Biomedical subjects
Publications and source records attributed to E Kawada.
A 60 year-old Japanese man having a 20-year history of diabetes mellitus presented with truncal neuropathy. The severe pain, especially its nocturnal exacerbation, prevented him from sleeping and eating, resulting in rapid emaciation. However, he recovered from the condition with oral mexiletine, which dramatically controlled the pain.
In this study, the authors have attempted to discover optimum conditions for eliminating all porosity, except what is caused by manual error, in the surfaces of Die Stone. Five vinyl-porisiloxane impression materials, two other kinds rubber impression materials, and two kinds of die materials were used. Die materials were poured at intervals of 0, 15, 30, 60, and 120 minutes after the impression had been removed. Cast-surface porosity was measured by means of SPICCA II. Results 1. Practically surface porosities were not scarcely observed in casts made from any of the impression materials except vinyl silicone rubber. Among the five vinyl-polysiloxane impression materials, Hydrophilic Exaflex produced the least porosity. 2. Porosity in casts made with Provil tended to decrease definitely as pouring time progressed. This tendency occurred with no other materials. 3. When the die material was mixed at a low water-powder ratio, cast-surface porosity was reduced in the case of all materials except President. 4. Concentration of hydrogen gas, which was released from all vinyl-polysiloxane impression materials, decreased with the passing of time. 5. In the case of Provil, a correlation existed between hydrogen-gas concentration and the degree of cast-surface porosity. But no similar correlation was observed in the case of any other vinyl-polysiloxane impression materials.
In this study, the author attempted to find out the suitable methods of surface treatments for non-precious metal-ceramics alloys. Three Ni-Cr system alloys in the market, (Gemini II, Euro-ceram and Wiron S) were used. The shear bond strength was measured under the various conditions, varying the heating temperatures of pre-oxidation treatment and finishing methods of the metal surface. A specially designed apparatus which had been improved by the author, was used to measure the shear bod strength of the metal-ceramics. The following results were obtained. 1. The testing method improved was found better as a means of measuring the bond strength. Because the shear bond strength which was obtained by this testing method was hardly affected by the compressive force originating from porcelain contraction or the strength of alloys. 2. In the case of Gemini II and Euro-ceram, the influence of the finishing treatment on the properties was great. The coarser the surface roughness, the greater the value of the shear bond strength. 3. In the case of Wiron S, the influence of the pre-oxidation treatment was great. The higher the temperature of treatment, the greater the value of shear bond strength. 4. The optimum surface treatment of metal was obtained among three alloys respectively. The shear bond strength of Gemini II was greater than the others under any condition. In the case of Euro-ceram, the highest bond strength was obtained under the coarser surface condition regardless of the temperature of pre-oxidation treatment. In the case of Wiron S, the highest bond strength was obtained by the surface which was finished by the #600 emerypaper and the higher temperature of pre-oxidation treatment.
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PURPOSE: The aim of this study was to measure the flexural strength and the elastic modulus of composite resin with and without reinforcing fibers and to evaluate the reinforcing effect of various fibers. MATERIALS AND METHODS: A polyethylene fiber (Ribbond), a polyaramid fiber (Fibreflex), and three glass fibers (FibreKor, GlasSpan, Vectris) were used to reinforce composite resins. The flexural strength and elastic modulus of specimens in the three-point bending mode were measured using a universal testing machine at a cross-head speed of 1 mm/min after storage in water at 37 degrees C for 24 hours. All tests were carried out in a water bath at 37 degrees C. The data were analyzed using analysis of variance and the Sheffé test at P= 0.05. After testing, the fractured surface was evaluated using a scanning electron microscope at 50x, 500x, and 3,000x magnifications. RESULTS: Yield flexural strengths of nonreinforced resins were 48 to 56 MPa, and those of reinforced resins were 56 to 134 MPa. Ultimate flexural strengths of nonreinforced specimens were 96 to 119 MPa, and those of reinforced ones were 203 to 386 MPa. Elastic modulus of nonreinforced resin was 6 to 9 GPa, and fiber reinforcing increased the value to 9 to 15 GPa, while it had no effect in Ribbond. CONCLUSION: Most of the fibers used in this study increased both yield and ultimate flexural strengths of composite resins, with the exception of the yield strength of Vectris. GlasSpan, Fibreflex, and FibreKor were effective in reinforcing elastic modulus, while Ribbond had no effect on it. Unidirectional glass fibers and polyaramid fiber were effective in reinforcing both flexural strength and elastic modulus of composite resin.