The anti-adherence activity and bactericidal effect of microparticulate silver additives in composite resin materials Ralf Bu ¨ rgers a, *, Andreas Eidt b , Roland Frankenberger c , Martin Rosentritt a , Helmut Schweikl b , Gerhard Handel a , Sebastian Hahnel a a Department of Prosthetic Dentistry, Regensburg University Medical Centre, 93042 Regensburg, Germany b Department of Operative Dentistry and Periodontology, Regensburg University Medical Centre, Germany c Dental Clinic 1 – Operative Dentistry and Periodontology, University of Erlangen-Nuremberg, Germany 1. Introduction The initial adhesion of specific oral bacteria to tooth surfaces or artificial dental substrata is both the primary and the essential prerequisite for the development of cariopathogenic biofilms. 1 Within the complex formation of such biofilms, Streptococcus mutans is primarily responsible for the initiation of tooth decay as well as for the progression of an established lesion. Thus, S. mutans is regarded as a major etiological agent of dental caries. 2,3 Secondary caries under and around archives of oral biology 54 (2009) 595–601 article info Article history: Accepted 14 March 2009 Keywords: Silver Antibacterial Adherence Streptococcus mutans Resin composite abstract Objective: Resin composite materials tend to accumulate microorganisms and dental pla- que, which in turn may induce secondary caries around adhesive restorations. The aim of the present in vitro study was to evaluate the antibacterial activity of a resin composite material loaded with silver microparticles against Streptococcus mutans. Design: Circular specimens (10.0 mm in diameter) of a resin composite matrix loaded with two different concentrations of a silver additive (Comp0.3: 0.3%; Comp0.6: 0.6%) and one unloaded reference composite matrix (Comp0: 0%) were made. Surface roughness R a was assessed by perthometer measurements and hydrophobicity according to water contact angles was determined by computerized image analysis. The specimens were incubated in a S. mutans suspension (1 h, 37 8C) and adhering streptococci were quantified by using a biofluorescence assay (Alamar blue/Resazurin). Additionally, the viability of adhering bac- teria was assessed by live/dead cell labelling in combination with fluorescence microscopy. Results: Statistically significant differences between the median water contact angles of Comp0 (66.38), Comp0.3 (76.78), and Comp0.6 (89.48) were observed ( p < 0.001). A three- to fourfold higher amount of adhering S. mutans was found on reference Comp0 (12,093 relative fluorescence units) than on Comp0.3 (4258 rfu) and Comp0.6 (3292) ( p < 0.001 for both). Significantly higher percentages of dead cells than on Comp0 (0.5%) were found on Comp0.3 (6.1%) and on Comp0.6 (10.1%) ( p < 0.001 for both). Conclusions: The addition of microparticulate silver to a resin composite material increased the surface hydrophobicity and reduced the number of adhering streptococci. Simulta- neously it increased the percentage of dead and inactive cells on the composite surface. Thus, silver additives seem to demonstrate anti-adherence activity as well as a bactericidal effect. # 2009 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +49 941 944 6059; fax: +49 941 944 6171. E-mail address: ralf.buergers@klinik.uni-regensburg.de (R. Bu ¨ rgers). available at www.sciencedirect.com journal homepage: www.intl.elsevierhealth.com/journals/arob 0003–9969/$ – see front matter # 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.archoralbio.2009.03.004