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Biomedical subjects

E Masuhara

Publications and source records attributed to E Masuhara.

At least 37 records · Page 2Linked to original sources
PubMed1978

[Solubility and degree of hemolysis as methods for the in vitro evaluation of dental filling materials].

For the biological examination of dental resin filling materials, a solubility and hemolysis test is recommended as an in-vitro testing method. Solubility and degree of hemolysis were examined in various filling materials based on MMA and BIS-GMA. It was found that, at the beginning, solubility was considerably higher in MMA-containing materials than in the BIS-GMA systems, and that after a while the conditions were reversed. The degree of hemolysis decreased in the following order with the individual materials: 1. Posite, Sevriton, Adatpic, 2. Epoxylite, Smile, Palakav, 3. MMA-BPO/Amin and MMA-TBBO. Comparison between the MMA and BIS-GMA monomers showed that corresponding to the same molar amounts, BIS-GMA materials developed a higher degree of hemolysis.

Dental Materials↗
PubMed1978

[Polymerization shrinkage and fitness of denture (author's transl)].

Polymerization shrinkage causes dimensional change of denture during the processing. We can not control the amount of shrinkage but can control the initiation points and the direction of polymerization. Heat conductivities of dough and mould, the distance from heating or cooling place, and amount of MMA etc. have influence on the polymerization. Polymerization shrinkage mainly appears on the point where polymerize last. In the case of heat processing the shrinkage mainly appeared on the point where heat supply was slow. On the other hand in that of self-curing resin, the polymerization starts at the center of the mass when the mould is immersed in an ice water bath and the shrinkage appeared on the surface of mass. Dentures were prepared by heat processing resin conventionally heated in a water bath, heated from mucous side only on a heat plate, and self-curing fluid resin. An amount of filled light body silicone impression materials between the denture and cast was minimum in the case of the one side heat processed denture. That was middle in the self-cured. The maximum case was conventional heat cured denture.

Composite Resins↗
PubMed1978

[Preparation of clear thermosetting resin for veneered crown from several bisMEPP monomers (author's transl)].

The whitish translucent shade of a thermosetting resin cured from a mixture of a 2,2-Bis (p-methacryloxy (ethoxy)1-2 phenyl)-propane monomer and PMMA pearls makes it difficult to reconstruct a shade of the natural tooth. The attempt to improve the transparency of the mixed polymer was made in this study. Varying the molecular weight of BisMEPP monomer, PMMA polymer and curing temperature, cured specimens were prepared and their transparency was measured with a spectrophotometer. The results obtained are as follows. 1) In any molecular weight of PMMA, BisMEPP with 2.3 to 3.3 average number of ethylene oxide linkage showed the highest transpalency on the specimen. 2) With increasing the curing temperature, transpalency of the specimens made from BisME4.0 PP increased. With another molecular of BisMEPP, transpalency of the cured specimens showed the highest transpalency at the curing temperature of 120 degrees C. 3) With increasing the molecular weight of PMMA, the transpalency increased.

Acrylates↗
PubMed1978

[Studies on dental self-curing resins. (17). Adhesion of PMMA with bovine enamel or dental alloys (author's transl)].

We synthesized 4-methacryloxyethyl trimellite acid (4-MET) and anhydride (4-META), and tried them as a reactive comonomer for adhesives to bovine enamel. In the case of non-etched enamel, tensile adhesive strength was 40-50 Kg/cm2 after one day immersion in 37 degrees C water, but it decreased below 10 Kg/cm2 after a month immersion in 37 degrees C water. It could be concluded that this adhesion was not sufficient for practical usage. Then we applied this method to an etched enamel. After a series of experiments we concluded that it was necessary to etch bovine enamel surface with 30% citric acid for practical usage. Adhesion of some dental alloys with a PMMA rod was also studied and adhesive strength in Co-Cr alloy was over 150 Kg/cm2 either after one month immersion in 37 degrees C water or 60 times thermal cycles between 4 degrees C and 60 degrees C.

Adhesiveness↗
PubMed1978

[Effect of cross-linking agents on mechanical properties of a fluid resin (author's transl)].

Effect of several cross-linking agents added to MMA on the mechanical properties of self-cured fluid resins was studied. The cross-linking agents were 2,2-bis (4-methacryloxyethoxyphenyl) propane, trimethylolpropane trimethacrylate, neopentylglycol dimethacrylate, hexamethyleneglycol dimethacrylate and 1,2-polybutadiene. Their concentrations in MMA were 1,3,5 and 10 wt%. Measured mechanical properties were Brinell hardness, tensile strength, impact strength and transverse strength. The best composition was 5% neopentylglycol dimethacrylate in MMA among studied samples. Microscopic observation of the surface after tensile test suggested that diffusibility of cross-linking agents into PMMA powder affected the mechanical properties. Mechanical properties of both matrix and powder, and their adhesion at the interface had influence upon the mechanical properties of resins processed by powder-liquid method.

Acrylates↗
PubMed1978

Evaluation of polysulfone as a potential biomedical material.

In the course of preliminary screening of various potential biomaterials, polysulfone (PS) has been found to have good biocompatibility (1,2). This paper describes the detailed results of evaluation of PS by several methods. Although a number of screening programs for biomaterials have been published (3,4,5,6,), we used our own program in this experiment.

Animals↗
PubMed1977

Studies on dental self-curing resins. XV. Application of nitrene to reactive adhesive with a tooth.

Effectiveness of p-azidobenzoyloxyethyl methacrylate on the adhesion of a tooth was studied. This methacrylate, dissolved in suitable monomer solvents such as 2-hydroxyethyl methacrylate, was painted on ivory- or acid-etched enamel and the surface was irradiated by ultraviolet light. Photolysis of the azide produced a nitrene which was reactive with polypeptides in the tooth. As the treated surface must have affinity with methyl methacrylate (MMA) and pol(methyl methacrylate) (PMMA), it was joined with a PMMA bar by the self-curing resin. The adhesive strength was 100 kg/cm2 with ivory or 65 kg/cm2 with enamel. Graft copolymerization of methyl methacrylate onto collagen may take place by the nitrene prepared in situ by photolysis of the azide. Subject to satisfactory biologic evaluation, this coupler may be useful in the development of adhesive dental filling materials and fissure sealants.

Animals↗
PubMed1976

[On the polymerization of pour type resin (author's transl)].

The initial polymerization point and the polymerization progress have been observed on powder-liquid pour type acrylic resin and one-liquid pour type acrylic resin. The results are as follows: 1. In case of un-heating at the bottom of powder liquid resin, in the former stage the polymerization makes the regular progress from the bottom part to the upper of the mould, but in the latter stage it does some irregular one. In case of heating at the bottom, at first it shows a better regular progress as in the case of un-heating. 2. In case of un-heating at the bottom of one-liquid resin, in the first stage the polymerization makes the regular progress from the bottom part of the resin and at the same time from its middle of the mould, and then to the upper part and the sprue part. In case of heating at the bottom, it begins just from the heated part, then it goes quite regularly to the middle, the upper, and the sprue part, and lastly the polymerization shrinkage concentrates exclusively at the sprue part.

Acrylic Resins↗