In the early 1970s dental composites came to be extremely important. The interesting possibilities that these materials offered was the reason to conduct a doctoral degree research project. During the period when the project was carried out, composites were already used in restorative dentistry extensively. At that time, mainly two-paste en UV-setting composites and a few visible light curing composites were available. However, the mechanical properties, the polymerization mode, the polymerization shrinkage and the composite wear were aspects of particular attention. During the past 25 years, research and material development have contributed to a significant improvement of these aspects. As a result of sophisticated filler technologies, occlusal wear of composites has achieved the level of good resistance, while the degree of shrinkage during hardening has been significantly reduced. However, shrinkage stress is still a matter of concern and remains an important subject of research, particularly with focus on the resin matrix. Low shrinking monomers and expanding monomers are being developed. If these materials can be introduced in dentisty, the shrinkage stress may be further reduced.