Plasma Sterilization in Oral Cavity
Na Xie
1,*
, Lei Lu
1
, Xiaoting Ji
2
, Chengfang Tang
1
, Zixia Li
1
and Danyang Wang
1,*
1
School of Stomatology, Xi'an Medical University, Xi'an 710021, Shaanxi, China
2
Department of Stomatology, Affiliated Hospital of Shaanxi University of Traditional Chinese Medicine,
Xianyang, 712000, Shaanxi, China
*
Keywords:
Plasma Sterilization, Oral Hygiene, Sterilization Equipment, Inactivation Effect.
Abstract:
Nowadays, more and more people begin to pay attention to oral hygiene and health. Whether seeking medical
treatment for oral diseases, oral cosmetic treatment or routine oral examinations, the public's demand for
dental treatment is increasing, and oral treatment inevitably requires the use of dental diagnostic equipment.
The plasma sterilization method has gradually won the favor of people due to its advantages of energy saving,
environmental protection and high efficiency, and its sterilization effect has also been widely recognized in
the medical industry. Therefore, a plasma sterilization equipment for oral treatment is designed in this paper.
By analyzing the inactivation effect of the plasma equipment in treating oral bacteria, it is found that the
plasma sterilization method can effectively remove oral bacteria. Sterilization with this equipment can prevent
oral bacteria infect.
1 INTRODUCTION
The oral cavity is the gateway for microorganisms to
enter the human body. There are many kinds of
microorganisms and complex compositions in it. As
one of the common diseases, oral diseases can occur
in people of any age. Stomatology is also a high-risk
department for nosocomial infection, and risk factors
are ubiquitous, which deserves the attention of
doctors and patients.
At present, many scholars have conducted in-
depth research on the application of plasma
sterilization in the oral cavity, and have achieved
good results. For example, a drug administration
recognized the wider utility of the plasma
sterilization system and approved the use of the
system in the sterilization of more medical and
surgical instruments, indirectly promoting the plasma
sterilization system, making it the only sterilization
system in many health care facilities (Jain, 2021;
Navneet, 2018). A scholar's research on the quality of
disinfection and sterilization of dental clinics found
that there are still many problems in dental clinic
sterilization, such as failure to implement various
management systems, pollution of the diagnosis and
treatment environment, unreasonable layout of the
diagnosis and treatment environment, disinfection of
oral diagnosis and treatment instruments and
materials (Nobuya, 2018; Kuwahara, 2018).
Although there are many studies on the application of
plasma sterilization in the oral cavity, further
discussion is still needed on how to effectively extend
the plasma equipment to the practical application of
oral sterilization to solve the problem of oral
infection.
This paper first introduces the concept of plasma,
then explains some of its main parameters, then
expounds the mechanism of plasma sterilization, then
designs the overall structure of the plasma
sterilization equipment, and finally analyzes the
treatment of oral bacteria by the equipment. The
sterilization effect proves the effectiveness of the
plasma sterilization method.
2 AN OVERVIEW OF PLASMA
AND ITS STERILIZATION
MECHANISM
2.1 Main Parameters of Plasma
The main parameters of the plasma are:
(1) Plasma oscillation frequency
Xie, N., Lu, L., Ji, X., Tang, C., Li, Z. and Wang, D.
Plasma Sterilization in Oral Cavity.
DOI: 10.5220/0012013000003633
In Proceedings of the 4th International Conference on Biotechnology and Biomedicine (ICBB 2022), pages 57-60
ISBN: 978-989-758-637-8
Copyright
c
 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)
57

m
ne
s
e
e
p
θ
0
2
=
(1)
where
n
e
is the plasma free electron density; e and
m
e
are the electron charge and mass, respectively,
and
θ
0
is the dielectric constant in vacuum.
(2) Plasma collision frequency
300
7.2
7.1
10
10
19
11
T
n
F
n
en
×
×=
(2)








+=
T
n
T
T
n
F
e
i
e
e
i
ei
T
ln
3
1
280
ln
5.5
3/13/2
(3)
In a plasma,
F
en
is the electron-molecular
collision frequency,
F
ei
is the electron-ion collision
frequency,
n
n
and
n
i
are the densities of neutral
particles and positively charged ions, respectively,
and T and
T
e
are the ion temperature and electron
temperature, respectively.
2.2 Mechanism of Plasma Sterilization
Matter can transform from its normal solid, liquid and
gaseous states to a plasma state after absorbing
enough energy (Filippova, Korepanov, 2020). For
example, ice cubes absorb heat and turn into liquid
water, water turns into gaseous water vapor when
heated, and water vapor forms plasma when heated
continuously (Filippova, Karpov, 2020; Antonini,
2019).
(1) The role of ultraviolet light: In the process of
plasma formation, due to the transition of atoms, light
of different wavelengths will be emitted, most of
which are occupied by ultraviolet light. After
ultraviolet rays are absorbed and sterilized by
microorganisms, they can destroy or mutate their
genetic material (Dogan, 2019; Kawasaki, 2018).
(2) Etching effect of high-energy particles: Using
an electron microscope to observe the surface of
sterile objects, it can be seen that after bacteria and
viruses have been sterilized by plasma, their cellular
structure has been severely damaged and covered
with holes (Samoylova, 2019).
(3) Oxidation: NO produces an acid effect in the
solution, causing the pH of the medium to drop
sharply, killing the bacteria; OH will cause oxidation
in the presence of water, which can cause the
microbial membrane to perforate (Baldin, 2018;
Laroussi, 2018).
3 PLASMA STERILIZATION
EQUIPMENT DESIGN
3.1 Overall Structure Design of
Equipment
As shown in Figure 1, the overall structure of the
sterilization equipment mainly includes two modules,
the decibel is the embedded control module and the
power module.
Figure 1: Overall structure of plasma sterilization equipment.
ICBB 2022 - International Conference on Biotechnology and Biomedicine
58

3.2 Design of Plasma Power Module
The voltage stabilizer converts the direct current into
high frequency alternating current through the
connection of the drive bridge converter, the
alternating current is boosted by a high frequency
transformer, and finally the high frequency and high
voltage alternating current is sent to the sterilization
output chamber to generate glow discharge plasma.
4 APPLICATION OF PLASMA
STERILIZATION IN ORAL
CAVITY
4.1 Sterilization and Disinfection Effect
of Plasma Sterilization Equipment
The results are shown in Table 1. According to the
data results, when the oral bacteria were not subjected
to plasma sterilization, the number of colonies in the
petri dish was 63, the average number of bacterial
colonies after plasma sterilization for 1 s was 14, and
the average number of colonies for 3 s was 6.677 pcs.
Before 10s, the number of colonies decreased with
the increase of treatment time, when the treatment
time was 10s, the number of colonies was the least,
and after 10s, the number of colonies increased with
the increase of treatment time. That is to say, the
number of colonies in the petri dish does not
continuously decrease with time, but shows a trend of
first decreasing and then increasing, but it will not
exceed the number of untreated colonies, because the
sterilization activity of the plasma is reduced.
Table 1: Comparison of sterilization effects.
Processing
time
Average number of
colonies (indivual)
Standard
deviation
Not processed 63 8.269
1s 14 6.375
3s 6.677 4.082
5s 4.333 2.716
10s 1.211 0.327
15s 3.677 5.238
20s 5.832 11.558
4.2 The Effect of the Initial Density of
Oral Cells on Plasma Sterilization
This experiment tests the effect of different oral
initial bacterial densities on plasma sterilization. Oral
bacteria were suspended in 1.5L deionized water, and
the initial density of oral cells was set between
1*10
4
cfu/mL and 3*10
8
cfu/mL. The test results are
shown in Figure 2. When the initial density of oral
cells is 1*10
4
cfu/mL, it takes 0.14s to sterilize 100
oral bacteria using plasma equipment, 1.68s to
inactivate 1000 oral bacteria, and 10000 It takes 5.37s
to inactivate 100,000 oral bacteria, and 8.42s to
inactivate 100,000 oral bacteria. When 100 bacteria
need to be inactivated, it takes 0.36s to inactivate oral
bacteria with an initial density of 1.3*10
5
cfu/mL,
1.45s for oral bacteria with an initial density of
2.4*10
6
cfu/mL, and an initial density of 3*10
8
cfu/mL
oral bacteria inactivation takes 2.82s.
Figure 2: Bacterial inactivation time at different initial densities of oral cells.
Plasma Sterilization in Oral Cavity
59

5 CONCLUSION
In this paper, the application of plasma sterilization
in inactivating oral bacteria was studied, and a plasma
device was developed for secondary sterilization by
gas glow discharge. In this paper, an experiment was
carried out when the device was applied to oral
sterilization. One was to compare the number of
colonies in the petri dish without plasma equipment
sterilization treatment and the treated petri dish. The
second is to test the effect of the initial density of oral
cells on the sterilization effect, which proves that
when the initial density remains unchanged, the more
bacteria that need to be inactivated, the longer the
inactivation time; when the number of bacteria to be
inactivated remains unchanged, the higher the initial
density The bigger it is, the longer it takes to put out
the fire.
ACKNOWLEDGMENTS
This work was financially supported by the National
Natural Science Foundation of China (81701014);
the Key disciplines of Xi'an Medical University-
funding for clinical dentistry; Science and
Technology Plan Project of Science and Industry
Information Bureau of Weiyang District, Xi'an City
(202126); National Student Innovation and
Entrepreneurship Training Program Project
(202111840006); Shaanxi Provincial Student
Innovation and Entrepreneurship Training Program
Project (202111840006); Xi'an Medical University
Student Innovation and Entrepreneurship Training
Program Project (121521006)
REFERENCES
Antonini L M, Malfatti C, Reilly G C, et al. Effect of
sterilization processes on nanostructured Ti6Al4V
surfaces obtained by electropolishing [J]. Journal of
Materials Research, 2019, 34(8):1-8.
Baldin E, Garcia C, Henriques J, et al. Effect of sterilization
processes on the properties of a silane hybrid coating
applied to Ti6Al4V alloy [J]. Journal of Materials
Research, 2018, 33(2):161-177.
Dogan C, Oksuz A U, Maslakci N N, et al. Sterilization of
Natural Rose Water with Nonthermal Atmospheric
Pressure Plasma [J]. Arabian Journal for Science and
Engineering, 2019, 44(7):6403-6410.
Filippova E O, Korepanov V I, Pichugin V F. Effect of
Plasma Modification of Surface and Sterilization on
Optical Characteristics of Polyethylene Terephthalate
Track Membranes [J]. Technical Physics, 2020,
65(4):640-644.
Filippova E O, Karpov D A, Pichugin V F, et al. The
Investigation of the Influence of Low-Temperature
Plasma and Steam Sterilization on the Properties of
Track Membranes Made of Polyethylene Terephthalate
[J]. Inorganic Materials: Applied Research, 2020,
11(5):1116-1123.
Jain S S, Siddiqui D A, Wheelis S E, et al. Mammalian cell
response and bacterial adhesion on titanium healing
abutments: effect of multiple implantation and
sterilization cycles [J]. Clinical Oral Investigations,
2021, 25(5):2633-2644.
Kawasaki H, Yagyu Y, Ohshima T, et al. Sterilization for
Bacillus Subtilis var. natto by Low Pressure Sputtering
and Laser Ablation Plasma using Metal Powder
Target[J]. Transactions of the Materials Research
Society of Japan, 2018, 43(5):293-296.
Kuwahara T. Reduction in Energy Consumption Using
Fuel Cells in Nonthermal Plasma-Based Water
Sterilization by Bubbling Ozone [J]. IEEE Transactions
on Industry Applications, 2018, PP (6):1-1.
Laroussi M, Graves D, Keidar M. Editorial Plasma and
Cancer Treatment [J]. IEEE Transactions on Radiation
and Plasma Medical Sciences, 2018, 2(2):85-86.
Navneet, Grewal, Neha, et al. Comparison of resorption
rate of primary teeth treated with alternative lesion
sterilization and tissue repair and conventional
endodontic treatment: An in vivo randomized clinical
trial. [J]. Journal of the Indian Society of Pedodontics
and Preventive Dentistry, 2018, 36(3):262-267.
Nobuya H, Masaaki G, Tomomasa I , et al. Current Plasma
Sterilization and Disinfection Studies [J]. Journal of
Photopolymer Science and Technology, 2018,
31(3):389-398.
Samoylova M V, Kosyreva T F, Anurova A E, et al. Oral
cavity microbiocenosis assessment on the basis of
bacterial endotoxin and plasmalogens in a saliva by
method GAS-liquid chromatography-mass
spectrometry [J]. Klinicheskaia Laboratornaia
Diagnostika, 2019, 64(3):186-192.
ICBB 2022 - International Conference on Biotechnology and Biomedicine
60