This article discusses the composition of major components of dental composite resins. The components include organic resin matrix, filler, coupling agents, and initiator-accelerator systems. The article provides a description of three steps in adhesive systems, namely, etching, priming, and the placement of a resin adhesive layer. It describes the properties of composite resins that are related to the amount and type of filler and resin-matrix compositions. The article also provides a discussion on the compositions, properties, and clinical applications of polyacid-modified composite resins and resin-modified glass-ionomer cements. It discusses the biodegradation and biocompatibility of resin-based restorative materials.