Tooth root canal is often a complex system composed of a central area and lateral parts. Endodontic infections are caused by microorganisms, usually bacteria, residing in the root canal system of the affected tooth. A variety of different measures has been used to eradicate root canal bacteria, including chemomechanical instrumentation techniques, irrigation, and intracanal medicaments. However, it has been shown that complete eradication of microorganisms is difficult to achieve. Therefore, new methods are continuously being developed to eradicate all bacteria and secure healing. Atmospheric-pressure nonequilibrium plasma jets (APNP-Js) have been shown to be able to kill bacteria effectively. APNP-Js can generate various high density reactive species including oxygen, hydroxide, ozone, and nitrogen oxide while keeping the gas temperature of the plasma at room temperature. Such reactive species could kill bacteria when they are in contact with bacteria. To develop the new technology of using plasma for root canal treatment, progress on using APNP-Js to kill bacteria in planktonic culture and single-species and multispecies biofilms in root canal is discussed. Finally, the progress of first prototype of plasma for root canal treatment device is presented.