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Volume 18 (1999)
- Issue 4 Pages 337-
- Issue 3 Pages 207-
- Issue 2 Pages 137-
- Issue 1 Pages 1-
Volume 18, Issue 4
Displaying 1-14 of 14 articles from this issue
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Masako UNEMORI, Yoko MATSUYA, Shigeki MATSUYA, Akane AKASHI, Keiko MIZ ...1999 Volume 18 Issue 4 Pages 337-346
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe effect of buffer agents incorporated in glutaraldehyde disinfectants on the surface quality of dental models was examined by the measurement of surface roughness, X-ray diffraction analysis and SEM observation. Seven experimental glutaraldehyde disinfectants were prepared using two buffer agents, potassium acetate alone or potassium acetate and sodium hydrogen carbonate in combination. Four kinds of sulfate -zinc, calcium, potassium and magnesium sulfatewere added to these disinfectants in order to accelerate the hydration of calcium sulfate hemihydrate. The impressions treated with the experimental disinfectants for 1h produced stone surfaces which had significantly lower surface roughness values than those treated with the commercial disinfectants (p<0.05). The X-ray diffraction analysis and SEM observation showed that these superior surfaces were produced as a result of significant reductions in the amount of residual calcium sulfate hemihydrate. Replacement of buffer agents in commercial glutaraldehyde disinfectants with chemicals such as those studied in the present study will improve the surface quality of dental stone.View full abstractDownload PDF (2570K) -
Toshiyuki ITOTA, Mimiko OKAMOTO, Kohei SATO, Satoshi NAKABO, Michihiro ...1999 Volume 18 Issue 4 Pages 347-353
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThis study investigated the release and recharge of fluoride by restorative materials. Resinmodified glass ionomers (RGIs), polyacid-modified composite resins (PMCRs) and resin composite containing fluoride were used for comparison of fluoride release. Non-fluoride-releasing resin composite was used as a control. The amounts of fluoride release from RGIs and PMCRs remarkably increased in the citrate-phosphate acid buffer compared with distilled water. The amounts of fluoride recharged in RGIs increased with the concentration of NaF solution, but those of PMCRs exposed to all concentrations of NaF solutions were less than 1.5ppm. Neither resin composite containing fluoride and non-fluoride-releasing resin composite gave any evidence of recharge. RGIs and PMCRs affected by acid buffer solution could not recharge much fluoride even if they were immersed in the 1000ppmF NaF solution. The results suggested that the matrix of RGIs and PMCRs functioned as a reservoir of fluoride, but the functions were lost by acid attack.View full abstractDownload PDF (683K) -
Tetsuya KOJIMA, Taiji SOHMURA, Kazumichi WAKABAYASHI, Mitsumasa NAGAO, ...1999 Volume 18 Issue 4 Pages 354-365
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSA new non-contact measurement system employing of a line laser and CCD camera was developed to rapidly measure maloccluded dental casts with large depth and high accuracy. In this system, the measuring interval along the line laser and the model scanning direction perpendicular to the line laser were both 0.2mm. By averaging the raw data through repetitious input and smoothing by local filtering, the noise was effectively decreased. Sub-pixel processing, which calculates the pixel position with the largest brightness within one pixel, improved the accuracy in the measurement to 22μm compared with 65μm before sub-pixel processing. Dental casts with malocclusion were measured with this system. The time and the depth for the measurement were about 10 minutes and 60mm, respectively. This was a vast improvement compared with our previous system employing a point laser. In the CG of the measured dental casts, smooth and detailed surface morphology were sufficiently reproduced, and recognition of the characteristic points in the cast could be accomplished with the accuracy of 30μm. This measurement system will be helpful to analyze the dental cast form with malocclusion in progress.View full abstractDownload PDF (4200K) -
Structural Changes of Alloy Surface by the High-temperature OxidationMasahiro SAGARA, Hiroki OHNO1999 Volume 18 Issue 4 Pages 366-384
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSTo achieve durable bonding with adhesive resin, the surface roughness and the kinds of oxides, respectively to increase mechanical retention to enhance the chemical affinity of adhesive monomer with the gold alloy, were regulated by high-temperature oxidation together with the addition of small amounts of base metals. Alloys containing 2mass% of Ni, In, or Cr with Cu were oxidized at 800°C for 20min in air, pickled in thioglycolic acid, and subsequently oxidized at 500°C for 10min in air. The morphology of the internal oxidation zone changed markedly according to the added base metals. Alhough the internal oxide particle composed of only Cu2O was removed by pickling, NiO, In2O3, and chromium oxides could not removed and remained on the alloy surface. The surface roughness was increased by addition of Ni, In, or Cr. Applying the present method can control the roughness and chemical states on a gold alloy surface to increase its adhesive ability with adhesive resins.View full abstractDownload PDF (10069K) -
Seiji BAN, Kenji MATSUO, Haruhiko IWASE, Kentaro KAIKAWA, Jiro HASEGAW ...1999 Volume 18 Issue 4 Pages 385-394
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSLeucite crystals having modified compositions from stoichiometry were prepared by the incorporation of Na+, Rb+, Cs+, Ca2+, Ba2+, and Sb3+ substituted for 5-50 at% of K+ in the leucite. The lattice parameters of the a- and c-axes of these tetragonal leucite were derived from the diffraction angles of (400) and (004) peaks due to tetragonal leucite, respectively. Both lattice parameters of the a- and c-axes of the leucites except Rb and Cs were slightly smaller than those of stoichiometric leucite. The lattice parameters of the a-axis of the leucites containing Rb and Cs were larger than those of stoichiometric leucite (p<0.01) and increased with the content of Rb and Cs. It was concluded that the crystal lattice of leucite was deformed by the incorporation of cations substituted for K and their variations mainly depend upon the kind of cation, namely ionic size and substitution site in the lattice.View full abstractDownload PDF (1340K) -
Takahiro NAKAZATO, Hidekazu TAKAHASHI, Masashi YAMAMOTO, Fumio NISHIMU ...1999 Volume 18 Issue 4 Pages 395-402
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe biaxial flexural strength and cyclic fatigue biaxial flexural strength of CAD/CAM ceramics polished with #220, 400, 600 and 1000 diamond pads were measured in an effort to determine the effect of surface roughness on fatigue behavior of dental ceramics. The surface roughness was improved after polishing with a smaller diamond grain pad. The flexural strengths of the specimens polished with #220, 400, 600 and 1000 diamond pad were 75.2, 76.6, 82.2, and 83.3 MPa, respectively; the fatigue flexural strength of those with #220, 400, 600 and 1000 were 53.0, 58.1, 60.0, and 61.5MPa, respectively. Both the flexural and fatigue flexural strengths increased with improvement of surface profile. These results suggest the importance of polishing of dental ceramics for not only the static strength but also the cyclic fatigue strength.View full abstractDownload PDF (2163K) -
Isao KAWASHIMA, Hiroki OHNO, Rohit SACHDEVA1999 Volume 18 Issue 4 Pages 403-412
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSSimple three point bending tests were performed on Ni-Ti wires with three different Af points (1°C, 13°C and 34°C) to clarify the relationship between Af temperature and load changes under constant deformation. Each wire was deformed at 37°C and then thermal changes were imposed by temperatures of 2°C or 60°C. The load changes with thermal changes from 37°C to 2°C or 60°C showed the same tendency on the wires with different Af points: In the loading stage, the load became lower than the initial level at 37°C and in the unloading stage, the load became higher than the initial load. The largest load change in the unloading stage was measured with the 13°C Af point wire. Care must be taken when handling Ni-Ti wire with an Af point of less than 1°C in order to prevent it from reaching the limit of critical stress of slip deformation when the temperature in the mouth rises to above 40°C.View full abstractDownload PDF (1378K) -
Maho FUKUIZUMI, Hiroshi KAKIGAWA, Yoshio KOZONO1999 Volume 18 Issue 4 Pages 413-424
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe characteristic temperature dependence of recovery force was evaluated for a Cu-containing Ni-Ti shape memory wire with the nominal Af point being 40°C. It exerted mild recovery force within the range of the proposed optimum force at the usual oral temperature. Larger forces were generated when it was heated to temperatures above Af: 40, 50 or 60°C. By subsequently cooling to temperatures below Af, the force decreased again, and vice versa. The excellent reversibility, reproducibility and durability of the recovery force were also confirmed. These results indicate that the shape memory wire may be a reasonable material for a new concept of intermittent orthodontic treatment, in which mild force will be applied to the tooth for most of the daily hours and the tooth movement will be intermittently accelerated by larger forces generated only when the patient has hot foods or drinks.View full abstractDownload PDF (1180K) -
Ayumi OHSAKI, Yohji IMAI1999 Volume 18 Issue 4 Pages 425-429
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe major components contained in commercial Bis-GMA monomer were isolated by thin layer chromatography (TLC) and identified by NMR and high resolution mass spectroscopy. In addition to the two major components already known (Bis-GMA and Iso-bis-GMA), an unknown hydrophilic third major component was isolated and identified as 2, 2-[4-(2-hydroxy-3-methacryloyloxy-1-propoxy)-4'-(2, 3-dihydroxy-1-propoxy)] diphenylpropane. This compound was designated as BIS-GMA-H, because it has a structure of Bis-GMA with one of which methacrylic ester bond hydrolyzed.View full abstractDownload PDF (445K) -
Koichi FUJII, Keiichi MIURA, Ken-ichi OMORI, Hiroyuki ARIKAWA, Takahit ...1999 Volume 18 Issue 4 Pages 430-436
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSTo elucidate the effects of thermal cycling on the viscoelastic properties of four commercial resins for crown and bridge, dynamic shear modulus (G'), mechanical loss tangent (tanδ), Knoop hardness, water sorption and appearance of specimen surfaces before and after thermal cycling test were determined. The changes of G' and tanδ for two materials were insignificant with increased repetitions of thermal cycling. Those of the other two materials were statistically significant: in particular, G' at temperatures above 60°C was inclined to increase slightly and tanδ decreased considerably. While the Knoop hardness of the materials was a little decreased over a number of 75000 thermal cycles, the water sorption almost attained an equilibrium in uptake after 14000 thermal cycles. Furthermore, cracks on the specimen surface were observed after 37500 to 75000 thermal cycles.
From these results, the deterioration of materials was observed as damage to the specimen surface. Moreover, it could be presumed that the materials would be further polymerized during the period of thermal cycling.View full abstractDownload PDF (1290K) -
Adhesion of a New Commercial Self-etching/Self-priming Bonding Resin to Human Caries-infected DentinTakeshi KIMOCHI, Masahiro YOSHIYAMA, Akihisa URAYAMA, Takashi MATSUO1999 Volume 18 Issue 4 Pages 437-443
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSWe have examined the adhesive properties of a new commercial self-etching/self-priming bonding resin (Unifil Bond, UB) to normal and caries-infected dentin of human extracted molars using scanning electron microscopy (SEM) and a micto-tensile bonding strength (MTBS) test. In this study, 7 human extracted molars with moderate occlusal caries were used, and flat surfaces including occlusal dentin caries were prepared from the teeth. After the application of UB to the surfaces, a composite resin was built up, and subjected to the measurement of MTBS and SEM observation of the interfacial morphology between UB and dentin. The MTBS of UB to normal dentin was 33.4MPa, but that to caries-infected dentin was 11.0MPa. There was a significant difference between the MTBS to normal and carious dentin. SEM observation revealed that the typical hybrid layer was not formed in caries-infected dentin. These results suggested that resin infiltration into caries-infected dentin was not sufficient to allow perfect sealing of the restoration.View full abstractDownload PDF (2975K) -
Noriyuki SATOH, Yasuo UEDA, Takumi YORIMOTO, Hideki AITA, Shingo MATSU ...1999 Volume 18 Issue 4 Pages 444-452
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSUsing porcelain and resin-mixed composites as experimental materials, cubic polymerized composites were prepared by the accumulation of thin slices cured by laser scanning. The composites were then fired, and bulk ceramic bodies were made. The optimal firing conditions of polymerized composites and firing shrinkage were investigated. The results showed that cubic ceramic bodies in a form homologous to that before firing could be reproduced. The volume shrinkage of fired ceramic bodies consisting of 1g of ceramic powders and 0.3g of epoxy resin was about 30% under all firing conditions, and there were no significant differences between specimens. It was suggested that with further research and development, three-dimensional forms for clinical use in dentistry could be manufactured by the proposed method.View full abstractDownload PDF (4276K) -
Yasuhiro TORII, Kousuke ITOU, Toshiyuki ITOTA, Kazuhiro HAMA, Norifumi ...1999 Volume 18 Issue 4 Pages 453-461
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSWe investigated the influence of filler content and gap dimension on the wear resistance of composite luting cement around CAD/CAM ceramic inlay restorations. Experimental hybrid dualcured composite luting cements containing 60, 70, 72, 74 and 80wt% of silanated barium-silica fillers were used for cementing CAD/CAM ceramic inlay into the cavity. The specimens involving inlay-cement-tooth interfaces were subjected to a three-body wear test. The relation between the interfacial gap dimension and wear loss was also investigated using 60, 70 and 80wt% filled cements. The cements containing more than 70wt% filler presented significantly higher wear resistance than 60wt% filled cement. There was a positive linear relationship between gap dimension and wear loss, and the inclination of the regression line decreased with increasing filler content. These results indicated that the higher filler content of the cement increased the wear resistance and this desirable influence appeared more remarkably in the wider horizontal gap dimension.View full abstractDownload PDF (1464K) -
Susumu HIRANO, Masaaki OZAWA, Iwao IKEJIMA, Manabu KOMORIYAMA, Atsushi ...1999 Volume 18 Issue 4 Pages 462-466
Published: 1999
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSA small experimental impression tray was fabricated with a NiTi shape memory alloy plate After recovery of the shape memory effect, the upper rims of the tray holding the impression were opened to some extent, the resistance during removal of the model from the impression was significantly decreased compared to a commercially available tray and the tray before recovery of the shape memory effect. The pull-out force of the model from the impression was 23.5(0.2)N for the commercially available tray, 23.5(3.9)N for the experimental tray before recovery of the shape memory effect and 14.7(4.0)N after recovery of the shape memory effect (heated for 15min at 70°C). Therefore the tray should be useful in teeth fracture free modeling.View full abstractDownload PDF (1680K)
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