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Volume 8 (1989)
- Issue 2 Pages 129-
- Issue 1 Pages 1-
Volume 8, Issue 1
Displaying 1-12 of 12 articles from this issue
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Adhesive Ability of Dental Adhesive Resin to the Cleaned Metal Surface Obtained by Hydrogen Gas Reduction MethodHiroki OHNO, Yoshima ARAKI, Kazuhiko ENDO, Isao KAWASHIMA1989 Volume 8 Issue 1 Pages 1-8,121
Published: June 25, 1989
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSWith the cleaned metal surface without passive film or an oxide layer, chromium, cobalt, and iron show excellent bonding strength, indicating values similar to 18-8 stainless steel. Therefore the existence of a passive film and oxide layer at the interface metal/resin is not essential for metal-resin bonding. The adhesive ability decreases in the order:
Cr≅Co≅Fe>Cu>Ag>Au≅Ni>Pt>Pd.View full abstractDownload PDF (1142K) -
Kenzo ASAOKA, John A. TESK1989 Volume 8 Issue 1 Pages 9-25,121
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe development of either transient or residual stress in a slab of dental porcelain during cooling was simulated by use of a super-computer. The temperature dependences of the elastic modulus, the thermal expansion coefficient, and the shear viscosity, and the cooling rate dependence of the glass transition temperature, Tg, were considered in this calculation.Internal stress and viscoelastic creep were computed for several cooling rates. Calculated results display stress profiles which agree reasonably well with reported measured profiles in quenched, tempered glasses. The calculated residual surface stress, σ, could be fit by the following empirical formula, σ=kl2(q/q0)n, q is the cooling rate, q0 is a reference cooling rate and l is the half-thickness of the porcelain. The method by which residual stress develops is also discussed. This discussion suggests a method for strengthening of the porcelain by the development of high-compressive residual stress on the surface.View full abstractDownload PDF (1774K) -
Masayuki TAIRA, Kunio WAKASA, Masao YAMAKI, Akira MATSUI1989 Volume 8 Issue 1 Pages 26-34,122
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSWe examined the effects of air pressure on the free-running speed of air-bearing and torque-type ball-bearing air-turbine handpieces. The air pressure for the former should be kept at a certain high level to maintain the stable super-thin air-bearing film and to provide the quasi-constant speed of around 420, 000 to 480, 000rpm. On the other hand, the air pressure for the latter could be adjusted to provide some varieties of speeds, ranging from about 150, 000 to 320, 000rpm. Subsequently, to compare the torque properties and cutting effectiveness between these two handpieces, weight-load cutting tests were conducted, using a glass-ceramic workpiece and a commercial diamond point. It was confirmed that the air-bearing handpiece had the lower torque power but exhibited better cutting effectiveness, compared with its counterpart.View full abstractDownload PDF (3034K) -
I. Viscoelastic Properties of Homopolymer/Plasticizer MixtureNaoyuki KATAKURA, Makoto HOSOTANI, Kazunori IIJIMA, Hisao HONMA, Midor ...1989 Volume 8 Issue 1 Pages 35-39,122
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe viscoelastic properties of new experimental tissue conditioners which consist of synthesized poly (butyl methacrylate) PBMA and a liquid of aromatic-ester plasticizer, without alcohol, were investigated to evaluate the effects of the molecular weight of polymer. The master curves of storage modulus G', dynamic viscosity η' and loss tangent tan δ were constructed from the viscoelastic data at different temperatures. The effects of the molecular weight of polymer on the viscoelastic properties G' and tan δ were observed particularly, in a low frequency range. However, the dynamic viscosity η' was not very sensitive to the molecular weight. These results suggest that PBMA produces more desirable properties for tissue conditioners, and that it is possible to manufacture new materials without alcohol.View full abstractDownload PDF (1815K) -
Minoru KAWAGUCHI, Tadao FUKUSHIMA, Takashi HORIBE1989 Volume 8 Issue 1 Pages 40-45,122
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe effects of monomer structure on the mechanical properties of visible light-cured composite resins based on the seven types of aromatic dimethacrylates were investigated. The results of this study suggested that the mechanical properties of the composite resins were dependent upon the chemical structure of the dimethacrylate monomers employed. The composites based on dimethacrylates with hydroxy groups showed a relatively significant decrease in flexural strength, elastic modulus, and compressive proportional limit under wet conditions. The segmental mobility of dimethacrylate monomers considerably influenced the nature of cured composites. Bis-GMA-F-based composite showed superior mechanical properties to a conventional Bis-GMA-based material. The SEM observation of fractured surfaces revealed that failure mainly occurred through the resin matrix of the composite resins.View full abstractDownload PDF (3160K) -
(Part 1) Electrochemical StudyKazuhiko ENDO, Yoshima ARAKI, Hiroki OHNO1989 Volume 8 Issue 1 Pages 46-55,123
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe corrosion behavior of three silver-based alloys, Ag-Sn-Zn, Ag-In, and Ag-Pd-Cu, were investigated by potentiodynamic anodic polarization analysis and the polarization resistance method in 0.1% Na2S and Ringer's solutions.
The corrosion activity of the Ag-Sn-Zn alloy was higher in Ringer's solution than in the 0.1% Na2S solution. In contrast, the corrosion rate of the Ag-Pd-Cu alloy was approximately 500 times higher in the 0.1% Na2S solution than in Ringer's solution. The results show that the generally accepted concept that tranish is merely a surface discoloration due to the deposition of insoluble products is inadequate. The alloy discolors while being severely attacked in the presence of sulfides. For the Ag-In alloy, the corrosion activity in the 0.1% Na2S solution was as high as in Ringer's solution.
These silver-based alloys exhibit different electrochemical activities in different solutions. The test solutions for corrosion tests must be carefully chosen for each alloy system through a screening test to replicate the predominant corrosion reaction proceeding in the oral environment.View full abstractDownload PDF (1497K) -
Part 2. Effects of Clasp Design in Unilateral Free-end DentureMasao MORIKAWA, Shinichi MASUMI, Hirofumi KIDO, Shizuo TOYODA, Yoshio ...1989 Volume 8 Issue 1 Pages 56-64,123
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe three-dimensional dymanic movement of the abutment tooth was successfully analyzed on a simulation model utilizing the mandibular kinesiograph. When the unilateral free-end denture retained by the RPA, RPI or Aker's clasp was subjected to various directions of loads, the abutment tooth was inclined mainly by the sliding displacement of the denture over the alveolar ridge and the lever action around the denture. The Aker's clasp assembly induced the largest tooth movement. The RPA clasp generally exhibited similar tendencies to the Aker's clasp, showing a larger tooth inclination in the disto-buccal direction. The RPI clasp seemed to be preferable for protecting the periodontal tissues from damage associated with unfavorable tooth movements since it induced less distal tooth inclination.View full abstractDownload PDF (1358K) -
Hideo OGURA, Yukio MIYAGAWA, Kengo NAKAMURA1989 Volume 8 Issue 1 Pages 65-75,123
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe bending creep of six different dental amalgams was continuously measured up to 30 days under different static loads. All six amalgams induced creep rupture within 30 days under 9kgf of static load and some of them did under the lower static load. The high copper amalgams resisted for a longer period of time compared to the low copper amalgams. The admixed high copper amalgam had the highest creep value at rupture under the same load, which indicates that this amalgam is more flexible under continuous loading than the other amalgams. The rupture time was approximately proportional to the reciprocal of the creep rates and the rupture time drastically increased as the creep rate decreased. This result basically explains and supports the previously reported correlation between the compressive creep during a specific period of time and the marginal fracture of amalgam restorations.View full abstractDownload PDF (3505K) -
Mikio CHIBA, Kazuo ITOH, Sadao WAKUMOTO1989 Volume 8 Issue 1 Pages 76-85,124
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe relation between the bonding efficacy of the dentin adhesive and the physical change of the dentin after treatment with various dentin cleansers was investigated.
The dentin surface was cleaned with one of the seven experimental dentin cleansers, 5, 10, 20, 30 and 40% of the phosphoric acid, neutralized 0.5M EDTA solution (pH7.4) and 9.1% pyruvic acid containing 9.1% glycin, prior to the combining application of 35% hydroxyethylmethacrylate solution (HEMA) and a marketed dentin bonding agent.
It was found that the bonding efficacy of the dentin bonding system employed in this study deteriorated with the degree of reduction of Vickers hardness on the dentin surface after the dentin cleaning.View full abstractDownload PDF (5423K) -
Hisashi CHIGIRA, Toshie KOIKE, Tokuji HASEGAWA, Kazuo ITOH, Sadao WAKU ...1989 Volume 8 Issue 1 Pages 86-92,124
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe efficacy of marketed and experimental self etching dentin primers which contained dicarboxylic acids or their esterified salts diluted in 35% hydroxyethylmethacrylate (HEMA) solution were studied by measuring the wall-to-wall polymerization contraction of the light curing composite in the cylindrical dentin cavity and the tensile bond strength to the flat dentin surface. In both of the measurements, a marketed dentin bonding agent and resin monomer was applied after the treatment with experimental primers and a marketed primer, respectively. It was revealed that two experimental primers composed of the methacryloxyethyl-succinate or methacryloxyethyl-phthalate and HEMA, exhibited a remarkable effect on the bonding efficacy of a dentin adhesive employed in this study. A marketed primer which contained maleic acid and HEMA could not improve the bonding between the resin and dentin cavity wall although a significantly high bonding strength (11.9±5.7MPa) was obtained after 24 hours.View full abstractDownload PDF (1936K) -
Susumu HIRANO, Tadashi HIRASAWA1989 Volume 8 Issue 1 Pages 93-99,124
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe compressive creep test of a composite resin (0-3.5kg/mm2 stress levels) was conducted in water for 500h. Linear regressions were obtained between the creep strains and the compressive stress levels at various hours. It is possible to predict the creep strain of the composite from the regression when it reaches water absorbed equilibrium after 500h.
The stress of the hygroscopic expansion was calculated from the linear regressions. The maximum stress due to the hygroscopic expansion of the composite was 0.74kg/mm2 at equilibrium of the water absorbed of the composite.
The linear regressions at several compressive stress levels were obtained within 30-50hr in the strain-log time diagrams.View full abstractDownload PDF (2605K) -
Yoshio KOZONO1989 Volume 8 Issue 1 Pages 100-107
Published: June 25, 1989
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSDownload PDF (949K)
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