The addition of resin to glass ionomers improves them significantly, allowing them to be more easily mixed and placed. Resin-modified glass ionomers allow equal or higher fluoride release and there is evidence of higher retention, higher strength and lower solubility. Resin-based glass ionomers have two setting reactions: an acid-base setting and a free-radical polymerisation. The free-radical polymerisation is the predominant mode of setting, as it occurs more rapidly than the acid-base mode. Only the material properly activated by light will be optimally cured. The presence of resin protects the cement from water contamination. Due to the shortened working time, it is recommended that placement and shaping of the material occurs as soon as possible after mixing.