Hypertonic Saline as a Final Flush and Post-Operative Pain After Single Visit Root Canal Treatment in Mandibular Premolar.

This randomized controlled trial evaluates whether a final flush with 3% hypertonic saline, compared with 0.9% normal saline, reduces post-operative pain and periapical Substance P (SP) levels after single-visit root canal treatment in mandibular premolars with symptomatic irreversible pulpitis. Forty adult patients will be randomized 1:1. Pain will be measured with the Visual Analogue Scale (VAS) at 6, 12, 24, and 48 hours post-operatively. Periapical fluid SP levels will be measured by ELISA at two intra-operative time points (after working length determination, and after the final flush). The number of ibuprofen 400 mg tablets consumed within 24-48 hours will also be recorded.

Inclusion Criteria: * Age 18-60 years, any sex * Systemically healthy * Mandibular premolar with clinically/radiographically diagnosed symptomatic irreversible pulpitis (prolonged, exaggerated response to cold testing; no periapical radiolucency) * Able to use the VAS scale and complete follow-up Exclusion Criteria: * Medically compromised patients * Pregnant or lactating women * Allergy/hypersensitivity to local anesthetics or NSAIDs * Analgesics, anti-inflammatories, or antibiotics within 12 hours pre-treatment * Vertical root fracture, root resorption, or previous RCT * Radiographic periapical pathology * Non-restorable teeth * TMD, bruxism, or traumatic occlusion interfering with pain assessment