ORIGINAL ARTICLE Effect of nanostructured zirconium dioxide incorporation in an experimental adhesive resin Camila Provenzi 1 & Fabrício Mezzomo Collares 1 & Marla Cuppini 1 & Susana Maria Werner Samuel 1 & Annelise Kopp Alves 2 & Carlos Pérez Bergmann 2 & Vicente Castelo Branco Leitune 1 Received: 26 June 2017 /Accepted: 12 December 2017 /Published online: 5 January 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Objectives The aim of this study was to evaluate the influence of nanostructured zirconium dioxide incorporation in an exper- imental adhesive resin. Methods ZrO 2 particles were characterized by X-ray diffraction (XRD), micro-Raman spectroscopy and Brunauer–Emmett– Teller (B.E.T). Experimental adhesive resins were formulated with 0, 0.5, 1, 4.8, and 9.1% ZrO 2 in weight. The adhesives were evaluated based on degree of conversion (DC), radiopacity, softening in solvent and microtensile bond strength (μTBS) 24 h and after 1 year of aging. Mineral deposition at the hybrid layer was assessed with micro-Raman spectroscopy at the baseline and after 14 days. Results XRD showed monoclinic and tetragonal phases of ZrO 2. particles. B.E.T data revealed a surface area of 37.41 m 2 /g, and typical chemical groups were shown on the Raman spectra . The addition of ZrO 2 did not influence the radiopacity. The addition of 4.8% and 9.1 wt.% ZrO 2 showed higher initial hardness with increased softening in solvent (P < 0.05) and promoted mineral deposition at the dentin interface. DC was significantly increased in the group with 1% ZrO 2 (P < 0.05). The μTBS test showed difference on the group with 9.1 wt.% of ZrO 2 , with a significant reduction after aging. Conclusion The incorporation of ZrO 2 promoted mineral deposition on the adhesive interface and the addition of 1 wt.% caused a significant increase on the DC without compromising the other physicochemical characteristics, which may prove promising for the development of new dental adhesive systems. Clinical relevance The mineral deposition on the hybrid layer can result in a longer stability of the adhesive, thus delaying the hydrolytic degradation. Keywords Nanostructures . Zirconium dioxide . Dentin bonding agents Introduction In the last decade, the role of the adhesive system components in the adhesion process has been extensively studied [1–3]. A stable bonding of dental adhesives to tooth substrates relies on the mechanical and chemical features of the polymeric material [4]. However, some concerns regarding the hybrid layer degra- dation over time, nanoleakage and longevity of materials in the oral environment remain issues to dentin adhesion [5–9]. The development of polymeric materials with better clinical behav- ior has been the subject of research and of great interest in the scientific community and dental materials industry [10–13]. Several studies have incorporated fillers, such as hydroxy- apatite [14], niobium pentoxide [4], tantalum oxide [15], and titanium dioxide [16] into the organic matrix of adhesive resins and improved mechanical properties have been observed. The addition of inorganic particles in adhesive resins aims to de- crease the degradation over time [17, 18] and, as a consequence, to reduce the composite structural defects that could lead to failures. The incorporation of fillers in adhesives can also lead to a hybrid layer with greater stability, thus contributing to the longevity of the restorative treatment [19]. * Vicente Castelo Branco Leitune vicente.leitune@ufrgs.br 1 Dental Materials Laboratory, School of Dentistry, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2492 - Rio Branco, Porto Alegre, RS, Brazil 2 Laboratory of Ceramic Materials, Universidade Federal do Rio Grande do Sul, Avenida Osvaldo Aranha 99, room 709 - Centro, Porto Alegre, RS, Brazil Clinical Oral Investigations (2018) 22:2209–2218 https://doi.org/10.1007/s00784-017-2311-z