This randomized controlled trial aims to evaluate the effect of two different concentrations of sodium hypochlorite (2.5% and 5.25%) on post-operative pain following single-visit root canal treatment. A total of 116 participants requiring primary endodontic treatment will be randomly allocated into two groups according to irrigant concentration. Post-operative pain will be assessed using a 100-mm Visual Analog Scale at 6, 12, 24, and 48 hours after treatment. The study seeks to determine the concentration that provides optimal disinfection with minimal patient discomfort.

This study will be conducted in the Department of Operative Dentistry, Saidu College of Dentistry, Swat. Sodium hypochlorite is widely regarded as the gold standard irrigant in endodontics because of its tissue dissolution and antimicrobial properties. However, its concentration-dependent cytotoxicity may influence post-operative pain after treatment.

A randomized controlled trial design will be used with two parallel groups receiving either 2.5% or 5.25% sodium hypochlorite during standardized single-visit root canal treatment. A total of 116 participants aged 18-60 years requiring primary root canal therapy will be recruited using consecutive sampling.

All procedures including anesthesia, access preparation, working length determination, instrumentation, irrigation protocol, and obturation will be standardized. Post-operative pain will be recorded using a 100-mm Visual Analog Scale at 6, 12, 24, and 48 hours post-treatment.

Data analysis will be performed using IBM SPSS Statistics. Repeated measures analysis will compare pain scores between groups across different time intervals. Statistical significance will be considered at p < 0.05.

Inclusion Criteria:

• Adult patients aged 18-60 years Systemically healthy individuals Permanent teeth with closed apices requiring primary root canal treatment Teeth diagnosed with symptomatic/asymptomatic irreversible pulpitis or pulpal necrosis Patients able to understand the Visual Analog Scale Patients willing to provide informed consent and complete follow-up

Exclusion Criteria:

• Uncontrolled systemic diseases Pregnant or breastfeeding women Allergy to sodium hypochlorite or local anesthetics Previously endodontically treated teeth Teeth with root resorption, vertical root fracture, or open apex Severe periodontal disease or mobility Use of analgesics, antibiotics, or anti-inflammatory drugs within previous 7 days