Clinical Evaluation of Underwater Discharge Plasma as a Root Canal Irrigant: A Randomized Pilot Study on Efficacy and Safety

Background/Objectives: Root canal therapy (RCT) aims to eliminate intracanal infection and promote periapical healing through mechanical instrumentation and chemical disinfection. Conventional irrigants, such as sodium hypochlorite (NaOCl), are effective but may exhibit limited penetration into anatomically complex root canal systems and carry the risks of cytotoxicity if extruded beyond the apical foramen or into surrounding periodontal tissues. In this pilot study, we evaluated the clinical effectiveness and safety of underwater discharge plasma (UDP) as a biocompatible alternative to NaOCl for root canal irrigation. Methods: A prospective, randomized clinical trial was conducted involving 30 patients who required root canal treatment. Patients were randomly allocated to the UDP (n = 15) or NaOCl (n = 15) group. All treatments were performed by a single operator following standardized protocols. Pain was assessed using the visual analog scale (VAS), and periapical healing was evaluated using the Periapical Index (PAI) at baseline, 2 months, and 4 months. Statistical analyses included the Friedman test, Mann–Whitney U test, and Fisher’s exact test. Interobserver agreement for radiographic readings was evaluated using quadratic-weighted Cohen’s kappa coefficient. Results: A total of 28 patients completed the study. VAS scores significantly decreased over time in both groups (p < 0.05), with no significant difference between the groups at any time point (p > 0.05). At 4 months, radiographic healing was observed in 71.4% and 92.9% of patients in the UDP and NaOCl groups, respectively (p > 0.05). PAI score changes and clinical success rates were comparable between groups. No adverse effects or thermal damage was reported when using UDP. Conclusions: UDP demonstrated short-term clinical efficacy and safety comparable to that of NaOCl. Thus, UDP may serve as a biocompatible alternative for root canal disinfection. Further large-scale and long-term studies are warranted to confirm its clinical utility.