Pharmaceutical Research and Literature

DENTIFRICES AND THEIR INGREDIENTS.*

JOSEPH HEAD, M. D., D. D. S., PHILADELPHIA.

The question, what ingredients should make up an antiseptic dentifrice, is by no means simple. Chemicals may destroy the acid forming germs but at the same time so lower the natural resistive action of the tissues that the final condition of the mouth after treatment may be worse rather than better.

Clinical experience proves conclusively that unclean mouths exist where there is practically neither tooth decay nor tissue infection, and likewise shows that uncared for mouths exist where there are no bacterial deposits to speak of. This resisting tendency against the forces of infection may lie within the tissues of the mouth, but since the saliva seems unquestionably to possess, outside of mere alkalinity, a power to restrain enamel decalcification, it is easily possible that it may also exert some similar restraint on the infection of the remainder of the oral tissues as well.

The problem before us is as follows: The mouth contains certain self-protecting elements and tendencies against infection. When these are overthrown by a virulent bacterial invasion, infection results. In restoring health all bacterial deposits that can be readily reached should be removed mechanically, and the antiseptic washes to be used to assist in overcoming the remaining infection should supplant, not oppose the natural health-restoring processes of the mouth. That there are at least two classes of such health-restoring processes in the mouth seems indisputable: First, a substance or enzyme that is present for a specific purpose of special protection which is illustrated by the saliva's property of retarding enamel decalcification. The other class consists of an automatic power of resistance and self-repair which is illustrated by the power possessed by tooth enamel to reharden under partial decalcification, as well as its power to harden the surface when its softer under-substance is exposed by grinding to the saliva or air.

That saliva does possess the power of restraining enamel from acid decalcification is shown by the following test: A sound extracted tooth was placed in a sparklet or automatic soda-water-former in which the liquid could be charged from a carbon dioxid cartridge. Thirty cubic centimeters of saliva, which had been obtained by chewing rubber, were added. The saliva was then charged with carbon dioxid and the syphon placed in a culture oven for thirty days. At the end of that time the tooth was taken out. It appeared unharmed. The tooth was then wiped with a little ether to remove any grease, and replaced in the syphon with distilled water. This water was charged with carbon dioxid and the flask replaced in the culture oven for twenty-four hours. At the end of that time the enamel showed a chalky, rough decalcification that could be scaled off with the finger nail. The relative protective power, thus demonstrated, is exerted against lactic acid and various vegetable acids such as lemon, orange, * Read before the Phila. Branch. Reprinted from Journal A. Ph. A.

grape, strawberry, rhubarb and cherry, the action of which formed the subject of a paper written by the author in March, 1908. Other tests reported before the New York State Dental Society meeting seemed to prove that enamel partly whitened and softened within a limited scope, might reharden automatically.

For instance, 1:1000 lactic acid and water at mouth temperature will cut tooth enamel in thirty minutes with a rough, white surface. A tooth placed in 1:500 lactic acid and some salivas will be unharmed. In this solution made with other salivas, after three or four days the enamel of a tooth, though perfectly. smooth and to all appearances normal, can readily be pared to a slight distance with a lancet, and yet a 1:500. saliva and lactic acid solution has an extremely acid taste and instantly turns litmus brilliantly red.

Further tests and tables presented before the American Medical Association in June, 1912, and which will shortly appear in the American Medical Journal, seem to prove with a fair degree of credibility that enamel rehardens from a partial softening due to the attack of an acid.

Thus, we see that the action of dentifrices and mouth antiseptics may have a very different action in different mouths. Salivas have different protective properties, and the same saliva in a mouth will show a great variation in its preservative power during various conditions of the system. It is possible that gout, diabetes, tuberculosis, arteriosclerosis, or even a bad attack of grip may reduce the vitality of the resisting agencies against deterioration and so make the use of a gritty powder much more destructive.

Experimental means of determining the strength of mouth antiseptics in vitro. are subject to many fallacies. In the year 1904 I performed the following experiment: An old bridge, covered with bacterial deposits freshly removed from the mouth, was cut into small pieces, so that the bacterial deposits were undisturbed. These bacterial deposits were then submerged in various antiseptic solutions at mouth temperature for various intervals of time, at the end of which time the deposits were washed in sterilized water and test cultures made from them on blood serum. Peroxide of hydrogen made the best record of the antiseptics tested. But even with a 3 per cent. solution of peroxide of hydrogen and a submersion of five minutes, growths were nevertheless obtained on the blood. serum. This test is significant inasmuch as it proves that to be effective, peroxide or in fact any antiseptic, must be applied in sufficient concentration for a sufficient time.

Clinically, peroxide of hydrogen gives excellent results in reducing oral infections. According to the experiments of Paul Bert and Reynard, it was found that all fermentations caused by bacteria were at once stopped by peroxide of hydrogen and the ferment was killed, while no effect was produced on enzymes and physiological ferments such as are found in the gastric juice and pancreas, so that it would practically have no effect on digestion, and yet it would inhibit the interfering action of micro-organisms.

Recent experiments in the Mulford laboratories under the supervision of Dr. A. P. Hitchens, indicate that a one per cent. peroxide solution has the same strength in inhibiting the growth of typhoid bacilli as a one per cent. carbolic acid solution. This is particularly interesting in reference to the antiseptic action of certain oxygen liberating dentifrices which claim to cleanse the mouth by the development of hydrogen peroxide. The idea is so excellent that it should. be given encouragement by both pharmacists and the public at large, but none of

the peroxide forming dentifrices according to the analyses that have come to my notice, have ever been able to develop more than .5 per cent. of free oxygen. This, as can be shown mathematically, cannot form more than 35 minims of the standard 3 per cent. peroxide solution for each hundred grains of dentifrice. Now, the amount of tooth powder capable of being put on an average tooth brush is seldom as much as ten grains, which ten grains or less of powder would have to be depended upon to deliver the antiseptic action to the mouth. These ten grains of tooth powder under the most favorable conditions would then deliver 3 1/3 drops of the official peroxide solution, no more. Three and a third drops, or even five drops, would be palpably inadequate to have any effect on the bacterial masses of the mouth. Some of these preparations that claimed the power of sterilization by free oxygen, at times did not show the presence of free oxygen at all under analysis. This was due to some error in the manufacture, no doubt, but for practical antisepsis in the mouth it really made little difference, as three drops of peroxide of hydrogen would be so rapidly diluted and broken up by the oral tissues, that its antiseptic value in the course of half a minute could be hardly much more effective than so much distilled water.

Peroxide of calcium and peroxide of strontium, as recommended by many writers, are entirely too caustic to be used pure in the mouth. When placed in any quantity on the tongue they make a bad burn that lasts for days. However, the commercial preparation of peroxide of magnesium is bland, and, in my opinion, more useful. It comes diluted with magnesium hydroxide and carbonate, so that it yields from four to seven per cent. free oxygen, and is only soluble in about 15,000 parts of water (practically insoluble). This powder can be freely taken into the mouth in any quantity, liberating for every hundred grains enough oxygen to make 280 to 500 drops of a 3 per cent. alkaline peroxide solution. The commercial powder has just about the cutting grit of precipitated. chalk, and when finely powdered, practically none at all. When the mouth is evacuated large quantities adhere to the interstices and necks of the teeth. This tendency may be turned to great advantage by the patient, for, while this powder is practically insoluble in water, it is readily converted into a soluble magnesium salt by any acid that may chance to be present.

But now let us discuss another phase of dentifrices that is even of greater importance than their carbolic acid coefficient. All thoughtful dentists must have noticed that there is a terrible disease that affects the mouths of those who are particularly careful of their teeth, and this shows generally between the ages of forty and fifty by the complete disappearance of the enamel in ever-spreading foci on the anterior surfaces of the front teeth. This has been explained by many as arising from an acid diathesis of the system-gout, rheumatism, indican, and the absence of the sulphocyanates, not to speak of the acid calcium phosphates. Now, no one would deny that there may be a systemic cause for this disease, but not to my knowledge has there been reported one such case in the mouth of a patient who did not carefully use tooth powder and brush, and as the loss of enamel is confined almost entirely to incisors, canines, bicuspids and first molars, it would seem strange that a systematic disease would not attack all of the teeth of the mouth with a certain amount of impartiality. Therefore, I felt that, while the disease might be partly systemic, it did not have, of necessity, to be so.

In 1908 I published in the "Dental Brief" experiments showing the effect of grits on the teeth, proving conclusively that tooth powders even of chalk were largely instrumental in cutting the well-known smooth grooves in the necks of teeth that so frequently appear from second molar to second molar. Although these tests were judged only from their macroscopic effect and no measuring instrument of precision was used, and although they were faulty inasmuch as they did not reveal the full extent and significance of the destructive action of pumice, chalk, etc., they were the beginning of a long series of experiments of which this paper is a partial summary. I, therefore, undertook a rather voluminous series of experiments to determine just what would happen to the enamel and cementum of a tooth when brushed with an ordinary tooth brush and saliva, when brushed with certain mouth, washes, when brushed with certain standard proprietary dentifrices, and finally what happened when brushed with plain precipitated chalk.

The first test was made to determine what was the effect of brushing the enamel and cementum for ten minutes with a new brush and saliva alone. No enamel loss was discovered but a loss of 1/10,000 of an inch of cementum was noted. But, as many other tests with plain saliva discovered only a polishing effect on the cementum, it was finally decided that the first test was an accident, and that the plain brush and saliva seemed to have no harmful effect on cementum or enamel that ten or twenty minutes brushing could determine. Six of the most prominent and best advertised dentifrices were tested in the same manner. a new brush being used with saliva and dentifrice for each test, the brushing being continued for ten minutes.

Dentifrice No. 1, in ten minutes test, cut off 1/10,000 of an inch of enamel and from 23 to 83 ten thousandths of an inch of cementum.

Dentifrice No. 2, under similar conditions, gave a loss of 1/10,000 of an inch of enamel and 26/10,000 of an inch of cementum.

Dentifrice No. 3, gave no loss of enamel and a loss of 66/10,000 of an inch of cementum.

Dentifrice No. 4, gave a barely measurable loss of enamel and 121/10,000 of an inch of cementum.

Dentifrice No. 5, caused no loss of enamel and 73/10,000 of an inch of cemen

tum.

Dentifrice No. 6, caused no loss of enamel and 7/10,000 of an inch of cemen

tum.

The only reason the powders with grit are so popular, in my opinion, is because they make the front teeth presentable with a minimum amount of labor. In brushing their teeth some patients wash for high neck, not for low neck, and, while this is partly due to laziness, it is also due to the inefficient unscientific teaching on the part of the profession who recommend methods of tooth brushing that a simple inspection of the mouth will show do not cleanse the teeth.

Having investigated some of the prominent proprietary dentrifices, I next ap plied the same tests to the standard chemical substances that might prove of value in mouth prophylaxis. I found, as would be expected, that ordinary precipitated chalk would cut the cementum and enamel. Thinking there might be an excess of silica in it, I procured precipitated chalk from a standard chemical company, guaranteed to be free from silica. It seemed to cut more than the others. I next tried the peroxide of magnesium in reference to its grit, and

found in its coarse state that it had a friction grit on the enamel and cementum somewhat less active than precipitated chalk, but nevertheless a decided grit. When, however, the peroxide of magnesium was ground in an agate mortar to impalpability, no such erosion was attained, thus showing that in peroxide of magnesium we can have a grit slightly less than chalk down to almost no grit at all, and also a tooth powder that will give abundant oxygen, so as to have a real antiseptic action on the mouth. I next tried the frictional action of perborate of soda, mixed with saliva, on a tooth and was not able to note that the Brown & Sharpe micrometer showed any erosive action. This was particularly gratifying as perborate of sodium is a bland salt that can freely be placed in the mouth without caustic action, and liberates 9 to 10 per cent. of oxygen, and in the presence of any acid that may be present forms a strong alkaline peroxide solution. When patients come to me with spots of dentin showing underneath the enamel of the front teeth, I prohibit them from using grit dentifrices of all sorts and recommend that they brush their teeth with perborate of soda alone. And when these patients have been carefully instructed in the proper act of brushing their teeth, perborate of soda seems quite able to keep the teeth clean without the aid of grits.

For patients that have healthy gums with no tendency to gum recession or thinning of the enamel, I use the following formula:

Peroxide of Magnesium (No. 200 inch sieve).

Perborate of Sodium...

Pulv. Saponis

60 parts

30 parts

Flavoring to suit.

10 parts

Tested with the latest method of brushing for ten minutes, this powder gave no loss of enamel and from 3/10,000 to 9/10,000 of an inch of cementum. It will be noted from the beginning of these tests that where erosion was demonstrated the demonstration was beyond question; but sometimes the presence of erosion was not noted owing to the absence of proper measuring instruments or incomplete technique.

Mr. Heidelberg of Mulford's laboratory has furnished me with three specimens of chalk. No. 1 sample was made by precipitation in 50 litres of water with very slow precipitation. No. 2 was made in 1 litres and was so concentrated a solution that in precipitating them slowly the drops of calcium chloride did not mix with the soda solution, both solutions being poured together quickly in order to produce a precipitate. The slow precipitate, as was expected, gave a larger crystal than the quick precipitate. The larger crystals of specimen No. 1 varied from 17 to 5.6 microns in diameter. The smaller crystals of specimen No. 2 measured 4 to 2 microns in diameter. Mr. Heidelberg sent me also a purchased specimen of precipitated chalk that had been ground much finer than the precipitated crystals, and yet these three specimens seemed about equally destructive of enamel and cementum. This would indicate that it is the chalk, not the preparation that is responsible for its gritty destructive action.

Mr. Beringer also supplied me with some specimens of precipitated chalk, silicious earth, precipitated phosphate of calcium, precipitated carbonate of calcium, and some calcined magnesium (light) that I might test them for their erosive action, hoping that they might be less harmful as the table of all the tests will show.

Erosion tests with a tooth brush on a natural tooth, brushed for ten minutes with saliva solution and various grits.