In the early 1990s reformulated ionomer-based materials were introduced. The modified materials are based on modifications that replace part of the original glass ionomer formulation with alternative filler particles sad/or matrix setting reactions to make them more composite-like (see Fig. 4-83, H to J) These materials are cate gorized as hybrid or resin-modified glass ionomers, They are usually light – cured, less technique sensitive, and may be finished at the time of placement. Although more compositelike in composition and structure, resin-modified glass inonmers still undergo acid-base reactions during setting and retain much of the chemical behavior of traditional glass-ionomer materials. Because resin – modified glass ionomers are significantly stronger than traditional glass ionomers, thay are recommended for Class V restorations and can be used for Class I and Class II restorations in primary teeth.