Endodontic plasma-jets for root-canal disinfection

Summary form only given. A plasma treatment for root-canal disinfection is expected to be substituted for the traditional methods for which some toxic antibacterial compounds such as sodium hypochlorite (NaOCl), chlor-hexidine (CHX), and others have been used with a tool of endodontic file (NiTi). Sometimes the toxic compound brings about the serious side-effects as a dropsical swelling around the root of a tooth, a massive swelling of the check, and an ecchymosis and a bruise on the side of face. A high attention should be paid to the perform irrigation as well as to apply a medicament for such a narrow, deep, and irregular-shaped root canals. Atmospheric pressure plasma jet possibly generates lots of reactive species comparable to conventional chemicals. Furthermore the treatment area can be focused narrowly and deeply without making sever toxic residues. For the last decade, a lot of jet-devices have been introduced and there have been some preliminary attempts to use a plasma-jet in endodontic practice but the completely sterilized results have not been reported yet.The purpose of this research is to develop an efficient device of a plasma jet system for dental surgery. We introduce a new concept of the jet-system combined with a dielectric barrier discharge, whose properties are as follows: (i) An Ar-jet device is operated by a remarkably low voltage with a sinusoidal frequency of several tens of kHz. Even in an air-jet device, the same electrode structure has been involved as that of an Ar-jet. (ii) To overcome the difficulty of approaching the deep and narrow irregular-cavity of rootcanal, a reliable and user-friendly plasma-jet device is needed. Our system is equipped with a proper structure of a hooked nozzle through which the plasma can be generated inside the canal. To prevent the infection during the operation, a disposable single-usage of the nozzle system is developed. (iii) Optical spectrum is analyzed to compare this jet-system to the conventional jets and to verify the effective radicals in killing bacteria. And finally, a bactericidal effect of this plasma jet on the Streptococcus mutants and Enterococcus faecalis as main pathogens in a root-canal is investigated in variously-designed 3-dimensional tooth model made by 3D printer or in extracted tooth.