272 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS TABLE 2--ACTIVE ETHYLENE DIAMII•E DERIVATIVES (REcovERY LEss THAN 40 PER CE•T) Ethylene Diamine Imidazoline Piperazines Di- [1-(3-ethylamyl)- 4-ethyloc tyl) ] Di(4 Ethyl-l-methylhexyl) 2-Ethylhexyl Di Alkyl, t5 alkyl aminoethyl I, fl-hydroxyethyl 2-(,,2-Ethyl- hexoxy) ethyl N-Decyl N-Nonyl N-Dodecyl H-Neptyl N-Diphenyl propenyl N-Octyl N-Diphenyl propenyl N-Oetyl N-Diphenyl methyl N-Fluorenyl N-(1-Naphthyl, 1-phenyl methyl) TABLV. 3•HER INHIBITORY AMINES (FROM A TOTAL Or 111 TESTED) (RzCOVER¾ LESS THAN 40 PER CENT) Substitution Conch. Decyl 0.1 Dodecyl 0.1 N,N Dimethyl dodecyl s/2 Methyl benzyl 1.0 Ethoxy phenyl s/10 (3 Aminopropyl) rosin 1.0 decyl amine and dimethyl dodecyl amine are inhibitory, indicating that methyl substitution does not interfere with activity of an amine. A second- ary amine with two large alkyl groups sometimes has no inhibitory action, probably because of a decrease in solubility. The amines studied are presented in Table 4 with each compound listed 'alphabetically in one of six groups according to its inhibitory effect. The number following each name is the concentration at test, and the letters "pg" indicate test in 10 per cent propylene glycol. The terms s/2 and s/10 refer to tests at one-tenth and one-half saturation, respectively. These results give a total of 20 active substances found from the 151 tested without the aid of solvents, about 13 per cent of those tried. This type of screening procedure is efficient in that it eliminates from further consideration about 90 per cent of substances selected at random. Other primary screening methods have involved either the rate of formation of acid by mixtures of sugar and saliva or the determination of the calcium- dissolving power of saliva-sugar mixtures for powdered tooth enamel. The efficiency of the saliva-sugar screening procedures appears to be low since nearly half the compounds tested in one study gave inhibitory effects at concentrations lower than 0.025 per cent (11). That study reported ac- tivity from six substances which we have also tried. We agree with their finding of inhibition by decylamine and dodecylamine, but did not find ac- tivity for the other four amines at concentrations four to ten times as great.

ENZYME INHIBITORS FOR DENTIFRICES 273 Possibly the discrepancy arises from the fact that the saliva-sugar tests do not indicate either the ability of a substance to penetrate a plaque or to be retained by a plaque. These amines are presented as examples of progress with our Inhibitor Survey Program. Since January, 1953, 1400 compounds have been sent us by over 60 organizations. About 140 substances have been found to have inhibitory properties greater than 50 per cent under certain conditions of testing. There are active substances among aldehydes, ketones, acids, amides, halogen derivatives, quaternary nitrogen compounds, sulfur com- pounds, and inorganic substances and various combinations of the above. Research directors of dentifrice companies sometimes appear disturbed be- cause of the number and variety of effective substances, and the total cost of submitting all of these to toxicity evaluation. Many compounds would be ruled out because of toxicity, but the cost of clinical trial of those that could be used might still be astronomical. In our opinion all of these amines and the other active substances should be subjected to further evaluation, using as guides a series of screening pro- grams, each somewhat more complex and more exacting than the one be- fore. The approach we wish to suggest is based on four assumptions: (1) that there is at present no substitute for a full-scale, thorough clinical trial in proving whether or not a dentifrice will actually inhibit dental caries, (2) that the most expensive research is the clinical trial which gives negative results, (3) that there are enough potential inhibitors available to justify use of the least expensive means for eliminating the majority of substances, and (4) that the risk of negative results should be kept as low as possible by using only those compounds which are rated highly by all recognized types of screening methods. Let us assume that each of the major dentifrice companies has a budget that will permit starting one clinical study each year. If 100 new active compounds come to tl•e research director's attention each year, his problem is how to pick the best non-toxic compound in time for the starting date of the clinical trial. Toxicity tests are not the most efficient secondary screen because of their cost and time required to get answers. It is more efficient to screen for inhibitory activity under the special con- ditions of dentifrice use. One special condition of dentifrice use is the short time of contact between dentifrice and inaccessible plaques, which amounts to only one to three minutes. Our testing procedure can be modified to give a contact of this duration rather than the usual thirty-minute contact. We believe that about two-thirds of any list of 100 could be eliminated because of sluggishness in penetrating salivary sediment. If the compounds were incorporated into dentifrice for test in a short contact study, information would automatically be obtained on the compatibility of a compounds ac- tion with the dentifrice components. Compounds which show enough