Plasma in dentistry

Biomaterials based on advanced oxidation processes in tooth whitening: fundamentals, progress, and models

The increasing desire for aesthetically pleasing teeth has resulted in the widespread use of tooth whitening treatments. Clinical tooth whitening products currently rely on hydrogen peroxide formulations to degrade dental pigments through oxidative processes. However, they usually cause side effects such as tooth sensitivity and gingival irritation due to the use of high concentrations of hydrogen peroxide or long-time contact. In recent years, various novel materials and reaction patterns have been developed to tackle the issues related to H2O2-based tooth whitening. These can be broadly classified as advanced oxidation processes (AOPs). AOPs generate free radicals that have potent oxidizing properties, which can thereby increase the oxidation power and/or reduce the exposure time and can probably minimize the side effects of tooth bleaching. While there have been several reviews on clinical tooth whitening and the application of novel nanomaterials, a review based on the concept of AOPs in tooth bleaching application has not yet been conducted. This review describes the common types and mechanisms of AOPs, summarizes the latest research progress of new tooth bleaching materials based on AOPs, and proposes a model for tooth bleaching and a rate control step at the molecular level. The paper also reviews the shortcomings and suggests future development directions.

Effect of argon cold plasma composition on orthodontic bonding-new insights into input parameters and protocols

PURPOSE

Cold atmospheric plasma can functionalize enamel without damaging the substrate morphology. It therefore has the potential to be a gentle alternative to conventional acid etching. To realize the full potential of cold atmospheric plasma in orthodontic bonding, the input parameters and protocols that are most beneficial to surface modification must first be identified. We aimed to clarify how the admixture of oxygen to cold atmospheric plasma and the rewetting of the enamel affect the conditioning properties for orthodontic bonding.

METHODS

First, we illustrated the morphological effects of different plasma compositions on the enamel surface by means of scanning electron microscopy. Then, we measured the shear bond strength resulting from different conditioning techniques on bovine enamel specimens: conventional acid etching; no conditioning; pure argon plasma; argon plasma plus 0.5% oxygen admixture; argon plasma plus 0.5% oxygen and rewetting after plasma application. Brackets were bonded using light cured adhesive; all specimens were subjected to thermocycling. The shear bond strength of each specimen was measured in a universal testing machine and compared using Welch one-way analysis of variance (ANOVA) and Games-Howell post hoc test.

RESULTS

Specimens conditioned with argon plasma plus 0.5% oxygen and rewetting showed a significantly higher shear bond strength than specimens conditioned with conventional acid etching. Conditioning with pure argon plasma and argon plasma plus 0.5% oxygen without rewetting yielded significantly lower shear bond strength.

CONCLUSION

Admixing 0.5% oxygen and rewetting the enamel after plasma application are crucial steps that could help make cold atmospheric plasma a gentle conditioning technique in orthodontic bonding.

Portable and affordable cold air plasma source with optimized bactericidal effect

The paper reports a low-cost handheld source of a cold air plasma intended for biomedical applications that can be made by anyone (detailed technical information and a step-by-step guide for creating the NTP source are provided). The plasma source employs a 1.4 W corona discharge in the needle-to-cone electrode configuration and is an extremely simple device, consisting basically of two electrodes and a cheap power supply. To achieve the best bactericidal effect, the plasma source has been optimized on Escherichia coli. The bactericidal ability of the plasma source was further tested on a wide range of microorganisms: Staphylococcus aureus as a representative of gram-positive bacteria, Pseudomonas aeruginosa as gram-negative bacteria, Candida albicans as yeasts, Trichophyton interdigitale as microfungi, and Deinococcus radiodurans as a representative of extremophilic bacteria resistant to many DNA-damaging agents, including ultraviolet and ionizing radiation. The testing showed that the plasma source inactivates all the microorganisms tested in several minutes (up to 105-107 CFU depending on a microorganism), proving its effectiveness against a wide spectrum of pathogens, in particular microfungi, yeasts, gram-positive and gram-negative bacteria. Studies of long-lived reactive species such as ozone, nitrogen oxides, hydrogen peroxide, nitrite, and nitrate revealed a strong correlation between ozone and the bactericidal effect, indicating that the bactericidal effect should generally be attributed to reactive oxygen species. This is the first comprehensive study of the bactericidal effect of a corona discharge in air and the formation of long-lived reactive species by the discharge, depending on both the interelectrode distance and the discharge current.

On the Use of Nanoparticles in Dental Implants

Results obtained in physics, chemistry and materials science on nanoparticles have drawn significant interest in the use of nanostructures on dental implants. The main focus concerns nanoscale surface modifications of titanium-based dental implants in order to increase the surface roughness and provide a better bone-implant interfacial area. Surface coatings via the sol-gel process ensure the deposition of a homogeneous layer of nanoparticles or mixtures of nanoparticles on the titanium substrate. Nanotubular structures created on the titanium surface by anodic oxidation yield an interesting nanotopography for drug release. Carbon-based nanomaterials hold great promise in the field of dentistry on account of their outstanding mechanical properties and their structural characteristics. Carbon nanomaterials that include carbon nanotubes, graphene and its derivatives (graphene oxide and graphene quantum dots) can be used as coatings of the implant surface. Their antibacterial properties as well as their ability to be functionalized with adequate chemical groups make them particularly useful for improving biocompatibility and promoting osseointegration. Nevertheless, an evaluation of their possible toxicity is required before being exploited in clinical trials.

Microbial Biofilms: Features of Formation and Potential for Use in Bioelectrochemical Devices

Microbial biofilms present one of the most widespread forms of life on Earth. The formation of microbial communities on various surfaces presents a major challenge in a variety of fields, including medicine, the food industry, shipping, etc. At the same time, this process can also be used for the benefit of humans-in bioremediation, wastewater treatment, and various biotechnological processes. The main direction of using electroactive microbial biofilms is their incorporation into the composition of biosensor and biofuel cells This review examines the fundamental knowledge acquired about the structure and formation of biofilms, the properties they have when used in bioelectrochemical devices, and the characteristics of the formation of these structures on different surfaces. Special attention is given to the potential of applying the latest advances in genetic engineering in order to improve the performance of microbial biofilm-based devices and to regulate the processes that take place within them. Finally, we highlight possible ways of dealing with the drawbacks of using biofilms in the creation of highly efficient biosensors and biofuel cells.

Dental silicate ceramics surface modification by nonthermal plasma: A systematic review

OBJECTIVES

Nonthermal atmospheric or low-pressure plasma (NTP) can improve the surface characteristics of dental materials without affecting their bulk properties. This study aimed to systematically review the available scientific evidence on the effectiveness of using NTP for the surface treatment of etchable, silica-based dental ceramics before cementation, and elucidate its potential to replace the hazardous and technically demanding protocol of hydrofluoric acid (HF) etching.

METHODS

A valid search query was developed with the help of PubMed's Medical Subject Headings (MeSH) vocabulary thesaurus and translated to three electronic databases: PubMed, Web of Science, and Scopus. The methodological quality of the studies was assessed according to an adapted version of the Methodological Index for Non-Randomized Studies (MINORS).

RESULTS

Thirteen in vitro study reports published between 2008 and 2023 were selected for the qualitative and quantitative data synthesis. The implemented methodologies were diverse, comprising 19 different plasma treatment protocols with various device settings. Argon, helium, oxygen, or atmospheric air plasma may significantly increase the wettability and roughness of silicate ceramics by plasma cleaning, etching, and activation, but the treatment generally results in inferior bond strength values after cementation compared to those achieved with HF etching. The technically demanding protocol of plasma-enhanced chemical vapor deposition was employed more commonly, in which the surface deposition of hexamethyl disiloxane with subsequent oxygen plasma activation proved the most promising, yielding bond strengths comparable to those of the positive control. Lack of power analysis, missing adequate control, absence of examiner blinding, and non-performance of specimen aging were common methodological frailties that contributed most to the increase in bias risk (mean MINORS score 15.3 ± 1.1).

SIGNIFICANCE

NTP can potentially improve the adhesive surface characteristics of dental silicate ceramics in laboratory conditions, but the conventional protocol of HF etching still performs better in terms of the resin-ceramic bond strength and longevity. More preclinical research is needed to determine the optimal NTP treatment settings and assess the aging of plasma-treated ceramic surfaces in atmospheric conditions.

Argon Plasma Treatment Effects on the Micro-Shear Bond Strength of Lithium Disilicate with Dental Resin Cements

The low bond strength of lithium disilicate (LD) ceramics to dental resin cements remains a critical issue for dental applications because it leads to frequent replacement and causes tooth tissue destruction and consumption. The objective of this study was to examine the effects of atmospheric non-thermal argon plasma (NTP) treatment on LD to improve its micro-shear bond strength (μSBS) with dental resin cements because LD mostly experiences shear stress for its commonly used dental applications as crowns or veneers. Argon plasma treatment was performed on hydrofluoric (HF) acid-etched LD surfaces, and then commercial resin cements were subsequently applied to the treated LD surfaces. The plasma treatment significantly reduced the water contact angle of the LD surface to less than 10° without changing the surface morphology. The μSBS test was performed with cement-bonded LD samples after 24 h and 30 days, as well as after 1000 cycles of thermal cycling. The test results show that, as compared with the untreated controls, 300 s of plasma treatment significantly improved the LD-resin cement bond strength by 59.1%. After 30 days of storage in DI water and 1000 cycles of thermal cycling, the plasma-treated LD samples show 84.2% and 44.8% higher bond strengths as compared to the control samples, respectively. The plasma treatment effect on LD surfaces diminished rapidly as the bond strength decreased to 25.5 MPa after aging in the air for 1 day prior to primer and cement application, suggesting that primers should be applied to the LD surfaces immediately after the plasma treatment. These results demonstrate that, when applied with caution, plasma treatment can activate LD surfaces and significantly improve the SBS of LD with dental resin cements in both short-term and long-term periods.

Modulation of the Tumor-Associated Immuno-Environment by Non-Invasive Physical Plasma

Over the past 15 years, investigating the efficacy of non-invasive physical plasma (NIPP) in cancer treatment as a safe oxidative stress inducer has become an active area of research. So far, most studies focused on the NIPP-induced apoptotic death of tumor cells. However, whether NIPP plays a role in the anti-tumor immune responses need to be deciphered in detail. In this review, we summarized the current knowledge of the potential effects of NIPP on immune cells, tumor-immune interactions, and the immunosuppressive tumor microenvironment. In general, relying on their inherent anti-oxidative defense systems, immune cells show a more resistant character than cancer cells in the NIPP-induced apoptosis, which is an important reason why NIPP is considered promising in cancer management. Moreover, NIPP treatment induces immunogenic cell death of cancer cells, leading to maturation of dendritic cells and activation of cytotoxic CD8⁺ T cells to further eliminate the cancer cells. Some studies also suggest that NIPP treatment may promote anti-tumor immune responses via other mechanisms such as inhibiting tumor angiogenesis and the desmoplasia of tumor stroma. Though more evidence is required, we expect a bright future for applying NIPP in clinical cancer management.

Plasma-Assisted Nanofabrication: The Potential and Challenges in Atomic Layer Deposition and Etching

The growing need for increasingly miniaturized devices has placed high importance and demands on nanofabrication technologies with high-quality, low temperatures, and low-cost techniques. In the past few years, the development and recent advances in atomic layer deposition (ALD) processes boosted interest in their use in advanced electronic and nano/microelectromechanical systems (NEMS/MEMS) device manufacturing. In this context, non-thermal plasma (NTP) technology has been highlighted because it allowed the ALD technique to expand its process window and the fabrication of several nanomaterials at reduced temperatures, allowing thermosensitive substrates to be covered with good formability and uniformity. In this review article, we comprehensively describe how the NTP changed the ALD universe and expanded it in device fabrication for different applications. We also present an overview of the efforts and developed strategies to gather the NTP and ALD technologies with the consecutive formation of plasma-assisted ALD (PA-ALD) technique, which has been successfully applied in nanofabrication and surface modification. The advantages and limitations currently faced by this technique are presented and discussed. We conclude this review by showing the atomic layer etching (ALE) technique, another development of NTP and ALD junction that has gained more and more attention by allowing significant advancements in plasma-assisted nanofabrication.

Simulation of the First Two Microseconds of an Ar CCP Cold Plasma Discharge by the PIC-MCC Method

Most simulations of capacitively coupled radiofrequency cold-plasma discharges (RF-CCP) are focused on the steady state, but the initial discharge time is important for understanding the ignition process and the behavior of pulsed discharges. In this work, the time evolution of an RF-CCP Ar discharge was simulated, considering a pressure of 66.6 Pa, a distance between the electrodes of 20 mm, and RF (13.56 MHz) bias amplitudes in range 100–400 V, and the discharge evolution was observed for the first 2 μs. A 1d3v (1 dimension for particle positions and 3 dimensions for particle velocities) electrostatic particle in cell with montecarlo collisions (PIC-MCC) model was used, with separated particle weights for electrons and ions that varied with the particle density. During the simulations, the time evolution of the electron density, mean electron energy, Debye length, Debye number, and plasma frequency were observed. The spatial distribution of electric potential and the electron energy distribution function were also monitored. A transition between two regimes was observed; the first was characterized by strong oscillation of the mean electron energy and an exponential increase of the mean plasma density with time, while in the second the mean electron energy was lower, and the plasma density increased linearly. The time required for the transition between the two regimes increased as the RF amplitude was raised from 100 to 250 V, then decreased with a further increase of the RF amplitude to 300 and 350 V.

Cold atmospheric plasma driven self-assembly in serum proteins: insights into the protein aggregation to biomaterials

The self-assembly of proteins is crucial in many biomedical applications. This work deals with understanding the role of cold atmospheric plasma (CAP) on the self-assembly of two different proteins present in the serum - BSA and hemoglobin and to elucidate the process associated with the direct application of physical plasma on or in the human (or animal) body, which has implications in therapeutics. The work has been corroborated by several spectroscopic studies such as fluorescence spectroscopy, circular dichroism spectroscopy, and SEM analysis. Through steady-state fluorescence spectroscopy and by following the tryptophan fluorescence, we observed that the emission intensity was quenched for the protein when treated with plasma radiation. Circular dichroism spectroscopy revealed that the structure of the protein was altered both in the case of BSA and hemoglobin. N-Acetyl tryptophanamide (NATA), which resembles the tryptophan in the protein, was treated with CAP and we observed the similar quenching of fluorescence as in the proteins, indicating that the protein underwent self-assembly. Time-resolved fluorescence spectroscopy with a decrease in the lifetime revealed that the protein self-assembly was promoted with CAP treatment, which was also substantiated by SEM micrographs. The ROS/RNS produced in the CAP has been correlated with the protein self-assembly. This work will help to design protein self-assembled systems, and in the future, may bring possibilities of creating novel biomaterials with the help of plasma radiation.

Applications of Plasma Produced with Electrical Discharges in Gases for Agriculture and Biomedicine

The use of thermal and non-thermal atmospheric pressure plasma to solve problems related to agriculture and biomedicine is the focus of this paper. Plasma in thermal equilibrium is used where heat is required. In agriculture, it is used to treat soil and land contaminated by the products of biomass, plastics, post-hospital and pharmaceutical waste combustion, and also by ecological phenomena that have recently been observed, such as droughts, floods and storms, leading to environmental pollution. In biomedical applications, thermal plasma is used in so-called indirect living tissue treatment. The sources of thermal plasma are arcs, plasma torches and microwave plasma reactors. In turn, atmospheric pressure cold (non-thermal) plasma is applied in agriculture and biomedicine where heat adversely affects technological processes. The thermodynamic imbalance of cold plasma makes it suitable for organic syntheses due its low power requirements and the possibility of conducting chemical reactions in gas at relatively low and close to ambient temperatures. It is also suitable in the treatment of living tissues and sterilisation of medical instruments made of materials that are non-resistant to high temperatures. Non-thermal and non-equilibrium discharges at atmospheric pressure that include dielectric barrier discharges (DBDs) and atmospheric pressure plasma jets (APPJs), as well as gliding arc (GAD), can be the source of cold plasma. This paper presents an overview of agriculture and soil protection problems and biomedical and health protection problems that can be solved with the aid of plasma produced with electrical discharges. In particular, agricultural processes related to water, sewage purification with ozone and with advanced oxidation processes, as well as those related to contaminated soil treatment and pest control, are presented. Among the biomedical applications of cold plasma, its antibacterial activity, wound healing, cancer treatment and dental problems are briefly discussed.

Comparison of the Biological Properties of Plasma-Treated Solution and Solution of Chemical Reagents

Presently, plasma-treated solutions (PTS) are widely introduced into medicine. Plasma-activated solutions contain various reactive forms of oxygen and nitrogen which provide the desired biological effects. Yet it remains unclear exactly which components of the treated solution are the most important and what the difference is between the plasma-treated solution and a chemically prepared solution composed of the same components. In this work, we show that the chemically prepared mixture of nitrites, nitrates, and hydrogen peroxide with concentrations similar to the plasma-treated solution exerts a fundamentally different effect on a cell culture. The chemically prepared solution has higher cyto- and genotoxicity and causes necrosis, while under the action of the plasma-treated solution, apoptotic processes develop in the cells slowly.

Cold plasma technology: An insight on its disinfection efficiency of various food systems

Cold plasma technology is considered as one of the novel potential non-thermal techniques for food disinfection. The acceptability of any food product depends upon its physicochemical properties and shelf life. Recent studies have confirmed that plasma can effectively reduce the pathogenic microbes in various food systems. Further, there are reports that cold plasma showed minimal or no effect on the physicochemical and sensory properties of the foods owing to its low-temperature operation. The present review explores the recent reports on cold plasma technology emphasizing its disinfection efficacy on different food categories. Various researchers have demonstrated that plasma successfully reduced the microorganisms on cereals, milk, meat, fish and spices. Therefore, based on the current research, it can be suggested that cold plasma is an effective disinfectant technology for the inactivation of pathogenic microorganisms, and its non-thermal and environmentally friendly nature is an added advantage over traditional processing technologies.

Laser Structured Dental Zirconium for Soft Tissue Cell Occupation—Importance of Wettability Modulation

Various approaches are being pursued to physico-chemically modify the zirconia neck region of dental implants to improve the integration into the surrounding soft tissue. In this study, polished zirconia discs were laser microstructured with periodic cavities and convex waves. These zirconia samples were additionally activated by argon plasma using the kINPen^®09. The surface topography was characterized by scanning electron microscopy and the surface wettability by water contact angle. The in vitro study with human gingival fibroblasts (HGF-1) was focused on cell spreading, morphology, and actin cytoskeleton organization within the first 24 h. The laser-induced microstructures were originally hydrophobic (e.g., 60 µm cavities 138.4°), but after argon plasma activation, the surfaces switched to the hydrophilic state (60 µm cavities 13.7°). HGF-1 cells adhered flatly on the polished zirconia. Spreading is hampered on cavity structures, and cells avoid the holes. However, cells on laser-induced waves spread well. Interestingly, argon plasma activation for only 1 min promoted adhesion and spreading of HGF-1 cells even after 2 h cultivation. The cells crawl and grow into the depth of the cavities. Thus, a combination of both laser microstructuring and argon plasma activation of zirconia seems to be optimal for a strong gingival cell attachment.

Aurora Borealis in dentistry: The applications of cold plasma in biomedicine

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.

•

Non-thermal plasma (NTP) has regarded as an important tool for biomedical application especially dental application.

•

The surface application of NTP can be used for disinfecting microbial infection in endodontic issues.

•

NTP can be used to eradicate the microorganism biofilm responsible for dental caries.

•

NTP can also be utilized in would healing, implant modifications and adhesive restoration.

•

NTP is potential candidate for clinical application in dentistry based on the experimental proofs.

Antibacterial efficacy of non-thermal atmospheric plasma against Streptococcus mutans biofilm grown on the surfaces of restorative resin composites

The aim of this study was to evaluate the antimicrobial efficacy of non-thermal atmospheric plasma (NTAP) against Streptococcus mutans biofilms. Resin discs were fabricated, wet-polished, UV sterilized, and immersed in water for monomer extraction (37 °C, 24 h). Biofilms of bioluminescent S. mutans strain JM10 was grown on resin discs in anaerobic conditions for (37 °C, 24 h). Discs were divided into seven groups: control (CON), 2% chlorhexidine (CHX), only argon gas 150 s (ARG) and four NTAP treatments (30 s, 90 s, 120 s, 150 s). NTAP was applied using a plasma jet device. After treatment, biofilms were analyzed through the counting of viable colonies (CFU), bioluminescence assay (BL), scanning electron microscopy (SEM), and polymerase chain reaction (PCR). All NTAP-treated biofilm yielded a significant CFU reduction when compared to ARG and CON. BL values showed that NTAP treatment for 90 s, 120 s or 150 s resulted in statistically significantly lower metabolic activity when compared to the other groups. CHX displayed the lowest means of CFU and BL. SEM showed significant morphological changes in NTAP-treated biofilm. PCR indicated damage to the DNA structure after NTAP treatment. NTAP treatment was effective in lowering the viability and metabolism of S. mutans in a time-dependent manner, suggesting its use as an intraoral surface-decontamination strategy.

Nitrogen doped titanium dioxide as an aesthetic antimicrobial filler in dental polymers

OBJECTIVE

To develop an aesthetic resin composite using a nitrogen-doped titanium dioxide (NTiO₂) filler that possesses antimicrobial properties against cariogenic bacteria.

METHODS

N-TiO₂ powder was manufactured by calcining commercial TiO₂ with urea. Free radical release from the N-TiO₂ powder under visible light irradiation was analysed using UV-Vis spectrophotometry. The N-TiO₂ powder was incorporated into a dental resin and the photocatalytic activity assessed using a dye under both visible light and dark conditions. Using XTT assay to measure the cellular metabolic activity, the antibacterial properties of the N-TiO₂ /resin composite discs were tested using Streptococcus mutans.

RESULTS

Doping nitrogen of TiO₂ resulted in a band gap shift towards the visible light spectrum, which enabled the powder to release reactive oxygen species when exposed to visible light. When incorporated into a dental resin, the N-TiO₂/resin composite still demonstrated sustained release of reactive oxygen species, maintaining its photocatalytic activity and showing an antibacterial effect towards Streptococcus mutans under visible light conditions.

SIGNIFICANCE

N-TiO₂ filled resin composite shows great promise as a potential aesthetic resin based adhesive for orthodontic bonding.

Human osteoblast and fibroblast response to oral implant biomaterials functionalized with non-thermal oxygen plasma

Plasma-treatment of oral implant biomaterials prior to clinical insertion is envisaged as a potential surface modification method for enhanced implant healing. To investigate a putative effect of plasma-functionalized implant biomaterials on oral tissue cells, this investigation examined the response of alveolar bone osteoblasts and gingival fibroblasts to clinically established zirconia- and titanium-based implant surfaces for bone and soft tissue integration. The biomaterials were either functionalized with oxygen-plasma in a plasma-cleaner or left untreated as controls, and were characterized in terms of topography and wettability. For the biological evaluation, the cell adhesion, morphogenesis, metabolic activity and proliferation were examined, since these parameters are closely interconnected during cell-biomaterial interaction. The results revealed that plasma-functionalization increased implant surface wettability. The magnitude of this effect thereby depended on surface topography parameters and initial wettability of the biomaterials. Concerning the cell response, plasma-functionalization of smooth surfaces affected initial fibroblast morphogenesis, whereas osteoblast morphology on rough surfaces was mainly influenced by topography. The plasma- and topography-induced differential cell morphologies were however not strong enough to trigger a change in proliferation behaviour. Hence, the results indicate that oxygen plasma-functionalization represents a possible cytocompatible implant surface modification method which can be applied for tailoring implant surface wettability.

Surface Characterisation of PEEK and Dentin, Treated with Atmospheric Non-Thermal PDD Plasma, Applicable for Dental Chair-Side Procedures

This study investigates the suitability of Piezoelectric Direct Discharge Plasma as a tool for wetting behaviour modification of PEEK and dentin, and compares the results of this method with low-pressure plasma treatment and phosphoric acid etching. Static contact angle measurements were made, roughness was assessed using tactile measurement, and AFM and SEM images were taken. An optimum operating distance of ≤15 mm was determined for the plasma based on the water contact angle. Furthermore, it was demonstrated that despite only a fraction of the power, the PDD plasma also produces hydrophilic and nanostructured PEEK surfaces with a 38° water contact angle in the same plasma time. In contrast, the gold standard of dental surface modification of dentin—phosphoric acid etching—showed no measurable contact angle due to the exposed dentin tubules. Treatment with PDD plasma reduces the water contact angle of dentin from 65° to 43° and is not negative affected by water. Wet, PDD plasma-treated dentin samples show a water contact angle of only 26.5°. The dentin tubules exposed by chemical etching led to a significantly increased roughness. No comparable effect could be demonstrated for plasma treatment on dentin, but based on the contact angle measurements, a chemically strongly activated surface with strongly polar interaction behaviour can be assumed. The additional use of the PDD plasma technique to improve wetting could therefore have a positive effect on the adhesive bond between human dentin and polymeric dental restorative materials or, depending on the adhesive system, replace the etching process altogether.

Evaluation of the bond strengths of restorative materials to primary tooth dentin treated with different pulpotomy techniques

The aim of this study was to investigate the changes of different pulpotomy techniques on the primary tooth dentin and to evaluate the effects of these pulpotomy methods on the shear bond strength of restorative materials to primary tooth dentin. Two hundred and forty dentin specimens were distributed randomly to the study groups as; control, ferric sulphate, Biodentine® , Nd:YAG laser, photobiomodulation, and atmospheric pressure cold plasma (APCP). After the application of pulpotomy methods, samples were again randomly divided to two restorative materials (glass hybrid and composite resin) (n = 20) and shear bond strength (SBS) test was performed. Then, 12 new dentin specimens were prepared for all groups for surface analysis. Surface examination (n = 12) and fracture analyses (n = 240) were carried out with scanning electron microscope (SEM). Statistical significance range was accepted as α <.05 for all data. A statistically significant difference was obtained among all study groups for glass hybrid material as well as composite material (p <.05). While the highest mean SBS value was obtained with Nd:YAG laser (7.58 ± 0.60 MPa), the lowest value was observed with Biodentine® (6.70 ± 0.91 MPa; p = .001) for glass hybrid material. For composite material, the highest mean SBS value was calculated for Nd:YAG laser (13.79 ± 1.24 MPa), while the lowest value was obtained with ferric sulphate (10.17 ± 1.45 MPa; p = .001). Fracture modes were mainly adhesive and mixed type according to SEM analysis. Moreover, morphological changes were observed with SEM on the dentin surfaces of ferric sulphate, Biodentine® and Nd:YAG laser. Within the limitations of this study, Nd:YAG laser increased the shear bond strength values in groups of composite resin. RESEARCH HIGHLIGHTS: In this article, we report the results of the shear bonding strength test of two restorative materials (glass-hybrid vs. composite resin) to primary tooth dentin following the application of five different pulpotomy techniques (ferric sulfate, Biodentine® , Nd:YAG laser, photobiomodulation, and atmospheric pressure cold plasma) were reported. This article will contribute to the literature that there are considerably limited researches concerning the bond strength of glass hybrid to primary dentin and also atmospheric pressure cold plasma in pulpotomies. The SEM examination was performed in two stages in this study; the morphological changes in both treated dentin surfaces and the surfaces of the samples subjected to the shear bond strength test.

Cold atmospheric plasma as an interface biotechnology for enhancing surgical implants

Cold atmospheric plasma (CAP) has been intensively researched for direct treatment of living cells and tissues. Significant attention is now being given to its indirect applications in plasma medicine. Surgical implant is an exemplary conveyor to deliver the therapeutic effects of plasma to patients. There is a constant drive to enhance the clinical performance of surgical implants, targeting at the implant-tissue interface. As a versatile and potent tool, CAP is capable of ameliorating surgical implants using various strategies of interface biotechnology, such as surface modification, coating deposition, and drug delivery. Understanding the chemical, physical, mechanical, electrical, and pharmacological processes occurring at the implant-tissue interface is crucial to effective application of CAP as an interface biotechnology. This preclinical review focuses on the recent advances in CAP-assisted implant-based therapy for major surgical specialties. The ultimate goal here is to elicit unique opportunities and challenges for translating implant science to plasma medicine.

Influence of chairside surface treatments on the shear bond strength of PEKK polymer to veneering resin materials: An in vitro study

STATEMENT OF PROBLEM

High-performance thermoplastics have been adopted as an alternative restorative material to metal or ceramics. However, a straightforward surface modification process to provide a durable bond strength between the polymer and the veneering material is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the shear bond strength (SBS) of different veneering resin materials to polyetherketoneketone (PEKK) after different surface treatments.

MATERIAL AND METHODS

Rectangular (7×7×2 mm) PEKK specimens (N=120) were randomly allocated to the following 6 groups (n=20): untreated (Cnt); nonthermal plasma (NTP) treated; tribochemical silica airborne-particle abrasion with 30-μm silica-modified Al₂O₃ (Tbc); abraded with a coarse-grit diamond rotary instrument (Ab); tribochemical silica airborne-particle abrasion + plasma treated (Tbc_NTP); abraded + plasma treated (Ab_NTP). After a bonding agent (PEKK Bond) was applied to the specimens, each group was divided into 2 subgroups according to the applied veneering resin materials: polymethylmethacrylate (PMMA) and nanohybrid composite resin (NHC, n=10). The specimens were stored in water for 24 hours at 37 °C and subjected to the SBS test by using a universal testing machine, and failure modes were evaluated using a stereomicroscope. Two-way analysis of variance (ANOVA) was performed followed by the Tukey honestly significant difference (HSD) test to statistically analyze the data (α=.05).

RESULTS

The 2-way ANOVA showed that surface treatment methods, veneering material, and their interactions were significantly different on the SBS values (P<.001). The highest SBS values were determined for the Tbc and Tbc_NTP treatment groups not only for PMMA (10.71 to 11.63 MPa) but also for NHC (19.80 to 20.60 MPa) veneering resin materials (P<.05).

CONCLUSIONS

The bonding capacity of PEKK to the PMMA and NHC veneering resin materials can be significantly improved by using tribochemical silica airborne-particle abrasion alone or with nonthermal plasma surface treatment techniques. Furthermore, using NHC veneering resin material is recommended over PMMA.

Oral Biofilm: Development Mechanism, Multidrug Resistance, and Their Effective Management with Novel Techniques

Biofilms are formed by the congregation of one or more types of microorganisms that can grow on a firm surface. Dental plaque is one of the most commonly forming biofilms in the oral cavity and appears as a slimy layer on the surface of the teeth. In general, the formation is slow, but biofilms are very adaptive to the changing environment, and a mature biofilm can cause many health-related problems in humans. These biofilms remain unaffected by antibiotics as they do not allow the penetration of antibiotics. Moreover, the increased level of virulence and antibiotic resistance of microorganisms in the oral biofilm or dental plaque has made its clinical management a serious challenge worldwide. Chlorhexidine-like antimicrobial drugs have been partially effective in removing such organisms; however, the precise and continuous elimination of these microorganisms without disturbing the normal microbial flora of the oral cavity is still a challenge. This review paper focuses on the process of oral biofilm formation, related complications, development of drug-resistant bacteria in these biofilms, and their effective management by the use of different novel techniques, available from various published research and review articles.

The antimicrobial and tissue healing efficacy of the atmospheric pressure cold plasma on grade III infected pressure ulcer: randomized controlled in vivo experiment

AIM

To evaluate the antimicrobial efficacy and wound healing effect of atmospheric pressure cold plasma (APCP) on an infected pressure ulcer (IPUs) model that was created on rats.

METHODS

A total of 18 rats was divided into APCP, silver sulfadiazine (AgS) and control groups to have six rats in each group. A third-grade pressure ulcer model was developed on the back of each of the rats, and pressure ulcers were infected by inoculation of multidrug resistance (MDR) Pseudomonas aeruginosa. A portable dielectric barrier discharge device was used to generate cold air plasma. APCP, AgS and saline treatments were carried out once a day for 14 days. The effectiveness of the treatment was evaluated on days 5, 10 and 15. Surface area, depth, pressure ulcer healing scale (PUSH) and microbiological examination were used for evaluation.

RESULTS

The results of this study showed that APCP was superior over AgS application and irrigation with saline by means of the reduction in surface area and depth of ulcers. Furthermore, PUSH score in plasma group was lower than other groups and histopathological examination showed a higher epithelization in APCP group. The average reductions of MDR P. aeruginosa for APCP, AgS and control groups were determined as 5·64 ± 1·87, 1·91 ± 0·90 and 1·22 ± 0·88 log10 CFU per gram tissue, respectively.

CONCLUSION

Atmospheric pressure cold plasma healed IPUs better than AgS.

SIGNIFICANCE AND IMPACT OF THE STUDY

Portable cold plasma devices could be a potential novel treatment modality for the patients who have IPUs.

Effects of Surface Modification on Adsorption Behavior of Cell and Protein on Titanium Surface by Using Quartz Crystal Microbalance System

Primary stability and osseointegration are major challenges in dental implant treatments, where the material surface properties and wettability are critical in the early formation of hard tissue around the implant. In this study, a quartz crystal microbalance (QCM) was used to measure the nanogram level amount of protein and bone marrow cells adhered to the surfaces of titanium (Ti) surface in real time. The effects of ultraviolet (UV) and atmospheric-pressure plasma treatment to impart surface hydrophilicity to the implant surface were evaluated. The surface treatment methods resulted in a marked decrease in the surface carbon (C) content and increase in the oxygen (O) content, along with super hydrophilicity. The results of QCM measurements showed that adhesion of both adhesive proteins and bone marrow cells was enhanced after surface treatment. Although both methods produced implants with good osseointegration behavior and less reactive oxidative species, the samples treated with atmospheric pressure plasma showed the best overall performance and are recommended for clinical use. It was verified that QCM is an effective method for analyzing the initial adhesion process on dental implants.

Influence of Low-Pressure Plasma on the Surface Properties of CAD-CAM Leucite-Reinforced Feldspar and Resin Matrix Ceramics

The introduction of new ceramic materials for dental restorations is currently a reality; however, little information is available on their surface treatment for the bonding process. Furthermore, surface treatment with plasma on ceramic materials has been recently introduced, although not many studies are available. The aim of this study was to evaluate the surface properties of a leucite-reinforced feldspar ceramic (LIC) and resin matrix ceramic (RMC) after low-pressure plasma treatment. From each material, 48 discs were prepared and subject to surface treatment. The LIC group was treated by hydrofluoric acid (HF) (LIC-HF), plasma with oxygen (LIC-O2), and plasma with argon (LIC-Ar). The RMC group was treated by sandblasting with alumina (RMC-SB), plasma with oxygen (RMC-O2), and plasma with argon (RMC-Ar). The groups whose surfaces were not subjected to treatment were considered as the control group. Surface wettability and roughness was analyzed. The results showed significant differences among the treatments for both ceramics regarding wettability and roughness. Plasma treatments increased the wettability and had a very low effect on the roughness. Plasma treatments achieved similar values for both surface properties in each ceramic group with no differences between both treatments. Plasma treatment seems to be a promising alternative for ceramic surface treatments since it increased the surface energy of the ceramics analyzed and hardly affects the roughness. Further studies are necessary to evaluate the effect of plasma treatment on the bond strength of ceramics.

Thin Film Deposition by Atmospheric Pressure Dielectric Barrier Discharges Containing Eugenol: Discharge and Coating Characterizations

Eugenol (4-Allyl-2-methoxyphenol) is the main constituent of clove oil. In addition to being widely used as a condiment, it has been recognized as a powerful bactericide. Owing to that, Eugenol has been used in several applications including odontology and as a conservative for food products. Aiming at the development of natural bactericide coatings, in this work, using an atmospheric pressure plasma in a dielectric barrier discharge (DBD) reactor Eugenol was deposited on stainless steel substrate, with argon as a carrier gas. The discharge power supply was a transformer at 14.4 kV peak-to-peak voltage and 60 Hz frequency. Operating with a gas flow rate at 4 L/min, the active power was around 1.2 W. The maximum plasma electron temperature of the plasma with monomers was about 1.5 eV, estimated by visible emission spectroscopy using a local thermodynamic equilibrium approach. The study also comprehended the analysis of the film structure, aging, and thermal stability using infrared reflectance spectroscopy, and its thicknesses and roughness by profilometry. The thickness of the films was in the range of 1000 to 2400 nm with a roughness of up to 800 nm with good adhesion on the substrate. The FTIR result shows a stable coating with a chemical structure similar to that of the monomer. Aging analysis showed that the film does not degrade, even after exposing the film for 120 days in ambient air and for 1.0 h under a high thermal UV-lamp.

Effects of cold atmospheric pressure plasma jet on human apical papilla cell proliferation, mineralization, and attachment

OBJECTIVES

To investigate the direct effects of cold atmospheric pressure plasma jet on cell proliferation and mineralization on human apical papilla cells and its indirect effect on cell attachment on plasma-treated dentin.

MATERIALS AND METHODS

Plasma was directly applied to cell culture for various durations. Cell proliferation was evaluated using AlamarBlue® assay. Mineralization was assessed using Alizarin Red S staining after 14 and 21 days. The cell attachment to plasma-treated dentin surface was evaluated using an ex vivo immature tooth model, and the protocols varied based on root canal irrigants (NSS or 17% EDTA), the durations of plasma application (0, 30, or 60 s), and the different positions of the plasma needle (coronal or middle). The attached cells were visualized using the immunofluorescence staining and the positive-staining cells were counted.

RESULTS

There was no difference in the cell proliferation between the untreated and plasma-treated cells. However, the plasma-treated cells tended to have lower levels of calcium deposition, especially after the 60-s plasma application (p < 0.05). Finally, significantly greater numbers of attached cells were shown when NSS was combined with plasma treatment when compared to the untreated cells (p < 0.05), whereas no difference was observed when EDTA was used as the irrigant.

CONCLUSIONS

Plasma might disturb the mineralization of the cells. Interestingly, the dentin conditioning process using a plasma jet with NSS irrigation may enhance cell attachment.

CLINICAL RELEVANCE

Cold atmospheric pressure plasma jet may be an alternative treatment in regenerative endodontic procedures in order to improve cell attachment in the root canal system.

Surface Modified Techniques and Emerging Functional Coating of Dental Implants

Dental implants are widely used in the field of oral restoration, but there are still problems leading to implant failures in clinical application, such as failed osseointegration, marginal bone resorption, and peri-implantitis, which restrict the success rate of dental implants and patient satisfaction. Poor osseointegration and bacterial infection are the most essential reasons resulting in implant failure. To improve the clinical outcomes of implants, many scholars devoted to modifying the surface of implants, especially to preparing different physical and chemical modifications to improve the osseointegration between alveolar bone and implant surface. Besides, the bioactive-coatings to promote the adhesion and colonization of ossteointegration-related proteins and cells also aim to improve the osseointegration. Meanwhile, improving the anti-bacterial performance of the implant surface can obstruct the adhesion and activity of bacteria, avoiding the occurrence of inflammation related to implants. Therefore, this review comprehensively investigates and summarizes the modifying or coating methods of implant surfaces, and analyzes the ossteointegration ability and anti-bacterial characteristics of emerging functional coatings in published references.

Effects of carbon and nitrogen plasma immersion ion implantation on bioactivity of zirconia

Zirconia is considered the most promising alternative material to titanium implants. However, zirconia is a biologically inert material and its surface modification is essential to obtain efficient osseointegration. Plasma immersion ion implantation (PIII) is a controllable and flexible approach that constructs functional groups on the surface of biomaterials and enhances osteogenic ability of host osteoclast cells. Zirconia disks were randomly divided into 4 groups (n = 50/group): (1) Blank, (2) C60N0, (3) C60N6, and (4) C60N18. Carbon and nitrogen plasma immersion ion implantation on zirconia (C and N₂-PIII) surface modification was completed with the corresponding parameters. When zirconia was modified by carbon and nitrogen plasma implantation, a new chemical structure was formed on the material surface while the surface roughness of the material remained unaltered. The nitrogen-containing functional groups with high potential were introduced but the bulk crystal structure of zirconia was not changed, indicating that the stability of zirconia was not affected. In vitro data showed that zirconia with high surface potential promoted adhesion, proliferation, and osteogenic differentiation of BMSCs. C60N6 was found to be superior to the other groups. Our results demonstrate that a zirconia surface modified by C and N₂-PIII can introduce desirable nitrogen functional groups and create a suitable extracellular environment to promote BMSCs biological activity. Taken together, these results suggest that C and N₂-PIII modified zirconia is a promising material for use in the field of medical implantation.

Zirconia is considered the most promising alternative material to titanium implants.

The impact of non-thermal plasma on the adhesion of polyetherketoneketone (PEKK) to a veneering composite system

The PEKK material can be used in prosthodontics for framework manufacturing and is commonly laminated with veneering composites to achieve a better esthetics. Various surface treatment methods including sandblasting, etching, laser and cold plasma treatments were reported to enhance the adhesive properties of dental polymers. Both tensile and shear bond test were employed to quantify the bond strength between PEKK and veneering composites. The present in vitro study aims to evaluate the influence of acetylene, argon, air, nitrogen and oxygen plasma on the shear bond strength between PEKK and one veneering composite. Firstly, to determine which bond test type should be applied, n = 40 PEKK specimens were treated with argon plasma. Both shear and tensile bond tests were performed and compared to the control group (n = 40). In shear bond testing, values were 8.14 ± 1.70 MPa for Argon plasma while 5.83 ± 1.42 MPa for control group. In tensile bond testing, Argon plasma 1.50 ± 0.51 MPa while control group 0.58 ± 0.50 MPa. Afterwards n = 160 PEKK specimens were treated with rocatec sandblasting (n = 20), adhesive (n = 20), acetylene (n = 20), argon (n = 20), air (n = 20), nitrogen (n = 20), oxygen (n = 20) plasma types and compared to the untreated control group (n = 20) using shear bond strength test (SBS). Additionally surface roughness and scanning electron microscopy analyses were performed. The following SBS values were revealed: 10.22 ± 1.06 MPa for rocatec; 9.89 ± 3.08 MPa for acetylene, 9.16 ± 1.48 MPa for adhesive, 7.54 ± 1.52 MPa for argon, 7.09 ± 1.99 MPa for air, 7.03 ± 1.48 MPa for nitrogen, 5.69 ± 1.59 MPa for oxygen plasma types and 4.71 ± 1.54 MPa for the control group. All groups, except control group, showed SBS over 5 MPa, which means that they are suitable for the clinical application, according to ISO 10477. Acetylene showed the highest SBS among all plasma types (p < 0.0001), which was on a level of rocatec sandblasting group. Rocatec and acetylene groups demonstrated Ra values significantly different to the reference group (p < 0.0001). Plasma treatment especially with acetylene gas can be an effective more convenient surface treatment method for strengthening the bond strength between PEKK and veneering composites than traditional sandblasting/adhesive treatment.

Utility of Reactive Species Generation in Plasma Medicine for Neuronal Development

Reactive oxygen species (ROS) are critical signaling molecules for neuronal physiology that stimulate growth and development and play vital roles in several pathways when in a balanced state, but they cause neurodegeneration when unbalanced. As ROS levels above a certain threshold cause the activation of the autophagy system, moderate levels of ROS can be used as treatment strategies. Currently, such treatments are used together with low-level laser or photodynamic therapies, photo-bio modulation, or infrared treatments, in different chronic diseases but not in the treatment of neurodegeneration. Recently, non-thermal plasma has been successfully used in biomedical applications and treatments, and beneficial effects such as differentiation, cell growth, and proliferation, stimulation of ROS based pathways have been observed. Besides the activation of a wide range of biological signaling pathways by generating ROS, plasma application can be an effective treatment in neuronal regeneration, as well as in neuronal diseases. In this review, we summarize the generation and role of ROS in neurons and provide critical insights into their potential benefits on neurons. We also discuss the underlying mechanisms of ROS on neuronal development. Regarding clinical applications, we focus on ROS-based neuronal growth and regeneration strategies and in the usage of non-thermal plasma in neuronal and CNS injury treatments.

Glow Discharge Plasma Treatment on Zirconia Surface to Enhance Osteoblastic-Like Cell Differentiation and Antimicrobial Effects

Peri-implantitis is the pathological condition of connective tissue inflammation and the progressive loss of supporting bone around dental implants. One of the primary causes of peri mucositis evolving into peri-implantitis is bacterial infection, including infection from Porphyromonas gingivalis. Enhancing the surface smoothness of implants helps to prevent P. gingivalis adhesion to the implant’s surface. Interaction analyses between bacteria and the surface roughness of zirconia (Zr) discs subjected to a glow discharge plasma (GDP) treatment compared with non-plasma-treated autoclaved control Zr discs were done. Examinations of the material prosperities revealed that the GDP-treated Zr group had a smoother surface for a better wettability. The GDP-treated Zr discs improved the proliferation of the osteoblast-like cells MG-63, and the osteoblastic differentiation was assessed through alkaline phosphatase detection and marker gene bone sialoprotein (Bsp) and osteocalcin (OC) induction. Scanning electron microscopy demonstrated a relatively low P. gingivalis adhesion on GDP-treated Zr disks, as well as lower colonization of P. gingivalis compared with the control. Our findings confirmed that the GDP treatment of Zr discs resulted in a significant reduction of P. gingivalis adhesion and growth, demonstrating a positive correlation between surface roughness and bacteria adhesion. Therefore, the GDP treatment of Zr dental implants can provide a method for reducing the risk of peri-implantitis.

Comparison of Antibacterial Effects of Photodynamic Therapy and an Irrigation Activation System on Root Canals Infected With Enterococcus faecalis: An In Vitro Study

Introduction: Enterococcus faecalis is a resistant bacterium which is the most abundant species in infected root canals. Photodynamic therapy (PDT) is a method for killing the bacteria with active Oxygen radicals generated in a photosensitizer when exposed to centralized light. Furthermore, as a new method of canal disinfection, a variety of irrigation activation systems have been introduced, one of which is GentleFile (GF) with rotary movements and spiral effects for antibacterial action. This study aimed to compare the effectiveness of the two mentioned methods when used with and without Sodium Hypochlorite in eliminating E. faecalis from infected root canals. Methods: Fifty-eight uniradicular teeth were randomly divided into 4 experimental groups of 14. Two specimens were selected for later scanning electron microscopy in order to screen the procedure steps. In each experimental group, 10 samples were selected to be treated with GF or PDT; 3 of them were selected as positive controls and the other one sample was chosen as a negative control. Experimental groups were as follows: (1) Irrigation activation system, (2) Irrigation activation system + sodium hypochlorite, (3) PDT, and (4) PDT+ sodium hypochlorite. The specimens were then cultured for a bacterial colony count. Results: The decrease in the bacterial count after the treatment with the irrigation activation system was 99.8% (P =0.011) and when the system was used with sodium hypochlorite, it was 100% (P =0.001). The antibacterial effect of PDT was 90.08% (P =0.011) and it was 99.7% when PDT was combined with sodium hypochlorite (P =0.011). Conclusion: All four methods can be administered as complementary methods in root canal disinfection. According to the results of disinfection in the experimental groups of current study it is concluded that integration of new technologies such as activation irrigation system or PDT in Combination with NaOCl ameliorates disinfection of root canal and can provide several advantages in the endodontic outcome.

Bioactive Surfaces vs. Conventional Surfaces in Titanium Dental Implants: A Comparative Systematic Review

Animal studies and the scarce clinical trials available that have been conducted suggest that bioactive surfaces on dental implants could improve the osseointegration of such implants. The purpose of this systematic review was to compare the effectiveness of osseointegration of titanium (Ti) dental implants using bioactive surfaces with that of Ti implants using conventional surfaces such as sandblasted large-grit acid-etched (SLA) or similar surfaces. Applying the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement, the MEDLINE, PubMed Central and Web of Science databases were searched for scientific articles in April 2020. The keywords used were “dental implants”, “bioactive surfaces”, “biofunctionalized surfaces”, and “osseointegration”, according to the question: “Do bioactive dental implant surfaces have greater osseointegration capacity compared with conventional implant surfaces?” Risk of bias was assessed using the Cochrane Collaboration tool. 128 studies were identified, of which only 30 met the inclusion criteria: 3 clinical trials and 27 animal studies. The average STROBE (STrengthening the Reporting of OBservational studies in Epidemiology) and ARRIVE (Animal Research: Reporting of In Vivo Experiments) scores were 15.13 ± 2.08 and 17.7±1.4, respectively. Implant stability quotient (ISQ) was reported in 3 studies; removal torque test (RTT)—in 1 study; intraoral periapical X-ray and microcomputed tomography radiological evaluation (RE)—in 4 studies; shear force (SF)—in 1 study; bone-to-implant contact (BIC)—in 12 studies; and BIC and bone area (BA) jointly—in 5 studies. All animal studies reported better bone-to-implant contact surface for bioactive surfaces as compared to control implants with a statistical significance of p < 0.05. Regarding the bioactive surfaces investigated, the best results were yielded by the one where mechanical and chemical treatment methods of the Ti surfaces were combined. Hydroxyapatite (HA) and calcium–phosphate (Ca–Ph) were the most frequently used bioactive surfaces. According to the results of this systematic review, certain bioactive surfaces have a positive effect on osseointegration, although certain coating biomolecules seem to influence early peri-implant bone formation. Further and more in-depth research in this field is required to reduce the time needed for osseointegration of dental implants.

Plasma Medicine: A Field of Applied Redox Biology

Plasma medicine comprises the application of physical plasma directly on or in the human body for therapeutic purposes. Three most important basic plasma effects are relevant for medical applications: i) inactivation of a broad spectrum of microorganisms, including multidrug-resistant pathogens, ii) stimulation of cell proliferation and angiogenesis with lower plasma treatment intensity, and iii) inactivation of cells by initialization of cell death with higher plasma treatment intensity, above all in cancer cells. Based on own published results as well as on monitoring of relevant literature the aim of this topical review is to summarize the state of the art in plasma medicine and connect it to redox biology. One of the most important results of basic research in plasma medicine is the insight that biological plasma effects are mainly mediated via reactive oxygen and nitrogen species influencing cellular redox-regulated processes. Plasma medicine can be considered a field of applied redox biology.

Platelet Adhesion on Commercially Pure Titanium Plates in Vitro II. Immunofluorescence Visualization of PDGF-B, TGFβ1, and PPARγ Released from Activated Adherent Platelets

Recent progress in the industrial development of dental implants has improved their surface bio-affinity, while clinical implantologists attempt to improve it through coating with various compounds, including platelet-rich plasma (PRP) in clinical settings. However, it is poorly understood how PRP acts on titanium surfaces. To validate this surface modification method and demonstrate how platelet-derived soluble biomolecules released from the activated adherent platelets act on plain, commercially pure-titanium (cp-Ti) plates, we evaluated the distribution of biomolecules by immunofluorescence. PPARγ, PDGF-B, and TGFβ1 were similarly released at immunofluorescence levels from activated adherent platelets, retained in the surrounding extra-platelet spaces for a while, and did not immediately diffuse away to distant spaces. Exogenously added CaCl₂ augmented release and retention of those biomolecules along with activation and aggregation. Taken together with our previous data regarding platelet adhesion, these findings suggest that especially when treated with CaCl₂, platelets immediately adhere on cp-Ti plates to release their stored biomolecules in the absence of plasma proteins and that these biomolecules do not diffuse away, but stay longer in extra-platelet spaces around the platelets by newly formed, immature fibrin fiber fragments. Consequently, these retained biomolecules are anticipated to cooperatively stabilize implants by stimulating alveolar bone regeneration and integration.

Singlet oxygen generated by a new nonthermal atmospheric pressure air plasma device exerts a bactericidal effect on oral pathogens

Oral diseases generally have certain bacteria associated with them. Non-thermal atmospheric pressure plasma (NTAP), generated at atmospheric pressure and room temperature, incorporates several molecules, including reactive oxygen species, that can inactivate various bacteria including oral pathogens. For this reason, several NTAP devices have been developed to treat oral diseases. Use of noble gases can enhance the bactericidal efficacy of NTAP, but this requires additional gas supply equipment. Therefore, a new NTAP device that employs ambient air as the working gas was developed. The device generates non-thermal atmospheric pressure air plasma. Here, the singlet oxygen (¹O₂) levels generated, their bactericidal effects on oral pathogens (Streptococcus mutans, Porphyromonas gingivalis, and Enterococcus faecalis), and the bacterial oxidative stress they imposed were measured. ¹O₂ generation in phosphatebuffered saline was assessed qualitatively using electron spin resonance (ESR) spectroscopy, and bactericidal efficacy was evaluated by counting of colony-forming units/mL. Bacterial oxidative stress was determined by measurement of hydrogen peroxide (H₂O₂) and superoxide dismutase (SOD) activity. ESR indicated that the level of ¹O₂ increased significantly and time-dependently, and was inversely correlated with distance, but the bactericidal effects were correlated only with treatment time (not distance) as H₂O₂ increased and SOD levels decreased, suggesting that the new device has potential applicability for treatment of oral disease.

Immobilization of quaternary ammonium based antibacterial monomer onto dentin substrate by non-thermal atmospheric plasma

Use of non-thermal atmospheric plasma (NTAP) brush on immobilization of dimethylaminohexadecyl methacrylate (DMAHDM) onto dentin bonding substrate, and resulting antibacterial activity against Streptococcus mutans were investigated. A bonding substrate with several-micron-demineralized layer was created from human dentin. DMAHDM was applied onto the demineralized layer with or without plasma exposure. Scanning electron microscopy (SEM) and Fourier transformed infrared (FTIR) spectroscopy were employed to verify immobilization/grafting of DMAHDM onto the substrate. Antibacterial activity of the resulting substrate was assessed by using colony-forming unit (CFU) and confocal scanning laser microscopy. Effects of saliva pellicle treatment and aging process on the above substrate were also evaluated. The SEM/FTIR results demonstrated that NTAP could induce DMAHDM immobilization onto dentin substrate, which was further verified via quantitative FTIR analysis. Comparing with non-plasma-treated, the plasmatreated substrate, with CFU 4 log lower, exhibited much stronger inhibitory effects, which were minimally affected by saliva or aging. The DMAHDM-immobilized dentin substrate showed effective and sustained antibacterial characteristics.

Cold atmospheric pressure plasma for treatment of chronic wounds: drug or medical device?

OBJECTIVE

The use of cold atmospheric pressure plasma (CAPP) as a new therapeutic option to aid the healing of chronic wounds appears promising. Currently, uncertainty exists regarding their classification as medical device or medical drug. Because the classification of CAPP has medical, legal, and economic consequences as well as implications for the level of preclinical and clinical testing, the correct classification is not an academic exercise, but an ethical need.

METHOD

A multidisciplinary team of physicians, surgeons, pharmacists, physicists and lawyers has analysed the physical and technical characteristics as well as legal conditions of the biological action of CAPP.

RESULTS

It was concluded that the mode of action of the locally generated CAPP, with its main active components being different radicals, is pharmacological and not physical in nature.

CONCLUSION

Depending on the intended use, CAPP should be classified as a drug, which is generated by use of a medical device directly at the point of therapeutic application.

Dispersion of OH Radicals in Applications Related to Fear-Free Dentistry Using Cold Plasma

Cold atmospheric plasmas (CAPs) are being used in applications related to dentistry. Potential benefits include tooth whitening/bleaching, the sterilization of dental cavities, and root canal disinfection. Generated reactive species, such as hydroxyl (OH) radicals, play a critical role in the effectiveness of CAPs in dentistry. In the present work, the mandibular jaw and teeth were modeled. The propagation of CAP plume in ambient air was dynamically tracked using the level set method. The transport and dispersion OH radicals away from the nozzle and towards the teeth under treatment were also tracked. The distributions of concentration of OH radicals over the teeth were obtained for nozzle to tooth distances of 2 and 4 mm. The discharge of the OH radicals out of the nozzle was found to be asymmetrical. Interestingly, depending on the type of tooth treated, the dispersion of OH radicals out of the nozzle could be altered. The present model and obtained results could be useful for advancements towards a fear-free dentistry using CAPs.

Side effects by oral application of atmospheric pressure plasma on the mucosa in mice

Cold atmospheric pressure plasma (CAP) has been investigated with promising results for peri-implant diseases treatment. However, prior to in-vivo applications of CAP sources in humans, short-term harmful mucosal damage or other unwanted side effects have to be reviewed. 180 male mice (B6C3F1) were divided into twelve treatment groups (n = 15). The right buccal cheek mucosa was treated with CAP. The first and second group each received continuous 10 sec irradiation with 2 different plasma sources (kINPen09, PS-MWM). The third group was treated with the kINPen09 for one minute. Control groups were treated with a corresponding dose of ultraviolet light for 8 seconds or 48 seconds and the other one was left untreated. The animals were weighed before and after treatment. The animals were sacrificed one day or one week after exposure. Stained tissue samples were histologically examined for tissue damage independently by two experienced pathologists. One day after CAP treatment histological analysis showed focal mucosal erosion with superficial ulceration and necrosis accompanied by a mild inflammatory reaction. One week after CAP treatment, the mucosal defects were completely re-epithelialized, associated with remnants of granulation tissue in the stroma irrespective of treatment duration. Furthermore, no cytological atypia was found and no severe weight loss occurred. The control groups did not show any alterations at all. CAP treatment led to a superficial mucosal damage that healed within few days. Nonetheless, further long-term experiments are necessary to exclude undesirable side effects after longer observation time. Particularly, potential carcinogenic effects must be ruled out prior to the application of CAP treatment in daily dental practice.

Effects of Pretreatment Methods on the Enamel Surface Improving Sealant Adhesion

Is PlasBeam pretreatment an efficient method to improve sealant adhesion onto the enamel surface?The aim of this study isto investigate the effects induced by three pretreatment techniques used to improve sealant adhesion on the enamel surface, respectively standard acid-etching, UV radiations and a new method based on plasma operating at atmospheric pressure, namely the PlasBeam method.The physical-chemical modifications induced onto the enamel surface by the above pretreatments were analyzed using Contact Angle Measurements and Diffuse Reflectance Spectroscopy.The changes in the enamel surface morphology show that the acid-etching pretreatment is mostly efficient in increasing roughness, but this method stimulates the degradation processes that are well-known and turns down the brillianceof the treated surface. On the other hand, the PlasBeam treatment brings a higher roughness at the contact area between sealant and the enamel surface, compared to the UV radiations pretreatments.Moreover, the PlasBeam improves the hydrophilic character of enamel as a practical solution in enhancing the sealant adhesion to the surface. Related to other effects, it has been noticed that thePlasBeam method generates the most reflective enamel surface, whereas the White/Yellow index reaches the minimum level after a 10 second treatment.