RESUMO
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.
Assuntos
Humanos , Streptococcus mutans , Cárie Dentária/terapia , Esterilização , Temperatura , ÁguaRESUMO
Objective To compare the different doses of low-temperature plasma (LTP) on wound healing in BALB/c mice so as to discuss the effects of the optimal dose of low-temperature plasma dealing with wound in mice and the acting mechanism of wound healing.Methods Adoptatmospheric pressure plasma jet discharged by the dielectric barrier was used to treat mouse skin wound.According to the processing time, the wounds were divided into 10s, 20s, 30s, 40s and 50s experimental groups, while naturally healing wounds served as negative controls and the wounds dealt with recombinant human epidermal growth factor served as positive controls.We recorded the wound size every day, observed the histopathological changes, the expression level of type Ⅰ collagen by immunofluorescence, and analyzed the composition of low-temperature plasma jet.Results The wounds with plasma treatment time of 10s, 20s, 30s, and 40s showed significant daily improvement and almost complete closure at days 12, 10, 7, 13, respectively.However, the wounds with plasma treatment time of 50s remained unhealed atday 14.The wounds in positive control group all healed, and the wound healing effect in positive control group could be achieved in 30s group.HE staining and immunofluorescence staining assays showed the optimal result of epidermal cell regeneration, granulation tissue hyperplasia, and collagen deposition in histological aspect at day 7 in 30 s group.The low-temperature plasma jet contained highly reactive free radicals of nitrogen and oxygen, which play an important role in wound healing process.Conclusion Appropriate doses of cold plasma can accelerate wound healing whereas over-doses of plasma can suppress wound healing.The process of wound healing may be related to reactive oxygen and nitrogen species in LTP.
RESUMO
Recently,plasma sterilization has attracted increasing attention in dental community for the atmospheric pressure non-equilibrium plasma jet (APNPs),which is driven by a kilohertz pulsed DC power,may be applied to the dental and oral diseases.However,it is still in doubt whether APNPs can effectively kill pathogenic bacteria in the oral cavity and produce no harmful effects on normal oral tissues,especially on normal mucosa.The aim of this study was to evaluate the bacterial-killing effect of APNPs in the biofilms containing a single breed of bacteria (Porphyromonas gingivalis,Pg.),and the pathological changes of the oral mucosa after treatment by APNPs.Pg.was incubated to form the biofilms in vitro,and the samples were divided into three groups randomly:group A (blank control);group B in which the biofilms were treated by APNPs (the setting of the equipment:10 kHz,1600 ns and 8 kV); group C in which the biofilms were exposed only to a gas jet without ignition of the plasma.Each group had three samples and each sample was processed for up to 5 min.The biofilms were then fluorescently stained,observed and photographed under a laser scanning confocal microscope.In the animal experiment,six male Japanese white rabbits were divided into two groups randomly (n=3 in each group) in terms of the different post-treatment time (1-day group and 5-day group).The buccal mucosa of the left side and the mucosa of the ventral surface of the tongue were treated by APNPs for 10 min in the same way as the bacterial biofilm experiment in each rabbit,and the corresponding mucosa of the other sides served as normal control.The clinical manifestations of the oral mucosa were observed and recorded every day.The rabbits were sacrificed one or five day(s) after APNPs treatment.The oral mucosa were harvested and prepared to haematoxylin and eosin-stained sections.Clinical observation and histopathological scores were used to assess mucosal changes.The results showed the obvious P.g.biofilms were formed at 10 days,and most of the bacteria in groups A and C were alive under a laser scanning confocal microscope,but the bacteria in the group B were almost all dead.In animal experiment,no ulcers,anabrosis and oral mucositis were found in both the 1-day and 5-day groups.The average mucous membrane irritation index was -0.83 and -0.67 in the 1-day and 5-day groups,respectively,suggesting that no intense mucosal membrane irritation responses occurred.It was concluded that APNPs could effectively kill P.g.in the biofilms and did not cause any pathological changes in the normal mucosa,suggesting that the plasma jet (APNPs) may be applied to oral diseases as a novel sterilization device in the future.