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Biomedical subjects

D Welker

Publications and source records attributed to D Welker.

At least 55 records · Page 3Linked to original sources

Morphogenesis of cell-to-substratum adhesion and spreading on Ni-Cr-alloys. A scanning electron microscopic study.

A scanning electron microscopy (SEM) analysis has been performed on the adhesion, spreading and growth pattern of fibroblastoid and epitheloid cells on Ni-Cr-alloys as compared to glass substrates. The attachment is initiated by filipodial contact of monolayer cells with the glass as well as alloys, and subsequent radial spreading occurs by the gradual peripheral extension of the broad lamellipodium followed by a general cell flattening. When cultured under identical conditions monolayer cells reach confluence at the same time on glass and alloy surfaces, respectively. The results show that the fibroblastoid and epitheloid cells form stable contacts between the cell surface and the alloy in the same manner in which the cells adhere to the surface of glass. The cells migrated and proliferated on the surface of alloys and covered the surface of the substratum.

Animals↗

Toxicity evaluation of water soluble substances of dental materials by means of cell population in vitro.

The paper describes a method of evaluation of the biocompatibility of dental restorative materials with a monolayer cell culture system. Semisolid and solid materials were eluted under physiological conditions. The cell monolayer was exposed to the eluates. The method enables the recognition of toxic ingredients and thus their elimination by the producer of these materials as well as the comparison of the cytotoxicity of newly developed materials with conventional ones.

Animals↗

[Studies on the influence of mixing ratio and manual or mechanical mixinng ratio and manual or mechanical mixing on physical properties of composites (author's transl)].

The study was carried out in order to see whether the physical properties (microhardness, cone-flow-point, compressive strength, abrasion resistance, density, dimensional change adherence to enamel) of the powder-liquid- composite are dependent upon the processing conditions (powder-liquid-ratio, manual or mechanical mixing). We found that the higher the powder-liquid-ratio the higher the microhardness, compressive strength, density and the least the volume contraction. The abrasion resistance and the adherence to enamel depended not significantly upon the mixing ratio. In a manual mixed composite the highest cone-flow-point has been found to lie between a high and a low powder-liquid-ratio. All this findings show clearly that a standardized powder-liquid-ratio is a necessary prerequisite to an optimal quality of the composite. This optimal ratio can be guaranteed by a proper predosage in capsules. Mechanical mixing increased the microhardness, cone-flow-point, compressive strength and density. This fact is due to homogenity and small porosity. Mechanical mixed and injection-capsule composites are recommendable.

Biomechanical Phenomena↗

[Composite porosity depending on the powder-fluid quotient, the mixing process and the methods of application].

Porosity (number of pores, pore size distribution, relative area of pores) of powder/liquid composite depended on processing conditions (powder/liquid ratio, manual or mechanical mixing, method of application). The minimum number of pores and the least relative area of all pores in a cross-section of the sample was found in the mechanically mixed composite. Injection-capsule composites are recommended. Application in small portions should be avoided. The higher the powder/liquid ratio the higher the number of pores and relative area of pores. The ratio of components and the method of application have a different effect on the pore size distribution.

Chemical Phenomena↗