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Biomedical subjects

S Okawa

Publications and source records attributed to S Okawa.

At least 55 records · Page 3Linked to original sources
PubMed1981

[Studies on the dynamic durability of dental restorative materials. Part 4. Materials evaluation of initial and fatigue specimen for composite resins by acoustic emission method].

Present study is directed towards development for a method of materials evaluation of the static and dynamic properties for dental restorative materials and nondestructive inspection of the dental restorations in oral cavity by acoustic emission (AE) method. AE characteristics and deformation-fracture behavior of hour commercial composite resins under three points bending test are examined in order to evaluate initial and fatigue specimen for conventional and microfilled composite resins. Experimental results obtained are as follows: (1) Deformation-fracture behavior of conventional and microfilled composite resins exhibits different mode, corresponding to relatively brittle and ductile fracture behavior, respectively. Therefore, the primary sources of AE for conventional and microfilled composite resins under bending test are related mainly to the nucleation and propagation of cracks and plastic deformation, respectively. (2) In conventional composite resins under bending test, the burst type AE signal of higher amplitude and shorter decay time and more many AE total counts tend to be observed. In microfilled composite resins under bending test, the burst type AE signal of lower amplitude and longer decay time and more a few total counts tend to be observed. (3) Composite resins, particularly conventional composite resins under unload and repeated bending load are indicative of different AE characteristics. Accordingly, application of AE method for composite resins offers a method to evaluate the static and dynamic strength of composite resins. (4) In conventional composite resins under bending test, as characteristic AE are observed in a few stress regions before fracture, it may be possible to monitor nondestructively the restorations in oral cavity by using AE method.

Composite Resins↗
PubMed1980

[Studies on the dynamic durability of dental restorative materials. (Part 2) Properties for the repeated impact compressive load ot composite resins (author's transl)].

Based on the fracture energy form the compression test of composite resins under the repeated impact loads in compression after stored for a period in water at 37 degrees C, the dynamic durability of commercially used composite resins was evaluated. The results obtained were summarized as follows. (1) The fracture energy of composite resins under the repeated impact compressive loads after stored in water at 37 degrees C is clearly lower than the initial fracture energy. Particularly the decrement of the initial fracture energy for Concise, Epolite 100 and Superlux after stored for 30 days in water at 37 degrees C is influenced considerably both by the physicochemical degradation caused by water and the mechanical deterioration caused by the repeated impact compressive loads, but Clearfil is superior to the mechanical deterioration. (2) In each composite resins, there is a close correlation between fracture energy and compressive strain. In composite resins without Superlux, also a correlation is in fracture energy and compressive strength. (3) In clearfil, concise and Epolite 100, the morphology of fracture in compression test of composite resins which are subjected to and are subjected to the repeated impact loads in compression is classified in a mode of shear fracture, but in Superlux, a mode of crack fracture.

Composite Resins↗
PubMed1977

Use of rabbit antiboty IgG bound onto plain and aminoalkylsilyl glass surface for the enzyme-linked sandwich immunoassay.

Rabbit antibody IgG was bound onto aminoalkylsilyl or plain glass rods by simple adsorption. For comparison, rabbit antibody IgG was also bound onto glutaraldehyde-activated aminoalkylsilyl glass rods. These antibody-glass rods were tested by the sandwich procedure using Fab' fragments of rabbit antibody conjugated with beta-D-galactosidase from Escherichia coli. The glutaraldehyde-activated aminoalkylsilyl glass showed the largest capacity to bind antigen and the plain glass showed the smallest. However, the antibody-glass rods prepared by simple adsorption were as useful for the sandwich immunoassay of macromolecular antigens as those prepared with glutaraldehyde. With all the antibody-glass rods prepared, 0.1 to 10 fmol of ornithine delta-aminotransferase from rat liver and 2,4-dinitrophenyl human IgG were measurable. More than 10 fmol of the antigens may be measurable with larger amounts of the antibody-beta-D-galactosidase complexes, although the non-specific binding of the complexes to the solid phase increases to limit the sensitivity of the immunoassay.

Animals↗
PubMed1976

Enzyme-linked sandwich immunoassay of macromolecular antigens using the rabbit antibody-coupled glass rod as a solid phase.

A highly sensitive sandwich immunoassay of macromolecular antigens using the rabbit antibody Fab' - beta-D-galactosidase complex and the rabbit antibody immunoglobulin-G-coupled glass rod as a solid phase is described. The Fab' fragments of rabbit antibody IgG are conjugated with beta-D-galactosidase from Escherichia coli using N,N'-o-phenylenedimaleimide. Rabbit antibody IgG is coupled to the aminoalkylsilyl glass rods (3 mm in diameter and 5 mm in length) using glutaraldehyde. A wide range of the concentrations of rabbit IgG fraction (20-2000 mug/ml) is effective for coupling, and the amount of rabbit immunoglobulin G coupled can be controlled. The smallest amounts of ornithine delta-aminotransferase from rat liver, human immunoglobulin G and 2,4-dinitrophenyl human immunoglobulin G that can be determined are 0.03, 0.3 and 0.04 fmol, respectively. The sensitivity of the assay for these antigens is affected mainly by the non-specific binding of the complexes to the solid phase and the ability of antigen molecules, adsorbed on the solid phase, to bind specifically the complexes. The assay with the rabbit antibody immunoglobulin-G-coupled glass rods is simpler and more sensitive than that with the rabbit antibody immunoglobulin-G-coupled Sepharose 4B.

Adsorption↗
PubMed1976

[Slip casting of stainless steel powder (author's transl)].

Slip casting of stainless steel powder (AISI type 316 L) was investigated as means of forming medical and dental porous restorations. This research was undertaken to evaluate the effects of the particle size and aging of casting slip and firing conditions. Bulk density was used as a measure of the degree of sintering. Water contents of casting bodies decreased with the particle size and its casting rates, bulk densities and bending strengths increased. Aging of slip decreased casting rates, water contents and bending strengths of the casts. The bulk densities of the sintered stainless steel increased with sintering time and temperature. The porosities of the materials decreased with the particle size and the elevating temperature. The bending strengths of the materials increased sharply with the decreasing particle size. The optical micrographs did not always show the uniform elimination of pores in the sintered. Aging of slip increased a little the bulk densities of the materials and decreased the porosity and the bending strength.

Dental Casting Technique↗