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Nicoleta ILIE, Ester JELEN, Tatiana CLEMENTINO-LUEDEMANN, Reinhard HIC ...
2007 Volume 26 Issue 2 Pages
149-155
Published: 2007
Released on J-STAGE: February 06, 2009
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In modern research, development of monomers that reduce shrinkage of composite materials remains an ongoing quest and perennial challenge. The purpose of this study, therefore, was to analyze the shrinkage behaviour of an innovative composite material for dental restorations based on a monomer with a new chemical formulation, known as silorane. To this end, shrinkage stress development during curing, gel point, and coefficient of near linear fit of contraction stress/time were evaluated after polymerizing the material with 10 different curing regimes.
Shrinkage stress varied between 1.4 MPa after a 10-second curing in a pulsed regime to 4.4 MPa after curing for 40 seconds with a high energy curing unit, Bluephase. Pearson correlation analysis showed that with respect to the tested curing units, shrinkage stress correlated significantly with energy density (0.89), irradiance (0.70), curing time (0.51), coefficient of near linear fit of contraction (0.70), and gel point (-0.60).
Silorane exhibited low shrinkage stress values in comparison to regular methacrylate composites. Nevertheless, stress due to thermal contraction when the light exposure ended was not negligible—but could be reduced by applying the appropriate curing strategy.
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Kyou HIASA, Yasuhiko ABE, Yasuhiro YOSHIDA, Tsuyoshi TAJI, Kazuomi SUZ ...
2007 Volume 26 Issue 2 Pages
156-161
Published: 2007
Released on J-STAGE: February 06, 2009
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The purpose of this study was to investigate the chemical interaction between titanium implant surface and amino acids. Pure titanium disks were pretreated with 10 N HCl and ultrapure water at room temperature for 30 minutes each. Disks were then modified with one of the three amino acids—L-aspartic acid, L-serine, or L-threonine—at 37°C for 12 hours. Modification with oxalic acid was used as a control. By means of X-ray photoelectron spectroscopy (XPS), amino acid powders and the modified surfaces without or with ultrasonic water rinsing were chemically analyzed. It was revealed that the N 1s peak which originated from amino acids was not or hardly detected in the wide scan spectra of amino acid-modified surfaces. Moreover, the COO
- peak which originated from oxalic acid could hardly be detected in the narrow scan spectrum of the C 1s region of oxalic acid-modified surface with ultrasonic water rinsing. Based on the results of this study, it was concluded that amino acids could not chemically bond to the titanium surface.
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Kazuya DOI, Takayasu KUBO, Kazuhiko HAYASHI, Koichi IMURA, Yasumasa AK ...
2007 Volume 26 Issue 2 Pages
162-169
Published: 2007
Released on J-STAGE: February 06, 2009
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The purpose of this study was to evaluate the effect of osteogenic differentiation of bone marrow stromal stem cells (BMSCs) on bone formation in a novel interconnected porous calcium hydroxyapatite (IP-CHA). BMSCs/IP-CHA composites, as a cell-hybrid artificial bone, were made by injecting BMSCs solution into IP-CHA scaffolds. To induce osteogenic differentiation, BMSCs/IP-CHA composites were subcultured for three, seven, 10, and 14 days. At the end of each subculture period, BMSCs/IP-CHA composites were examined by SEM and ALP staining. BMSCs/IP-CHA composites of different osteogenic groups of subculture were also placed into bone sockets in the right femur of beagle dogs. After four weeks, same placement procedure was done in the left femur. BMSCs/IP-CHA subcultured for 10 and 14 days were ALP-positive as opposed to those of three and seven days. At four weeks after placement, bone formation was superior at the 10- and 14-day subculture groups. Based on the results obtained, it was suggested that osteogenic differentiation periods with 10 and 14 days of subculture for BMSCs/IP-CHA as a cell-hybrid artificial bone were beneficial in promoting bone formation.
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Kazuhiko HAYASHI, Takayasu KUBO, Kazuya DOI, Yasuhiko TABATA, Yasumasa ...
2007 Volume 26 Issue 2 Pages
170-177
Published: 2007
Released on J-STAGE: February 06, 2009
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This study sought to clarify the effectiveness of bFGF-gelatin hydrogel complex on bone regeneration around implants for the development of a new drug delivery system for bone augmentation. Twenty-four titanium implants (ø3.3 mm×10 mm) were placed into edentulous areas of the mandibles of four beagle dogs with the upper four screw threads exposed at buccal side. bFGF-gelatin hydrogel complex with 0, 0.1, 1, 10, 100 μg bFGF or autogenous bone (as control) then filled the bone defect site to cover the exposed screw threads. After eight weeks, tissue specimens including implants were evaluated histologically and histomorphometrically. Histological observation showed new bone formation around exposed screw threads in the groups with 1, 10, 100 μg bFGF and autogenous bone—a striking contrast to the groups with contents of 0 and 0.1 μg bFGF. These results thus suggested that bFGF-gelatin hydrogel complex using an optimum amount of bFGF was useful for bone augmentation around implants.
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Naofumi AOKI, Tsukasa AKASAKA, Fumio WATARI, Atsuro YOKOYAMA
2007 Volume 26 Issue 2 Pages
178-185
Published: 2007
Released on J-STAGE: February 06, 2009
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To investigate the dependence of biocompatibility of carbon materials on crystal structure with the aim of developing biomedical applications, single-(SW) and multi-walled (MW) carbon nanotubes (CNTs) were employed as scaffolds for cell culture and compared with graphite (GP). SaOS2 cells were used to investigate the properties and response of osteoblast-like cells. Polycarbonate membranes (PC) coated with CNTs by vacuum filtration formed a meshwork nanostructure. Cells grown on CNTs greatly extended in all directions. In terms of cell proliferation, alkaline phosphatase (ALP) activity, and protein adsorption on the substrates, CNTs showed better results than PC and GP. SW showed the best cell proliferation and total ALP. These favorable results might be attributed to the structure of CNTs and the affinity of CNTs toward proteins, thereby suggesting that CNTs could be potential scaffold materials for cell culture.
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Hiroshi KONO, Motoharu MIYAMOTO, Seiji BAN
2007 Volume 26 Issue 2 Pages
186-193
Published: 2007
Released on J-STAGE: February 06, 2009
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We developed a novel apatite coating method that consisted of two-step of chemical treatment: a combined pretreatment of concentrated acid etching and alkaline treatment, followed by alternate soaking. In this study, the effects of the number of reaction cycles, solution temperature, and soaking time on apatite deposition on titanium surface using alternate soaking were investigated. Results revealed that the deposited amount of apatite mainly depended on the number of reaction cycles, and was independent of solution temperature and soaking time. Characterization results revealed that apatite formation using alternate soaking basically depended on ion exchange and adsorption on the pretreated surface. Further, apatite coating using alternate soaking on a 200-grid titanium mesh confirmed that this coating method was applicable for substrates with complicated shapes.
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Masaaki TAKECHI, Youji MIYAMOTO, Kunio ISHIKAWA, Yukihiro MOMOTA, Tets ...
2007 Volume 26 Issue 2 Pages
194-200
Published: 2007
Released on J-STAGE: February 06, 2009
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Tissue response to apatite cement (AC) containing atelocollagen (AC (ate)) was evaluated using conventional AC (c-AC) as a control material. At one week, the only difference between AC (ate) and c-AC was found in the soft tissue response. With c-AC, a moderate inflammatory response was exhibited: small particles of c-AC were scattered in the cutaneous tissue and many foreign body giant cells were aggregated around the scattered c-AC, whereas AC (ate) showed only a slight inflammatory response with few foreign body giant cells. In terms of bone tissue response, difference between AC (ate) and c-AC was observed at four weeks. New bone formation was observed along the cement at the edge of the pre-existing cortical bone in both c-AC and AC (ate). However, in the case of AC (ate), more abundant and thicker new bone was formed along the cement in the bone marrow when compared with c-AC.
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Tomohisa OGINO, Hiroyasu KOIZUMI, Mika FURUCHI, Mahoko MURAKAMI, Hideo ...
2007 Volume 26 Issue 2 Pages
201-208
Published: 2007
Released on J-STAGE: February 06, 2009
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The purpose of the current study was to evaluate the effect of a metal priming agent on wear resistance of gold alloy-composite joint. Four types of plate specimen were prepared: composite (Estenia C&B or Epricord) alone, type 4 gold alloy alone, alloy-composite joint without priming agent, and alloy-composite joint bonded with a priming agent (Alloy Primer). Three-body wear test was performed using the plate specimens, gold alloy antagonist, and polymer slurry. Joined specimens with priming exhibited less wear depth (in μm; 21.0 for Estenia and 24.9 for Epricord) than the joined specimens without priming (57.8 for Estenia and 46.7 for Epricord). Wear depth of the single plate specimens when abraded with the gold alloy antagonist was ranked as follows: Estenia (9.6), gold alloy (12.8), and Epricord (19.1). It was concluded that the use of a metal priming agent at the alloy-composite interface effectively enhanced the wear resistance of the joined area when under cycled loading.
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Serra OGUZ, Mustafa Murat MUTLUAY, Orhan Murat DOGAN, Bülent BEK
2007 Volume 26 Issue 2 Pages
209-216
Published: 2007
Released on J-STAGE: February 06, 2009
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This study evaluated the color stability of soft denture liners after being exposed to coffee and tea solutions for different time periods. Four soft denture liners and a denture base polymer were tested. Five specimens of each material were immersed in either coffee or tea solution at 50±1°C for one, three, nine, 24, 48, and 96 hours. Color measurements were made using a reflectance spectrophotometer before and after the specimens were exposed to the solutions. After 96 hours' immersion in coffee and tea solutions, coffee produced more marked color changes than did tea for all the materials tested. Surface roughness (Ra) of the materials after being cured against a stainless steel surface was also measured with a contact-type surface roughness measuring instrument. Due to the different surface structures, which thus accounted for the different Ra values, the materials behaved differently when immersed in different solutions.
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Gisele Rodrigues da SILVA, Paulo Cézar SIMAMOTO-JÚNIOR, ...
2007 Volume 26 Issue 2 Pages
217-223
Published: 2007
Released on J-STAGE: February 06, 2009
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This study aimed to analyze the microhardness (KHN) and diametral tensile strength (DTS) of two hybrid resin composites (TPH Spectrum and Filtek Z250). To this end, the composites were polymerized with six laboratory photo-curing units (LPUs) and the results compared with an alternative polymerization method using conventional halogen light source in conjunction with additional polymerization in an autoclave (15 minutes/100°C). LPUs were used following the manufacturers' instructions. Diametral tensile strength and Knoop hardness tests were conducted for all groups (n=5). Data were statistically compared using ANOVA and Tukey's test (α=0.05). Among the LPUs, the one that provided light curing in conjunction with heat and nitrogen pressure resulted in a significant increase in KHN and DTS of resin composites. Between the resin composites, Filtek Z250 showed higher hardness values than TPH Spectrum. It was concluded that the use of alternative polymerization with conventional light polymerization and autoclave was feasible with a wide implication for the general public in terms of reduced dental treatment cost.
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Ki-Young NAM, Jong-Bae KIM, Byeong-Churl JANG, Tae-Yub KWON, Kyo-Han K ...
2007 Volume 26 Issue 2 Pages
224-231
Published: 2007
Released on J-STAGE: February 06, 2009
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The present study evaluated the bonding durability of a flowable composite on bovine dentin using dentin bonding agents with different numbers of application steps: Scotchbond Multipurpose (three steps), Prime & Bond NT and One-Step (two steps), AQ Bond and Prompt L-Pop (one step). Shear bond strength tests were performed, and resin-dentin interface and fracture mode were observed. There were no significant differences in bond strength among the specimens within 37°C storage group (p>0.05) and post-thermocycling group, except between Prompt L-Pop and Scotchbond Multipurpose (p<0.05) in the post-thermocycling group. Further, Scotchbond Multipurpose and One-Step showed significantly lower bond strengths after thermocycling (p<0.05). It was thus shown that the use of simplified bonding agents did not necessarily improve the bonding strength of flowable composites.
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Orhan Murat DOGAN, Giray BOLAYIR, Selda KESKIN, Arife DOGAN, Büle ...
2007 Volume 26 Issue 2 Pages
232-239
Published: 2007
Released on J-STAGE: February 06, 2009
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This study was conducted to observe the changes in impact resistance of a denture base resin reinforced with five types of fiber. E-glass, polyester, rayon, nylon 6, and nylon 6/6 fibers were cut into 2, 4, and 6 mm lengths and added into the resin at a concentration of 3% by weight. Five test specimens for each formulation, as well as control specimens without fiber, were prepared using a mold including a V-shaped notch with 55×10×10 mm dimensions. Impact tests were carried out using a Charpy-type tester. Additionally, surfaces of the impact sections were observed under a scanning electron micro-scope (SEM). Results indicated that impact energy tended to increase with fiber length, and that the highest value was recorded for rayon fiber-reinforced specimens of 6 mm length. E-glass fiber reinforcement produced relatively stable, high values for each length, whereby good interfacial strength between polymer matrix and glass fibers was confirmed by SEM analysis.
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Kohji KAMADA, Yohsuke TAIRA, Keiichi YOSHIDA, Mitsuru ATSUTA
2007 Volume 26 Issue 2 Pages
240-244
Published: 2007
Released on J-STAGE: February 06, 2009
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The purpose of the present study was to evaluate the effect of four silane coupling agents on the bond strength between two resin-modified glass ionomer cements and a machinable leucite glass ceramic. Ceramic specimens were ground with silicon carbide paper and cleaned with phosphoric acid. They were then conditioned and bonded with combinations of four silane coupling agents (GC Ceramic Primer, Clapearl Bonding Agent, Clearfil Mega Bond Porcelain Bonding Kit, and RelyX Ceramic Primer) and two resin-modified glass ionomer cements (Fuji Luting S and Fuji Lute). Shear bond strength was determined after 24-hour immersion in water or after thermocycling of 50,000 cycles. The results showed that every silane coupling agent significantly improved the bond strength. It was thus recommended that resin-modified glass ionomer cement be applied in conjunction with silane coupling agent when luting ceramic restorations.
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Yuhe ZHU, Fumio WATARI
2007 Volume 26 Issue 2 Pages
245-253
Published: 2007
Released on J-STAGE: February 06, 2009
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Carbide layer was formed on the surface of Ti by heating in hydrocarbon atmosphere (benzene C
6H
6) at 1000-1400°C using a high frequency induction heating method. Physical and mechanical properties of carbide-coated Ti were investigated to examine its potential as an abrasion-resistant implant material. Scanning electron microscopy (SEM) showed that the surface of Ti was covered with fine grains of 1-4 μm diameter, depending on heating conditions. In addition, carbide layer of about 1-25 μm thickness was observed on the cross-section of specimens by SEM and energy dispersive spectroscopy. Vickers hardness of surface carbide was found to be more than 2000. Further, Martens scratch test and ultrasonic scaler abrasion test showed that the indentation depth and width of carbide-coated Ti were much smaller than pure Ti, thereby confirming its high abrasion resistance. These results showed that for Ti implant materials that require high abrasion resistance, such as the abutment for dental implants, surface carbide coatings would be an effective means to improve their wear properties.
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Yukio KOJIMA, Hisao FUKUI
2007 Volume 26 Issue 2 Pages
254-259
Published: 2007
Released on J-STAGE: February 06, 2009
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Natural frequencies and vibration modes of four kinds of teeth were calculated by using a mechanical model. The alveolar bone and the tooth were assumed as rigid bodies, while the periodontal ligament was assumed as an elastic spring. All the natural frequencies were within a range of 1 to 10 kHz. The first natural frequencies of four teeth were about 1.5 kHz, and decreased as the root length decreased. Their vibration modes were tipping movements of the root. The natural frequency of the twisting vibration mode, or rotating movement around the tooth axis, was affected by root configuration. When subjected to a periodic force, the tooth and periodontal ligament would vibrate with the corresponding resonance mode. This phenomenon may be used as a method for the diagnosis and the treatment of a periodontal tissue.
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Junichi YAMAZOE, Masaharu NAKAGAWA, Yoshinari MATONO, Akari TAKEUCHI, ...
2007 Volume 26 Issue 2 Pages
260-267
Published: 2007
Released on J-STAGE: February 06, 2009
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The corrosion behaviors of Ti and Ti-6Al-4V, Ti-6Al-7Nb, Ti-0.5Pt, Ti-6Al-4V-0.5Pt, and Ti-6Al-7Nb-0.5Pt alloys were examined using an electrochemical analyzer in artificial saliva containing 0.1 and 0.2% NaF at a pH of 4.0. The SEM observations revealed that the surfaces of the alloys containing 0.5 wt% Pt were not affected in fluoride-containing environments, whereas the surfaces of Ti, Ti-6Al-4V, and Ti-6Al-7Nb alloys were markedly rough. In artificial saliva containing 0.1% NaF at a pH of 4.0, the amounts of Ti dissolved from the Ti, Ti-6Al-4V, and Ti-6Al-7Nb alloys were about 50 times larger than those of the alloys containing 0.5 wt% Pt. The tensile strengths of the alloys containing 0.5 wt% Pt were equal to or higher than those of pure Ti or the alloys without Pt. The Ti-0.5Pt, Ti-6Al-4V-0.5Pt, and Ti-6Al-7Nb-0.5 alloys are expected to be useful in clinical dentistry as new Ti alloys with high corrosion resistance and mechanical strength.
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Motohiro UO, Kiyotaka ASAKURA, Atsuro YOKOYAMA, Makoto ISHIKAWA, Kazuc ...
2007 Volume 26 Issue 2 Pages
268-273
Published: 2007
Released on J-STAGE: February 06, 2009
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Tissues contacting Ti dental implants were subjected to X-ray absorption fine structure (XAFS) analysis to examine the chemical state of Ti transferred from the placed implant into the surrounding tissue. Nine tissues that contacted pure Ti cover screws for several months were excised in a second surgery whereby healing abutments were set. Six tissues that surrounded implants retrieved due to their failure were also excised. Ti distributions in the excised specimens were confirmed by X-ray scanning analytical microscopy (XSAM), and the specimens were subjected to fluorescence XAFS analysis to determine the chemical states of the low concentrations of Ti in the tissues surrounding Ti dental implants. Ti mostly existed in the metallic state and was considered to be debris derived from the abrasion of implant pieces during implant surgery. Oxidized forms of Ti, such as anatase and rutile, were also detected in a few specimens—and existed in either a pure state or mixed state with metallic Ti. It was concluded that the existence of Ti in the tissue did not cause implant failure. Moreover, the usefulness of XAFS for analysis of the chemical states of rarely contained elements in biological tissue was demonstrated.
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Takatsugu YAMAMOTO, Shinichi TAKEISHI, Yasuko MOMOI
2007 Volume 26 Issue 2 Pages
274-279
Published: 2007
Released on J-STAGE: February 06, 2009
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The objective of this study was to analyze the distribution of tensile stresses in indirect restorations prepared in several composite cavity bases. Elastic moduli of 20 materials were measured by nanoindentation technique for finite element analysis. Axisymmetric models of posterior onlays were constructed using combinations of two onlay materials and three cavity base materials. Thickness of resin cement was 50 μm. A vertical load of 95.5 N was applied on the cusp tip. Maximum stress of 18.1 MPa was found in the model consisting of a ceramic onlay and a flowable resin composite base. It was also found that tensile stress increased as the area of the base having a lower elastic modulus became wider. Base materials having higher elastic moduli were determined to be suitable as cavity base materials for posterior restorations.
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Masayuki OOTAKI, Akikazu SHIN-YA, Harunori GOMI, Akiyoshi SHIN-YA, Yuj ...
2007 Volume 26 Issue 2 Pages
280-289
Published: 2007
Released on J-STAGE: February 06, 2009
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By means of finite element analysis, the optimal thickness of fiber framework placed in a fiber-reinforced composite bridge replacing the mandibular first molar was obtained. Test results demonstrated that more than 30% maximum principal stress was reduced by reinforcing with fiber framework in a thickness of up to 0.6 mm for 1.5-mm occlusal clearance. Indeed, maximum principal stress generated in lower embrasure of connectors was reduced from 107 MPa to 70 MPa by maximizing reinforcement effect.
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Hitomi ISHIMURA, Takatomo YOSHIOKA, Hideaki SUDA
2007 Volume 26 Issue 2 Pages
290-295
Published: 2007
Released on J-STAGE: February 06, 2009
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The sealing ability of new adhesive root canal filling materials was evaluated using a new dye penetration method. Twenty-eight single-rooted mandibular premolars were randomly divided into four groups of seven teeth each and filled by lateral condensation using one of these combinations: Resilon point with Epiphany sealer (RE); gutta-percha point with Sealapex sealer (GS); gutta-percha point with dentin activator and Superbond sealer (GDS); or gutta-percha point with Accel primer, dentin activator, and Superbond sealer (GADS). Amount of 0.06% methylene blue dye solution (MB) that leaked from the coronal portion to the apical area was measured with a spectrophotometer at one, four, eight, 15, and 30 days in an accumulative manner. The total amount of leaked MB on day 30 was significantly higher for GDS than the other combinations (p<0.05).
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Serra OGUZ, Mustafa Murat MUTLUAY, Orhan Murat DOGAN, Bulent BEK
2007 Volume 26 Issue 2 Pages
296-302
Published: 2007
Released on J-STAGE: February 06, 2009
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This study evaluated the effect of thermocycling on the tensile strength and tear resistance of four long-term soft denture liners. One light-activated (Astron Light, AL), two chemically activated (GC Reline Soft, GC; Silagum Comfort, SC), and one heat-cured (Molloplast-B, MLP) soft liner materials were tested. Dumbbell and trouser-leg specimen geometries were used for tensile strength and tear resistance tests, respectively. A total of 120 specimens were prepared. Test specimens for each material (n=5) were subjected to thermal cycling for 1,000 and 3,000 cycles between 5°C and 55°C in a thermocycler. Before thermocycling, AL gave the lowest tensile strength, while SC exhibited the highest tear resistance value among the materials tested (p<0.05). Thermal cycling significantly affected the tensile strength of AL as well as the tear resistance values of AL, MLP, and GC materials. This
in vitro study revealed that the tensile strength and tear resistance values of the soft liner materials tested varied according to their chemical compositions.
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