A three-dimensional cavity design was used to test the bond strength between restorative materials and tooth structure. Results indicated that bonding agents that rely on mechanical retention to the dentinal smear layer produced relatively low bond strengths. Bonding agents that require smear layer modification yielded mixed results, possibly because of differences in chemical formulation. The three-dimensional cavity design employed in t his study is a replicable one, allowing the creation of standardized, clinically relevant preparations.