This study aimed to evaluate and compare impact of integrating passive ultrasonic activation and laser activation with nano-chitosan and aloe vera in terms of postoperative pain and flare-up incidence in a randomized clinical trial.

Inclusion Criteria:

• Age 18-60 (adults only)
• multiple-rooted with multiple root canal.
• Permanent teeth with mature apex and complete root formation.
• Without root caries.
• Tooth must be restorable.
• Without anatomical abnormalities such as fusion.
• Healthy patient category I according to ASA.
• Vital tooth, with acute irreversible pulpitis and without peri-apical periodontitis.
• No periapical radiolucency.
• Consent Patients for who consent to participate and attend follow-up appointments.

Exclusion Criteria:

• single root canals or double root.
• Root canal calcifications.
• Root resorption or fracture.
• Previously root canal treated teeth.
• immunocompromised patients.
• Pregnant females
• Patients with systemic diseases as diabetic or hypertension patients.
• Patients with facial swelling.
• patients who use analgesics or antibiotics within 48-72 hours.
• Allergy to any materials used (e.g., irrigants or anesthetics).
• psychiatric illness
• Teeth that are not indicated for endodontic treatment: bad oral hygiene, mobile teeth, or recessed teeth.
• Previously endodontically treated teeth.
• Teeth with sinus tract.