-
Shuji OHKAWA, Takayoshi MATSUKAWA, Tooru NAGASAWA, Hiromichi TSURU
1989 Volume 8 Issue 2 Pages
129-134,283
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The new resilient denture liner "M*" was evaluated for adhesion, color stability, surface texture, tissue response, deterioration and denture base stability, at periods of 1 month, 3 months and about 30 months after denture liner application. At the observation of approximately 30 months, the usage of 17 dentures had been discontinued within 2 years, and 6 dentures continued to be used. It could be considered that the main reasons why 17 dentures were discontinued were poor fitting caused by deterioration, and a decrease in the strength of the denture base caused by the denture liner lining. It was suggested that "M" was appropriate for long-term use (about 2 to 3 years), if patients faithfully practice denture cleaning, and if the strength of denture base is considered.
View full abstract
-
Takashi YAMASHITA, Kazuo ITOH, Sadao WAKUMOTO
1989 Volume 8 Issue 2 Pages
135-140,283
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The possibility for the clinical application of an experimental restorative material, which is composed of an Ag-Sn-Cu-Pd spherical alloy and a Ga-In-Sn-Ag alloy, was examined by observing periodic changes during class I restoration. In all of the restorations tested, the surface testure and the marginal integrity had deteriorated after a period of one year. Therefore, it was concluded that this metallic plastic filling material couldn't overcome physical and chemical stresses in the mouth, as a result, some improvement is required before this material can be substituted for the high copper amalgam.
View full abstract
-
Takeshi FUJIMITSU, Hiromasa KATO, Kazuo ITOH, Sadao WAKUMOTO
1989 Volume 8 Issue 2 Pages
141-146,284
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The cavity adaptation of marketed composite resins was evaluated by measuring the contraction gap width in a cylindrical dentin cavity. Cavity walls were cleaned with neutralized 0.5 M EDTA and treated with an aqueous solution of 35% HEMA and a dentin bonding agent. The inorganic filler content was measured by weighing specimens before and after burning.
When the composite which contained an inorganic component of less than 75 wt% was employed, a relatively low contraction value of less than 0.09% was obtained. On the other hand, for the composite with an inorganic component of more than 75 wt%, the gap values varied from 0.01 to 0.43%. However, using regression analysis, no statistically significant correlation was observed between the wall-to-wall polymerization contraction and the inorganic filler content.
View full abstract
-
Junichi NAKAZATO, Kazuo ITOH, Sadao WAKUMOTO
1989 Volume 8 Issue 2 Pages
147-154,284
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The physical properties of experimental visible light-activated resins containing dyestuff, which could be quickly discolored by irradiation was, evaluated by analyzing light absorbance characteristics and measuring micro Vickers hardness. The experimental resin, which was prepared by mixing equivalent weights of Bis-GMA and triethyleneglycol-dimethacrylate, was colored by one of three organic dye stuffs, and camphorquinone and dimethyl-p-toluidine were added to activate polymerization. In the tested materials, the experimental resins containing Methylene blue and Nile blue A were discolored quickly after the start of irradiation, and this was considered to be useful for dental practice because an overfilled margin could be easily identified. The Vickers hardness number of the base resin decreased slightly by a level of 6% by adding the dyestuff.
View full abstract
-
Tohru HAYAKAWA, Hiroshi ENDO, Akihisa NAGATSUKA, Kozo HORIE
1989 Volume 8 Issue 2 Pages
155-163,284
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The influences of the kinds and concentrations of the aldehydes in the primer on dentin adhesion were investigated. Moreover, the durability of the adhesion to the dentin treated with primer was examined by thermal cycling tests.
Among the aldehyde tested here, glutaraldehyde was effective in improving the adhesion to dentin etched with citric acid. When HEMA was substituted with ethanol, the bond strengths decreased. The relationship between the bond strength and the concentration of glutaraldehyde in the primer was studied. In the cases of phosphoric acid or citric acid etching, the bond strengths were affected by the concentration of glutaraldehyde in the primer. The bond strengths decreased after 2000 thermocycles in phosphoric acid etching.
View full abstract
-
Keiichi ISHIKAWA, Shigemitsu ITO, Yoshiaki HATA
1989 Volume 8 Issue 2 Pages
164-174,285
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The in vitro dentin permeability of the constituents of two types of conventional phosphoric acid etching agents which had different viscosities, and their pH changes after being permeated dentin were investigated. It was recognized that, even though the etching was for a short time (one minute) followed by rinsing, the etching agents were still detected in the dentinal tubules which had permeated through the dentin. The pH of the etching agents also increased (neutralized) after they had permeated through the dentin. The results of a qualitative and quantitative analysis of the constituents which had permeated through the dentin showed that, after one minute of etching, the concentrations of calcium, magnesium, zinc and phosphorus increased as compared with the non-etched control samples.
View full abstract
-
Osamu MIYAKAWA, Kouichi WATANABE, Seigo OKAWA, Syuji NAKANO, Masayoshi ...
1989 Volume 8 Issue 2 Pages
175-185,285
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The present study concerns the surface layered structure of the cast Ti. A commercial Ti was cast into a mold which was made of a phosphate-bonded Al2O3/SiO2 investment. Elemental analyses of the interfacial zone of the casting were made under an electron probe micro-analyzer.
The interfacial zone was composed of four layers: the outermost reaction or casting burn layer, the second layer of an O-and Al-stabilized α case, the third layer in which Si, P, O, and C were inhomogeneously concentrated, and the fourth layer which consisted of acicular or plate-like crystals. It was observed that the larger the cast volume and the higher the mold temperature, the thicker became each layer and the coarser became the acicular grains. Probably, the layered structure was formed through decomposition of reducible species in the burnout investment and diffusion of the resulting elements into the casting.
View full abstract
-
Part 2 Effect of Temperature and Residual Monomer on Impact Characteristics
Jun-ichi OKU
1989 Volume 8 Issue 2 Pages
186-193,285
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The temperature dependence of the impact strength, resilience, and toughness of the acrylic denture base resins on temperature changes was examined by using a modified impact testing machine. In addition, the creep properties and the residual monomer of their resins were measured; and, considering these properties, the impact characteristics of the denture base resins were discussed. With an increase in temperature, the impact properties of all the acrylic denture base resins tested decreased. Furthermore, there was an adequate correlation between the impact characteristics and the amount of the residual monomer. The coefficient of correlation was 0.92 for the impact strength, -0.95 for the resilience and 0.94 for the toughness. For the cold cured acrylic resins, both elastic moduli obtained by the impact test and by the creep test increased obviously according to an increase in the time which elapsed after polymerization.
View full abstract
-
Hisashi CHIGIRA, Atsufumi MANABE, Kazuo ITOH, Sadao WAKUMOTO, Tohru HA ...
1989 Volume 8 Issue 2 Pages
194-199,286
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The efficacy of pretreatment on the dentin surface with an aqueous solution of glyceryl methacrylate (GM) was examined by measuring the wall-to-wall polymerization contraction of a light activated composite in a cylindrical dentin cavity, and by measuring the tensile bond strength to a flat dentin surface. All of the tested dentin surfaces were cleaned with neutralized 0.5 M EDTA and treated with experimental primers, followed by a marketed dentin bonding agent and composite. The contraction gap formation of the composite was completely prevented by the application of the GM solution at concentrations of 25 and 35% in water. In contrast, half of the specimens treated with 35% HEMA and 35% HEMA containing 5% glutaraldehyde showed gap formation. Furthermore, a considerably high tensile bond strength of more than 18MPa was observed in the above described dentin bonding system.
View full abstract
-
The Effect of a Cleanser on Bonding
Toshio YANAGAWA, Kazuo ITOH, Sadao WAKUMOTO
1989 Volume 8 Issue 2 Pages
200-205,286
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The effect of the cavity cleanser on the efficacy of the experimental dentin bonding system, which was composed of dentin primer (aqueous solution of 35% hydroxyethyl methacrylate), a dentin bonding agent containing a functional monomer (4-methacryloxyethyl trimellitate anhydride), and an urethane dimetha. crylate based composite resin was examined. The bonding efficacy was evaluated by measuring the contraction gap in an experimental cavity which had both an enamel and a dentin cavity margin, and by measuring the tensile bond strength to the flat tooth surface. The whole cavity was cleaned by neutralized 0.5M EDTA or 10% citric acid containing 3% ferric chloride (10-3 solution) prior to the application of the dentin primer. For the control, the enamel and dentin were etched and cleaned with a 38% phosphoric acid gel and EDTA respectively. It was possible to conclude that the cavity cleanser employing the 10-3 solution for 5s was effective both in cleaning to the dentin and the enamel cavity walls.
View full abstract
-
Masayuki TAIRA, Kunio WAKASA, Masao YAMAKI, Nobuyuki TANAKA, Hideaki S ...
1989 Volume 8 Issue 2 Pages
206-214,287
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
Machinable ceramics that can be cut and even lathed have recently been developed in industry. As a first step in evaluating the feasibility of such ceramics in dentistry, eight machinable ceramics were examined for color using the Vita shade guide and a chroma-meter reflectance instrument. We discovered that the studied machinable ceramics varied significantly from the Vita shade guide by the color difference vector, delta E. These machinable ceramics appeared very white and strongly opaque due to their high brightness (L*) values. For intra-oral applications, we expect that L* values of machinable ceramics will be reduced by modification of their microstructures, including their matrix and dispersed phases, while their excellent machinability due to the cleavage of dispersed crystals should be retained.
View full abstract
-
Part 3 Impact Properties of Cross-linked Polymers
Jun-ichi OKU
1989 Volume 8 Issue 2 Pages
215-222,287
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The impact properties in acrylic denture base resins cross-linked using 6 diacrylates, such as ethylene glycol dimethacrylate (EDMA) and
p-divinyl benzene (DVB), were investigated and discussed. In addition, the creep characteristics of these cross-linked resins were examined and related with their impact characteristics. From these results, it was seen that both characteristics deteriorated with an increase in the diacrylate concentration from 2mol% to 10mol%. On the other hand, an increase in the repeated number (n) of (-CH
2-CH
2-O-)
n promoted a flexibility in the materials which resulted in a higher impact strength and toughness. But, there was no a significant difference in the resilience of these materials.
View full abstract
-
Hiroyuki ARIKAWA
1989 Volume 8 Issue 2 Pages
223-235,287
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
The dynamic shear moduli of human dentin and enamel were measured using a torsion pendulum over a temperature range from 23 to 150°C. For dentin, the shear modulus slightly increased for temperatures near 50 to 100°C, which was caused by a loss of free water. The peak in the loss tangent was observed near 75°C. The shear moduli at 37°C for sixty coronal dentin specimens ranged from 5.77×10
10 to 1.16×10
11dyn/cm
2. For enamel, the shear modulus and the loss tangent were markedly stable and independent of the temperature. The shear moduli at 37°C for forty specimens ranged from 2.35×10
11 to 4.48×10
11dyn/cm
2. Enamel had a modulus which was approximately three to five times higher, and a lower loss tangent than those of dentin.
For both dentin and enamel, there were no significant correlations between the values of the shear modulus and sex, age or tooth type.
View full abstract
-
Polyelectrolyte Behavior of the Cement Polymers Obtained by Potentiometric Titration in the Presence of Calcium Ion
Atsuko IIOKA, Yoshima ARAKI, Koichi MATSUDA, Hiroki OHNO
1989 Volume 8 Issue 2 Pages
236-242,288
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
Potentiomeric titration of aqueous solutions of polyacrylic acid and commercial polyelectrolyte cement polymers with sodium hydroxide solution was carried out in the presence of different concentrations of Ca
2+. Polyelectrolytes all behave as weak acids without the coexisting Ca
2+. However, in the presence of Ca
2+, in amounts over one-half of the equivalent amount to the carboxyl group in the polymer, they have a strong acid-like behavior. This means that the carboxyl groups in the polymer chain tend to react strongly with coexisting Ca
2+ as they are partially neutralized by the alkaline solution. This is also strong evidence supporting polyelectrolyte cement as an adhesion mechanism to tooth structure during cementation.
View full abstract
-
Koichi FUJII
1989 Volume 8 Issue 2 Pages
243-259,288
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
Observations were made of fractured surfaces caused by flexural and tensile fatigue tests made in polymethyl methacrylate denture base resins (PMMA). In addition, the changes in dynamic viscoelastic and tensile properties of the materials along with fatigue propagation were investigated.
In the tensile and flexural fatigue tests, both the fractured surfaces, which had striations on their surfaces and cracks near the fractured section, closely resembled each other in appearance. On the other hand, all of the tensile properties, such as elastic modulus, toughness and tensile strength, decreased with the increase of the number of stress cycles in the fatigue test. The storage modulus (E') of the material decreased gradually along with fatigue propagation over the whole range of temperatures tested. The loss modulus (E") and mechanical loss tangent (tanδ) increased slightly.
The fatigue limit of four commercial denture base resins varied widely from one product to another.
View full abstract
-
Tetsuya TAKAMATA, B. Keith Moore, Varoujan A Chalian
1989 Volume 8 Issue 2 Pages
260-270,289
Published: December 25, 1989
Released on J-STAGE: May 25, 2009
JOURNAL
FREE ACCESS
A number of authors have listed the following qualities as ideal for maxillofacial material: (1) original physical and mechanical properties comparable to the human tissue that they are replacing, (2) the ability to sustain these properties during service, (3) compatibility with human tissues and the adhesives used to adhere the prostheses to tissue, and (4) the quality of being easy to process and an insensitivity to processing variables. Clinical experience has indicated that there is frequent and for the replacement of maxillofacial appliances because of rapid discoloration in the service environment and/or degradation of the physical and dynamic properties of the base elastomer. Color stability in the service environment may be the most important factor in patient acceptance of the prosthesis. The results of this study suggested that aging rather than exposure to sunlight results in most of the color changes observed in the HTV and RTV base polymers studied.
View full abstract
