Effect of In-office Bleaching Agents on the Surface Roughness and Morphology of Different Dental Composites: An AFM Study EDUARDO VARANDA, 1 MA  IRA DO PRADO, 2 * RENATA A. SIM ~ AO, 3 AND KATIA REGINA HOST  ILIO CERVANTES DIAS 4 1 Department of Restorative Dentistry, State University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil 2 Department of Dental Clinic, Division of Endodontics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 3 Department of Metallurgic and Materials Engineering, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 4 Department of Restorative Dentistry, State University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil KEY WORDS atomic force microscopy; bleaching; hydrogen peroxide; dental composites; roughness ABSTRACT The aim of this study was to evaluate, using atomic force microscopy, the effect of two different bleaching agents on the modification of dental composites materials. This modifi- cation will be judged by analyzing the variation of surface roughness and surface morphology of two different composites: one containing nanoparticles and other consisting of microhybrid resin. The bleaching was performed by using two different concentrations of hydrogen peroxide: HP Blue (20% hydrogen peroxide) and Whiteness HP Maxx (35% hydrogen peroxide). Disks of Esthet X and Filtek TM Z350 composites were used. Atomic force microscopy was used for analy- ses of the same place of the sample before and after treatment. A total of 12 analyses were per- formed per group (n 5 12). The samples were analyzed qualitatively by evaluating morphological changes in the images and quantitatively by using roughness parameters (Ra). Data were ana- lyzed statistically using Kruskal–Wallis, Mann–Whitney, and Friedman tests (P < 0.05). Changes were observed both qualitatively and quantitatively only in the groups where Esthet X resin was used. The use of hydrogen peroxide bleaching agents caused changes only in the sur- face of microhybrid composites, with no changes being observed in the composite containing nanoparticles. Despite being even significant, these alterations are clinically slight and can be eliminated by polishing them. Microsc. Res. Tech. 76:481–485, 2013. VC 2013 Wiley Periodicals, Inc. INTRODUCTION Dental bleaching is one of the most commonly used dental esthetic clinical procedures. This procedure is non-invasive, being considered an effective and safe treatment (Dadoun et al., 2003; Moraes et al., 2006; Kielbassa, 2006; Ulukapi, 2007). When resin composite restorations are clinically used, they are frequently removed after bleaching (Attin et al., 2004; Taher, 2005). However, when the restorative material is placed in distal areas of premolars and molars where there is no esthetic compromise with respect to resin color change after bleaching, many dentists dispense with removing the restoration (Wattanapayungkul et al., 2004; Wang et al., 2011). Different dental resin composites are proposed for tooth restoration. Microhybrid composites are most widely used as they provide optimal mechanical and physical properties combined with good polishing prop- erties (Janus et al., 2010). With the application of nanotechnology to dental composites, nanocomposites have also been proposed as restorative material. In fact, they show favorable mechanical properties, which are at least equal to or even superior to those of hybrid materials (Attar, 2007; Beun et al., 2007; Lohbauer et al., 2006; Mesquita et al., 2006; Papadogiannis et al., 2008; Rodrigues Junior et al., 2007). The consequences of bleaching resin-based materi- als can vary according to resin and bleaching gel compositions, as well as the frequency and duration of the exposure (Attin et al., 2004; Wang et al., 2011). The consequences already observed include changes in micro-hardness and roughness (Al-Salehi et al., 2006; Arcari et al., 2005; Bailey et al., 1992; Cehreli et al., 2003). An increase in superficial roughness is clinically relevant as this results in extrinsic staining, bacteria adhesion, plaque maturation, and periodontal disease, irrespective of etiological factors (Mor et al., 1998; Steiberg et al.,1999). Atomic force microscopy (AFM) is a well-established and documented tool for structural characterization of materials. It offers the opportunity to image the three- dimensional surface topography with high spatial reso- lution under a wide variety of conditions. Also, this is a nondestructive technique, which offers the possibility *Correspondence to: Maıra do Prado, Department of Dental Clinic, Division of Endodontics, Federal University of Rio de Janeiro, Rua Prof. Rodolpho Paulo Rocco 325/2  andar, Ilha da Cidade Universit aria, Rio de Janeiro, RJ, Brazil. E-mail: mairapr@hotmail.com Received 26 February 2012; accepted in revised form 17 January 2013 Contract grant sponsors: the Brazilian agencies, FAPERJ, CNPq. DOI 10.1002/jemt.22190 Published online 15 February 2013 in Wiley Online Library (wileyonlinelibrary.com). V VC 2013 WILEY PERIODICALS, INC. MICROSCOPY RESEARCH AND TECHNIQUE 76:481–485 (2013)