Figure 8. Modified SEM image of bonding to dentin with (two-step) self-etching adhesives. (A) The smear-layer covering the dentin surface and the smear-plugs occluding the dentinal tubules are impregnated by the self-etching primer (light blue). (B) Application of the acidic primer. The acidic resin (blue) has dissolved and impregnated the smear layer. The resin has also penetrated the dentinal tubules. (C) Dentinal substrate after application of the adhesive resin. Theoretically, the adhesive resin (purple) infiltrates to the same extent as the acidic primer exposed the collagen.