The evolution of resin-containing materials has resulted in a major advance in restorative dentistry as mercury-containing silver amalgam are used less in the dental practice. However, there is still a debate on the in vitro and in vivo biological properties of dental resins now considered as potential amalgam substitutes. Differing answers between clinical data as opposed to what is known about the tolerability or toxicity of resin-containing materials, creates some benefit/risk interrogations for dental practitioners. In order to reduce the gap between basic science and the clinic, a dialogue has been established between researchers in biomaterials and in biology, and also between researchers and clinicians. A group of well-recognized experts was asked by the Regional European Organization of the Federation Dentaire Internationale to report on the intrinsic properties, the biocompatibility or cytotoxic effects of dental composites. Consequently, the physico-chemical properties of resin based composites and dental adhesives are reviewed in this text. The interaction of resin-containing materials with soft dental and calcified tissues is then studied and adverse effects are reported in a series of in vitro and in vivo studies. In order to reconcile differing evaluations, laboratory data are compared with human clinical data. In addition, a final chapter aims to provide some insights on emerging trends in dental material research. A series of investigations on a new restorative cement are given as examples of future developments. The gap between the bench and the chair side is still open, but answers are now better identified in this book.