1955 SEMINAR DISCUSSION 271 in my opinion, this would have made a great impression with the public had the company come out and said it was the first to use the products of the atomic age to develop a better product. But they did not do it. Obviously I am prejudiced, I suppose, but I certainly feel there is great promotional capital to be made in such situations. I can prove my point to some extent in the case of the Accu-ray. A couple of months ago there was a conference on atomic energy in Switzerland. I helped organize an industrial exhibit of products that were for sale. The American Machine and Foundry Company makes cigarette machines and also makes the beta density gauge used on these machines. It decided to include in its large exhibit this density gauge. What happened? That cigarette machine with its Accu-ray was the star performer in the U.S. show. The American Machine and Foundry Company had mechanical hands which picked up cigarettes and gave them to the visitors, who walked off smoking. No one asked, "Is this cigarette radioactive?" The promotion branches of your industry have been slower than you people in the technical and development lines in the utilization of atomic energy. I believe a seminar of this kind is of immense help. I hope it will stimulate a lot of you to go back to your companies and develop radiation techniques of your own. But when a new product results don't let your management and the sales division of your company shy away from using the sales power of the atom and thus miss an opportunity to put your prod- uct ahead of everybody else's. I am sure that's the reason you and your company are in business. MARTIN KUNA (Bristol-Myers Products Division, Hillside 5, N.J.) The problems of the cosmetic industry are much different from others in that the things which the cosmetic industry has to work with, namely, the skin, hair and teeth, are much more diverse in nature. These properties vary with different animal species, within a single species, with individuals of a species and finally also on the individual. The use of radioisotopes to help solve some of the problems presents a challenge as to the source material and reproducibility of results. At the present time, in order to initiate a study utilizing radioisotopes on the skin, hair or teeth, a statistician must design the experiment in conjunction with the radio chemist so that the results may be analyzed statistically. Natu- rally, this means a large number of samples and readings. The cosmetic industry will use the results obtained from these radio- isotope experiments in its advertising campaigns only if and when the re- suits are-statistically significant to substantiate claims.

272 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Our interest in isotopes was aroused by the General Electric Company's Silicone Division. Dr. Leung at the University of Pittsburgh has been using silicones as protective films against acid attack on teeth in vitro. So with the cooperation of G. E., a silicone oil with a radioactive C TM was synthesized, and incorporated into a toothpaste at a concentration of 1.7 per cent. The activity of the oil was about 0.5 microcurie per milligram. Extracted human teeth were brushed with the paste and then brushed with water. This was repeated three more times. The teeth retained the radioactive silicone to an extent which calculated to be three mono- molecular layers deep. (The radioactivity was about three times back- ground.) We were encouraged by these in vitro results, and decided to test the silicone in vivo. Miniature pigs and mongrel dogs were anaesthetized and their teeth were brushed with the radioactive silicone paste thirty seconds for each quadrant. After rinsing with water, teeth were extracted at various times up to forty-eight hours. The extracted teeth were mounted in planchets, and the radioactivity was determined. In order to correlate radioactivity with surface area, photographs (about 3 X enlargements) of the planchets with the mounted teeth were taken, and printed through a tracing of millimeter cross section paper. The squares presented by the tooth surface to the Geiger tube were then counted. The results which are preliminary and not statistically significant show that dog's teeth retained the silicone to a very small degree (the most active tooth had only eight counts per minute per square centimeter after twenty- four hours). The teeth extracted immediately showed a low order of activity of about 25 cts./min./cm. 2. It was observed that molars differed from bicuspids and that the buccal surface of a tooth differed from the lingual surface. In pigs, the initial radioactivity on the teeth was only about 3 cts./min./cm. 2 and was not detectable after six hours. Not only do the different faces of the tooth differ in their ability to ab- sorb and retain radioactive substances, but the age of the tooth since erup- tion also plays a part. If the four first molars of an animal are considered, a difference of one week in the eruption time would affect the rate of adsorption. The earlier erupting tooth is more resistant to adsorption and penetration of substances. The proximity of the saliva ducts to the teeth is different in the upper jaw than in the lower jaw so that ehe radioisotope-labeled substance may be washed away faster from one surface than from another in the same mouth. Carious teeth adsorb materials much more readily than sound ones as was already mentioned by Dr. Nelson so that the condition of the tooth must also be noted. The work will continue, and I am sure that adequate samples of tooth