Clinical efficacy of rotary versus manual instrumentation in pulpectomy for mandibular primary molars: a focus on operative efficiency and postoperative pain in children

Background Dental caries, one of the most prevalent chronic diseases in childhood, frequently leads to pulp involvement in primary molars, necessitating pulpectomy to preserve oral function and support craniofacial development. The complex anatomy of primary teeth and limited cooperation of pediatric patients pose significant challenges to conventional treatment. This retrospective study compared the clinical efficacy of two pediatric rotary file systems (M3 and S3) combined with ultrasonic irrigation versus manual K-files in pulpectomy of mandibular primary molars, with emphasis on instrumentation efficiency, obturation quality, postoperative pain, and therapeutic outcomes. Methods A single-center analysis was conducted involving children aged 4–9 years treated at the Pediatric Dentistry Clinic of the Third Hospital of Hebei Medical University. Participants were divided into three groups according to instrumentation method: M3 rotary files (n = 98), S3 rotary files (n = 84), and manual K-files (n = 78). Instrumentation time was recorded digitally. Obturation quality was radiographically rated as optimal, underfilled, or overfilled. Postoperative pain was assessed using the Wong-Baker FACES scale at 24, 48, and 72 hours. Clinical and radiographic evaluations at 6 months classified outcomes as success, improvement, or failure. Results The M3 rotary group demonstrated the shortest instrumentation time (210.45 ± 6.85 seconds) and the highest rate of optimal obturation (87.1%), significantly exceeding the S3 and manual file groups ( P  < 0.05). Both rotary systems resulted in significantly lower pain scores at 24 and 48 hours compared to manual instrumentation ( P  < 0.01), though no significant differences were observed at 72 hours or in 6-month success rates across groups ( P  > 0.05). Conclusions The use of pediatric rotary file systems—particularly the 0.04 tapered M3 instrument—combined with ultrasonic irrigation significantly enhanced pulpectomy efficiency, improved obturation quality, and reduced early postoperative pain in children. By shortening operative time and alleviating discomfort, this integrated approach not only facilitates clinical workflow but also promotes a more positive dental experience for young patients—an essential consideration in pediatric public health and patient-centered care.