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Volume 21 (2002)
- Issue 4 Pages 285-
- Issue 3 Pages 225-
- Issue 2 Pages 73-
- Issue 1 Pages 1-
Volume 21, Issue 2
Displaying 1-12 of 12 articles from this issue
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Jia LIU, Masayuki HATTORI, Koji HASEGAWA, Masao YOSHINARI, Eiji KAWADA ...2002 Volume 21 Issue 2 Pages 73-82
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSTo investigate the mechanical properties of root dentin and to further clarify the cause of vertical root fracture (VRF), this study evaluated the effect of tubule orientation (parallel, perpendicular and oblique to the cross-section of dumbbell specimens in microtensile tests) and dentin location (cervical, middle, and apical location of the root) on the microtensile strength of bovine root dentin. Each specimen was stressed in tension at a crosshead speed of 1.0mm/min. The results of the microtensile strength measurements were statistically analyzed with one-way ANOVA and the Fisher PLSD. The oblique group (95.18±23.80MPa) was significantly (p<0.01) higher than the parallel group (38.93±5.28MPa) or the perpendicular group (32.64±4.69MPa). There were no significant differences among the different dentin locations within the parallel group (p>0.05). It was clarified that the VRF occurs frequently in practical situations due to the tubule orientation of root dentin.View full abstractDownload PDF (1811K) -
Masaharu NAKAGAWA, Shigeki MATSUYA, Koichi UDOH2002 Volume 21 Issue 2 Pages 83-92
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe effects of dissolved-oxygen concentration and fluoride concentration on the corrosion behaviors of commercial pure titanium, Ti-6Al-4V and Ti-6Al-7Nb alloys and experimentally produced Ti-0.2Pd and Ti-0.5Pt alloys were examined using the corrosion potential measurements. The amount of dissolved Ti was analyzed by inductively coupled plasma mass spectroscopy. A decrease in the dissolved-oxygen concentration tended to reduce the corrosion resistance of Ti and Ti alloys. If there was no fluoride, however, corrosion did not occur. Under low dissolved-oxygen conditions, the corrosion of pure Ti and Ti-6Al-4V and Ti-6Al-7Nb alloys might easily take place in the presence of small amounts of fluoride. They were corroded by half or less of the fluoride concentrations in commercial dentifrices. The Ti-0.2Pd and Ti-0.5Pt alloys did not corrode more, even under the low dissolved-oxygen conditions and a fluoridecontaining environment, than pure Ti and Ti-6Al-4V and Ti-6Al-7Nb alloys. These alloys are expected to be useful as new Ti alloys with high corrosion resistance in dental use.View full abstractDownload PDF (956K) -
Yuki NAGAMATSU, Kerr-Kong CHEN, Kiyoshi TAJIMA, Hiroshi KAKIGAWA, Yosh ...2002 Volume 21 Issue 2 Pages 93-104
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSElectrolyzed strong and weak acid waters have been widely used for sterilization in clinical dentistry because of their excellent bactericidal activities. Electrolyzed neutral water was recently developed with a new concept of long-term good durability in addition to the excellent bactericidal activity similar to acid waters. The present study, evaluated the storage life of this water compared with the acid waters in terms of the changes in pH, oxidation-reduction potential (ORP), residual chlorine and bactericidal activity under several conditions using Staphylococcus aureus 209P. The strong acid water showed a rapid deterioration of its bactericidal activity. The weak acid and neutral waters exhibited excellent durability. Although all the bacteria were annihilated by the contact with the waters even stored for 40 days in the uncapped bottle, the neutral water was superior in further long-term duration.View full abstractDownload PDF (1643K) -
Yasuhiro TANIMOTO, Tsuyoshi NISHIWAKI, Norihiro NISHIYAMA, Kimiya NEMO ...2002 Volume 21 Issue 2 Pages 105-117
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe purpose of this study was to propose a new numerical modeling of the glass fiber cloth reinforced denture base resin (GFRP). The proposed model is constructed with an isotropic shell, beam and orthotropic shell elements representing the outmost resin, interlaminar resin and glass fiber cloth, respectively. The proposed model was applied to the failure progress analysis under three-point bending conditions, the validity of the numerical model was checked through comparisons with experimental results. The failure progress behaviors involving the local failures, such as interlaminar delamination and resin failure, could be simulated using the numerical model for analyzing the failure progress of GFRP. It is concluded that the model was effective for the failure progress analysis of GFRP.View full abstractDownload PDF (1721K) -
Masato NISHIJIMA, Yoshiya HASHIMOTO, Masaaki NAKAMURA2002 Volume 21 Issue 2 Pages 118-132
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe estrogenic activity of phthalate esters for dental use as plasticizers was concerned. To study the feasibility of candidate chemicals for phthalate tissue conditioners, three candidate plasticizers, di-n-butyl sebacate, acetyl tributyl citrate and tri-n-butyl phosphate together with conventional plasticizers were examined for estrogenic activity and cytotoxicity using three estrogenicity assays, human gingival fibroblasts and living skin equivalent. None of the three candidate plasticizers showed any estrogenic activity at the concentrations tested by the three assays. Di-n-butyl sebacate, acetyl tributyl citrate and their prototype tissue conditioners were weakly to negligibly cytotoxic, while tri-n-butyl phosphate and its prototype tissue conditioner yielded the strongest cytotoxicity among the six plasticizers tested. In particular, the cytotoxicities of di-n-butyl sebacate and its prototype tissue conditioners were significantly weaker than the others and the conventional plasticizers. The results suggested that di-n-butyl sebacate and acetyl tributyl citrate could be candidate chemicals for phthalate ester-free tissue conditioners.View full abstractDownload PDF (1540K) -
Tatuji SAKAI, Shoji TAKEDA, Masaaki NAKAMURA2002 Volume 21 Issue 2 Pages 133-146
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSEffects of fifteen particulate objects, fourteen metals and one non-metal on cell viability of osteoblast-like cells were studied in vitro, to determine whether an adverse effect on cells could be induced by the particulate form or soluble ions. The Al, Ti, Zr, Nb, Ta, Cr, Mo, and Fe particulates depressed cell viability at higher particulate concentrations, but their extracts yielded no effect on cells except for Mo. On the other hand, little difference in cell viability between particulates and extracts was observed for Cu, Si, V, W, and Co. However, Mn and Ni yielded more adverse effects on cells in the case of the particulates than the extracts. These findings suggested that the effects of particulates on cells depended upon the direct effects of contact between particulates and cells, the indirect effects of dissolved ions and the kinds of particulate elements.View full abstractDownload PDF (1497K) -
Hiroyuki ARIKAWA, Takahito KANIE, Koichi FUJII, Keita FUKUI, Tetsuya H ...2002 Volume 21 Issue 2 Pages 147-155
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe light-attenuating effects of enamel on the mechanical properties of light-cured composite resins were evaluated using simple experimental filters. Three filters were designed to simulate the light transmittance characteristics of 0.5, 1.0, and 1.5mm thick human enamel. The Knoop hardness numbers (KHN) and the elastic modulus in transverse tests for twelve shades of three light-cured composite resins were examined. These resins were cured either using direct irradiation with a light source, or indirect irradiation through one of the filters. The attenuations of light by 0.5, 1.0, and 1.5mm thick enamel filter were 45%, 67% and 81% in the 430nm-550nm wavelength region, respectively. For all materials, KHN and the elastic modulus of specimens irradiated through filters were significantly lower than those irradiated directly. The results suggest that the light-attenuating effect of enamel reduces the mechanical properties of light-cured resin, and may cause poor clinical longevity of restorations.View full abstractDownload PDF (1611K) -
Yoshinori KADOMA2002 Volume 21 Issue 2 Pages 156-169
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSTo develop a new surface treatment agent which improves the bond strength of adhesive resin to both non-precious and precious metals, experimental treatment agents containing both an adhesive bonding promoter for precious metals and one for non-precious metals were prepared by dissolving epithioalkyl methacrylate (EP3MA or EP8MA) and 10-methacryloyloxydecyl dihydrogen phosphate (MDP) in acetone. The surfaces of dental metals were treated by the treatment agents and metal specimens were butt-jointed together with MMA-PMMA resins. After 2, 000 thermal cyclings in water at temperatures of 4 and 60°C, tensile bond strengths were measured. The effectiveness of surface treatments was evaluated by tensile bond strengths and microscopic failure mode analysis after the tensile test.
The combined treatment of EP3MA-MDP or EP8MA-MDP was used effectively for nonprecious metals as well as precious metals, and was shown to be extremely effective compared with the single treatment of EP3MA, EP8MA, or MDP.View full abstractDownload PDF (1532K) -
Masayuki KON, Luciana M. HIRAKATA, Youji MIYAMOTO, Fumiaki KAWANO, Ken ...2002 Volume 21 Issue 2 Pages 170-180
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe purpose of this study was to examine or characterize the surface layer of a calcium phosphate ceramic with a gradual compositional change from α-tricalcium phosphate (α-TCP) on the surface to hydroxyapatite (HAP) on the inside. The surface of a dense HAP ceramic was acid-treated for 1 hour with orthophosphoric acid (H3PO4) solutions of several concentrations (0.5, 1.0 and 5.0mol/L) or a buffered solution (pH 4.0) consisting of phosphate solutions. After acid treatment, specimens were heat-treated at 1, 250°C for 1 hour. X-ray photoelectron spectroscopy revealed that the compositional gradient layer could be modified on the surface of the HAP ceramic with all acid and heat treatments, and that 5.0mol/L H3PO4 solution and heat treatments had a maximal thickness of approximately 2μm for the surface-modified layer. It was confirmed that the outermost layer of HAP ceramics modified with the treatments, except 5.0mol/L H3PO4 solution, showed a compound such α-TCP.View full abstractDownload PDF (2112K) -
Part 4 Flexural Strength and Flexural Modulus of Metal-resin Composite using Ag-In Alloy Particles as FillerKiyoshi KAKUTA, Somchai URAPEPON, Yukio MIYAGAWA, Hideo OGURA, Masahik ...2002 Volume 21 Issue 2 Pages 181-190
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe flexural strength and flexural modulus of an experimental metal-resin composite, which used Ag-In alloy particle as the filler, were evaluated. The effect of acid treatment and heat treatment on the Ag-In alloy particle was investigated.
The flexural strength of the experimental metal-resin composites ranged from 65.5MPa to 91.0MPa. The flexural strength of the metal-resin composite increased with the temperature of the heat treatment until 350°C, but its effect varied with the concentrations of HCl of the acid treatment. A metal-resin composite, which used acid-treated and 350°C heat-treated Ag-In alloy fillers, matched the requirement of strength of ISO 4049.
The average of flexural modulus of the experimental metal-resin composite was 9.1GPa. The flexural modulus of the metal-resin composite did not vary with the treatment conditions of the metal filler. The flexural modulus of a metal-resin composite, which used Ag-In alloy particle as the filler, was lower than that of Ag-Sn alloy metal-resin composite, which was reported previously. However, the flexural strength of the Ag-In alloy metal-resin composite was similar to that of Ag-Sn alloy metal-resin composite. We can control a flexural modulus of a metal-resin composite without decreasing flexural strength by choosing filler materials.View full abstractDownload PDF (952K) -
Part 2. Effect of Titanium Content on the Dimensional Change of the InvestmentAkira NAKAI2002 Volume 21 Issue 2 Pages 191-199
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSIn the present study, titanium powder was chosen as an expanding agent of an experimentally prepared resin-bonded calsia investment. The effect of Ti content on the dimensional change was investigated. In addition, the effects of the heating rate and heating temperature on the dimensional change of the investment were investigated during setting and after heating. The expansion increased with Ti content and the highest expansion (1.57%±0.58) was obtained at 10mass% Ti. The highest expansion was obtained at 900°C for 30min heating and was independent of the heating rate. These findings mean that the titanium powder in the calcia investment oxidized sufficiently at that heating condition. It was found that the developed resin-bonded calcia investment was able to compensate for casting shrinkage of pure titanium by adding some Ti powder to the investment.View full abstractDownload PDF (900K) -
Funda BAYINDIR, Nuran YANIKOGLU, Zeynep DUYMUS2002 Volume 21 Issue 2 Pages 200-209
Published: 2002
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSPresent study the relation between pH, thermal changes and dimensional stability during setting of irreversible hydrocolloid impression materials was investigated. Ten specimens of each product were prepared for different measurements: Thermal, pH changes and dimensional stability (mass and linear). Thermal and pH readings for 20min and dimensional measurements for a 2hr period were taken after mixing. It was observed that pH and thermal values changed in relation to different materials, while they did not change with the time according to variance analysis results. On the other hand, dimensional stability showed significant differences with time in all tested impression materials.
A continuous pH change was observed with the time of gelation in all irreversible hydrocolloid impression materials tested. Dimensional stability also showed significant differences with time in all impression material and as a result hydrocolloids with a high pH showed better dimensional stability than those with a low pH.View full abstractDownload PDF (887K)
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