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Tomonori WAKI, Takashi NAKAMURA, Toshio NAKAMURA, Soichiro KINUTA, Kaz ...
2006 Volume 25 Issue 1 Pages
1-6
Published: 2006
Released on J-STAGE: May 22, 2009
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In this study, the effect on the fracture load of inlay-retained composite fixed partial dentures (FPDs) caused by reinforcing them with fiber-reinforced composite (FRC) in different positions was examined. Experimental FPDs were fabricated using Estenia/ EG Fiber (Kuraray Medical) . Pontic reinforcement was then performed in one of the following three ways: reinforced the central area in a single line or in double straight lines, or reinforced the bottom in a curved line. The finding was that, when the area ranging from the connector to the bottom of the pontic was reinforced with FRC in a curved line, the fracture load of the FPDs tended to become higher. In addition, the FPDs fractured mainly at the veneering composite of the connector area. Based on the results of this study, it was concluded that reinforcement using FRC is effective, and that the veneering composite in the connector area needs to have sufficient strength to prevent the fractures.
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Yasushi SHIMADA, Vanthana SATTABANASUK, Alireza SADR, Yang YUAN, Zheng ...
2006 Volume 25 Issue 1 Pages
7-12
Published: 2006
Released on J-STAGE: May 22, 2009
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To investigate the bonding of tooth-colored indirect restorations to cervical dentin, shear bond strengths of bonded resin inlays to cervical dentin and mid-coronal dentin were investigated and compared. Indirectly fabricated composite inlays (Estenia) were cemented with a dual-cured resin cement (Panavia Fluoro Cement II) to either cervical or mid-coronal dentin. Resin cement was cured with or without light irradiation for 20 seconds. After 24-hour or one-week storage, the bonded inlays were subjected to a micro-shear bond test. The light-cure method showed significantly higher bond strengths to both dentin regions compared with the self-cure method. Further, significant improvement in bonding after one-week storage was found in the case of light-cure method rather than the self-cure method. Although the cervical dentin tended to show lower bond strength than mid-coronal dentin, significant difference between the two dentin regions was only found when the resin cement was light-cured and stored for only one day.
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Osamu MIYAKAWA, Seigo OKAWA, Masayoshi KOBAYASHI
2006 Volume 25 Issue 1 Pages
13-19
Published: 2006
Released on J-STAGE: May 22, 2009
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CP Ti was mirror-polished and then abraded with waterproof SiC papers of two different grit sizes: 16 and 3μm. As-polished and abraded surfaces were characterized by means of EPMA, XPS, XRD, and hardness test.
Oxygen in the mirror-polished surface was uniformly distributed at the lowest level. Comparatively, abrading with SiC papers increased the surface oxygen amount and hardness.
Owing to its excellent abrasivity, the coarse grit efficiently scratched the surface and hindered the regenerated oxide film from growing thick, but allowed only the metal-oxide interfacial gradient zone to extend. But, the fine grit merely rubbed the surface and allowed both the oxide film and interfacial zone to extend. Further, the surface appeared to be lightly yellow-colored, suggesting that the oxide film was thicker, probably within 10 nm, than the nominal one.
When compared with the bulk, the interfacial zone was rich in oxygen and therefore subjected to high coherency strain, which was introduced to relieve the great lattice mismatch between the outer and inner layers of titanium substrate. Effects of solute oxygen hardening and strain hardening were speculated to be responsible for the surface hardening of both SiC-abraded surfaces. In conclusion, abrading with a coarse grit led to accumulation of a high, non-uniform strain in the titanium substrate, thereby hardening the surface further.
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Kazuki SHIMADA, Motoko NAKAZAWA, Yoshiyuki KAKEHASHI, Hideo MATSUMURA
2006 Volume 25 Issue 1 Pages
20-25
Published: 2006
Released on J-STAGE: May 22, 2009
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The purpose of this study was to evaluate the influence of abutment materials on the color of IPS Empress 2 ceramic coping with different thicknesses. Ceramic coping specimens (12.0×12.0×0.8-2.0 mm) were fabricated from IPS Empress 2 material (Ingot-100, n=5/ group) . Abutment specimens were fabricated from a build-up composite, a gold alloy, or a silver-palladium alloy. Color was evaluated using a colorimeter according to the CIE L
*a
*b
* system. The L
*a
*b
* values of the ceramic coping specimens of different thicknesses on each abutment specimen were measured. Following which, the color difference (ΔE
*ab) values between the ceramic coping specimens on various abutment specimens were calculated. Significant differences in ΔE
*ab value were observed among different abutment specimens at certain ceramic coping thicknesses (P<0.05). Thus, it was concluded that the color of IPS Empress 2 coping material was influenced significantly by both the thickness of the coping and the color of the abutment material.
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Naoko KAMISHIMA, Takatsumi IKEDA, Hidehiko SANO
2006 Volume 25 Issue 1 Pages
26-31
Published: 2006
Released on J-STAGE: May 22, 2009
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The purpose of this study was to evaluate the effect of the covering enamel layer of various thicknesses on the color of layered resin composites (LRC). To this end, the CIELAB parameters of the following were evaluated: underlying base (ULB: 2.0 mm of body shade + 3.0 mm of opaque shade), inherent color of the enamel shade (4.0 mm of enamel shade + ULB), and LRC disks (0.5, 1.0, 2.0, 3.0 mm of enamel shade + ULB) of Filtek Supreme (FS, 3M) and Gradia Direct (GD, GC). To assess the effect of the enamel layer on the color of LRC, color difference between ULB and LRC was calculated. With FS, the enamel layer had no major effect on the color of LRC - regardless of thickness. With GD, the enamel layer had a significant effect on the color of LRC, even if the thickness was only 0.5 mm. The difference in enamel layer effect between the two products could be attributed to the difference in color characteristics of the two enamel shades.
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Makoto TAMURA, Kazuhiko ENDO, Takeo MAIDA, Hiroki OHNO
2006 Volume 25 Issue 1 Pages
32-38
Published: 2006
Released on J-STAGE: May 22, 2009
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Thermally induced liquid-phase deposition method was employed to produce a thin hydroxyapatite (HA) film on a titanium substrate in a metastable calcium phosphate solution. Titanium foil of 100×10×0.02 mm
3 was used as a substrate. Prior to HA coating, the substrate was immersed in 5 M NaOH solution at 60°C for 24 hours. Substrate temperature was kept constant at 60°C for 0.5-3 hours by electrical heating with a DC power source in the metastable calcium phosphate solution.
An X-ray diffractogram indicated that the film deposited on the titanium substrate was composed of HA. The amount of HA deposited increased with increase in heating time. These results suggested that a uniform HA film can be formed by simple chemical and thermal treatments. Based on the results of this study, this technique seemed to be useful for producing uniform HA coatings on complex-shaped and porous dental implants.
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Nuran YANIKOGLU, Saip DENIZOGLU
2006 Volume 25 Issue 1 Pages
39-44
Published: 2006
Released on J-STAGE: May 22, 2009
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In this study, we investigated the effect of different solutions - coffee, tea, Turkish coffee, artificial saliva, mouthwash, denture cleanser, and distilled water - on the bond strength of soft lining materials (one acrylic- and three silicone-based) to acrylic resin. Acrylic specimens (40×10×10 mm) were prepared for the bond strength test. The specimens were stored in different solutions and tested after 24 hours, seven days, and 30 days.
Using analysis of variance, the bond strength of soft lining materials to acrylic resin was found to be related to the type of material, storage time, and storage solution. Visco-gel had the lowest bond strength to cured acrylic resin, where its strength ranged from 0.149 MPa to 0.784 MPa. The bond strength of Visco-gel was also found to increase with time.
Molloplast-B and Ufi Gel P demonstrated better bond strength than Visco-gel and Mollosil
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Nipaporn WATTANAWONGPITAK, Takako YOSHIKAWA, Michael F. BURROW, Junji ...
2006 Volume 25 Issue 1 Pages
45-50
Published: 2006
Released on J-STAGE: May 22, 2009
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This study evaluated the effect of two adhesive systems and four resin-based composites on the marginal sealing and cavity wall adaptation of restorations with different C-factors. Cylindrical cavities, 1 mm deep and 3 mm in diameter (C-factor=2.3) or 2 mm in diameter (C-factor=3) , were prepared on superficial bovine dentin surfaces. The teeth were restored with Clearfil SE Bond or Single Bond adhesive system followed by hybrid (Photo Clearfil Bright or Z100) or flowable (Filtek Flow or Estelite LV) resin composite. After thermocycling, a dye penetration test was carried out to evaluate the degree of marginal leakage and cavity-wall gap formation. Cavity-wall gap formation increased when the C-factor increased from 2.3 to 3, except for Estelite LV resin composite. In terms of marginal sealing, Clearfil SE Bond showed better performance than Single Bond. When using Clearfil SE Bond, flowable composites improved resin composite adaptation to the cavity wall compared with hybrid composites.
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Melvin L. MUNAR, Koh-ichi UDOH, Kunio ISHIKAWA, Shigeki MATSUYA, Masah ...
2006 Volume 25 Issue 1 Pages
51-58
Published: 2006
Released on J-STAGE: May 22, 2009
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Porous hydroxyapatite (HAP) foam permits three-dimensional (3D) structure with fully interconnecting pores as well as excellent tissue response and good osteoconductivity. It is therefore thought to be a good candidate as scaffold material for bone regeneration and as a synthetic bone substitute material. To fabricate better porous HAP foam, improved physical and structural properties as well as higher osteoconductivity are desired. In the present study, the effects of sintering temperature on the physical and compositional properties of porous HAP foam were evaluated by employing high sintering temperature starting at 1,300°C up to 1,550°C. The mechanical strength of porous HAP foam increased with sintering temperature to reach the maximum value at 1,525°C, then decreased slightly when sintering temperature was further increased to 1,550°C. Alpha tricalcium phosphate (α-TCP) was formed, and thus the porous HAP foam became biphasic calcium phosphate. Biphasic calcium phosphate consisting of both α-TCP and HAP had been reported to show higher osteoconductivity than HAP alone. We therefore recommend 1,500-1,550°C as the sintering temperature for porous HAP foam since this condition provided the most desirable physical properties with biphasic calcium phosphate composition.
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Alp Erdin KOYUTURK, Abdulkadir SENGUN, Fusun OZER, Yagmur SENER, Alpar ...
2006 Volume 25 Issue 1 Pages
59-65
Published: 2006
Released on J-STAGE: May 22, 2009
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The purpose of this study was to evaluate the bonding ability of five current self-etching adhesives to caries-affected dentin on the gingival wall. Seventy extracted human molars with approximal dentin caries were employed in this study. In order to obtain caries-affected dentin on the gingival wall, grinding was performed under running water. Following which, specimens mounted in acrylic blocks and composite resins of the bonding systems were bonded to dentin with plastic rings and then debonded by shear bond strength. With Clearfil SE Bond, bonding to caries-affected dentin showed the highest bond strength. With Optibond Solo Plus Self-Etch, bonding to caries-affected dentin showed higher shear bond strength than AQ Bond, Tyrian SPE & One-Step Plus, and Prompt-L-Pop (p<0.05) . Further, the bond strengths of Clearfil SE Bond and Optibond Solo Plus Self-Etch to sound dentin were higher than those of Prompt-L-Pop, AQ Bond, and Tyrian SPE & One-Step Plus (p<0.05) . In conclusion, besides micromechanical interlocking through hybrid layer formation, bond strength of self-etch adhesives to dentin may be increased from additional chemical interaction between the functional monomer and residual hydroxyapatite. The results of this study confirmed that differences in bond strength among self-etching adhesives to both caries-affected and sound dentin were due to chemical composition rather than acidity.
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Haruka YOKOTA, Shisei KUBO, Hiroaki YOKOTA, Masahiro OHSAWA, Yoshihiko ...
2006 Volume 25 Issue 1 Pages
66-74
Published: 2006
Released on J-STAGE: May 22, 2009
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This study investigated the effect of a caries-detecting solution on the tensile bond strength (TBS) to sound bovine dentin - which was either rinsed thoroughly of or contaminated with the caries-detecting solution.
Caries Detector (1.0% acid red in propylene glycol) was applied on flat dentin surfaces for 10 seconds, rinsed, and dried with syringe air. In another group, Caries Detector was not rinsed but air-dried. Then, the surfaces were treated with one of the following adhesive systems: Clearfil Protect Bond, Clearfil SE Bond, One-Up Bond F, or Single Bond. Furthermore, an ingredient of Caries Detector, either 1.0% acid red aqueous solution or propylene glycol, was applied to evaluate the effect of each component. In the control groups, Caries Detector was not applied to the dentin surfaces. Finally, a resin composite was light-cured and the TBS measured. Fractured specimens and treated dentin surfaces were observed by SEM. Caries Detector did not reduce the tensile bond strength of any adhesive system (p>0.05) when rinsed thoroughly. On the other hand, when dentin surface was contaminated with Caries Detector, TBS decreased significantly with Clearfil SE Bond and Single Bond. As for the ingredients of Caries Detector, the effect of acid red on TBS was not significant, but that of propylene glycol was significant
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Goro NISHIGAWA, Yukinori MARUO, Makoto OKAMOTO, Kazuhiro OKI, Yoshihir ...
2006 Volume 25 Issue 1 Pages
75-80
Published: 2006
Released on J-STAGE: May 22, 2009
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Despite progress in the development of denture base resin and artificial tooth materials, dental clinics are still plagued with artificial teeth falling off the denture base - due to poor bond strength - after denture delivery. Against this background, this study sought to examine the effect and durability of an adhesive primer developed exclusively for heat-curing resin on the adhesive strength of heat-curing denture base acrylic resin to plastic artificial tooth. Test specimens were divided into four groups according to the treatment method of the artificial tooth's test bonding surface: air abrasion, adhesive primer application, adhesive primer application after air abrasion, and pretreatment only (control) . After heat curing of acrylic resin onto the bonding surface, shear test was performed for two storage periods: 24-hour versus 100-day water storage. From the results obtained, it was revealed that the evaluated adhesive primer was significantly effective in increasing adhesive strength between artificial tooth and acrylic resin, although specimens were stored in water for 100 days.
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Murat TÜRKÜN, L. Sebnem TÜRKÜN, Esra Uzer Ç ...
2006 Volume 25 Issue 1 Pages
81-86
Published: 2006
Released on J-STAGE: May 22, 2009
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The aim of this study was to compare the antibacterial activities of Er,Cr:YSGG laser with two different power outputs against a chlorhexidine gluconate-based cavity disinfectant. A cavity tooth model test was used to determine the antibacterial activity. Four cylindrical cavities were prepared on the dentin surface of 10 bovine incisors and left in contact with
Streptococcus mutans for 72 hours to allow bacterial invasion. Following which, Er,Cr:YSGG laser with 0.75 W and 1 W power outputs and a chlorhexidine gluconate-based cavity disinfectant were applied separately on one of the three infected cavities, whereas the fourth was left untreated for control. Standardized amounts of dentin chips were obtained from the cavity walls, and the number of bacteria recovered was counted. Statistical analysis was carried out using one-way ANOVA and Dunnett's C test (p=0.05). No significant differences were observed among the data obtained from the chlorhexidine gluconate-based cavity disinfectant and the two Er,Cr:YSGG laser groups (p>0.05) . However, when compared to the control group, both Er,Cr:YSGG laser groups and the chlorhexidine gluconate-based cavity disinfectant resulted in significantly less bacterial recovery (p<0.05). In conclusion, the antibacterial activity on
S. mutans demonstrated by Er,Cr:YSGG laser with both energy outputs was similar to that of the tested chlorhexidine gluconate-based cavity disinfectant.
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Masakazu MURAI, Shuichi SATO, Yasumasa FUKASE, Yutaka YAMADA, Kazuo KO ...
2006 Volume 25 Issue 1 Pages
87-96
Published: 2006
Released on J-STAGE: May 22, 2009
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This study evaluated the effects of different sizes of β-TCP particles on bone augmentation within a titanium cap. In 20 rabbits, the calvarium was exposed and a circular groove was prepared. After marrow penetration, a standardized hemispherical titanium cap was placed in the circular grove. The cap was filled with small-sized (100-250μm) or medium-sized (250-500μm) β-TCP particles for the experimental site and without β-TCP for the control site. After one and three months of healing, the animals were euthanized and examined histologically. There was a statistically significant difference in the amount of mineralized bone generated between the experimental and control groups in the three-month specimens. Furthermore, the medium-sized particles showed significantly more mineralized bone than did the small-sized particles. Based on these findings, we suggested that β-TCP might be effective for bone formation and that medium-sized particles are more useful than small-sized particles in bone maturation.
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Rena MARUOKA, Toru NIKAIDO, Masaomi IKEDA, Tomoyasu ISHIZUKA, Richard ...
2006 Volume 25 Issue 1 Pages
97-103
Published: 2006
Released on J-STAGE: May 22, 2009
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The purpose of this study was to evaluate coronal leakage inhibition using a resin-coating technique after endodontic treatment. Thirty-six human incisors were cut at the cementoenamel junction, and endodontic obturations were performed. The specimens were randomly divided into three groups according to post space preparation (10 mm depth) , resin coating, and temporization. For the resin coating, the dentin surface was coated with either a combination of Clearfil SE Bond and Protect Liner F (SE/ PLF) or RZII (RZ). Then, the specimens were stored in 37°C distilled water for 24 hours and placed in 1% methylene blue solution for 48 hours. After which, the specimens were sectioned faciolingually along the root canal and the length of dye penetration was measured from the cementoenamel junction. Three-way ANOVA revealed that the dye penetration scores were influenced by post space preparation, resin coating, and temporization. Resin coating with RZ significantly reduced the dye penetration score and SE/ PLF completely eliminated dye penetration.
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Yoshinari MATONO, Masaharu NAKAGAWA, Shigeki MATSUYA, Kunio ISHIKAWA, ...
2006 Volume 25 Issue 1 Pages
104-112
Published: 2006
Released on J-STAGE: May 22, 2009
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The corrosion behaviors of Ti, Ti-6Al-7Nb and Ti-6Al-4V alloys, and an experimentally produced Ti-0.5Pt alloy in 0.05% to 2.0% concentrations of Acidulated Phosphate Fluoride (APF) solutions (corresponding to 226 to 9,050 ppm fluoride at pH 3.5 or 3.6) were examined. While the corrosion of Ti, Ti-6Al-7Nb and Ti-6Al-4V alloys might occur easily even in a diluted 0.05% APF solution, dissolution of Ti from the Ti-0.5Pt alloy was observed only in test solutions with APF concentration exceeding 0.2%. When Ti-6Al-7Nb and Ti-6Al-4V alloys were immersed in 2.0% APF solution, their surfaces were entirely covered by compact corrosion products of Na
3TiF
6 due to severe corrosion. As a result, Ti dissolution was prevented and the amount of Ti dissolved decreased. However, since Ti was covered by porous, large-sized corrosion products of Na
3TiF
6 and that Ti-0.5Pt alloy was not covered with any corrosion product, the amount of Ti dissolved increased in the 2.0% APF solution.
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Tatiana Nogueira Rocha CLEMENTINO-LUEDEMANN, Karl-Heinz KUNZELMANN
2006 Volume 25 Issue 1 Pages
113-119
Published: 2006
Released on J-STAGE: May 22, 2009
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This study aimed to evaluate a commercial micro-CT system (μCT 20) for quantitative analysis of mineral concentration in human enamel and dentin using different methodologies, and thereby compare the obtained results with established data from published literature. A micro-CT device set at 50 kVp (160μA) was used to scan five whole molars (G1) and five molars ground to 6-mm thickness (G2) , as well as evaluate the mineral concentration of the samples. Mean mineral contents for enamel and dentin were 2.57 (±0.12) and 1.53 (±0.12) g/ cm
3 for G1, and 2.76 (±0.03) and 1.45 (±0.02) g/ cm
3 for G2. Difference between the groups was significant for enamel. For dentin, there was a clear although not significant tendency towards higher values with G1. The equipment could identify and differentiate a higher mineral content of the tooth enamel and dentin from the external to the inner tissue. Further, the absolute mean values of mineral concentration were lower in whole tooth samples than in sectioned samples due to beam hardening. In conclusion, the equipment is well suited for quantifying the mineral content of teeth. However, it is necessary to consider the limited acceleration voltage of the μCT 20 system and to limit sample evaluation to 6-mm thickness.
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Youhei TSUCHIMOTO, Yasuhiro YOSHIDA, Atsushi MINE, Mariko NAKAMURA, No ...
2006 Volume 25 Issue 1 Pages
120-124
Published: 2006
Released on J-STAGE: May 22, 2009
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The purpose of this study was to investigate the effect of a 4-MET- and 10-MDP-based primer on the bond strength of two resin cements (SuperBond C&B, Sun Medical; Panavia Fluoro Cement, Kuraray) to titanium (Ti). Ti plates were treated with six experimental primers consisting of, respectively, 10-MDP and 4-MET in concentrations of 0.1, 1 and 10wt%, or were kept untreated (control). The highest tensile bond strength of Panavia Fluoro Cement to Ti was obtained when the Ti surface was pre-treated with 10wt% 10-MDP and was significantly higher than that when a lower concentrated 10-MDP-based primer or any 4-MET-based primer was used. On the contrary, no significant difference in tensile bond strength of SuperBond C&B was found for the untreated and six pre-treated Ti surfaces, although pre-treatment with each 10-MDP-based primer resulted in a higher tensile bond strength as compared to any 4-MET pre-treatment. Altogether, the data obtained strongly suggest that 10-MDP is effective to improve the adhesive performance of resin to titanium.
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Yo OMATA, Shigeru UNO, Yasuko NAKAOKI, Toru TANAKA, Hidehiko SANO, Shi ...
2006 Volume 25 Issue 1 Pages
125-131
Published: 2006
Released on J-STAGE: May 22, 2009
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This study examined the surface staining mechanism of a photopolymerized composite by coffee, oolong tea, and red wine.
Dental composite was subjected to an experimental 24-hour staining cycle: 17-hour immersion in artificial saliva solution containing 0.3% mucin followed by 7-hour immersion in coffee, tea, or wine. After one, two, and four weeks, digital images of the composite surface were analyzed in grayscale mode with an imaging analyzer. Specimens polished but not immersed were used as a baseline measurement for color change. Additionally, the effects of mechanical brushing and chlorhexidine on drink-induced staining were examined.
Wine caused the most severe staining, followed by tea and coffee. After four weeks of immersion, brushing reduced surface staining by wine. On the contrary, chlorhexidine increased the staining effect of tea and coffee (p<0.05) when compared to the control specimens. In conclusion, we showed that common drinks stained the dental composite, but each by a specific mechanism that depended on external conditions such as the presence of chlorhexidine.
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Xiangfeng MENG, Keiichi YOSHIDA, Mitsuru ATSUTA
2006 Volume 25 Issue 1 Pages
132-137
Published: 2006
Released on J-STAGE: May 22, 2009
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This study investigated the Knoop hardness of a thin layer in three dual-cured resin cements (Linkmax HV, Nexus 2, and Variolink II HV) irradiated through or not through different thicknesses (1 through 5 mm) of a machinable ceramic. Hardness was recorded at a series of time intervals up to five days, starting from the end of a light irradiation period. Increase in hardness was more rapid over the first 0.5 hour; thereafter it continued at a low rate until maximum hardness was attained. Ceramic thickness had a significant influence on hardness in all dual-cured resin cements, especially when ceramic thickness was more than 4 mm. In addition, it was noted that the polymerization of Nexus 2 seemed to be more dependent on light exposure compared with the other two materials. Variolink II HV and Linkmax HV, on the other hand, seemed to indicate the potential of being compensated by chemical curing to some degree.
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Tomonori MATSUNO, Tatsuo NAKAMURA, Koh-ichi KUREMOTO, Syunsuke NOTAZAW ...
2006 Volume 25 Issue 1 Pages
138-144
Published: 2006
Released on J-STAGE: May 22, 2009
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Synthetic biomaterials have been developed and used for bone grafting. Here, we developed a biodegradable sponge composite for bone tissue engineering by combining β-tricalcium phosphate (β-TCP) and collagen. In addition, we sought to determine the optimal β-TCP granules/ collagen ratio by evaluating and bone formation
in vivo. Porous β-TCP granules were mixed with atelocollagen hydrochloride solution at various ratios — 0.02, 0.05, 0.1, and 0.2 g/ mL. The resultant mixtures were freeze-dried and subjected to dehydrothermal treatment
in vacuo. The final composites obtained were designated β-TCP/ collagen sponge composites (β-TCP/ CS) . Through compression testing, it was found that the stress values for β-TCP/ CS (0.2 g/ mL) were higher than those of the other three composites over the whole strain range. Histological evaluation at four weeks after implantation revealed that the collagen sponge had degraded and newly formed bone was present on the surface of the β-TCP granules. At 12 weeks, the β-TCP granules were completely degraded and remodeling of the lamellar bone was observed.
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Takashi NAKAMURA, Tatsuo OHYAMA, Tomonori WAKI, Soichiro KINUTA, Kazum ...
2006 Volume 25 Issue 1 Pages
145-150
Published: 2006
Released on J-STAGE: May 22, 2009
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Finite element analysis was performed to evaluate stress distribution in maxillary central incisors treated endodontically and restored with a post and an all-ceramic crown. Tensile stress at tooth root was analyzed using two-dimensional finite element models with different post diameters and lengths. One post length was 1/ 3 of the root (short) , while the other was 2/ 3 of the root (long) ; one post diameter was 1/ 3 of the root (narrow) , while the other was 2/ 3 of the root (wide) . The following combinations were used for posts and cores: gold alloy cast post and core, commercial stainless steel post and resin core, and fiber post and resin core. Results showed that the fiber post produced less stress on the root dentin around the post tip than did the metal posts. This finding thus suggested that to reduce the stresses that cause root fracture, a long, thin fiber post should be used.
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Osamu FUKUSHIMA, Takayuki YONEYAMA, Hisashi DOI, Takao HANAWA
2006 Volume 25 Issue 1 Pages
151-160
Published: 2006
Released on J-STAGE: May 22, 2009
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Ti-Ni alloy has been increasingly applied to medical and dental devices, such as coronary stents and orthodontic wires. This alloy contains nickel, which is known to give rise to cytotoxicity, metal allergy, and carcinogenicity. Therefore, the purpose of this study was to improve the corrosion resistance of Ti-Ni alloy by electrolytic treatment, whereby investigation was carried out using different acidic electrolyte compositions. As a result, specimens electrolyzed with lactic acid, water, and glycerol were found to show higher corrosion potential and release lower amount of titanium and nickel ions than mechanical-polished specimens (p<0.05) . With the electrolytic treatment, nickel concentration in the surface oxide layer of Ti-Ni alloy decreased, and the thickness of the surface oxide layer increased. Based on the results of this study, it was shown that electrolytic treatment with suitable electrolyte could improve the corrosion resistance of Ti-Ni alloy, which is effective to produce medical and dental devices that utilize shape memory effect or superelasticity with better biocompatibility.
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Masamichi NISHIOKA, Yoshihisa YAMABE, Kunihiro HISATSUNE, Hiroyuki FUJ ...
2006 Volume 25 Issue 1 Pages
161-165
Published: 2006
Released on J-STAGE: May 22, 2009
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The purpose of this study was to investigate the influence of the surface roughness of denture base resin and metal on wettability with water and saliva.
Solid specimens were produced using heat-curing denture base resin and Co-Cr alloy. After polymerizing or casting these materials, specimens with four different types of surface roughness were produced by a progressive polishing process using polishing papers (#240, #400, and #1,000) and cotton buffs.
Surface roughness decreased significantly as the polishing process progressed (p<0.0001) . Contact angle increased as surface roughness in metal specimens decreased, but decreased as surface roughness in resin specimens decreased (p<0.0001) . Furthermore, differences in contact angle between tap water and saliva were larger in metal specimens (p<0.0001) . These results suggested that with regard to the tissue surface of a denture base, the influence of its roughness on adhesive force differed according to the type of denture base material.
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Yumiko HOSOYA, Tetsuo OOTA, Masahiko NAGASAKA, Joel M. WHITE
2006 Volume 25 Issue 1 Pages
166-171
Published: 2006
Released on J-STAGE: May 22, 2009
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The purpose of this study was to observe the tooth colors and retention of a cosmetic veneer Fiche
® Pearl On containing shellac and five experimental formulations containing benzoin gum and ethyl cellulose. Tooth color was measured with a spectrophotometer before and after application of the veneers to the buccal or labial surface of experimental teeth. Through both
in vitro and
in vivo studies, the retention rates of veneers were assessed. In terms of color difference (ΔE
*ab) between before and after veneer application, it ranged from 4.3 (Fiche
® Pearl On) to 15.0 (experimental formulation White Plus). In terms of retention rate,
in vitro test found the retention rate of experimental formulation White Plus was significantly higher than that of Fiche
® Pearl On. In
in vivo test where subjects were permitted to drink water and tea, it was found that the retention rate after two hours ranged from 94.0 to 98.5%. In conclusion, teeth applied with the experimental cosmetic veneer formulations showed better color and retention than teeth with Fiche
® .
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Hisako HIRAGUCHI, Hisami NAKAGAWA, Mitsuru WAKASHIMA, Kohichi MIYANAGA ...
2006 Volume 25 Issue 1 Pages
172-176
Published: 2006
Released on J-STAGE: May 22, 2009
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This study investigated the effects of disinfecting alginate impressions on the scratch depth of resultant stone models. Eleven brands of alginate impression material and two disinfectants, 1% sodium hypochlorite and 2% glutaraldehyde, were used. Impressions were immersed in disinfectant solutions or stored in sealed bags after spraying with disinfectants, and then poured with a type V dental stone. The scratch depth of the stone model obtained from disinfected impression was measured. The storage of alginate impressions after spraying with disinfectants did not increase the scratch depth of resultant stone models. However, the effect of immersion in disinfectants on scratch depth varied with the brand of the alginate impression material.
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Wataru KOMADA, Hiroyuki MIURA, Daizo OKADA, Keiichi YOSHIDA
2006 Volume 25 Issue 1 Pages
177-182
Published: 2006
Released on J-STAGE: May 22, 2009
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This study evaluated the influence of alveolar bone level on the fracture resistance of root restored with post and core. Forty-eight extracted human mandibular premolars were divided into six groups. Cast posts and cores were cemented (MN8 and MP8) or resin cores were built up with fiber posts and composite resin (FN8, FP8, FN4, and FP4) . Post length was 8 mm (MN8, MP8, FN8, and FP8) or 4 mm (FN4 and FP4) . Specimens were embedded 2 mm (MN8, FN8 and FN4) or 5 mm (MP8, FP8 and FP4) below cement-enamel junction. All specimens were loaded at 45 degrees to the long axis until fracture. With normal bone model, cast post and core (MN8) showed the highest fracture resistance (2262.4 N) . However, in the resorbed bone model, there were no significant differences in fracture resistance between cast post and core and fiber post with composite resin.
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Mihoko KON, Kiyoshi KAKUTA, Hideo OGURA
2006 Volume 25 Issue 1 Pages
183-194
Published: 2006
Released on J-STAGE: May 22, 2009
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Effects of occlusal and brushing forces on the wear of composite resins were investigated using three different wear tests: simulated occlusal wear test, toothbrush wear test, and combined wear test which carried out toothbrush wear test and occlusal wear test alternately. Test specimens were prepared from four commercial composite resins. Worn volume and maximum worn depth were measured under different occlusal forces (40 N and 80 N) and brushing forces (1.5 N and 3 N) in the three wear tests. Worn surfaces were observed using a SEM.
In all the three wear tests, both higher occlusal and brushing forces resulted in significantly greater worn volume and higher maximum worn depth. The effects of occlusal force on worn volume and maximum worn depth varied with different composites, indicating that the four tested composites showed different wear behaviors under different occlusal forces and brushing forces. It was suggested that their different wear behaviors most probably stemmed from the differences in their filler systems.
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