Biological, Medical, and Agricultural Applications of Plasmas I

Cold Atmospheric-Pressure Plasma (CAP) jets are emerging as a promising tool in endodontics due to their ability to generate reactive oxygen and nitrogen species (RONS), relevant radiations, and electromagnetic fields at near-ambient temperatures. This study presents the design, characterization, and optimization of a bipolar pulsed powered CAP jet for plasma-mediated root canal irrigation. The dielectric barrier discharge-based CAP jet was optimised by varying applied voltage, frequency, and helium gas flow rate. The jet exhibited a transition from laminar to turbulent flow at helium flow rates exceeding 4 slpm, corresponding to a Reynolds number of ~400. Optical Emission Spectroscopy (OES) analysis identified key reactive species, while the collisional–radiative (CR) model confirmed a non-equilibrium plasma regime with electron density (nₑ ~ 10¹³ cm⁻³), electron temperature (Tₑ ~ 0.35 eV), and plasma gas temperature (Tg ~ 305 K) under optimized plasma discharge conditions (4 kV, 20 kHz, 4 slpm). The effectiveness of CAP treatment was evaluated on fifty-six extracted mandibular premolars, divided into four groups and prepared using ProTaper Universal hand files. Samples were irrigated with normal saline (control) or exposed to CAP jet for 2 min, 5 min, and 10 min, respectively. Scanning Electron Microscopy (SEM) imaging and microbial disinfection analysis revealed substantial smear layer removal and an approximately 5-log reduction in Enterococcus faecalis count. Safety parameters, including gas temperature, leakage currents, and ozone emissions, were assessed according to DIN-specification 91315 (General requirements for plasma sources in medicine). These findings highlight the potential of CAP technology in minimally invasive endodontic procedures, paving the way for further clinical translation and development in dental care.