Degree of postoperative pain was measured using visual analogue scale (VAS) after 6, 12, 24 and 48 hours after instrumentation then at 6 and 12 hours after obturation. The VAS consists of a 10-cm line anchored by two extremes "No pain" and "pain as bad as could be". The patients were asked to choose the mark that represents their level of pain. Pain level was assigned to one of four categorical scores: 1, None(0); 2,Mild(1-3); 3,Moderate(4-6); 4,Severe(7-10) 10.