CONVERSION OF VITAMIN E ACETATE TO VITAMIN E 161 absent on the skin surface as well as in the horny layer. These findings are in accordance with Landmann (15), who reported extracellular esterases being shed by lameliar bodies in the epidermis. As demonstrated, the galenic formulation of the vitamin E acetate, as of lipophilic substances in general, is crucial for its skin availability. Beyond the physical and chemi- cal properties of the active, the type of formulation and the phase in which the active is dissolved also determine its fate and the biological activity. In the present study, more than 95% of vitamin E acetate remained either on the skin surface or deposited in the horny layer when applied in an oil. In contrast, when applied in the water phase, up to 50% of vitamin Etot• l was made available to the viable skin, the zone of cosmetic interest. In the best case, up to 20% of the initial amount of vitamin E acetate was recovered as free vitamin E. Controversial findings on the activation of the pro-drug may well be due to differences in formulating vitamin E acetate (7-11). REFERENCES (1) A. Igarashi, M. Uzuka, and K. Nakajima, The effects of vitamin E deficiency on rat skin, Br. J. Dermatol., 121, 43•49 (1989). (2) J. Fuchs, M. Huflejt, L. M. Rothfuss, D. S. Wilson, G. Carcamo, and L. Packer, Acute effects of near ultraviolet and visible light on the cutaneous antioxidant defense system, Photochem. Photobiol., 50, 739-744 (1989). (3) M.M. Rieger, Oxidative reactions in and on skin: Mechanism and prevention, Cosmet. Toiletr., 108, 43-55 (1993). (4) P. Mayer and W. Pittermann, The effects of vitamin E on the skin, Cosmet. Toiletr., 108, 99-109 (1993). (5) V. Kagan, E. Witt, R. Goldmann, G. Scita, and L. Packer, Ultraviolet light-induced generation of vitamin E radicals and their recycling. A possible photosensitizing effect of vitamin E in the skin, Free Rad. Res. Comm., 16, 51-64 (1991). (6) M. Rangarajan and J. Zatz, Skin delivery of vitamin E,.]. Cosmet. Sci., 50, 249-279 (1999). (7) E. P. Norkus, G. F. Bryce, and H. N. Bhagavan, Uptake and bioconversion ofalpha-tocopheryl acetate to alpha-tocopherol in skin of hairless mice, Photochem. Photobiol., 57, 613-615 (1993). (8) K. Tojo and A.-R. C. Lee, Bioconversion of a provitamin to vitamins C and E in skin, J. Soc. Costa. Chem., 38, 333-339 (1987). (9) J. R. Trevithick and K. P. Mitton, Topical application and uptake of vitamin E acetate by the skin and conversion to free vitamin E, Blochem Mol. Biol. Intl., 31,869-878 (1993). (10) H. Gensler, M. Aikin, Y-M. Peng, and M. Xu, Importance of the form of topical vitamin E for prevention of photocarcinogenesis, Nutr. Cancer, 26, 183-191 (1996). (ll) D. S. Alberts, R. Goldmann, M.-J. Xu, R. T. Dorr, J. Quinn, K. Welch, J. Guillen-Rodriguez, M. Aickin, Y.-M. Peng, L. Loescher, and H. Gensler, Disposition and metabolism of topically adminis- tered alpha-tocopherol acetate: A common ingredient of commercially available sunscreens and cos- metics, Nutr. Cancer, 26, 193-201 (1996). (12) B. Herzog, K. Soreruer, W. Baschong, and J. Roeding, Nanotopes, a surfactant resistant carrier system, SOeFWJournal, 124, 614-623 (1998). (13) H. Maibach, Percutaneous absorption,.]. Am. Coll. Toxicol., 8, 803-813 (1989). (14) C.W. Artmann, In vitro percutaneous absorption into human skin, Fund. Appl. Toxicol., 28, 1-5 (1996). (15) L. Landmann, The epidermal permeability barrier, Anat. Emb•yol., 178, 1-13 (1988).

Cosmet. Sd., 52, 163-167 (May/June 2001) Abrasiveness evaluation of silica and calcium carbonate used in the production of dentifrices I. M. C. CAMARGO, M. SAIKI, M. B. A. VASCONCELLOS, and D. M. ]tVILA, Instituto de Pesquisas Energdticas e Nucleares, Centro de Qu/mica e Meio Ambiente, IPEN/CNEN-SP, Caixa Postal 11049, ZIP 05422-970, S•o Paulo, SP, Brazil. Accepted for publication March 15, 2001. Synopsis Our purpose was to apply a radiometric method to an abrasivehess evaluation in samples of silica and calcium carbonate used as an abrasive in a dentifrice, to help in a prudent selection of materials by dentifrice producers. The results of RDA (radioactive dentin abrasion) abrasivehess indices obtained for these com- pounds varied from 136 to 19. The relative standard deviations of these RDA results varied from 5.9% to 11.8%, showing a good precision in the method. Also, the results obtained indicated that the abrasivehess indices increase with the particle size of the material. A comparison between different abrasives with similar particle sizes showed that silica presents higher RDA values than calcium carbonate. INTRODUCTION Dentifrices are cosmetics used with toothbrushes to clean tooth surfaces to prevent the accumulation of stains and plaques. Therefore, they should present an appropriate abra- siveness to clean the teeth, but without causing wear. Consequently, knowledge of the characteristics of the abrasive agents used for dentifrice manufacturing is of interest to industries in order to obtain appropriate products for perfect oral hygiene without causing wear to the teeth or restorative materials. The abrasives commonly utilized in the dentifrices produced in Brazil are silica and calcium carbonate, and their quantities in dentifrices vary from 30% to 48% in mass (1,2). Among several articles related to the use of abrasives in the dentifrices, one by Boer et al. (3) evaluated the wear caused by abrasives through the method of surface profilometry and verified the correlation between abrasivehess and the particle size of abrasives. Also, these authors obtained different abrasivehess values for distinct abrasives presenting similar particle sizes, that is, the abrasive AI(OH) 3 of 7-1•m particle size showed greater abrasivehess than that presented by CaCO 3 with 8-1•m particle size. This difference in abrasivehess may be attributed to the distinct particle hardness of these two agents. Address all correspondence to M. Saiki. 163