BACKGROUND The aim of this study was to evaluate the antimicrobial effectiveness of dental cement materials for the prevention of bacterial growth, which can cause failure of fixed cementation. MATERIAL AND METHODS We developed an agar diffusion disk test in-house to evaluate the antibacterial properties of 3 commercially available dental cement materials (Ketac, Harvard FLB, and Panavia SA Universal Dual Resin cements) compared with a negative control. The materials were tested for the inhibition against Streptococcus mutans (ATCC 10449), Streptoccocus salivarius (ATCC 25975), Enterococcus faecalis (ATCC 29212), and Lactobacilus acidophilus (ATCC 4356). The antimicrobial effectiveness of materials was expressed as the diameters of the inhibition zones around the disk. RESULTS Overall, 240 specimens were tested. All cement materials showed antimicrobial effectiveness. Different microbial strains reacted differently to the different dental cements (all P.