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Yasuko MOMOI, Kunitsugu HIROSAKI, Atsushi KOHNO, John F. MCCABE
1995 Volume 14 Issue 2 Pages
109-119,275
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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The mechanical properties of resin-modified “hybrid” glass-ionomers, for both restorative and liner/base applications, were assessed by a flexural test and compared with those of conventional acid-base glassionomers. Flexural strength, flexural modulus, and the modulus of resilience were determined 30 minutes after mixing, and at 24 hours and 3 months after aging in distilled water at 37°C. With a microscope and SEM observations, a comparison of marginal breakdown was made between a resin-modified and a conventional glass-ionomer restoration in bovine cavities, after cyclic loading with steel balls. It was found that resin-modified glass-ionomers were stronger, more flexible, and more resilient than conventional acid-base glass-ionomers. This was in accord with the finding that less marginal breakdown and surface deterioration occurred in a resin-modified glass-ionomer than in a conventional analogue. For some materials the flexural properties progressively improved between 24 hours and 3 months, while others showed no improvement or even deteriorated.
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Takeyoshi SHIMIZU, Tadanori KITANO, Masayoshi INOUE, Koichi NARIKAWA, ...
1995 Volume 14 Issue 2 Pages
120-134,275
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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Using modified USPHS criteria, we evaluated annually for ten years 91 cases restored with visible light cured posterior composite resin LFP (Base resin: UDMA; filler: micro crushed type, alumino-silicate, barium glass and silica, 85wt%, 74vol%). The 91 cases restored with LFP decreased to 68 in ten years. Of the 23 cases that were lost, one resulted from a pulpal reaction immediately following restoration, four were extracted owing to periodontal disease or extrusion of third molars, two became abutments owing to loss of an adjacent tooth, eight had recurrent caries, and eight were lost owing to caries on a surface having no relationship to the composite resin restoration. Because we observed comparatively little wear, good marginal adaptability, and no discoloration, we concluded that the ten-year clinical success of LFP was on the whole very good, and that this resin has adequate clinical merit as a restorative material for posterior teeth when restricted to restorations covering comparatively small areas.
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Kozo UMEMOTO, Shigeaki KURATA
1995 Volume 14 Issue 2 Pages
135-142,275
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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Mixed silanes, 3-methacryloxypropylsilyltriisocyanate and 3-mercaptopropyltrimethoxysilane, were used as primers for adhesion of poly (methyl methacrylate) to porcelain teeth, precious alloys and nonprecious alloys. After thermocycle testing, the mean bond strengths of the resin to porcelain, silver alloys and stainless steel were excellent. The fracture patterns of porcelain teeth after thermocycling followed by adherent testing were similar to those of specimens subjected to 48-hour water immersion at 37°C. Two specimens failed cohesively in the porcelain and the other specimens failed in the resin. The mixed primer had no effect on cobalt-chromium alloy specimens.
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Chatcharee SUCHATLAMPONG, Shin-ichi GOTO, Hideo OGURA
1995 Volume 14 Issue 2 Pages
143-151,276
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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The compressive strength of five different amalgams was measured at one hour, six hours, 24 hours, and seven days, and X-ray diffraction analysis was carried out for each amalgam at the same times in order to investigate the early strength characteristics of the amalgams in relation to the formation of different phases. At 24 hours all tested amalgams reached about 90% or more of their seven-day compressive strength, but the increase in the early compressive strength from one hour to 24 hours varied between different amalgams. Two of the five amalgams tested reached about 90% of their seven-day compressive strength at six hours. A significant correlation was found between the ratio of early compressive strength to seven-day compressive strength, and the X-ray diffraction intensity ratio (ratios of one-, six- and 24-hour intensity to sevenday intensity) for the γ
1 phase, indicating that the increases in early compressive strength are mainly dependent upon the formation of γ
1.
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Kunio WAKASA, Masao YAMAKI, Akira MATSUI
1995 Volume 14 Issue 2 Pages
152-165,276
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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Average stress during shear bond testing, and deformation behaviour during nano-indentation testing were calculated for the bonding area as a bonding site for copolymerization with resin composite in dentine bonding systems. First, average stress was calculated in the bonding area between bovine dentine and composite resin. Secondly, the plastic deformation zone size was calculated using an elastic/plastic deformation zone model after a nano-indentation test. The result clearly showed that average stress depended upon the elasticity of the bonding area, the elasticity value ratio of the composite resin-to-bonding area, and interfacial stress between the dentine and the adhesive resin. In this bonding area, the elasticity/hardness ratio changed depending on the thickness of the bonding area as well as the plastic deformation zone size (b), expressed as a (b/2a)-value (indented triangular length (2a) at nano-indentation test) expanded with increasing the elasticity value.
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Junko HAYASHIZAKI, Seiji BAN, Norihiro ARIMOTO, Norio KATO, Yoshihiro ...
1995 Volume 14 Issue 2 Pages
166-174,277
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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This study investigated the effects of preparation conditions on the crystal phase of the fired fiber prepared with sodium alginate. Hydroxyapatite, Ca
10(PO
4)
6(OH)
2, hereafter referred to as HA, was only formed in fiber fired at 900°C under proper conditions. There was no significant difference in the crystal phase of the fired fibers prepared using different sodium alginate concentrations and syringe nozzle diameter, although fiber diameters were enlarged with increasing in either. No effects of phosphate type on the crystal phase of the fired fiber were found, but the aging time and the rinsing time had great effects. Sodium calcium phosphate, NaCaPO
4, and HA were formed when the aging time was shorter than 5min. Chlorapatite, Ca
5Cl(PO
4)
3, and HA were formed when the rinsing time was shorter than 3sec, and HA was formed when the rinsing time was 5min to 1 hour, whereas β-TCP, β-Ca
3(PO
4)
2, and HA were formed when the rinsing time exceeded 2 weeks.
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Masashi YAMAMOTO, Hidekazu TAKAHASHI
1995 Volume 14 Issue 2 Pages
175-184,277
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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The fatigue property of the composite resin has recently been a subject of research. In this study, the fatigue strength and the tensile strength of composite resins stored in water were investigated. Two types of light cure composite resins were used: a Hybrid type and an MFR type. Dumbbell-shaped specimens were prepared. After storage at 37±0.5°C for 24 hours, 1 month, 3 months, 6 months and 12 months, the fatigue test and the direct tensile test were performed. The staircase method was employed to analyze the fatigue strength under a 10
5 cyclic load. The fatigue strength of the Hybrid type at 24h ours was 54.7MPa; that of the MFR type was 28.1MPa. Both fatigue strengths decreased during water storage. Otherwise, the tensile strength of the Hybrid type was 77.0MPa; that of the MFR type was 53.5MPa. After 12 months of storage, the tensile strength of the Hybrid type remained unchanged during water storage; however, that of the MFR type decreased.
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(Part 1) Molecular Structure and Biological Activity of a Modified NiTi Alloy Surface
Kazuhiko ENDO
1995 Volume 14 Issue 2 Pages
185-198,277
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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Human plasma fibronectin (pFN), an adhesive protein, was covalently immobilized onto an alkylaminosilane derivative of a NiTi substrate with glutaraldehyde through Schiff's base formation. The surface at different stages of the modification was characterized by X-ray photoelectron spectroscopy (XPS), and the amount of immobilized pFN was determined by a fluorometric method. The spreading behavior of human gingival fibroblasts was examined on the modified surface. The XPS spectra suggested that γ-aminopropyltriethoxysilane (γ-APS) was bonded to the surface through metallosiloxane bonds (Ti-O-Si) formed via a condensation reaction between the silanol end of γ-APS and the surface hydroxyl group, with a highly cross-linked siloxane network formed after heat treatment of the silanized surface at 100°C. The pFN was immobilized at the surface density of 1.1μg⋅cm
-2, and significantly promoted fibroblast spreading, suggesting that this chemical modification offers an effective means of controlling metal/cell interactions. These results may contribute to the development of bioactive metallic implants.
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(Part 2) Corrosion Resistance of a Chemically Modified NiTi Alloy
Kazuhiko ENDO
1995 Volume 14 Issue 2 Pages
199-210,278
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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The corrosion resistance of a NiTi alloy, chemically modified with a human plasma fibronectin (pFN) using an aminosilane and a glutaraldehyde, was examined by electrochemical techniques in a 0.9% NaCl solution and a cell culture medium containing serum. The role of serum proteins in influencing the passive behavior of the alloy was extensively studied by anodic polarization and X-ray photoelectron spectroscopy (XPS). The passive current density increased in the presence of serum proteins. The enhanced dissolution of the passive film appears to be a consequence of quick adsorption of the serum proteins and the subsequent formation of metal ion-protein complexes on the film surface. With the chemical modification, the corrosion rate was reduced by approximately 50% in both solutions due to a highly cross-linked siloxane network formed on the alloy surface. This network layer limited the diffusion of dissolved oxygen, metal ions, and biological molecules involved in the corrosion reactions.
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Keiji KAWAI, Karl F. LEINFELDER
1995 Volume 14 Issue 2 Pages
211-220,278
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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Inappropriate bonding treatment tends to result in marginal fractures or microleakage caused by masticatory loading. The purpose of this study was to investigate the effect of adhesion of resin composites on marginal degradation. Five posterior resin composites were inserted into Class I preparations with and without etching or bonding treatment. These restored teeth were subjected to a three-body wear test for 400, 000 cycles, and the exposed enamel height at the tooth/restoration interface was determined by profilometer and scanning electron micrography (SEM). It was found that use of appropriate etching and bonding agents reduced the exposed enamel height and maintained marginal integrity after repeated loading.
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Akiko SUZUKI, Yohji IMAI
1995 Volume 14 Issue 2 Pages
221-229,279
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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The effectiveness of a barbituric acid/copper (II) chloride initiator system in dentin bonding was examined in terms of the effects of barbituric acid structures and dentin conditioners on bond strength. Curing times and tensile bond strengths to bovine dentin were measured for PMMA/MMA resins in conjunction with initiators consisting of a combination of CuCl
2 and four barbituric acids having different substituents. The dentin surfaces were treated with six conditioners consisting of 10% citric acid or phosphoric acid with or without 3% FeCl
3 and CuCl
2. Among the four barbituric acid systems studied, curing times varied significantly (p<0.002), but the bond strengths to dentin, conditioned with 10% citric acid containing 3% CuCl
2, did not (p>0.60). The dentin conditioners influenced bond strength significantly (p<0.02). The phosphoric acid based conditioners produced higher bond strengths than those based on citric acid. The bond strengths obtained under optimal conditions were comparable to those reported for MMA-TBB resin. Thus, the resin applied using the barbituric acid/CuCl
2 system worked as well as one of the most effective bonding resins available.
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Mir Ayubur RAHMAN, Chihiro TANI, Kazuo ITOH, Sadao WAKUMOTO, Hisashi H ...
1995 Volume 14 Issue 2 Pages
230-235,279
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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The optimum concentration and application time for an experimental dentin primer composed of an aqueous solution of 1, 6-hexanediol were determined by measuring the wall-to-wall polymerization contraction gap width of a commercial light-activated resin composite in a cylindrical dentin cavity prepared in an extracted human molar. Contraction gap formation was completely prevented only when the dentin cavity wall was primed with 45wt% 1, 6-hexanediol for 60s. There were no significant differences in tensile bond strength among primers composed of 20.0-57.5wt% 1, 6-hexanediol. These results suggest that the optimum concentration and application time are 45wt% and 60s, respectively.
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Masafumi KIKUCHI, Kazuo TAKAKUDA, Hiroo MIYAIRI, Osamu OKUNO
1995 Volume 14 Issue 2 Pages
236-244,279
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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To examine a new concept for computerized production of dental prostheses, an experimental porcelain forming system was devised. Unlike other dental CAM systems, the system is intended to form porcelain much as human technicians do. The system builds up an object by alternately applying water and droplets of porcelain powder. Test specimens were made by forming porcelain powder into square plates under different forming conditions. Surface characteristics and shapes of formed porcelain were found to be affected by conditions such as quantity of water, forming area and forming thickness. The proper quantity of water for forming was influenced by evaporation. It was concluded that investigation into feedback control of the water supply in response to varying forming conditions is required.
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Tadashi ONIZUKA, Noriko KAMIMURA, Hirotada KAJIWARA, Atsuo NAKASHIMA, ...
1995 Volume 14 Issue 2 Pages
245-255,280
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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The influence of boiling water treatment on the surface roughness and surface microstructure of set gypsums was investigated. Typical surfaces before and after immersion in boiling water were compared by means of SEM observation, the Knoop hardness test, and a surface roughness test. The surfaces of set gypsums were rougher than that of an acrylic resin plate, and after immersion in boiling water, highly roughened surfaces and thinner crystal bodies were observed on each specimen under SEM. The knoop hardness of set gypsums was considerably lowered after boiling water immersion. That of die stones was the same or lower than set dental stones. The results showed that even brief immersion in boiling water had profound effects on the dental stone cast, resulting in rougher surfaces and lower hardnesses of set gypsums.
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Mold Temperature and Spruing Factors
Yvonne VIDOVIC, Hyun-Gon P CHUNG, Toshiko MORI
1995 Volume 14 Issue 2 Pages
256-262,280
Published: December 25, 1995
Released on J-STAGE: February 12, 2009
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This study evaluated the sensitivity of an experimental model to mold temperature using a two-chamber casting machine and its recommended investment (Exp.1), and the effect of sprue diameter and length using a one-chamber casting machine and its recommended investment (Exp.2). Experimental patterns were cast from commercially pure titanium and percentage casting success obtained. Mold temperatures of 620, 350 and less than 100°C, and sprues, 4 or 6mm diameter and 5, 20 or 26mm long, were used. The effect on casting success of a “non-system” investment was also evaluated in both experiments. The experimental model did not discriminate the two lower mold temperatures (Exp.1). Casting success was significantly lower with a 4mm sprue diameter but was not affected by sprue length (Exp.2). The results suggest the importance of the combination of casting machine, investment type and mold dimension.
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