Plasma Needle: An Atmospheric Plasma Jet for Dentistry

Summary form only given. Motivated by possible dental applications for disinfecting teeth, a small low-power radiofrequency plasma jet was developed by Sladek et al. We have performed tests with a similar device. This so-called plasma needle consists of a metal wire, 200 microns diameter, with a sharp tip. Helium at atmospheric pressure flows coaxially with the needle tip at 1.5 m/s. This helium flow entrains nitrogen and other atmospheric gases at the end of the plasma jet nozzle, where the gas mixes with the atmosphere. Radio-frequency voltage at approximately 7 MHz is applied through a matching network, creating a millimeter-size plasma jet that flows toward a sample. The sample tested was a glass Petri dish, with and without a bacterial culture, resting on a grounded metal plate. The separation between the needle tip and the sample is approximately 2 mm. It is thought that radicals produced from atmospheric gas molecules will kill bacteria. To characterize the plasma jet, we imaged the glow using a digital CCD camera. To reveal the internal structure of the plasma, we also prepared Abel-inverted images. Bacteriology tests will be performed using cultures provided by the University of Iowa´s College of Dentistry. These bacteriology tests are intended to demonstrate efficacy in killing a colony of bacteria of a type found commonly on human teeth.