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Naho HAMANO, Satoshi INO, Satoru HOJO, Fumihiko YOSHINO, Tomonaga WATA ...
2007 年 26 巻 6 号 p.
761-765
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The purpose of this study was to investigate the effect of irradiation on the polymerization behavior of a bonding agent of a dual-cured self-etching bonding system. By means of electron spin resonance spectroscopy, it was shown that the concentration of polymer radicals in samples cured chemically without irradiation was closely similar to that in samples dual-cured under irradiation. There was no significant difference in the time required to reach the maximum spin concentration between these two sample groups, thereby showing that the radical generation rates were similar. Findings of this study revealed that the dual-cured self-etching bonding system tested in this study was effective in polymerization in regions where irradiated light could hardly reach.
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Jens FISCHER, Bogna STAWARCZYK, Milos TOMIC, Jörg R. STRUB, Chris ...
2007 年 26 巻 6 号 p.
766-772
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
Thermal misfit is deemed as one reason for the chipping of veneered zirconia restorations. Aim of the present study was to assess the effect of thermal misfit on the fracture load of veneered zirconia frameworks and to evaluate the applicability of a universal veneering ceramic for both zirconia and titanium frameworks. Fracture loads of zirconia and titanium frameworks veneered with different ceramics were measured. Differences in the thermal expansion coefficients of core and veneer (Δ
α), as well as differences between glass transition temperatures of the veneering ceramics and room temperature (ΔT)—which is considered as the effective temperature range for stress formation, were determined. In the zirconia group, fracture load ranged from 818.0±127.2 to 935.2±186.3 N without significant differences (Student's t-test, p<0.05). Moreover, zirconia and titanium crowns veneered with the universal veneering ceramic revealed high fracture load. Results also showed a correlation to the product Δ
α · ΔT, such that if 185 · 10
-6<Δ
α · ΔT<1120 · 10
-6, a veneering ceramic adapted for titanium might be likewise applicable for zirconia.
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Andrea V. KANESHIRO, Satoshi IMAZATO, Shigeyuki EBISU
2007 年 26 巻 6 号 p.
773-784
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The aim of this study was to compare the bonding ability of single-step self-etching adhesives with different degrees of etching aggressiveness to root dentin. Composite restorations were placed on sound or caries-affected root dentin using a “strong” (Adper Prompt L-Pop, Absolute) or “mild” (Clearfil Tri-S Bond, Reactmer Bond) system. Immediately after restoration placement and after 24-hour storage in distilled water, the bonding interface was examined by scanning electron microscopy. Microtensile bond strength (MTBS) on sound root dentin was also measured with each storage condition.
The adhesives with strong etching aggressiveness demonstrated interfacial integrity immediately after restoration and also after 24 hours of storage. Conversely, the “mild” adhesives showed debonding immediately after restoration. There were no statistical differences in MTBS among the four systems, nor between the two storage periods for each material. For restorations on root dentin using single-step adhesives, “strong” systems were thus recommended as they favorably produced a stable bond since the early stage.
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Yoshiya HASHIMOTO, Jiro TANAKA, Kazuomi SUZUKI, Masaaki NAKAMURA
2007 年 26 巻 6 号 p.
785-791
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
In the current study, we examined the cytocompatibility of eight vinyl esters as candidate plasticizers for producing phthalate- and ethanol-free tissue conditioners. We measured the estrogenic activity and cytotoxicity of vinyl esters in human fibroblasts and keratinocytes using an E-screen assay and a mitochondrial dye conversion assay, respectively. We also assessed the cytotoxicity of three prototype materials and commercially available tissue conditioners on human fibroblasts grown in collagen gels. Finally, we measured the effects of these materials on the expression of cytokines in three-dimensional cultures by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assays. None of the tested vinyl esters had estrogenic activity. Vinyl octanoate and vinyl pivalate were the least cytotoxic of the eight tested vinyl esters. In the same vein, a prototype tissue conditioner containing vinyl octanoate had equivalent or weaker cytotoxicity and induction of cytokine expression than conventional materials.
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Kou FUJITA, Shen MA, Rui LI, Jun LI, Takuji IKEMI, Norihiro NISHIYAMA
2007 年 26 巻 6 号 p.
792-799
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
This study sought to investigate the degradation mechanism of 4-methacryloyloxy ethyl trimellitic acid, 4-MET, which is commonly used as an acidic monomer in solvated self-etching primers or one-step bonding agents. To this end, we examined the effects of solvent type used—such as ethanol, methanol, and acetone—on the degradation mechanism of 4-MET by using the
13C NMR technique.
The degradation mechanism of 4-MET was strongly dependent on the type of solvent used. When an alcohol-based solution was used for 4-MET, the esterification of 1- or 2-carboxylic acid in 4-MET occurred. However, when an acetone solvent was used for 4-MET, the esterification reaction did not occur. Increases in the aging period of 4-MET solvated solutions resulted in the hydrolysis of the benzoyl ester portion in 4-MET. The 2-hydroxyethyl methacrylate, produced as a subproduct, also became hydrolyzed. In addition, methacrylic acid, non-esterified and esterified trimellitic acid, as well as ethylene glycol were produced as subproducts. In particular, the production of trimellitic acid and ethylene glycol affected the bonding efficacy and durability of the resin to the tooth created by self-etching primers or one-step bonding agents that contained the altered 4-MET.
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Shigeaki KURATA, Kozo UMEMOTO
2007 年 26 巻 6 号 p.
800-804
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
With a view to improving the bond strength of resin to dental ceramics and alloys, new silane coupling agents, namely 4-trichlorosilylpropyl- and 4-trimethoxysilylpropyl-trimellitic anhydride (4-CSTA and 4-MSTA, respectively), were synthesized. In addition, silane mixtures of 4-CSTA with 3-methacryloyloxypropyltrimethoxysilane (3-MPS) and 4-MSTA with 3-MPS were used as primers for adhesion of poly (methyl methacrylate) to glass, silver-palladium-gold alloy (Ag-Pd alloy), and cobalt-chromium alloy (Co-Cr alloy). The tensile bond strengths of resin to glass using 4-CSTA+3-MPS and 4-MSTA+3-MPS were 28.5±5.3 and 23.9±8.1 MPa respectively. With the metal alloys, the strengths were 14.8±5.3 MPa for Ag-Pd alloy and 24.7±7.2 MPa for Co-Cr alloy. In the light of these results obtained, it seemed that the mixture of 4-MSTA and 3-MPS was an effective primer for both metals and ceramics.
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Paola G. LOYAGA-RENDON, Hidekazu TAKAHASHI, Naohiko IWASAKI, Fazal REZ ...
2007 年 26 巻 6 号 p.
805-813
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The purpose of the present study was to evaluate how ultraviolet light (UV) irradiation using an ordinary UV sterilizer would affect the bonding of experimental composite resins to an autopolymerizing acrylic resin. To this end, three composite resins and one unfilled resin—of which the compositions were similar to commercial composite resin artificial teeth—were prepared as repair composites. Their shear bond strengths after UV irradiation for one to 60 minutes were significantly greater than those before UV irradiation regardless of composite resin type. Failure mode after UV irradiation for one to 60 minutes was mainly cohesive failure of the composite resins, but that before UV irradiation and after 24 hours' irradiation was mainly adhesive failure. These results thus suggested that a short period of UV irradiation on composite resin teeth would improve the bonding efficacy of composite resin artificial teeth to autopolymerizing resin.
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Yoshihiko FUSE, Isao HIRATA, Hidemi KURIHARA, Masayuki OKAZAKI
2007 年 26 巻 6 号 p.
814-819
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
Mixed self-assembled monolayers (SAMs) with hydroxyl and methyl surface groups were prepared as biomaterial surface models which were well-controlled and well-defined. The surface properties of mixed SAMs were examined by X-ray photo-electron spectroscopy and water contact angle measurement. It was found that the parameter of water contact angle more accurately reflected the surface compositions of mixed SAMs than by the mixing ratio of the two alkanethiols. Cell adhesion and growth were also examined on mixed SAMs of various wettability conditions. It was found that amount of serum protein adsorption changed with the surface composition. To examine the effect of surface composition on cell growth pattern, four cell types—C3H10T1/2-clone 8, L929, UVB6-2.1A, and MC3T3E1—were incubated on mixed SAMs for three or six days. Differences in cell growth pattern against wettability were clearly recognized for each cell type. In light of the results obtained in this study, the relationship between the biocompatibility of biomaterials and surface factors were thus clarified.
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Jun KUNII, Yasuhiro HOTTA, Yukimichi TAMAKI, Atushi OZAWA, Yukitaka KO ...
2007 年 26 巻 6 号 p.
820-826
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The aim of this study was to investigate the effect of post-machining sintering on marginal and internal fit of CAD/CAM-fabricated zirconia frameworks. Single crown copings (A: abutment), three-unit bridge frameworks (APA, P: pontic), four-unit bridge frameworks (APPA), and five-unit bridge frameworks (A
1P
1A
2P
2A
3) were fabricated with raw-stage zirconia blanks using a commercial CAD/CAM system (KATANA®, Noritake Dental Supply Co. Ltd., Aichi, Japan). Crown copings and frameworks were cemented to their respective master abutment models, and thickness of the cement layer was measured at specific measuring points. Marginal and internal fit of both APA and APPA were within clinical acceptance. However, the marginal gap and thickness of the cement layer on the axial surface of the pontic side of APA and APPA were slightly higher than those of the non-pontic side. As for the marginal gap of A
1P
1A
2P
2A
3 framework, it was superior to those of APA and APPA because the center abutment supported the framework to prevent distortion.
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Jamshid AGHAZADEH MOHANDESI, Mohammad Ali RAFIEE, Vahid BARZEGARAN, Fa ...
2007 年 26 巻 6 号 p.
827-837
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The purpose of this study was to investigate the compressive fatigue behavior of five dental composites. Cylindrical specimens of 8 mm length and 4 mm diameter were made according to manufacturers' recommendations and stored for two weeks in distilled water at 37°C. Compressive fracture strength was measured, and subsequently fatigue tests at 10 Hz frequency were carried out in distilled water. Compressive fatigue strength was thereby obtained using the staircase method for 10
5 cycles (n=17) under sinusoidal loading. Acquired data for compressive fracture strength were analyzed using ANOVA and Weibull statistics. Among the dental composites examined, Filtek
® Z250 exhibited the highest fatigue strength. This seemed to be due to the superior matrix properties coupled with a specific filler type at the highest weight%/volume% ratio. In addition, fracture mechanisms of the composites were examined.
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Tae-Sung JEONG, Young-Ran KIM, Jong-Hwa KIM, Hyung-Il KIM, Yong Hoon K ...
2007 年 26 巻 6 号 p.
838-844
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The purpose of this study was to examine the effects of LEDs on the polymerization of dental composite resins. Three composite resins and two LED units were used to evaluate the latter's effects on microhardness and temperature rise. In particular, two composite resins contained a coinitiator in addition to camphorquinone (CQ). The emission peak of the tested LEDs matched well with the absorption peak of CQ, while G-Light had one additional but weak peak near 410 nm. As for the coinitiators, their absorption peaks were lower than 400 nm. Within the specimens, incident photons from the LED units showed an exponential decrease in their counts as the specimens became thicker. However, microhardness values decreased and became almost linear at subsurface levels regardless of the curing unit. Among the composite resins, Z250 showed the highest microhardness value. As for the temperature rise (°C) due to exothermic reaction at polymerization, it was higher than 5°C for the 40-second light curing with both LED units. Among the specimens, Solitaire 2 cured with G-Light showed the highest temperature rise.
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Ihsan HUBBEZOGLU, Giray BOLAYIR, Orhan Murat DOGAN, Arife DOGAN, Ali & ...
2007 年 26 巻 6 号 p.
845-853
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
This study examined the surface microhardness of four kinds of resin composites with different fillers and resin matrices. Ten specimens of 2 mm thickness and 4 mm diameter of each resin composite were polymerized using a halogen light, a blue light-emitted diode, and a plasma arc unit. Microhardness evaluation was performed at top and bottom surfaces for each specimen using a Vickers microhardness tester. Furthermore, morphologies of the polished top surfaces of composites cured with blue light-emitted diode were observed using scanning electron microscopy. Results indicated that composites cured with halogen or blue light-emitted diode light yielded higher microhardness values, although it also appeared to depend on the type of composite cured. Plasma arc curing according to manufacturer's instructions yielded the lowest microhardness values for all the materials. Among the materials tested, the nanofilled resin composite displayed the highest microhardness values for each curing regime.
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Tadao FUKUSHIMA, Minoru KAWAGUCHI, Tohru HAYAKAWA, Shoji TAKEDA, Yusuk ...
2007 年 26 巻 6 号 p.
854-860
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
We evaluated the blended compound of DNA/lipid complexes and PLGA (poly(D,L-lactide-co-glycolide)) as a carrier material for drug delivery system (DDS). Transparent, self-standing DNA/lipid/PLGA films were prepared by casting from an organic solvent such as DMSO/chloroform. Daunorubicin hydrochloride (DH) could intercalate and groove bind into DNA in the films, whereby the amount of DH bound to the films was controlled by the latter's immersion period in DH aqueous solution. DH was released from DH films after immersion in PBS solution, whereby release rate was dependent on the chemical structure of lipids. Released DH caused reduction of cell viability during the cell culture of L929 mouse fibroblasts. These results suggested that DNA/lipid/PLGA film was a promising useful material for DDS.
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Kouhei MASUKI, Yuji NOMURA, Ujjal Kumar BHAWAL, Masahiko SAWAJIRI, Isa ...
2007 年 26 巻 6 号 p.
861-869
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The aim of this study was to examine the apoptotic and necrotic influence of four dental resin polymerization initiators—namely benzoyl peroxide (BPO), camphorquinone (CQ), dimethylaminoethyl methacrylate (DMAEMA), and dimethyl-para-toluidine (DMPT)—on human gingival fibroblast (HGF) cells. To this end, the growth inhibition of HGF cells with 1 mM BPO, CQ, and DMAEMA, and 500 μM DMPT was evaluated using Cell Counting Kit-8. Then, cell cycle analysis by flow cytometry was used to assess propidium iodide-stained cells (distribution of cells in G
0/G
1, S, G
2/M phases). All four dental resin polymerization initiators induced G
0/G
1 cell cycle arrest. As for the patterns of cell death (necrosis and/or apoptosis), they were analyzed using Annexin V-FITC/PI staining with flow cytometry. All four dental resin polymerization initiators most likely induced necrosis.
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Akira NAKAI, Hideo OGURA
2007 年 26 巻 6 号 p.
870-874
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The objective of this study was to develop a casting investment that prevents the blackening of the cast surface of noble metal alloys. Experimental investments were prepared using a gypsum-bonded investment in which a hydroxide, namely Mg(OH)
2 or Ca(OH)
2, was added. An Ag-Pd-Cu-Au alloy was cast into the mold made of the prepared investment. The addition of both hydroxides showed a significant effect on the color of as-cast surfaces, which was improved with increase in additive content. When Mg(OH)
2 or Ca(OH)
2 was added at more than 4.0 mass% to the investment, it was useful in preventing the blackening of the as-cast surfaces of an Ag-Pd-Cu-Au alloy. As for differences in the effects between Mg(OH)
2 and Ca(OH)
2, they were not found.
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Koichi MURAGUCHI, Satsuki SHIGENOBU, Shiro SUZUKI, Takuo TANAKA
2007 年 26 巻 6 号 p.
875-881
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The purposes of this study were twofold: (1) to examine the effects of bleaching on the bond strength of an adhesive to bovine tooth surfaces; and (2) to explore the effectiveness of an ascorbic acid application in preventing the deterioration of bonding ability due to bleaching. In the experimental groups, ascorbic acid was applied to the bleached bovine tooth surfaces. In the control groups, the tooth specimens were bleached but no ascorbic acid application was carried out. All bonded specimens were subjected to shear bond test, and the data were statistically analyzed with twoway ANOVA and Bonferroni's test (p=0.05). Bond strengths to the bleached specimens were significantly lower than those of non-bleached specimens. No statistical differences were found in bond strength between the bleached and non-bleached groups when the ascorbic acid treatment was carried out. Results of this study suggested that ascorbic acid application was effective in preventing the reduction of bonding ability to bleached teeth.
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Akira NAKAJIMA, Mamoru MURATA, Eiji TANAKA, Yoshinori ARAI, Yasumasa F ...
2007 年 26 巻 6 号 p.
882-891
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
Previously, numerous three-dimensional finite element (FE) models of the dentoalveolar complex have been developed and stress analyses of orthodontic tooth movements were reported. Most of the models were, however, developed based on average anatomical data, but not on individual data. The aim of this study, therefore, was to investigate dentoalveolar stress distribution by lingual and distal tipping tooth movements using FE models of individual teeth based on the limited cone beam CT (3DX) images. Three extracted teeth (lower canine, upper molar, and lower molar) were used to test the three-dimensional reconstruction procedure in terms of accuracy and reproducibility in linear dimensions and sizes. From the stress analysis of the three different models, the equivalent stress in tipping movement concentrated at the cervical region of the PDL and bone crest in all teeth. It was suggested that the FE modeling technique based on 3DX in this study is recommended for the individual determination of optimal orthodontic force for effective tooth movement.
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Satoru UYAMA, Atsushi IROKAWA, Mika IWASA, Motoka TONEGAWA, Yoko SHIBU ...
2007 年 26 巻 6 号 p.
892-897
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The purpose of this study was to evaluate the influence of irradiation time on volumetric change and flexural properties of flowable resins. Four commercially available flowable resins were employed. For volumetric shrinkage measurement, resin pastes were inserted into a mold (2 mm in height, 4 mm in diameter) and put into a water-filled dilatometer. This was followed by light irradiation for 10, 20, or 30 seconds at 600 mW/cm
2. Volumetric shrinkage of the specimens was then determined from the change in the height of water meniscus, and the percentage volumetric change thereof was calculated. For flexural strength measurement, resin pastes were filled into a stainless steel mold (25×2×2 mm), and the middle one-third of the specimen was first irradiated. The remaining two-thirds were irradiated under the same irradiation conditions as volumetric shrinkage measurement. After 24-hour storage in 37°C water, three-point flexural tests were performed with a span length of 20 mm at a crosshead speed of 1.0 mm/min. One-way ANOVA followed by Tukey's HSD test were used for statistical analysis. For all materials tested except Estelite Flow Quick, both volumetric shrinkage and flexural strength increased with longer light irradiation time. Results of this study indicated that both volumetric shrinkage and flexural properties were influenced by light irradiation time and resin composite type.
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Katsuya ANDO, Masahiro KUROSAWA, Yuji FUWA, Takamasa KONDO, Shigemi GO ...
2007 年 26 巻 6 号 p.
898-905
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The aim of this study was to establish an objective and quantitative method of measuring occlusal contact areas. To this end, bite records were taken with a silicone impression material and a light transmission device was used to read the silicone impression material. To examine the effectiveness of this novel method, the occlusal contact area of the silicone impression material and its thickness limit of readable range were measured. Results of this study suggested that easy and highly accurate measurements of occlusal contact area could be obtained by selecting an optimal applied voltage of the light transmission device and an appropriate color of the silicone impression material.
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Linlin HAN, Akira OKAMOTO, Masayoshi FUKUSHIMA, Takashi OKIJI
2007 年 26 巻 6 号 p.
906-914
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
This study sought to evaluate the pH value, film thickness, filler particle percentage, and morphological changes of self-adhesive resin luting cements. Products tested were G-Cem, Maxcem, Smart Cem, and RelyX™ Unicem. Cement pH was measured with pH test paper. Filler particle percentage was calculated after cement samples were incinerated at 750°C. To test film thickness, mixed cements were placed between two glass plates and compressed using a loading device. For morphological changes, specimen surfaces were observed by SEM after treatment with various media. There were significant differences among the cement pH values measured at 20 seconds after light curing, and at 90 seconds and 48 hours after mixing. Filler particle percentage was directly proportional to film thickness. Degradation of cement surfaces was also detected after surface polishing and immersion in water, acetic acid, and acetone. In conclusion, significant differences were found in the surface properties of the materials tested, and these differences might lead to differences in their clinical performance.
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Masaomi IKEDA, Khairul MATIN, Toru NIKAIDO, Richard M. FOXTON, Junji T ...
2007 年 26 巻 6 号 p.
915-923
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
The purpose of this study was to evaluate the adherence of biofilms to the surfaces of two indirect resin composites, Estenia C&B and Gradia. Slabs were prepared from the materials, and then either ground with 800-grit silicon carbide paper or polished with diamond pastes up to 1 μm. Artificial biofilms of
Streptococcus mutans were grown on the composite slabs in an artificial mouth system for 20 hours. Thereafter, the amounts of retained biofilm on the surfaces were measured after sonication. Surface characteristics of the resins—such as surface roughness, amount of residual monomers, and distribution of filler particles—were examined. Two-way ANOVA revealed that the amount of retained biofilm varied (p<0.05) according to the composition and surface roughness of the material. In particular, biofilm adherence was lowest on Estenia C&B slabs when polished with diamond pastes up to 1 μm. It was thus concluded that the surface roughness and composition of a resin composite influenced biofilm adherence.
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Yosuke HORIUCHI, Mariko HORIUCHI, Takao HANAWA, Kunimichi SOMA
2007 年 26 巻 6 号 p.
924-929
発行日: 2007年
公開日: 2009/02/06
ジャーナル
フリー
Photocatalytic activity from the reaction of titanium oxide with ultraviolet light has recently gained much attention. In particular, there is scientific interest in inducing photocatalytic reactions on Ti-Ni alloy, a material widely used in orthodontic applications. However, it is believed that inducing a photocatalytic reaction with an amorphous oxide film on the alloy is a difficult challenge. In this study, therefore, we sought to induce a photocatalytic reaction on Ti-Ni alloy by subjecting the latter to electrolytic and heat treatments. Then, an antibacterial test was used to examine whether a photocatalytic reaction had indeed been induced. By thickening the titanium oxide film with electrolytic treatment and then applying heat treatment, the surface oxide film of Ti-Ni alloy was thus modified from amorphous structure to rutile crystal. Furthermore, it was revealed that Ti-Ni alloy had an antibacterial effect by virtue of the photocatalytic reaction.
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