الفهرس 
Introduction .Only 14 pages are availabe for public view
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Abstract
This study aimed to evaluate a quick-setting calcium-silicate based dental cement (BiodentineTM, Septodont, Saint Maur des Fossés, France) launched in 2011 as a bioactive and biocompatible dentin substitute. The solubility of Biodentine in water and its bond strength to the overlying resin composite restoration were both evaluated in this study.
Obtaining a durable bond between resin composite and the underlying dentin is challenging owing to the polymerization shrinkage of resin composite and the incomplete infiltration of resin into the demineralized dentinthat may lead to bond failure.
The introduction of the sandwich technique to overcome the drawbacks of resin composite restorations allowed the use of Glass Ionomer Cement (GIC) as dentin substitute, which is placedbeneath resin composite thatreplaces the enamel, thus providing the advantages of both composite restorations and GICs.
However, the dissolution of GIC has been reported by some clinicians to occur ‘often’ at the proximal area in the open sandwich, where it is difficult to control moisture and gain access for finishing. Thus an alternative material to GIC with lower solubility in the oral environment may be required in an open-sandwich technique.
In this study, the soluibility of Biodentine was assessed after both 24 hours and 6 months of immersion in deionized water using both the residue method and the % mass loss of the disc.
The micro-shear bond strength between Biodentine and the overlying flowable composite was evaluated by bonding resin composite to Biodentine at different time intervals from mixing of Biodentine: 15 minutes, 24 hours and 30 days. All the groups were furthersubdivided into two subgroups after specimen preparationintotwo different storage periods before testing; the bond strength of the first subgroup was evaluatedafter 24 hours and the other subgroup was aged in distilled water for 6 monthsbefore evaluating its bond strength.Fractographic analysis was doneto the surface of Biodentine specimensusing stereomicroscope to assess the mode of failure of the specimens.
During specimen preparation, we recognized the precipitation of a layer on the surface of Biodentine that increased in thickness by time. Thus, more groups were prepared by grinding the surface of Biodentine for 20 seconds before bonding resin composite on top of it for all the previously prepared time intervals. This grinding could not be applied to the 15 minute groups because Biodentine was washed away during the rinsing process. Surface topography was analyzed using Scanning Electron Microscope (SEM). Chemical groups present in the surface precipitate were investigated using Fourier Transform Infrared Spectroscopy (FT-IR).
Results of this study revealed higher solubility of Biodentine after 6 months compared to 24 hours as shown by the residue method. However, the discs of Biodentine have gained more weight after 6 months compared to 24 hours. For the micro-shear bond strength results;regarding the effect of time on bond strength; better results were obtained when bonding was done after 15 minutes compared to 30 days, moreover, water storage for 6 months has compromised the bond strength.
The trial done to grind the surface of Biodentine before applying the resin composite had no effect on the bond strength. Scanning Electron Microscope has shown rough surface of Biodentine at 15 minutes, and crystalline precipitates on the surface of Biodentine after 24 hours and 30 days. FT-IR analysis has shown more hydration after 30 days compared to 24 hours.