Inclusion Criteria:  Teeth with necrotic pulps and asymptomatic apical periodontitis  Exclusion Criteria:  patients who had received antibiotics during the previous 3 months or had any general disease, teeth that could not be properly isolated with rubber dam, non-restored teeth, periodontal pockets depths greater than 4 mm, previous endodontic treatment, open apex, crown/root fracture root resorption or calcifications.