preventing carious lesions in teeth. It has good thermal properties as the expansion under stimulus is similar to dentine. The material does not contract on setting meaning it is not subject to shrinkage and microleakage. GIC is also less susceptible to staining and colour change than composite. Disadvantages of using Glass ionomer cement: GIC have poor wear resistance, they are usually weak after setting and are not stable in water however this improves when time goes on and progression reactions take place. Due to their low strength GICs are not appropriate to be placed in cavities in areas which bear an increase amount of occlusal load or wear. The material is susceptible to moisture when it is first placed. GIC varies in translucency therefore it can have poor aesthetics , especially noticeable if placed on anterior teeth. Resin Modified Glass Ionomer Resin modified glass ionomer was developed to combine the properties of glass ionomer cement with composite technology. It comes in a powder-liquid form. The powder contains fluro-alumino-silicate glass, barium glass (provides radiopacity), potassium persulphate (a redox catalyst to provide resin cure in the dark) and other components such as pigments. The liquid consists of HEMA (water miscible resin), polyacrylic acid (with pendant methacrylate groups) and tartaric acid. This can undergo both acid base and polymerisation reactions. It also has photoinitiators present which enable light curing. The ionomer has a number of uses in dentistry. It can be applied as fissure sealant, placed in endodontic access cavity as a temporary filling and a luting agent. It can also be used to restore lesions in both primary and permanent dentition. They are easier to use and are a very popular group of materials. Advantages of using RMGIC: Provides a good bond to enamel and dentine. It has better physical properties than GIC. A Lower solubility in moisture. It also releases fluoride over time. Provided better translucency and aesthetics as compared to GIC. Better handling properties making it easier to use. Disadvantages of using RMGIC: Polymerisation Contraction can cause microleakage around restoration margins It has an exothermic setting reaction which can cause potential damage to tooth tissue. The material swells due to uptake of water as HEMA is extremely hydrophilic. Monomer leaching : HEMA is toxic to the pulp therefore it must be polymerised completely. The strength of the material reduces if its not light-cured. GIC and RMGIC are used in dentistry,