Significant advances have been made in the development of systems that adhere to dentin, and restorative dentistry is fast approaching the development of a group of materials that will provide a strong and durable bond to dentin. Newer dentin-bonding systems, requiring alteration or complete removal of the smear layer, in general produce stronger bonds, and appear to provide a more effective marginal seal, than smear layer-dependent bonding systems. Some of these newer bonding agents have developed bond strengths to dentin comparable to those achieved with acid-etched enamel surfaces. However, for situations in which the retentive form of the cavity preparation is particularly critical to the success of the restoration, traditional retentive features should be used in the cavity design.