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Volume 19 (2000)
- Issue 4 Pages 329-
- Issue 3 Pages 211-
- Issue 2 Pages 99-
- Issue 1 Pages 1-
Volume 19, Issue 1
Displaying 1-8 of 8 articles from this issue
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Maud BERGMAN2000 Volume 19 Issue 1 Pages 1-9
Published: 2000
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSDental treatment usually involves a wide range of materials which continue to grow in number and complexity. During the last decade there has been an increasing demand for safety evaluation and control of dental materials. Since it is the members of the dental staff who handle the materials in their most reactive states they constitute the main risk category. Bearing this in mind reported side-effects in both patients and dental personnel in Scandinavia are presented. Data from the only two existing national registers for side-effects of dental materials, i.e. those in Norway and Sweden, are thus elucidated. Furthermore, recent mainly Scandinavian publications dealing with the side-effects of dental materials are presented. It can be concluded that a national register on the side-effects of dental materials, apart from revealing information regarding their frequency and nature, may detect changes in the profiles of adverse reactions and also serve as a tool for the post-marketing surveillance of dental materials.View full abstractDownload PDF (1673K) -
Rowshan AKHTER, Seigo OKAWA, Syuji NAKANO, Masayoshi KOBAYASHI, Osamu ...2000 Volume 19 Issue 1 Pages 10-21
Published: 2000
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSCast plates were prepared from commercial titanium. The plates were polished with a slurry of fine ferric oxide powder. The surface composition and structure were investigated by electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). In the high pressure-polished surface, iron was non-uniformly distributed but oxygen was mostly uniformly distributed, while in a light pressure-polished surface, iron and oxygen were uniformly distributed though at lower and higher concentrations, respectively. EPMA state analysis and XPS suggested that the iron might exist as Fe2+ in the outermost surface, while it might be in a metallic state in the inner surface layer.View full abstractDownload PDF (2826K) -
Kyo-Han KIM, Young-Bin KIM, Osamu OKUNO2000 Volume 19 Issue 1 Pages 22-33
Published: 2000
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe effect of prepolymerized particle fillers on fracture toughness of four commercial composite resins was studied. The ground surface morphology was examined with a field emission scanning electron microscope. Fracture toughness was determined by using single edge notched specimens. Acoustic Emission (AE), which is the elastic wave due to the release of energy from the localized sources of material, was detected by sensors of a high-sensitivity and lownoise resonance type during the fracture toughness test. Acoustic Emission signals detected were analyzed for parameters such as amplitude and energy. Fracture surfaces were examined with a scanning electron microscope. The fracture toughness values, AE releasing patterns during fracture toughness test, and the fracture surface findings were analyzed to understand the fracture behavior of composite resins containing prepolymerized particle fillers. A microfracture model and fracture mechanisms to increase the fracture toughness of this type of composite resins are proposed.View full abstractDownload PDF (3237K) -
Kazuhiko ENDO, Masahiro SUZUKI, Hiroki OHNO2000 Volume 19 Issue 1 Pages 34-49
Published: 2000
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe corrosion behaviors of four ferric stainless steels and two austenitic stainless steels were examined in a simulated physiological environment (0.9% NaCl solution) to obtain basic data for evaluating the appropriate composition of stainless steels for dental magnetic attachments. The corrosion resistance was evaluated by electrochemical techniques and the analysis of released metal ions by atomic absorption spectrophotometry. The surface of the stainless steels was analyzed by X-ray photoelectron spectroscopy (XPS). The breakdown potential of ferric stainless steels increased and the total amount of released metal ions decreased linearly with increases in the sum of the Cr and Mo contents. The corrosion rate of the ferric stainless steels increased 2 to 6 times when they were galvanically coupled with noble metal alloys but decreased when coupled with commercially pure Ti. For austenitic stainless steels, the breakdown potential of high N-bearing stainless steel was approximately 500mV higher than that of SUS316L, which is currently used as a component in dental magnetic attachments. The enriched nitrogen at the alloy/passive film interface may be effective in improving the localized corrosion resistance.View full abstractDownload PDF (2120K) -
Shinichi UKON, Hiroko MOROI, Kimie OKIMOTO, Makoto FUJITA, Masatsugu I ...2000 Volume 19 Issue 1 Pages 50-64
Published: 2000
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSThis study was carried out to investigate the influences of elastic moduli of the dowel-core combination on the stress distribution in the root by the use of 2-dimensional finite element analysis. The peak stress at the dowel-cement interface was influenced strongly by a change of elastic modulus of the post (from 20, 000kg/mm2 as a hard prefabricated post to 8, 000kg/mm2 as a custom cast post) for both vertical and 45 degree oblique loading (ρ>90%). Peak dentinal stress adjacent to the luting cement layer depended only on the post material for vertical loading (ρ≈99%). In contrast, the post and core materials (from 8, 000kg/mm2 as cast core to 300kg/mm2 as composite resin core) acted in cooperation on the stress magnitude for oblique loading, but the influence of the core material was stronger than that of the post (ρ of core≈41% and ρ of post≈26%).
On the other hand, at the marginal region the effect of the core material contributed more than 86% to the peak stress value for both loadings, and the post material affected at most about 11% of the bending resistance.View full abstractDownload PDF (2120K) -
Influence on Tensile Bond Strength and Antibacterial EffectYoshiyuki KUDOU, Kenichi OBARA, Toshihiro KAWASHIMA, Minoru KUBOTA, Sa ...2000 Volume 19 Issue 1 Pages 65-74
Published: 2000
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSTo produce a bonding system which has both high bond strength and antibacterial properties, an antibacterial agent (vancomycin: VCM or metronidazol: MN) was added to the PMMA powder of 4-META/MMA-TBB resin (CB). The influence of the addition of an antibacterial agent on tensile bond strength to dentin and the antibacterial effect were investigated in this study. Forty-seven freshly extracted bovine first or second incisors were used to measure the tensile bond strength to dentin. The bond strengths to bovine dentin were not significantly decreased by addition of VCM (1%, 2%, 5%), or MN (1%) to CB (p<0.05).
The antibacterial effect of CB containing antibacterial agent on six strains of bacteria was investigated by the agar plate diffusion method, analyzing the appearance of the inhibition zone around a resin disk following anaerobic culturing. The resin disks containing VCM showed antibacterial effects on all of the strains examined; the widths of the inhibition zones were 4-15mm. The resin disks containing MN showed antibacterial effects on three strains; the widths of the inhibition zones were 0-4mm.
It was thus possible to produce a bonding system with both antibacterial effect and high tensile bond strength by addition of VCM to PMMA powder.View full abstractDownload PDF (1105K) -
Atsufumi MANABE, Shoko KANEKO, Satoshi NUMAZAWA, Kazuo ITOH, Mitsuko I ...2000 Volume 19 Issue 1 Pages 75-86
Published: 2000
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe xenoestrogenic substance bisphenol-A is widely used as a synthetic precursor of resin monomers, such as bisphenol-A diglycidyl methacrylate. Reports describing the release of bisphenol-A from polymerized resin into saliva have aroused considerable concern regarding exposure to xenoestrogen by dental treatment. The purpose of the present study was to demonstrate a reliable methodology of detecting the trace amounts of bisphenol-A in dental materials. Bisphenol-A was separable from bisphenol-A diglycidyl methacrylate, which is often employed as the principal dimethacrylate monomer, by selective extraction with a Sep-Pak C18 cartridge. Using this extraction method in combination with a gas-chromatography mass-spectrometry, we have obtained evidence that all unpolymerized materials used in this study were contaminated with bisphenol-A. Quantitative analysis using a deuterium-labeled compound as an internal standard revealed bisphenol-A contents in commercial dental materials ranging from<1μg/g material to about 20μg/g material. The polymerized dental materials released up to 91.4ng bisphenol-A /g material into phosphate buffered saline during 24-h incubation. These results indicate that bisphenol-A can be released from dental materials, however the leachable amount would be less than 1/1000 of the reported dose (2μg/kg body weight/day) required for xenoestrogenisity in vivo.View full abstractDownload PDF (1265K) -
Tohru HAYAKAWA, Hiroyuki MISHIMA, Ichirou YOKOTA, Toshiro SAKAE, Yukis ...2000 Volume 19 Issue 1 Pages 87-95
Published: 2000
Released on J-STAGE: February 12, 2009
JOURNAL FREE ACCESSThe calcification degree of extracted human teeth was observed by using high resolution microfocus X-ray CT. As samples, upper and lower first premolars extracted from a 21-year-old female were used. The computed tomograms were produced by high resolution microfocus X-ray CT with a open vacuum X-ray source, rotating sample stage, and image sensor.
The distinction between enamel and dentin was very clear, and the shape of the pulp cavity was also clearly identified. The secondary dentin was visible in the circumpulpal dentin. The color map displays showed the heterogeneity of the calcification degree not only in the dentin but also in the enamel. The enamel was divided into three layers according to the calcification degree.
High resolution microfocus X-ray CT was very useful for the observation of the internal structure of human teeth without destroying the samples.View full abstractDownload PDF (2913K)
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