Push-out bond strength of FRC posts using conventional and wet-ethanol bonding systems: an ex-vivo study Hani F Ounsi, Ziad Salameh, Moustafa N.Aboushelib, Simone Grandini Abstract Purpose: The aim of this study was to compare the bond strength obtained on root canal walls when using two different adhesive systems to bond a fiber reinforced composite (FRC) post inside a root canal and to evaluate the type of failure at the resin-dentine interface. Methodology: Thirty-eight central incisors were root canal treated, divided in 2 groups, and restored using FRC posts luted using resin cement (Multilink). Excite DSC was used as bonding agent in group 1 and an experimental ethanol-wet bonding system was used in group 2. The specimens were cut into 1mm-thick sections and a push-out test was carried out after 24h. Fracture type was assessed using optical and scanning electron microscopy. Results: Mean and standard deviation for the excite DSC and ethanol-wet groups were respectively 7.6±5.5 and 7.4±5.6 MPa. The Mann-Whitney rank sum test showed no statistical difference between the 2 groups (P=0.708). With regards to failure type, adhesive failure prevailed in the 2 groups. SEM evaluation revealed that adhesive failures occurred mainly at the resin- dentin interface. Conclusions: The 2 bonding systems exhibited similar short-term behavior. A baseline is established to test potential improvement of long-term behavior when using ethanol-wet bonding systems. Running title: Push-out bond strength of FRC posts Key Words: adhesion, fiber-post, ethanol-wet bonding, interface, dentin, photodarkening Scientific Ounsi HF DCD, DESE, MSc, MRACDS(Endo), FICD. Research Department, School of Dentistry, Lebanese University, Beirut, Lebanon; PhD student, Department of Dental Materials, University of Siena, Italy. Salameh Z DDS, MSc, FICD. Assistant Professor, Research Department, School of Dentistry, Lebanese University,Beirut, Lebanon; Department of Dental Materials, University of Siena, Italy. Aboushelib MN DDS, MSc, PhD. Dental Biomaterials Department, Faculty of Dentistry, Alexandria University, Egypt. Grandini S DDS, PhD. Chair, Department of Endodontics and Restorative Dentistry, University of Siena, Italy. Corresponding author Prof. Simone Grandini Dipartimento di Scienze Odontostomatologiche, Università degli Studi di Siena, Policlinico Le Scotte, Viale Bracci, 53100 Siena, Italy Tel: 0039.0577.233131; Fax: 0039.0577.233117; e-mail: simogr@unisi.it Introduction In the actual wet-bonding concept, acid-etching of the dentin is required to generate a superficial collagen layer. This layer should remain moist and will receive a primer in order to allow the infiltration of hydrophobic monomers thus creating the hybrid layer 1 . Simplification of bonding procedures reduced 3-step techniques to 2 steps, and later to 1-step with the introduction of self- etching primer adhesives. This simplification was possible by increasing the amount of acidic monomers dissolved in primers. 2 However, some potential problems are associated with the simplification of bonding procedures 3,4 as these simplified adhesives behave as permeable membranes that allow the fluids to cross the adhesive layer after polymerization. 5 The water that migrates to the composite-adhesive interface is trapped as water blisters, which might act as stress concentration sites, which might result in deterioration of the resin-dentin bond. 6 Furthermore, long-term survival of bonded restorations is compromised due to the hydrophilic properties that allow for hybrid layer disintegration at the dentin resin interface. 7,8 This disruption of the hybrid layer was reportedly due to water sorption and also to the action of matrix metalloproteinases that were liberated from the dentinal tissues after the etching process. 9-11 As such processes are mainly water-based, recently, a 22 INTERNATIONAL DENTISTRY SA VOL. 11, NO. 3