Influence of surface properties of resin-based composites on in vitro Streptococcus mutans biofilm development Ionescu A, Wutscher E, Brambilla E, Schneider-Feyrer S, Giessibl FJ , Hahnel S. Influence of surface properties of resin-based composites on in vitro Streptococcus mutans biofilm development. Eur J Oral Sci 2012; 00: 000–000. © 2012 Eur J Oral Sci The aim of this in vitro study was to evaluate the influence of physicochemical surface properties of resin-based composites on Streptococcus mutans biofilm forma- tion. Specimens were prepared from each of four resin-based composites by poly- merization against Mylar strips. Half of the number of specimens received no further surface treatment, whereas the other half were subjected to a polishing treat- ment. Surface roughness (SR) and topography were assessed using profilometry and atomic force microscopy. Surface free-energy (SFE) was determined, and the chemi- cal surface composition was analysed by X-ray photoelectron spectroscopy (XPS). S. mutans biofilms were formed on the surface of the resin-based composite speci- mens for either 48 or 96 h using an artificial mouth system (AMS). Polishing caused a significant decrease in SFE, and XPS analysis indicated an increase of surface sili- con and a decrease of surface carbon. Only for Grandio was a significant increase in SR identified after polishing, which was probably related to the higher concentra- tion of filler particles on its surface. Significantly less S. mutans biofilm formation was observed on polished resin-based composites than on unpolished resin-based composites. These results indicate that the proportions of resin matrix and filler par- ticles on the surface of resin-based composites strongly influence S. mutans biofilm formation in vitro, suggesting that minimization of resin matrix exposure might be useful to reduce biofilm formation on the surface of resin-based composites. Andrei Ionescu 1 , Elisabeth Wutscher 2 , Eugenio Brambilla 1 , Sibylle Schneider-Feyrer 3 , Franz J. Giessibl 2 , Sebastian Hahnel 3 1 Department of Medicine, Surgery and Dentistry, S. Paolo Hospital, University of Milan, Milan, Italy; 2 Institute of Experimental and Applied Physics, University of Regensburg, Regensburg; 3 Department of Prosthetic Dentistry, University Medical Center Regensburg, Regensburg, Germany Sebastian Hahnel, Regensburg University Medical Center, Department of Prosthetic Dentistry, Regensburg 93042, Germany Telefax: +49–941–9446171 E-mail: Sebastian.Hahnel@klinik. uni-regensburg.de Key words: atomic force microscopy; biofilm; bioreactors; resin-based composite; Streptococcus mutans Accepted for publication June 2012 The use of resin-based composites is steadily increasing (1) as a result of their broad range of application in both anterior and posterior teeth (2), their superior aes- thetic properties (3), and their ease of use (4). Clinical studies identified secondary caries as the main reason for resin-based composite restoration failure (5–8). As secondary caries development is closely related to the presence of cariogenic biofilms in the marginal areas of dental restorations, bacterial colonization of resin-based composite surfaces plays a pivotal role in this process (9). Experimental data demonstrate that high surface roughness (SR) and, to a lesser extent, high surface free-energy (SFE) of a dental-restorative material are related to increased biofilm formation on its surface (10–12). Thus, attempts to minimize biofilm formation on resin-based composites have focused on the develop- ment of materials featuring unfavourable conditions for the adhesion and colonization of oral microorganisms, and included the development of resin-based compos- ites with low SR and SFE and high hydrophobicity (13). Resin-based composites are complex materials con- sisting of a hydrophobic resin matrix and less hydro- phobic filler particles, which implies that a resin-based composite surface is never a homogeneous interface, producing matrix-rich and filler-poor areas, as well as matrix-poor and filler-rich areas, which accounts for the topographical and chemical differences within a sin- gle resin-based composite surface. For commercially available resin-based composites, differences in resin and filler chemistry, as well as in filler size and shape, account for differences in terms of SR and surface chemistry after polishing (14–16). In addition, the pol- ishing procedure substantially modifies the physico- chemical characteristics of a resin-based composite surface by removing the matrix-rich superficial resin- based composite layers and producing a surface that is Eur J Oral Sci 2012; 1–8 DOI: 10.1111/j.1600-0722.2012.00983.x Printed in Singapore. All rights reserved Ó 2012 Eur J Oral Sci European Journal of Oral Sciences