Enamel adhesion by means of acid etching has become an accepted technique in restorative dentistry. Adhesion to dentin, however, is still under investigation. At this time, two distinct adhesive techniques are prominent in the attempt to establish a strong bond to dentin: total-etch and self-etching primers. Total-etch bonding systems have been shown to be effective both in vitro and in clinical evaluations. The new total-etch one-bottle bonding systems, although exhibiting the same success on laboratory tests, still have to prove their clinical effectiveness. Self-etching primer systems are undergoing rapid evolution; their results are not yet sufficiently predictable overall, but some systems have achieved positive results in both enamel and dentin bonding. Further studies are necessary to confirm the long-term efficiency of these self-etching primers.