ORIGINAL ARTICLE Adhesion of multimode adhesives to enamel and dentin after one year of water storage Paulo Moreira Vermelho 1 & André Figueiredo Reis 2 & Glaucia Maria Bovi Ambrosano 3 & Marcelo Giannini 1 Received: 15 January 2016 /Accepted: 26 September 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract Objectives This study aimed to evaluate the ultramorphological characteristics of tooth–resin interfaces and the bond strength (BS) of multimode adhesive systems to enamel and dentin. Methods Multimode adhesives (Scotchbond Universal (SBU) and All-Bond Universal) were tested in both self-etch and etch-and-rinse modes and compared to control groups (Optibond FL and Clearfil SE Bond (CSB)). Adhesives were applied to human molars and composite blocks were incre- mentally built up. Teeth were sectioned to obtain specimens for microtensile BS and TEM analysis. Specimens were tested after storage for either 24 h or 1 year. SEM analyses were performed to classify the failure pattern of beam specimens after BS testing. Results Etching increased the enamel BS of multimode adhe- sives; however, BS decreased after storage for 1 year. No significant differences in dentin BS were noted between mul- timode and control in either evaluation period. Storage for 1 year only reduced the dentin BS for SBU in self-etch mode. TEM analysis identified hybridization and interaction zones in dentin and enamel for all adhesives. Silver impregnation was detected on dentin–resin interfaces after storage of specimens for 1 year only with the SBU and CSB. Conclusions Storage for 1 year reduced enamel BS when ad- hesives are applied on etched surface; however, BS of multi- mode adhesives did not differ from those of the control group. In dentin, no significant difference was noted between the multimode and control group adhesives, regardless of etching mode. Clinical relevance In general, multimode adhesives showed similar behavior when compared to traditional adhesive tech- niques. Multimode adhesives are one-step self-etching adhe- sives that can also be used after enamel/dentin phosphoric acid etching, but each product may work better in specific conditions. Keywords Bond strength . Transmission electron microscopy . Phosphoric acid etching . Adhesive system . Dentin . Enamel Introduction The most effective adhesion of composite resins to enamel occurs when the enamel is previously etched with 30 to 40 % phosphoric acid for 15 to 60 s before the application of a hydrophobic resin monomer [1–4]. The acid etching mod- ifies the enamel’ s surface energy by dissolving minerals and creating microporosities at the interprismatic area and prism core. The resin monomers from hydrophobic resin are able to penetrate into enamel porosities and, after polymerization, produce a high-strength, durable bond [5–7]. Regarding dentin, the gold standard bonding agents for this dental structure are the three-step etch-and-rinse adhesives; however, the two-step self-etching primers also have shown good results in terms of bond strength and clinical durability [8–12]. The hydrophobic layer used after priming is important to improve the dentin sealing and increase the monomeric * Marcelo Giannini giannini@fop.unicamp.br 1 Operative Dentistry Division, Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Av. Limeira, 901, Piracicaba, SP 13414-903, Brazil 2 Department of Operative Dentistry, School of Dentistry, University of Guarulhos, R. Nilo Peçanha 81, Guarrulhos, SP 07011-040, Brazil 3 Department of Social Dentistry, Piracicaba Dental School, State University of Campinas, Av. Limeira, 901, Piracicaba, SP 13414-903, Brazil Clin Oral Invest DOI 10.1007/s00784-016-1966-1