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Volume 13 (1994)
- Issue 2 Pages 131-
- Issue 1 Pages 1-
Volume 13, Issue 1
Displaying 1-11 of 11 articles from this issue
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Takuji IKEMI, Kimiya NEMOTO1994 Volume 13 Issue 1 Pages 1-8,123
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSRecently, three types of lining materials have been used in dental clinics, conventional powder-liquid glass ionomer cement, light-cured powder-liquid glass ionomer cement and a light-cured single paste type. This study compared the effects of these lining materials on the shrinkage stress of light-cured composite resins during the early setting stage, when polymerization shrinkage occurs. After the second irradiation, the shrinkage stress of composite resins lined with light-cured powder-liquid type cements was approximately 1.0 to 2.2MPa when the lining application was 1.5mm and 0.5mm thick, respectively, demonstrating that a thicker lining application decreased shrinkage stress. The single paste type was only slightly effective in reducing shrinkage stress in composite resins. Although the sample lined with conventional powder-liquid type showed that stresses were less affected by the thickness of the lining, and had the lowest shrinkage stress of all conditions tested, greater exfoliation from the composiView full abstractDownload PDF (414K) -
Kohji MIYAZAKI, Toshikazu TAKATA, Takeshi ENDO, Akihiko INANAGA1994 Volume 13 Issue 1 Pages 9-18,123
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSThe syntheses and polymerizations of acrylate (ASOE) and methacrylate (MASOE) containing spiro ortho ester moieties were carried out and the properties of the polymers obtained were investigated. The ringopening reaction of the Spiro ortho ester groups proceeded well during heat polymerization (HC) with the ionic initiators (BSS and HPSS). However, a small amount of unreacted carbon-carbon double bond was observed in the polymers obtained. Not only vinyl polymerization but also a small amount of ring-opening reaction took place during polymerization with radical initiators (BPO, AIBN, DTB and CQ). The poly(MASOE) s obtained by HC with BSS, BSS/AIBN and BSS/BPO were plastic like polymers. Low volume shrinkage was observed during HC and UVLC of ASOE and MASOE with ionic initiators. These shrinkages were smaller than those of conventional methacrylate.View full abstractDownload PDF (819K) -
Shigeru UNO, Hirokata SHIMOKOBE1994 Volume 13 Issue 1 Pages 19-24,124
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSThe influence of contraction stress in composite resins on both the shear bond strength to dentin (BS) and marginal adaptation in a standardized dentin cavity was investigated using three restorative resin systems. A teflon ring mold (TF) or copper ring with a roughened inner surface (CP) placed on human tooth dentin was filled with the composite resin, and a shearing test was then performed. ANOVA of BS demonstrated a significant influence from the resin systems and type of molds. BSCP tended to be lower than BSTF in all three systems. This suggested that the inner surface of the CP restricted the flow of resin and then contraction stress occurred at the interface of the bond to the dentin. The system which demonstrated the smallest difference between BSTF and BSCP also showed the best adaptation. This result indicates that contraction stress in the composite resin plays an important role in marginal adaptation.View full abstractDownload PDF (336K) -
Hideaki ITOH, Yuichi WAKISAKA, Yoko OHNUMA, Yoshinori KUBOKI1994 Volume 13 Issue 1 Pages 25-35,124
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSA new porous hydroxyapatite ceramic was prepared by cold isostatic pressing and sintering of the flaky powder, that was synthesized through two-stage hydrolysis of brushite; (1) a structural change into the apatite structure and (2) a compositional increase in Ca/P ratio, according to the method of Monma and Kamiya. The appearance of the synthesized powder resembled the flaky shape of the starting materials and its average particle size was about 15μm. This powder consisted of fine needle crystals, which had a tendency to grow into the larger grains, but the powder was highly resistant to sintering under the usual heating conditions at 1200°C. Porous hydroxyapatite blocks and granules were prepared by cold isostatic pressing and sintering a pellet consisting of the hydroxyapatite powder and spherical polymer beads. The product showed a 70% apparent porosity with spherical pores, ranging from 100-200μm in size, and most pores were interconnected. These properties were ascribed to the effect of cold isostatic pressing on the hydroxyapatite powders with the flaky shape.View full abstractDownload PDF (2862K) -
Kazuhito SEKIYA, Akira OKAMOTO, Masayoshi FUKUSHIMA, Masaaki IWAKU1994 Volume 13 Issue 1 Pages 36-46,124
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSUsing a scanning electron microscope (SEM) and an electron probe surface roughness analyzer (ERA), we conducted the in vivo study of the effect of various filler components on the wear of composite resins. Experimental light-cured composite resins were prepared employing three different filler components; -(1) Silica type, (2) Strontium type, and (3) Barium type. The filler content for all three types was 80wt%, with the mean particlesize being 2.6μm in diameter. The resin monomers consisted of 40wt% Bis-GMA, 40wt % TEGDMA and 20wt% UTMA. These materials were placed in 2mm diameter cylindrical cavities located in the OCA (occlusal contact area) or the CFA (contact free area) of cast crowns temporarily set in a volunteer patient's mouth. The crowns were removed at monthly intervals for longitudinal SEM observation. After two months, worn surfaces were also analyzed by ERA. The result showed that the wear patterns of the composites were characterized by the filler components, especially in the OCA.View full abstractDownload PDF (3856K) -
Masayuki KON, Fumiaki KAWANO, Yoshio TADA, Sanshiro INOUE, Kenzo ASAOK ...1994 Volume 13 Issue 1 Pages 47-54,125
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSThe relationship between fracture strength and crystallization in castable glass-ceramics was studied using castable glass-ceramics which contained crystalline apatite and magnesium titanate. Bending strength was increased with increases in crystal phases; 90, 124, 122 and 162MPa were recorded for as-cast specimens and specimens cerammed at temperatures of 905°, 925° and 945°C, respectively. The results of bending tests suggest that the crystallization of magnesium titanate is more effective than that of apatite in increasing the strength of glass-ceramics. Fracture toughness in specimens reheated at 905°C was doubled compared with as-cast specimens. The apatite particles precipitated during ceramming treatment were thought to be an important factor in increasing both the fracture toughness and crack pinning effect.View full abstractDownload PDF (1158K) -
Jiro TANAKA, Kazuomi SUZUKI, Hiroyuki NAKAI1994 Volume 13 Issue 1 Pages 55-65,125
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSO-Methacryloyl-N-acyl tyrosines (MAATY) having acyl groups with the various chain length were synthesized and the strength of bonding agents, consisting of MAATY as an adhesive monomer, to unetched human dentin was studied to elucidate the relationship between the molecular structure of MAATY and its adhesive characteristics. Increasing the flexibility of the carboxyl group of tyrosine favors the interaction with the tooth substrate, causing strict bonding. Also, the properties of the neighboring carboxyl group, i.e., steric hindrance and hydrophobicity, hydrophobic-hydrophilic balance in the monomer, and shrinkage of the monomer at copolymerization, are considered important. Especially, steric hindrance of the substituted group neighboring the carboxyl group of tyrosine would play an extremely important role in the adhesion of O-methacryloyl-N-octanoyl tyrosine. The maximum tensile bond strength was obtained with a bonding agent consisting of O-methacryloyl-N-hexanoyl tyrosine (15mol%) and hydroxyethyl methacrylate (85mol%), and the strength (4.75MPa) was the maximum in all methacrylates with phenylalanine as a bone structure.View full abstractDownload PDF (909K) -
Yohji IMAI, Ryuichiro IKEMURA1994 Volume 13 Issue 1 Pages 66-75,126
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSA primer containing cupric [Cu (II)] ions that promoted the interfacial initiation of polymerization from dentin surfaces was studied. Bovine dentin surfaces were treated with 10% phosphoric acid, then with a Cu primer consisting of aqueous 35% 2-hydroxyethyl methacrylate (HEMA) containing 0.03% cupric salt, and finally bonded with 4-META/MMA-PMMA resin initiated with oxidized tributylborane (TBBO). The use of the Cu primer resulted in a mean bond strength of 12.5MPa compared with 3.8MPa without the primer and 6.3MPa using a 35% HEMA primer without Cu. The Cu primer produced a bond strength of 13.5MPa even without 4-META in the resin system. Use of the Cu primer should simplify the bonding procedure since enamel and dentin can be etched simultaneously with 10% phosphoric acid.View full abstractDownload PDF (1054K) -
Florentina T IIMURO1994 Volume 13 Issue 1 Pages 76-88,126
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSThe use of a rare earth magnetic attachment system as a means of retaining dentures or maxillofacial prostheses results in artifacts, when magnetic resonance imaging (MRI) is used as a diagnostic tool. In such cases, the artifact is not caused by the magnet itself, but by the ferromagnetic stainless steel keeper that is placed in the body. This report evaluates such ferromagnetic stainless steel devices with respect to magnetic resonance imaging artifacts. A grid phantom and a 0.2 Tesla superconducting system were used to assess the imaging artifacts. The magnetic properties, shape, composition and size of ferromagnetic stainless steel devices were analyzed to study the relation MRI artifacts and ferromagnetic materials. The higher the magnetic permeability was, the greater the artifact produced. The size and volume of the material directly influence the artifact produced. The artifact size can be attenuated by the sequence used to obtain the images.View full abstractDownload PDF (3095K) -
Mariko YAMAGA, Takeshi KOIDE, Toyoji HIEDA1994 Volume 13 Issue 1 Pages 89-102,126
Published: June 25, 1994
Released on J-STAGE: May 25, 2009
JOURNAL FREE ACCESSWe investigated the fluorine uptake in various layers of bovine dentin treated with glass ionomer cement (GIC) where a tannin-fluoride preparation (HY agent) was incorporated in the cement powder at ratios of 0% (HY 0), 1.5% (HY 1.5), 5% (HY 5), and 10% (HY 10) by weight. The crystallinity of the dentin treated with the HY 0 and HY 10 cements was also investigated. The higher the ratio of incorporated HY agent, the deeper the penetration of fluorine in the dentin, and the greater the amount of fluorine taken up that bonded with the apatite. Compared with total fluorine uptake, more time is needed for fluorine to form a stable bond with apatite. It is also suggested that the crystallinity of dentin is enhanced when exposed to GIC containing the HY agent.View full abstractDownload PDF (985K) -
Danny LOW, Helen BEST, Toshiko MORI1994 Volume 13 Issue 1 Pages 103-109,127
Published: June 25, 1994
Released on J-STAGE: January 07, 2010
JOURNAL FREE ACCESSIn order to establish the most suitable technique for the construction of cast titanium denture frames, an experimental model was developed for the quantification of casting success. A relatively large wax pattern (36×29×0.9mm) was prepared from a grid sheet used for the construction of cast cobalt chromium partial denture frames. The pattern consisted of 100 circles and the number of completely cast circles was counted to obtain a percentage success rate. The castings were complete with pure titanium but incomplete (average 54%) with a titanium alloy. For an inspection of internal defects the radiographic conditions were optimised by adopting a relative density of about 2.0. The procedures described will help in establishing the most suitable casting technique for the construction of titanium denture frames for any casting system employed in a laboratory.View full abstractDownload PDF (1504K)
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