Comparative Evaluation of Pediatric Rotary Files and Hand Files in Primary Molars

The goal of this clinical trial is to evaluate and compare the efficacy of Kedo-Nano Plus rotary files, Kedo-S Square rotary files, and manual K-files for biomechanical preparation during pulpectomy of primary mandibular molars in children aged 5-8 years. The main questions it aims to answer are: * Does the use of Kedo-Nano Plus and Kedo-S Square rotary file systems result in better obturation quality compared with manual K-files during pulpectomy of primary mandibular molars? * Does the use of Kedo-Nano Plus and Kedo-S Square rotary file systems reduce postoperative pain compared with manual K-files following pulpectomy? Researchers will compare Kedo-Nano Plus rotary files, Kedo-S Square rotary files, and manual K-files to determine their effect on obturation quality and postoperative pain. Participants will: * Undergo clinical and radiographic evaluation of primary mandibular molars requiring pulpectomy. * Be randomly allocated to one of three instrumentation groups: Kedo-Nano Plus rotary files, Kedo-S Square rotary files, or manual K-files. * Receive pulpectomy treatment using the assigned instrumentation technique. * Undergo radiographic assessment of obturation quality following treatment. * Have postoperative pain assessed using the Wong-Baker Faces Pain Rating Scale at 6, 12, 24, and 48 hours after treatment.