Bond strength of a total-etch and two self-etch adhesives to dentin with and without intermediate flowable liner

Purpose: To evaluate the effect of flowable resin composite application on the microtensile bond strength of a total-etch and two self-etch adhesive systems to dentin. Methods: Occlusal surfaces of 30 human third molars were ground to obtain flat dentin surfaces. One of the following adhesive systems was applied to the dentin surface following manufacturers' instructions: Admira Bond, Futurabond DC and Clearfil SE Bond. For each adhesive, half of the specimens received a layer of flowable composite (Amaris Flow) applied into dentin and light-cured (experimental groups). The other teeth received no liner and served as control group. For all teeth, resin composite (Amaris) was applied in 2 mm thickness to form a crown segment 5-6 mm height and each increment was light-cured. The restored teeth were stored in water at 37 degrees C for 24 hours. Each tooth was serially sectioned in a longitudinal direction in order to obtain several bonded slabs (1.0 mm(2) in cross-section). Each slab was attached to the set-up by their lateral sides and placed in a universal testing machine. Tensile load was applied at cross-head speed of 0.5 mm/minute until failure. Data were analyzed by two-way ANOVA and Tukey's test at 5% significance level. Results: Placement of a low-viscosity resin after adhesive application increased the microtensile bond strength for all tested adhesive systems. However, such increase was not significant (P > 0.05). The percentage of cohesive failure was increased in specimens with flowable resin liner. (Am J Dent 2010;23:157-160).