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Michael F. BURROW, Momoko HAYASHIDA, Tadashi NEGISHI, Toru NIKAIDO, Ju ...
1993 Volume 12 Issue 2 Pages
97-105,271
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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Tensile bond strength and contraction gap tests were carried out using a new dentin bonding resin in association with various dentin conditioning and priming materials
in vitro. For the tensile bond test, significant differences were found between the nonconditioned and conditioned dentin, and the primed and non-primed dentin surfaces. The strongest bond was obtained using a combination of phosphoric acid conditioning and priming with HEMA in glutaraldehyde at 151.3kgf/cm
2. Gap test results showed the presence of gaps in all of the test groups, but with variation in the extent of gap formation. A not significant, inverse correlation was determined between the tensile bond strength and gap tests (R=-0.65). The new bonding resin obtained good bond strengths in all cases, but high bond strengths can only be obtained with a combination of etching and priming. Similarly, the smallest gaps were associated with the etched and primed groups.
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Seiji BAN, Mitsuru MATSUURA, Norihiro ARIMOTO, Jyunko HAYASHIZAKI, Yas ...
1993 Volume 12 Issue 2 Pages
106-117,271
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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A fresh octacalcium phosphate (OCP) precipitate without drying and three kinds of dried OCP powders were soaked for 3 weeks in 11 kinds of physiological solutions consisting of different combinations of Ca
2+, Mg
2+, K
+, Na
+, HCO
3-, HPO
42-, F
-, albumin, collagen and alkaline phosphatase, in three different pH values and at three different temperatures. X-ray diffraction study showed that most of the OCP had been transformed to apatite with low crystallinity after soaking in the solutions without Mg
2+. The IR absorption spectra revealed that CO
3 was incorporated in the apatite formed from OCP in the solution without Mg
2+, whereas OCP changed little after soaking in the solution containing Mg
2+. These results suggest that the presence of Mg
2+ in the solution is one of the most effective means of inhibiting the transformation of OCP to apatite by interrupting the precipitation process of apatite.
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Takao HANAWA, Bruce E. GNADE, Jack L. FERRACANE, Toru OKABE, Fumio WAT ...
1993 Volume 12 Issue 2 Pages
118-126,272
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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The surface layers formed on both a zinc-free and a zinc-containing dental amalgam after polishing and aging in air, water, or saline, were characterized using x-ray photoelectron spectroscopy (XPS) to determine the compositions of the surface layers which might govern the release of mercury from amalgam. The XPS data revealed that the formation of the surface layer on the zinc-containing amalgam was affected by the environment in which the amalgam was polished and aged, whereas that on the zinc-free amalgam was not affected. In addition, among the elements contained in amalgam, zinc was the most reactive with the environment, and was preferentially dissolved from amalgam into water or saline. Mercury atoms existed in the metallic state in the surface layer.
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Shigeaki KURATA, Noboru YAMAZAKI
1993 Volume 12 Issue 2 Pages
127-135,272
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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Improvement of the siloxane layer on minerals by using a bisfunctional silane, such as 1, 6-bis (trichlorosilyl) hexane and 1, 8-bis (trichlorosilyl) octane, and the effects on adhesion of methacrylic resin to glass plates treated with the silanes were studied. The tensile bond strength of the resin to the glass plate treated with bisfunctional silane alone was high (about 20MPa) in spite of the fact that the molecule contains no double bonds. Futhermore, a mixture of bisfunctional silane and 3-methacryloxypropyltrichlorosilane showed an excellent effect for tensile bond strength and water-resistance. Based on the results, it is suggested that the better water-resistant adhesion of the mixed silane depends on the higher degree of crosslinking in the siloxane phase and on the formation of an interpenetrating polymer network between the siloxane layer and the matrix resin.
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Florentina T. IIMURO, Takayuki YONEYAMA, Osamu OKUNO
1993 Volume 12 Issue 2 Pages
136-144,272
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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Implants and magnetic attachments are becoming widespread in dental treatment. Their associated use, implants and magnetic attachments, can be seen often too. In those cases, it is difficult to avoid coupling of different metals. The corrosion behavior of the metals is expected to be different depending on whether it is found in an isolated or a coupled condition. Potential corrosion couples in a dental magnetic attachment system among titanium, ferromagnetic stainless steel, gold alloy type IV, and gold-silver-palladium alloy were studied by an immersion test in 1% lactic acid for 7 days and potential/current density curves were measured. Corrosion of titanium and ferromagnetic stainless steel seemed to be accelerated by coupling with gold alloys or gold-silver-palladium alloys. On the other hand, the corrosion amount of gold alloy and gold-silver-palladium alloys were attenuated by coupling.
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Kazuhito SEKIYA, Akira OKAMOTO, Masayoshi FUKUSHIMA, Masaaki IWAKU
1993 Volume 12 Issue 2 Pages
145-158,273
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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This study investigated the effects of various monomer systems on composite resin wear
in vivo. Experimental light-cured composite resins were prepared employing four different monomer systems: (1) Bis-GMA type, (2) D-2. 6E type, (3) UDMA type, (4) UTMA type. The resin monomers consisted of 70wt% main monomer and 30wt% TEGDMA. These composites contained 80wt% fine quartz. The resins were placed in 2mm diameter cylindrical cavities located in the occlusal contact area or the contact free area in cast crowns, temporarily set in a mouth. The crowns were removed at monthly intervals, for longitudinal SEM observation. Two months after setting, wear was analyzed, using an electron probe surface roughness analyzer. Microabrasion of the resin matrix and loss of filler particles were observed for all types of monomer systems. The effect of matrix resin systems on occlusal wear was smaller than that of filler systems.
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Shigeru HIRABAYASHI, James A.A. HOOD, Tadashi HIRASAWA
1993 Volume 12 Issue 2 Pages
159-170,273
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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The extent of polymerization of light-cured composite resins cured in relatively large class II cavities was estimated by measuring Knoop hardness on sectioned surfaces of resin restorations. The influences of the incremental placement technique, exposure time, and post-curing of resin inlay on the extent of polymerization of two different resin materials were examined. For both MFR type (HE) and hybrid type (P50) materials, the 3-step incremental placement technique was superior when the cavity was restored by the direct filling method. For resin inlays, the post-heating improved the conversion of resin restorations. However, because the final degree of conversion of resin attained by heating was influenced by the initial conversion of the resin at the stage of light-curing, the 2-step incremental placement technique was recommended at the light-curing stage for even resin inlays. As the exposure time is influenced by the transmittance of material and the intensity of activator light, it should be optimized in accordance with manufacturers' directions.
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Osamu MIYAKAWA, Kouichi WATANABE, Seigo OKAWA, Syuji NAKANO, Hiro HONM ...
1993 Volume 12 Issue 2 Pages
171-181,274
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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The present study describes refractories which contribute to formation of skin holes of Ti casting. Plates consisting of quartz (
Qu) and cristobalite (
Cr) powders and
Qu- and
Cr-MgO mixtures were fired at high temperatures and used as phosphate-free molds. The cross-section of the castings was investigated using an optical microscope and an electron probe microanalyzer. Whereas the castings into the
Qu molds were almost complete, those into the
Cr molds were incomplete. The surface reaction zone of the
Qu molds formed a typical layered structure with fewer skin holes. That of the latter extended deeply into the interior with a net-shaped Ti-Si phase, cracks, and holes. Addition of MgO to
Cr effectively improved the castability and changed the reaction zone to the typical layered structure. However, slender holes occurred along the mold wall. The overall area around the holes was contaminated by Si and Mg. Probably, this resulted from a reaction of forsterite with Ti. The reactivity difference between
Qu and
Cr was not related to the fired strength of mold.
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Yoshiaki TANI, Toshiyuki NAMBU, Akiko ISHIKAWA, Shigeru KATSUYAMA
1993 Volume 12 Issue 2 Pages
182-189,274
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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This study quantified the contraction force and polymerization shrinkage of composite resins with / without β-Quartz Glass Ceramic Inserts (BQCI) as “Megafiller”. The materials used for the determination included a chemically cured composite and five light-cured composites. The system for measuring contraction force consisted of a transparent teflon tube for preparing the specimen, a small load cell, a dynamic strain guage and a pen-recorder. After the composite was packed into the teflon mold, a BQCI (Type R3) was inserted through the opening and the specimen was cured. Linear polymerization shrinkage of the composites was measured every 10 seconds from the start of mixing or irradiation to 90 minutes by the mercury bath method. Three pieces each of BQCI (Type T3) were inserted in each specimen. The results suggested that BQCI was markedly effective in reducing polymerization shrinkage, but was not always effective in reducing the contraction force during polymerization.
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Taiji SOHMURA, Junzo TAKAHASHI
1993 Volume 12 Issue 2 Pages
190-195,274
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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Improvement of the CAD process to design the shape of crown restorations of a 6 die was carried out by including the bite data of the antagonistic tooth in addition to the data measured in the previous paper. Initially, the position adjustment of the crown data with the bite data in the centric occlusion was attempted. After fixation of the crown data to a suitable position, modulation of the occlusal surface by the functionally generated path (FGP) data was carried out. To connect between the end of the crown data and the margin, a parabolic function was used instead of the B-Spline function used in the previous paper. As a result, the data points were connected more smoothly. Thus, CAD data which were composed of the die data, the crown data, and the connecting data were accomplished. They will be used as the basic data to CAM.
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Jiro TANAKA, Hiroyuki NAKAI
1993 Volume 12 Issue 2 Pages
196-208,275
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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Commercial root canal cleaning agents with the ability to dissolve collagen were used for the surface treatment to enhance the bonding of dental resins. These agents increased the bond strength of a dental bonding agent to dentin. For example, the tensile bond strength to bovine dentin was 10.7±3.9MPa following the joint use of M and N and 8.8±2.2MPa following the combined use of P-S and N. In these cases, the damage to the tooth surface was very small and was equal to or less than damage caused by EDTA. These results demonstrate the usefulness of commercial root canal cleaning agents for dentin surface treatment due to their ability to enhance the bonding of dental resin.
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Hiroko MIURA, Yoshima ARAKI, Hiroki OHNO
1993 Volume 12 Issue 2 Pages
209-218,275
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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A precipitation reaction between hydroxyapatite (HAp) and fluoride solution was analyzed by computer simulation. The system comprised excess HAp and 0.05-0.2M acetic buffer solutions containing 0.5-2.0mM potassium fluoride. The amounts of HAp dissolved and calcium salts precipitated, and activities of all the species present in the solution were calculated during the process. In the systems, calcium fluoride was initially precipitated when applying the fluoride solution to HAp, followed by precipitation of fluorapatite (FAp) and re-dissolution of the previously precipitated calcium fluoride at a critical pH at which the ion activity product exceeded the solubility product of FAp. The critical pH was increased with pH of the buffer, whereas it was scarcely affected by fluoride ion concentration, and it was necessary to introduce phosphate ions in advance into the buffer for predominant precipitation of FAp in this system.
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Chihiro TANI, Kazuo ITOH, Hisashi HISAMITSU, Sadao WAKUMOTO
1993 Volume 12 Issue 2 Pages
219-224,276
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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The bonding efficacies of three cmmercial dentin bonding agents and an intermediate resin combined with two self-etching dentin primers (aqueous solutions of methacryloxyethyl hydrogen phenyl phosphate (Phenyl-P, 20wt%) and either hydroxyethyl methacrylate (HEMA, 35wt%) or glyceryl methacrylate (GM, 35wt%)) were examined by measuring the wall-to-wall contraction gap of a light-activated resin composite in a cylindrical dentin cavity prepared in extracted human teeth. Among the tested bonding agents, only one material showed complete adaptation between the resin composite and the dentin cavity margin i.e. a dual-cured agent that contained 10-methacryloxydecyl dihydrogen phosphate (MDP). The contraction gap of the intermediate resin was significantly reduced by pretreatment with the experimental self-etching dentin primers containing Phenyl-P.
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Akira OKAMOTO, Kazuhito SEKIYA, Masayoshi FUKUSHIMA, Masaaki IWAKU
1993 Volume 12 Issue 2 Pages
225-232,276
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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This study evaluated the effect of various types of microfiller on the
in vivo wear resistance of composite resins. Experimental light-cured composites with two different microfiller systems were prepared: (1) 56wt% fine quartz filler, 21wt% organic filler and 3wt% colloidal silica filler (Hybrid type 1), and (2) 64wt% fine quartz filler and 21wt% colloidal silica filler (Hybrid type 2). The resin monomer consisted of 50wt% Bis-GMA and 50wt% TEGDMA. These materials were placed in 2mm diameter cylindrical cavities located in the OCA (occlusal contact area) or the CFA (contact free area) in cast gold-silver-palladium alloy full coverage crowns, which were temporarily set in a volunteer patient's mouth. The crowns were removed at monthly intervals for SEM observation. Hybrid type 1, which contained organic fillers, showed bulk fractures in the OCA, by the second month of the experiment. However, reinforcement of the resin matrix by dispersion of microfiller provided Hybrid type 2 with superior wear resistance for up to two months.
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Kunihiro HISATSUNE, Yasuhiro TANAKA, Koichi UDOH, Alaa M. EL-ARABY, Ke ...
1993 Volume 12 Issue 2 Pages
233-237,276
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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The electrical resistivity measurement to determine a critical temperature (
Tc) in a stoichiometric CuAu alloy is discussed on the dependence of the current used. The tempetrature was measured on two ways: With the thermocouple connected to the specimen by spot-welding, and with them separated. In the latter case, the greater the current, the lower the apparent
Tc because of the generation of Joule heat. To obtain a more precise
Tc, the current should be as small as possible or the thermocouple should be located as close as possible to the specimen. It is highly desirable for the thermocouple and the specimen to be welded together, if the effects of some contamination can be ignored in measuring system.
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Junzo TAKAHASHI, Jian-Zhong ZHANG, Masayuki OKAZAKI
1993 Volume 12 Issue 2 Pages
238-244,277
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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The effect of 12 different experimental compositions of phosphate-bonded SiO
2 investments was examined on cast pure titanium. The mold temperature was 600°C and the casting was conducted with an argon-arc melting and pressure casting machine. Castability was evaluated by the volume of casting porosity, which was calculated from the volume of wax pattern (15mm×15mm×1.5mm), the weight of cast plate and the specific density of pure titanium. The existence of inner casting porosities was confirmed by an X-ray non-destructive inspection instrument. Cast plates made in molds with cristobalite had significantly lower castability and higher surface hardness than those in molds with quartz as a refractory material. Cast plates in molds (quartz-cristobalite mixtures) with 20% binder had lower surface hardness and fewer casting porosities than those in molds with 10% binder.
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Junzo TAKAHASHI, Jian-Zhong ZHANG, Masayuki OKAZAKI
1993 Volume 12 Issue 2 Pages
245-252,277
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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Two types of patterns were tested for castability: 1) polyester mesh pattern (20mm×22mm with 100 open squares) and 2) 20mm×20mm wax plates 1.0 and 1.5mm in thickness. These materials were invested using a pre-arranged commercial phosphate-bonded investment for titanium. Three different types of casting machines were selected: 1) a pressure-type casting machine with separate melting and casting chambers, 2) a pressure-type casting machine with one chamber and 3) a centrifugal-type casting machine at 3000rpm. Pure titanium (>99.5%) was cast into the molds at a mold temperature of 100°C. The castability of mesh pattern was evaluated in terms of the number of cast segment, and the cast plate was evaluated using X-ray transparent images by a digital imaging technique. The centrifugal casting method showed the best castability among these three casting methods.
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Hironori TSUCHIYA, Kuniaki YAMADA, Mioko AKAGIRI, Katsushi TAJIMA, Tak ...
1993 Volume 12 Issue 2 Pages
253-258,277
Published: December 25, 1993
Released on J-STAGE: February 12, 2009
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Effect of glazing with an ultraviolet light-activated coating material on reduction of the leaching of methyl methacrylate and formaldehyde from denture acrylic resins was quantitatively evaluated. Disks prepared from auto-polymerized resins were painted with the material and radiated with ultraviolet light. The disks were immersed in artificial saliva and the concentrations of methyl methacrylate and formaldehyde leached were determined by high-performance liquid chromatography and flow injection analysis. Compared to untreated controls, the glaze significantly decreased concentrations of both leachable substances. Treatment with an ultraviolet light-activated coating material is effective in suppressing the leaching of methyl methacrylate and formaldehyde from acrylic resins as well as in smoothing the denture surfaces.
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