The aim of the present study is to compare the effect of canal shaping using TruNatomy and RaCe rotary systems in bi-rooted maxillary premolars in terms of:

• Post operative pain: incidence and intensity
• Real time torque generated during mechanical instrumentation using real time torque motoring endodontic motor
• Time needed for the instruments to reach to the full working length

Inclusion Criteria:

• Patients who are free from any physical or mental handicapping condition and no contributory systemic disease.

• Age between 30-60 years old.

• Males & Females.

• Patients' acceptance for participating in the trial through an informed consent

• Maxillary permanent premolar teeth:

  • Diagnosed clinically and radiographically with pulp necrosis
  • With or without periapical radiolucency
  • Negative response of pulp tissue to thermal and electric pulp tester
  • Possessing two independent roots each having a type I canal
  • Patent canals with no internal calcification or resorptive lesions
  • Fully formed roots
  • Root curvatures less than 30

Exclusion Criteria:

• Patient with contributory medical condition

• Badly destructed teeth

• Patients with pre-operative pain

• Patients having significant systemic disorders

• Patients with two or more adjacent teeth requiring root canal therapy

• Patients who had received antibiotics in the last month

• Teeth presenting with:

  • Positive response to thermal or electric pulp tester
  • History of trauma or previous endodontic treatment
  • Immature or open apices
  • Association with acute periapical abscess and swelling or fistulous tract
  • Fused roots at any level
  • Canals larger than size 15# K-file
  • Periodontonal/ endodontic lesions
  • Mobility higher than grade I
  • Radiographic evidence of external or internal root resorption vertical root fracture, perforation, calcification.
  • Severe root curvature (>30)