The science of dental materials covers a broad range of terminology, composition, microstructure and properties used to describe or predict the performance of preventive and restorative materials. Additives, fillers, and reinforcements are used to change and improve the physical and mechanical properties of plastics. Most of the materials used in dentistry contain fillers as a part of their composition. By the appropriate selection of the fillers, not only the economics but also the other properties such as processing and mechanical behaviour can be improved.