The preparation of antibacterial polymeric dental restorative materials was carried out using various ammonium chloride compounds. To improve the mechanical properties of dental restorative composites, surface of silica filler was treated with γ-Methacryloxypropyltrimethoxysilane. Both diametral tensile and flexural strength of composites were measured. Antibacterial effect was also investigated. The optimum concentration of antibacterial agent was 3 wt% of 2,2''-Bis-[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]-propane/Triethyleneglycol-dimethacrylate resin matrix and antibacterial agents with higher chain length between functional groups reduced mechanical properties of restorative materials. It was also discovered that optimum chain length between ether (or amino) and ammonium group of antibacterial compound was 2∼3 carbons.