 Overall, 90 patients who had asymptomatic and non-vital teeth associated with periapical lesions, were included to the study. All diagnosis and treatment procedures were performed by a single operator to eliminate or minimize individual variability in the treatment between clinicians. The patients were randomly stratified into 3 groups of 30 by coin toss. Allocation was done by a person other than the operator performing the root canal procedure. The patients were assigned into three equal groups according to instrumentation techniques used n30; 