Patients will be clinically and radiographically examined and their eligibility will be assessed. Eligible patients will be treated in one visit.~Patients will be randomly assigned to one of 4 groups: experimental groups of root canal instrumentation with EdgeFile X7 to size #35/0.06 or #45/0.04 or #45/0.06 or the comparator group to size #35/0.04. Intra-canal bacterial count will be measured using a culture technique. Bacterial samples will be taken before and after root canal instrumentation. After endodontic treatment, patients will be given postoperative instructions and informed, in case of pain, to receive ibuprofen 400 mg as rescue medication.~Postendodontic pain intensity and incidence at the different pain categories (No, mild, moderate, severe) will be assessed at 6, 12, 24, 48 and 72 hours postoperatively using Numerical Rating Scale (NRS).
The aim of this prospective randomized clinical trial is to evaluate the effect of different apical size and taper preparation (35. 04; 35. 06; 45. 04 and 45. 06) on postoperative pain at 6, 12, 24, 48 and 72 hours, and intra-canal bacterial count in patients having mandibular premolars with necrotic pulps.