Of the many important scientific advances in restorative dentistry
in the past century, perhaps none is as important as the discovery
by Buonocore in 1955 of acid etching enamel. It is noteworthy that at the present time the resin bond to acid-etched enamel is the most important bond in adhesive dentistry. Smear layer is defined as any debris, calcific in nature, produced by reduction or instrumentation of enamel, dentin or cementum. Hybrid layer is formed by the interdiffusion of the low viscosity monomers into the exposed collagen network and the intertubular dentin to form a micromechanical bond with dentin. Dentin bonding has grown through many generations, and the process has been one of evolution and simplification.