الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
This study was conducted to investigate in Vivo and in Vitro the effect of SDR resin-based composite as a liner under Class II nano hybrid resin composite restorations. For clinical study, forty-five patients wih Class II carious lesions were selected. A total of 90 Class II cavities were prepared in premolar/molar teeth. The cavities were equally divided into three groups. For laboratoy investigations; i. polymerization shrinkage test: composites (SurFil SDR & Filtek z350 XT flow) were applied to a cylindrical Teflon mold (7 mm ×2 mm), polymerized and removed from the mold. Optical coherence tomography was used for linear shrinkage evaluations. ii. marginal and internal adaptation test, 30 MOD cavitties were prepared in extracted human molars. The cavities (n=10) were restored and grouped like clinical test. Before and after thermocycling (between 5 and 55 0c), marginal gaps were analysed using OCT Based on the results and within the limitations of this study, There were no significant differences (p >0.05) between the tested groups for clinical investigations, while there were a high significane differencec (p<0.0001) for laboratory investigations.Conclusions: SDR as 4 mm bulk fill dentin replacement showed good performance as a liner under nano hybrid composite resin restorations.