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Volume 18 (1999)
- Issue 4 Pages 337-
- Issue 3 Pages 207-
- Issue 2 Pages 137-
- Issue 1 Pages 1-
Volume 18, Issue 2
Displaying 1-7 of 7 articles from this issue
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Seiji BAN, Kenji MATSUO, Norihiko MIZUTANI, Hironobu TANIKAWA, Kentaro ...1999 Volume 18 Issue 2 Pages 137-143
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSX-ray diffractometry (XRD) was used to analyze the crystal phases of three commercial dentin and incisal porcelains prepared by normal cooling, quenching in water, and controlled slow annealing after normal firing. There were no remarkable differences in the contents of either tetragonal and cubic leucite in the fired porcelain discs prepared under the three cooling conditions. Furthermore, there were no significant differences in the parameters of the α-axis and c-axis of tetragonal leucite, and the α-axis of cubic leucite among them. These results suggest that the cooling condition has little effect on the microstructural changes of leucite crystals in the dental porcelains, since the leucite crystals were formed at a higher temperature range than the firing- and cooling-temperature range and were stabilized by incorporation of additives into the lattice.View full abstractDownload PDF (740K) -
Part 2 Effects of acid and heat treatments of silver-tin filler particles on flexural properties of metal-resin compositeSomchai URAPEPON, Kiyoshi KAKUTA, Yukio MIYAGAWA, Hideo OGURA, Chatcha ...1999 Volume 18 Issue 2 Pages 144-154
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe effects of acid and heat treatments of silver-tin filler particles on the flexural properties of metal-resin composite restorative materials were investigated. Five metal-resin composite restorative materials containing different silver-tin filler particles treated under different conditions were experimentally prepared. The conditions of the alloy particles were; 1) as atomized (NT), 2) 1.8% HCl acid-treated (AT), 3) heat-treated at 150°C for 5min after AT (A15), 4) heattreated at 200°C for 5min after AT (A20) and 5) heat-treated at 250°C for 5min after AT (A25). The flexural strength and the flexural modulus of elasticity were measured for the five metalresin composites to evaluate the effects of the acid and heat treatments.
The flexural strength of the prepared composites was significantly influenced by the surface condition of the filler particles (p<0.01), and increased significantly when the as atomized particles (NT) were acid-treated (AT) or acid- and heat-treated at 150°C (A15), but then significantly decreased as the heat treatment temperature increased (A20 and A25). The strength of the A15 composite was significantly higher than those of the other composites, and exceeded that (about 60MPa) of the previous composite with no treatment. No significant difference was found in the flexural modulus of the composites.View full abstractDownload PDF (2869K) -
Shigeki MATSUYA, Yoko MATSUYA, Michio OHTA1999 Volume 18 Issue 2 Pages 155-166
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSWe prepared a new glass ionomer cement using bioactive CaO-P2O5SiO2(-MgO) glass and investigated its setting process using FT-IR and MAS NMR analyses. The compressive strengths of the cements depended on the glass composition and a maximum strength of 33.3±4.7MPa was obtained using cement with the glass composition of MgO: 4.6, CaO: 44.9, SiO2: 34.2 and P2O5: 16.3% in weight. FT-IR analysis showed that the COOH group in the polyacrylic acid decreased and carboxylate ion (COO-Ca2+) increased after the setting reaction. A broad signal appeared around -82ppm in 29Si MAS-NMR spectra of the glass and a new signal corresponding to hydrated silica gel formation appeared around -102 and -111ppm after setting. This suggests that Ca2+ was released from the glass powder to form carboxylate salt and that a degree of polymerization in the silicate network increased. The setting mechanism of the cement was found to be essentially the same as in conventional glass ionomer cement.View full abstractDownload PDF (1261K) -
Tohru IMAI, Shuichi YAMAGATA, Fumio WATARI, Masahiro KOBAYASHI, Kazuno ...1999 Volume 18 Issue 2 Pages 167-175
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe temperature-dependence of the mechanical properties of a new esthetic orthodontic wire with fiber-reinforced plastic (FRP) structure was investigated. The new FRP wire, fabricated by a hot drawing method, is 0.5 mm in diameter and has a multiple fiber structure composed of biocompatible CaO-P2O5-SiO2-Al2O3 glass fibers of 20 μm in diameter and a polymethyl methacrylate matrix. The flexural load at a deflection of 1 mm and Young's modulus at 24, 37, and 50°C under wet conditions showed similar fiber fraction dependence to those under dry conditions for a fiber fraction of 40-51%. The flexural load and Young's modulus tended to decrease slightly with increases in temperature. This tendency was larger for the lower fiber fraction. However, the difference in flexural load for a temperature difference of between 24°C and 50°C was at most 10 gf. This is negligibly small, and a constant orthodontic force regarding temperature change would be advantageous from a clinical point of view.View full abstractDownload PDF (2360K) -
Rie NOMOTO, Tadashi HIRASAWA1999 Volume 18 Issue 2 Pages 176-183
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe purpose of this study was to establish a method using FTIR to evaluate the polymerization characteristics of UDMA-based resins. Three kinds of experimental UDMA-based resins were prepared with various molar fractions. IR spectra of the cured film specimens were measured with FTIR before and after extracting residual monomer from each specimen by MeOH. From the IR spectra, the changes in the number of double bonds were measured, with the NH absorbance peak as an internal standard, and the amounts of residual monomers (RM) were calculated. The MeOH-immersed specimens were analyzed by HPLC. The RM measured by FTIR were compared with those measured by HPLC. The RM measured by HPLC were more than those by FTIR. Since these differences could be due to the difference in the area measured, this FTIR estimation method of residual monomers in cured resins using the NH absorbance peak as an internal standard could be an appropriate method when the resin monomer does not contain aromatic compounds.View full abstractDownload PDF (804K) -
Tae-Yub KWON, Yohji IMAI1999 Volume 18 Issue 2 Pages 184-193
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe aim of this study was to examine the effects of ferric chloride/citric acid/phosphoric acid conditioners on the surface morphology of enamel and dentin and on the adhesion of 4-META/MMA-TBB resin to conditioned tooth surfaces. Seven conditioners, including phosphoric acid and its mixture with citric acid and ferric chloride, were prepared and used for treating bovine teeth before bonding with the resin. The effects of the conditioners on the surface morphology and adhesion were examined by scanning electron microscopy and by atomic force microscopy and by tensile bond strength tests, respectively. The maximum bond strengths to tooth surfaces were obtained by using 3% ferric chloride/5% citric acid/10% phosphoric acid conditioner. Thus, enamel and dentin can be treated simultaneously with this conditioner before bonding with the 4-META/MMA-TBB resin system.View full abstractDownload PDF (5202K) -
1999 Volume 18 Issue 2 Pages e1
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSDownload PDF (43K)
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