Antibacterial efficacy of non-thermal atmospheric plasma against Streptococcus mutans biofilm grown on the surfaces of restorative resin composites

[Study on the sterilization effect of plasma jet and plasma activated water on Streptococcus mutans]

To explore the effects of plasma jet (PJ) and plasma activated water (PAW) on the sterilization of Streptococcus mutans ( S. mutans) and compare the advantages and disadvantages of the two methods, so as to provide a basis for plasma treatment of dental caries and to enrich the treatment means of dental caries, an atmospheric pressure plasma excitation system was built, and the effects of PJ and PAW on the sterilization rate of S. mutans and the changes of temperature and pH during treatment were studied under different excitation voltage ( U e ) and different excitation time ( t e ). The results showed that in the PJ treatment, the difference in the survival rate of S. mutans between the treatment group and the control group was statistically significant ( P = 0.007, d=2.66) when U e = 7 kV and t e = 60 s, and complete sterilization was achieved at U e = 8 kV and t e = 120 s in the PJ treatment. In contrast, in the PAW treatment, the difference in the survival rate of S. mutans between the treatment group and the control group was statistically significant ( P = 0.029, d = 1.71) when U e = 7 kV and t e = 30 s, and complete sterilization was achieved with PAW treatment when U e = 9 kV and t e = 60 s. Results of the monitoring of temperature and pH showed that the maximum temperature rise during PJ and PAW treatment did not exceed 4.3 °C, while the pH value after PAW treatment would drop to a minimum of 3.02. In summary, the optimal sterilization parameters for PJ were U e =8 kV and 90 s < t e ≤ 120 s, while the optimal sterilization parameters for PAW were U e = 9 kV and 30 s< t e ≤ 60 s. Both treatment methods achieved non-thermal sterilization of S. mutans, where PJ required only a smaller U e to achieve complete sterilization, while at pH < 4.7, PAW only required a shorter t e to achieve complete sterilization, but its acidic environment could cause some chemical damage to the teeth. This study can provide some reference value for plasma treatment of dental caries.

Applications of Plasma Produced with Electrical Discharges in Gases for Agriculture and Biomedicine

The use of thermal and non-thermal atmospheric pressure plasma to solve problems related to agriculture and biomedicine is the focus of this paper. Plasma in thermal equilibrium is used where heat is required. In agriculture, it is used to treat soil and land contaminated by the products of biomass, plastics, post-hospital and pharmaceutical waste combustion, and also by ecological phenomena that have recently been observed, such as droughts, floods and storms, leading to environmental pollution. In biomedical applications, thermal plasma is used in so-called indirect living tissue treatment. The sources of thermal plasma are arcs, plasma torches and microwave plasma reactors. In turn, atmospheric pressure cold (non-thermal) plasma is applied in agriculture and biomedicine where heat adversely affects technological processes. The thermodynamic imbalance of cold plasma makes it suitable for organic syntheses due its low power requirements and the possibility of conducting chemical reactions in gas at relatively low and close to ambient temperatures. It is also suitable in the treatment of living tissues and sterilisation of medical instruments made of materials that are non-resistant to high temperatures. Non-thermal and non-equilibrium discharges at atmospheric pressure that include dielectric barrier discharges (DBDs) and atmospheric pressure plasma jets (APPJs), as well as gliding arc (GAD), can be the source of cold plasma. This paper presents an overview of agriculture and soil protection problems and biomedical and health protection problems that can be solved with the aid of plasma produced with electrical discharges. In particular, agricultural processes related to water, sewage purification with ozone and with advanced oxidation processes, as well as those related to contaminated soil treatment and pest control, are presented. Among the biomedical applications of cold plasma, its antibacterial activity, wound healing, cancer treatment and dental problems are briefly discussed.

Aurora Borealis in dentistry: The applications of cold plasma in biomedicine

Plasma is regularly alluded to as the fourth form of matter. Its bounty presence in nature along with its potential antibacterial properties has made it a widely utilized disinfectant in clinical sciences. Thermal plasma and non-thermal (or cold atmospheric) plasma (NTP) are two types of plasma. Atoms and heavy particles are both available at the same temperature in thermal plasma. Cold atmospheric plasma (CAP) is intended to be non-thermal since its electrons are hotter than the heavier particles at ambient temperature. Direct barrier discharge (DBD), atmospheric plasma pressure jet (APPJ), etc. methods can be used to produce plasma, however, all follow a basic concept in their generation. This review focuses on the anticipated uses of cold atmospheric plasma in dentistry, such as its effectiveness in sterilizing dental instruments by eradicating bacteria, its advantage in dental cavity decontamination over conventional methods, root canal disinfection, its effects on tooth whitening, the benefits of plasma treatment on the success of dental implant placement, and so forth. Moreover, the limitations and probable solutions has also been anticipated. These conceivable outcomes thus have proclaimed the improvement of more up-to-date gadgets, for example, the plasma needle and plasma pen, which are efficient in treating the small areas like root canal bleaching, biofilm disruption, requiring treatment in dentistry.

•

Non-thermal plasma (NTP) has regarded as an important tool for biomedical application especially dental application.

•

The surface application of NTP can be used for disinfecting microbial infection in endodontic issues.

•

NTP can be used to eradicate the microorganism biofilm responsible for dental caries.

•

NTP can also be utilized in would healing, implant modifications and adhesive restoration.

•

NTP is potential candidate for clinical application in dentistry based on the experimental proofs.