Surface Tension of Tooth Paste Solutions SAMUEL 11. GORDOIV IIVD EDWINW. SHAND, American Dental Association Bureau of Chemistry, Chicago, Ill.
E
ARLY in 1930 the Ameri-
Some contain in addition magThe surface tension of solutions prepared can Dental Association nesium hydroxide (added as milk j r o m fourteen samples of tooth paste have been through a recently organof magnesia), soap, astringents measured and the data tabulated and correlated. ized Council on Dental Theraor germicides as zinc chloride, The results do not bear out the absolute siatepeutics, undertook to place the v a r i o u s p h e n o l s , orris root, ment of the low surface tension alleged to have advertising of the dentifrice on potassium chlorate. These are a more truthful and rational mixed in paste form by the aid of been made by authorities and quoted in public level. One of the methods by glycerol, of glycerite of starch, advertising; the numerical values f o r surface which it hoped to accomplish and of gums such as tragacanth, of solutions f r o m soap dentifrices, as tensions this was by publishing a set of k a r a y a , a n d water, and are found, are all practically of the same order of provisions under which dentiflavored with sugar, saccharin, magnitude. Two types of surface tension data frices would be placed on a n acand volatile oilq. This general cepted list. These provisions statement ip not exhaustive, as were obtained-one corresponding to the pastes proposed to define a dentifrice as an examination of the patents Containing soap, the other to pastes containing a n agent to be used in conjunci s s u e d f o r dentifrices in the no soap. The solutions of all give relatively lox t i o n w i t h the toothbrush for past two decades would show. surface-tension data. cleaning the surfaces of the teeth. Probably no other class of prodNo tests were made to determine the relation N o c 1a i m s with bacteriologic, ucts betttr illustrates the extent therapeutic, or chemical infert o which the abuses of the patent between surface tension and cleansing power of ences could be accepted. It is situation have heen carried. It tooth pastes quoted in adcertisements. Nothing hardly necessary to mention that reflects credit neither to the inin this report indicates that a soap-containing the council cannot accept dentitelligence of the patentors nor to looth paste m a y not be as useful or more useful frices containing materials which the patent system. than a nonsoapy paste. The relation of these would be harmful when used for F o u r t e e n dentifrices were results to certain advertising is discussed. cleaning the teeth. used in the tests. Ten of these It has been encouraging that a c c o u n t , i n general, for the a fair Droportion of the large more widelv advertised Droducts nationai advertisers of dentifrices have seen fit t o modify in this class. Others were introduced as samples became their advertising so that it agrees with the provisions of the available. The samples were all original unopened packages. council. Consequently the readers of such advertising in Data on the composition of t’he tooth pastes investigated newspapers and magazines, and listeners over the radio have have been gathered from the manufacturer, from the techa more truthful representation of what dentifrices might nical and advertising literature, and from other sources. accomplish, even allowing for the puffery that accompanies S. T . 37 Tooth Paste. This tooth paste (made by Sharp & advertising t o the public. Dohme, Inc.. Philadelphia) is based apparently on the work of It was unfortunate, therefore, that photographs and signed Feirer and Leonard (6) who examined several tooth pastes contestimonials appeared in newspapers and magazines, claiming sisting essentially of gelatin, chalk, and glycerol, with sodium bicarthat the low surface tension of one dentifrice made it superior bonate and butyl- and hexylresorcinol. They claimed that such containing 1 per cent of sodium bicarbonate and 0.16 to the others as a cleaning agent, basing this distinction on aperpaste, cent, of hexylresorcinol in 20 per cent aqueous solution, the one characteristic. These signed testimonials were destroyed all of the common pathogenic bacteria in 15 seconds. accompanied by photographs of men described as distin- From the data reported below, i t is apparent that the name guished scientists, world renowned, unquestionable leaders ‘IS. T. 37 Tooth Paste” does not accurately define the comof the product on the market Furthermore, the in science, public figures of unimpeachable authority, etc., position council does not accept dentifrices for which bacteriologic claims together with quotations of their records from “Who’s R h o ” are made. Cnlgatr’s Ribbon Dental C r e a m 1 Each 100 grams of this paste and “American Men of Science.” The signed statements were to the effect that they had examined a number of tooth (made by Colgate-Palmolive-Peet Company, Chicago) contains grams glycerol. 5.0 grams soap (vegetable), 35.7 grams calpastes and that they had found one of them to possesb the 28.0 cium carbonate, 7.6 grams precipitated chalk, 2.1 grams sodium lowest surface tension. They concluded, without citing benzoate, 0.9 gram aromatics, 6.5 grams corn starch, and 14.2 factual evidence, that the tooth paste of the company which grams water. Zpana Tooth Paste. Preliminary unpublished investigations employed them possessed “the greatest cleansing action.” indicate that Ipana (made by Bristol-Myers Company, Sew On general grounds it could be assumed that any soap-con- York) contains 18.8 per cent glycerol, 38.5 per cent calcium taining dentifrices would have a low surface tension. carbonate, 28.1 per cent water, approximately 6 per cent soap, $naphthol, and a plant material which has not yet been fully These advertisements attracted the attention of this bureau and the writers awaited published reports in scientific journals investigated Forhon s This tooth paste (made by t h e Forhan Company, upon which these statements might be based. Inaqniuch as SPU York) n-as found to contain approximately 0 2 per cent these factual data did not appear, examination was under- of zinc chloride (2\, 5 per cent soap, and 46.0 per cent calcium taken here to determine the surface tension of “qolutionq” caibonate. The manufacturer? refused to divulge the formula. Iodent Tooth Paste No. 2 . 1 This paste (made by Iodent Chemiprepared from tooth pastes. cal Company, Detroit) is composed of 55 gram5 precipitated calcium carhonate, 6 grams soap, 34 prams glycerol, 1.25 gramE l P h R I B I E Z l . 4 1 ~I’HOCEDURE petrolatum, 0.25 gram saccharin, 1.0 gram oil of peppermint. Tooth pastes in general contain as abrasive either calcium 2 26 grams water, and 0.24 gram iodides (as potassium and cnlcarbonate or some form of calcium phosphate (tricalcium phosphate, calcium pyrophosphate, or dicalcium phosphate). 1 icceptable t o t h e Council 011 Dental Therapeutics
October, 1932
I N D U S T R I IL
; i
ND E N GI U E E
Iodent Tooth Paste A-o. 2.1 The composition is 30.14 grams precipitated calcium carbonate, 30.14 grams prepared calcium carbonate, 7.23 grams soap, 28.9 grams glycerol, 1.51 grams petrolatum, 0.30 grams saccharin, 1.20 grams oi! of peppermint, 0.30 gram water, m d 0.24 gram iodides (as potassium and calcium) (,?). Pebeco Tooth Paste.’ Each 100 grams of this paste (made by Lehn & Fink, Bloomfield, S. J.) contains 19.98 grams precipitated chalk, 41.62 grams potassium chlorate, 2.15 grams stearic acid, 14.87 grams sugar and glycerol, 19.13 grams water, 0.72 gram binder, and 1.53 grams flavoring (4). Pepsodcnl. This tooth paste (made by Pepsodent Company, Chicago) has an avowedly changing formula. The product has been the subject of several articles by Gies and collaborators (8). They pointed out the unwarranted claims concerning the film-removing properties through the agency of pepsin. Each formula was inferred to be the last word in dental science, a position difficult to reconcile in the light of the firm P advertising and changes of composition. I n 1920 the composition w s represented as followv-:
1% I \ G
C H E \I I S T R Y
1149
Specimens for the test were obtained by squeezing portions of the paste from the tubes and weighing by difference. Curqory visual examination indicated that the pastes were uniform as to homogeneity, with the exception of Iodent Tooth Pastes ?;os. 1 and 2. On squeezing from the tubes, the latter yielded a strip of paste with a layer of liquid surrounding it. CLASS
I
I
CLASS 2
% Pepsin Acid calcium phosphate Calcium chloride Precipitated tricalcium phosphate Glycerol, alcohol, water, flavoring, e t c . 111
0.81 1.04 0.44 51.99 45.72 SUPFACI TtRSIOH I N DYNtS
1926 the formida nxs given as:
FIGURE 1. %
Pepsin Acid calcium phosphate -4cid calcium t a r t r a t e Calcium chloride Benzoic acid Mitinated calcium DhosDhate T&alcium phosihate’ Anhydrous calcium sulfate Glycerol, water, flavoring, etc.
0.621 0.512 0.190 0.237 0.094 59.400
38 946
It is worthy to note the plethora of figures in this and the succeeding formula. One naturally wonders if this is the result of “laboratory analysis’’ or “lead pencil analysis” from the “mixing formula.” Pepsodent Tooth Paste is now advertised as having the following composition: % 59.400 0.100
0.600 1,200
0.237
38.463
The exact chemical nature of the “special” calcium phosphate is not stated in any advertising literature that has come to the attention of the authors. Preliminary investigation:, indicate it to be related to brushite (CaHP04,2H20). Listerine Tooth Paste. This paste (made by Lambert Pharmacal’company, St. Louis) is admittedly secret in composition. Qualitative tests indicate the abrasive portion t o consist of calcium sulfate and tricalcium phosphate. Soap was not found. Kolynos Denlal Cream. This paste (made by the Kolynos Company, Kern Haven, Conn.) was stated by the manufacturers to have the following composition: 18.87 per cent, alcohol, 0.21 per cent thymol, 0.35 per cent saccharin, 1.30 per cent oil of eucalyptus, 1.42 per cent oil of peppermint, 0.22 per cent benzoic acid, 28.63 per cent glycerol, 20.00 per cent soap, 29.01 per cent chalk ( 5 ) . Dr. V e s t ’ s Tooth Paste. This paste (made by The Western Company, Chicago) has the following formula, according to the manufacturer: 39.71 per cent calcium carbonate (Sturge), 0.76 per cent carbonate of magnesia, 1.51 per cent soap (imported castile), 17.80 per cent milk of magnesia, 2.50 per cent silica, 2.50 per cent simple sirup, 30.54 per cent glycerite of starch, 3.75 per cent mineral oil, 0.06 per cent gum tragacanth, 0.07 per cent saccharin, 0.78 per cent flavoring oils, 0.02 per cent color solution. Orphos Tooth Paste. This paste (made by Orphos Inc., Xew York) on qualitative examination was found to contain calcium sulfate and-tricalcium phosphate as the abrasive portion. Lactona Dentifrice. The specimen of Lactona (made by Lactona Company, Chicago) used for the surface tension test had, according to the manufacturer, the following formula: 41 to 45 per cent glycerol, 42 to 38 per cent tricalcium phosphate, 3.0 per cent galactonic lactone, 9.0 per cent wafer, 0.3 per cent malic acid, 3.7 per cent alcohol, 0.37 per cent gum tragacanth or karaya, 0.6 per cent sodium chloride and flavoring.
1. 2. 3. 4. 5.
Pt4
5Q. C k .
TENSION O F TOOTHPASTE IN DISTILLED M7.4TER
SURF.4CE
S. T. 37 Colgate’s Ipana Forhan’s Iodent No. 1
8,I . Iodent N o . 2. Pebeco 8. Pepsodent (A aplgo 2) 9. Listerine 10. Kolynos
11. 12. 13. 14. 15.
SOLUTIOXS
Pepsodent ( A aplgc 4 ) Dr. West’s Orphos Lactona Soap solution (5 70)
Aqueous solutions of these pastes were prepared by shaking together accurately weighed portions with accurately measured volumes of water. Both Chicago t a p water and distilled water were used. The suspended matter was allowed to settle out as far as possible, and a portion of liquid was drawn off and centrifuged a t a controlled, but nearly uniform, speed for a half hour to cause as many solid particles as possible to settle. The relative amount of water used with the toothbrush and paste by different people varies. Therefore, a wide range of concentrations was employed. One part of paste was mixed with the following parts of water: Parts 1 2
% by weight 50 331/a
Parts
% by weiohl
Parts
% bu weight
4
20 142/7
8
111/8 7g/ia
6
12
Five cubic centimeters of the centrifuged liquid were transferred to a clean watch glass, and the surface tension of the solution determined by means of a tensiometer, of the DuNouy type. A comprehensive treatment of the methods for measuring surface tension is included in articles by Ferguson, DuXoUy, and Klopsteg ( 7 ) . Constant readings could usually t e obtained by waiting for one minute after placing the solution in the dish, and one minute between readings. The usual precautions for cleaning the glassware used were observed. The instrument was standardized by the absolute method, and checked with boiled distilled water cooled to 22” C., as a reference liquid. Measurements were made a t prevailing room temperature (25” C.), The surface tension values for a 5.0 per cent solution of soap (U. S. P.) were determined for comparison. The results obtained are shown in Table I. Figure 1 and Figure 2 show the surface tension values of solutions in relation to concentration in distilled and t a p water, respectively. All the plotted points were connected by straight lines rather than by attempting t o draw curves.
DI~CUSSION OF RESULTS It may be seen from the graphs t h a t the values for surface tension obtained for the solutions of the tooth pastes examined
INDUSTRIAL AND
1150
ENGISEERING CHEMISTRY
Vol. 24, No. 10
TABLE I. DATAON TOOTH PASTES DILUTIOSR ~ T I O
PASTE
Grams
TEMP. WATER S U R F A CTESJIOX E Cc. D y n e s / s q . cm. C.
DILUTION R.ATIO P A ~ T E Grnms
P E R E C O TOOTH P.&STE
9. T. 37 TOOTH PASTE
1:l 1:2 1:4 1:6
1:s 1 : 1'
..
16.78 19.33 10.30 9.00 4.08 4.02 2.93 3.92 2.74 2.66 2.07 3.54
. . , . .
16.78" 19,33b 20.60 18.00 16.32 16.08 17.58 23.52 21.92 21.28 24,84 42.48 Distilled Tap
22.5 24.5 22.5 24.4 22.5 24.7 22.5 24.7 23.8 24.9 23.8 25.0 22.5 22.5
1:l
35.75 35.6 35.85 35.9 36.0 35.75 36.1 35.8 36.2 35.7 36.0 35.0 74.2 75.5
25.0 26.1 26.1 25.6 26.2 26.5 26.1 26.6 26.5 27.2 26.2 27.3 23.0 26.5
1:1
32.0 32.0 31.8 31.8 31.85 31.75 31.7 31.75 31.9 31.85 31.85 31.75 22.55 ,3 0
23.6 24.0 23.2 24.0 23.2 24.5 23.2 24.6 23.3 24.6 23.5 24.4 23.5 24.4
:1
32.75 32.3 32.75 32,35 32.95 32.5 33.8 32.6 34.8 33.0 36.0 33.4 l2.9 72.9
24.5 24,, 24.7 25.1 24.7 24.9 24.8 24.9 24.8 24.5 24.8 24.1 24.5 24.5
38.6 38.3 41.55 40.55 43.05 44.45 44.15 44.95 46.5 45.9 47.75 i6.45 (3.4 73.95
l:? 1:4 1:6 1:8 l:l?
..
14,30 15.65 9.41 9.66 6.30 5.18 5.12 3.50 3.25 3.01 2.62 2.49
1:2 1:4
1 :6 1:8 1: r?
..
16.19 12.85 10.07 8.33 4.97 5.20 3.70 2.72 4.44 3.00 3.16 2.88
...
...
16.19" 12.85) 20.14 16.66 19.88 20.80 22.20 16.32 35.62 24.00 37.92 34 .,56
Distilled Tap
1 2 :.I :A
:8 : 12
..
..
15.15 19.27 9.21 9.17 4.64 4.18 5.43 3.00 4.97 2.99 2.74 3.7"
...
...
1:L' 1:4
1:6 1:s 1:12
12.18 12.36 7.88 9.74 6.47 4.29 4.10 3.28 3.27 3.76 3.64 3.30
... , . .
12.18" 12.36b 15.76 19.48 25.88 17.16 24.60 19.68 26.16 30.08 43.68 39.60 Distilled Tap
.. .7_ :4
:6 :8 : 12
..
15.77 12.76 9.65 7.11 6.69 4.26 3.85 3.73 2.69 3.12 2.91 1 74
... ...
1:2
1:4 1:6 1:8 1 : 12
14.06 15.86 9.81 7.55 3.82 5.63 4.14 3.67 2.48 2.70 2.38 2.59
.. .
I
14.06a 15.86b 19.62 15.10 15.28 22.52 24.84 22.02 19.84 21.60 28.56 31.08 Distilled Tap
:1
I:? 1.4 1 H
1:Y l:l!
..
16.18 15.33 8.24 8.26 3.40 4.42 2.77 3.80 1.97 3.12 1.35 2.90
...
...
1:2 1:4 1:6
1:8 1: 1 2
..
14.68 20.83 11.23 8.08 7.86 6.34 3.29 6.01 3.26 3.92 3.07 2.02 ,.. ,..
14.68" 20.83b 22.46 16.16 31.44 25.36 19.74 30.06 26.08 31.36 36,84 24 24 Distilled Tap
32.8 33.0 32.75 31.9 33.5 31.8 33.7 32.0 33.9 32.8 34.35 33.0 72 85 72 9
23.2 24.0 23.4 24.5 23.2 24.5 22.0 24.5 22.2 25.2 22.1
25.5 22.3 24.9
1:l 1:2
1:4 1:6
1:s 1:12
..
1:l
l:? 1:6
1:s 1:12
..
.. a
Distilled water.
28.03" 16.16b 17.92 19.12 20.52 34.48 28.38 40.56 17.12 19.12 35.28 32.76 Distilled ... ... Tap b Tap water.
28.03 16.16 8.96 9.56 5.13 8.62 4.73 6.76 2.14 2.39 2.94 2.73
45.45 45.8 47.65 48.8 50.9 51.55 53.5 52.6 54.9 54.4 56.55 56.95 73.0 72.85
24.0 24.0 24.0 24.0 24.0 24.0 24.0 23.8 24.3 23.6 24.4 23.5 24.2 23.4
15.77" 12.76b 19.30 14.22 26.76 17.04 23.10 22.38 21.52 24.96 34.92 20.88 Distilled Tap
52.7 50.65 53.6 54.5 55.8 55.4 56.5 56.2 57.8 59.75 59.4 61.25 71.4 71.55
28.2 28.8 28.1 28.5 27.2 28.0 29.5 28.0 28.8 28.5 28.0 29.2 28.9 28.8
33.3 33.2 32.65 32.5 34.9 34.0 35 85 35.1 36.05 33.5 36.8 33.1 72.9 73.3
16.185 15.33b 16.48 16.52 13.60 17.68 16.62 22.80 15.76 16.96 16.20 34.80 Distilled Tap
32.7 33.0 32.4 32.9 32.55 32.55 32.65 32.1 32.75 32.25 32.7 32.0 71.85 72.3
27.2 27.0 28.0 26.8 26.5 27.2 27.4 27.0 28.2 28.0 27.5 27.1 27.5 27.0
33.65 16.70 6.06 7.19 3.46 5.16 3.70 4.09 2.99 4.00 2.52 1.76
49.4 49.45 49.6 49.8 51.2 52.55 52. F, 53.7 j4.0 54.0 55.0 5
