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The bright future of dentistry with cold plasma – Review

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IOSR Journal of Dental and Medical Sciences (IOSR-JDMS)
e-ISSN: 2279-0853, p-ISSN: 2279-0861.Volume 13, Issue 10 Ver. IV (Oct. 2014), PP 06-13
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The bright future of dentistry with cold plasma Review
Dr. Shailja Singh1, Dr. Ramesh Chandra2, Dr. Supratim Tripathi3,
Dr. Hena Rahman4, Dr. Payal Tripathi5, Dr. Amisha Jain6, Dr. Pulkit Gupta7
1Reader, Career Post Graduate Institute of Dental Sciences & Hospital Lucknow, UP, INDIA.
2Professor, Career Post Graduate Institute of Dental Sciences & Hospital Lucknow, UP, INDIA
3,4,5Sr. Lecturer, Career Post Graduate Institute of Dental Sciences & Hospital Lucknow, UP, INDIA
6,7P.G. Student, Career Post Graduate Institute of Dental Sciences & Hospital Lucknow, UP, INDIA
Abstract: - Plasma is the fourth state of matter and other states of matter are liquid, gas, and solid4. Plasma
occurs as a natural phenomenon in the universe in the form of fire, in the polar aurora borealis and in the
nuclear fusion reactions of the sun and also can be created artificially which has gained importance in the fields
of plasma screens or light sources1. There are two types of plasma: thermal and non-thermal or cold
atmospheric plasma. Thermal plasma has electrons and heavy particles (neutral and ions) at the same
temperature. Cold Atmospheric Plasma (CAP) is said to be non-thermal because it has electron at a hotter
temperature than the heavy particles that are at room temperature. . Cold Atmospheric Plasma is a specific type
of plasma that is less than 104°F at the point of application4. So the bright future of dentistry with help of cold
plasma.
Key word:- cold plasma, non thermal atmospheric plasma,
I. Introduction
The British physicist Sir William Crookes identified the fourth state of matter in 1879. It was termed
“plasma” by Irving Langmuir in 1929. Plasma is a collection of stripped particles. When electrons are stripped
from atoms and molecules, those particles change state and become plasma. Plasmas are naturally energetic
because stripping electrons takes constant energy. If the energy dissipates, the electrons reattach and the plasma
particles become a gas once again1. Plasma, referred to as the fourth state of matter. The other states of matter
are liquid, gas, and solid (Figure 1)4.
Physical plasma is defined as a gas in which part of the particles are present in ionized form. This is
achieved by heating a gas which leads to the dissociation of the molecular bonds and subsequently ionization of
the free atoms. Thus, plasma consists of positively and negatively charged ions and negatively charged electrons
as well as radicals, neutral and excited atoms and molecules2&3
Plasma not only occurs as a natural phenomenon as seen in the universe in the form of fire, in the polar
aurora borealis and in the nuclear fusion reactions of the sun but also can be created artificially which has gained
importance in the fields of plasma screens or light sources1.
There are two types of plasma: thermal and non-thermal or cold atmospheric plasma. Thermal plasma
has electrons and heavy particles (neutral and ions) at the same temperature. Cold Atmospheric Plasma (CAP) is
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said to be non-thermal because it has electron at a hotter temperature than the heavy particles that are at room
temperature. CAP is a specific type of plasma that is less than 104°F at the point of application4.
II. History
The English physicist Sir William Crookes identified plasmas in 1879, although it was an American
physicist, Dr Irving Langmuir who first applied the word „plasma‟ to ionized gas in 1929. In the late 1850s, the
Siemens company used plasma discharge to generate ozone, which acted as an agent to remove contaminants
and toxins from water. Nevertheless, for the next 100 years, little research was conducted exploring the
relationship between plasma and biological cells. From the 1960s to 1980s, plasmas were mainly utilized as a
secondary agent to indicate biological sterilization, yet diminutive cause and effect knowledge was advanced. It
was not until the mid- 1990s that scientists made considerable progress in cold plasma technology. As the news
of plasma science spread, visionary researchers took notice and began to explore various ways to utilize
plasma‟s unique properties. Plasma science was in its infancy in the 1990s, but by 1997, multidisciplinary teams
set out to understand the effects that plasmas had on pathogenic and nonpathogenic microorganisms, as well as
develop proof of concept studies to demonstrate that plasma could be used as a decontaminant or sterilizing
agent. Since the late 1990s, plasma research has evolved at a rapid pace as technology expanded into areas, such
as biomedical, environmental, aerospace, agriculture and the military5&6.
Non Thermal Atmospheric Plasma
Low temperature plasma, also known as cold plasma, is used in the modification of biomaterial
surfaces. It is characterised by a low degree of ionization at low or atmospheric pressure 7-9. Low temperature
plasma is created by the conversion of a compound into gas followed by ionization by applying energy in the
form of heat, direct or alternating electric current, radiation or laser light. Oxygen, nitrogen, hydrogen or agon
are the commonly used plasma gas sources. In material science, the possible applications of low-temperature
plasmas include the modification of surface properties like electrochemical charge or amount of oxidation as
well as attachment or modification of surface-bound chemical groups. Consequently, properties like hardness,
resistance to chemical corrosion or physical abrasion, wettability, the water absorption capacity as well as the
affinity towards specific molecules can be modulated specifically and precisely by the use of low temperature
plasmas10 . Non-thermal Atmospheric Plasmas are very efficient in the deactivation of bacteria. A relatively new
area is the use of these plasmas in dental applications. Plasma treatment is potentially a novel tissue-saving
technique, allowing irregular structures and narrow channels within the diseased tooth to be cleaned. Low-
temperature plasma is a promising method for destroying microorganisms, an alternative to conventional
methods which have numerous drawbacks11.
III. Mechanism Of Generation Of Cold Plasma
Plasmas can be produced by various means, e.g. radio frequency, microwave frequencies, high voltage
ac or dc, etc. The main body of the device is made of a medical syringe and a needle. They are used for guiding
the gas flow. The needle also serves as the electrode, which is connected to a high-voltage (HV)
submicrosecond pulsed direct-current (dc) power supply (amplitudes of upto 10 kV, repetition rate of upto 10
kHz, and pulse width variable from 200 ns to dc) through a 60- ballast resistor R and a 50-pF capacitor C,
where both the resistor and the capacitor are used for controlling the discharge current and the voltage on the
needle. Because of the series-connected capacitor and the resistor, the discharge current is limited to a safety
range for a human. It is found that, if the resistance of R is too small or the capacitance of C is too large, there is
feeling of weak electric shock when the plasma is touched by a human [12]. The diameter of the syringe is about
6mm, and the diameter of the syringe nozzle is about 0.7mm. The needle has an inner diameter of about 200μm
and a length of 3cm. Working gas such as He, Ar, or their mixtures with O2 can be used. The gas flow rate is
controlled by a mass-flow controller12. When working gas such as He/O2 (20%) is injected into the hollow
barrel of the syringe with a flow rate of 0.4 L/min and the HV pulsed dc voltage is applied to the needle,
homogeneous plasma is generated in front of the needle. finger can directly contact with the plasma or even with
the needle without any feeling of warmth or electric shock. Therefore, this device is safe for the application of
root-canal disinfection12.
IV. Methods Of Production
Several different types of CAP have been developed for biomedical uses. Energy is needed to produce
and maintain plasma. Thermal, electric, or light energy can be used. Usually, the discharge needed to produce
CAP is induced electrically. Some methods used to produce CAP include: Dielectric Barrier Discharge (DBD),
Atmospheric Pressure Plasma Jet (APPJ), Plasma Needle, and Plasma Pencil.
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Dielectric Barrier Discharge
In 1857, Siemens was first to conduct experiments on Dielectric Barrier Discharge (DBD). DBD has
many applications including: sterilization of living tissue, bacteria inactivation, angiogenesis, surface treatment,
and excimer formation13,14. The dielectric barrier discharge (DBD) consists of two flat metal electrodes that are
covered with dielectric material. A carrier gas moves between the two electrodes and is ionized to create plasma.
One electrode is a high voltage electrode and the other is a grounded electrode. High voltages are required to
produce the discharge needed to create the plasma. Alternative Current (AC) high voltages generally drive
DBD‟s with frequencies in the kHz range. The power consumption is between 10 and 100 W15. There are many
variations in the configuration of the electrodes, but the concept behind them all remains the same. For example,
some electrodes are cylindrical instead of flat and sometimes the dielectric material covers only one electrode
instead of both. More recently, Fridman et al. developed the floating electrode DBD (FE-DBD)16. It is similar to
the original DBD and consists of two electrodes: an insulated high voltage electrode and an active electrode.
The difference between FE-DBD and DBD is that the second electrode is not grounded; it is active meaning that
the second electrode can be human skin, a sample, and even an organ. The powered electrode needs to be close
to the surface of the second electrode (< 3mm) to create the discharge. It has been used on endothelial cells,
melanoma skin cancer, and blood coagulation. It has also been used in living tissue sterilization and in
deactivation of Bacillus stratosphericus (Figure 2)17. Plasma jets using a DBD system have also been created18
.
Plasma Jet-Radio Frequency Plasma Jets
One type of plasma jet, which is employed for bacterial sterilization, is the Atmospheric Pressure
Plasma Jet (APPJ)19. The APPJ consists of two coaxial electrodes between which a feed gas (mixtures of
helium, oxygen, and other gases) flows at a high rate. The outer electrode is grounded while Radio Frequency
(RF) power (50-100W) at 13.56 MHz is applied to the central electrode that creates a discharge. The reactive
species produced exits the nozzle at high velocity and arrives to the area that is to be treated. APPJ has been
used for the inactivation of several micro-organisms20-23. Koinuma et al. developed the earliest RF cold plasma
jet in 199224. The cathode is a needle electrode made of tungsten or stainless steel with a 1 mm diameter
connected to a RF source (13.56 MHz). The needle electrode lies within a quartz tube whereas the anode
electrode is grounded. Depending on the application, helium or argon was mixed with various gases. This group
published several papers describing its variants and applications of the plasma jet25,26. In 2002, Stoffels et al.
created a miniature atmospheric plasma jet that they called plasma needle27and created a new version in 200428.
In the former version, the needle was enclosed in a box and as a result, the samples had to be placed inside of
the box to be treated. In the new version, the plasma needle consists of a 0.3 mm metal strand diameter with a
sharpened tip inside of a Perspex tube. The length of the entire needle is 8 cm and 1.5 cm remains uncovered by
the Perspex tube. The gas used most frequently is Helium due to its high thermal conductivity. The gas is then
mixed with air at the needle tip where a micro discharge is created. Gases other than Helium are also used29. The
diameter of the plasma glow generated is 2 mm. Microplasma is created when RF power at 13.05 MHz ranging
between 10 mW and several watts is applied to the needle. Its small size enables it to be used to treat small areas
where accuracy is required like in dentistry30,31. It has also been used to deactivate E. Coli (Figure 3)32.
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Pulsed Direct Current-Driven Plasma Jets
Laroussi et al. developed a miniature jet that they called plasma pencil33. It consists of a dielectric
cylindrical tube of 2.5 cm in diameter where two disk electrodes of the same diameter as the tube are inserted.
The two electrodes are separated by a gap (the distance can vary from 0.3 to 1 cm) and consist of a thin copper
ring attached to a dielectric disk. To create the plasma, sub-microsecond high voltage pulses are applied
between the two electrodes while a gas is injected through the holes of the electrodes. When the discharge is
created, a plasma plume is launched through the hole of the outer electrode into the air. Because the plasma
plume (up to 5cm in length) remains at low temperature (290K), it can be touched safely. The electrical power is
supplied to the electrodes by a high voltage pulse generator. The high voltage is supplied to the pulse generator
by a DC voltage supply with variable output. The plasma pencil has been used in the treatment of E. coli,
Leukemia cells, and P. Gingivalis34. Forster et al., Zhang et al., and Wash et al. developed a plasma jet using a
DBD configuration (Figure 4)35,36.
Applications Of Cold Atmospheric Plasma In Dentistry
Sterilization by eradication of bacteria. The sterilization efficacy of plasma devices is influenced by gas
composition, driving frequency, and bacterial strain, but plasma devices have shown to kill a higher proportion
of bacteria than do conventional non-thermal methods such as UV sterilization37,38. The mechanism of plasma
sterilization is related to the abundance of plasma components, like reactive oxygen species, ions and electrons,
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and UV and electromagnetic fields39. Also, plasma can affect not only the contacted point but also the area
around it. Recently, plasma sterilization has been used to treat dental diseases40. The risk of prior transmission
through surgical instruments is of both current public and professional concern. The use of plasma
decontamination of surgical instruments is limited. Whittaker et al. has indicated that the use of gas plasma
cleaning may be extremely beneficial in reducing the absolute amount of proteinaceous materials that may be
transferred between patients when endodontic files are reused41. Yang Hong Li et al. stated that plasma
sterilization, with the advantage of low temperature, fastness, thoroughness, safety, overcomes the deficiency of
the traditional sterilization technology, and may become a novel method for killing microbe42. Autoclaves and
UV sterilizers are presently used to sterilize dental instruments. To develop a dental sterilizer which can sterilize
most materials, such as metals, rubbers, and plastics, the sterilization effect of an atmospheric pressure non-
thermal air plasma device was evaluated by Su-Jin Sung et al. It was proved that the atmospheric pressure
nonthermal air plasma device was effective in killing both Escherichia coli and Bacillus subtilis, and was more
effective in killing Escherichia coli than the UV sterilizer43.
Plasma In Dental Cavities
Plasma can treat and sterilize irregular surfaces; making them suitable for decontaminating dental
cavities without drilling. Although, plasma itself is superficial, the active plasma species it produces can easily
reach inside of the cavity. This approach was pioneered by Eva Stoffels, who suggested the use of plasma
needles in the dental cavity on the basis of the ability of plasma to kill Escherichia coli44. Goree et al., provided
substantial evidence that non thermal atmospheric plasmas killed Streptococcus mutans, a gram-positive
cariogenic bacterium45. Sladek et al., studied the interactions of the plasma with dental tissue using a plasma
needle44. It is an efficient source of various radicals, which are capable of bacterial decontamination; but, it
operates at room temperature and thus, does not cause bulk destruction of the tissue. Raymond EJ et al., studied
the interactions of the plasma with dental tissue using a plasma needle. Cleaning and sterilization of infected
tissue in a dental cavity or in a root canal can be accomplished using mechanical or laser techniques. However,
with both approaches, heating and destruction of healthy tissue can occur. A plasma needle is an efficient source
of various radicals, which are capable of bacterial decontamination; however, it operates at room temperature
and thus, does not cause bulk destruction of the tissue. From his research he concluded that plasma treatment is
potentially a novel tissue-saving technique, allowing irregular structures and narrow channels within the
diseased tooth to be cleaned11.
Intraoral Diseases
Oral candidiasis includes Candida-associated denture stomatitis, angular stomatitis, median rhomboid
glossitis, and linear gingival erythema. Koban et al. and Yamazaki et al. reported the high efficiency of Candida
albicans sterilization using various plasmas. Their result indicates the possibility that stomatitis caused by
Candida albicans can be cured by plasma jets46,47.
Root Canal Sterilisation
Lu et al., used a reliable and user-friendly plasma-jet device, which could generate plasma inside the
root canal. The plasma could be touched by bare hands and directed manually by a user to place it into root
canal for disinfection without causing any painful sensation. When He/O2(20%) is used as working gas, the
rotational and vibrational temperatures of the plasma are about 300 K and 2700 K, respectively. The peak
discharge current is about 10 mA. Preliminary inactivation experiment results showed that it can efficiently kill
Enterococcus faecalis, one of the main types of bacterium causing failure of root-canal treatment in several
minutes48. Pan et al., investigated the feasibility of using a cold plasma treatment of a root canal infected with
Enterococcus faecalis biofilms in-vitro. It was concluded that the cold plasma had a high efficiency in
disinfecting the Enterococcus faecalis biofilms invitro dental root canal treatment.
Use of Plasma in Composite Restorations
Preliminary data has also shown that plasma treatment increases bonding strength at the dentin/
composite interface by roughly 60%, and with that interface-bonding enhancement to significantly improve
composite performance, durability, and longevity. Current clinical practice relies on mechanical bonding when
it should rely on chemical bonding. The culprit that foils mechanical methods is a protein layer, the so-called
“smear layer,” which is primarily composed of type I collagen that develops at the dentin/adhesive junction. To
create a porous surface that the adhesive can infiltrate, current preparation techniques etch and demineralise
dentin. Interactions between demineralised dentin and adhesive gives rise to the smear layer, which actually
inhibits adhesive diffusion throughout the prepared dentin surface. This protein layer may be responsible, in
part, for causing premature failure of the composite restoration. It contributes to inadequate bonding that can
leave exposed, unprotected collagen at the dentin- adhesive interface, allowing bacterial enzymes to enter and
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further degrade the interface and the tissue11. Kong et al., investigated the plasma treatment effects on dental
composite restoration for improved interface properties and their results showed that atmospheric cold plasma
brush (ACPB) treatment can modify the dentin surface and thus increase the dentin/adhesive interfacial bonding.
The solution is to introduce bonds that depend on surface chemistry rather than surface porosity49.
Plasma In Tooth Bleaching
A non thermal, atmospheric pressure, helium plasma jet device was developed to enhance the tooth
bleaching effect of hydrogen peroxide (H 2O 2). Combining plasma and improved the bleaching efficacy by a
factor of 3 compared with using H 2O 2 alone. Tooth surface proteins were n H 2O 2oticeably removed by plasma
treatment. When a piece of tooth was added to a solution of H 2O 2as a catalyst, production of OH after plasma
treatment was 1.9 times greater than when using H 2O 2 alone. It is suggested that the improvement in tooth
bleaching induced by plasma is due to the removal of tooth surface proteins and to increased OH production50 .
Nam et al., used a plasma jet on 40 extracted human molar teeth with intact crowns. The 40 teeth were randomly
divided into four groups (n=10) and were treated with Carbamide peroxide + CAP, Carbamide peroxide +
Plasma Arc Lamp (PAC), Carbamide peroxide + diode laser, or Carbamide Peroxide alone (control). They
observed CAP was the most effective at bleaching teeth. Moreover, they observed that CAP does not damage
the tooth due to its low temperature51.Claiborne D et al., used a plasma plume on extracted human teeth. They
observed a statistically significant increase in the whitening of the teeth after exposure to CAP + 36% hydrogen
peroxide gel, compared with 36% hydrogen peroxide only, in the 10 and 20 min groups. The temperature in
both treatment groups remained under 80°F throughout the study, which is below the thermal threat for vital
tooth bleaching52. In a study by Jamali and Evans results revealed that prolonged plasma treatment (without
bleaching) removed some blue-stain, but the effect was small53. On the contrary, the combination of plasma
treatment and bleaching removed most of the blue-stains. It was concluded that vacuum plasma pre-treatment
and bleaching showed promise as a way of removing blue-stain.
Post and Core
Yavrich et al., studied the effects of plasma treatment on the shear bond strength between fiber
reinforced composite posts and resin composite for core build- up and concluded that plasma treatment appeared
to increase the tensile-shear bond strength between post and composite11.
MERITS
Enables the dentist to perform procedures without shots and pain11. Reduces or avoids the use of
routinely practiced painful and destructive drilling [12]. Noiseless, painless cavity preparations would be a huge
advance11.
SAFE TO USE
The flame is cool to touch without any feeling of warmth or touch12. It operates at room temperature
and does not cause bulk destruction of the tissue, being superior to lasers11.
LIMITATIONS
The technique is highly sensitive54. It does not work well in cases where amalgam restoration is present
in the oral cavity54. Cost of the equipment, marketing, maintenance and availability are also some of the issues
at present55. Plasma needle technology has a long way to go and shall prove its appli cability in the days to
come54.
V. CONCLUSION
Based on the above evidence, we can say that CAP has a bright future in dentistry due to its anti-
microbial properties and its cell death properties on cells. Studies of CAP showed promising results in tooth
bleaching, deactivation of biofilms in teeth, instrument sterilization, and in composite restoration. Nevertheless,
progress needs to be made concerning the ideal width and depth of the plume of plasma to enable the treatment
to reach lower in teeth. However, more studies need to be performed regarding the mechanism of action.
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... 5,[18][19][20] An alternative method uses nonthermal atmospheric plasma (NTAP) to decontaminate the surface. [21][22][23] NTAP leaves no residue, does not affect the surface morphology, 24,25 has minimal toxic effects, 26,27 and may be beneficial for mineral contents maintenance. 28 Two mechanisms of action are proposed for NTAP: the generation of reactive species, such as oxygen, nitrogen, or nitrogen oxide radicals that promote higher surface energy 29,30 ; and the etching effect caused by the process of oxidation. ...
... It is known that when plasma is applied to the surface, it may remove the organic residues, thus promoting a surface chemical restructure, and reduce the viability of bacteria. [21][22][23] Another NTAP characteristic is to decrease the amount of carbon and increase the amount of oxygen, 24,25,43 increasing the oxygenic polar groups, promoting a more hydrophilic surface. Since zirconia is a hydrophobic material and has no surface density of hydroxyl groups, the bonding to resin is not so strong. ...
Article
Objective To evaluate the effects of human saliva decontamination protocols on bond strength of resin cement to zirconia (Y‐PSZ), wettability, and microbial decontamination. Materials and methods Zirconia plates were sandblasted and divided into (a) not contaminated, (b) contaminated with human saliva and: (c) not cleaned, (d) cleaned with air‐water spray, (e) cleaned with 70% ethanol, (f) cleaned with Ivoclean, or (g) cleaned with nonthermal atmospheric plasma (NTAP). The wettability and microbial decontamination of the surfaces were determined after saliva contamination or cleaning. Monobond Plus (Ivoclar Vivadent) was applied after cleaning, followed by Variolink LC (Ivoclar Vivadent). The samples were stored 1 week before shear bond strength (SBS) testing, and data (SBS and wettability) were analyzed by one‐way analysis of variance and Tukey test (α = .05). Results Saliva contamination reduced SBS to zirconia compared to not contaminated. Both Ivoclean and NTAP produced higher SBS compared to not cleaned and were not significantly different from the not contaminated. Ivoclean produced the highest contact angle, and NTAP the lowest. With the exception of using just water‐spray, all cleaning protocols decontaminated the specimens. Conclusions Both Ivoclean and NTAP overcame the effects of saliva contamination, producing an SBS to zirconia comparable to the positive control. Clinical significance Dental ceramics should be cleaned prior to resin cementation to eliminate the effects of human saliva contamination, and Ivoclean and NTAP are considered suitable materials for this purpose.
... Aplikasi Plasma dalam bidang lingkungan yaitu dalam produksi ozon, Pembersihan gas polutan seperti gas nitrogen, belerang dioksida, pemurnian air dan pengolahan limbah industri [3]. Selain itu plasma dapat diaplikasikan dalam bidang kedokteran gigi untuk sterilisasi gigi dan pembersihan plak gigi [4]. ...
... These were in accordance with many researches (5,27,28) . Valverde et al (29) found a significant increase in the bond strength to zirconia surfaces when cold plasma was applied alone or in combination with alumina sandblasting. ...
... These plasmas can be produced in air or with various gases, such as oxygen, helium, argon, and nitrogen. Plasma can be produced by power sources with different frequencies such as low frequency, radio frequency, microwave frequency, high voltage AC or DC, to generate atmospheric and low-pressure glow discharge, corona, magnetron, microwave, gliding arc, plasma jet, and DBD discharge [84][85][86]. ...
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The formation of bacterial biofilm on implanted devices or damaged tissues leads to biomaterial-associated infections often resulting in life-threatening diseases and implant failure. It is a challenging process to eradicate biofilms as they are resistant to antimicrobial treatments. Conventional techniques, such as high heat and chemicals exposure, may not be suitable for biofilm removal in nosocomial settings. These techniques create surface degradation on the treated materials and lead to environmental pollution due to the use of toxic chemicals. A novel technique known as non-thermal plasma has a great potential to decontaminate or sterilize those nosocomial biofilms. This article aims to provide readers with an extensive review of non-thermal plasma and biofilms to facilitate further investigations. A brief introduction summarizes the problem caused by biofilms in hospital settings with current techniques used for biofilm inactivation followed by the literature review strategy. The remainder of the review discusses plasma and its generation, the role played by plasma reactive species, various factors affecting the antimicrobial efficacy of non-thermal plasma and summarizes many studies published in the field.
... In the recent years PSM found increased use in biomedical material science and engineering. The antibacterial properties of non-thermal plasma are already used to sterilize chirurgical instruments, disinfect carious dentin and stop dental bacteria [17][18][19][20][21][22][23][24][25][26][27][28][29]. The idea of using PSM to improve adhesive bonding of dental restorations has become a major point of interest as well. ...
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Objectives: The aim of the study was to evaluate the influence of contamination and different cleaning methods on the tensile bond strength with a phosphate monomer containing luting resin to zirconia ceramic. Methods: After the contamination with saliva or silicone disclosing agent, 228 polished and airborne-particle abraded zirconia discs were ultrasonically cleaned with 99% isopropanol. In a second step, the specimens were either treated with argon-oxygen plasma, air plasma, enzymatic cleaning agent or did not undergo an additional cleaning process. Uncontaminated zirconia specimens were used as the control group. X-ray photoelectron spectroscopy (XPS) was used for chemical analysis of the bonding surfaces of specimens. Plexiglas tubes filled with composite resin were bonded to zirconia specimens with a phosphate monomer containing luting resin. Tensile bond strength (TBS) was tested after 3 days or 150 days water storage with 37,500 thermal cycles. Results: XPS revealed a decrease of the carbon/oxygen ratio after plasma treatment and an increase after treatment with an enzymatic cleaning agent in all groups. All contaminated specimens showed high and durable TBS after cleaning with a combination of isopropanol and a non-thermal atmospheric plasma. After the cleaning with enzymatic cleaning agent the TBS was significantly reduced in all groups after 150 days thermal cycling. Significance: The combination of isopropanol and plasma cleaning was effective in removing salvia and disclosing agent contamination. Enzymatic clearing agent was not able to remove contamination effectively and had a negative impact on the TBS of non-contaminated specimens.
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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.
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Thermography is a technique of measurement of skin temperature distribution on the body over a given period of time. It is a noncontact, noninvasive method that utilizes the heat from an object to detect, display, and record thermal patterns and temperature across the surface of the object. Over the years, various devices have been used to measure the amount of heat dissipated by the body and most recently thermography has been emerged to detect the oral and maxillofacial pathologies. It is used to detect malignancies of the maxillofacial region such as vitality of teeth, TMJ disorders, chronic orofacial pain, assessing inferior alveolar nerve decit, and detection of herpes labialis. The present article highlights the history, basic principles, types and applications of thermography and its benecial role in detecting the maxillofacial pathologies in dentistry.
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A device capable of generating a relatively long cold plasma plume has recently been developed. The advantages of this device are: plasma controllability and stability, room temperature and atmospheric pressure operation, and low power consumption. These features are what is required from a plasma source to be used reliably in material processing applications, including the biomedical applications. In this communication we describe the device and we present evidence that it can be used successfully to inactivate Escherechia coli in a targeted fashion. More recent experiments have shown that this device inactivates other bacteria also, but these will be reported in the future.
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The hypothesis that a combination of plasma treatment and bleaching will be more effective than bleaching alone at removing stain from blue-stained lodgepole pine sapwood was tested. Blue-stained wood was pre-treated with glow-discharge plasma in vacuo for different times, immersed in a concentrated aqueous solution of sodium hypochlorite for 30 s and air-dried. The colour of dry samples before and after plasma treatment and also after bleaching was measured with a spectrophotometer. Prolonged plasma treatment (without bleaching) removed some blue-stain, but the effect was small. In contrast, the combination of plasma treatment and bleaching removed most of the blue-stain. It was concluded that vacuum plasma pre-treatment and bleaching shows promise as a way of removing blue-stain. Further research should be done to examine whether more practical (atmospheric) plasma pre-treatments can increase the effectiveness of hypochlorite bleach at removing blue-stain.
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