The physical and chemical properties of restorative materials and procedures that influence the extent of microleakage at the tooth/restoration interface are discussed. Adhesion to enamel is achieved and microleakage at the enamel/restoration interface has been controlled by acid etching enamel surfaces with orthophosphoric acid. The acid concentration and the duration of etching are reviewed. Adhesion to dentin and microleakage at the restoration/dentin (cementum) interface are more difficult. The development of dentin bonding agents and the tremendous advances made with these restorative systems are reviewed. Particular attention is directed towards the Gluma/Lumifor dentin bonding restorative system and the development of an experimental conditioning solution for both enamel and dentin.