Effects of plasma-induced grafting modification on the adhesive strength and mechanical properties of fiber posts.

OBJECTIVE: This study aimed to assess the effects of plasma grafting modification on the micro-push-out adhesive strength and mechanical properties of fiber posts and to assess the stability of these treatment effects. MATERIALS AND METHODS: Glass-fiber posts were divided into four groups based on the treatment methods used, as follows: (1) Group NT: no treatment; (2) Group PT: Helium (He) plasma treatment; (3) Group PIG: He-plasma-induced post-irradiation grafting; and (4) Group SIG: He-plasma-induced syn-irradiation grafting. The treated fiber posts were bonded using self-adhesive resin cement exposure to air for 0, 1, 6 or 12 hours separately after surface treatment. Micro-push-out adhesive strength, flexural modulus, and flexural strength were measured. RESULTS: Plasma treatment, post-irradiation grafting, and syn-irradiation grafting improved adhesive strength at the 0-hours level. However, the improved adhesive strength disappeared in group PT after exposure for one or more hours. In group PIG, the adhesive strength after 1-hour exposure was 20.5% lower than that of 0-hour exposure (adhesive immediately after treatment), and no statistically significant differences in adhesive strength were observed between the 1, 6, and 12-hour exposure. In group SIG, no statistically significant differences in adhesive strength were observed among the 0, 1, and 6-hour exposure. Although the adhesive strength was 23% lower at the 12-hour exposure than that of 0-hour exposure in group SIG, the adhesive strength of fiber posts received syn-irradiation grafting still presented the best adhesive strength compared with the other treatment methods. The three-point flexural modulus and strength remained unaffected by the treatment methods used. CONCLUSIONS: Plasma-induced syn-irradiation grafting provided the ideal improvement and stability in adhesive strength in fiber posts. In addition, plasma-induced grafting modification successfully overcame the surface aging effect caused by plasma treatment alone without affecting the bulk mechanical properties of fiber posts.

[Dentin barrier cytotoxicity test with three-dimensional cell cultures].

OBJECTIVE: To evaluate the cytotoxicity of four dentin filling materials and two dentin adhesives with a dentin barrier test and to compare the results with those in a conventional filter diffusion test in order to investigate the advantages of the dentin barrier test. METHODS: Eugenol cement, zinc phosphate cement, adhesive glass ionomer cement, composite resin and two self-etching adhesives (REMI BOND and Adper Easy One) were tested. In the dentin barrier test, L929 mouse fibroblasts were three-dimensional cultured in polystyrene meshes. The dentin disks were cut from the human third molars, near the pulp and in parallel with the occlusal surface, and their permeability within the measurement area was evaluated by a hydraulic permeability device. A mesh with the cells was placed in the "pulp cavity" of the chamber and one dentin disk was put on the cell mesh and its "pulp side" was in contact with the mesh. The test materials and controls were in contact with the "occlusal side" of the dentine disks for 24 h. The cell viability was obtained with MTT assay and the results were expressed as a percentage of control tissues. The Mann-Whitney U test was used to make the statistical analyses. In the filter diffusion test, after a 24 h contact between the test materials and the filters with monolayer cells, the filters were dyed and the grades of cytotoxicity were decided. RESULTS: A mean permeability of the dentin disks near the pulp was 0.293 µL/(min×cm(2)×cmH(2)O)(1 cmH(2)O=0.098 kPa); In the dentin barrier test, Eugenol cement, REMI BOND and Adper Easy One respectively reduced the cell survival rates to 82%, 63% and 54%. Other materials showed no or very low toxic reactions; In the filter diffusion test, the light-curing composite resin was moderately cytotoxic, the dental adhesive glass ionomer cement was mildly cytotoxic and the others were severely cytotoxic; All the six materials in the dentin barrier test had lower cytotoxicity than in the filter diffusion test. CONCLUSION: The cytotoxicity of the test materials using the dentin barrier test with three-dimensional cell cultures is lower than that in the filter diffusion test, which has good correlation with the clinical situation.

A comparative study of the H + FO (v = 0, j = 0) --> (OH + F)/(HF + O) reaction from QM and QCT methods.

The dynamics of the title reaction are investigated using both the time-dependent quantum wave packet and the quasi-classical trajectory methods and employing a recently developed adiabatic ground 1(3)A'' potential energy surface [Gomez-Carrasco et al. J. Chem. Phys. 2004, 121, 4605]. By comparison to the quantum J = 0 reaction probabilities, the QCT method is first validated for the title reaction and further employed to produce the integral cross sections and rate constants. No resonance structures have been observed in both the QCT J = 0 and the quantum reaction probabilities of OH + F as well as in the QCT integral cross sections of both product channels, while there are some undulations in the calculated quantum reaction probabilities of HF + O. It is also found that Coriolis coupling effects play a significant role in the quantum calculation and that formation of the OH product is favored over the HF product in the reactive system.

Nocardiosis in large yellow croaker, Larimichthys crocea (Richardson).

An epizootic in seawater-cage reared large yellow croaker, Larimichthys crocea, in China was caused by a Nocardia sp. from August to October 2003. The cumulative mortality rate was 15% and the diseased fish were 16 months old with individual length varying from 25 to 30 cm. Multiple, white nodules, 0.1-0.2 cm in diameter, were scattered on the heart, spleen and kidney. The morphology of isolated bacteria from Lowenstein-Jensen medium and tryptic soy agar was bead-like or long, slender, filamentous rods. Experimental infection indicated that the isolated bacterium was the pathogen responsible for the mortalities. A partial sequence of the 16S rRNA gene of the organism and the type strain of Nocardia seriolae JCM 3360T (Z36925) formed a monophyletic clade with a high sequence similarity of 99.9%. Based on the morphological, physiological, biological properties and the phylogenetic analysis, the pathogenic organism was identified as N. seriolae. This is the first report on N. seriolae-infected large yellow croaker in aquaculture.