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News Bulletin : ADA News Bulletin May 2011
39 MAY 2011 box and occlusal surface, leaving the glass ionomer cement encased with the preparation. This procedure offers no protection from proximal caries until failure of the dentine bonding agent. The application of a resin modified glass ionomer cement bonding agent (Fuji Bond LC, Fuji II LC, GC Corp, Japan. Vitremer 3M ESPE, USA) that extends to the outer cavo margin enables the marginal tooth structure to continue to receive the dual benefits of a glass ionomer cement, namely, fluoride infusion as well as the buffering capacity (although somewhat reduced). This may be achieved in either of two ways: Composite resin co cure technique Bond a thin layer of a resin modified glass ionomer cement (RMGIC) bonding agent directly onto etched enamel and dentine. Next place a second layer of resin modified glass ionomer cement bonding agent followed immediately by the application of a composite resin prior to light curing. The first layer of resin modified GIC bond cures all the HEMA and seals the cavity while the second layer acts as a polymerization stress release during photo initiation of the composite resin. For cavities over 2 mm deep a further layer of resin modified glass ionomer cement bonding agent can be used as a stress breaker between layers of composite resin (Fig 4 -- RMGIC bond has been dyed blue for clarification purposes*). Glass ionomer cement co cure technique Following cavity preparation and etching of dentine and enamel surfaces, an increment of auto cure glass ionomer cement is placed into the proximal box and over the floor of the cavity extending up to the dento enamel junction around the perimeter of the preparation or just short of the cavo margin at the base of the proximal box. Either prior to or at the immediate set of the auto cure glass ionomer cement, a layer of resin modified glass ionomer cement bonding agent is brushed over the auto cure glass ionomer cement and up to the outer perimeter of the preparation. An increment of composite resin is next placed over the auto cure glass ionomer cement to fill the cavity followed immediately by photo curing the preparation. Upon photo initiation the composite resin cures and undergoes polymerization shrinkage before the resin modified glass ionomer bond has cured resulting in a stress free bond to tooth structure Fig 3. Glass ionomer cement succumbs to acid break down at the surface resulting in food packing and creating the impression of recurrent caries. Fig 4. Composite resin co cure technique. Fig 5. Glass ionomer cement co cure technique. at the cavity perimeter. Resin modified glass ionomer cement chemically bonds composite resin to glass ionomer cement. The exothermic setting reaction of the composite resin heats the auto cure glass ionomer cement initiating a cascade setting reaction of the auto cure glass ionomer cement to occur between 20 to 40 seconds depending on the ambient temperature (Fig 5 -- RMGIC bond has been dyed blue for clarification purposes†). CONCLUSION The successful placement of a proximal restoration requires a predictable outcome that offers protection from further caries at the cavo margins. Apart from these benefits, the 'co cure closed sandwich technique' creates stress free cavo margins and is more clinically efficient to place than incremental placement of composite resin using a dentine bonding agent or the traditional set and etch techniques prescribed for sandwich restorations. REFERENCES References supplied with this article are available from the author email@example.com DISCLAIMER The statements made in the above article are published on the authority of the author and have not been peer-reviewed. They do not necessarily reflect the views of the ADA and publishing them is not to be regarded as an endorsement of them by the ADA. The author has a financial interest with some of the companies mentioned in this article. *A video of composite resin co cure technique may be viewed at www. dentalk.com.au † A video of glass ionomer cement co cure technique may be viewed at www.dentalk.com.au aesthetic update
ADA News Bulletin April 2011
ADA News Bulletin June 2011