RESEARCH ARTICLE Effect of additional polishing methods on the physical surface properties of different nanocomposites: SEM and AFM study Giovanna de Fátima Alves da Costa 1 | Ana Carla Bezerra de Carvalho Justo Fernandes 1 | Lenise Anand de Oliveira Carvalho 2 | Aldenora Cardoso de Andrade 1 | Isauremi Vieira de Assunção 1 | Boniek Castillo Dutra Borges 1 1 Department of Dentistry, Federal University of Rio Grande do Norte (UFRN), Natal, Rio Grande do Norte, Brazil 2 Federal University of Rio Grande do Norte (UFRN), Natal, Rio Grande do Norte, Brazil Correspondence Boniek Castillo Dutra Borges, Av. Senador Salgado Filho, 1787, Lagoa Nova, Natal 59056-000, Rio Grande do Norte, Brazil. Email: boniek.castillo@gmail.com Review Editor: Prof. Paul Verkade Abstract This evaluated the arrangement of filler particles in depth of nanocomposites, and surface roughness, wettability, microtopography, and micromorphology following additional polishing step. Forty samples of each composite tested [Filtek Z350XT (FZ), IPS Empress Direct (IP)] were fabricated and finished/polished/additionally polished using one of the following methods (n = 10/group): no finishing/polishing (NFP), Sof-Lex Pop-On + no additional polishing (SP), Sof- Lex Pop-On + Astropol rubber polisher (SP+A), and Sof-Lex Pop-On + felt disc with polishing paste (SP+FP). Surface roughness (Ra) and contact angles were measured using a profilometer and goniometer, respectively. Microtopography and micromorphology were evaluated using atomic force microscopy and scanning electron microscopy, respectively. Ra and contact angle data were examined by two-way analysis of variance and Tukey's test (p < .05). Organic matrix, lower and larger filler particles were disposed in depth. Mean Ra values were lowest and contact angles were smallest in the NFP group for both composite resins. SP+A and SP+FP decreased mean Ra in comparison with SP for FZ, whereas only SP+FP decreased mean Ra in comparison with SP for IP. Only SP+FP increased contact angles in comparison with SP for FZ, whereas con- tact angles in the SP+A, SP+FP, and SP groups were similar for FZ. Both composites presented more uniform topography and smother surfaces following SP+A and SP+FP in comparison with SP. Therefore, additional polishing improved surface smoothness and decreased wettability of the composite resins studied. SP+FP produced smoother and less wettable surfaces for FZ and IP. KEYWORDS composite resin, dental polishing, surface roughness, wettability 1 | INTRODUCTION Technological progress in the development of composite resins has resulted in improvements in the physical, mechanical, and esthetic properties of these materials. Changes in composite resins, especially in the type, distribution, and size of filler particles (Kumari, Bhat and Bansal, 2016), have occurred, and nanosized fillers have been intro- duced to improve the mechanical properties of these resins (Aytac et al., 2016). However, a smooth surface is an integral requirement for the success of composite restorations, as a rough surface may allow bacterial adhesion, promoting secondary caries development, and affect the color properties of esthetic restorations (Kumari, Nagaraj, Siddaraju and Poluri, 2015). The use of different finishing/polishing systems based on alumi- num oxide, diamond, silicon carbide, and silicon dioxide abrasives has been investigated in attempts to achieve surface smoothness in com- posite resins (Aytac et al., 2016). Previous investigations showed that additional polishing with a felt disc moistened with polishing paste after conventional finishing/polishing with aluminum oxide discs may improve the smoothness of nanocomposite surfaces (Justo- Received: 6 June 2018 Revised: 6 September 2018 Accepted: 7 September 2018 DOI: 10.1002/jemt.23147 Microsc Res Tech. 2018;1–7. wileyonlinelibrary.com/journal/jemt © 2018 Wiley Periodicals, Inc. 1