Enterococcus faecalis (E.faecalis)is a microorganism that can survive extreme challengesin obturated root canals.The aim of this study was to evaluate the efficacy of a non-thermalatmospheric pressure plasma plume against E.faecalis in vitro.A non-thermal atmospheric pressureplasma jet device which could generate a cold plasma plume carrying a peak current of300 mA was used.The antibacterial efficacy of this device against E.faecalis and its biofilm underdifferent conditions was detected.The antibacterial efficacy of the plasma against E.faecalisand Staphylococcus aureus (S.aureus)was also evaluated.After plasma treatment,the averagediameter of inhibition zone on S.aureus and E.faecalis was 2.62±0.26 cm and 1.06±0.30 cm,respectively (P < 0.05).The diameter was increased with prolongation of the treatment duration.The diameters of inhibition zone of the sealed Petri dishes were larger than those of theuncovered Petri dishes.There was significant difference in colony-forming units between plasmagroup and control group on E.faecalis biofilm (P < 0.01).The transmission electron microscopyrevealed that the ultrastructural changes cytoderm of E.faecalis were observed after treatmentfor 2 min.It is concluded that the non-thermal atmospheric pressure plasma could serve as aneffective adjunct to standard endodontic microbial treatment.
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,P.g.),and the pathological changes of the oral mucosa after treatment by APNPs.P.g.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 group
