This study evaluated microtensile bond strength (pTBS) when an additional adhesive layer was applied to the dentin surface. Thirty-five human third molars were flattened to expose the occlusal dentin surface. The teeth were randomly assigned to 7 experimental groups: G1-Single Bond (SB); G2-additional layer of SB; G3--a layer of Scotchbond Multi-purpose (SMP) adhesive applied over SB; G4-Clearfil SE Bond (CE); G5-additional layer of CE; G6-Adper Prompt (AP) and G7-additional layer of AP. For the G2, G3, G5 and G7 groups, the first adhesive layer was light-cured before application of the additional layer. After bonding procedures, 5-mm high composite crowns were incrementally built up. The samples were sectioned to obtain 0.9 x 0.9 beams, which were tested under tension at a crosshead speed of 0.5-mm/minute until failure. The failure mode and adhesive thickness were evaluated under SEM. The pTBS data were analyzed by 1-way ANOVA and post-hoc Ducan's Test (a=0.05). Mean adhesive thickness was analyzed by 1-way ANOVA and post-hoc Tukey's test (a=0.05). The results indicated that G3 presented the highest microTBS and the thickest adhesive layer. G6 and G7 presented the lowest microTBS values. When solvent-free adhesives systems were used, microTBS values were not affected by the thicker layer.31562-8