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Guang HONG, YingAi LI, Takeshi MAEDA, Wataru MIZUMACHI, Shinsuke SADAM ...
2008 Volume 27 Issue 2 Pages
153-158
Published: 2008
Released on J-STAGE: January 27, 2009
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The purpose of this study was to compare the influence of three kinds of storage methods on surface roughness of tissue conditioners. Four commercial tissue conditioners (GC Soft Liner, Softone, Fictioner, and Hydro-Cast) were used in this study. Five samples of each material were stored in distilled water, air, and a denture cleanser (Polident). Mean surface roughness (R
a) values of dental stone casts made from the tissue conditioners were measured after 0, 1, 3, 7, and 14 days of immersion using a profilometer. Significant differences in the R
a values of the specimens were found among the three storage methods. The values of R
a significantly increased with increase in immersion time for each storage method, except for the materials stored in air. It was found that the materials stored in air showed the most stable and lowest values of R
a. Results obtained suggested that a tissue conditioner exhibited smooth and minimal change in surface roughness with time when stored in air than in distilled water and denture cleanser.
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Makoto TSUKAKOSHI, Akikazu SHINYA, Harunori GOMI, Lippo V.J. LASSILA, ...
2008 Volume 27 Issue 2 Pages
159-171
Published: 2008
Released on J-STAGE: January 27, 2009
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To evaluate the interactive influence of adhesive materials and surface treatments on bond strength of zirconium oxide ceramics, six types of adhesive resin cements (RelyX ARC (RA), Super-Bond C & B (SB), Linkmax (LM), Panavia Fluoro Cement (PF), Bistite II (BT), and Imperva Dual (ID)), three types of resin-reinforced glass ionomer cements (Xeno Cem Plus (XC), Vitremer Luting (VR), and Fuji Luting (FL)), as well as four types of surface treatments (#600 polishing, sandblasting, silane, and Rocatec system) were used in this study.
Results of this study indicated that all the tested adhesive materials treated with Rocatec system achieved the highest shear bond strength (31.9—67.1 MPa). In particular, the highest shear bond strength value of 67.1 MPa was found for Linkmax and Rocatec treatment combination, while the lowest shear bond strength value of 5.4 MPa was found for RelyX and #600 polishing combination. Furthermore, results showed that Rocatec treatment was an effective way to prevent marginal leakage.
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Masanori HASHIMOTO, Shinichi FUJITA, Masayuki KAGA, Yasutaka YAWAKA
2008 Volume 27 Issue 2 Pages
172-178
Published: 2008
Released on J-STAGE: January 27, 2009
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This study evaluated the effect of water on dentin substrate bonding of one-bottle self-etching adhesives. Dentin substrates were divided into two groups: wet and dry dentin. Wet dentin is the normal substrate for bond testing whereas dry dentin was dehydrated in a desiccator for 24 hours. Bonded dehydrated teeth were then divided into two subgroups: stored in water or in desiccator for 24 hours. Microtensile bond strength of resin to dentin was measured using three one-bottle self-etching adhesives. In addition, nanoleakage evaluation was performed through the analyses of SEM and TEM micrographs. The bond strength of dry-dentin group was significantly greater than that of wet-dentin. Further, the amount of nanoleakage within the adhesive interface of dry-dentin group was less than that of wet-dentin. Results showed that bond strength and nanoleakage formation depended on the bonding substrate (wet
versus dry dentin) before bonding. One-bottle self-etching adhesives might suck the water from dentinal tubules during bonding by osmosis, leading to nanoleakage formation and thus a decline in bond strength.
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Yali CHENG, Takako SAKAI, Ryoji MOROI, Masaharu NAKAGAWA, Hidetaka SAK ...
2008 Volume 27 Issue 2 Pages
179-186
Published: 2008
Released on J-STAGE: January 27, 2009
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This study examined the ability of a photocatalyst mixed in a denture base resin to decompose organic substances which adhered to the denture base resin surface. The photocatalyst was mixed with denture base resin at concentrations of 0, 5, 10, and 15% (w/w). Decomposition test, bending test, and surface roughness measurement were performed at 1, 7, 30, 90, and 180 days after polymerization. Decomposition ability was evaluated based on the residual amount of methylene blue (MB) dissolved in ethanol after UV irradiation for 12 hours. As the mixing ratio increased, the amount of MB in the solution decreased. Meanwhile, no changes in the amount of MB in the immersion solution were observed in the photocatalyst-free resin specimen. Therefore, the results indicated that a denture base resin containing a photocatalyst might have a photocatalytic ability.
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Meu ARIYOSHI, Toru NIKAIDO, Ayako OKADA, Richard M. FOXTON, Junji TAGA ...
2008 Volume 27 Issue 2 Pages
187-194
Published: 2008
Released on J-STAGE: January 27, 2009
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This study evaluated the tensile bond strengths of three adhesive/composite core materials to bovine dentin using three different curing units. Bovine dentin surfaces were ground with 600-grit SiC paper. Bonding area was demarcated with a vinyl tape (4-mm-diameter hole). Three adhesive/composite core systems—S6054 (experimental), UniFil Core, and Clearfil DC Core Automix—were used with three curing units—Curing Light XL3000 (quartz-tungsten-halogen), Hyper Lightel (high-power quartz-tungsten-halogen), and LEDemetron1 (blue light-emitting diode)—according to manufacturers' instructions. After 24 hours of storage in water at 37°C, tensile bond strengths were measured at a crosshead speed of 2 mm/min. Results were statistically analyzed with one-way ANOVA and Tukey′s HSD test (p<0.05). Highest tensile bond strength was obtained using Clearfil DC Core Automix with Hyper Lightel.
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Ovul KUMBULOGLU, Mutlu ÖZCAN, Atilla USER
2008 Volume 27 Issue 2 Pages
195-202
Published: 2008
Released on J-STAGE: January 27, 2009
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This study compared the fracture strengths and analyzed the failure types of direct, surface-retained, anterior fixed-partial-dentures (FPD), reinforced with four types of fiber-reinforced composites (FRC)
versus non-fiber-reinforced FPDs made of three particulate filler composites (PFC). To this end, surface-retained anterior FPDs (N=70, 10 per group) were prepared and divided into seven experimental groups, where Group 1: FRC1 (everStick)+PFC1 (Clearfil Photo Posterior); Group 2: FRC2 (BR 100)+PFC1; Group 3: FRC3 (Interling)+PFC1; Group 4: FRC4 (Ribbond)+PFC1; Group 5: PFC1 only; Group 6: PFC2 only (Sinfony); and Group 7: PFC3 only (Estenia). Fracture strength test was performed after water storage at 37°C for three days (universal testing machine, 1 mm/min). No significant differences were found among the four FRC types veneered with PFC1 (1490±548—1951±335 N) (p<0.05) (ANOVA, Tukey′s test). Among all the experimental groups, PFC1 presented a significantly higher mean value (2061±270 N) than PFC2 (1340±395 N) (p<0.05) and all the other FRC-reinforced groups (p<0.05). Complete pontic fracture was 100% and 70% for PFC2 and PFC3 respectively.
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Keisuke NAKAMURA, Yukyo TAKADA, Masanobu YODA, Kohei KIMURA, Osamu OKU ...
2008 Volume 27 Issue 2 Pages
203-210
Published: 2008
Released on J-STAGE: January 27, 2009
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This study was an examination of the galvanic corrosion of ferritic stainless steels, namely SUS 444, SUS XM27, and SUS 447J1, in contact with a Fe-Pt magnet. The surface area ratio of each stainless steel to the Fe-Pt magnet was set at 1/1 or 1/10. Galvanic corrosion between the stainless steels and the magnet was evaluated by the amount of released ions and the electrochemical properties in 0.9% NaCl solution. Although each stainless steel showed sufficient corrosion resistance for clinical use, the amount of ions released from each tended to increase when the stainless steel was in contact with the magnet. When the surface area ratio was reduced to 1/10, the amount of Fe ions released from the stainless steels increased significantly more than when there was no contact. Since contact with the magnet which possessed an extremely noble potential created a very corrosive environment for the stainless steels, 447J1 was thus the recommended choice against a corrosion exposure as such.
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Michio SHIMAKURA, Tomohisa NAGATA, Misao TAKEUCHI, Toru NEMOTO
2008 Volume 27 Issue 2 Pages
211-215
Published: 2008
Released on J-STAGE: January 27, 2009
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The purpose of this study was to investigate the clinical application possibility of pure titanium konus telescope crowns fabricated using a CAD/CAM system. For the CAD/CAM system, Dental Cadim (Advance Co.) was used. For the material, exclusive pure titanium block for this system was used in this experiment. Two types of experimental dies with different heights assumed the konus inner crown and three types of konus outer crowns with different gap widths at the occlusal part were prepared. The outer crown was seated on the inner crown die, and a load was applied perpendicularly to the upper surface of the outer crown for 10 seconds. Pullout test was performed at a crosshead speed of 5 mm/min, and the retentive force was measured. With increase in the height of the inner crown die and the applied load, the retentive force of konus telescope crown increased. Similarly, as the gap width at the occlusal part between the inner crown die and outer crown increased, the retentive force of konus telescope crown also increased.
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Masafumi KIKUCHI, Masatoshi TAKAHASHI, Osamu OKUNO
2008 Volume 27 Issue 2 Pages
216-220
Published: 2008
Released on J-STAGE: January 27, 2009
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This study investigated the machinability of experimental Ti-Ag alloys (5, 10, 20, and 30 mass% Ag) as a new dental titanium alloy candidate for CAD/CAM use. The alloys were slotted with a vertical milling machine and carbide square end mills under two cutting conditions. Machinability was evaluated through cutting force using a three-component force transducer fixed on the table of the milling machine. The horizontal cutting force of the Ti-Ag alloys tended to decrease as the concentration of silver increased. Values of the component of the horizontal cutting force perpendicular to the feed direction for Ti-20%Ag and Ti-30%Ag were more than 20% lower than those for titanium under both cutting conditions. Alloying with silver significantly improved the machinability of titanium in terms of cutting force under the present cutting conditions.
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Nicoleta ILIE, Reinhard HICKEL
2008 Volume 27 Issue 2 Pages
221-228
Published: 2008
Released on J-STAGE: January 27, 2009
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Despite good clinical acceptance, photoinitiating systems based on camphorquinone and amines raise concerns in terms of yellowing, aging, toxicity, or degradation in low pH conditions. This study aimed to prove whether CQ could be successfully replaced by alternative initiators in adhesive systems. Further, the efficiency of a prototype dual-wavelength LED (=Light Emitting Diode) curing unit was analyzed.
In two commercial adhesive systems, CQ was completely replaced by Lucirin TPO. The commercial adhesives and their experimental counterparts were evaluated after curing for 10 seconds and 20 second with two dual-wavelength LED units and one regular LED unit, by applying the curing unit on the adhesive surface at two distances of 0 mm and 5 mm. Degree of cure and mechanical properties (Vickers hardness and modulus of elasticity) were assessed after 24-hour storage in distilled water at 37°C.
Experimental data showed that the CQ-amine system could be completely replaced by Lucirin TPO when dual-wavelength LED unit was used for photoactivation.
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Chikako SUZUKI, Hiroyuki MIURA, Daizo OKADA, Wataru KOMADA
2008 Volume 27 Issue 2 Pages
229-236
Published: 2008
Released on J-STAGE: January 27, 2009
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The purpose of this study was to identify crown materials and luting agents that would decrease the stress concentrated at the roots of endodontically treated teeth. To this end, natural tooth model (NT), full cast crown model (gold-silver-palladium alloy; MC), polymer-based restorative material crown model (HCC), and all-ceramic crown model (ACC) were constructed. In each model, methyl methacrylate-based resin cement (MMA) and composite cement (CC) were used as luting agents. The magnitudes of von Mises stress of the roots during function were compared. When the luting agent was changed from MMA to CC, von Mises stress in the cervical area decreased by 37.8 % for MC, 27.1 % for HCC, and 37.0 % for ACC. Within the limitations of this study, the combination of HCC and CC gave rise to the lowest stress concentration at the cervical area.
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Noriko TAKAHASHI, Yukyo TAKADA, Osamu OKUNO
2008 Volume 27 Issue 2 Pages
237-242
Published: 2008
Released on J-STAGE: January 27, 2009
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In this study, we examined the corrosion behavior of dental precious alloys and magnetic stainless steels, namely SUS 444, SUS XM27, and SUS 447J1, used for dental magnetic attachments. Their galvanic corrosion behavior was evaluated from the viewpoint of corrosion potentials when they were in contact with each other. Rest potentials of the precious alloys were constantly higher than those of magnetic stainless steels. Since most gold alloys raised the corrosion potential more significantly than silver alloys did, silver alloys seemed to be better suited than gold alloys for combination with magnetic stainless steels. However, all corrosion potential values were sufficiently lower than the breakdown potentials of the stainless steels and existed within their passive regions. Based on the findings of this study, SUS XM27 and SUS 447J1 — which exhibited higher breakdown potentials than SUS 444 — emerged as the preferred choices for combination with gold alloys.
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Amornrat WONGLAMSAM, Kiyoshi KAKUTA, Hideo OGURA
2008 Volume 27 Issue 2 Pages
243-250
Published: 2008
Released on J-STAGE: January 27, 2009
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The effects of occlusal cycles and brushing cycles on wear of composite resins were investigated using a combined wear test, which carried out occlusal and toothbrush wear tests alternately. Worn volume and maximum worn depth were measured to evaluate wear under four combinations of two different cycles (occlusal cycles: 50 and 150 cycles; brushing cycles: 20 and 50 cycles).
With composite resin APX, which consisted of relatively large and irregular-shaped filler particles, its worn volume and worn depth significantly increased with the number of occlusal cycles. With composite resin Z100, which consisted of relatively small and irregular-shaped filler particles, its wear values significantly increased with both brushing and occlusal cycles. With composite resin SRE, which consisted of small, irregular-shaped, inorganic filler particles and large organic filler particles, its worn volume significantly increased with the occlusal cycle when under a lower brushing cycle. With composite resin SDX, which consisted of spherical inorganic filler particles and large organic filler particles, its wear was not influenced by increases in both brushing and occlusal cycles.
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Tetsurou ODATSU, Takashi SAWASE, Kohji KAMADA, Yohsuke TAIRA, Takanobu ...
2008 Volume 27 Issue 2 Pages
251-257
Published: 2008
Released on J-STAGE: January 27, 2009
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The purpose of this study was to investigate the effect of modifying aluminum oxide slips with magnesium oxide (MgO) to create a jointing material for In-Ceram
® Alumina. Jointed In-Ceram
® Alumina bars with In-Ceram
® Alumina slips containing 0—1.0 mass% MgO were examined by a three-point bending test. Joint-free bars were also tested as controls. Fracture surfaces were evaluated by scanning electron microscopy. In addition, linear shrinkage and fracture toughness were assessed.
The 0.3 mass% MgO group showed the highest flexural strength among the jointed groups, and there were no statistical differences between the joint-free control groups. The fracture surface of 0.3 mass% MgO group showed increased sintering densification with reduced micropore size. No linear shrinkage was observed with the addition of MgO to the alumina slip. Added MgO was also effective in boosting fracture toughness. The present findings indicate that the MgO-supplemented binding material is useful for clinical applications.
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Kiyoshi TAJIMA, Masahisa HIRONAKA, Ker-Kong CHEN, Yuki NAGAMATSU, Hiro ...
2008 Volume 27 Issue 2 Pages
258-265
Published: 2008
Released on J-STAGE: January 27, 2009
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A newly developed electropolishing system, equipped with an original agitation function for an electrolyte and using a safe electrolyte composed of an alcoholic solution, was applied for wrought and cast CP titanium and its alloys. Surface roughness and morphology of the polished surfaces were then examined. Under an electrolytic condition of 70—75 V, 2.0 kA/m
2, and 30°C, wrought CP Ti and Ti-6Al-4V alloy achieved an apparent mirror-like finishing with an average surface roughness (Ra) of 0.03 and 0.12 μm respectively. Under the same condition, on the other hand, cast CP Ti and Ti-6Al-7Nb alloy produced rougher polished surfaces with average Ra values of 0.67—0.80 μm, and the finishing was apparently shiny, but not mirror-like. SEM observation of the polished surfaces showed that wrought CP Ti was even and completely featureless, while wrought Ti-6Al-4V alloy was pitted. For cast CP Ti, a needle-like phase containing traces of iron was observed on the polished surface.
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Zahra JABERI ANSARI, Alireza SADR, Maryam MOEZIZADEH, Roya AMINIAN, Am ...
2008 Volume 27 Issue 2 Pages
266-272
Published: 2008
Released on J-STAGE: January 27, 2009
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The aim of this study was to compare the bond strengths of three self-etching materials during one year of storage. Clearfil SE Bond (SE), Clearfil Protect Bond (PB), and Clearfil Tri-S Bond (TS) were used for bonding to dentin and enamel according to manufacturer's instructions. Microshear bond strength values were measured after 24 hours, six months, and one year. Two-way ANOVA showed that the interaction of material type and storage time was significant for dentin. At baseline, SE had the highest bond strength to dentin. There were no significant changes in bond strength for each material during the storage period, except for PB which showed increased bond strength to dentin after one year. All materials performed reliably after one year. However, the antibacterial and fluoride-releasing effects of PB would further contribute to the long-term clinical benefits of this material.
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Shigeaki KURATA, Kumiko MORISHITA, Kazuo SHIMOYAMA, Kozo UMEMOTO
2008 Volume 27 Issue 2 Pages
273-277
Published: 2008
Released on J-STAGE: January 27, 2009
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To improve the mechanical properties and to reduce the water sorption amount of denture base resins, the polymerization characteristics of three novel fluoro-substituted monomers (MAF-TBN, MAF-MAE, MAF-TBN) and three styrene-type monomers (PTBS, PEES, PACS) were studied, as well as the copolymerization of these monomers with MMA. Subsequently, the mechanical properties and water sorption of the copolymers prepared from these monomers and MMA were evaluated. The polymerization reactivity of the monomers by BPO was lower than MMA, except for PACS. However, the copolymerization reactivity of the monomers with MMA was good, except for MAF-TBN. The copolymer of MAF-MAE and MMA in three fluoro-substituted monomers and PACS and MMA in three styrene-type monomers showed similar mechanical properties and extremely low water sorption compared with those of PMMA.
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