifrice were relatively free from the microscopic scratches and pits characterizing tooth surfaces brushed with the con trol dentifrice.

Example 21 A calcium pyrophosphate tooth paste was prepared as follows:

Formulation A had a luster increase of 40, and formulation B a luster increase of 52, 12 points higher.

Teeth brushed with the dentifrice containing a-alumina had a smoother surface than the teeth brushed with the control paste which did not contain tat-alumina. Microscopic scratches and pits Were reduced in number, compared With the control dentifrice.

Example 22 A dicalcium phosphate dihydrate tooth powder having the following formulation was prepared:

Percent by weight Ingredients Dicalcium phosphate dihydrate 96. 85 95.85 a-Alumina, Linde Type A 1. 00 Sodium lauryl sulfate. 1. 25 Flavor 1. 90

Formulation A gave a luster increase of 39, whereas formulation B was 16 points higher, or 55.

Teeth brushed with the dentifrice containing ot-alumina had a smoother surface than the teeth brushed wtih the control powder containing no a-alumina. Moreover, the tooth surfaces were relatively free from the microscopic scratches and pits characterizing tooth surfaces brushed with the control dentifrice.

Example 23 Four different tooth paste formulations were made up, two containing a mixture of dicalcium phosphate and Linde Type A tit-alumina abrasive, another identical with this but without the u-alumina abrasive, and a third which did not contain any dicalium phosphate, but in which the tat-alumina abrasive constituted the sole polishing agent. These dentifrices had the following formulation:

Parts by weight Ingredients A B O D Linde Type A malumina 39. 77 0. 50 10.00 Diealeium orthophosphate dihydrate. 49. 63 49. 13 37. 20 Sodium carragheenate 0.95 0.80 0.95 0. 90 Aqueous sorbitol solution, 70%- 19.72 24. 31 19. 72 20. 87 Polyethylene glycol 400 4.07 5.03 4. 07 4. 31 Glycerin 4. 3S 4. 38 i. 38 4. 38 Distilled water 19. 01 23. 43 19.01 20. 09 Sodium lauryl sulfate 1.17 1.17 l. 17 l. 17 Flavor 1.07 1.11 1.07 1. 08

These paste dentifrices were tested for luster increase, abrasion (enamel loss) and surface effects. Abrasion testing was done by measuring the thickness of extracted human teeth before and after each brushing with a given dentifrice; any differences represented enamel loss. The test was as developed by G. H. Wandel. The test tooth was first conditioned by storage in tap water until the thickness measurements were constant and remained constant for three successive days. The tooth was mounted in the bottom of a metal cup directly below a revolving brush of the type used by dentists in prophylactic work. The slurry of the test product was then poured into the cup and the machine was operated. The cup and tooth were moved slowly back and forth beneath the revolving brush for a period of one hour. The tooth thickness was then remeasured. The abrasion loss represents the difference between the initial and final measurement of tooth thickness. Results on three teeth were averaged to obtain the abrasion loss value. This test is reported in chapter 15, Dentifrices, by S. D. Gershon, H. H. Pokras, and T. H. Rider, of the text Cosmetics: Science and Technology, by Sagarin, Interscience Publishers (1957). Surface effects evaluation was done by microscopic examination at a magnification of 57X of teeth brushed with denti-frices containing each of the abrasives indicated.

The above results show that a tooth paste composed wholly of dicalcium phosphate is a nonabrasive, low luster producer which causes heavy scratching and light pitting (dentifrice A). An abrasive composed entirely of the Linde Type A a-alumina is a good luster producer but it is very abrasive and causes very heavy enamel grooving (dentifrice B). Dentifrices composed of a mixture of dicalcium phosphate and 0.5% and 18% Linde Type A a-alumina abrasives are relatively nonabrasive, excellent luster producers which leave a minimum of enamel surface markings with only light scratching and slight pitting (dentifrices C and D). The Luster Increase is much higher than would be expected for the amount of tit-alumina that is present (only 0.5% in dentifrice C) and the enamel loss also is less than would he expected, particularly in dentifrice C, and the surface is better as well, being smooth and virtually pit-, grooveand scratch-free.

Increasing the amount of tat-alumina in D to 10%, Le, twenty times C, gave only a small Luster Increase as compared to C, and a considerably greater enamel loss with light grooving. This shows the desirability of employing a minimum amount of the a-alumina, since the smaller amounts give practically as good a Luster Increase without undesirable side effects. This confirms the preference for an amount within the range from 0.5 to 5% tit-alumina by weight of the total polishing agent. However, obviously considerably more a-alurnina could have been used without obtaining undue abrasion and heavy grooving.

It will be evident to those skilled in the art that many variations can be made in the compositions of the dentifrice of the invention and accordingly the invention is not to be limited except as set forth in the appended claims.

All parts and percentages in the specification and claims are by weight.

I claim.

1. A dentifrice capable of imparting an improved luster increase to teeth with a minimum of surface enamel markings including pits, scratches and grooves, said dentifrice being composed of from about 20% to about 99.5% by weight of a polishing agent consisting essentiaL ly of from about 0.1% to about 40% by weight of anhydrous alpha-alumina composed of smoothly surfaced particles having rounded edges of an average particle size within the range of from about 0.05 to about microns, a density of about 0.3 to 0.6 gram per cubic centimeter, and a Mohs hardness of about 9, and from about 99.9% to about 60% by Weight of a supplemental polishing agent having a Mohs hardness below about 6 and selected from the group consisting of dicalcium phosphate, tricalcium phosphate, calcium pyrophosphate and calcium carbonate.

2. A dentifrice in accordance with claim 1 in which the supplemental polishing agent is dicalcium phosphate.

3. A dentifrice in accordance with claim 1 in which the supplemental polishing agent is tricalcium phosphate.

4. A dentifrice in accordance with claim 1 in which the supplemental polishing agent is calcium pyrophosphate.

5. A dentifrice in accordance with claim 1 in which the supplemental polishing agent is calcium carbonate.

6. A paste dentifrice in accordance with claim 1 in cluding from about 20% to about 85% by weight of the polishing agent, from 5% to 70% by weight of a carrier and from 0.5% to 30% by weight of a binder.

7. A powder dentifrice in accordance with claim 1 comprising from 83% to 99.5 by weight of the polishing agent.

8. A dentifrice capable of imparting an improved luster increase to teeth with a minimum of surface enamel mark- 5 ings including pits, scratches and grooves, said dentifrice being composed of from about 20% to about 99.5% by Weight of a polishing agent consisting essentially of from about 0.25% to about 5% by weight of anhydrous alpha-alumina composed of smoothly surfaced particles having rounded edges of an average particle size within the range of from about 0.2 micron to about 1.5 mi crons, a density of about 0.3 to 0.6 gram per cubic centimeter, and a Mohs hardness of about 9, and from about 99.5% to about 95% by weight of a supplemental polishing agent having a Mohs hardness below about 6 and selected from the group consisting of dicalcium phosphate, tricalcium phosphate, calcium pyrophosphate and calcium carbonate.

References Cited in the file of this patent UNITED STATES PATENTS 2,010,910 Atkins Aug. 13, 1935 2,359,326 Moss et al. Oct. 3, 1944 2,550,207 Tainter et a1. Apr. 24, 1951 OTHER REFERENCES

Claims

1. A DENTIFRICE CAPABLE OF IMPPRTING AN IMPROVED LUSTER INCREASE TO TEETH WITH A MINIMUM OF SURFACE ENAMEL MARKINGS INCLUDING PITS, SCRATCHES AND GROOVES, SAID DENTIFRICE BEING COMPOSED OF FROM ABOUT 20% TO ABOUT 99.5% BY WEIGHT OF POLISHING AGENT CONSISTING ESSENTIALLY OF FROM ABOUT 0.1% TO ABOUT 40% BY WEIGHT OF ANHYDROUS ALPHA-ALUMINA COMPOSED OF SMOOTHLY SURFACED PARTICLES HAVING ROUNDED EDGES OF AN AVERAGE PARTICLE SIZE WITHIN THE RANGE OF FROM ABOUT 0.05 TO ABOUT 5 MICRONS, A DENSITY OF ABOUT 0.3 TO 0.6 GRAM PER CUBIC CENTIMETER, AND A MOHS HARDNESS OF ABOUT 9, AND FROM ABOUT 99.9% TO ABOUT 60% BY WEIGHT OF A SUPPLEMENTAL POLISHING AGENT HAVING A MOHS HARDNESS BELOW ABOUT 6 AND SELECTED FROM THE GROUP CONSISTING OF DICALCIUM PHOSPHATE, TRICALCIUM PHOSPHATE, CALCIUM PYROPHOSPHATE AND CALCIUM CARBONATE.