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Part III The Effects of Amount of Polymerization Initiator on the Shrinkage Stress
Kimiya NEMOTO, Koichi KOMATSU, Kozo HORIE, Rafael L.BOWEN, Yasuhiro TA ...
1993 Volume 12 Issue 1 Pages
1-7
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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Three kinds of experiments were performed about the composite resin produced by way of trial which was mixed 60% irregular silica and the microfiller (MF) in the dimethacrylate contained the initiator varying 0.25 to 1.0%.
First, the linear shrinkage was measured with the apparatus which has a ditch equipped with the aluminium blocks at the each end. The linear shrinkage was larger with increasing the initiator quantities. Unfilled resins tended to show larger shrinkage.
Second, the shrinking stress in the open type cavity was measured during hardening. It was increased logarithmically with more initiator addition. The shrinking stress of unfilled resin was 2.6 times larger than the composite resin, and these were direct proportion.
Third, the surface profile of specimens were measured after hardening. The profile unfilled resin was changed a parabola to square with increasing the initiator quantities. These volume of the shrinkage was 8% of all, and the composite resin showed the volumetric decreasing with shallowing the parabola shape gradually.
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Motonobu MIYAO, Mutsuo YAMAUCHI, Tooru NAGASAWA, Takayasu GOTO
1993 Volume 12 Issue 1 Pages
8-16
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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Radiopacity of resin for crown, brige and inlay is a necessary property in clinical use. This study examined the radiopacity of commercial autocured resin, thermosetting resin and resin for inlay and the factors causing high radiopacity.
The radiopacity of autocured resin and thermosetting resin were not high, but resin for inlay demonstrated good radiopacity. Therefore, the consitituent elements of filler materials were investigate.
The filler size and structure were observed under scanning electron microscope. Elemental analysis of fillers was made with an electron probe micro analyzer, and the filler substances were identified by powder X-ray diffractometer.
The filler particle size, was less than 40 μm. Silicate glass and/or crystal silica were found in all fillers. ZrSiO
4 or YbF was identified in some fillers, and Ba ions were detected in the glass fillers. The resin for inlay including ZrSiO
4 was the most radiopaque filler and next was that with Yb ion.
These results suggest that fillers including Zr ion would be preferable for obtaining higher radiopacity in composite resins for inlay.
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-Relationship between the Impression Thickness and the Influence from the Cooling Shrinkage of Impressions-
Hisako HIRAGUCHI, Akiya KAWAMOTO, Shinji NAGASAKI, Hisami NAKAGAWA, Hi ...
1993 Volume 12 Issue 1 Pages
17-28
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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The reproducibility of cylindrical stone casts obtained from four types of elastomeric impression materials (hydrophilic addition silicone, addition silicone, condensation silicone and polysulfide) with four thickness (1.0 mm, 2.5 mm, 5.0 mm, 7.5 mm) at the different temperatures during setting (23℃ and 32℃) was evaluated using a three-dimensional measuring system.
For all impression materials, the dimensional accuracy of the stone casts was affected by the temperature during setting and by the impression thickness. The distortion in diameter due to cooling shrinkage of the impression material increased as the impression thickness increased, with a diameter change of about 10-12 μm for each 1 mm increase in impression thickness.
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1. Accelerated Aging Tests of Experimental Composite Resin
Minoru KAWAGUCHI, Tadao FUKUSHIMA, Koji MIYAZAKI
1993 Volume 12 Issue 1 Pages
29-33
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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Four modes of accelerated aging tests were carried out on experimental BisGMA-based composite resins (Vf=55%: splinter-shaped or spherical silica) to investigate the relationships between the degradation of matrix resin and resin/filler interface and the mechanical properties. Degradation of resin/filler interface was evaluated on composite resins thermo-cycled (0-10
5 cycles) and immersed in distilled water (37℃ and 60℃) for up to 180 days. Matrix resin degradation was evaluated in composite resins immersed in 75% ethanol at 37℃ for up to 180 days. The results of this study revealed that degradation of resin/filler interface and matrix resin affected the mechanical properties considerably. Degradation was accelerated by the number of thermo-cycles and the immersion periods in various conditions. The results indicated that the degradation of the resin/filler inteface and the matrix resin significantly affected the clinical durability of composite dental resins.
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-Treatment of Acid-etched Dentin by Aqueous Solution of HEMA-
Kazuomi SUZUKI, Hiroyuki NAKAI
1993 Volume 12 Issue 1 Pages
34-44
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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The effect of tooth surface treatment and its mechanism was examined to obtain improved adhesion of restorative resin. From the fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and adhesive strength studies with respect to collagen and acid-etched dentin, treated with aqueous solution of 2-hydroxyethyl methacrylate (HEMA), the following results were obtained. Water was an essential component in respect to the adsorption of HEMA to collagen fiber. Substantial amounts of HEMA were adsorbed by collagen fiber when the concentration range of HEMA in aqueous solution was 6〜60wt%. Following treatment with HEMA, it was apparent from SEM observation that collagen fibers were stiffened and maintained a fibrous network. In regard to tensile bond strength of a composite resin to dentin, 12.07, 10.9 and 7.04 MPa was obtained with phosphoric acid-30% HEMA, citric acid-30% HEMA and EDTA-30% HEMA aqueous solution, respectively.
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Masayuki KON, Norihiko KUWAYAMA
1993 Volume 12 Issue 1 Pages
45-50
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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The effects of adding H
3BO
3 to composite powder compacts consisting of ZnO and Al
2O
3 were investigated.
The volumes of ZnO-Al
2O
3 composite compacts were increased with an increase of gahnite(ZnAl
2O
4) crystallization at a firing temperature of above 1, 000℃. A compact of equivalent mole ratio had a maximum value of firing expansion compared with the other compacts, a linear expansion value of about 10% at a firing temperature 1, 350℃. H
3BO
3 dispersed composite compacts with ZnO-Al
2O
3 of the equivalent mole ratio as matrix sintered with an increase of H
3BO
3 content, however, the compacts that contain less than 7 wt% H
3BO
3 addition did not shrink at a firing temperature of 1, 300℃ compared with the size of a green body. A bending strength value of 40 MPa was obtained from a non-contractible fired body with a porosity of 46%.
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Part 4 Effects of Cast Metal Core on Morphological Cytotoxicities
Yuki YOKOYAMA, Kiyoshi TAJIMA, Yasuhiro FUKAMIZU, Hiroshi KAKIGAWA, Ka ...
1993 Volume 12 Issue 1 Pages
51-58
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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Previous reports showed the superiority of pure Ti and Ti-6Al-4V alloy as prefabricated post materials by mechanical test and L-cell growth test using culturing media in which each post had been immersed for 1 month.
In this study, a cytotoxicity test was performed on several post and core materials in terms of the morphological changes in the cultured cells.
When the cells were cultured in the presence of the Ni-Cr alloy and stainless steel posts with a cast metal core, their cytoplasms were severely damaged by Ag and Zn leached from the cast Ag alloy core as well as by constituent elements from the post which were leached out with increasing rapidity by the galvanic reaction. The cast Au-Ag-Pd alloy core caused more marked damage, even to the cell nuclei, due to the additional leaching of Cu from the core. Although similar but minor cytotoxicities were found in the cases of pure Ti and Ti-6Al-4V alloy posts, they were attributed substantially to the leaching of elements from the cast core.
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Part I. Effect of Firing Temperature
Masanori ADACHI, Yutaka DOI, Takayasu GOTO, Nobukazu WAKAMATSU, Hideo ...
1993 Volume 12 Issue 1 Pages
59-67
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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This study examined the sintering process of hydroxyapataite (HAp) by measuring the electron spin resonance (ESR) signal intensity of Mn
2+ naturally present as an impurity in synthesized HAp. For HAp, the ESR signal of Mn
2+ appeared above 950℃, whereas for Li
3PO
4- added apatite (Li-HAp) the signal appeared at 750℃. The intensity of ESR signal of HAp and Li-HAp increased linearly with increases in the firing temperature. This finding suggests that Mn
2+ of HAp could diffuse to sites responsible for the spherical symmetry field shown in an ESR signal, indicating that other lattice ion species could diffuse as well. This sintering behaviour shown by ESR was the same as that measured by thermo mechanical analysis (TMA).
Thus far, the sintering process of HAp was measured only indirectly by thermo mechanical analysis (TMA), but ESR measurement can trace the behavior of the ion directly, and can elucidate the mechanism of sintering.
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Part II. Effect of Firing Time
Masanori ADACHI, Yutaka DOI, Takayasu GOTO, Nobukazu WAKAMATSU, Hideo ...
1993 Volume 12 Issue 1 Pages
68-73
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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This study examined the change of both the electron spin resonance (ESR) signal intensity of Mn
2+ and the structure of sintered hydroxyapataite (HAp) at various firing times.
The time needed for the sintering of pure HAp was decreased by increasing the firing temperature and finshed in 20 to 40 minutes at 1, 200℃. However, sintering HAp with Lithium Phosphate (Li
3PO
4) added as a sintering aid, started at a 200℃ lower temperature compared with pure HAp.
However, it was found that by firing HAp at a high temperature for a long time in the presence of Li
3PO
4 promotes decomposition of HAp and a large quantity of β-Ca
3(PO
4)
2 (β-TCP) was found. Moreover, it was clear that the ESR signal of Mn
2+ did not appear after decomposition to β-TCP.
There is possibilty that the decomposing process of HAp to β-TCP can be traced by ESR.
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Takao KAWAI, Tomiharu MATSUSHITA, Osamu TERANOBU, Keikichi SHIMADA
1993 Volume 12 Issue 1 Pages
74-83
Published: January 25, 1993
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The surface reaction of bi-phase ceramics containing HAP and αTCP or CaO during sintering of the hydroxyapatite powders of 3 different Ca/P molar ratios was investigated by immersing the materials into the media which contained 10% bovine serum.
When immersed in the medium saturated with Ca and P ions, HAP fine particles deposited on the surface of samples containing small amounts of αTCP or CaO. However, they dissolved when the medium was undersaturated with Ca ion. Samples containing large amounts of αTCP dissolved more quickly after the addition of bovine serum and were influenced by the Ca and P concentration of the media.
Therefore, it is important to take into account the effect of serum components when evaluating calcium phosphate ceramics
in vitro.
Since this corresponds to the
in vivo results, it is necessary to reduce the αTCP content of bi-phase ceramics to improve the biostability of implant ceramics in the earlier stage after implantation.
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I. Effect on Vickers Hardness
Fumio WATARI, Hideo NAKAMURA
1993 Volume 12 Issue 1 Pages
84-92
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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To strengthen dental titanium products utilizing the solid solution hardening effect by the diffusion of interstitial alloying atoms from surface to the interior, the materials were heated at temperatures of 500〜1, 200℃ in a controlled gas atmosphere (10
-5〜760 torr O
2, N
2, C
6H
6 partial pressure and vacuum). The effects of three interstitial alloying atoms, oxygen, nitrogen and carbon, were compared by measuring the micro-Vickers hardness. The distribution of Vickers hardness in the cross section of the specimen is composed of the surface hardening layer and the inner uniform hardness area. The surface hardening layer thickness experimentally obtained correlated well quantitatively with the calculated value using the activation energy of diffusion of interstitial atoms in titanium. The surface products from heat treatment were identified by X-ray diffraction. The properties of reactivity, diffusivity, solubility and the strengthening effect of the three interstitial alloying atoms were compared. Nitrogen, much less reactive than oxygen, had a solution hardening effect similar to oxygen, whereas carbon with slight solubility, easily formed a surface carbide film and had a lesser strengthening effect.
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Akihiko SAKAMURA
1993 Volume 12 Issue 1 Pages
93-103
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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Disinfecting is becoming an important aspect of dentin adhesion. Glutaraldehyde (GA) has been used clinically as a disinfectant for medical instruments and tools. It is also used in dentin adhesion as a component of the define primer. In this study, effects of addition of GA to etching agents and primers were studied in order to increase the use of GA as a disinfectant in dentin adhesion. Addition of GA to aqueous 2-hydroxyethyl methacrylate primer was very effective in increasing the bond strength between dentin and resin, independent of pretreatment agents like EDTA and phosphoric acid and initiator systems. Study of the dentin surface by scanning electron microscopy and infrared spectroscopy showed that the capability of etching dentin with aqueous phosphoric acid remained practically unchanged by the addition of GA, which had no negative effect in dentin adhesion, but rather some positive effect in increasing the bond strength. Aqueous solution of 10% phosphoric acid containing GA was suggested as a useful total etching solution capable of disinfecting and etching enamel and dentin simultaneously.
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Hirohide HIRANO
1993 Volume 12 Issue 1 Pages
104-116
Published: January 25, 1993
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The purpose of this study was to prepare and evaluate a new experimental resin for denture lining material. The new denture liner was composed of vinylidene fluoride/hexafluoropropylene copolymer (2-6F) and methyl methacrylate (MMA) containing 10% trimethylolpropane trimethacrylate. The denture liner was dual-cured by a combination of light and chemical initiator systems. This denture liner was compared with light-and chemical-cured denture liners of the same 2-6F and monomer composition and commercial denture liners of Rebaron, Rebaron LC and Tokuso Rebase. The physical properties, fitness, resistance to contamination and cytotoxicity were measured.
The dual-cured resin showed properties nearer to the light-cured than to the chemical-cured resins. It was similar or superior to the commercial denture liners in physical properties and fitness and considerably superior in resistance to contamination and low cytotoxicity. Thus, the new experimental dual-cured resin seems to have various properties suitable for a denture liner, and would be useful in clinical practice.
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Koichi FUJII, Hiroyuki ARIKAWA, Takahito KANIE, Takaharu TERAO, Hirono ...
1993 Volume 12 Issue 1 Pages
117-122
Published: January 25, 1993
Released on J-STAGE: April 05, 2018
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In order to investigate the dynamic viscoelastic properties of soft lining materials used for denture base resins, the storage modulus (E′) and loss modulus (E″) of 3 commercial soft lining materials (2 acrylates and a silicone) and a denture base resin (PMMA) were measured by a vibrating reed method. In addition, each PMMA lined with one of the above 3 soft lining materials was also measured.
The E′ and E″ of the 2 acrylic soft lining materials were markedly decreased in temperatures ranging from -20 to 50℃. In the neighbourhood of 75 to 80℃, a small peak in E″ was observed. However, temperature dispersion of E′ and E″ for the silicone soft lining material examined was considerably smaller than those of the 2 acrylic soft lining materials for the whole range of temperature tested. From these results, silicone soft lining material was fairly thermo-stable and tougher.
For denture base resins lined with one of the 3 soft lining materials, values of E′s and E″s at 37℃ were approximately one eighth lower than those obtained for PMMA. For PMMA lined with one of the 2 acrylic soft lining materials, the peak of E″ was observed near -10℃, and for PMMA lined with the silicone soft lining material, E″ decreased slightly depending on the increase in temperature tested.
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