The antimicrobial effectiveness of bioaggregate (BA) and mineral trioxide aggregate (MTA) against Enterococcus faecalis was evaluated in vitro. Fresh BA and MTA powders, powder from crushed set materials, and pieces of uncrushed set cements were suspended in autoclaved water at concentrations of 10-100 mg/mL for direct exposure testing. The antimicrobial effect of the cements mixed with equal amounts of human dentin powder was also tested. BA and MTA powder were equally effective in bacterial elimination and caused a significant decrease in bacterial viability within 6 minutes. Powder from crushed set cements was either equally or more effective than fresh powders in killing the bacteria. The addition of equal amounts of dentin powder to the suspension of either BA or MTA powder (both fresh and set) resulted in faster elimination of the bacteria (P < 0.05).