Evaluation Of Microleakage In Class II Cavity Preparation Restored Using Zirconomer As Liner And Composite Resin In Closed-Sandwich Technique

Introduction : Microleakage in class II restoration mostly occur due to masticatory stresses and thermal changes which leads to secondary or recurrent caries. To overcome this problem of marginal leakage, Glass Ionomer cement base was used to substantially replace the composite resin restorative material in the proximal box.This technique is known as “composite-laminated GIC” or “sandwich” restoration. In the traditional “closed sandwich” technique there is placement of the zirconomer at the base of the proximal box so as it falls just short of the external cavo surface. This procedure offers no protection from proximal caries until failure of the dentine bonding agent.Materials and method : Twenty-six sound healthy teeth with absence of caries, restoration, cracks and white spots were selected.The proximal box was 4 mm wide bucco-lingually; whereas, the pulpal and axial walls measured to be 2 mm deep. After placement of the Zirconomer at the base of the proximal box such that it falls just short of the external cavo surface, etching and bonding of Zirconomer was done. Composite resin was placed in the proximal box and occlusal surface, leaving the zirconomer encased within the preparation. Samples were then processed for thermocycling. With the help of modelling wax, the apexes of the root were sealed to prevent the ingress of dye. The samples were then coated with nail varnish, applying two coats around all surfaces of teeth leaving 2 mm of the marginal area around the restorations. Immersion of sample was then done in methylene blue dye. Samples were then washed under running water for one minute and then air dried. In next step restorations were sectioned longitudinally through the centre of the tooth. They were sectioned by using diamond disc along with water as coolant. Sections were examined at 32x magnification under a stereomicroscope. SEM observations at the gingival margins of the specimens restored with closed sandwich technique depicted less satisfactory marginal adaptation. Conclusion : It can be concluded that none of the technique tested are free of microleakage. Zirconomer placed in the gingival floor of class II composite restoration may be a practical method to reduce microleakage.