Abstract:Fiber posts (FP) are commonly used for extensive coronal reconstructions, often being associated with composite resins (CR) in order to minimize the space between the post and the intraradicular dentin. This study evaluated the shear bond strength of three different CR to a FP surface, with and without FP pretreatment with adhesive. Sixty #3 FP (Exacto Translúcido) were divided into six experimental groups (n = 10), according to the surface treatment used: G1-Filtek ™ Z250; G2-Filtek ™ P90; G3-Filtek ™ bulk fill restorative; G4-Scotchbond ™ Universal adhesive + Filtek ™ Z250; G5-Silorane adhesive + Filtek ™ P90 and G6-Scotchbond ™ Universal adhesive + Filtek ™ Bulkfill restorative. Two 2.0 mm thick specimens were obtained from each fiber post unit and submitted to a push-out test in a universal testing machine with a 5 mm/min crosshead speed and 5 Kilo-newton load cell. Mean and standard deviation values for bond strength (MPa) were: G1: 5.54 ± 1.78; G2: 1.69 ± 1.02; G3: 5.31 ± 1.58; G4: 7.39 ± 2.05; G5: 6.07 ± 1.88e G6: 5.50 ± 3.03. The results were analyzed through two-way analysis of variance (ANOVA) and statistical significant differences were determined by Tukey test (p = 0.05). When no adhesive was used, the bond strength was statistically significantly higher for G1 and G3, which were not statistically significantly different between them. Adhesive application showed statistically significantly higher bond strength only for G5. Without the FP pretreatment with adhesive, the bond strength was statistically significantly higher for the methacrylate-based resins and the FP pretreatment with adhesive increased the bond strength only for the silorane-based resin and changed the prevalence of failure mode type to cohesive in all composite resin study groups. The use of silorane-based composite resins to customize posts require the use of adhesive as FP surface pretreatment. The use of adhesive as pretreatment of simulated customized FP, regardless of the CR used, appear to improve the mechanical behavior of the FP-CR unit.