Comparison Study of Plasma-Activated Water and Plasma Jet Effects on Escherichia coli Bacteria for the Disinfection of Tooth Root Canal

Abstract

This study compares the effects of plasma jet and plasma-activated water on teeth root canals contaminated with Escherichia coli bacteria. A plasma jet system was developed for biological purposes that operate at atmospheric pressure. The plasma jet works with argon gas and is generated by a power supply, which supplies a sinusoidal alternating voltage of 12 kV of 20 kHz frequency. The system was optically diagnosed, as it was found that the peaks of the nitrogen spectrum were obtained at the wavelength (300- 450) nm with the appearance of hydroxide peaks at 380 nm. Extracted teeth with one root canal were used, which were contaminated with bacteria and divided into two groups to be treated with a plasma jet and plasma-activated water. The first group was treated with a plasma jet at a gas flow of 2.5 L/min with a change of treatment time from 0.5 to 3 minutes. The number of killed bacteria colonies increased when the exposure time increased (2.7×10⁸ CFU per mL - 0), and the total killing of bacteria was obtained at 3 minutes treatment time. While the second group was treated with plasma-activated water; the water used to kill the bacteria was treated with plasma for one hour at a gas flow rate of 1 L/min. The measured concentrations of (NO2, NO3, and H2O2) of this water were (10, 100 and 200) ppm. The teeth were treated with plasma-activated water for different times that ranged between (5- 35) minutes. Different bacterial killing rates were obtained at these times, and the total bacterial killing rate was obtained for 35 minutes of treatment time. The obtained results found that the response of bacteria to treatment with plasma jet is better than treatment with plasma-activated water.