Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)This study evaluated the bond strength and ultramorphology of the resin-dentin interfaces produced by current dental adhesive systems. Nine dentin bonding agents were investigated. Restored teeth were vertically, serially sectioned to obtain bonded slices for interfacial TEM analysis or to produce bonded beams for the microtensile bond strength test. The one-step self-etching adhesives (Futurabond (R) NR and Hybrid Bond (R)) showed lower bond strength values than the three-step etch-&-rinse adhesive system All-Bond 3. Most bonding agents presented statistically similar mean bond strength values, which ranged from 41.3 +/- 17.9 to 35.0 +/- 5.3 MPa. The thickness of the hybrid layer varied according to the type of adhesive system used. While the etch and rinse adhesives with alcohol as organic solvent showed bond strength means higher than 40 MPa, the self-etching systems showed bond strength lower than 40 MPa. Resin-dentin inter-difusion zone and resin tags were noted in all bonded interfaces.871211481166National Council for Research and Development [474670/2006-6, 303587/2007-5]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)National Council for Research and Development [474670/2006-6, 303587/2007-5]FAPESP [05/60697-9, 07/06083-4]