<qa>  What is a possible solution for preventing recurrent caries?Resin composites withholding antibacterial properties may be useful in preventing recurrent caries. Covalently attached antibacterial polymers are a possible solution.This in vivo study would evaluated the antibacterial effect of alkylated polyethylenimine nanoparticles incorporated into flowable and hybrid composite resin disks embedded in a palatal removable appliance.The disks would be in close contact with the palate in order to check for contact mucosities. disks on the side facing the Tongue would be evaluated for their antibacterial potency with confocal laser scanning microscopy. 