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Yasuo SIOTA
1985 Volume 4 Issue 1 Pages
1-7,119
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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Effects of heat-treatment and
60Co γ-ray irradiation on human teeth were examined by Wide Angle X-ray Diffraction (WAXD) and Small Angle X-ray Scattering (SAXS). Heat-treatment increased the intensity of SAXS. This suggests that heating altered the scattering centers in a large amount of collagen.
Irradiation doses of 10
7 to 10
8R decreased the intensity of SAXS. However, further irradiation up to 10
9R increased the intensity of SAXS. The former phenomenon arises from the decrease in difference of electron density between organic and mineral compositions. The latter arises from the newly separated amorphous particles from the original collagen materials.
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Part 2. Microscopic observations
Hiroyuki NAKAI, Kazuomi SUZUKI, Hirokazu HASHIMOTO
1985 Volume 4 Issue 1 Pages
8-18,119
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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Effects of mixing time on the microstructure of several low and high copper amalgams were observed. An apparent relationship was found between the microstructure, especially enclosed porosities, and physical properties reported previously
1). In regard to the mixing time, a greater influence was observed with either lathe-cut or high copper than spherical or low copper, with respect to the particle shape and copper content of the alloys. Sufficient mixing is required for lathe-cut high copper alloys.
However, differences in the mixing characteristics were often observed even with alloys having similar particle shape or composition. This may be due to the dissimilar surface characteristics of alloy particles, causing the differences in affinity with mercury. Prolonged mixing to eliminate the porosities in the set amalgam may cause the poor results, such as remarkably shortened working time and increase in shrinkage during setting.
The mixing time of an amalgam alloy should be estimated on both technological and practical bases.
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Naoyuki KATAKURA, Michio KAWAKAMI
1985 Volume 4 Issue 1 Pages
19-24,119
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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Stress relaxation contributes greatly to the restriction of shrinkage of the pattern at the male portion of the die. In this study, three types of binary mixtures consisting of paraffin and another ingredient were formulated, and the effects of ingredients on stress relaxation of these mixtures were investigated.
By the application of the time-temperature superposition principle for each material, relaxation curves at various temperatures were superimposed to a single master curve with good overlapping. Addition of carnauba wax to paraffin resulted in a high restriction of stress relaxation in the high temperature range. Addition of beeswax to paraffin decreased the modulus of mixtures in the low temperature range. Dammar caused no appreciable change in stress relaxation of mixtures.
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The effects of Cu and Cr as additive elements
Kunio WAKASA, Masao YAMAKI
1985 Volume 4 Issue 1 Pages
25-32,120
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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The oxygen concentration in molten binary Ni-based alloys was estimated by an electrochemical method using solid electrolytes. The electrochemical cell was Pt|Mo+MoO
2|ZrO
2(MgO)|O(in liquid)|Mo. The activity of oxygen determined from the electromotive force (EMF) of the cell increased when Cu was added to pure Ni. Namely, the oxygen concentration was higher than that for pure Ni only when the amount of Cu was between 1wt% and 30wt%. In binary Ni-Cr alloys, it was deduced that the addition of 15 and 20wt% Cr to pure Ni showed the lower oxygen concentration, although the liquid Ni-based alloys having 5, 7 and 10wt% Cr tended to have higher oxygen concentrations than pure Ni.
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Syntheses of Succinoxy Methacrylates and Their Adhesion to Polished and Etched Tooth Surfaces
Tadao FUKUSHIMA, Minoru KAWAGUCHI, Yusuke INOUE, Koji MIYAZAKI, Takash ...
1985 Volume 4 Issue 1 Pages
33-39,120
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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Four kinds of succinoxy methacrylates (2-succinoxypropyl methacrylate (2SPrM), 2-succinoxyethyl methacrylate (2SEM), 2-succinoxy-3-phenoxypropyl methacrylate (SPPM), and 2, 2-bis-(-4-(-2-succinoxy-3-methacryloxypropoxy)-phenyl-)-propane (Bis-SGMA)) were synthesized to improve the adhesive property of dental resins to tooth structure. Also the relations between concentration or chemical structure of these monomers and their adhesive property to polished and etched tooth surfaces were investigated.
The highest adhesion to unetched enamel surface after standing at room temperature and after soaking in water was obtaind with Bis-SGMA (50mol%), and SPPM (40mol%).
The highest adhesion to unetched dentin surface after standing at room temperature and after soaking in water was obtained with 2SEM (55-65mol%).
The highest adhesion to etched enamel and dentin surfaces was obtained with SPPM (40mol%), and Bis-SGMA (15-25mol%).
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Takahito KANIE, Shinichi NISHIOKA, Shigetaka NAGAOKA, Hong-Jih LIU, Ma ...
1985 Volume 4 Issue 1 Pages
40-46,120
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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The dimensional changes of 4 types commercial luting cements after setting were examined in distilled water, using a developed thermal expansion testing apparatus. The measurements were carried out under three conditions: increasing temperature (from 37°C to 60°C), decreasing temperature (from 37°C to 10°C), and constant temperature (37°C). The results indicated that: (1) the zinc phosphate cement possessed superior dimensional stability after setting; (2) the variation values in dimension of Fuji Ionomer and CBA varied markedly with the specimen thickness tested; and (3) with Fuji Ionomer, this value also varied with the mixing proportion.
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1. A method of determining elastic modulus of oral soft tissue
K. INOUE, H. ARIKAWA, K. FUJII, N. SHINOHARA, N. KAWAHATA
1985 Volume 4 Issue 1 Pages
47-53,121
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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A method of measuring the elastic modulus of oral soft tissue was developed and used to determining the elastic moduli of oral soft tissue in two patients and of two elastomeric impression materials.
The elastic modulus of oral soft tissue varied considerably according to positions measured and became slightly higher, compared with that of elastomeric impression materials. These results suggest that the accuracy of dental impression is affected by the viscoelastic properties of oral soft tissue. The developed instrument was also found to be appropriate for the comparative assessment of rheological properties of oral soft tissue and impression material.
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Hideaki SHINTANI, Naoki SATOU, Aki YUKIHIRO, Junko SATOU, Izumi YAMANE ...
1985 Volume 4 Issue 1 Pages
54-61,121
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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Water sorption, solubility and staining properties of three microfilled resins and one conventional resin polished by various methods were studied.
Water sorption of smooth surfaces after 60 days was higher than those of white point-polished and finished surfaces, while smooth surfaces showed the highest solubility.
For polished surfaces of composite resins, white point-polished surfaces had the highest value of staining, followed in order by smooth and finished surfaces. Among microfilled resins, Superlux showed the highest value of staining whereas Microrest the lowest, correlating with the values of water sorption and solubility.
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John M. POWERS, Mohamed M. BARAKAT, Hideo OGURA
1985 Volume 4 Issue 1 Pages
62-67,122
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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The color and optical properties of three anterior and four posterior composites were determined from reflection spectrophotometric data and Kubelka's equations. Samples were aged for 300 hours at 43°C, 90% relative humidity, intermittent water spray, and continuous exposure to a 2500 watt xenon light. After aging the composites were generally darker, more chromatic, and more opaque. Values of S (absorption coefficient) and K (scattering coefficient) increased and values of XI (infinite optical thickness) decreased. The light-cured composites were less stable than the chemically cured ones.
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Part 1 Effect of fresh dentin and storing conditions
Sumio KIMURA, Takeyoshi SHIMIZU, Benji FUJII
1985 Volume 4 Issue 1 Pages
68-80,122
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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The effects of preserving conditions and time after extraction of human teeth, as specimens for bond strength of composite resin to the dentin, were investigated by the tensile test method and scanning electron microscopy (SEM).
When the teeth were stored in physiologic saline solution, bond strength at 15 minutes after extraction showed the lowest value (13kg/cm
2), and at 1 to 12 weeks it was elevated to about 35kg/cm
2. However pretreatment with citric acid-FeCl
3 solution of dentin surface increased the bond strength 3-fold. The teeth stored in formalin for 6 months had the highest bond strength (80kg/cm
2). On SEM observation of the dentin and resin surfaces following the tensile test, a clear correlation was found between range of bond strength and appearance of resin tags.
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Seiichiro KONDO, Shoji OHKAWA, Takao HANAWA, Toshi SUGAWARA, Mamoru OT ...
1985 Volume 4 Issue 1 Pages
81-87,122
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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Load-load line displacement diagrams and acoustic emission characteristics were measured in the transverse test of conventional and microfilled composite resins in order to develop a method for the evaluation of strength of dental restorative materials and the non-destructive inspection of restorations in oral cavity. Both conventional and microfilled composite resins exhibited burst type acoustic emission. Conventional composite resins generated the abrupt acoustic emission, but microfilled composite resins did not showed an appreciable increase in acoustic emission before fracture for a low acoustic emission activity.
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Seiji BAN, Yoshifumi TAKAHASHI, Jiro HASEGAWA
1985 Volume 4 Issue 1 Pages
88-92,123
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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Analyses were performed on the chemical composition of zinc phosphate, polycarboxylate, and glass ionomer cement. The results showed that powders of zinc phosphate and polycarboxylate cements contained mainly alumino-silicate glass, AlPO
4 and CaF
2. The main component of the liquid of zinc phosphate cement was approximately 56% aqueous solution of orthophosphoric acid with a small amount of aluminum and zinc. On the other hand, liquids of both polycarboxylate and glass ionomer cements were composed of approximately 42.1-59.3% aqueous solution of poly-carbolic acid.
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(Part 2). Fluid behavior of Calvital
Masami TAKEUCHI, Tatsushi KAWAI, Hisao FUKUI, Hiroshi MURAKAMI, Jiro H ...
1985 Volume 4 Issue 1 Pages
93-99,123
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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The rheological properties of a calcium hydroxide paste (Calvital) were studied using a cone and plate viscometer. Calvital was considered to be thixotropy based on the hysteresis loops of shear-stress rotational speed. The loops changed with temperature and the powder/liquid ratio. The strength of the thixotropy increased as the temperature was decreased and as the powder/liquid ratio was increased. Between these two factors, the thixotropy was influenced largely by the powder/liquid ratio.
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YOSHIAKI TANI
1985 Volume 4 Issue 1 Pages
100-109
Published: June 25, 1985
Released on J-STAGE: February 12, 2009
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