All issues
Volume 21 (2002)
- Issue 4 Pages 285-
- Issue 3 Pages 225-
- Issue 2 Pages 73-
- Issue 1 Pages 1-
Volume 21, Issue 4
Displaying 1-11 of 11 articles from this issue
- |<
- <
- 1
- >
- >|
-
Linlin HAN, Edward CV, Mu LI, Kazuaki NIWANO, Neamat AB, Akira OKAMOTO ...2002 Volume 21 Issue 4 Pages 285-295
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThis study evaluated fluoride-release and recharging with the fluoride mouth rinsing technique on fluoridated materials. Three fluoride containing materials and one non-fluoride containing composite resin were used for this study. Samples for each material consisted of 15 discs, 9mm diameter with a thickness of 1mm. Initial fluoride release was assessed over a 60-day period. After that, 15 discs for each material were divided into 3 groups: distilled water group, 450-ppm and 900-ppm mouth rinsing groups. Fluoride release increased in combination with fluoride mouth rinse, and fluoride was higher in the 900-ppm group than the 450-ppm group. Moreover, S-PRG or F-PRG fillers materials released fluoride in higher than fluoroaluminosilicate glass fillers materials. In addition fluoride release from control samples was not observed. Therefore, only fluoride release material takes up fluoride. The findings of the present investigation suggest that the rate of fluoride release was different for each material, because they contained different function fillers. The results showed the importance of the fluoride mouth rinsing technique for fluoride-releasing restorative materials for the prevention of secondary caries.View full abstractDownload PDF (2044K) -
Kenji FUJIKAWA, Akiyoshi SUGAWARA, Kaoru KUSAMA, Minoru NISHIYAMA, Sei ...2002 Volume 21 Issue 4 Pages 296-305
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSOur previous histopathological study showed that the augmentation block, prepared from a calcium phosphate cement (CPC) mixed with H2O at powder to liquid ratio of 5g/mL, placed on the alveolar bone ridge, was gradually replaced by natural bone. In the present study, fluorescent labeling analysis (FLA) and electron probe microanalysis (EPMA) were performed on the same surgical site of the above histopathological study. Fluorescent labeling agents, that would be incorporated into newly formed mineralized tissues, were injected into dogs intramuscularly twice a week during the 3 week period that ended 1 week before sacrifice. The specimens obtained from the block were subjected to FLA for assessing the extent of new bone formation and to EPMA for measuring the elemental (Ca, P, Mg) distributions. FLA results showed the presence of newly formed bone at 1 month after surgery. EPMA results showed that the elemental distributions in the augmentation site were similar to those of the residual bone area at 6 months after surgery. FLA and EPMA examinations also indicated that the implants were surrounded and fixed by natural bone chronologically. A CPC augmentation block is clearly useful for alveolar ridge augmentation and osteointegrated implant fixation.View full abstractDownload PDF (2553K) -
Seiji BAN, Akira KAMIYA, Tsutomu SONODA2002 Volume 21 Issue 4 Pages 306-313
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe depths of calcium-ion incorporation into a commercially pure titanium and an experimental β-type titanium alloy were determined using Auger electron spectroscopy. After the electrochemical deposition of apatite, new compositional gradients appeared in the profiles in which the Ca and P concentrations gradually decreased as a function of the depth up to 6-8nm. The relative concentration of Ca in the outermost layer was higher than that of P. On the other hand, after the soaking in a simulated body fluid, the relative concentration of P was higher than that of Ca in the outermost layer. These results suggested that Ca ions were well incorporated into the outermost oxide layer of titanium accompanied by the electrochemical apatite-deposition on its surface.View full abstractDownload PDF (806K) -
I. Comparison of TBB and Other Initiators in the Polymerization of PMMA/MMA ResinChiemi HIRABAYASHI, Yohji IMAI2002 Volume 21 Issue 4 Pages 314-321
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSPolymerization characteristics of poly (methyl methacrylate) (PMMA)/(methyl methacrylate) (MMA) resin initiated by tributylborane (TBB) were compared with those by benzoyl peroxide (BPO)/N, N-dimethyl-p-toluidine and camphorquinone (CQ)/N, N-dimethylaminoethyl methacrylate from the aspects of temporal changes of residual MMA and molecular weight up to 4 weeks at 37°C. Residual MMA 30min after polymerization decreased from 8.15% for TBB resin, 8.39% for the BPO resin, and 9.19% for the CQ resin to 0.48%, 3.54%, and 6.79%, respectively, after 4 weeks. The molecular weights at 30min and 4 weeks after polymerization were 409×103 and 247×103 for TBB resin, 297×103 and 282×103 for the BPO resin, and 267×103 and 231×103 for the CQ resin, respectively. The present results revealed that the TBB-initiated polymerization had unique and different characteristics compared with those initiated by the other common initiators: (1) The decrease in residual MMA was fast, sustained for a long time and resulted in very low value; (2) high molecular weight PMMA was formed first and then decreased with time.View full abstractDownload PDF (824K) -
Shigeyuki TAKASHIBA, Zutai ZHANG, Yukimichi TAMAKI2002 Volume 21 Issue 4 Pages 322-331
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSIn our previous study, we investigated ammonia-free phosphate-bonded investments using Mg(H2PO4)2 powder. The purpose of the present study was to attempt usage of 50wt% Mg(H2PO4)2 solution instead of powder. Magnesium oxide (MgO) was prepared as a binder and cristobalite was selected as a refractory. After arranging six kinds of experimental investments (A-F) with different cristobalite/MgO ratios, the fundamental properties of the dental investments were examined. The properties of the molds were influenced by the amount of MgO. Decreases in MgO showed lower mold strengths, longer setting time and larger setting expansion. According to XRD analysis, the peaks of MgH(PO4)3⋅3H2O newly formed, cristobalite and MgO were detected in the A set, but MgO peaks in F set were reduced. On the other hand, the surface of F was entirely covered by phosphorus. From these results, it was found that the usage of Mg(H2PO4)2 solution was possible for ammonia-free investments.View full abstractDownload PDF (2769K) -
Masahiko YAMANAKA, Shin-ichi GOTO, Pornkiat CHURNJITAPIROM, Hideo OGUR ...2002 Volume 21 Issue 4 Pages 332-342
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSTen 35Ag-30Pd-20Au-15Cu alloys containing 0.00, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 2.00, 4.00, or 6.00% Ga were experimentally prepared to investigate the effect of Ga on their mechanical properties in addition to their use for denture frameworks, connectors and clasps. The effect of Ga addition on the mechanical properties was marked with a significant increase in the tensile strength, 0.2% off-set proof stress (proof stress) and Vickers hardness observed at low Ga contents (0.25-2.00%). On the other hand, the elongation significantly decreased with the addition of Ga at all contents used in this study. The tensile strength, proof stress and Vickers hardness of the 35Ag-30Pd-20Au-15Cu alloys containing 0.25-2.00% Ga were in the range of 809-957MPa, 669-857MPa and 260-301MPa, respectively. These values are similar to those of Co-Cr alloys, suggesting that 0.25-2.00% Ga alloys can be used for denture frameworks, clasps and connectors.View full abstractDownload PDF (5662K) -
Satoshi INOUE, Yasuhiro MURATA, Hidehiko SANO, Toshiaki KASHIWADA2002 Volume 21 Issue 4 Pages 343-354
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe aim of this study was to investigate the bond strength between indirect resin core-buildup and dentin treated with or without hypochlorite (NaOCl) gel. The post-space was made in five extracted human molars with obturated root canals, and the indirect resin core was produced on a gypsum model. Then, the dentin surface was treated with/without NaOCl, followed by luting of the resin core into the cavity. After storage for 24h in 37°C water, the specimens were sectioned for measuring bond strength to the root and coronal dentin, and were subjected to micro-tensile bond strength (MTBS) testing. Two-way ANOVA showed that significant differences in MTBS were revealed for both factors of NaOCl treatment and dentin region. It is concluded that, for indirect resin core-buildup, the proper use of the NaOCl gel to dentin could increase the bond strength.View full abstractDownload PDF (4179K) -
Yutaka TAMURA, Atsuro YOKOYAMA, Fumio WATARI, Takao KAWASAKI2002 Volume 21 Issue 4 Pages 355-372
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSCorrosion, other related properties and biocompatibility of surface nitrided titanium were investigated to examine its possible use as an abrasion resistant implant material. The nitrided layer about 2μm thick composed of TiN and Ti2N was formed on titanium by a gas nitriding method. The dissolved amount of titanium ion in SBF was as low as the detection limit of ICP, and that in the 1% lactic acid showed no significant difference from titanium. The tissue reaction of the cylindrical implant in soft tissue of rats showed no inflammation, and fine particles of 1μm induced phagocytosis, which was similar to titanium. The implantation in the femor showed the new bone formed in direct contact with implants. All the results suggested that the wettability, corrosion resistance, S. mutans adhesion and biocompatibility were nearly equivalent to those of titanium. The surface of nitrided titanium was promising, with biocompatibility comparable with titanium, as an implant material such as for an abutment part of a dental implant, which requires high abrasion resistance.View full abstractDownload PDF (5680K) -
En-Sheng KEH, Iwao HAYAKAWA, Hidekazu TAKAHASHI, Akihiko WATANABE, Yas ...2002 Volume 21 Issue 4 Pages 373-382
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSSelf-curing dental resins are always manipulated in the presence of curing inhibitory factors such as oxygen, hydroquinone, water and another contaminants such as saliva and blood. The purpose of this study was to elucidate the effects of eliminating these curing inhibitory factors on resin properties. Several clinically relevant characteristics of an experimental resin cured in the absence of inhibitory factors (purified group) were determined and compared with the resin cured conventionally (control group). The purified group showed a significantly shorter induction period and higher reaction exotherm. It also showed significantly higher tensile strength and lower strain to failure. With regard to the amount of residual monomer, fracture toughness and fatigue strength the improvements were not significant. These findings suggest that the polymerization outcomes and mechanical properties of the purified group resin can be improved in general. Dental clinicians should pay attention to the storage and curing environments while manipulating the self-curing resin.View full abstractDownload PDF (2428K) -
Yasuhiro YOSHIDA, Kenichi SHIRAI, Hideaki SHINTANI, Masayuki OKAZAKI, ...2002 Volume 21 Issue 4 Pages 383-395
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSFiller-matrix coupling determines, to a large extent, the mechanical strength and clinical longevity of dental composites. The aim of this study was to examine how far a methodology to decontaminate filler prior to silanization may improve aesthetic performance in addition to physico-mechanical properties such as degradation resistance. It was reported that filler particles are surrounded and wrapped by a film that consists of multiple layers of silane molecules. X-ray photoelectron spectroscopy, however, revealed that silanization of filler particles largely depended upon siloxane bridge (Si-O-Si) formation between the silica surface and the silane molecule rather than on intermolecular bonding between adjacent silane molecules. In this study, we showed that filler decontamination resulted in a higher translucency, thereby providing a better aesthetic potential. In addition, experimental composites produced following presilanization decontamination of filler revealed a higher Vickers hardness value and a diametral tensile strength that was resistant to degradation by thermo-cycling.View full abstractDownload PDF (1582K) -
Choong-Bo JUNG, Hyung-Il KIM, Kyo-Han KIM, Yong Hoon KWON2002 Volume 21 Issue 4 Pages 396-403
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe surface modifications and the coefficient of thermal expansion of compomers after treatment with a 30% hydrogen peroxide bleaching agent were investigated. Three compomers (Compoglass F, Elan and F2000) were nonbleached and bleached for 1 and 3 days. The surface modification and the coefficient of thermal expansion of each bleached compomer were evaluated using a scanning electron microscope and a thermomechanical analyzer, respectively. As a result, Compoglass F and Elan showed slight surface degradation, whereas F2000 showed many cracks on its surface and these cracks were not observed in Compoglass F and Elan. Bleached Elan and F2000 has changed to the extent where their the coefficient of thermal expansion increased compared with those of nonbleached specimens. In addition, bleached compomers showed a strong inverse correlation between the coefficient of thermal expansion and the volume percent of filler.View full abstractDownload PDF (2503K)
- |<
- <
- 1
- >
- >|