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Bart VAN MEERBEEK, Kirsten VAN LANDUYT, Jan DE MUNCK, Masanori HASHIMO ...
2005 Volume 24 Issue 1 Pages
1-13
Published: 2005
Released on J-STAGE: February 24, 2010
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Besides micro-mechanical interlocking through hybrid-layer formation, self-etch adhesives may benefit from additional chemical interaction between the functional monomer and residual hydroxyapatite. One-step adhesives are commonly associated with lower bonding effectiveness, which must be attributed in part to the dissolution of hydrophilic and hydrophobic monomers in a relatively highly concentrated solvent. In this ‘difficult’ mixture, also water is essential as ionization medium to enable self-etching activity. Due to the high hydrophilicity, one-step self-etch adhesives have been reported to behave as semi-permeable membranes, allowing fluids to pass through and seriously jeopardizing bond durability. Recent research has also revealed that HEMA-free one-step adhesives are prone to phase-separation, which may also account for their lower bonding effectiveness. Employing an appropriate air-drying technique may, however, improve the bonding effectiveness of such phase-separating adhesives by getting rid of substantially more interfacial water than HEMA-containing adhesives, of which water might be more difficult to remove from.
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Zutai ZHANG, Yukimichi TAMAKI, Yasuhiro HOTTA, Takashi MIYAZAKI
2005 Volume 24 Issue 1 Pages
14-18
Published: 2005
Released on J-STAGE: February 24, 2010
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Industrial waste is on the increase, resulting in severe environmental contamination. Against this background, this study sought to investigate the possibility of recycling used phosphate-bonded investments. Commercial phosphate-bonded investment was mixed and heated according to manufacturer's instructions, then powdered with a ball mill machine to be used as recycled investment (Code: R). Mono-ammonium phosphate (NH
4H
2PO
4) of 2, 5, 8, 11, and 14g were added to 100g of R because of residual MgO, and coded as Ra, Rb, Rc, Rd, and Re respectively. Investment properties were then examined. Particle size of R was 50.66μm and close to the original investment. It was found that more NH
4H
2PO
4 led to larger setting expansion, smaller thermal expansion, and lower fired strength. The data of Re in these three aspects were 1.42±0.09%, 0.78±0.21%, and 8.85±0.88MPa respectively, and differences against the original investment were significant. Ra showed significantly longer setting time than other investments. Based on the results of this study, we concluded that it was possible to set used phosphate-bonded investments by adding NH
4H
2PO
4; in particular, Rd showed suitable expansion and acceptable mechanical properties.
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Kohyoh SOENO, Shiro SUZUKI, Yohsuke TAIRA, Mitsuru ATSUTA
2005 Volume 24 Issue 1 Pages
19-23
Published: 2005
Released on J-STAGE: February 24, 2010
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The purpose of this study was to investigate the efficacy of an experimental dentin primer consisting of ascorbic acid (AA) and ferric chloride (Fe). Three exprimental primers—10wt%AA and 0.075wt%Fe (
i. e., 10AA-0.075Fe), 10AA-0Fe, and 0AA-0.075Fe—were prepared. Flattened dentin surfaces were first treated with phosphoric acid and NaClO, and subsequently primed using each experimental solution. Besides the experimental solutions, 10wt% citric acid and 3wt% ferric chroride (10CA-3Fe) was also used. A stainless steel rod was bonded to the dentin surface with Super-Bond C & B. 10CA-3Fe/Super-Bond C & B was then used as a control. Tensile bond strengths were evaluated after 24-hour immersion in water. 10AA-0.075Fe showed significantly high bond strength compared to 10AA-0Fe, 0AA-0.075Fe, 0AA-0Fe, and 10CA-3Fe. No significant differences were found between 10AA-0.075Fe and Super-Bond C & B system. The experimental primer consisting of 10wt% ascorbic acid and 0.075wt% ferric chloride improved the bonding between Super-Bond C & B and dentin conditioned with phosphoric acid and NaClO.
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Youhei HAMAKUBO, Takashi SAWASE, Keiichi YOSHIDA, Kohji KAMADA, Yohsuk ...
2005 Volume 24 Issue 1 Pages
24-29
Published: 2005
Released on J-STAGE: February 24, 2010
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To investigate the pre-clinical relevancy of a machinable composite, its physical properties were evaluated and compared with a machinable ceramic and two indirect composites. A machinable resin composite (GN-I composite, CO), a machinable ceramic (GN-I ceramic, CE), and two resin composites (Artglass dentin, AG; Estenia dentin, ET) were used. Compressive strength, diametral tensile strength, flexural strength, elastic modulus, and fracture load of standardized, premolar crown-shaped specimens were determined. In terms of compressive strength, diametral tensile strength, and flexural strength, AG showed significantly lower values than the other three materials. In terms of fracture load, specimens with 1.5mm thick wall showed a higher value than those with 1.0mm thick wall, and the value decreased in the order of ET, CE, CO, and AG. Marginal tipping was also observed in ET and CE. Within the limits of the current study, CO showed physical properties favorable for constructing esthetic restorations.
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Daijiro MEGURO, Tohru HAYAKAWA, Kayo SAITO, Mayuko KAWASAKI, Kazutaka ...
2005 Volume 24 Issue 1 Pages
30-35
Published: 2005
Released on J-STAGE: February 24, 2010
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The purpose of this study was to determine the bonding durability when orthodontic bracket was bonded to human enamel using a MMA-based resin (Multibond) with two types of commercially available self-etching primer—Multibond and Megabond. Multibond primer contained a polymerization initiator, but Megabond primer did not. No significant differences in shear bond strength were observed between Multibond and Megabond primers after immersion in water at 37°C for 24 hours (before thermal cycling). Multibond primer produced no significant decrease in shear bond strength after 2000 and 5000 thermo-cycles between 5°C and 55°C. On the contrary, Megabond primer showed significant decrease in shear bond strength after thermal cycling. The present study suggested that if Multibond resin were to be used for bonding orthodontic brackets, difference in self-etching primer's components would influence shear bond strength after thermal cycling.
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Hisako HIRAGUCHI, Hisami NAKAGAWA, Mitsuru WAKASHIMA, Kohichi MIYANAGA ...
2005 Volume 24 Issue 1 Pages
36-42
Published: 2005
Released on J-STAGE: February 24, 2010
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This study investigated the effect of storage period on dimensional change and deformation of stone models to determine an acceptable period of alginate impression storage in a sealed bag after spraying with disinfectant solution. Two alginate impression products: Aroma Fine DFIII and Alginoplast EM, characterized by greater or smaller contraction in 100% relative humidity, were used. The impressions were sprayed with 1% sodium hypochlorite or 2% glutaraldehyde solution and then stored in sealed bags. The storage periods were 1 hour, 2 hours, 3 hours, and 4 hours. The sectional profiles of the stone models obtained from each impression were measured using a three-dimensional coordinate measuring system.
The results indicated that the impression characterized by greater contraction in 100% relative humidity should not be stored for even 1 hour, and that storage for up to 3 hours of the impression characterized by smaller contraction was clinically acceptable.
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Naomi TANOUE, Mitsuru ATSUTA, Shin-ichi KITAZAWA, Hiroyasu KOIZUMI, Hi ...
2005 Volume 24 Issue 1 Pages
43-48
Published: 2005
Released on J-STAGE: February 24, 2010
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We developed a new laboratory polymerizing unit (Twinkle MIII: M3) equipped with different light sources (a metal halide and two halogen lamps) that could illuminate independently. This study introduced the structure of the curing unit and examined the curing depth of a representative indirect composite (Artglass). The composite material was cured with the following modes: 1) M3-halogen only; 2) M3-metal halide only; 3) M3-both halogen and metal halide (HM); 4) conventional xenon; and 5) preliminary halogen. The results obtained from analysis of variances and post-hoc tests revealed that curing depth was affected significantly (p<0.05) by both exposure mode and time, and that HM mode exhibited the most favorable curing performance (p<0.05) among the curing units and polymerization modes. In conclusion, the M3 unit was found to be well suited to polymerizing the composite material tested.
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Motohiro UO, Mayumi OKAMOTO, Fumio WATARI, Kazutoshi TANI, Manabu MORI ...
2005 Volume 24 Issue 1 Pages
49-52
Published: 2005
Released on J-STAGE: February 24, 2010
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In recent dental care, esthetic restorative materials such as composite resin and porcelain have been widely used and studied. However, their good esthetics makes the visual inspection of restored teeth difficult. In this study, a fluorescent glass filler containing rare earth oxides—which are well-known fluorescent materials—was prepared and used in composite resin to enhance visual inspection capability with small change in color. For example, when irradiated with near ultraviolet light, an Eu
2O
3-containing filler fluoresced clearly and visibly. The fluorescence intensity of the prepared composite resin increased with increase of Eu
2O
3 content in the glass filler and with filler/resin ratio in the resin. Despite the clear fluorescence, the effect of Eu
2O
3 on the color change of composite resin was quite small—even when up to 10wt% Eu
2O
3 was added to the glass filler. Tb
4O
7- and Dy
2O
3-added fillers also showed clear fluorescence, just like Eu
2O
3-added filler. Therefore, fluorescent glass fillers for composite resins, resulting in small color change in the latter, were successfully prepared in this study.
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Hiroyuki KIBAYASHI, Fumio TERAOKA, Shinji FUJIMOTO, Masafumi NAKAGAWA, ...
2005 Volume 24 Issue 1 Pages
53-58
Published: 2005
Released on J-STAGE: February 24, 2010
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The purpose of this study was to investigate the effects on shear bond strength to resin after pure titanium (Ti) was exposed to plasma under different kinds of gas atmosphere. Polished Ti samples were treated using a plasma exposure apparatus in gas atmospheres of air, CO
2, and C
3F
8. Surface analysis of Ti exposed to plasma was achieved through surface free energy and XPS measurements. The Ti sample was bonded with adhesive resin (4-META, MAC-10, HEMA, MDP, VBATDT) to a stainless steel piece. After which, shearing adhesion test was done. It was observed that plasma exposure in a specific gas atmosphere in regulated the bonding strength of titanium surface to resin. Based on the results of this study, we concluded that plasma exposure was a useful surface treatment method for dental practices.
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Kozo NISHIMURA, Toru NIKAIDO, Richard M. FOXTON, Junji TAGAMI
2005 Volume 24 Issue 1 Pages
59-65
Published: 2005
Released on J-STAGE: February 24, 2010
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The purpose of this study was to evaluate the effect of air-powder polishing with sodium bicarbonate (SB) or crystalline cellulose (CC) on the bond strength of a self-etching primer bonding system to dentin. Ground human dentin surfaces were prepared using 600-grit SiC paper. The teeth were divided into three groups according to dentin treatment: control, air-powder polishing with SB, and air-powder polishing with CC. The dentin surfaces were bonded with a self-etching primer bonding system, followed by a light-cured resin composite. μTBS test and SEM analysis were performed. The results of μTBS test indicated that air-powder polishing with SB affected bond strength to dentin, while that with CC did not influence bond strength. SEM observation of air-polished dentin surfaces showed that dentin surfaces air-polished with SB were roughened and covered with a smear layer, while those with CC were smooth and the smear layer was removed.
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Motoko OKITSU, Hidekazu TAKAHASHI, Takatomo YOSHIOKA, Naohiko IWASAKI, ...
2005 Volume 24 Issue 1 Pages
66-69
Published: 2005
Released on J-STAGE: February 24, 2010
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The purpose of the present study was to analyze effective factors including periodontal ligament on vertical root fractures (VRFs) . Eighty maxillary central incisors were assigned to eight groups, depending on master apical file (MAF) size, loading point and existence of a simulated periodontal ligament (PDL) . The gutta-percha in the root canal was vertically pressed with a Co-Cr rod using a universal testing machine. An ordinal logistic analysis was employed to determine significant factors. VRFs were observed in 88.8% of the specimens but no horizontal fractures were found. There were three types of VRFs: partial fracture not involving the apex (PF, 41.3%), partial fracture involving the apex (AF, 40.0%), and complete fracture (CF, 7.5%). MAF size significantly affected VRFs (p<0.05); large MAF size exhibited more partial fractures involving the apex. Loading point and existence of PDL did not affect VRFs.
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Rena SHIMURA, Toru NIKAIDO, Monica YAMAUTI, Masaomi IKEDA, Junji TAGAM ...
2005 Volume 24 Issue 1 Pages
70-75
Published: 2005
Released on J-STAGE: February 24, 2010
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This study evaluated the influence of curing method and storage condition on the microhardness of dual-cure resin cements: Panavia F 2.0 (PF) and Nexus 2 (NX). The specimens were either light-cured (LC) or chemically cured in darkness (CC). After 24 hours of storage in dry chamber (Dry) or distilled water (DW), the specimens were sectioned and polished. The microhardness of resin cement matrix was measured using a nanoindentation tester (ENT-1100). The data (n=6) were statistically analyzed with t-test, two-way ANOVA (p<0.05), and Tukey HSD test (α=.05). It was found that the factors of curing method and storage condition had significant effect on microhardness. For both PF and NX, LC presented higher microhardness than CC, while DW showed higher microhardness than Dry. In conclusion, dual-cure resin cements could achieve high degree of cure when light-cured. In addition, the microhardness of the resin cements evaluated did not decrease when kept in water.
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Hideki TAMASAKI, Taiji SOHMURA, Fumio TERAOKA, Takehiro YAMAMOTO, Yous ...
2005 Volume 24 Issue 1 Pages
76-82
Published: 2005
Released on J-STAGE: February 24, 2010
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A simple and novel method —in the form of solution spraying— was developed to fabricate biodegradable, porous poly (L-lactic acid) (PLLA) particulates for scaffold. PLLA pellets were dissolved in an organic solvent. Then, 5% PLLA-dioxane solution was sprayed using an air-assisted atomizer with a nozzle diameter of 2.5mm at an air flow rate of 15L/min. After the sprayed solution solidified in liquid nitrogen, spherical particulates with median diameter of 225μm were obtained. Morphology of sprayed products could be altered by varying the fabrication conditions. When nozzle diameter was reduced to 1.5mm, sprayed products became fibrous. When the concentration of PLLA-dioxane solution was increased, the diameter of particulates increased too. On the other hand, when air flow rate was increased, the diameter of particulates decreased. Likewise, solidification conditions also affected the morphology of sprayed products, such that they were either thin film-like or in particulate form.
Based on the results of the present study, we concluded that PLLA particulates of varying morphologies could be obtained by adjusting the fabrication conditions.
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Linlin HAN, Akira OKAMOTO, Masayoshi FUKUSHIMA, Takashi OKIJI
2005 Volume 24 Issue 1 Pages
83-91
Published: 2005
Released on J-STAGE: February 24, 2010
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In this study, enamel micro-cracks produced around flowable composite restorations were observed using a stereomicroscope and a scanning confocal laser microscope (SCLM). The effects of polymerization shrinkage, mobility of composite and polishing period after filling on the incidence of marginal enamel micro-cracks were examined. Enamel micro cracks were observed on all of the composite restorations when the restoration was polished immediately after filling.
Enamel micro-cracks distributed approximately parallel to the cavity margin and located 0.01-0.3mm from the restored cavity margin. The occurrence of enamel micro-cracks was higher in conventional hybrid composite restorations than in flowable composites, and when polished 15 minutes after filling (as compared to 24 hours after filling).
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Sule KAVALOGLU CILDIR, Nuket SANDALLI
2005 Volume 24 Issue 1 Pages
92-97
Published: 2005
Released on J-STAGE: February 24, 2010
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The aim of this study was to investigate the fluoride release and fluoride recharge behaviors of two conventional glass-ionomer cements (GICs) and two polyacid-modified composite resins (PMCRs) after exposure to mouthwash and toothpaste. Fluoride released from the materials was measured at 1
st, 2
nd, 3
rd, 4
th, 7
th, 14
th, 21
st, and 28
th days. At 28
th day, the specimens were divided into three groups. Specimens in the control group were stored in deionized water. For the other two groups, the specimens were exposed to 0.05% NaF solution and fluoridated toothpaste for one month. After refluoridation, fluoride amount was measured at 30
th, 31
st, 32
nd, 36
th, 44
th, 52
nd, and 60
th days. All materials released fluoride. The highest amount of fluoride was obtained during the first 24 hours, and there was a statistically significant difference between the amounts of fluoride released from GICs and PMCRs (p<0.0001). After exposure to mouthwash and fluoridated toothpaste, all materials were recharged and continued releasing fluoride. While the amount of fluoride release from the materials increased after reflouridation, the increase was higher in GICs.
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Tijen PAMIR, Bilge Hakan SEN, Ali CELIK
2005 Volume 24 Issue 1 Pages
98-103
Published: 2005
Released on J-STAGE: February 24, 2010
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The aim of this study was to determine the fluoride-release and mechanical properties of a water-hardening glass-ionomer cement (GIC) (ChemFil Superior) when titanium tetrafluoride (TiF
4) was added. Three experimental groups were prepared with TiF
4 added to the liquid component of the material in concentrations of 0.5, 1, and 2%. The control group was the original form of the cement and free of TiF
4. After the specimens (4mm in diameter×6mm in length) were prepared, their compressive strength, microhardness, modulus of elasticity, and fluoride release were measured. Data were analyzed using one-way analysis of variance (ANOVA) and post-hoc test (Bonferroni/Dunn correction). The addition of TiF
4 into GIC significantly reduced fluoride release from the material with the exception of 1% TiF
4 (p<0.0083). Compressive strengths of 0.5 and 1% TiF
4-added GICs were higher than that of the original GIC, but it was not statistically significant (p>0.05). The differences among modulus of elasticity values of experimental and control groups were not significant (p>0.05). Similarly, microhardness of GIC was not affected with TiF
4 addition (p>0.05).
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Masayuki KON, Luciana M. HIRAKATA, Youji MIYAMOTO, Hidemitsu KASAHARA, ...
2005 Volume 24 Issue 1 Pages
104-110
Published: 2005
Released on J-STAGE: February 24, 2010
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The purpose of this study was to investigate how aragonite (calcium carbonate) whiskers influenced the strengthening and carbonating of α-tricalcium phosphate (α-TCP) based calcium phosphate cement. Aragonite whiskers of 0.95μm width with an aspect ratio of 6.6 were prepared. The cement powder, α-TCP containing 0-50 mass% aragonite whisker, was mixed with 0.6 mol/L NaH
2PO
4 solution and incubated at 37°C and 100% relative humidity. Diametral tensile strength (DTS) value increased significantly when appropriate amount of aragonaite whiskers was added. For example, DTS value of set cement containing 20 mass% aragonite whisker was 5.8±0.5 MPa, whereas DTS value of set cement containing no whiskers was 1.3±0.2MPa after 1-week incubation. SEM observation revealed that the shape of the whiskers and the densification of the structure could have contributed to the strengthening of the set cement. Moreover, FTIR spectra implied that a bone-like carbonated apatite was precipitated in the cement. The results obtained in the present study revealed that the shape as well as any slight dissolution of aragonite whiskers could contribute to improving the properties of α-TCP based calcium phosphate cement.
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Megumi FUJITA, Susumu KAWAKAMI, Hisanori KOMATSU, Hidehiko SANO
2005 Volume 24 Issue 1 Pages
111-116
Published: 2005
Released on J-STAGE: February 24, 2010
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The purpose of this study was to evaluate the translucency and color change of simulated heavily discolored teeth using polymer-based dental tooth coating materials and flowable resin composites. Five shades of coating material and two shades of flowable resin composite were used. Colorimetric values of the materials in different shades were determined using the L
*a
*b
* system of the Commission Internationale de l'Eclairage (CIE). Colorimetric examination was performed on white, black, and shade guide (C4) backgrounds using specimens of various thickness (0.2, 0.3, 0.5, 1.0, and 2.0mm).
New coating material showed less translucent than flowable resin composites. Moreover the new material showed the potential to improve the appearance of heavily discolored teeth when being applied as a thin first layer.
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Satomi KOSAKA, Hirotada KAJIHARA, Hisanori KURASHIGE, Takuo TANAKA
2005 Volume 24 Issue 1 Pages
117-122
Published: 2005
Released on J-STAGE: February 24, 2010
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The purpose of this study was to evaluate the effectiveness of resin coating as a means of preventing marginal leakage beneath full cast crowns which were emplaced using different cements. Standard full cast crown preparation was made on 64 extracted premolars. These samples were then divided into four groups, with half of each group coated with dentin coating material after preparation. Crowns were cemented onto the teeth using zinc cement, Fuji I, Vitremer, or C & B Metabond. The samples were thermal-cycled for 10, 000 cycles. They were then immersed in erythrosine solution, sectioned, and observed under a microscope. Microleakage analyses were performed using a 0-4 point system. The data were statistically analyzed. There were significant differences between the coated specimens and the uncoated specimens using Fuji I and Vitremer.
The results showed that a resin coating could decrease the amount of marginal leakage when applied with these two cements.
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Sachiko TOMITA, Akiyoshi SHIN-YA, Harunori GOMI, Tetsuji MATSUDA, Shin ...
2005 Volume 24 Issue 1 Pages
123-133
Published: 2005
Released on J-STAGE: February 24, 2010
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The purpose of this study was to investigate the effect of repeated machining up to 51 times using the same diamond bur on machining accuracy of inner and outer surfaces of CAD/CAM (computer-aided designing and computer-aided manufacturing) machined ceramic crowns. The surface topography of machined crowns was examined using photographs. It was found that machining accuracy was not affected by the number of machining times. In all measuring points, the inner surface was machined to a dimension larger than the die model (
i. e., increased gap), whereas the outer surface was machined to a dimension smaller than the crown model (
i. e., smaller crown). Photo observation showed that cervical contour was machined in a clear, rounded form from 1
st to 11
th crowns.
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Atsushi YARA, Hideo OGURA, Akiyoshi SHINYA, Shoko TOMITA, Takashi MIYA ...
2005 Volume 24 Issue 1 Pages
134-139
Published: 2005
Released on J-STAGE: February 24, 2010
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The diamond burs of two dental CAD/CAM systems (GN and CD) were examined if they could be used to fabricate up to 21 ceramic full crowns without fracture. After one, 11, and 21 machining times, the surfaces of the diamond burs were observed and the number of particles captured on SEM pictures was counted. The average surface roughness of the crowns was also measured. All diamond burs could be used to fabricate 21 ceramic crowns without fracture. A significant decrease in the number of diamond particles was found on the surfaces of GN burs after 11 and 21 machining times, but not on those of CD burs. The average surface roughness of GN crowns significantly increased with increase in the number of machining times. A significant positive correlation was found between the average surface roughness and the number of diamond particles.
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Part III Alloys for Metal-bond Porcelain
Sakae NAGASAWA, Takamitsu YOSHIDA, Nobuyoshi TERASHIMA, Toshihide MIZO ...
2005 Volume 24 Issue 1 Pages
140-148
Published: 2005
Released on J-STAGE: February 24, 2010
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The thermal expansion rate, coefficient of thermal expansion, and high temperature strength of two types of commercially available alloy for metal-bond porcelain, KIK-HII (KIK) and Degubond-J2 (J2), were evaluated up to the liquidus point temperature using a thermo-mechanical analyzer. Furthermore, microstructure in the solid-liquid coexisting region was observed for evaluation.
Our results revealed the following findings:
1. For KIK, solidus point was 1, 209.3±3.2°C, liquidus point was 1, 308.3±7.1°C, and melting expansion rate was 0.41±0.16%.
2. For J2, solidus point was 1, 198.3±0.6°C, liquidus point was 1, 253.0±4.4°C, and melting expansion rate was 4.50±0.80%.
3. At high temperature, the mechanical characteristics of KIK greatly differed from those of J2. The risk of causing deformation during porcelain baking was suggested for KIK. Removal of segregation during casting was considered difficult in J2.
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