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This study investigated the effect of low-power, non-thermal atmospheric pressure plasma (NT-APP) treatments, in pulsed and conventional modes, on the adhesion of resin composite to dentin and on the durability of the bond between resin composite and dentin. A pencil-type NT-APP jet was applied in pulsed and conventional modes to acid-etched dentin. The microtensile bond strength (MTBS) of resin composite to dentin was evaluated at 24 h and after thermocycling in one control group (no plasma) and in two experimental groups (pulsed plasma and conventional plasma groups) using the Scotchbond Multi-Purpose Plus Adhesive System. Data were analyzed using two-factor repeated-measures anova and Weibull statistics. Fractured surfaces and the bonded interfaces were evaluated using a field-emission scanning electron microscope. Although there were no significant differences between the plasma treatment groups, the plasma treatment improved the MTBS compared with the control group. After thermocycling, the MTBS did not decrease in the control or conventional plasma group but increased in the pulsed plasma group. Thermocycling increased the Weibull moduli of plasma-treated groups. In conclusion, plasma treatment using NT-APP improved the adhesion of resin composite to dentin. Using a pulsed energy source, the energy delivered to the dentin was effectively reduced without any reduction in bond strength or durability.

This study investigated the effect of monomer deposition through a low-power, non-thermal atmospheric pressure plasma (NT-APP) on adhesion of resin composite to enamel and its durability. The adhesion of resin composite to enamel and its durability were compared using micro-shear bond strength (MSBS) tests, with or without monomer deposition and before or after thermocycling (TC). The bond strength data were interpreted using Weibull analysis. Hydrophilicities of treated ceramic surfaces were compared with contact angle measurements. Surface characterization was performed with a Fourier transform infra-red spectrophotometer and X-ray photoelectron spectroscopy. The fracture mode at the interface was evaluated using a stereomicroscope and a scanning electron microscope. The plasma polymer deposition of benzene and 1,3-butadiene using the low-power NT-APP improved the MSBS of resin composite to enamel (p

According to the types of dental ceramic, various surface treatment techniques have been tried for adhesive cementation, but each treatment has its shortcomings. A simple and universal surface treatment for intraoral and chair-side adhesion promotion is needed for resin cements. This study investigated whether hexamethyldisiloxane (HMDSO) and benzene, when deposited using a low-power non-thermal atmospheric pressure dielectric barrier discharge jet, were effective precursor monomers in dental ceramic adhesion. Their effect on adhesion was evaluated with shear bond strength test (SBS), contact angle measurement, X-ray photoelectron spectroscopy, and Fourier transform infra-red spectrophotometer in an attenuated total reflectance mode. The bonded interfaces and fractured surfaces were evaluated using a scanning electron microscope. Plasma polymerization of HMDSO resulted in formation of a siloxane network (Si2 peak), but its surface hydrophobicity hindered adhesive wetting. Additional deposition of benzene onto the HMDSO-coated ceramic surface increased the C1 peak, which partly corresponded to the C=C double bonds, and the hydrophilic peaks (C-O, C=O and O-C=O bonds). Benzene deposition itself improved the adhesion between the ceramic and the overlying adhesive through the chemical interaction of C=C double bonds and the increased hydrophilic groups. Additional deposition of HMDSO before benzene mediated the chemical adhesion of benzene to the ceramic surface and led to an additional increase of bond strength. Plasma polymerization of benzene and HMDSO/benzene increased the bond strength of composite resin to dental ceramic by improving wettability and adaptation with hydrophilic ether, carbonyl and ester groups, and chemical bonding with active species, such as C=C double bonds and silanol groups. Open image in new window

A pencil-type floating electrode dielectric barrier discharge (FE-DBD) jet was designed to improve adhesion of composite resin to dental ceramic by plasma deposition. Among various monomers used for plasma deposition, 1,3-butadiene (BD) merged as a promising monomer. Shear bond strength (SBS) and fracture modes were evaluated with specimens prepared at various flow rates of BD. The SBS values of the experimental groups were significantly higher than that of the negative control group and approached that of the positive control group when flow rate was higher than or equal to 2 sccm. Surface characterizations of plasma polymer-deposited ceramic surfaces were performed with FTIR-ATR and XPS. The deposited polymer on the ceramic surface contained methyl and methylene groups, ether and ester groups, and carbon–carbon double bonds. Formation of plasma deposited layer from BD was verified with TEM and EDS from specimens prepared using a focused ion beam technique. Adhesion between ceramic and composite resin was enhanced with BD plasma deposition using the FE-DBD jet. The adhesion effect was stemmed from chemical reactions between C=C double bonds remaining in the plasma deposited polymer and those in the adhesive monomers as well as increased wettability due to the ester and ether groups involved in deposited polymer.

Non-thermal atmospheric pressure plasmas (NT-APPs) have been shown to improve the bond strength of resin composites to demineralized dentin surfaces. Based on a wet-bonding philosophy, it is believed that a rewetting procedure is necessary after treatment with NT-APP because of its air-drying effect. This study investigated the effect of 'plasma-drying' on the bond strength of an etch-and-rinse adhesive to dentin by comparison with the wet-bonding technique. Dentin surfaces of human third molars were acid-etched and divided into four groups according to the adhesion procedure: wet bonding, plasma-drying, plasma-drying/rewetting, and dry bonding. In plasma treatment groups, the demineralized dentin surfaces were treated with a plasma plume generated using a pencil-type low-power plasma torch. After the adhesion procedures, resin composite/dentin-bonded specimens were subjected to a microtensile bond-strength test. The hybrid layer formation was characterized by micro-Raman spectroscopy and scanning electron microscopy. The plasma-drying group presented significantly higher bond strength than the wet-bonding and dry-bonding groups. Micro-Raman spectral analysis indicated that plasma-drying improved the penetration and polymerization efficacy of the adhesive. Plasma-drying could be a promising method to control the moisture of demineralized dentin surfaces and improve the penetration of adhesive and the mechanical property of the adhesive/dentin interface.

If plasma technology can come out of the vacuum chamber and plasma can be extruded through a small pencil-type torch, it can be applied widely to dental practices. For this study, we designed a small pencil-type non-thermal atmospheric-pressure glow discharge plasma torch. The purpose of this study was to determine the effect of plasma polymer coating on the adhesion of composite resin to feldspathic porcelain. The effect of plasma polymer coating was evaluated using shear bond strength (SBS) test. Contact angle measurements and fracture mode analysis were also performed. Among the groups treated with plasma polymer coating, the SBS of the adhesive (Adper Scotchbond Multi-Purpose, 3M ESPE) to the ceramic surface pre-treated sequentially with water plasma and triethyleneglycol dimethacrylate (TEGDMA) plasma in helium gas was significantly higher than that of the adhesive to the untreated surface (p < 0.05). In this group, the predominant fracture mode was mixed fracture, where small cohesively fractured fragments of ceramic were dispersed on the adhesively fractured flat adhesive surface. However, the SBS values of all the plasma polymer-coated groups were lower than those obtained through a routine porcelain bonding procedure with HF acid and silane coupling agent (p < 0.05). The non-thermal atmospheric-pressure plasma polymer coating technique was found to have a potential promoting adhesion to dental materials.

Contact angles of various monomers are measured by goniometer to calculate surface energies in order to select the monomer with highest surface energy. The highest surface energy is obtained with hexamethyl-disiloxane and is used in plasma coating the wood flour to improve its bonding and dispersion with the polypropylene (PP). The mechanical test results and SEM inspections indicate the good dispersion and the good compatibility between the wood flour and the PP. Also, this method is considered as a nontoxic process as compared to other chemical bonding method.

The direct hydroxylation of benzene using molecular oxygen by atmospheric pulse DC corona discharge was investigated. The conversion of benzene increased with the increase of oxygen content and input voltage but the selectivity of phenol decreased due to the formation of polymerized products. The reactivity was also influenced by the kind and content of background inert gas. By using argon as background gas, we could get 2.2% of phenol yield at 60°C and 1 atm with energy consumption of 50 W. The strategy of reductive oxidation, which added hydrogen to the reactant, was not favorable to the phenol formation in this reaction system. The polymerized product showed the oligomeric character and the analysis of its chemical structure with FT–IR was presented.

NOx conversion to N2 was investigated by a plasma/catalyst system in rich oxygen similar to a lean-burn engine exhaust. Catalytic activity was enhanced by the assistance of plasma, and the plasma/catalyst system showed higher NOx conversion over a wider temperature window than did catalyst alone. The plasma/catalyst (Ag/Al2O3) system showed a remarkable improvement in NOx conversion in the lower temperature range under 400 °C. The NOx conversion of plasma/catalyst (Ag/Al2O3) was 40%–50%, and its selectivity to N2 was over 96% under the conditions that the hydrocarbon (C1 base) to NOx ratio was about 3 and 10% O2 existed over the temperature range of 300–500 °C. Ag/Al2O3 showed a better performance than Al2O3 when assisted by plasma. Helium was used as a balance gas to measure N2 formation by gas chromatography, and NOx conversion was measured by a chemiluminescence NOx analyzer in N2 balance as well as He balance. The result in N2 balance gas was compared with the result in helium balance gas at the 300 °C where the largest enhancement by plasma was observed. The NOx conversion in N2 balance gas was similar to that in helium balance gas, which verified that the plasma effect obtained in helium balance gas is consistent with that of N2 balance gas, which is the largest component of the real exhaust gas.

PURPOSE: A plasma catalytic system is provided to efficiently remove NOx from exhaust gas discharged from a diesel engine by using a plasma reactor and a catalytic reactor. CONSTITUTION: A plasma catalytic system is comprised of a plasma reactor(11) supplied with DC pulse power and a catalytic reactor(12) filled with Ag and Al2O3. Exhaust gas generated from a diesel engine is treated by sequentially passing through the plasma reactor and the catalytic reactor. The plasma reactor consists of an anode and a cathode and supplies energy of 10-100J/L per unit flux of exhaust gas. The catalytic reactor is filled with a catalyst prepared by impregnating AgNO3 aqueous solution in gamma-Al2O3. The plasma reactor is operated in a normal pressure while the catalytic reactor is operated at 200-450deg.C of temperature. In the plasma reactor, NO in the exhaust gas is converted to NO2. In the catalytic reactor, NO2 is reduced to N2. Therefore, NOx in the exhaust gas is reduced.