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Development and Research in the U.S.A.
Hiroshi NAKAJIMA, Toru OKABE
1996 Volume 15 Issue 2 Pages
77-90,249
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
JOURNAL
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Titanium has received a great deal of attention from dental researchers and clinicians. In the United States, the history of the application of titanium as a biomaterial started as early as 1940 when experiments with titanium implants were done using laboratory animals. It appears that in 1959, two American researchers were the first to suggest casting titanium to fabricate implant posts. The use of cast titanium for dental prostheses in the U.S. was first reported in 1977. The present survey revealed that during the last decade, the number of research projects on the applications of titanium to dentistry that were presented at annual IADR/AADR meetings has steadily increased. The majority of these presentations have been made by American researchers, and 59% of these were related to dental implantology. The numbers of reports on casting and prosthodontic applications have steadily increased, but they are still more limited. The purpose of this review was to provide information on the development and the current status of research on titanium in dentistry in the U.S.
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Susumu HIRANO, Hiromi YASUKAWA, Rie NOMOTO, Keisuke MORIYAMA, Tadashi ...
1996 Volume 15 Issue 2 Pages
91-97,249
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
JOURNAL
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SUS444 stainless steel filled chemically cured resin composites that can attract magnet were fabricated. The filler was treated with various concentrations of silane. The experimental composite was easy to handle and showed a good shelf life. The maximal properties obtained are as follows; The attraction force to a magnetic attachment was 1/3-1/4 lower than the commercially available magnet-keeper system for dental magnetic attachment. Flexural strength and Knoop hardness of the composite were 76MPa (7.7kgf/mm
2) and 64KHN. These values were lower than the commercially available chemically cured composite used as a reference. Eluted metal from the composite in 1% lactic acid solution for 7 days showed 0.7mg/cm
2, but in 0.9% NaCl solution for 7 days, it could not be detected.
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Taira MIYASAKA
1996 Volume 15 Issue 2 Pages
98-110,249
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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The binary system of hybrid fillers selected from four irregular fillers (1.7-21.5μm), five spherical fillers (0.46-31.2μm), and a microfiller of 0.04μm, were applied to photo cure composite resin and mechanical properties were measured. The strength for the hybrid of irregular and spherical fillers tended to increase as the size of component fillers decreased. The strength for the hybrid of the same fillers in shape also increased as the size of fillers decreased. The strength for the hybrid containing 30% microfiller showed the same trend, especially, the largest strength was obtained from hybrids containing small spherical fillers.
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Kenji OKA, Takao HANAWA, Masayuki KON, Hae-Hyoung LEE, Fumiaki KAWANO, ...
1996 Volume 15 Issue 2 Pages
111-120,250
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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The bonding strength to titanium, thermal expansion, and bending strength of glassy porcelain containing barium of 5, 10, and 15 mass% were estimated and compared with those of barium-free porcelain, to estimate the effect of barium content on bonding strength to titanium. The three different glassy porcelains containing barium were made by melting at 950°C. The bonding strength of a commercial porcelain to titanium increased with the addition of barium. Bending strength and thermal expansion were not affected by the barium content. Therefore, the addition of barium to porcelain is effective for strengthening the bonding of porcelain to titanium.
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Kenzo ASAOKA, John A. TESK
1996 Volume 15 Issue 2 Pages
121-131,250
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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The aim of this study was to clarify the effect of heating rate on the development of both transient and residual stresses in investment molds. Solid, cylindrical, gypsum-based molds were modeled and theoretical calculations made of temperature distributions with a constant heating rate. These calculations used experimental thermal diffusivity data obtained with a laser flash method. The simulations calculated transient thermal stresses during heating and at the end of heating for two surface conditions: an unrestricted surface, and a surface restricted by a casting ring. The simulation model developed nonuniform strains and stresses at casting temperature; tangential stress was compressive at the surface and tensile at the mid-point for the unrestricted surface model. The surface restricted model developed compressive tangential stresses throughout the mold at the casting temperature. This resulted in significant thermal strain differences compared to the magnitudes of expansion of the mold due to heating.
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Kunio IKEMURA, Yoshiaki KOURO, Takeshi ENDO
1996 Volume 15 Issue 2 Pages
132-143,251
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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To develop a self-etching primer for ground dentin, 4-acryloxyethyltrimellitic acid (4-AET) was newly synthesized, and the effect of concentrations varying from 0 (control) to 56.5wt% 4-AET in the water/HEMA primer on bonding to the dentin was investigated. Bond strength to the dentin was significantly affected by the inclusion of 4-AET in the primer which also contained N, N-di(hydroxyethyl)-
p-toluidine (DEPT) when compared with the control (0% 4-AET) (p<0.01). The optimum 4-AET-concentration and the mean bond strength (SD) were found to be 6.5wt%: 24.2 (3.6)MPa, 37.4wt%: 25.3 (4.4)MPa, 47.2wt%: 26.9 (11.6)MPa and 54.4wt%: 29.7 (12.9)MPa. The role of DEPT in the 4-AET/HEMA primer was assessed, and the optimum DEPT-concentration was found to be 0.154 and 0.307mol%. Regarding the hypothetical bonding mechanism to dentin, it was thought that the ionized 4-AET in water/HEMA would penetrate into dentin substrates, and DEPT as an accelerator
in situ would facilitate photo-polymerization at the dentin-resin interface, and result in increased bond strength to ground dentin.
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Kunio IKEMURA, Koichi ARAI, Hirokazu HASHIMOTO, Takaya KAWAKAMI
1996 Volume 15 Issue 2 Pages
144-153,251
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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The effect of the inclusion of aminobenzoic acid derivatives (ABAD) in a self-etching primer comprising 4-acryloxyethyltrimellitic acid (4-AET), HEMA and water on shear bond strength to ground dentin was investigated. The mean bond strengths to dentin were significantly increased by the inclusion of 0.307mol% ABAD in the 4-AET/HEMA primer, when compared with the control (0wt% ABAD) (p<0.01). A particu-larly high value (38.0MPa) of shear bond strength was obtained in the use of the primer containing
p-nitroanthranilic acid (
p-NAA). It seemed to assume that the effect of
p-NAA could be caused by the strong electron-withdrawing group of -NO
2. From SEM observation, it was found that bonding resin appeared to adhere strongly to the ground dentin without formation of any resin-tags in the dentinal tubules. It was thought that the ABAD with 4-AET/HEMA could perform facilitating photo-polymerization at the bonding interface, and resulted in increased bond strength to ground dentin, and that the bond strength could be affected by the electronegativities of substitutional groups of ABAD.
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Kunio IKEMURA, Koichi ARAI, Takeshi ENDO, Takaya KAWAKAMI, Hirokazu HA ...
1996 Volume 15 Issue 2 Pages
154-167,252
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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To develop a non-polymerization shrinkage adhesive resin, the effects of the contents varying 0∼20wt% radical polymerizable spirocyclic monomers of 2-methylene-1, 4, 6-trioxyaspiro [4, 6] undecane (MTSU) and 2-methylene-8, 9-benzo-1, 4, 6-trioxyaspiro [4, 4] nonane (BTSN) together with three kinds of initiator systems in adhesive resin on bonding to both Ni-Cr alloy and unetched enamel were investigated. Tensile bond strength to either Ni-Cr alloy or unetched enamel was affected by the inclusion of MTSU or BTSN, and indicated that increased contents of MTSU or BTSN resulted in decreased bond strength to the metal in the negative correlations. Regarding the bond strength to Ni-Cr alloy, however, the effective concentration of BTSN was found to be 5wt%, and the mean bond strength was 58.5 and 58.6 MPa, respectively. The data of differential scanning calorimeter measurement, on the other hand, showed that the copolymerization of MTSU with conventional methacrylate monomers was not completely achieved.
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Hiroshi NAKAJIMA, Eduardo LORENZANA, Jack L. FERRACANE, Toru OKABE
1996 Volume 15 Issue 2 Pages
168-174,252
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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This study examined the Hg evaporation behavior during the early setting of amalgams that contain In in the alloy powders. Two different types of commercially available In-containing alloys were tested: an In-particle admixed powder (Indisperse, D) and an In-containing single-composition powder (Indiloy, S).Mercury evaporation from specimens (4mm in dia, 8mm tall) was monitored 10min after trituration to 180min using a mercury vapor analyzer according to the methods used in a previous study
1). The amounts released from 10min to 180min were compared with the results of our previous study on a single-composition amalgam (Tytin, T) with pure Hg and with Hg-In liquids (5 or 10%). Amalgam S and In-containing T terminated Hg evaporation within 180min. There was no significant (
p>0.05) difference in the amount released between T amalgam made using pure mercury and D, and between T amalgam made with 5% In-containing mercury and S amalgam. Mercury release from amalgam D was significantly (
p>0.05) higher than from S or both types of In-containing T amalgam. Adding In to mercury or alloying In into the alloy particles appeared to be more effective in reducing the mercury vapor than admixing pure In particles into the amalgam.
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MIN NYUNT MIN, Yohji IMAI
1996 Volume 15 Issue 2 Pages
175-182,253
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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A study was made on the dentin bonding of MMA/PMMA resin using sulfinic acid/BPO/amine polymerization initiator, to examine: 1) the effect of ferric and copper chloride contained in phosphoric acid or citric acid dentin conditioners, and 2) the effect of the addition of acidic monomers to the resin. Tensile bond strength was significantly improved by conditioning dentin with 10% phosphoric acid containing 3% ferric chloride. The citric acid-based conditioners and the addition of the copper salt to the acidic conditioners were less effective in improving bond strength. The mechanism of the improved bond strength is discussed in terms of polymerization promoting action of ferric ion at the dentin-resin interface. For improving bond strength, the presence of a suitable acidic monomer was essential. Its effectiveness depended on the types of acids: Two phosphoric acid ester monomers were effective but methacrylic acid had little effect.
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Hiroki OHNO, Yoshima ARAKI, Kazuhiko ENDO, Yuro YAMANE, Isao KAWASHIMA
1996 Volume 15 Issue 2 Pages
183-192,253
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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The water durability at adhesion interfaces was investigated by measurement of the peeled area of thin resin films bonded with 4-META resin on metal surfaces after imposing thermal stress using liquid nitrogen. Thermal stress at the adhesion interface was calculated by a computer-aided finite element method. On 18-8 stainless-steel specimens which bond strongly with 4-META resin, total interface failure occurs on specimens with resin thicker than 0.55mm in dry condition. A resin layer of 0.25mm was chosen to study degradation of the adhesion interface by water. The shearing stress was calculated as 16MPa for a 0.25mm thick resin layer. On mild-steel adherend interface with 4-META resin which degrades rapidly by water molecule, the relationship between water immersion time and degradation at the adhesion interface was discussed together with the amount of water penetrated at the interface. The method proposed in the present study is effective as a quick evaluation method for water durability at the adhesion interface.
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Effect of Hygroscopic Expansion and Bond Strength
Masao IRIE, Hiroyuki NAKAI
1996 Volume 15 Issue 2 Pages
193-200,253
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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The present study investigates the effect of storage in water on hygroscopic expansion and shear bond strength to dentin at periods up to 1 week, of the resin-modified glass ionomers for base/liner, and to analyze the effect on the marginal gaps in dentin cavities. For polishing after storage in water for 1 day, the material indicated significantly smaller marginal gaps both in dentin and in Teflon cavities than in those immediately after light-activation. For the results of after storage in water for 1 day, the material indicated significantly greater bond strength than material immediately after light-activation. The improvement of marginal sealability in dentin cavities may be performed not only by hygroscopic expansion during storage in water but also by greater bond strength after the setting reaction which continues to advance during storage in water.
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Kohji YAMAMOTO, Shizue OHASHI, Eiichi TAKI, Kenichi HIRATA
1996 Volume 15 Issue 2 Pages
201-204,254
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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The adherence of oral bacteria to composite resins plays an important role in the development of secondary caries. The present study deals with the adherence to composite resin having various surface roughness of
S. oralis, which is frequently isolated from composite resin squares attached to maxillary first molars. available commerciall resin was used in this experiment.
In vitro bacterial adhesion test was carried out under a sucrose independent conditions. The surface roughness values of each specimen ranged between 0.2μm and 3.0μm. No relationship was observed between the surface roughness values and bacterial adhesion because
S. oralis adhered firmly to the filler particles of all composite resin surfaces.
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Ken-ichi TONAMI, Hidekazu TAKAHASHI, Fumio NISHIMURA
1996 Volume 15 Issue 2 Pages
205-211,254
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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Bovine teeth are used for dental research as a substitute for human teeth. In the present study, the effects of storage on the tensile strength of bovine dentin were investigated. Storage conditions selected were frozen storage for 1 week, 4 weeks, and 1 year. Boiling in water for 45 minutes was also employed to clarify the effect of heat. Dumbbell-shaped specimens were prepared from teeth of each condition and tensile tests were performed immediately. The same tests were also performed on specimens, as a control, prepared from bovine teeth within 8 hours of extraction. The tensile strength of the control was 76.1MPa; 1 week frozen storage, 78.7MPa; 4 weeks, 79.9MPa; 1 year, 79.0MPa. The tensile strength of bovine dentin remained unchanged during one year frozen storage. On the other hand, the tensile strength of bovine dentin after boiling was 70.3MPa, showing that tensile strength had decreased.
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Kouichi WATANABE, Seigo OKAWA, Mitsugu KANATANI, Syuji NAKANO, Osamu M ...
1996 Volume 15 Issue 2 Pages
212-219,254
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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The possibility of the segregation under solidification process using a centrifugal casting machine was investigated using an electron probe microanalyzer with elemental distribution map, line analysis and quantitative analysis. When a very small quantity of platinum was added to local molten titanium during the casting process, macroscopic segregation was observed under conditions of density difference of 0.1g/cm
3 at the most, confirming that the centrifugal force of the casting machine is extremely strong. When a Ti-6Al-4V alloy was cast, however, no macroscopic segregation was observed. The centrifugal force of the casting machine examined in the present study hardly results in the body-force segregation in this titanium alloy.
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Hiroshi MURAKAMI, Shigemitsu SAKUMA, Kentarou NAKAMURA, Yutaka ITO, Ma ...
1996 Volume 15 Issue 2 Pages
220-225,255
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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Over time, removable dentures tend to become unsanitary and emit unpleasant odors, and oral mucosa sometimes becomes inflamed or denture stomatitis is caused by denture plaque. Recently, various cleaning products designed to keep removable dentures sanitary have appeared on the market. It is known that denture plaque is mainly composed of
Candida albicans (C. albicans), and that ozone seems to inhibit these micro-organisms. Accordingly, a denture cleaner using ozone bubbles (ozone concentration of about 10ppm) was considered as clinically appropriate because of its strong disinfecting and deodorizing power, and high biological safeness. The effectiveness of this cleaner against
C. albicans was investigated using. Results showed that
C. albicans decreased to about 1/10 after 30min and to 1/10
3 after 60min.
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Aya KURIHARA, Atsufumi MANABE, Kazuyuki KATSUNO, Kazuo ITOH, Hisashi H ...
1996 Volume 15 Issue 2 Pages
226-232,255
Published: December 25, 1996
Released on J-STAGE: February 12, 2009
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The purpose of the present study was to evaluate the safety of ethylene glycol (EG) and 1, 6-hexanediol (HD) solutions as experimental dentin primers when subjected to the guinea pig maximization test (GPMT), primary irritation test, cumulative skin irritation test and human patch test. No primary and cumulative skin irritation resulting from the use of 62.5% EG or 45% HD solutions was observed. In the case of GPMT, the animals sensitized with 2-hydroxyethyl methacrylate (2-HEMA) responded to 100% HD. 62.5% EG and 45% HD as dentin primers were safer than 2-HEMA such as a methacrylic primer.
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