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.

Poly(ethylene glycol)-poly(L-lactide) diblock and triblock copolymers were prepared by ring-opening polymerization of L-lactide with poly(ethylene glycol) methyl ether or with poly(ethylene glycol) in the presence of stannous octoate. Molecular weight, thermal properties, and crystalline structure of block copolymers were analyzed by 1 H-NMR, FTIR, GPC, DSC, and wide-angle X-ray diffraction (WAXD). The composition of the block copolymer was found to be comparable to those of the reactants. Each block of the PEG-PLLA copolymer was phase separated at room temperature, as determined by DSC and WAXD. For the asymmetric block copolymers, the crystallization of one block influenced much the crystalline structure of the other block that was chemically connected to it. Time-resolved WAXD analyses also showed the crystallization of the PLLA block became retarded due to the presence of the PEG block. According to the biodegradability test using the activated sludge, PEG-PLLA block copolymer degraded much faster than PLLA homopolymers of the same molecular weight.

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.

No abstract

No abstract