1. The patient marks moderate to severe pain on the numerical rating scale (NRS) . a horizontal line of 11 marks and 10 intervals each takes numbers from 0 to 10 where 0 = no pain , 1-3 =mild pain , 4-6 = moderate pain , 7-10 = severe pain (recording the baseline degree of pain preoperatively before initiating the endodontic treatment ) all the steps done by the same operator.