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Volume 17 (1998)
- Issue 4 Pages 223-
- Issue 3 Pages 163-
- Issue 2 Pages 93-
- Issue 1 Pages 1-
Volume 17, Issue 3
Displaying 1-6 of 6 articles from this issue
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Masayuki OKAZAKI, Xue WANG, Marcia S. TOGUCHI, Masayuki TAIRA, Junzo T ...1998 Volume 17 Issue 3 Pages 163-173
Published: 1998
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe mechanism of bonding between metal and ceramic in systems using the functionally graded method with pure gold and gold mixture as a primer was examined. Four types of samples, porcelain, porcelain-gold, porcelain-metal and porcelain-gold-metal were prepared. The gold intermediate layer was fired at 1000°C. For porcelain and metal, low-fusing opaque, body porcelain and palladium alloy were used. The intermediate layer was composed of three layers; pure gold, gold-palladium and gold-porcelain layer. During the bending test of each sample, the porcelain peeled away from the porcelain-metal system, while porcelain with the gold intermediate layer remained on the metal surface even after maximal loading. The bond strength of the porcelain-gold-metal system was much higher than that of the porcelain-metal system, and the toughness of the former was much greater than that of the latter. Laser microscopy and scanning electron microscopy (SEM) showed a smooth interface between the intermediate layer and the metal which suggested proper chemical bonding, and no gap was observed. At the interface between the porcelain and the gold intermediate alloy, a good mechanical anchor lock was observed. Electron probe microanalysis (EPMA) showed a clear distribution of each element (e.g. Si, Au and Pd) in the porcelain, gold intermediate layer and metal frame.View full abstractDownload PDF (4038K) -
Min YAN, Hidekazu TAKAHASHI1998 Volume 17 Issue 3 Pages 174-185
Published: 1998
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSIn this study, we developed a new gypsum-bonded investment for high-fusing alloys. The investment was composed of gypsum as a binder and alumina as a refractory. Effects of type of alumina powder and gypsum content on characteristics of the gypsum-bonded alumina investment were investigated. Obtained characteristics of this experimental investment were as follows: fluidities ranged from 48.8 to 88.9mm; setting times ranged from 21.2 to more than 120 minutes; setting expansions ranged from 0.4 to 1.3%; green strengths showed 0.5 to 4.5MPa; fired strengths ranged from 0.2 to 1.7MPa; thermal expansions after firing were -1.60 to 2.16%. Thermal expansion occurred because of the chemical reaction between Al2O3 and CaO decomposed from gypsum. These results suggest that this gypsum-bonded alumina investment with 20 or 25mass% gypsum content possessed the fundamental properties for high-fusing alloy casting.View full abstractDownload PDF (1792K) -
Sen HIGASHI, Tomoko OHSUMI, Keiko OZUMI, Kayoko KUROKI, Yuri INOKUCHI, ...1998 Volume 17 Issue 3 Pages 186-194
Published: 1998
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSA newly developed calcium phosphate cement, MM, was evaluated for tissue irritability by means of cell cultures. In this study, MM showed extensive mild cytotoxicity compared with other cements before setting. Inhibition of adhesion of L-929 cells was not observed after contact with MM for 24 hours. The influence of MM on colony formation was approximately the same as that of another calcium phosphate cement and less than that of a glass ionomer cement. Toxicity of MM after setting was compared with four cements; another calcium phosphate cement, glass ionomer cement, silicate cement and zinc oxide eugenol cement, but MM showed the least influence on cell morphology. Judging from these results, MM appears to be less cytotoxic than the cements in current use.View full abstractDownload PDF (1521K) -
Chihiro TANI, Kazuo ITOH, Miwako OHBA, Kazuyo TADA, Atsufumi MANABE, H ...1998 Volume 17 Issue 3 Pages 195-204
Published: 1998
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe efficacy of four commercial and two experimental dentin bonding systems was examined by observing the cavity adaptation of commercial light-cured resin composites restored in the dogs scheduled to be sacrificed after a medical experiment. Before being sacrificed, a cylindrical class V cavity was prepared in each canine, and the cavity wall was treated with one of four commercial dentin bonding systems according to the manufacturers instructions followed by resin composite filling. The maximum contraction gap widths at the occlusal, gingival and axial cavity wall were measured on the cavity section 30min after the polymerization of the resin composite under a light microscope.
Contraction gap formation was completely prevented in only one of the experimental groups in which the cavity wall was primed with 35vol% glyceryl mono-methacrylate (GM). In addition, observation of cavity adaptation in the canine in vivo was useful to estimate consistently the efficacy of the bonding systems.View full abstractDownload PDF (4187K) -
Koichi FUJII, Gakuji TSUKADA, Osamu UENO, Akira IMAIZUMI, Akihisa MASU ...1998 Volume 17 Issue 3 Pages 205-212
Published: 1998
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSIn order to clarify the viscoelastic properties of four commercial resins for crown and bridge, the dynamic shear modulus (G'), Knoop hardness (KHN), filler content, quantity of unreacted substance and thermal expansion were measured. The results were as follows. The G' (37°C) of each material ranged from 2.61∼11.1GPa, and gradually decreased with increasing temperature. KHN (23°C) ranged from 29.4 to 120, and the most significant correlation (0.999) was found between G' and KHN. Of the relationship among G', filler content and unreacted substance, there was a highly significant correlation (0.980) between G' and filler content. The coefficient of linear-thermal expansion (α) also ranged from 17.9∼65.0×10-6/°C (25-60°C), and the correlation (-0.961) between G' and α was meaningful. It can be presumed that the temperature dependence of G' is closely connected with the specific volume of each material, together with an increase in temperature.View full abstractDownload PDF (802K) -
Masahiro OHSAWA, Yoshihiko HAYASHI1998 Volume 17 Issue 3 Pages 213-219
Published: 1998
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe correlation between the degree of linear setting expansion and the dimensional changes in a mold space was examined. The dimensional changes in the mold were determined by investing the MOD-type wax pattern using a die-investing material of which the degree of the setting expansion was controlled by diluting a concentration of colloidal silica solution. The wax was eliminated in an electric furnace at 130°C and a fusible alloy, m.p. 48°C, was cast into the mold space at room temperature. The dimensions of the wax pattern and the casting were compared. The degree of linear setting expansion was measured in a paper ring by means of a dial gauge. A high correlation was found between the dimensional changes of the mold space and the degree of the linear setting expansion. The expansion was highest at the axiogingival portion while those at both the axial dimension and the occlusal dimension were smallest. Linear regression lines (Y=AX+B) revealed the differences in the expansion mode at both the external and internal portions to show a discrepancy in value B.View full abstractDownload PDF (564K)
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