Postoperative pain after endodontic treatment can affect a patient's quality of life. It is reported that debris extrusion after the instrumentation technique can influence postoperative pain. As a result, the aim of this clinical trial is to compare the recent rotary systems (TruNatomy, ProTaper Ultimate, Hyflex EDM and XP- rise rotary files systems) in terms of apical extrusion defined by post-operative pain and their role in reducing the bacterial count inside the canal

One hundred and twenty lower premolar teeth will be included in the study(n=120). Teeth will be randomly assigned to one of the 4 groups(n=30). Preoprative pain will be recorded before root canal treatment. Postoperative pain will be recorded using visual analogue scale (VAS) at 6 hours,12 hours, 1day, 2 days, 3 days, 4 dayse and five days after the root canal treatment. Bacterial count before and after instrumentation will be determined using culturing methods to determine the bacterial count reduction.

Inclusion Criteria:

• Medically fit
• Age ranges from 18-65 year
• Restorable teeth
• Necrotic teeth and symptoms free
• Lower premolars teeth (single canal posterior teeth)
• Necrotic pulps

Exclusion Criteria:

• Medically compromised
• Non-restorable teeth
• Open apex canal
• The past 12-hour history of analgesic intake before treatment.
• Patients with a history of antibiotics intake in the last 3 months before treatment.
• Pregnant females.
• Symptomatic patient.
• Pulpal diagnosis is not necrotic pulp.
• Retreatment cases