_______________________________________________________________________________________________________________________________________________________________ Research Article _______________________________________________________________________________________________________________________________________________________________ Indirect resin composite restorations bonded to dentin using self-adhesive resin cements applied with an electric current-assisted method VALERIA BISINOTO GOTTI, DDS, MSC, VICTOR PINHEIRO FEITOSA, DDS, MSC, PHD, SALVATORE SAURO, DDS, PHD, LOURENÇO CORRER-SOBRINHO, DDS, MSC, PHD & AMERICO BORTOLAZZO CORRER, DDS, MSC, PHD ABSTRACT: Purpose: To evaluate the effects of an electric current-assisted application on the bond strength and interfacial morphology of self-adhesive resin cements bonded to dentin. Methods: Indirect resin composite build-ups were luted to prepared dentin surfaces using two self-adhesive resin cements (RelyX Unicem and BisCem) and an ElectroBond device under 0, 20, or 40 A electrical current. All specimens were submitted to microtensile bond strength test and to interfacial SEM analysis. Results: The electric current-assisted application induced no change (P> 0.05) on the overall bond strength, although RelyX Unicem showed significantly higher bond strength (P< 0.05) than BisCem. Similarly, no differences were observed in terms of interfacial integrity when using the electrical current applicator. (Am J Dent 2014;27:233-236). CLINICAL SIGNIFICANCE: The results indicated that the application of the tested self-adhesive resin cements with an electric current-assisted method did not impair nor improve the bond strength of these materials to dentin. : Dr. Valeria Bisinoto Gotti, Division of Dental Materials, FOP-UNICAMP, 901 Limeira Ave, Piracicaba, SP, CEP 13414-903, Brazil. E-: val_bisinoto@hotmail.com Introduction Esthetic indirect restorations require durable enamel and dentin bonding with resin cements. 1 Self-adhesive resin cements simplify the application of conventional resin-based cements which usually require a separate application of dental bonding agents. 2 No dentin/ enamel surface pre-treatment is needed when using self-adhe- sive luting cements due to the presence of acidic functional monomers which allow simultaneous demineralization and infiltration of the resin co-monomer blend. 3,4 Thus, due to the constant evolution of these materials, their performance in achieving reliable adhesion, adequate mechanical properties and low water sorption/solubility is of interest to clinicians and researchers. 5,6 An intimate contact (i.e. wettability) between the adhesive resin and the dental hard tissues plays an important role in establishing effective bonding, both using dental adhesives and resin luting cements. 7 In this regard, some studies revealed the improvements attained by using electric current-assisted devices (ElectroBond a ) to apply etch-and-rinse and self-etch dental adhesive on dentin. 7-11 This latter category of adhesives contains similar functional monomers undertaken in the self- adhesive resin cements which could likely result in similar improvements by using ElectroBond. The rationale behind the application of adhesives assisted by electric current is based on the enhancement of resin infiltration into partially demineralized dentin due to improved dentin wettability. 7 In fact, this electric current-assisted application of dental adhesives has shown significant advances on direct bonded restorations such as longer-lasting durability of the bond strength. 7,8,10 The hybridization quality plays an important role on the long-term stability of bonded restoratives 8 and an intimate contact between resin cement and dentin with electric current could contribute to a better interaction of the material to the substrate. Nevertheless, such a device has never been evaluated in assisting the application of resin cements to lute indirect restorations, such as inlays, onlays and veneers onto dentin. Therefore, this study evaluated the effects an electric current- assisted application of self-adhesive resin cements had on the bond strength and interfacial morphology of self-adhesive resin cements bonded to dentin. The two hypotheses tested were that (1) the application of electric current may improve the dentin bonding performance of self-adhesive resin cements; and (2) the morphology of the bonded interface was different with the use of electric current. Materials and Methods Specimen preparation - Forty extracted human molars were obtained under approval of the institutional ethics committee of The University of Campinas, Piracicaba, Brazil (protocol 53/2012) and stored in 0.5% chloramine/water solution at 4°C for no longer than 4 months. The roots were removed 2 mm beneath the cemento-enamel junction (CEJ), while the occlusal enamel was cut 2 mm above the CEJ using a slow-speed water-cooled diamond saw (Isomet b ). The pulpal tissue was carefully removed with small tweezers to avoid scratching the pulpal walls. The exposed dentin surface was ground just before bonding with a 600-grit SiC paper for 60 seconds under running water to create standardized smear layers. Each tooth was longitudinally sectioned into halves (experimental and control) in order to standardize the bonding substrates in each group. The 80 specimens were randomly divided into three main groups based on the electric current applied: (1) 0 A (n=40); (2) 20 A (n=20); (3) 40 A (n=20), and each main group was subsequently divided into two sub- groups according to the self-adhesive resin cements employed in this study (RelyX Unicem c and BisCem d ) (Table 1). Half of the resin discs (Filtek Z250-XT c ) were prepared using polyvinylsiloxane molds (12 mm diameter and 2 mm thick). The surface of the composite to be bonded was sand- blasted with aluminum oxide (50 μm), at 2 mm distance and 2 bar pressure for 5 seconds. The discs were subjected to ultrasonic bath for 3 minutes and this surface was silanized