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Yoshinori YOSHIDA, Satoshi YAMAGUCHI, Yusuke KAWAMOTO, Hiroshi NOBORIO ...
2011 Volume 30 Issue 1 Pages
1-6
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
JOURNAL
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A virtual reality (VR) haptic dental training system could be a promising tool for future dental education. One major challenge is to develop a virtual tooth model which similarly reflected a real tooth having multiple layers with different mechanical hardness in each layer. The multi-layered virtual tooth model was successfully constructed in our virtual system. The constructed model allows us to feel tooth cutting which is similar to that with a real tooth. Through a cutting experiment by using the real tooth, a spring coefficient and a damping coefficient of a dental hard tissue were determined 0.8 N/mm and 1.79 Nsec/mm respectively. The feedback force smoothly altered when crossing the border of regions having different mechanical hardnesses. The constructed model introduced in this study could be a promising tool for acquiring dental hand skills in a virtual learning system.
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Jan DE MUNCK, Atsushi MINE, Marcio VIVAN CARDOSO, Aline DE ALMEIDA NEV ...
2011 Volume 30 Issue 1 Pages
7-13
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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Dentin is a variable substrate with properties that change considerable in a single surface. The purpose of this study was to evaluate the bonding effectiveness to these different dentin locations and evaluate these differences over time. After bonding procedures with five different adhesives, small micro-tensile bond strength (μTBS) beams were prepared and dichotomously divided in ‘center’ and ‘periphery’ dentin specimens. After 1 week, 3, 6 and 12 months of water storage the μTBS of specimens of each group was determined, enabling a paired study design. The bond strengths of both etch&rinse adhesives were insensitive to regional variability. For the two-step self-etch adhesives, a marked increase in bond strengths was observed with increasing amount of intertubular dentin. Regional variability did not affect the long-term bonding effectiveness for any of the adhesives tested. In conclusion, only for the mild self-etch adhesives, μTBS to ‘periphery’ dentin was higher than for the ‘center’ specimens.
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Michito MARUTA, Shigeki MATSUYA, Seiji NAKAMURA, Kunio ISHIKAWA
2011 Volume 30 Issue 1 Pages
14-20
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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Carbonate apatite (CO
3Ap) foam may be an ideal bone substitute as it is sidelined to cancellous bone with respect to its chemical composition and structure. However, CO
3Ap foam fabricated using α-tricalcium phosphate foam showed limited mechanical strength. In the present study, feasibility of the fabrication of calcite which could be a precursor of CO
3Ap was studied. Calcite foam was successfully fabricated by the so-called “ceramic foam” method using calcium hydroxide coated polyurethane foam under CO
2+O
2 atmosphere. Then the calcite foam was immersed in Na
2HPO
4 aqueous solution for phase transformation based on dissolution-precipitation reaction. When CaO-free calcite foam was immersed in Na
2HPO
4 solution, low-crystalline CO
3Ap foam with 93–96% porosity and fully interconnected porous structure was fabricated. The compressive strength of the foam was 25.6±6 kPa. In light of these results, we concluded that the properties of the precursor foam were key factors for the fabrication of CO
3Ap foams.
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Ching-Lien HUNG, Jen-Chang YANG, Wei-Jen CHANG, Chih-Yuan HU, Yong-Ho ...
2011 Volume 30 Issue 1 Pages
21-28
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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The ability to promote new bone formation of poor crystalline hydroxyapatite (PC-HA) based biphasic calcium phosphate (BCP) bone substitutes were investigated. Various ratios of porous PC-HA/
β-TCP (70/30, 60/40, and 0/100) grafts were fabricated. SEM and XRD measurements were performed to study the morphology and crystalline structure. Cylindrical artificial bone defects (3×6 mm
2) were produced in alveolar bone at premolars extraction site and then filled with sterilized bone grafts. Commercial MBCP
® and unfilled empty defect served as control groups. At 8 weeks postoperation, samples were harvested from each artificial defect site for histological analysis. New bone formation of all the PC-HA/
β-TCP groups was significantly greater than that of the empty control group (
p<0.05), but without statistical difference from that of MBCP
® group. The degree of uniformity of new bone formation within defect region for PC-HA/
β-TCP (60/40) was higher than that for MBCP
®. The PC-HA/
β-TCP grafts showed enhanced bone regenerations with a more even dispersion of new bone formation than the other materials without causing inflammation, suggesting that these materials may be an alternative choice for bone void fillers in dental applications.
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Nobuhisa AIDA, Akikazu SHINYA, Daiichiro YOKOYAMA, Lippo V.J. LASSILA, ...
2011 Volume 30 Issue 1 Pages
29-37
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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The aim of this study was to evaluate the influence of connectors under two different loading conditions on displacement and stress distribution generated in isotropic hybrid composite fixed partial denture (C-FPD) and partially anisotropic fiber-reinforced hybrid composite fixed partial denture (FRC-FPD). To this end, two three-dimensional finite element (FE) models of three-unit FPD from mandibular second premolar to mandibular second molar —intended to replace the mandibular first molar— were developed. The two loading conditions employed were a vertical load of 629 N (applied to eight points on the occlusal surface) and a lateral load of 250 N (applied to three points of the pontic). The results suggested that the reinforcing fibers in FRC framework significantly improved the rigidity of the connectors against any twisting and bending moments induced by loading. Consequently, maximum principal stress and displacement generated in the connectors of FRC-FPD were significantly reduced because stresses generated by vertical and lateral loading were transferred to the reinforcing fibers.
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Mi-Joo KIM, Won-Chang JUNG, Seunghan OH, Masayuki HATTORI, Masao YOSHI ...
2011 Volume 30 Issue 1 Pages
38-44
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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The aim of this study was to estimate the flexural properties of three kinds of experimental fiber-reinforced composite (FRC) posts and to evaluate their potential use as posts. Experimental FRC posts were fabricated with glass, aramid, and UHMWP fibers. Commercial FRC posts were used for comparison. A three-point bending test was performed at a crosshead speed of 1 mm/min. Experimental glass fiber posts showed significantly higher flexural strengths and moduli than aramid and UHMWP posts. Experimental UHMWP posts demonstrated superior toughness to the commercial posts. The glass fiber posts displayed stiff, strong and brittle features, while the UHMWP posts were flexible, weak and ductile. The flexural properties of the aramid posts fell between those of the glass and UHMWP posts. In conclusion, the glass fiber posts proved excellent in flexural strengths and moduli. However, the superior toughness of UHMWP fibers suggests the possibility of their use as posts in combination with glass fibers.
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Yuta KASUGA, Hidekazu TAKAHASHI, Norihisa AKIBA, Shunsuke MINAKUCHI, N ...
2011 Volume 30 Issue 1 Pages
45-51
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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The purpose of the present study was to compare the properties required for the clinical application of soft lining materials containing a fluorinated monomer
versus that of conventional materials in an effort to develop a new soft lining material with long-term stable viscoelastic properties. Four soft lining materials were examined. Two experimental materials containing dodecafluoroheptyl methacrylate (SR12F) or tridecafluorooctyl methacrylate (SR13F) were prepared. Two commercial soft lining materials, one acrylic-based and one silicone rubber-based, were selected as reference materials. Shore A hardness, viscoelastic properties, water sorption, solubility, and staining resistance were evaluated. The Shore A hardness and the displacements were analyzed with two-way analysis of variance (ANOVA) and Tukey’s HSD test. The water sorption, the solubility and the color change were analyzed with one-way ANOVA and Tukey’s HSD test. The significance level was set at 0.05. SR12F and SR13F showed greater viscous flow, low water sorption, low solubility, and good staining resistance compared to the commercial products. The results indicate that the soft lining materials containing fluorinated monomers might have a potentially long-term stable viscoelastic behavior.
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Harumasa WANIBE, Mitsunori YAMAMOTO, Kazuhiko NAKATA, Tatsushi KAWAI, ...
2011 Volume 30 Issue 1 Pages
52-57
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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The purpose of this study was to examine the physical properties of PEMA-TA/HX-based resins including 20 to 100% ethanol, for a root canal filling material. The values of the elastic modulus in the samples including ethanol were more than 250 MPa, being higher than the approximately 40 MPa of Gutte-percha (GP). The values of compressive strain in the samples increased in an ethanol concentration-dependent manner. The weight of samples including ethanol decreased gradually. In the adhesiveness test, the values of PEMA-TA/HX-based resins including ethanol were significantly higher than that of GP (
p<0.01). Cohesive fractures were observed in Super-Bond SEALER in the samples including ethanol except for 20%. The results suggest that the new PEMA-TA/HX-based resin cone in combination with resin-based sealer might facilitate “monoblock obturation”. The new PEMA-TA/HX-based resin cone developed in the present study may be effective root canal filling material for vertical root fractures.
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Miho HAYASHI, Tetsuji TAKAHASHI, Kazuko KAWAGUCHI, Takao WATANABE, Jia ...
2011 Volume 30 Issue 1 Pages
58-65
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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β-TCP was implanted into bone defects of dog mandibles, and gene expression profiles were examined using DNA microarray. An implant drill was used to make bone defects, and then
β-TCP was filled into bone defects. All specimens were taken out, total RNA was isolated, and levels were analyzed using Affymetrix GeneChip. Higher mRNA levels of connexin 43 (Cx43) and Cx45 were observed in
β-TCP-implanted samples compared with controls. The enhancement of Cx43 and Cx45 by
β-TCP was confirmed by RT-PCR and real-time RT-PCR. Since Cx43 is known to express in bone-forming regions and is involved in osteogenesis through gap junctional intercellular bone-cell communication (GJIB), immunohistochemical staining was also examined and demonstrated Cx43 protein expression was increased in
β-TCP-implanted bone. Cx43 plays a role in osteogenesis through GJIB; therefore, the stimulation of Cx43 expression by
β-TCP might be a mechanism of accelerating wound healing and bone formation.
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Melek D. TURGUT, Nuray ATTAR, Yonca KORKMAZ, Aylin Gokcelik
2011 Volume 30 Issue 1 Pages
66-71
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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This study evaluated the shear bond strengths of orthodontic brackets bonded to human premolars using five different combinations of flowable composites and one-step self-etching adhesives (
n=12): (1) Adper Easy Bond+Filtek Supreme XT Flow; (2) Futurabond NR+Grandio Flow; (3) Clearfil S3 Bond+Clearfil Majesty Flow; (4) AdheSE One+Tetric EvoFlow; and (5) Transbond Plus Self Etching Primer+Transbond XT Light Cure Adhesive. After shear bond strength testing, adhesive remnant index (ARI) scores were given according to the amount of adhesive and resin remaining on the brackets. On shear bond strength, there were no statistically significant differences between Groups 2 and 4 and between Groups 3 and 5 (
p>0.05). On ARI scores, the predominant ARI scores in Groups 1, 2, 3, and 5 were 4, 2, 5, and 4 respectively; in Group 4, they were 0 and 4. Results showed that some combinations of flowable composites and self-etching adhesives might not be suitable for orthodontic use due to their low shear bond strengths and high ARI scores —with the latter signaling the risk of damaging the enamel surface during debonding.
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Kunio IKEMURA, Katsunori KOJIMA, Takeshi ENDO, Yoshinori KADOMA
2011 Volume 30 Issue 1 Pages
72-78
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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This study investigated the effect of novel dithiooctanoate monomers, in comparison with conventional sulfur-containing monomers, on adhesion to precious metals and alloys. Nine experimental primers containing 5.0 wt% 2-methacryloyloxyethyl 6,8-dithiooctanoate (2-MEDT), 6-methacryloyloxyhexyl 6,8-dithiooctanoate (6-MHDT), 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT), bis(2-methacryloyloxyethyl) disulfide (BMEDS), bis(5-methacryloyloxypentyl) disulfide (BMPDS), bis(10-methacryloyloxydecyl) disulfide (BMDDS), 6-(4-vinylbenzyl-
n-propyl) amino-1,3,5-triazine-2,4-dithione (VBATDT),
N-(4-mercaptophenyl)methacrylamide (MPMA), or 4-methacryloyloxyethoxycarbonylphthalic anhydride (4-META; control) were prepared. After primer pretreatment and bonding using modified MMA-PMMA/BPO-DEPT resin, tensile bond strengths to precious metals and alloys after 2,000 thermal cycles were measured. For bonding to Au or Ag, novel 2-MEDT, 6-MHDT, and 10-MDDT exhibited significantly higher tensile bond strengths than conventional BMEDS, BMPDS, BMDDS, VBATDT, MPMA, and 4-META (
p<0.05). For bonding to Au alloy, Ag alloy, and Au-Ag-Pd alloy, all the novel dithiooctanoate monomers showed significantly higher tensile bond strengths than conventional BMEDS, BMPDS, VBATDT, MPMA, and 4-META (
p<0.05). It was found that novel dithiooctanoate monomers exhibited excellent bonding to precious metals and alloys when compared with conventional sulfur-containing monomers.
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Masanori NAGAME, Yutaka KOMASA, Kazutoshi KAKIMOTO, Fuminobu KUBO
2011 Volume 30 Issue 1 Pages
79-86
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
JOURNAL
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Although ceramic fiber is widely used in ring liners for dental casting, its carcinogenicity is a matter of concern. We investigated the use of noncarcinogenic biosoluble fiber for ring liners. Plate-shaped biosoluble fiber was modified to obtain the same setting expansion as that of a commercial ring liner as a prototype, and we subjected it to scanning electron microscopic observation, energy-dispersive X-ray spectrometry, X-ray diffraction, and a tensile test. The main components of the prototype were Mg, Si, and O and those of the commercial sample were Al, Si, and O. The prototype and commercial samples were mostly amorphous when not heated, and crystalline components were observed after heating. The tensile strength was significantly different between the prototype and commercial samples, but the difference was small and not problematic with regard to the ring liner strength.
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Mizuho KUSUNOKI, Kazuo ITOH, Yuka GOKAN, Yoshitaka NAGAI, Chihiro TANI ...
2011 Volume 30 Issue 1 Pages
87-92
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
JOURNAL
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The purpose of this study was to evaluate changes in the quantity of water evaporation from tooth surfaces. The amount of water evaporation was measured using Multi probe adapter MPA5 and Tewameter TM300 (Courage+Khazaka Electric GmbH, Köln, Germany) after acid etching and GM priming of enamel; and after EDTA conditioning and GM priming of dentin. The results indicated that the amount of water evaporation from the enamel surface was significantly less than that from the dentin. Acid etching did not affect the water evaporation from enamel, though GM priming significantly decreased the evaporation (83.48±15.14% of that before priming). The evaporation from dentin was significantly increased by EDTA conditioning (131.38±42.08% of that before conditioning) and significantly reduced by GM priming (80.26±7.43% of that before priming). It was concluded that dentin priming reduced water evaporation from the dentin surface.
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Manabu KANAZAWA, Masanao INOKOSHI, Shunsuke MINAKUCHI, Naoto OHBAYASHI
2011 Volume 30 Issue 1 Pages
93-96
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
JOURNAL
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The purpose of this study was to evaluate the fabrication of a complete denture using a CAD/CAM system. Cone beam CT was used to measure the complete denture and the artificial teeth. After a 3D complete denture image was structured using 3D CAD software, we factored out the artificial teeth and obtained a 3D denture base image. A machining center cut an acrylic resin block, and fabricated an acrylic complete denture base. The artificial teeth were bonded to the cut denture base using resin cement. A 3D digitizer digitized the fabricated acrylic denture. We measured the deviations between the master 3D complete denture image and the 3D data of the fabricated acrylic denture. The average deviations from the master 3D image were 0.50 mm for the occlusal surface. This present study indicates that it is possible to fabricate a complete denture using a CAD/CAM system.
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Özge KARATASLI, Pinar KURSOGLU, Nuray ÇAPA, Ender KAZAZOGL ...
2011 Volume 30 Issue 1 Pages
97-102
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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In this study, marginal adaptations of different copings fabricated with CAD/CAM or MAD/CAM were analysed. Celay and Zirkonzahn groups were fabricated by MAD/CAM, LAVA and DC-Zircon groups were fabricated by CAD/CAM. Casting metal copings were used as the control group. An implant abutment that was embedded in octagonal acrylic block was used to prepare the copings. Sixteen previously established points were marked and the measurements were performed with the stereomicroscope (at ×150). The marginal fit of the samples were evaluated by calculating the mean measurements of each 16 points. The statistical analysis was performed by Tukey multiple comparisons test at 95% confidence interval. The groups can be summarized as follows in terms of marginal gap, from the lowest to highest: LAVA (24.6±14.0 μm)<Celay (64.9±25.2 μm)<DC-Zircon (110.1±36.5 μm)<Zirkonzahn (112.11±22.6 μm)<Metal (120.1±33.1 μm). Usage of CAD/CAM or MAD/CAM systems may not be the most important factor for marginal adaptation.
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Shigeaki KURATA, Noboru YAMAZAKI
2011 Volume 30 Issue 1 Pages
103-108
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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To recognize good mechanical properties and water-resistance of a dental resin, dimethacryloxyethyl-1,1,6,6-tetrahydro-perfluoro-hexamethylene-1,6-dicarbamate (FDMHD) was newly synthesized. FDMHD initially was a white powder with m.p. 98.5−99.5°C. The copolymers of FDMHD and methyl methacrylate (MMA), FDMHD/MMA copolymers, were prepared to estimate the basic properties for dental resin materials. The compressive strength of FDMHD/MMA copolymers was almost the same compared with those of the copolymers of Bis-GMA or dimethacryloxyethyl-hexamethylene-1,6-carbamate (DMHD) and MMA. The bending, tensile, diametral tensile, impact strength and toughness of FDMHD/MMA copolymers containing 10.4 mol% FDMHD were higher than those of Bis-GMA/MMA copolymer, and the water sorption of FDMHD/MMA copolymers was lower than those of DMHD/MMA copolymers.
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Frank P. NOTHDURFT, Thomas SCHMITT, Stefan RUPF, Peter R. POSPIECH
2011 Volume 30 Issue 1 Pages
109-114
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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The aim of the study was to evaluate the influence of fatigue and cementation mode on the fracture behaviour of endodontically treated bovine incisors restored with fiber-reinforced-composite (FRC) posts and crowns. Forty-eight endodontically treated incisors were restored with FRC posts, composite build-ups, and cast crowns. In 16 teeth, each of the posts were cemented conventionally with KetacCem (3M Espe) or adhesively with Panavia F (Kuraray) or RelyXUniCem (3M Espe). One-half of the specimens in each group were subjected to thermal cycling with 10,000 cycles at 5–55°C and mechanical aging, loading the specimens in 1,200,000 cycles with 50 N. Fracture resistance was determined by loading the specimens until fracture at an angle of 45°. The loading test showed that cementation mode and fatigue testing had an influence on the load bearing capability. Before fatigue testing no statistically significant differences between the different cementation modes could be detected. After fatigue testing, conventionally cemented FRC posts lead to statistically significant higher fracture loads compared to adhesively luted posts. Most specimens fractured in a favourable way, independent from the type of cementation.
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Shigeaki KURATA, Kozo UMEMOTO
2011 Volume 30 Issue 1 Pages
115-120
Published: 2011
Released on J-STAGE: February 04, 2011
Advance online publication: January 26, 2011
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To reduce the adverse effects of water on the mechanical properties and bonding durability of glass ionomer cements, experimental cements which used a temperature-responsive polymer as the cement liquid were prepared and evaluated in this study. Temperature-responsive copolymers were synthesized using radical polymerization with varying molar ratios of N-isopropylacrylamide (NIPAM) and acrylic acid (AA). It was found that copolymer synthesis with varying ratios of NIPAM and AA was able to modify the lower critical solution temperature to range between 27 and 42°C. Bond strength of the cement prepared from AA/NIPAM copolymer containing 53 mol% AA was better than that prepared from polyacrylic acid (PAA) —the conventional cement liquid. However, compressive strength of the experimental cement was slightly lower than that of PAA cement.
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