Aim of study: Aim of this study to evaluate the antimicrobial properties of fluoride release dental resin composite (SureFill SDR, DENTSPLY Caulk, Milford, Delaware, USA) compared to conventional Glass ionomer (Ketac™ Molar Quick, 3M/ESPE, St. Paul, USA). Materials and methods: Ten specimens of fluoride release dental resin composite (SureFill SDR) and conventional Glass ionomer (Ketac™ Molar Quick) were prepared with 8 mm diameter and 2 mm thickness. Then specimens finished and polished. Then each specimen was placed in a tube containing 5 mL of deionized water. The tubes were incubated at the controlled temperature of 37°C for up to 30 days. The storage solution was collected and collected solution was mixed with TISAB III solution. Fluoride ion concentration in the solution was then measured using fluoride specific ion electrode. An adapted agar diffusion test, used for the assessment of antimicrobial activity, was applied in the microbiological studies. Results: there was fluoride release of all composite specimens (SureFill SDR) were below effective threshold (0.1 ppm-1 ppm) mean ± standard deviation (0.001 ppm ± 0.0005 ppm), while fluoride release of Ketac™ Molar Quick was (6.1 ppm ± 0.2 ppm). Antimicrobial activity: after 1-day storage there was no inhibition zone detected in both blood agar and agar-agar plates in composite specimens while there was inhibition zone in glass ionomer specimens, after 15 days’ bacterial growth was observed in both incubation media of composite specimens. Conclusion: SureFill One show little fluoride release (below effective threshold) and there is no antimicrobial activity especially cariogenic bacterial other than Ketac™ Molar Quick.