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Volume 22 (2003)
- Issue 4 Pages 425-
- Issue 3 Pages 227-
- Issue 2 Pages 115-
- Issue 1 Pages 1-
Volume 22, Issue 2
Displaying 1-9 of 9 articles from this issue
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Part 1. Comparison of Wet and Dry Technique after Short-term Stored in WaterSomchai URAPEPON, Akira OKAMOTO, Kazuyuki ISHIKAWA, Masaaki IWAKU2003 Volume 22 Issue 2 Pages 115-125
Published: 2003
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe study was to evaluate the marginal leakage of wet or dry dentin condition after restoration on short-term. In the study we used Photobond adhesive system and Single Bond adhesive system. The specimens were prepared from premolars. A class V cavity was prepared at the CEJ with a high-speed hand piece and #010 round diamond point. The cavity's walls and floors were etched with phosphoric acids of the test materials by wet and dry bonding techniques. The specimens were cross-sectioned longitudinally through the center of the cavities with a low speed diamond micro-cutter and polished with carbide paper (#600-1200) after storage in distilled water for 1 day, and silver nitrate staining. Specimens were viewed with EPMA for elemental distribution of calcium, nitrogen and silver on the resin-dentin interface.
The uptake of silver particles was less in samples treated with the wet-bonding technique when compared with dry-bonding technique. This in vitro study showed that bonding technique is important in establishing a seal along the restoration margins to control marginal leakage.View full abstractDownload PDF (2518K) -
Kenji ARITA, Milanita E. LUCAS, Mizuho NISHINO2003 Volume 22 Issue 2 Pages 126-136
Published: 2003
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThis present study investigated the effects of the addition of hydroxyapatite (HA) on the flexural strength and microstructure of conventional GIC, and its effect on the cement's initial flexural strength at different storage conditions. Specimens were fabricated by mixing HA in whisker or granule form into commercially prepared GIC, and these were subjected to a threepoint bending test and SEM observations. Some specimens were stored in different conditions from dry to wet for 15 minutes to an hour prior to testing. When compared to the control, specimens with 16-25% HA whiskers added at P/L 1.75 showed a significant increase in the flexural strength (p<0.05), and as well with 19% HA whiskers at P/L 1.75 (p<0.001) and 2.33 (p<0.05). A significant increase was also noted for those with 8-25% HA granules added at P/L's 1.75 (p<0.05), 2.5 (p<0.05) and 3.60 (p<0.01). The addition of HA hastens the development of early (15min, 1 hour) flexural strength of GIC in moist or wet conditions. These results indicate that the addition of HA, regardless of form, improve the flexural and microstructural properties of GIC.View full abstractDownload PDF (3565K) -
Part 5: Evaluation of the Bonding between Ag-Sn Particle and 4-META Coupling Agent of the Metal-resin CompositeSomchai URAPEPON, Kiyoshi KAKUTA, Hideo OGURA2003 Volume 22 Issue 2 Pages 137-145
Published: 2003
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThis study evaluated the oxide characteristics on a Ag-Sn particle surface modified by acid and heat in order to understand the bonding mechanism. Nine different Ag-Sn particles including standard Sn, SnO and SnO2 were evaluated by X-ray Photoelectron Spectroscopy (XPS). The particles were also used for preparing the composite to test the flexural properties following the ISO4049. A high correlation between flexural strength of the composites and Sn3d binding energy of their filler particles was found. Different oxide forms (SnO and SnO2) showed different adhesive abilities to bond with 4-META, regarding the difference in flexural strength of the composite. The highest flexural strength composite showed Sn3d binding energy of its filler at 486.4eV, which was the SnO binding area. This implies that SnO was responsible for a good bond between particle surface and 4-META coupling agent.View full abstractDownload PDF (821K) -
Kotaro YANARU, Kazunori YAMAGUCHI, Hiroshi KAKIGAWA, Yoshio KOZONO2003 Volume 22 Issue 2 Pages 146-159
Published: 2003
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSOrthodontic forces of Ni-Ti wires examined under the retrained condition on the dental arch model were evaluated with the changes in temperature and deflection. The tested specimens were a commercially available superelastic (W1) wire and two shape memory wires with their nominal Af points were 35°C (W2) and 40°C (W3), respectively. They showed typical superelastic hysteresis loops under the restraint condition at 40°C. The force levels were significantly larger than those generally obtained by simple three-bending test. The recovery forces in the plateau region at 1.0mm deflection were much larger than desired in the clinical guidelines around oral temperatures. In the shape memory wire W3, the recovery force rapidly decreased to zero by a small reduction of the deflection from its maximum. However, the wire again exerted the force with the remaining permanent deflection by temperature rising. It was small compared to the guidelines of desirable orthodontic force and seemed to be useful especially for the hypersensitive patients.View full abstractDownload PDF (1488K) -
Kenichi HAMADA, Fumiaki KAWANO, Kenzo ASAOKA2003 Volume 22 Issue 2 Pages 160-167
Published: 2003
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSNi-Ti shape memory alloy fiber embedded resin matrix composites were produced for evaluation of “smart denture”, a newly developing denture with the function to close its own crack. Their bending strength and shape recovery after instant crack repair was estimated. The embedded fibers did not decrease the bending strength of the composite after repair. The crack closure of the composites was performed well simply by heating at 80°C. Nevertheless, they showed apparent deflection after crack repair. The following two phenomena were supposed to be the main cause of it: the polymerization shrinkage of matrix resin with heating, and the coefficient of the thermal expansion mismatch between the fiber and the matrix. The embedded fibers could close the crack of the matrix with enough high accuracy for specimen repair, but they turned out to change the specimen shape after repair.View full abstractDownload PDF (745K) -
Yoko MAIKUMA, Kazuhiro USUI, Kouji ARAKI, Shiro MATAKI, Norimasa KUROS ...2003 Volume 22 Issue 2 Pages 168-179
Published: 2003
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe aim of this study was to evaluate the trial Teaching Robot for the development of a contact-type measuring apparatus for using directly in the oral cavity. A standard model was used to mimic the dentition by placing an arrangement of three bearing balls. The diameters of the balls were measured. A practical dentition model was used. The coordinates were measured on the top of the buccal cusp of the right and left first premolars and the distal contact points of the right and left first molars and the mesial contact point of the right incisor. The arch width and length were calculated. The diameters of the bearing balls and the widths and lengths of the dental arches were not significantly different from the results of the XYZAX G-800D. Therefore, we suggest that the trial Teaching Robot has superior efficiency for measurements in oral cavity.View full abstractDownload PDF (3344K) -
Xing Yan WANG, Koji MIYAZAKI, Wataru MOTOKAWA2003 Volume 22 Issue 2 Pages 180-190
Published: 2003
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe objective of the study was to evaluate the relationship between the fluoride concentration of the fluoride-releasing elastomers and the acquired acid resistance of human enamel. Four kinds of fluoride concentration of the experimental fluoride-releasing elastomers were 1.25, 2.5, 3.75 and 5.0wt%. An enamel block was cut into two smaller enamel blocks, one of which was set with an elastomer, the other as a control not set with elastomer. A plastic block that had the same shape as the small enamel block was also set with elastomer. Fluoride release and acid resistance tests were carried out. The mineral loss of the demineralized enamel was measured by microradiography. The results showed that the fluoride-releasing ability significantly increased with the increase of fluoride concentration in the elastomer (p<0.05). The acid resistance of the enamel appeared to be enhanced greatly, however, its change was not proportional to the fluoride concentration in the elastomers.View full abstractDownload PDF (2394K) -
Masafumi KIKUCHI, Masatoshi TAKAHASHI, Toru OKABE, Osamu OKUNO2003 Volume 22 Issue 2 Pages 191-205
Published: 2003
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSExperimental Ti-Ag alloys (5, 10, and 20mass% Ag) and Ti-Cu alloys (2, 5, and 10mass% Cu) were cast into magnesia molds using a dental casting machine, and their grindability was investigated. At the lowest grinding speed (500m⋅min-1), there were no statistical differences among the grindability values of the titanium and titanium alloys. The grindability of the alloys increased as the grinding speed increased. At the highest grinding speed (1500m⋅min-1), the grindability of the 20% Ag, 5% Cu, and 10% Cu alloys was significantly higher than that of titanium. It was found that alloying with silver or copper improved the grindability of titanium, particularly at a high speed. It appeared that the decrease in elongation caused by the precipitation of small amounts of intermetallic compounds primarily contributed to the favorable grindability of the experimental alloys.View full abstractDownload PDF (3319K) -
Seyfettin BAYDAS, Funda BAYINDIR, M. Samil AKYIL2003 Volume 22 Issue 2 Pages 206-213
Published: 2003
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSIn this study we determined the effect of different compression packing processes, investment materials (α hemihydrate and dental stone) and time on the dimensional accuracy of polymethyl metacrylate denture bases.
Square stainless steel plates (15mm×15mm×5mm) were prepared to make an acrylic resin specimen. The linear dimensional changes of acrylic resin were determined by measuring the distances of fix points. Measurements were made at 24 hours, 48 hours, 12 days and 30 days after setting with a digital compass. Dimensional changes of test specimens that were obtained with three different flasks and two press techniques were compared by univariate analysis. Measurements of the linear dimensions of specimens cured by different compression packing techniques suggested that differences existed. The time interval differences were not significant.
According to the results; flask and investment material types affect the dimensional accuracy of test specimens (p<0.05). The least dimensional change observed in the specimens was obtained with Type 1 flask-dental stone-manual press combinations.View full abstractDownload PDF (1956K)
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