An innovative approach to treating dental decay in children. A new anti-caries agent Andre ´a Gadelha Ribeiro Targino • Miguel Angel Pelagio Flores • Valdeci Elias dos Santos Junior • Fabiana de Godoy Bene ´ Bezerra • Hilzeth de Luna Freire • Andre ´ Galembeck • Aronita Rosenblatt Received: 4 December 2013 / Accepted: 19 April 2014 Ó Springer Science+Business Media New York 2014 Abstract The aim of this work is to evaluate the anti- microbial and cytotoxic activity of a formulation contain- ing silver nanoparticles and chitosan, provisionally called nano silver fluoride (NSF), against Streptococcus mutans in comparison to chlorhexidine and silver diamine fluoride (SDF). The product was characterised by transmission electron microscopy and UV–Vis absorption spectroscopy. The minimum inhibition concentration (MIC) was evalu- ated by the spectrophotometric microdilution method and turbidity. The minimum bactericide concentration (MBC) was evaluated in brain heart infusion plates, and cytotox- icity was evaluated by haemolytic activity. The MIC and MBC for NSF were, respectively, 33.54 ± 14.52 and 50.32 lg/mL; for SDF were 33.33 ± 14.43 and 50.0 lg/ mL, respectively; and for CHX were 3.3 ± 0.5 and 6 lg/ mL, respectively. An ANOVA for MIC gave P = 0.032, and for MBC P = 0.035. The cytotoxic effect of NSF compared to SDF demonstrated a statistically significant difference in the MIC value (t test P \ 0.05). The NSF formulation may be effective against S. mutans with much lower doses, may have lower toxicity than SDF, and may not stain teeth. 1 Introduction The incidence of caries has declined in the industrialised world and also in developing countries [1–5]; however, the data are still worrisome, and globally the greatest burden of oral diseases lies on disadvantaged and poor populations [6]. Fluoride agents of different concentrations have been shown to be effective in reducing caries [7–10], and silver diamine fluoride (SDF) has been proven to more effec- tively prevent caries [11] than fluoride varnish and water [12, 13]. However, SDF stains caries tissues dark brown [12, 14]. The use of SDF in poor communities may increase the access of children to dental care, but it may also stigmatise those individuals by causing their teeth to be stained black. Dentists and patients are familiar with the black surfaces of cavities filled with silver amalgam, reported earlier by [15, 16], who directly applied silver nitrate to caries lesions. Previous studies have described the bactericidal and bacteriostatic effects of silver nanoparticles measuring 25 nm [17], 8.4, 16.1 and 98 nm [18], and 5, 15 and 55 nm [19] in Streptococcus mutans obtained from ATCC (American Type Cultural Collection). The results indicate that the antibacterial activity of silver nanoparticles increases as the particle size decreases [20, 21]. Chitosan, a biocompatible, biodegradable and non- toxic biopolymer obtained by the deacetylation of chitin, a polysaccharide from shrimp shells, has antibacterial activity against a broad spectrum of bacteria [22], including S. mutans and S. sanguinis (formerly S. sanguis) [23]. Currently, sufficient evidence exists to support the use of chitosan and silver nanoparticles as antibacterial agents [24]. Both materials have demonstrated antimicrobial activity, A. G. R. Targino (&) Á V. E. dos Santos Junior Á F. de Godoy Bene ´ Bezerra Á A. Rosenblatt Department of Paediatric Dentistry, Faculty of Dentistry, University of Pernambuco, Av: Gal. Newton Cavalcanti n8 1650, Camaragibe, PE CEP 54 753-020, Brazil e-mail: andreadoutorado@gmail.com M. A. P. Flores Á A. Galembeck Department of Chemical Sciences, Federal University of Pernambuco, Recife, Brazil H. de Luna Freire Department of Biological Science, Faculty of Biological Science, Federal University of Paraı ´ba, Joa ˜o Pessoa, Brazil 123 J Mater Sci: Mater Med DOI 10.1007/s10856-014-5221-5