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Masaru GUNJIMA, Iwan TOFANI, Yukimi KOJIMA, Kenshi MAKI, Mitsutaka KIM ...
2004 Volume 23 Issue 2 Pages
67-74
Published: 2004
Released on J-STAGE: February 12, 2009
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Grape seed proanthocyanidins extract (GSPE), whose principal ingredient is proanthocyanidins, shows many activities such as cholesterol lowering effects, antioxidant effects, anti-tumor effects, cardioprotective effects, and protection against ultraviolet rays. However, reports of the effects of GSPE on bone are rare. We performed a mechanical analysis of the effect of GSPE on the interior structure of rat mandibular bone in the growth period, using three-dimensional peripheral quantitative computed tomography (pQCT). A low-calcium/high-calcium diet with supplementary GSPE was compared to a lowcalcium/high-calcium diet in rats with debilitated mandibular bones. The group who received added GSPE showed a significant increase in cortical bone density, cross-sectional area, and trabecular bone mineral content (p<0.05). A significant increase was also seen in the results of a non-invasive stress strain index (SSI) (p<0.01) in the added GSPE. Our findings suggest that GSPE can increase bone quality and bone strength of rat mandibles in the growth period.
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A Finite Element Analysis
Kunihiko KOBAYASHI, Takumi YORIMOTO, Kazuhiro HIKITA, Takeo MAIDA
2004 Volume 23 Issue 2 Pages
75-80
Published: 2004
Released on J-STAGE: February 12, 2009
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This study evaluated experimental abutment forms utilizing adhesion for clinical treatment by the three-dimensional finite element method. Three experimental abutment forms with no axial wall were evaluated: Form 1 was the occlusal surface reduced by 1.5mm, Forms 2 and 3 were the crown cut perpendicular to the tooth axis 2mm or 4mm from the central groove. The restorations were made of 3 types of materials: composite resin, porcelain, and a gold-based alloy. Restorations were bonded to the abutments with an adhesive resin. A vertical load of 500N was applied to the center of the inner incline of the buccal cusp. The stresses in the adhesives were largest in Form 1 with composite resin and in Form 3. It was indicated that the stresses were greatly affected by the form of the abutment and the restorative materials.
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Part II ADAS Type 3 Gold Alloy
Sakae NAGASAWA, Takamitsu YOSHIDA, Nobuyoshi TERASHIMA, Toshihide MIZO ...
2004 Volume 23 Issue 2 Pages
81-88
Published: 2004
Released on J-STAGE: February 12, 2009
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Previously, high temperature properties of the silver-palladium-copper-gold alloy were investigated. In this study, the thermal expansion percentage and coefficient, and high temperature strengths of ADAS Type 3 gold alloy were investigated up to the liquidus temperature. Furthermore, microstructural and compositional changes in the solid/liquid dual phase were studied. The following conclusions were obtained. (1) The solidus point of the Type 3 gold alloy was 899.3±11.7°C, and the liquidus point was 962.3±2.4°C. (2) The thermal expansion percentage at the solidus point was 1.636±0.046%, while it was 4.853±0.213% for the liquidus point. The thermal expansion percentage of the melt was 3.217±0.257%. (3) The melt expansion was observed even under the measuring pressure of 373.75HPa, which was quite different from the fact that the melt expansion disappeared at the pressure of 20.87HPa for the silver-palladium-copper-gold alloy. (4) The morphology of solid phase in the solid/liquid dual zone of this alloy was quite different from those observed with the silver-palladium-copper-gold alloy.
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Masahiro OHSAWA, Hiroaki YOKOTA, Yoshihiko HAYASHI
2004 Volume 23 Issue 2 Pages
89-93
Published: 2004
Released on J-STAGE: February 12, 2009
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The bond durability of resin cements to a 12% Au-Pd-Ag alloy was studied through cyclic impact tests with different loads. A piece of casting alloy was bonded to a cast block with two types of resin cements, Super Bond C&B and Bistite II. A shear load was applied onto a small piece of alloy until debonding of the specimen, using different weights of plungers, 130g, 230g, 330g and 430g.
The specimen bonded with Super Bond exhibited a higher resistance than that with Bistite II. The fracture modes of the debonded cements were completely different from each other. That is, Bistite II showed a bulk fracture of cement by the crack penetrating through the cement layer. On the other hand, Super Bond showed damages limited to the surface and no bulk fracture. The mode of fracture was dependent not on the loading weight but the types of resin cements used.
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Guang HONG, Hiroshi MURATA, Taizo HAMADA
2004 Volume 23 Issue 2 Pages
94-99
Published: 2004
Released on J-STAGE: February 12, 2009
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The purpose of this study was to determine the influence of plasticizer content on the tensile bond strength of heat-cured acrylic soft denture liners to a denture base resin. Differences among materials were significant, except for 100wt% Dibutyl Sebacate (DBS) and 80wt% DBS of tensile bond strength. The bond strength of all materials to the denture base increased with an increase in thermal cycles significantly except for 40wt% DBS. The tensile bond strength of soft denture liners to the denture base resin significantly decreased with an increase of plasticizer contents. Differences were found among the difference plasticizer contents in failure types between the denture base resin and soft denture liners. The results suggest that the tensile bond strengths of heat-cured acrylic soft denture liners to the denture base resin were lower with an increase in plasticizer content.
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Effect of Conditioner with Ascorbic Acid/Ferric Chloride
Kohyoh SOENO, Yohsuke TAIRA, Hideo MATSUMURA, Mitsuru ATSUTA, Shiro SU ...
2004 Volume 23 Issue 2 Pages
100-105
Published: 2004
Released on J-STAGE: February 12, 2009
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The purpose of this study was to evaluate ascorbic acid (AS) and ferric chloride (FE) for bonding 4-META/MMA-TBB resin to dentin that had been treated with NaClO. An experimental dentin conditioner consisting of 10%AS and 5%Fe (10AS-5FE) and three controls (10AS-0FE, 0AS-5FE, and 0AS-0FE) were prepared. Ascorcic acid neutralizes NaClO. The flattened dentin surfaces were modified sequentially with phosphoric acid etchant, NaClO agent, and the experimental conditioner, then each surface was bonded to a stainless steel rod with 4-META/MMA-TBB resin. The Super-Bond C&B (10-3/SB) system was also used. 24-hour tensile bond strengths were determined. The bonding system using 10AS-5FE conditioner showed significantly high bond strength compared to 10AS-0FE, 0AS-5FE, and 0AS-0FE. No significant differences were observed between 10AS-5FE and 10-3/SB. Microphotographs suggested that no hybrid layer formed in the 10AS-5FE group. Although the use of phosphoric acid and NaClO resulted in decreased bond strength between 4-META/MMA-TBB resin and dentin, additional conditioning with ascorbic acid and ferric chloride improved the bond strength.
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Seiichiro FUJISAWA, Toshiko ATSUMI
2004 Volume 23 Issue 2 Pages
106-108
Published: 2004
Released on J-STAGE: February 12, 2009
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This study was designed to investigate the cytotoxicity of MMA (methyl methacrylate) and 4-META (4-methacryloyloxyethoxycarbonylphthalic anhydride)/MMA with or without TBBO (tri-
n-butylborane partially oxide), an initiator and TBBO alone against human pulp fibroblasts (HPF).
Cell viabilities were measured by MTT assay. The cytotoxicity of 4-META/MMA-TBBO was comparable with that of MMA-TBBO. TBBO showed higher cytotoxicity than 4-META/MMA. The cytotoxicity induction of a 4-META/MMATBBO resin may be preferably associated with TBBO.
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Masatoshi TAKAHASHI, Masafumi KIKUCHI, Yukyo TAKADA, Osamu OKUNO, Toru ...
2004 Volume 23 Issue 2 Pages
109-116
Published: 2004
Released on J-STAGE: February 12, 2009
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Anodic polarization was performed in 0.9% NaCl and 1% lactic acid solutions to characterize the relationship between the corrosion behavior and microstructures of cast Ti-Au (5-40%) alloys. An abrupt increase in the current density occurred at approximately 0.6V vs. SCE for the 30% and 40% Au alloys in the 0.9% NaCl solution. The microstructures after corrosion testing indicated that this breakdown may have been caused by the preferential dissolution of the Ti
3Au. However, the potential for preferential dissolution was higher than the breakdown potential of stainless steel or Co-Cr alloy, which meant that the corrosion resistance of the Ti-Au alloys was superior. In 1% lactic acid solution, the corrosion resistance of the Ti-Au alloys was excellent, with no breakdown at any composition. In the present test solutions, the Ti-Au alloys up to 20% Au had good corrosion resistance comparable to that for pure titanium.
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Yusuf Ziya BAYINDIR, Funda BAYINDIR, M. Samil AKYIL
2004 Volume 23 Issue 2 Pages
117-120
Published: 2004
Released on J-STAGE: February 12, 2009
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The purpose of this laboratory investigation was to evaluate the bond strength of permanent cement (Duo-cement Kit, Meron, Durelon) to commonly used core build-up materials (President, Dyract AP, Ionofil, Vitremer).
Sixty specimens (five of each product) were fabricated as a canine core build- up. Full crown castings were made to fit each core specimen. Full crown castings were cemented to core samples and stored at 37°C and 100% humidity for 10 days. After storage, the bond strength was measured with a Haunsfield tensometer in tensile mode at a crosshead speed of 5mm/min.
Statistical evaluation was performed with univariate analysis of variance (P<0.001). The cement types affected the bond strength of full crown castings to core materials (F: 14.80; P<0.001). The interaction between the cement and core materials was significant (F: 3.69; P<0.01). According to the Duncan's test it was found that the values of Duo-cement were statistically different from the other cements.
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Taiji SOHMURA, Kazumichi WAKABAYASHI, Rungnapa LOWMUNKONG, Hirokazu HO ...
2004 Volume 23 Issue 2 Pages
121-128
Published: 2004
Released on J-STAGE: February 12, 2009
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Three-dimensional (3D) digitizing and computerization of dental casts is a trend in dentistry especially for orthodontics to substitute stone casts. Generally used laser scanners have a blind side in the measurement of undercuts. As alternative equipment that can digitize regardless of the undercut, the potential of recent multi-slice medical CT was examined. In 3D shape reconstruction, the CT window level affects the size of the object. It was examined, and a CT window level of 800 was found to be suitable. However, the size became slightly smaller than the real object. Then, a correction ratio of 1.002, 1.015 and 1.013 on the X-, Y- and Z-axis was given, and error within 0.08% was accomplished. The measurement and 3D imaging of dental casts was completed within 10min. The reproducibility of the complicated morphology of dental casts was slightly inferior to that of the latest laser scanners, but the accuracy and operationality regardless of the undercut is noteworthy for clinical application.
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Part 3. Effect of Reducing Agent Addition on the Strength and Expansion of the Investments
Yukun MENG, Akira NAKAI, Hideo OGURA
2004 Volume 23 Issue 2 Pages
129-135
Published: 2004
Released on J-STAGE: February 12, 2009
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Different reducing agents (B, Al, Si and Ti) were individually added to two gypsum-bonded investments to prepare investments preventing surface blackening of some noble cast alloys. The effect of different additive contents on green-body and burnout compressive strength, setting and thermal expansion of the investments were evaluated. The strength and expansion of the investments were changed by the additives. The compressive strength of Al-, Si- and Ti-added investments decreased with the increase of additive contents. The burnout strength of B-added investments significantly increased while green-body strength remained unchanged. The setting expansion of the B-added investments increased while those of the Al-, Si- and Ti-added investments decreased with the increase of additive contents. The thermal expansion of the Si- and Ti-added investments decreased, and that of the Al- and B-added investments remained unchanged. Further study is necessary to evaluate the effects of these additives on the accuracy of dental castings.
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Sakae NAGASAWA, Takamitsu YOSHIDA, Toshihide MIZOGUCHI, Nobuyoshi TERA ...
2004 Volume 23 Issue 2 Pages
136-145
Published: 2004
Released on J-STAGE: February 12, 2009
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This study evaluates effects of repeated baking processes on the mechanical and physical properties of single and triple applications of opaque, body and enamel porcelains fused to three different metal substrates (precious metal, semi-precious metal and non-precious metal). The vintage halo porcelain system was employed and fused to metals. Fused samples were subjected to three-point bend tests to evaluate bend strength and modulus of elasticity.
It was found that, by increasing repeated baking cycles, (1) body and enamel porcelains increased bend strengths but opaque porcelain did not show any changes, (2) all triple-layered porcelains fired to metals increased bend strengths, and (3) all three porcelains and metal substrates did not exhibit changes in thermal expansion percentage.
It was concluded that repeating baking procedures up to 10 cycles did not exhibit any adverse effects on the final properties of porcelain-fired to metals, rather it was noticed that mechanical strengths increased by increasing cycles.
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Rosalina TJANDRAWINATA, Masao IRIE, Yasuhiro YOSHIDA, Kazuomi SUZUKI
2004 Volume 23 Issue 2 Pages
146-154
Published: 2004
Released on J-STAGE: February 12, 2009
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This study investigated the effects of spherical silica fillers on the physical and mechanical properties of resin-modified glassionomer cement (RMGIC). Specimens were fabricated by mixing untreated (UF) or silanized (SF) spherical silica filler into the powder of a commercially prepared RMGIC. The original RMGIC and a preparation containing 20wt% spherical silica filler were also examined with regard to their fractured surface and fluoride release. The fillers increased the compressive strength remarkably: up to 17% in the case of SF and 9% in the case of UF. Both UF and SF increased the flexural strength by up to 17%. The addition of SF increased the DTS up to 38%, but UF decreased the DTS. The addition of SF improved the workability and the mechanical properties of the RMGIC.
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Hiroyuki ARIKAWA, Takahito KANIE, Koichi FUJII, Seiji BAN, Tetsuya HOM ...
2004 Volume 23 Issue 2 Pages
155-160
Published: 2004
Released on J-STAGE: February 12, 2009
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The purpose of this study was to examine the optical and color stabilities of the paint-on resin used for shade modification of restorative resins. Three shades of paint-on resin and two crown and bridge resins were used. The light transmittance characteristics of the materials during accelerated aging tests such as water immersion, toothbrush abrasion, ultraviolet (UV) light irradiation, and staining tests were measured. Discolorations of materials resulting from tests were also determined. There were no significant effects of water immersion, toothbrush abrasion and UV light irradiation on the light transmittance and visible color change of paint-on resins, whereas the staining tests significantly decreased the light transmittance and increased color change of the translucent shades of materials. Our results indicate that the paint-on resins exhibit stable optical properties and color appearance, which are at least as good as the crown and bridge resins.
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Tae-Yub KWON, Yohji IMAI
2004 Volume 23 Issue 2 Pages
161-165
Published: 2004
Released on J-STAGE: February 12, 2009
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Polymerization characteristics of 4 types of ethyl methacrylate (EMA)-based resin, composed of EMA and EMA/methyl methacrylate (MMA) copolymers and initiated by tributylborane (TBB), were studied from the aspects of long term changes of residual monomer (RM) and molecular weight (Mw). The resins were polymerized at room temperature for 30min, stored at 37°C for 24hr, 1 and 4 weeks and then analyzed by high performance liquid chromatography and size exclusion chromatography to determine RM and Mw. RM decreased significantly from 4.47-1161% after 30min to 0.94-7.73%, 0.81-7.81%, and 0.78-7.10% after 24hr, 1 and 4 weeks, respectively, demonstrating a tendency to decrease with time for each resin. Mw showed a tendency to decrease from 427×10
3-551×10
3 after 30min to 354×10
3-530×10
3 after 4 weeks. TBB-initiated EMA resin had polymerization characteristics similar to those for TBB-initiated MMA resin in the temporal changes in RM and Mw during postpolymerization.
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Ji-Myung BAE, Kyoung-Nam KIM, Masayuki HATTORI, Koji HASEGAWA, Masao Y ...
2004 Volume 23 Issue 2 Pages
166-174
Published: 2004
Released on J-STAGE: February 12, 2009
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The aim of this study was to evaluate the dynamic fatigue strengths at 10
5 cycles and the strains of particulate filler composite resins with and without reinforcing fibers. An UHMWPE (Ribbond), a polyaromatic polyamide fiber (Fibreflex), and three glass fibers (GlasSpan, FibreKor, Vectris Frame) were used to reinforce the particulate filler composite resins. The fatigue properties were measured in three-point bending mode using a servohydraulic universal testing machine at a frequency of 5Hz, until failure occurred or 10
5 cycles had been completed. The fatigue strengths at 10
5 cycles were determined by the staircase method. The fractured aspects of specimens were evaluated by an optical and scanning electron microscope. The fatigue strengths of particulate filler composite resins were 49-57MPa, and those of fiber-reinforced were 90-209MPa. Unidirectional glass fibers showed higher reinforcing effects on the fatigue strengths of composite resins. The strain of UHMWPE-reinforced composite was largest.
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Mansuang ARKSORNNUKIT, Hidekazu TAKAHASHI, Norihiro NISHIYAMA, Prasit ...
2004 Volume 23 Issue 2 Pages
175-179
Published: 2004
Released on J-STAGE: February 12, 2009
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The objectives of this study were to evaluate the effect of heat application after silanation and the pH effect of silanated solution on flexural properties and hydrolytic durability of experimental composites. A spherical-shaped filler was silanated with 0.66 mass% of γ-MPTS in 70vol% ethanol solution. For the heating effect, the filler was heated after silanation for 3 hours at 50°C, 80°C and 110°C. For the effect of pH, ethanol solution with HCl solution of pH1, 2 and 4 were used. All fillers were mixed to make photopolymerized experimental composite resins. All specimens after immersion in 37°C water for 24 hours were additionally immersed in Soxhlet's extractor for another 1, 7 and 28 days. A three-point bending test was performed in 37°C water. The heat application of 50°C and 80°C increased flexural strength while heat of 110°C and pH showed no effects on flexural properties at p<0.05.
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Part 1 Masking Ability for Discolored Teeth
Mitsunobu OKAMURA, Ker-Kong CHEN, Hiroshi KAKIGAWA, Yoshio KOZONO
2004 Volume 23 Issue 2 Pages
180-183
Published: 2004
Released on J-STAGE: February 12, 2009
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A densely sintered high-purity alumina has been successfully utilized as a coping for all-ceramic crown. In order to apply the alumina coping to the porcelain laminate veneer restoration for the discolored teeth, the present study evaluated its masking ability when it was thinner than the proposed thickness for the crown. Colorimetric examination was performed on white and black backgrounds for the 0.7mm thick porcelain laminate veneer with 0.40 or 0.25mm thick alumina coping and 0.7mm thick porcelain without coping. With the presence of the coping, the porcelain appeared significantly lighter. Judging from the calculated color differences ΔE and the literature, it was suggested that the masking ability of the alumina coping would be sufficient with a 0.25mm thickness for the porcelain laminate veneer for heavily discolored teeth.
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Yoshiya HASHIMOTO, Akihiro UEDA, Masaaki NAKAMURA
2004 Volume 23 Issue 2 Pages
184-189
Published: 2004
Released on J-STAGE: February 12, 2009
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In the current studies, we examined the possibility of using HSP70 gene regulation as a cytocompatibility test for dental biomaterials. For this reason, we assessed the effects of three metal salts, HgCl
2, CuSO
4 and NiCl
2 on HSP70 gene expression in HeLa S3 cells using real-time Taqman quantitative PCR. Incubation of the cells for 4h in medium containing HgCl
2 (20 or 40μM), CuSO
4 (157, 313, 625 or 1250μM) or NiCl
2 (5000 and 10000μM) significantly induced HSP70 mRNA. The real-time Taqman quantitative PCR was able to detect HSP70 mRNA induction at 4-fold lower concentrations of HgCl
2 and 8-fold lower concentrations of CuSO
4 than the Neutral Red cell viability assay. These results indicate that real-time Taqman quantitative PCR, in combination with the monitoring of cell viability, may be a valuable tool for distinguishing between specific HSP70 mRNA induction and cytocompatibility of metals in dental biomaterials.
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Yasuhiro HOTTA, Takashi MIYAZAKI, Toshihisa FUJIWARA, Shoko TOMITA, Ak ...
2004 Volume 23 Issue 2 Pages
190-196
Published: 2004
Released on J-STAGE: February 12, 2009
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The purpose of this study was to evaluate the durability of tungsten carbide burs for the fabrication of titanium crowns using two dental CAD/CAM systems (DECSY, Digital Process, Japan and Cadim, Advance, Japan). A tungsten carbide bur in each system was examined and used without fracture to fabricate 51 titanium crowns. For both systems tiny chips were found on the bur blade at the 11th machining. These chips gradually enlarged as the number of machining times increased. At the first machining no significant difference in the average surface roughness was found on the crown between the two systems (1.6μm for DECSY and 1.2μm for Cadim). The cutting grooves became dull and the average surface roughness increased as the number of machining times increased. It is concluded that the tungsten carbide burs for both systems can be used to fabricate up to 51 titanium crowns.
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Yasuyuki YONEKURA, Kazuhiko ENDO, Masahiro IIJIMA, Hiroki OHNO, Itaru ...
2004 Volume 23 Issue 2 Pages
197-202
Published: 2004
Released on J-STAGE: February 12, 2009
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The corrosion characteristics of orthodontic alloy wires were investigated both in as-received and grinded conditions in 0.9% NaCl solution by atomic absorption spectrophotometry and potentiodynamic polarization measurements. The amount of each metal ion released from most alloys was larger for the grinded wires than for the as-received wires (p<0.01). The fact that the beta-Ti alloy wire (Ti-Mo-Zr) does not contain allergenic metals such as Ni, Co, and Cr, and the finding that resistance to both general and localized corrosion is the highest among the six wires investigated suggest that this wire is the most biocompatible orthodontic wire. Since a small amount of Ni, Cr or Co ions were released from Ni-Ti, Co-Cr and stainless steel wires, special attention should be paid during their clinical use for patients with allergic tendencies.
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Masatoshi TAKAHASHI, Masafumi KIKUCHI, Osamu OKUNO
2004 Volume 23 Issue 2 Pages
203-210
Published: 2004
Released on J-STAGE: February 12, 2009
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Experimental Ti-Au alloys (5, 10, 20 and 40 mass% Au) were made. Mechanical properties and grindability of the castings of the Ti-Au alloys were examined. As the concentration of gold increased to 20%, the yield strength and the tensile strength of the Ti-Au alloys became higher without markedly deteriorating their ductility. This higher strength can be explained by the solid-solution strengthening of the α titanium. The Ti-40% Au alloy became brittle because the intermetallic compound Ti
3Au precipitated intensively near the grain boundaries. There was no significant difference in the grinding rate and grinding ratio among all the Ti-Au alloys and the pure titanium at any speed.
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Hideki SATO, Masashi KOMATSU, Barbara MILLER, Hiroshi SHIMIZU, Hideki ...
2004 Volume 23 Issue 2 Pages
211-217
Published: 2004
Released on J-STAGE: February 12, 2009
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We examined the mold filling capacity and microhardness of two industrial 1% Fe titanium alloys: Super-TIX800
TM (Nippon Steel Corp.) (Fe: 0.910%, O: 0.370%, N: 0.005%) and Super-TIX800N
TM (Nippon Steel Corp.) (Fe: 0.960%, O: 0.300%, N: 0.041%). Two wedge-shaped acrylic patterns (with 30° or 15° angles) were prepared. Each alloy was cast in a centrifugal casting machine. Mold filling was evaluated as the missing length between the tip of the casting and the theoretical tip. Vickers hardness of the edge of the castings was also determined. For both angles tested, there were no significant differences (p>0.05) in mold filling among these alloys and the control (CP Ti). The results of testing the microhardness near the cast surfaces indicated that the hardened reaction layers on these alloys were thinner at the edge compared to CP Ti.
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Masahiro OHSAWA, Masahiro KAWAGUCHI, Yoshihiko HAYASHI
2004 Volume 23 Issue 2 Pages
218-222
Published: 2004
Released on J-STAGE: February 12, 2009
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Ring shaped wax patterns, having the same outside diameter and different inside diameters, were invested with a gypsumbonded cristobalite investment. The wax pattern was eliminated in an electric furnace at 120°C. A fusible alloy with a melting point of 47°C was cast at room temperature. The dimensional deviations between the fusible alloy casting and the wax pattern were calculated using the inside diameter, ring width and outside diameter. On the other series, a gold alloy casting of the same size was fabricated in the usual manner of the dental precise casting procedure, and the dimension was compared with that of the wax pattern.
In the comparison of 2 types of patterns, dimensional change by setting expansion was different. Dimensional change of the small inside diameter specimen differed at 3 portions measured, but that of the large inside diameter specimen was comparable at 3 portions. Concerning the resultant gold alloy casting, dimensional change at the outside diameter differed from each other, but those at ring width and inside diameter were comparable to each other. The difference in the inside diameter influenced dimensional change by setting expansion as well as that of the resultant casting.
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Effect of Water Absorption
Koichi FUJII, Hiroyuki ARIKAWA, Takahito KANIE, Seiji BAN
2004 Volume 23 Issue 2 Pages
223-229
Published: 2004
Released on J-STAGE: February 12, 2009
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In order to investigate the clinical application of paint-on resins, the effect of water absorption on toothbrush abrasion and light transmittance of ten crown resins including three paint-on resins was examined. Water absorption into each material ranged from 0.29 to 0.89mg/cm
2 after storage in distilled-water for 6 weeks and their hardnesses decreased by 3.5-22.3%. Maximum surface roughness (Rmax) of the materials stored in distilled water for 6 weeks increased with an increasing number of toothbrush abrasion cycles and ranged from 1.9 to 10.5μm after 100, 000 cycles. Also, Maximum depth and weight loss as an indicator of the amount of each material lost by abrasion showed similar behaviors similar to Rmax. These results indicated that the abrasion resistance of paint-on resins was located in the middle among all materials examined.
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(III) Composition of Investment for the Quick Casting Technique
Toshiko MORI, Farzaneh AGHAJANI
2004 Volume 23 Issue 2 Pages
230-232
Published: 2004
Released on J-STAGE: February 12, 2009
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A simultaneous differential thermal analysis and thermogravimetry method previously established was used to estimate the composition of gypsum-bonded investment marketed for the quick casting technique. Three commercial investments of this type were heated to 700°C at 10°C/min and the hemihydrate content was estimated by the mass decrease reached at 300°C after subtracting the mass decrease at 100°C as moisture content. The hemihydrate contents were between 25% and 30%, which appears to be the range also chosen for the conventional gypsum-bonded investment of cristobalite type over 70 years by the industry. However, the new type of investment contained both cristobalite and quartz. The small sample size is a disadvantage of the present method but this can be overcome by more frequent use of the method by investigators.
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Nuran DINÇKAL YANIKOGLU, Zeynep YESIL DUYMUS
2004 Volume 23 Issue 2 Pages
233-239
Published: 2004
Released on J-STAGE: February 12, 2009
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In this study, two acrylic based materials and three silicone rubber soft lining materials were investigated to determine the percentage of absorption and solubility in artificial saliva, distilled water, and denture cleanser. In addition, the effect of denture cleanser on surface properties of soft lining materials was also evaluated.
For sorption and solubility testing, 75 discs (50mm×0.5mm) were prepared and divided into 5 groups with 15 samples in each group. The specimens were stored in different solutions, and tested after 1, 4, and 16 weeks.
Analysis of variance was used to find the significant differences between the materials at all time intervals. The acrylic resin soft lining materials had higher solubility (3.432% Visco-gel in artificial saliva) and absorption (3.349% Visco-gel in distilled water) than Molloplast-B after 16 weeks of aging. The greatest hardness and color change were shown in the acrylic soft lining materials.
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