Methods: Sixty extracted human teeth were infected with E.faecalis for 3 weeks. The canals were prepared by a standard step-back technique and divided in two groups. In the first group (G1) calcium hydroxide was used as intra canal medication for 7 days and obturated with guta percha and sealer. The specimens of group two (G2) were obturated with guta percha and sealer immediately. All teeth incubated for 60 days .Each specimen were transversally cut in middle of the root. Dentine chips for detection E. faecalis were removed from two different depth of the apical intra walls with two sterile burs. Samples were immediately collected in separate test tubes containing BHI broth medium, and cultured to agar plates and colony forming units were counted.
Results: E.f recovered from 87.9% of G1( super ficial dentine), 78.3% of G1 (deep layer dentine), 39.4% of G2 (super ficial dentine) and 24.2% of G2 deep layer dentine.
Conclusions: According the result of this study using of calcium hydroxide as intra canal medication dose not cause elimination of microorganisms from the root canal.
Keywords: Endodontics and Microbiology