Surface modification of several dental substrates by non-thermal, atmospheric plasma brush

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.

Nanostructured ZnO thin film to enhance gutta-percha's adhesion to endodontic sealers

BACKGROUND

Gutta-percha (GP) combined with an endodontic sealer is still the core material most widely used for tridimensional obturation. The sealer acts as a bonding agent between the GP and the root dentinal walls. However, one of the main drawbacks of GP core material is the lack of adhesiveness to the sealer. ZnO thin films have many remarkable features due to their considerable bond strength, good optical quality, and excellent piezoelectric, antibacterial, and antifungal properties, offering many potential applications in various fields. This study aimed to explore the influence of GP surface's functionalization with a nanostructured ZnO thin film on its adhesiveness to endodontic sealers.

METHODS

Conventional GP samples were divided randomly into three groups: (a) Untreated GP (control); (b) GP treated with argon plasma (PT); (c) Functionalized GP (PT followed by ZnO thin film deposition). GP's surface functionalization encompassed a multi-step process. First, a low-pressure argon PT was applied to modify the GP surface, followed by a ZnO thin film deposition via magnetron sputtering. The surface morphology was assessed using SEM and water contact angle analysis. Further comprehensive testing included tensile bond strength assessment evaluating Endoresin and AH Plus Bioceramic sealers' adhesion to GP. ANOVA procedures were used for data statistical analysis.

RESULTS

The ZnO thin film reproduced the underlying surface topography produced by PT. ZnO thin film deposition decreased the water contact angle compared to the control (p < 0.001). Endoresin showed a statistically higher mean bond strength value than AH Plus Bioceramic (p < 0.001). There was a statistically significant difference between the control and the ZnO-functionalized GP (p = 0.006), with the latter presenting the highest mean bond strength value.

CONCLUSIONS

The deposition of a nanostructured ZnO thin film on GP surface induced a shift towards hydrophilicity and an increased GP's adhesion to Endoresin and AH Bioceramic sealers.

Atmospheric plasma treatment: an alternative of HF etching in lithium disilicate glass-ceramic cementation

Objectives: This study aimed to investigate whether the atmospheric pressure plasma jet (APPJ) could modify the surface of lithium disilicate glass ceramics (LDC) instead of hydrofluoric acid (HF) in LDC resin cementation. Methods: Two hundred and thirty-two LDC blocks were randomly divided into seven groups: Group 1 (16 specimens) was the blank control group (without HF or APPJ treatment); Group 2 (36 specimens) was etched by HF; Groups 3-7 (36 specimens each) were treated with APPJ, and the relative air humidity (RAH) of the discharge was 22.8%, 43.6%, 59.4%, 75.2%, and 94.0%, respectively. Three LDC blocks in each group were characterized via X-ray photoemission spectroscopy (XPS) analyses, 3 blocks via contact angle measurements, and other 10 blocks via surface roughness measurements. The residual LDC blocks in groups 2-7 were cemented to composite cylinders. Testing the cemented specimens' shear bond strength (SBS) before and after thermocycling (6,500 cycles of 5°C and 55°C) revealed fracture patterns. Data were analyzed by ANOVA (post hoc: Bonferroni) (α = 0.05). Results: After APPJ treatment, the water contact angle values of APPJ treated blocks dropped from 31.37° to 5.66°, while that of HF etched ones dropped to 18.33°. The O/C ratio increased after HF etching or APPJ treatment according to the calculated results, except for the APPJ-treated samples at a RAH of 22.8%. The surface roughness of LDC blocks showed no statistic difference before and after APPJ treatment, but experienced significant difference after HF etching. The O/Si and O/C ratios varied after HF etching or APPJ treatment. No significant difference in SBS values could be found among groups 2-7 before or after artificial aging (p > 0.05). All specimens showed mixed failure patterns. Conclusion: The APPJ treatment method reported in this study is a promising novel strategy for surface modification of the LDC. With acceptable bonding strength, it might be an alternative to HF in LDC-resin cementation.

Gas Plasma Treatment Improves Titanium Dental Implant Osseointegration-A Preclinical In Vivo Experimental Study

Recent technological advancements led to the development of various plasma-based technologies for post-packaging modifications. The purpose of the present preclinical in vivo study was to assess the safety and efficacy of a novel chairside nonthermal gas plasma treatment for enhancing osseointegration of titanium implants. Six male mixed foxhounds underwent extraction of mandibular premolars and first molars, and the sockets healed for 42 days. Canine mandibles were randomized to receive either plasma-treated (test) or non-plasma-treated (control) dental implants. A total of 36 implants were placed in six animals, and they were sacrificed at 2 weeks (two animals), 4 weeks (two animals), and 6 weeks (two animals) after the implant surgery. When the radiographic analysis was performed, the changes in bone level were not statistically significant between the two groups at 2 weeks and 4 weeks. The difference became significant at 6 weeks (p = 0.016), indicating more bone loss from baseline to 6 weeks for the control group. The bone-to-implant contact (BIC) appeared to be higher for the test groups at all time points, and the BIC was significantly higher for the test group at 4 weeks (p = 0.046). In conclusion, this study underscored the potential of nonthermal plasma treatment in enhancing implant osseointegration.

Functionalization of gutta-percha surfaces with argon and oxygen plasma treatments to enhance adhesiveness

Gutta-percha's lack of adhesion has been presented as a drawback to avoid gaps at sealer/gutta-percha interface. Plasma treatments have been scarcely assessed on gutta-percha surfaces as a method of enhancing adhesiveness. This study aimed to evaluate the effect of low-pressure Argon and Oxygen plasma atmospheres on conventional and bioceramic gutta-percha standardized smooth discs, assessing their roughness, surface free energy, chemical structure, and sealer wettability. A Low-Pressure Plasma Cleaner by Diener Electronic (Zepto Model) was used. Different gases (Argon or Oxygen), powers (25 W, or 50 W), and exposure times (30 s, 60 s, 120 s, or 180 s) were tested in control and experimental groups. Kruskal-Wallis and Student's t-test were used in data analysis. Statistically significant differences were detected when P < 0.05. Both gases showed different behaviors according to the parameters selected. Even though chemical changes were detected, the basic molecular structure was maintained. Argon or Oxygen plasma treatments favoured the wetting of conventional and bioceramic gutta-perchas by Endoresin and AH Plus Bioceramic sealers (P < 0.001). Overall, the functionalization of gutta-percha surfaces with Argon or Oxygen plasma treatments can increase roughness, surface free energy and wettability, which might improve its adhesive properties when compared to non-treated gutta-percha.

Influence of nonthermal argon plasma on the micro-shear bond strength between resin cement and translucent zirconia

Background

Considering the potential of translucent zirconia for application in esthetic restorations, it is necessary to find effective methods with the least adverse effects to increase its bond strength to resin cement.

Aims

This study aimed to test if different conservative surface treatments and cement types could affect the micro-shear bond strength (μSBS), failure mode, and bonding interface between resin cement and translucent zirconia.

Materials and Methods

In this in vitro experimental study, translucent zirconia blocks were divided into four groups based on the surface treatment they received: no treatment, argon plasma, primer (Pr), and Pr + plasma. Each group was further divided into two subgroups based on the applied cement: PANAVIA F2 and Duo-Link cement. Fourteen cement columns with a diameter of 1 mm were placed on each block (n = 14); all the specimens were immersed in 37°C water for 24 h. Afterward, μSBS was evaluated (P < 0.05), and the mode of failure was determined by a stereomicroscope (×10). The cement-zirconia interface and the surface hydrophilicity (contact angle) were also evaluated.

Statistical Analysis

Two-way analysis of variance (ANOVA) was used to evaluate the effect of surface preparation, cement types, and incubator, simultaneously (P < 0.05). The bond strengths after incubation were analyzed by one-way ANOVA (P < 0.05). Failure mode, contact angle, and cement-zirconia interface were analyzed descriptively.

Results

The highest bond strength was seen in Pr surface treatment for Duo-Link cement; however, this group was not significantly different from Pr and PANAVIA F2 cement and Pr + plasma and Duo-Link cement (P = 0.075) groups. All plasma specimens in the incubator failed prematurely. The mode of failure in all specimens was adhesive. The lowest and highest contact angles were seen in Pr + plasma and the control groups, respectively.

Conclusion

The use of Pr could successfully improve the bond strength of resin cement to translucent zirconia while plasma was not an acceptable and durable substitute.

Effect of nonthermal atmospheric plasma on bond strength of composite resin using total-etch and self-etch adhesive systems

Aim

The aim of this study was to assess the impact of nonthermal atmospheric plasma (NTAP) on the bond strength of composite resin following plasma application at different steps of dentin bonding in total-etch and self-etch adhesive systems.

Materials and Methods

Ninety extracted third molars were taken, and the occlusal surfaces were removed until the exposure of the dentin. Samples were distributed into two main groups: Group T: total-etch adhesive system and Group S: self-etch adhesive system. Groups are further subdivided (n = 10) based on plasma application at different steps of dentin bonding. T1: surface etching with 37% phosphoric acid and bonding agent application. T2: plasma application and bonding agent application. T3: plasma application, etching, and bonding agent application. T4: etching, plasma application, and bonding agent application. T5: etching, plasma application, bonding agent application, and again plasma application. S1: self-etch bonding agent application. S2: plasma application and bonding agent application. S3: Bonding agent application and plasma application. S4: plasma application, bonding agent application, and again plasma application. For all the samples, composite resin buildup was done, and shear bond strength (SBS) was measured. The contact angle was measured at different steps of dental adhesive systems.

Statistical Analysis

Two-way analysis of variance and the post hoc Tukey's test were used for analysis, regarding P < 0.05 as statistically significant.

Results

Among all groups of total-etch and self-etch adhesives, Group T4 (48.81 Mpa) and Group S2 (36.59 Mpa), respectively, have demonstrated significantly greater bond strength values than the corresponding control groups.

Conclusion

NTAP enhanced the composite resin's SBS when plasma treatment was done before bonding agent application and significantly reduced the contact angles of the distilled water.

A confocal laser scanning microscopic evaluation of nonthermal atmospheric plasma on the dentinal tubule penetration of bioceramic and epoxy resin-based root canal sealers

Aim

Using confocal laser scanning microscopy (CLSM), the current study assessed the impact of nonthermal atmospheric plasma (NTAP) on the dentinal tubule penetration of bioceramic and epoxy resin-based root canal sealers (CLSM).

Materials and Methods

Forty human mandibular premolar teeth with a single root that had just undergone extraction were chosen and biomechanical preparation of root canals was done with ProTaper Gold rotary Nickel-titanium instruments. Samples were divided into four groups (n = 10). Group 1: Bioceramic sealer (BioRoot RCS); Group 2: Epoxy resin-based sealer (AH Plus) without application of NTAP; Group 3: Bioceramic sealer (BioRoot RCS); and Group 4: Epoxy resin-based sealer (AH Plus) with the application of NTAP for 30 s. In Groups 3 and 4, all of the samples underwent obturation with the appropriate sealers following NTAP application. For determination of the sealer's dentinal tubule penetration values, slices with a thickness of 2 mm were taken from the middle third of sample's root and examined using CLSM. The acquired data were statistically analyzed with one-way analysis of variance and the Post hoc Tukey's test. The cutoff for statistical significance was P < 0.05.

Results

In comparison to other groups, the maximum sealer penetration values into dentinal tubules were significantly higher in Group 3 for Bioceramic sealer with NTAP application and Group 4 for Epoxy resin-based sealer with NTAP application.

Conclusion

NTAP application increased the dentinal tubule penetration of bioceramic and epoxy resin-based sealers in comparison to groups without NTAP application.

Assessment of Inhibition of Biofilm Formation on Non-Thermal Plasma-Treated TiO2 Nanotubes

Peri-implantitis is an inflammatory disease similar to periodontitis, caused by biofilms formed on the surface of dental implants. This inflammation can spread to bone tissues and result in bone loss. Therefore, it is essential to inhibit the formation of biofilms on the surface of dental implants. Thus, this study examined the inhibition of biofilm formation by treating TiO₂ nanotubes with heat and plasma. Commercially pure titanium specimens were anodized to form TiO₂ nanotubes. Heat treatment was performed at 400 and 600 °C, and atmospheric pressure plasma was applied using a plasma generator (PGS-200, Expantech, Suwon, Republic of Korea). Contact angles, surface roughness, surface structure, crystal structure, and chemical compositions were measured to analyze the surface properties of the specimens. The inhibition of biofilm formation was assessed using two methods. The results of this study showed that the heat treatment of TiO₂ nanotubes at 400 °C inhibited the adhesion of Streptococcus mutans (S. mutans), associated with initial biofilm formation, and that heat treatment of TiO₂ nanotubes at 600 °C inhibited the adhesion of Porphyromonas gingivalis (P. gingivalis), which causes peri-implantitis. Applying plasma to the TiO₂ nanotubes heat-treated at 600 °C inhibited the adhesion of S. mutans and P. gingivalis.

The effect of argon cold atmospheric plasma on the metabolism and demineralization of oral plaque biofilms

Objective

The aim of this study was to design and optimize a cold atmospheric plasma (CAP) device that could be applied in an oral environment and to study its effects on plaque biofilm metabolism and regrowth, as well as microbial flora composition and enamel demineralization.

Method

CAP was obtained through a dielectric barrier discharge device; the optical properties were analyzed using emission spectroscopy. The electrochemical analysis of plasma devices includes voltametric characteristic curves and Lissajous. The Streptococcus mutans (UA159) and saliva biofilms were treated in vitro, and the effects of CAP on biofilm metabolism were investigated using MTT and lactate dehydrogenase assays. The duration of antibacterial activity on biofilms was examined, scanning electron microscopy was used to observe the morphology of biofilms, and 16S rRNA sequencing was used to explore the influence of CAP on the microbial flora composition of saliva biofilms. An in vitro model of biofilm-enamel demineralization was designed, and the effect of CAP on enamel demineralization was evaluated by micro surface hardness and micro-CT analysis.

Results

CAP had antibacterial proliferative ability toward Streptococcus mutans biofilms and saliva biofilms and was stronger than ultraviolet under the same tested conditions. After 24 h, the antibacterial effect disappeared, which proved the short-term timeliness of its bactericidal ability. CAP can inhibit the acid production of biofilms, and its inhibitory effect on saliva biofilms can be extended to 24 h. CAP had a strong ability to regulate the composition of plaque biofilms, especially for Lactococcus proliferation, a major acid-producing bacterium in microcosm biofilms. The CAP-treated enamels were more acid-tolerant than non-treated controls.

Conclusion

CAP had an explicit bactericidal effect on caries-related biofilms, which is a short-term antibacterial effect. It can inhibit the acid production of biofilms and has a downregulation effect on Lactococcus in saliva biofilms. CAP can help reduce demineralization of enamel.

Reactive Oxygen Species Enlightened Therapeutic Strategy for Oral and Maxillofacial Diseases-Art of Destruction and Reconstruction

Reactive oxygen species (ROS) are byproducts of cell metabolism produced by living cells and signal mediators in biological processes. As unstable and highly reactive oxygen-derived molecules, excessive ROS production and defective oxidant clearance, or both, are associated with the pathogenesis of several conditions. Among them, ROS are widely involved in oral and maxillofacial diseases, such as periodontitis, as well as other infectious diseases or chronic inflammation, temporomandibular joint disorders, oral mucosal lesions, trigeminal neuralgia, muscle fatigue, and oral cancer. The purpose of this paper is to outline how ROS contribute to the pathophysiology of oral and maxillofacial regions, with an emphasis on oral infectious diseases represented by periodontitis and mucosal diseases represented by oral ulcers and how to effectively utilize and eliminate ROS in these pathological processes, as well as to review recent research on the potential targets and interventions of cutting-edge antioxidant materials. The PubMed, Web of Science, and Embase databases were searched using the MesH terms "oral and maxillofacial diseases", "reactive oxygen species", and "antioxidant materials". Irrelevant, obsolete, imprecise, and repetitive articles were excluded through screening of titles, abstracts, and eventually full content. The full-text data of the selected articles are, therefore, summarized using selection criteria. While there are various emerging biomaterials used as drugs themselves or delivery systems, more attention was paid to antioxidant drugs with broad application prospects and rigorous prophase animal experimental results.

Improvement of osseointegration efficacy of titanium implant through plasma surface treatment

A novel plasma treatment source for generating cylindrical plasma on the surface of titanium dental implants is developed herein. Using the titanium implant as an electrode and the packaging wall as a dielectric barrier, a dielectric barrier discharge (DBD) plasma was generated, allowing the implant to remain sterile. Numerical and experimental investigations were conducted to determine the optimal discharge conditions for eliminating hydrocarbon impurities, which are known to degrade the bioactivity of the implant. XPS measurement confirmed that plasma treatment reduced the amount of carbon impurities on the implant surface by approximately 60%. Additionally, in vitro experiments demonstrated that the surface treatment significantly improved cell adhesion, proliferation, and differentiation. Collectively, we proposed a plasma treatment source for dental implants that successfully removes carbon impurities and facilitate the osseointegration of SLA implants.

Enhancing Resin Cement Adhesion to Zirconia by Oxygen Plasma-Aided Silicatization

The combinations of alumina particle air abrasion (AA) and a 10-methacryloyloxyidecyl-dihyidrogenphosphate (MDP) primer and a tribochemical silica coating (TSC) and a silane-base primer are contemporary pre-cementation treatments for zirconia restorations for bonding with resin cements. However, the stability of zirconia resists the mechanical or chemical preparations. The purpose of this study was to develop an atmospheric-pressure oxygen plasma (OP)-aided silicatization method to enhance the adhesion of resin cements to zirconia. Zirconia discs were prepared to receive surface treatments of different combinations: (1) AA or TSC (2) with or without OP treatment, and (3) a chemical primer (no primer, silane, or a silane-MDP mixture). The surface morphology, hydrophilicity, and chemical compositions were characterized, and the resin-zirconia bond strengths were examined either after 24 h or a thermocycling test. The results indicated that the OP treatment after the TSC facilitated the homogeneous distribution of silane and crosslinking of silica particles, and effectively improved the hydrophilicity. The OP increased the O and Si and reduced the C elemental contents, while the combination of TSC, OP, and silane induced SiO_x generation. Among the groups, only the TSC-OP-silane treatment effectively enhanced the bond strength and maintained the adhesion after thermocycling. With these results, the OP aided the silicatization protocol effectively, generated silane crosslinking, and resulted in superior resin-zirconia bond strength and durability compared to the current treatments.

The Measurement of Contact Angle, pH, and Conductivity of Artificial Saliva and Mouthwashes on Enamel, Glass-Ionomer, and Composite Dental Materials

The aim of this study was to tackle the topic of appropriate recommendations for artificial-saliva and mouthwash usage. The contact angle, pH, and conductivity of two artificial saliva solutions, four mouthwashes, and their mixtures on enamel, glass-ionomer, and composite dental materials were measured. The measurements were conducted with a MATLAB algorithm to minimize human error. The obtained values for the contact angle were in the range from 7.98° to 52.6°, and they showed completely nonlinear and nonuniform behavior for all investigated liquids and on all investigated substrates. Results reveal statistically significant differences among all tested liquids on all investigated substrates (p < 0.05). pH values ranged from 1.54 to 7.01. A wide range of conductivity values were observed, from 1205µS/cm in the saliva-stimulating solution to 6679 mS/cm in the artificial saliva. Spearman’s test showed a moderate positive correlation between the pH and conductivity of the tested fluids (R = 0.7108). A comparison of the data obtained using Image J software and the MATLAB algorithm showed consistency, not exceeding 5% error. When an experiment uses human material and bioactive materials THAT are used in biomedicine as substrates, an additional definition of protocols is highly recommended for future research on this topic.

Effect of Helium Plasma Exposure on Wettability and Shear Bond Strength between the Zirconia Core and Feldspathic Veneering Ceramic: An In Vitro Study

Introduction. The present study aimed to evaluate the effect of helium plasma treatment on the wettability of zirconia surface and on the shear bond strength between the dental zirconia core and feldspathic veneering ceramic. Methods. 128 zirconia specimens were prepared, polished, and then divided into four groups: control, Zr, FC, and Zr/FC. In Zr and Zr/FC groups, the zirconia blocks were treated by helium plasma for 60 s. In FC and Zr/FC, the feldspathic ceramic powder received 60 s of plasma treatment. Then, the feldspathic powder was applied on the zirconia blocks. Half of the specimens in each group were sintered in a tube furnace, and the contact angle between the zirconia core and feldspathic ceramic was measured at different time intervals. The other half were sintered in a ceramic furnace and then subjected to thermocycling. The shear bond strength was measured using a universal testing machine. The failure mode was assessed using a stereomicroscope. Data were analyzed by one-way ANOVA test, and the statistical significance was considered less than 0.05. Results. There was no significant difference in the mean contact angle and the shear bond strength values of the experimental groups ( $P>0.05$ ). The mean contact angle decreased significantly in all groups over time ( $P<0.001$ ). The modes of failure were predominantly mixed in all groups. Conclusion. The helium plasma applied on either dental zirconia core or feldspathic ceramic powder could not improve the zirconia surface wettability and the shear bond strength between the two ceramics.

Characterization of cold atmospheric plasma-modified dentin collagen

The aim of this study was to evaluate the crosslinking effect of the radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma jet treatment on dentin collagen. The dentin collagen was treated by an RF-APGD plasma jet with the gas temperature of 4°C under different treatment times, while the control was a non-treatment group. The dentin collagen was characterized in terms of atomic force microscopy-based nanoindentation, differential scanning calorimeter, Raman analysis and X-ray photoelectron spectroscopy (XPS) measurement. The crosslinking effect of the plasma-treated dentin collagen was found compared to that of the control group. The elastic modulus and denaturation temperature of the dentin collagen after plasma treatment for 30 s were significantly higher than those in the control group (p<0.05). The RF-APGD plasma jet treatment can promote the crosslinking of the dentin collagen, which is of great significance to improve its mechanical and thermal stabilities.

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.

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

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

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

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

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

Resin Cement-Zirconia Bond Strengthening by Exposure to Low-Temperature Atmospheric Pressure Multi-Gas Plasma

The purpose of this study was to investigate the effect of gas species used for low-temperature atmospheric pressure plasma surface treatment, using various gas species and different treatment times, on zirconia surface state and the bond strength between zirconia and dental resin cement. Three groups of zirconia specimens with different surface treatments were prepared as follows: untreated group, alumina sandblasting treatment group, and plasma treatment group. Nitrogen (N₂), carbon dioxide (CO₂), oxygen (O₂), argon (Ar), and air were employed for plasma irradiation. The bond strength between each zirconia specimen and resin cement was compared using a tension test. The effect of the gas species for plasma irradiation on the zirconia surface was investigated using a contact angle meter, an optical interferometer, an X-ray diffractometer, and X-ray photoelectric spectroscopy. Plasma irradiation increased the wettability and decreased the carbon contamination on the zirconia surface, whereas it did not affect the surface topography and crystalline phase. The bond strength varied depending on the gas species and irradiation time. Plasma treatment with N₂ gas significantly increased bond strength compared to the untreated group and showed a high bond strength equivalent to that of the sandblasting treatment group. The removal of carbon contamination from the zirconia surface and an increase in the percentage of Zr-O₂ on the zirconia surface by plasma irradiation might increase bond strength.

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.

Atmospheric Pressure Plasma Activation of Hydroxyapatite to Improve Fluoride Incorporation and Modulate Bacterial Biofilm

Despite the technological progress of the last decade, dental caries is still the most frequent oral health threat in children and adults alike. Such a condition has multiple triggers and is caused mainly by enamel degradation under the acidic attack of microbial cells, which compose the biofilm of the dental plaque. The biofilm of the dental plaque is a multispecific microbial consortium that periodically develops on mammalian teeth. It can be partially removed through mechanical forces by individual brushing or in specialized oral care facilities. Inhibition of microbial attachment and biofilm formation, as well as methods to strengthen dental enamel to microbial attack, represent the key factors in caries prevention. The purpose of this study was to elaborate a cold plasma-based method in order to modulate microbial attachment and biofilm formation and to improve the retention of fluoride (F-) in an enamel-like hydroxyapatite (HAP) model sample. Our results showed improved F retention in the HAP model, which correlated with an increased antimicrobial and antibiofilm effect. The obtained cold plasma with a dual effect exhibited through biofilm modulation and enamel strengthening through fluoridation is intended for dental application, such as preventing and treating dental caries and enamel deterioration.

Non-thermal plasma for surface treatment of inorganic fillers added to resin-based cements

OBJECTIVES

This study aims to evaluate the effect of non-thermal plasma (NTP) surface treatment in two composite inorganic fillers and evaluate their impact on the chemical-mechanical properties and bond strength ability of experimental resin cements.

MATERIALS AND METHODS

Ytterbium fluoride (YF) and barium silicate glass (BS) were characterized and submitted to different surface treatments: non-thermal plasma (NTP); non-thermal plasma and 3-(trimethoxysilyl) propyl methacrylate silanization; and 3-(trimethoxysilyl) propyl methacrylate silanization. Untreated fillers were used as a control. The fillers were incorporated at 65wt% concentration into light-cured experimental resin cements (50wt% BisGMA; 25wt% UDMA; 25wt% TEGDMA; 1mol% CQ). The degree of conversion, the flexural strength, and the microshear bond strength (μSBS) were evaluated to characterize developed composites.

RESULTS

YF and BS were successfully cleaned with NTP treatment. Nor NTP neither the silanization affected the degree of conversion of resin cements. The NTP predicted an increase in YF-containing resin cements flexural strength, reducing the storage impact in these materials. NTP treatment did not affect the μSBS when applied to YF, while silanization was effective for BS-containing materials.

CONCLUSION

NTP treatment of inorganic particles was possible and was shown to reduce the amount of organic contamination of the particle surface. YF surface treatment with NTP can be an alternative to improve the organic/inorganic interaction in resin composites to obtain materials with better mechanical properties.

CLINICAL RELEVANCE

Surface cleaning with NTP may be an alternative for particle surface cleaning to enhance organic-inorganic interaction in dental composites resulting in improved mechanical strength of experimental resin cements.

Exploring Emerging Technologies with Analysis of Bibliographic Data Focused on Plasma Surface Treatment

Research trends and emerging technologies were explored through the Web of Science (WoS) literature of the last decade in relation to plasma technology, especially plasma surface treatment, widely used in all industries. For this, a network analysis using country and author keywords and emerging technology search algorithms, with regard to novelty, fast growth and impact, were used. As a result, we derived 40 keywords in terms of novelty and fast growth. Additionally, with these keywords, we traced the impact based on the citation relationships. Finally, nine keywords which were analyzed to contain many new technological issues were identified by deriving the author keywords included in the relevant documents. It is expected that the new technology fields derived from this paper can contribute to establishing a preemptive R&D strategy.

Effects of a helium cold atmospheric plasma on bonding to artificial caries-affected dentin

This study investigated the effects of a helium cold atmospheric plasma (CAP) on the bonding performance and surface modification of the caries-affected dentin (CAD). Artificial CAD was created by pH-cycling. The microtensile bond of CAD were examined before and after CAP treatments at 24 h and after 2-year aging. The effects of surface modification were studied with contact-angle measurement, scanning electron microscopy and X-ray photoemission spectroscopy. Thirty-second CAP treatment increased the immediate bond strength of CAD to a level that was statistically the same as sound dentin, and slowed the aging process of the bonding as well. The CAP treatment induced modified CAD surface with increased wettability, cleaner appearance, and increased percentage of the mineral-associated elements and oxygen. This research demonstrated that the helium CAP jet treatments of 30 s and 45 s improved the bond strength of the artificial CAD, and was considerably effective in its surface modification.

The effect of atmospheric cold plasma on the dentinal tubule penetration of calcium silicate-based sealer used with different obturation techniques: A confocal laser scanning microscopy study

The aim of this study was to evaluate the effect of atmospheric cold plasma (ACP) on dentinal tubule penetration of EndoSequence BC. Sixty premolars were divided into four groups according to the obturation technique and plasma treatment. Root canals were filled with single cone in Group 1 (SC), single cone after ACP application in Group 2 (SC-P), warm vertical compaction in Group 3 (WVC), warm vertical compaction after ACP application in Group 4 (WVC-P). Horizontal sections were imaged using confocal laser scanning microscopy. The maximum penetration and percentage of penetration values were measured. These data were statistically analysed (P < 0.01). In the coronal region, the percentage of penetration values were higher in SC-P and WVC-P than in SC and WVC. In the middle region, SC-P and SC showed a higher penetration percentage than WVC and WVC-P. In the apical region, WVC showed a higher percentage of penetration value than SC-P, WVC-P and SC did. Maximum penetration of WVC was higher than of SC and SC-P. Within the limitations of this study, ACP improved the percentage of penetration values of EndoSequence BC when used with single-cone technique.

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.

In vitro study on how cold plasma affects dentin surface characteristics

PURPOSE

Studies evaluating different features of cold plasma action on dentin surface characteristics are lacking. Thus, this in vitro study aimed to determine the effect of cold plasma under different protocols of exposure time, distance to plasma source, and the association of argon gas with distinct concentrations of oxygen on the wettability, surface energy, total free interaction energy, surface roughness, morphology and chemical composition of dentin.

MATERIAL AND METHODS

One hundred and twenty-five bovine dentin samples were used and divided into twenty-five groups according to the exposure time to plasma (15, 30, or 60 s); distance between plasma source and dentin surface (3 or 6 mm); argon gas without plasma generation; and plasma generated by argon gas and association of argon gas with distinct concentrations of oxygen (2 % or 3 %) (n = 5). Contact angle (θ), surface energy (γs) and total free interaction energy (ΔG) were measured using a goniometer (Krüss), while surface roughness (Ra) was evaluated by a profilometer (Mitutoyo). Representative samples were submitted to scanning electron microscopy (JEOL) to ilustrate the morphology and chemical composition of dentin. Data comparing control group with all experimental groups were submitted to ANOVA followed by Tukey's test (α = .05). Data comparing oxygen gas action at different concentrations and argon gas on dentin characteristics were submitted to non-parametric Kruskal-Wallis test, followed by Dunn test for comparison between the groups and methods (α = 0.05).

RESULTS

In general, argon gas without plasma generation promoted no significant difference on dentin surface characteristics compared to control group (P > .05), differently for the cold plasma that significantly reduced contact angle values and increased total free interaction energy of dentin surface (P < .05). Overall, feeding of oxygen at distinct concentrations promoted significant difference on dentin surface characteristics compared to control group (P < .05). Exposure time and distance protocols interfered with contact angle, surface energy and total free interaction energy analyses for each gas. There was no significant difference on surface roughness (P > .05), morphology and chemical composition of dentin submitted to argon gas, cold plasma, and distinct concentrations of oxygen.

CONCLUSION

In conclusion, plasma generated by argon gas and its feeding with 2 % and 3 % oxygen gas improved the dentin surface characteristics about wettability, surface energy and total free interaction energy. Such treatments preserved the surface roughness, morphology and chemical composition of dentin. The protocols of groups Ar-6mm-15sec, ArO2-3mm-30sec and ArO3-3mm-15sec are recommended for improvement of dentin surface characteristics.

Effects of non-thermal atmospheric plasma on dentin wetting and adhesive bonding efficiency: Systematic review and meta-analysis

OBJECTIVES

This systematic review and meta-analysis evaluated the effects of non-thermal atmospheric plasma (NTAP) treatment on dentin wetting and adhesive-dentin bond strength.

DATA/SOURCES

This report followed the PRISMA 2020 statement. Two reviewers conducted literature search of MEDLINE, Web of Science and Scopus databases up to the end of November 2020. Included in vitro studies compared the effect of NTAP on treated dentin of non-carious, intact, extracted human third molar teeth with different control groups. Studies with no adequate methods, missing data, lack of control group, or those using animal teeth were excluded. The random effects model was used to summarize the treatment effect with standardized mean difference (SMD) and 95% CI. Risk of bias was assessed using the custom Cochrane Collaboration's tool.

STUDY SELECTION/RESULTS

Seventeen studies met inclusion criteria. The effects on dentin wetting were reported in favor of NTAP (SMD -5.38; 95% CI [-6.97, -3.78]; p<0.00001; I2=81%). Regarding adhesive-dentin bond strength, statistically significant differences between the NTAP and control group were in favor of NTAP in the short-term (SMD 1.92; 95%CI [1.35, 2.50]; p<0.00001; I2=97%), and long-term (SMD 3.28; 95%CI [2.46, 4.09]; p<0.00001; I2=97%). A limitation of meta-analysis is moderate heterogeneity caused by methodological differences and lack of data, which was evaluated through risk of bias and sensitivity analysis.

CONCLUSIONS

NTAP substantially improves dentin wetting and adhesive-dentin bond strength with 30 seconds exposure time and up to 10 mm tip-to-surface distances being sufficient for positive NTAP effects on bonding efficiency.

FUNDING

ON172207 and III41008 from the Ministry of Education, Science and Technological Development, Republic of Serbia. NP is funded by MESTD grant number 451-03-68/2020-14/200024.

CLINICAL SIGNIFICANCE

This systematic review and meta-analysis substantiate potential applicability of NTAP treatment of dentin in improving adhesive bonding clinically. Further research should be based on the optimized parameters such as time and distance with additional refinement of NTAP power.

Effect of Cold Atmospheric Pressure Plasma Coupled with Resin-Containing and Xylitol-Containing Fluoride Varnishes on Enamel Erosion

Purpose

Considering the suggested advantages of cold atmospheric plasma (CAP) in increasing the fluoride uptake by the enamel, this study aimed to assess enamel erosion following the application of helium CAP and two types of fluoride varnishes.

Methods

The microhardness of 70 bovine enamel specimens was measured using a Vickers hardness tester. The specimens were randomly divided into 7 groups (n = 10): control, CAP (P), resin-containing fluoride varnish (RF), CAP + resin-containing fluoride varnish (PRF), fluoride varnish (F), CAP + fluoride varnish (PF), and erosion (E). The specimens in the control and erosion groups did not receive CAP or fluoride varnish. All specimens underwent erosive challenge 4 times/day using hydrochloric acid and artificial saliva except for the control specimens that remained in distilled water during the course of the study. After 5 days of erosive challenge, microhardness was measured again, and the percentage of microhardness change was calculated. Surface roughness of two specimens in each group was assessed by atomic force microscopy (AFM). Data were analyzed using one-way ANOVA followed by Tamhane's post-hoc test.

Results

The percentage of microhardness change in all groups was significantly higher than that of the control group. All groups showed significantly lower percentage of microhardness change compared with the E group except for the P group; no significant difference was noted in microhardness change of P and E groups. Other experimental groups had no significant difference with each other. Surface roughness was the highest in PRF and the lowest in the F group.

Conclusion

CAP application had no significant effect on increasing the enamel resistance to erosion. However, enamel resistance to erosion increased significantly after fluoride varnish application alone or fluoride varnish application combined with CAP. No significant difference was noted between the two types of varnishes in this regard. CAP increased the surface roughness while fluoride varnish application alone decreased the roughness.

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.

Influence of Non-Thermal Atmospheric Pressure Plasma Treatment on Retentive Strength between Zirconia Crown and Titanium Implant Abutment

The aim of this study is to investigate the effect of non-thermal atmospheric pressure plasma (NTP) on retentive strength (RS) between the zirconia crown and the titanium implant abutment using self-adhesive resin cement. Surface free energy (SFE) was calculated on 24 cube-shaped zirconia blocks, and RS was measured on 120 zirconia crown-titanium abutment assemblies bonded with G-CEM LinkAce. The groups were categorized according to the zirconia surface treatment as follows: Control (no surface treatment), NTP, Si (Silane), NTP + Si, Pr (Z-Prime Plus), and NTP + Pr. Half of the RS test assemblies were aged by thermocycling for 5000 cycles at 5–55 °C. The SFE was calculated using the Owens-Wendt method, and the RS was measured using a universal testing machine at the maximum load until failure. One-way analysis of variance (ANOVA) with post-hoc Tukey honestly significant difference (HSD) was performed to evaluate the effect of surface treatments on the SFE and RS. Independent sample t-test was used to compare the RS according to thermocycling (p < 0.05). For the SFE analysis, the NTP group had a significantly higher SFE value than the Control group (p < 0.05). For the RS test, in non-thermocycling, the NTP group showed a significantly higher RS value than the Control group (p < 0.05). However, in thermocycling, there was no significant difference between the Control and NTP groups (p > 0.05). In non-thermocycling, comparing with the NTP + Si or NTP + Pr group, there was no significant difference from the Si or Pr group, respectively (p > 0.05). Conversely, in thermocycling, the NTP + Si and NTP + Pr group had significantly lower RS than the Si and Pr group, respectively (p < 0.05). These results suggest that NTP single treatment for the zirconia crown increases the initial RS but has little effect on the long-term RS. Applied with Silane or Z-Prime Plus, NTP pre-treatment has no positive effect on the RS.

Plasma bioscience and its application to medicine

Nonthermal atmospheric pressure biocompatible plasma (NBP), alternatively called bio-cold plasma, is a partially ionized gas that consists of charged particles, neutral atoms and molecules, photons, an electric field, and heat. Recently, nonthermal plasma-based technology has been applied to bioscience, medicine, agriculture, food processing, and safety. Various plasma device configurations and electrode layouts has fast-tracked plasma applications in the treatment of biological and material surfaces. The NBP action mechanism may be related to the synergy of plasma constituents, such as ultraviolet radiation or a reactive species. Recently, plasma has been used in the inactivation of viruses and resistant microbes, such as fungal cells, bacteria, spores, and biofilms made by microbes. It has also been used to heal wounds, coagulate blood, degrade pollutants, functionalize material surfaces, kill cancers, and for dental applications. This review provides an outline of NBP devices and their applications in bioscience and medicine. We also discuss the role of plasma-activated liquids in biological applications, such as cancer treatments and agriculture. The individual adaptation of plasma to meet specific medical requirements necessitates real-time monitoring of both the plasma performance and the target that is treated and will provide a new paradigm of plasma-based therapeutic clinical systems.

Bond Strength of Universal Adhesives to Dentin: A Systematic Review and Meta-Analysis

Currently, the availability of a wide variety of universal adhesives makes it difficult for clinicians to choose the correct system for specific bonding situations to dentin substrate. This study aimed to determine whether there are any alternative techniques or additional strategies available to enhance the bond strength of universal adhesives to dentin through a systematic review and meta-analysis. Two reviewers executed a literature search up to September 2020 in four electronic databases: PubMed, ISI Web of Science, Scopus, and EMBASE. Only in vitro studies that reported the dentin bond strength of universal adhesives using additional strategies were included. An analysis was carried out using Review Manager Software version 5.3.5 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). The methodological quality of each in vitro study was assessed according to the parameters of a previous systematic. A total of 5671 potentially relevant studies were identified. After title and abstract examination, 74 studies remained in systematic review. From these, a total of 61 studies were included in the meta-analysis. The bond strength of universal adhesives to dentin was improved by the use of one of the following techniques: Previous application of matrix metalloproteinases (MMP) inhibitors (p < 0.001), prolonged application time (p = 0.007), scrubbing technique (p < 0.001), selective dentin etching (p < 0.001), non-atmospheric plasma (p = 0.01), ethanol-wet bonding (p < 0.01), prolonged blowing time (p = 0.02), multiple layer application (p = 0.005), prolonged curing time (p = 0.006), and hydrophobic layer coating (p < 0.001). On the other hand, the use of a shortened application time (p = 0.006), and dentin desensitizers (p = 0.01) impaired the bond strength of universal adhesives to dentin. Most of the analyses performed showed a high heterogenicity. The in vitro evidence suggests that the application of universal adhesives using some alternative techniques or additional strategies may be beneficial for improving their bonding performance to dentin. This research received no external funding. Considering that this systematic review was carried out only with in vitro studies, registration was not performed.

Effect of Non-Thermal Atmospheric Plasma on Micro-Tensile Bond Strength at Adhesive/Dentin Interface: A Systematic Review

Objective: The objective of this review was to evaluate the effect of non-thermal atmospheric plasma (NTAP) on adhesives resin–dentin micro-tensile bond strength (μTBS) in previously published studies. Methods: Electronic search was conducted using the Medline, Cochrane library, and Scopus databases. The included studies were laboratory studies that investigated the effect of NTAP on adhesives μTBS to coronal dentin. Studies that evaluated the effect of NTAP on bond strength to indirect substrates, enamel or root dentin, were excluded. The methodological quality of included studies was assessed. Results: Thirteen studies were included in this systematic review. All the included studies were considered to have a medium risk of bias. NTAP significantly improved μTBS at 24 h or after short-term aging in five studies (38.5%) and both immediate and after long-term aging in 5 studies (38.5%). In two studies (15.4%), NTAP resulted in a short-term material-dependent effect that was not stable after long-term aging. Interestingly, in one study (7.7%), NTAP had a positive effect only in the etch-and-rinse (ER) mode after long-term aging. Conclusion: Within the limitations of this systematic review, NTAP application could enhance resin–dentin μTBS of ER adhesives or universal adhesives (UAs) applied in the ER mode. In the ER mode, the rewetting step after NTAP seems to be unnecessary. Because of the limited information currently available in the literature, further studies are required to evaluate the effect of the NTAP application on self-etch (SE) adhesives or UAs applied in the SE mode.

The Antimicrobial Effect of Cold Atmospheric Plasma against Dental Pathogens-A Systematic Review of In-Vitro Studies

Interest in the application of cold atmospheric plasma (CAP) in the medical field has been increasing. Indications in dentistry are surface modifications and antimicrobial interventions. The antimicrobial effect of CAP is mainly attributed to the generation of reactive oxygen and reactive nitrogen species. The aim of this article is to systematically review the available evidence from in-vitro studies on the antimicrobial effect of CAP on dental pathogens. A database search was performed (PubMed, Embase, Scopus). Data concerning the device parameters, experimental set-ups and microbial cultivation were extracted. The quality of the studies was evaluated using a newly designed assessment tool. 55 studies were included (quality score 31-92%). The reduction factors varied strongly among the publications although clusters could be identified between groups of set pathogen, working gases, and treatment time intervals. A time-dependent increase of the antimicrobial effect was observed throughout the studies. CAP may be a promising alternative for antimicrobial treatment in a clinically feasible application time. The introduced standardized protocol is able to compare the outcome and quality of in-vitro studies. Further studies, including multi-species biofilm models, are needed to specify the application parameters of CAP before CAP should be tested in randomized clinical trials.

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.

Effect of different surface treatments on the bond strength of milled polyetheretherketone posts

STATEMENT OF PROBLEM

Polyetheretherketone (PEEK) can be used as a framework material for removable and fixed dental prostheses. However, information about the use of PEEK as a post-and-core restoration is scarce.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of different surface treatments on the push-out bond strength of milled polyetheretherketone posts to resin cement.

MATERIAL AND METHODS

Sixty intact human maxillary central incisors were selected and endodontically treated, and standardized post spaces were prepared. Sixty PEEK posts were milled from a prefabricated PEEK blank by using a computer-aided design and computer-aided manufacturing (CAD-CAM) system and divided into 3 groups (n=15) according to the surface treatment: acid etching by using 98% sulfuric acid (AE); airborne-particle abrasion by using 50-μm Al₂O₃ (AA); nonthermal plasma treatment (NTP); in addition, PEEK posts (n=15) received no treatment (NT) and served as a control. All posts were bonded by using a self-adhesive resin cement. Three sections (coronal, middle, and apical) were obtained for each specimen. Push-out bond strength measurements (MPa) for each section were recorded by using a universal testing machine at a crosshead speed of 0.5 mm/min until failure occurred. The post-cement interfaces and failure modes were evaluated by using scanning electron microscopy. The data obtained were statistically analyzed by using 1-way ANOVA and the pair-wise Tukey (HSD) test to study the difference between group mean values (α=.05).

RESULTS

The overall mean ±standard deviation of the push-out bond strength was 11 ±2 MPa for AE group, 6 ±1 MPa for AA group, 5 ±1 MPa for NTP group, and 3 ±1 MPa for NT group. A statistically significant difference was found among all groups subjected to different surface treatments as indicated by the ANOVA test (P<.001). The pair-wise Tukey honestly significant difference (HSD) test showed a significant difference among the AE group and all groups (P<.001); however, no significant difference was observed between the AA and NTP groups (P>.05). Moreover, a significant difference was observed among all root sections (P<.001).

CONCLUSIONS

Surface treatment of PEEK posts with 98% sulfuric acid for 60 seconds showed significantly higher bond strength values than those in other groups. The bond strength of PEEK posts to resin cement was significantly higher in the coronal section than that in other sections.

Atmospheric pressure plasma jet treatment enhances the effect of Alloy Primer on the bond strength between polymethyl methacrylate and stainless steels: application for retention of magnetic attachment to resin denture base

Magnetic attachment system is used to embed in polymethyl methacrylate (PMMA) resin denture base to improve denture stability. However, dislodgement of magnetic attachments from denture base is a major clinical problem. This study is to evaluate the bond strength between PMMA and stainless steel using metal primer and atmospheric pressure plasma jet (APPJ) treatment. Stainless steel discs were treated with Single Bond Universal Adhesive; Palfique Universal Bond; Alloy Primer; heat treatment with Alloy Primer; and 10-s, 20-s, and 30-s APPJ treatment with Alloy Primer. The shear bond strength between PMMA and surface-treated stainless steel was measured using universal testing machine. The effects of N₂ flow rate (60, 50, 40, 30 SLM), thermal cycling, and air quenching on shear bond strength were also investigated. The surface of each disc was examined using X-ray photoelectron spectroscopy and a goniometer. Finally, the temperature of plasma with various N₂ flow rates was measured and the optical emission spectra of the plasma were measured using spectrometer. Alloy Primer produced the highest bond strength. APPJ treatment was effective at enhancing bond strength by cleaning the surface of contaminants. Moreover, APPJ treatment with air quenching increased surface O^2-/OH- and Fe₂O₃/FeOOH ratios, reducing the negative influence of thermal cycling on bond strength. Alloy Primer with 20 s of APPJ treatment with a 50-SLM N₂ flow rate and air quenching was the most effective at increasing bond strength.

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.

Effect of Non-Thermal Atmospheric Pressure Plasma (NTP) and Zirconia Primer Treatment on Shear Bond Strength between Y-TZP and Resin Cement

The purpose of this study was to investigate the effect of non-thermal atmospheric pressure plasma (NTP) treatment on the sandblasting of mechanical method and zirconia primer of chemical method used to increase the bond strength between zirconia and resin cement. In this study, Y-TZP was divided into 4 groups according to the surface treatment methods as follows: Zirconia primer (Pr), NTP + Zirconia primer (NTP + Pr), Sandblasting + Zirconia primer (Sb + Pr), Sandblasting + NTP + Zirconia primer (Sb + NTP + Pr). Then, two types of resin cement (G-CEM LinkAce and Rely X-U200) were used to measure the shear bond strength (SBS) and they were divided into non-thermal cycling group and thermal cycling group for aging effect. Statistical analyses were performed using the Kruskal-Wallis test and Mann-Whitney U test. The result of the surface energy (SE), there was no significant difference among the groups (p > 0.05). As a result of the SBS test, the Sb + Pr group had a significantly higher SBS value than the other groups regardless of the resin cement type (p < 0.05), and the decrease rate after thermal cycling treatment was the lowest. On the other hand, the NTP + Pr group showed significantly lower SBS values than the other groups except for the case of using Rely X-U200 (p < 0.05), and the reduction rate after thermal cycling was the highest. The Sb + NTP + Pr group did not differ significantly from the Pr group (p > 0.05). Within the limitations of two successive studies, treatment with NTP after sandblasting used for mechanical bond strength showed a positive effect on initial SBS. However, when NTP was treated before the zirconia primer used for the chemical bond strength, it showed a negative effect on SBS compared to other treatment methods, which was noticeable after the thermal cycling treatment.

Enhanced Osteogenic Differentiation of Human Mesenchymal Stem Cells on Amine-Functionalized Titanium Using Humidified Ammonia Supplied Nonthermal Atmospheric Pressure Plasma

The surface molecular chemistry, such as amine functionality, of biomaterials plays a crucial role in the osteogenic activity of relevant cells and tissues during hard tissue regeneration. Here, we examined the possibilities of creating amine functionalities on the surface of titanium by using the nonthermal atmospheric pressure plasma jet (NTAPPJ) method with humidified ammonia, and the effects on human mesenchymal stem cell (hMSC) were investigated. Titanium samples were subjected to NTAPPJ treatments using nitrogen (N-P), air (A-P), or humidified ammonia (NA-P) as the plasma gas, while control (C-P) samples were not subjected to plasma treatment. After plasma exposure, all treatment groups showed increased hydrophilicity and had more attached cells than the C-P. Among the plasma-treated samples, the A-P and NA-P showed surface oxygen functionalities and exhibited greater cell proliferation than the C-P and N-P. The NA-P additionally showed surface amine-related functionalities and exhibited a higher level of alkaline phosphatase activity and osteocalcin expression than the other samples. The results can be explained by increases in fibronectin absorption and focal adhesion kinase gene expression on the NA-P samples. These findings suggest that NTAPPJ technology with humidified ammonia as a gas source has clinical potential for hard tissue generation.

Efficacy of cavity liners with/without atmospheric cold helium plasma jet for dentin remineralization

Aim: This study aimed to assess the efficacy of cavity liners with/without the atmospheric cold plasma jet (ACPJ) for dentin remineralization.

Effect of zirconia decontamination protocols on bond strength and surface wettability

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.

Metallization and Ar-O plasma effects on dental enamel roughness evaluated with SEM and MeX™ for 3D reconstruction

The MeX™ software is a useful tool for tridimensional data collection for surface evaluation and could be relevant to evaluate the same specimen in different phases of the study, assuming repeated measures of dental enamel roughness. The aim of this study was to evaluate the influence of sample metallization for dental enamel roughness analysis with 3D images reconstructed using MeX™ software from Scanning Electron Microscopy (SEM) images. The influence of 74.98% (%mol/mol) argon-oxygen plasma for carbon layer removal on surface roughness of the metallized specimen was also evaluated. Dental enamel specimens were prepared for SEM analysis with and without carbon metallization using conventional or environmental modes. Argon-oxygen plasma for carbon layer removal was used and surface roughness was re-evaluated. Roughness obtained by SEM and MeX™ reconstructed images, with or without metallization, did not differ. No significant alteration on surface roughness after carbon layer removal using plasma was found. SEM baseline evaluation using conventional mode without sample preparation and in environmental mode were not comparable. Roughness of enamel 3D images reconstructed with MeX™ software from SEM images, with or without metallization was similar. The 74.98% (%mol/mol) argon-oxygen plasma removed the carbon layer with no effect on enamel roughness.

Effects of non-thermal plasma treatment on the polysaccharide from Dendrobium nobile Lindl. And its immune activities in vitro

In order to improve the hydrophilicity and immune activity of the polysaccharide from Dendrobium nobile Lindl., non-thermal plasma was used to treat the polysaccharide. It was found that the hydrophilicity of the polysaccharide plasma-treated was significantly enhanced. Infrared spectra showed that the content of OH in the molecule increased significantly, and the monosaccharide ring changed from β-pyran sugar to β-furan sugar. The detection of SEM, AFM and TEM showed that the degree of cross-linking of surface molecules increased, and the arrangement of the polysaccharide was more compact and orderly. In vitro cell tests showed that the polysaccharide plasma-treated significantly improve the phagocytosis ability of RAW264.7, and promote the secretion of cytokines TNF-α, IL-6, IL-1. However, the cell proliferation test indicated that the polysaccharide did not increase the concentration of cytokines by promoting cell proliferation. RT-PCR showed that the polysaccharide plasma-treated could promote the expression of IL-1β at the transcriptional level. These results showed that non-thermal plasma treatment can effectively enhance the hydrophilicity of the polysaccharide and enhance its immune activity in vitro. Therefore, it can be inferred that the non-thermal plasma technology can be applied to the modification of active polysaccharides and will promote active polysaccharides to work better.

Influence of Non-Thermal Atmospheric Pressure Plasma Treatment on Shear Bond Strength between Y-TZP and Self-Adhesive Resin Cement

The purpose of this study was to evaluate the effect of non-thermal atmospheric pressure plasma (NTP) on shear bond strength (SBS) between yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and self-adhesive resin cement. For this study, surface energy (SE) was calculated with cube-shaped Y-TZP specimens, and SBS was measured on disc-shaped Y-TZP specimens bonded with G-CEM LinkAce or RelyX U200 resin cylinder. The Y-TZP specimens were classified into four groups according to the surface treatment as follows: Control (no surface treatment), NTP, Sb (Sandblasting), and Sb + NTP. The results showed that the SE was significantly higher in the NTP group than in the Control group (p < 0.05). For the SBS test, in non-thermocycling, the NTP group of both self-adhesive resin cements showed significantly higher SBS than the Control group (p < 0.05). However, regardless of the cement type in thermocycling, there was no significant increase in the SBS between the Control and NTP groups. Comparing the two cements, regardless of thermocycling, the NTP group of G-CEM LinkAce showed significantly higher SBS than that of RelyX U200 (p < 0.05). Our study suggests that NTP increases the SE. Furthermore, NTP increases the initial SBS, which is higher when using G-CEM LinkAce than when using RelyX U200.

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.