Atmospheric Pressure Room-temperature Plasma Jets(RT-APPJs) And Their Applications In Root Canal Treatment

Atmospheric pressure room-temperature plasma jets have great potential in biomedical applications. On one hand, they could be generated in latm pressure at room temperature; on the other hand, plasma jets device create plasmas in the surrounding air, thus avoid the limit by the space size, which is critical for the industrial application such as plasma medicine. Nowadays, lots of works of RT-APPJs applications been done on sterilization and disinfection, skin disease treatment, blood coagulation, cancer cell apoptosis, stomatology, etc. Applications of RT-APPJs on stomatology contain the treatment of decayed tooth, periodontal disease, oral mucosa disease and tooth bleaching, etc. The application on oral clinic is not mature this time. The inactivation effect and the mechanism of atmospheric pressure cold plasma jet on oral pathogenic microorganisms as well as the plasma bio-safety are studued mainly though experiments. In addition, combined with clinical practice, the treatment conditions of oral diseases, especially root canal treatment are improved.Detailed comtents are presented as follows:1. Development of atmospheric low temperature plasma sources for biomedical use especially for root canal treatment,(i) Noble gas RC plasma needle driven by DC pulsed power supply. The high voltage electrode is made by injection needle, connected to the power supply through a series of resistance and capacitance. This device could directly generate safe room-temperature plasma inside the root canal with the gas temperature about300K, thus the active species could be gathered inside the root canal, which improves the treatment efficiency,(ii) Air RC plasma needle driven by DC pulsed power supply. This device directly uses the surrounding air as the working gas. This structure omits the complicated gas circuit, making the device much smarter, and cuts the cost as well.2. Plasma diagnoses, the roles of different species in the sterilization process and the optimization of the treatment conditions. Optical emission spectrometry, laser-induced fluorescence spectroscopy, the NO detection kits and other methods are used to measure the content of active species (OH, NO and UV, etc) in the plasma jets. Focusing on the OH and O which contribute a lot in the microorganism inactivation, the absolute concentration of OH in the4kinds of plasma jet device and the O two-phone absorption laser-induced fluorescence intensity was measured and found to could be as high as2.4×1013cm-3. By changing the voltage amplitude, frequency, pulse width, gas components and gas flow velocity, etc, the spatial and temporal distribution OH and O density and was measured and the inactivation effect was compared. It was found that N*, He*and their ions as well as electron had little effect on the inactivation, while the Reactive oxygen species (such as OH, O, etc) and the negative ions of O played the significant role, which made a strong support for the plasma application in Stomatology.3. Effect and treatment condition optimization of plasma jets on typical planktonic pathogens in oral cavity. For the oral cavity disease especially for the root canal treatment, the inactivation effects were tested on2typical pathogenic bacteria (Enterococcus faecalis and Porphyromonas gingivalis), a typical fungus (Candida alicans) and2kinds of virus (adenovirus and HSV I). Results showed that plasma has a good effect on the various types of oral pathogenic microorganisms, and the anti-plasma ability was different for different microorganisms. Structure changes of microbial cells were observed before and after the plasma treatment. It is found that plasma treatment damaged the cell skeleton structure which caused the cytoplasm loss, and the active species directly interact with the genetic material to cause cell death. In addition, the plasma etching effect could even completely disintegrate the cells and became fragment.4. Study on the inactivation of pathogen biofilms. Single bacteria biofilm (Enterococcus faecalis and Porphyromonas gingivalis biofilm) and the mixed pathogen biofilm of oral cavity on were successfully inactivated with high efficiency. The penetrating ability of plasma was investigated, and the treatment effect was compared with that of the traditional antibiotic (like Chlorhexidine). It is found that plasma could penetrate at least40μm biofilm within5min, and the effect could be even improved by working gas through the drug solution (Chlorhexidine, etc).5. Study on the root canal treatment by plasma jet. Using both the tooth root canal model and the real human teeth to inoculate tooth root canal diseases, combining with clinical practice, the therapeutic effects were further enhanced by washing with normal saline and drugs. It is found that12min pure plasma treatment can decreaseapproximately5magnitudes of bacteria number inside the root canal model, and aiding by saline washing and mixed with5.25%NaCLO in the working gas,12min plasma treatment can even make6magnitudes decreases. In the treatment of real root canal,15min plasma treatment can also decrease three orders of magnitude. And15min plasma treatment with2%Chlorhexidine after soaked in2%CHX showed better effect with the amount of the bacteria inside the root canal decreasing4orders of magnitude.6. Study on the biological safety of plasma jets. Osteoblasts cultured in vitro, rabbit buccal mucosa/tongue mucosa and golden hamster oral cheek pouch mucosa were tested by plasma treatments. It is found that anti-plasma ability of cells cultured in vitro was far weaker than the animal cell tissues. By adding a layer of liquid on the osteoblast surface, it can greatly reduce the plasma effect on cell activity. The rabbit and hamster oral mucosa biopsy after10min plasma and drug-enhanced plasma treatment showed that plasma treatment will bring no harm to the cell tissue, indicating that plasma is safe for both animal and human being.7. Plasma oral cpmprehensive therapeule apparatus development. This apparatus could treat root canal, peri-implantitis, periodontal disease, gingivitis, decayed tooth, and dental ulcer, etc. The power supply and gas circuit are integrated inside a chest, and the control panel adopts LCD display. The voltage amplitude, frequency and the gas flow velocity could be adjusted according to different uses. The structure of the handle is similar to the dental handpiece with high insulation performance. When certain high votage is loaded, the atmospheric pressure plasma jet could be generated as long as several cn. Additionally, the plasma3D size could be changed as required through changing the nozzle.