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cosmetic dentistry_ beauty & science

08 I I CE article _ bioactive materials astressabsorberattheinterfaceoftherestoration and the tooth.12 Resin-modified glass ionomers (RMGIC), which are a hybrid of traditional glass ionomer cements with a small addition of light-curing resin, exhibit propertiesintermediateofthetwomaterials.13 This material has been shown to have properties simi- lar to GIC, but with better esthetics and immediate light cure. RMGICs have been shown to undergo slight internal fracturing from polymerization shrinkage, yet have an inherent ability to renew broken bonds and reshape to enforce new forms.12 ApplicationofRMGICtoallcutdentininClassII composite restorations has been shown to “sig- nificantly reduce micro-leakage along (the) axial wall” of the restoration,14 and helps prevent bac- terial invasion of the restored tooth. RMGIC bio- materials are multifunctional molecules that can adhere to both tooth structure and composite resin,thusprovidinganimprovedsealingabilityby chemical or micromechanical adhesion to enamel, dentin, cementum and composite resin. They, like GICs, can be bulk filled to reduce the amount of composite necessary to restore the cavity preparation and act as dentin substitutes in the restoration.15 The use of GIC and RMGIC in the restoration of posterior Class V restorations and conservative Class I restorations provides many benefits. They are easy to place and reasonably forgiving, even in a slightly moist environment. They should be placed in a moist but not wet environment, so familiaritywithtechniqueisimperativeasitiswith alldentalrestorations.IwilloftenuseRivaSC(SDI) or Fuji 9 GP Extra (GC America) in posterior Class I and V restorations (Figs. 1–7). Polishing and shaping of the materials must be done with water spray and fine/ultra fine compos- itefinishingbursandpolisherssoasnottodestroy the surface of the material (Fig. 8). The use of RMGIC products, such as Riva LC or Fuji II LC, is great in bicuspid and anterior Class V restorations, especiallyinhighcariespronepatients(Figs.9–12). Class II restorations, however, have always pre- sented a challenge to the clinician. If the operator wantedtouseGICorRMGIC,therewasnoeasyway to do this that appeared to provide satisfactory results. It is with this in mind that the “sandwich technique” was developed. It was thought that using the properties of GIC to bond to the tooth and then applying resin- bonding agents and composite to the set GIC couldhelpreducesensitivityandbondfailurestyp- ically seen in many resin-bonded composite (RBC) techniques. Typically, the GIC is placed in the preparation, allowed to set, cut back to ideal form and then bonded to with an RBC technique. However, the inability of RBCs to adhere to the set GIC often createsmanyfailures.Thematerialsbythemselves are incompatible over the long term. The modified sandwich technique evolved as a means to overcome this problem. Placing RMGIC over set GIC—and then adding a RBC to that— provided a better solution, but was as laborious and time consuming to do, as is the sandwich technique. _The ‘Co-Cure Technique’ In 2006, an article was published16 that, in my opin- ion, has revolutionized the way I approach direct poste- rior restorations and direct restorations as a whole. The article presented a radical approach to direct posterior cosmeticdentistry 1_2013 Fig. 10 Fig. 11 Fig. 9Fig. 8