The resin-modified glass-ionomers contain the essential components of both a conventional glass-ionomer and a visible light-cured resin. They have several advantages like longer working time, shorter setting time, bonding to tooth structure, fluoride-release, better aesthetics than conventional glass-ionomers and ease in use. As disadvantages can be mentioned the polymerisation shrinkage, trapping of air-bubbles, difficulties in colour choice and contouring. A physical and mechanical characterisation was necessary to define the possibilities and limits of these materials. It can be stated that the strength and aesthetic appearance of resin-modified glass-ionomers are less than that of composites, but better than that of conventional glass-ionomers. Clinically, this is expressed in a rough and dull surface compared to a composite restoration. They are not indicated in stress bearing areas. Consequently, they are mainly indicated in cervical class V-restorations in the postcanine region, and probably restorations in pedodontics, geriatric dentistry and for patients with a high caries activity.