Research progress on the methods of observation and analysis of dental bonding interfaces / 口腔疾病防治

@#Dental bonding technology and materials have been used widely in dentistry because of their excellent properties. The development of novel bonding technology and materials is constantly being performed to improve the effect of dental bonding restorations. Observation and analysis of the dental bonding interface is one of the most important methods for laboratory evaluation of bonding efficiency. This paper aims to review the methods of observation and analysis of dental bonding interfaces to provide a reference for the selection of evaluation methods in dental bonding research. The features of 6 methods, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM), Raman spectroscopy (RS), optical coherence tomography (OCT) and atomic force microscopy (AFM), were described and summarized. Among these methods, SEM and TEM are used most often in the analysis of fine structures; CLSM and OCT are used for the acquisition of characteristic image signals, such as microleakage and exogenous and endogenous fluorescence; and RS and AFM can test chemical composition and mechanical properties.

Effect of fungicide on Fusarium verticillioides mycelial morphology and fumonisin B1 production

The effect of fludioxonil + metalaxyl-M on the mycelial morphology, sporulation and fumonisin B1 production by Fusarium verticillioides 103 F was evaluated. Scanning electron microscopy analysis showed that the fungicide caused inhibition of hyphal growth and defects on hyphae morphology such as cell wall disruption, withered hyphae, and excessive septation. In addition, extracellular material around the hyphae was rarely observed in the presence of fludioxonil + metalaxyl-M. While promoting the reduction of mycelial growth, the fungicide increased sporulation of F. verticillioides compared to the control, and the highest production occurred on the 14th day in the treatments and on the 10th day in the control cultures. Fumonisin B1 production in the culture media containing the fungicide (treatment) was detected from the 7th day incubation, whereas in cultures without fungicide (control) it was detected on the 10th day. The highest fumonisin B1 production occurred on the 14th day, both for the control and for the treatment. Fludioxonil + metalaxyl - M can interfere in F. verticillioides mycelial morphology and sporulation and increase fumonisin B1 levels. These data indicate the importance of understanding the effects of fungicide to minimize the occurrence of toxigenic fungi and fumonisins.

Culture-Independent Analysis of Bacterial Community Composition during Bioremediation of Crude Oil-Polluted Soil.

Aim: To use cultivation-independent techniques based on DGGE of PCR-amplified 16S rRNA gene and to evaluate bacterial community composition during bioremediation of crude oil-polluted soil. Study Design: Molecular fingerprints of bacterial populations involved in the active phase of crude oil biodegradation were generated with DGGE after 16S rRNA gene amplification. Place and Duration of Study: Department of Microbiology and Plant Pathology, University of Pretoria, South Africa, between March and August 2008. Methodology: Crude oil-degrading bacteria in soil microcosms contaminated with 4% crude oil and then biostimulated with nitrogen-phosphorus-potassium inorganic fertilizer (NPK: designated PN soil), calcium ammonium nitrate (designated PU soil) and poultry droppings (designated PP soil) respectively were characterized with PCR of the gene for the small subunit (SSU) of the bacterial ribosome. Total culturable heterotrophic and hydrocarbon utilizing bacteria were enumerated using plate count and Bushnell Haas media. Total organic carbon content was measured throughout the study period to indirectly determine the effect of microbial activity on carbon content in biostimulated treatments as against controls. Gas chromatography was used to monitor hydrocarbon degradation with time while electron microscopy examined community richness during hydrocarbon degradation. Reamplified dominant DGGE bands (550bp) were cleaned up and sequenced using an ABI 3130XL genetic analyzer. Electropherograms were inspected with Chromas Lite 2.01. Sequence identification was performed using BLAST. Results: Dendogram of the DGGE bands constructed using Jaccard coefficient algorithm revealed that communities from PU and PP-amended soils each formed distinct clades whereas PN treated soil showed less association when compared with PU and PP respectively. Fifty distinct bands were excised, reamplified by PCR and sequenced. Sequence analysis revealed the presence of phylogenetically distinct known hydrocarbon degrading bacteria like Corynebacterium spp., Dietzia spp., Janibacter sp. low G+C Gram positive bacterial clones Nocardioides spp., Rhodococcus erythropolis and uncultured bacterial clones. Forty successful sequence data obtained from the excised DGGE bands were submitted to GenBank database under accession numbers GU451069 to GU451108. Chromatograms of the residual hydrocarbons in test treatments and controls showed that biodegradation occurred markedly in treated soils in this order PN>PU>PP while no significant loss was observed in the oil-contaminated control on days zero and 42 respectively. Bacterial counts increased significantly in PN, PU and PP treatments and not in controls PC and OC. Total organic carbon increased appreciably in PN, PU and PP respectively from day zero to day 28. Electron micrographs of microbial consortia in the nutrient-amended soils revealed presence of active populations induced by biostimulation as against the sparsely populated controls. Conclusion: The results suggest that nutrient amendment stimulates and selects indigenous soil bacteria that are able to degrade petroleum hydrocarbons.