ABSTRACT
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 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.
ABSTRACT
The present study evaluated the effect of non-thermal plasma on skin wound healing in BalB/c mice. Two 6-mm wounds along the both sides of the spine were created on the back of each mouse (n=80) by using a punch biopsy. The mice were assigned randomly into two groups, with 40 animals in each group: a non-thermal plasma group in which the mice were treated with the non-thermal plasma; a control group in which the mice were left to heal naturally. Wound healing was evaluated on postoperative days (POD) 4, 7, 10 and 14 (n=5 per group in each POD) by percentage of wound closure. The mice was euthanized on POD 1, 4, 7, 10, 14, 21, 28 and 35 (n=1 in each POD). The wounds were removed, routinely fixed, paraffin-embedded, sectioned and HE-stained. A modified scoring system was used to evaluate the wounds. The results showed that acute inflammation peaked on POD 4 in non-thermal plasma group, earlier than in control group in which acute inflammation reached a peak on POD 7, and the acute inflammation scores were much lower in non-thermal group than in control group on POD 7 (P10(12) CFU/mL on the POD 7) (P<0.05). It was suggested that the non-thermal plasma facilitates the wound healing by suppressing bacterial colonization.