A Sem Study Comparing Cavity Preparations Done With Air Abrasion And Conventional Authors: *Prof. Alcione Scur (Presenter); ** Fernando Bizzi; Eduardo Reston*** (Department Of Restorative Dentistry – Lutheran University Of Brazil) The air abrasion technique has been available for the past years, however high-speed hand-pieces keep the leadership on dentist’s choice for cavity preparations.   Since 1985, all technologies have been applied towards a more conservative dentistry, preserving as much as possible all the sound tissue available in the cavity. The concept of preservation became possible because of the incoming of new materials, commonly named adhesive materials.   For this study, twenty freshly extracted molars were used, divided in two groups of ten teeth each. In the first group, class I cavities, standardized, were prepared using a 330 carbide bur. In the second group, class I cavities, as in group I, were prepared using the air abrasion system.   After cavity preparation, cavities were cleansed and conditioned with 37% phosphoric acid for 15 seconds. Acid etching were applied to remove the smear layer, and to improve the visualization of the surface of the ultra structure of enamel and dentin.   Comparative analysis were done using SEM to determine the possible differences caused by the two applied systems.   Referencias Bibliográficas Black, RB. Airabrasive: Some Fundamentals. JADA 1950:41(6) : 701-10 Goldberg, MA. Airabrasive: Patients reactions. J.Dent.Res. 1952:31(49: 504-5 Los, AS, Barkmeier, W.W. Effects os Dentin Air Abreasion with aluminum Oxide and Hidroxyappatite on Adesive Bons Stenrgth. OPER. Dent. 1994, 19, 169-175. Roeder, L.B.., Berry, E.A., III, You, C. Powers, J.M. Bond Strength of composite to air abraded Enamel and Dentin. Opert. Dent. 1995, 20, 186-190,. Rinaudo P.J., Cochran M.ª, Moore B.K. The effect of air abrasion on Shear bond Strength to dentin whith dental adhesives. Opert. Dent. 1997,22, 254-259.