The aim of this study is to clinically compare the intensity of post-operative pain and the amount of bacterial reduction after using 20mg/ml propolis nanoparticles extract solution during chemo-mechanical preparation, versus 2.5% NaOCl, in asymptomatic necrotic mandibular premolars treated in a single visit.

Inclusion Criteria:

1. Systematically healthy patient (ASA I,II).
2. Age between 20 and 55 years
3. Male or female.
4. Asymptomatic mandibular premolar teeth diagnosed with pulp necrosis with or without apical periodontitis.
5. Radiographic examination using Digora intraoral periapical sensor plate and software (Digora; Soredex, Helsinki, Finland) showing mandibular premolars with (smaller than 3 mm (0-2 mm)) periapical radiolucency.

Exclusion Criteria:

1. Medically compromised patients having significant systemic disorders. (ASA III or IV).

2. History of intolerance to NSAIDS.

3. Teeth with:

   • Immature roots
   • Vital pulp tissues.
   • Association with swelling.
   • Acute peri-apical abscess or acute exacerbation of a chronic abscess.
   • Mobility Grade II or III.
   • Previously accessed or endodontically treated
   • Deep periodontal pockets more than 4 mm
   • Vertical root fractures, coronal perforation, calcification, and external or internal root resorptions.

4. Patients who could not interpret the NRS.

5. Patients with diabetes, immune-compromising, and immunosuppression disease and pregnant women were, also, excluded.