Lasers in Surgery and Medicine 34:385–390 (2004) Comparative Study of the Dentin/Adhesive Systems Interface After Treatment With Er:YAG Laser and Acid Etching Using Scanning Electron Microscope Juliano F. Sassi, DDS, 1 Daniela T. Chimello, MS, 1 Maria C. Borsatto, PhD, 2 Silmara A.M. Corona, PhD, 1 Jesus D. Pecora, PhD, 1 and Regina Guenka Palma-Dibb, PhD 1 * 1 Department of Restorative Dentistry, Ribeira ˜ o Preto School of Dentistry, University of Sa ˜ o Paulo (USP), Av. do Cafe ´, s/n, Monte Alegre, 14040-904,Ribeira ˜ o Preto, Sa ˜ o Paulo, Brazil 2 Department of Pediatric Dentistry, Ribeira ˜ o Preto School of Dentistry, University of Sa ˜ o Paulo (USP), Av. do Cafe ´, s/n, Monte Alegre, 14040-904, Ribeira ˜ o Preto, Sa ˜ o Paulo, Brazil Background and Objectives: To assess dentin/adhesive systems interface after dentin conditioning with Er:YAG laser. Study Design/Materials and Methods: Twenty-four dentin half-disks were assigned to 3 groups: All Bond 2 (AB); Optibond Solo Plus (OP); and Clearfil Liner Bond 2V (CL), which were divided into three sub-groups, according to dentin surface treatment: Er:YAG laser; Er:YAG laser plus acid; acid solely. After the adhesive protocol, speci- mens were embedded in resin, sectioned, and prepared for SEM analysis. Each area was examined under 1,500 magnification to assess the hybrid layer. Results: Acid conditioning provided to AB and OP thick and homogeneous hybrid layer, as well as conical and uniform tags. The same pattern was observed for CL. In general, dentin treatment with laser, even when associated to acid, promoted irregular and thin hybrid layer, as well as scarce and thin tags. Conclusions: Er:YAG laser influenced the adhesive sys- tems interface, hampering hybrid layer formation. Lasers Surg. Med. 34:385 – 390, 2004. ß 2004 Wiley-Liss, Inc. Key words: conditioning; laser irradiation; microscopy; morphology INTRODUCTION Many of the restorative procedures currently used employ adhesive techniques, which are constantly being improved in order to reach effective bonding between the material and the dental substrate. The results of these techniques are cavity preparations which are more con- servative than those advocated by Black [1]. Enamel surface treatment by the acid conditioning technique, firstly proposed by Buonocore in 1955 [2], produced microscopic irregularities on the treated surface, increasing enamel area, and surface energy, readying it for the mechanical retention. When acid conditioning of enamel was introduced in dental practice, the search was focused on materials that could provide, apart from cleansing, an effective bonding to dentin, aiming to obtain the formation of micro-porosities, in a way similar to that observed on enamel [3]. However, the adhesion mechanism to dentin is far more complex than to enamel, due to the dentin tubular structure, its high water content and the presence of micro-structural patho- logical and physiological alterations, such as sclerotic and hyper-mineralized dentin [3–5]. Several studies [6–9] were developed aiming to under- stand dentin’s characteristics after cavity preparations, observing an altered surface morphology, and thus result- ing from the smear layer formation [10]. One of the alternative techniques analyzed for cavity preparation and treatment of dental structures is the laser irradiation, based on the Albert Einstein’s theory of light emission, was published in 1917 [11]. Lasers are classified according to their emitting material, which can be solid (e.g., crystals), liquid (e.g., dyes), or gas (e.g., helium–neon, CO 2 ). This device provides light emission of a definite wavelength, which associated to other parameters, such as emission mode (pulsed or continuous), irradiation time, pulse repetition rate, and power, results in different interactions with each kind of tissue. Several researchers reported the Er:YAG laser ability in selective removal of carious tissue [12,13], cavity prepara- tion [14–18], and in the dental surfaces treatment (conditioning) [19–21]. The amount of tissue removed by the Er:YAG laser, as well as the impact upon adjacent dental tissues are dependent on some factors, such as: the focal distance; a focused beam; the energy (between 200 and 500 mJ and pulse repetition rate up to 8 Hz) [12]; the amount of water in the tissue, as well as its structural Contract grant sponsor: FAPESP (Brazil); Contract grant numbers: 01/08729-2, 01/05422-3. *Correspondence to: Prof. Dr. Regina Guenka Palma-Dibb, PhD, Universidade de Sa ˜o Paulo/Faculdade de Odontologia de Ribeira ˜o Preto, Departamento de Odontologia Restauradora, Av. do Cafe ´, s/n Monte Alegre Cep: 14040-904 Ribeira ˜o Preto- SP, Brasil. E-mail: rgpalma@forp.usp.br Accepted 3 March 2004 Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/lsm.20064 ß 2004 Wiley-Liss, Inc.