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Takuma TSUGE, Yoshiyuki HAGIWARA
2009 Volume 28 Issue 4 Pages
373-381
Published: 2009
Released on J-STAGE: August 31, 2009
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To date, there is no evidence that internal anti-rotation configurations are better than external ones. The purpose of this study was to evaluate the effect of eccentric cyclic loading on abutment screw loosening in internal and external hexagon implants with either of these two screw materials, titanium (Ti) alloy
versus gold alloy. The reverse torque value of the abutment screw was measured before (initial preload) and after loading (post-loading). The prepared assemblies were divided into four groups (A to D). Groups A and B used internal hex implants with gold alloy and Ti alloy abutment screws respectively. Groups C and D used external hex implants with gold alloy and Ti alloy abutment screws respectively. In all the groups, post-loading preload was significantly (
p<0.05) higher than initial preload. Further, two-way ANOVA indicated that the implant-abutment connection did not have an effect, but the abutment screw material did. In particular, Ti abutment screws were less likely to come loose.
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Kenjiro NAKANO, Tatsuhide HAYASHI, Hideki KAWAI, Yukiko TAKEI, Yosuke ...
2009 Volume 28 Issue 4 Pages
382-387
Published: 2009
Released on J-STAGE: August 31, 2009
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In a diffusion chamber (DC) system, cells are cultured
in vivo — hence making it possible to minimize infection and foreign material contamination. In view of this merit, we devised a technique to combine a DC system and a scaffold to the end of incubating sufficient host cells for grafting. In the present study, PLGA sponge and rat bone marrow cells were encapsulated inside a DC and then placed inside the abdominal cavities of rats. DCs were removed at two or four weeks after grafting. At four weeks after grafting, fibrous and calcified tissue matching the shape of the PLGA sponge was formed. These results suggested that the PLGA sponge was an effective scaffolding material in inducing three-dimensional tissue formation and that combination with a DC system resulted in a cell mass matching the scaffold shape. In addition, the cells were cultured
in vivo — which meant that DC culturing did not require special incubation facilities or technologies after grafting.
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Yosuke SATO, Ken MIYAZAWA, Natsu SATO, Kenjiro NAKANO, Yukiko TAKEI, T ...
2009 Volume 28 Issue 4 Pages
388-395
Published: 2009
Released on J-STAGE: August 31, 2009
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We sought to investigate whether the photocatalytic function of rutile-type titanium dioxide is applicable for orthodontic brackets. To this end, TiO
2 specimens were compressed and sintered. Then, each specimen was analyzed by X-ray diffraction to confirm that no compositional changes had taken place. Next, the surface of each specimen was observed with a colorimeter, scanning electron microscope (SEM), and atomic force microscope (AFM). Fundamental material properties after calcination were measured. The photocatalytic function was evaluated using the decolorization method with toluidine blue. The following were observed with the increase of calcinations temperature: growth of crystal particles, decrease in surface roughness and surface brightness, but increase in shrinkage percentage and compressive strength. The aesthetic and mechanical properties of TiO
2 material were adequate when compared with other bracket materials. In addition, it had a satisfactory photocatalytic function after high-temperature calcination. Based on the favorable results obtained, rutile-type titanium dioxide seemed to be applicable for the fabrication of self-cleaning orthodontic brackets.
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Hakan DEVELIOGLU, Serpil UNVER SARAYDIN, Unal KARTAL
2009 Volume 28 Issue 4 Pages
396-400
Published: 2009
Released on J-STAGE: August 31, 2009
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Bone grafts have been widely used to fill osseous defects in medicine, dentistry, and periodontology. The purpose of this study was to investigate the effects of a xenograft (Unilab Surgibone
®) on experimentally created parietal bone defects in rats. To this end, 14 rats were employed in the present study and in each of them, 5-mm-diameter defects were created on the parietal bone. The right defect sites were filled with the xenograft material, while the left sites were used as control. After 30 days, the rats were sacrificed and tissue samples were retrieved from the defect sites of the cranium. Dense collagenous tissue was observed in the control area, whereas the xenograft particles were surrounded by a fibrous tissue layer at the implantation site. Based on the findings obtained, it could be concluded that the investigated xenograft seemed biocompatible and could be proposed as a potential material for filling osseous defects.
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Jun LI, Isao SHIBUYA, Ichiko TESHIMA, Kimiya NEMOTO, Norihiro NISHIYAM ...
2009 Volume 28 Issue 4 Pages
401-408
Published: 2009
Released on J-STAGE: August 31, 2009
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In this study, a dual-curing type composite resin cement that included a photo-initiator and two accelerators was designed. In particular, special emphasis was made on addressing questions on the effects from different amounts of additional accelerators on the flexural strength of the designed experimental composite resin cement, as well as on the tensile bond strength of the bracket bonded onto the enamel surface by the experimental composite resin cement.
When 0.25 mass% of the
p-tolydiethanolamine and sodium
p-toluenesulfinate were added, the maximum flexural strength was obtained for the chemical-cured and dual-cured experimental composite resin cement. The dual-cured experimental composite resin cement's flexural strength value was in the mid-range of the values exhibited from the commercial resin cements. However, the dual-cured experimental composite resin cement exhibited noticeably high tensile bond strength when compared with the results obtained with the commercial resin cements.
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Yuki KATSUMATA, Satoru HOJO, Naho HAMANO, Tomonaga WATANABE, Hiroaki Y ...
2009 Volume 28 Issue 4 Pages
409-418
Published: 2009
Released on J-STAGE: August 31, 2009
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This study aimed to investigate the shear bond strength of an autopolymerizing resin to a nylon denture base polymer (Lucitone FRS: LT) subjected to different surface treatments, and the results thereof compared with a heat-polymerizing resin and a polycarbonate polymer. Specimens were divided into five groups according to the surface treatment method: polishing (#600), sandblasting, adhesive primer application (resin primer), sandblasting + adhesive primer application, and tribochemical coating (Rocatec system). Following which, specimens were subjected to a shear bond strength test and Si concentrations were measured using an electron probe microanalyzer (EPMA). On shear bond strength, that of LT with tribochemical coating was significantly higher than the other groups. On EPMA results, the surface of LT with tribochemical coating was found to be covered with a silica film. Therefore, findings in this study indicated that silica-coating by Rocatec system was effective in improving the bond strength of nylon denture base polymer to autopolymerizing repair resin.
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Shinya HORIUCH, Kazuyuki KANEKO, Hiroko MORI, Emi KAWAKAMI, Takashi TS ...
2009 Volume 28 Issue 4 Pages
419-425
Published: 2009
Released on J-STAGE: August 31, 2009
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This study aimed to evaluate the effectiveness of self-etching and phosphoric acid-etching orthodontic adhesives for enamel bonding in simulated clinical conditions. By using two self-etching (Transbond Plus, TP; Beauty Ortho Bond, BB) and two acid-etching (Transbond XT, TX; Superbond Orthomite, SB) adhesives, orthodontic brackets were bonded on human premolars (
n=10 for each adhesive). Ten teeth without bracket bonding,
i.e., intact enamel surfaces, were used as control for SEM observation. After 7-day storage in lactic acid solution, bracket debonding force by means of debonding pliers, adhesive remnant index (ARI), and enamel surface morphology were examined. All the tested adhesives exhibited sufficient bond strength for clinical use. The ARI scores were almost the same among the four adhesives. In terms of SEM observation, the enamel surfaces in the control and TP groups showed a slight change after immersion in lactic acid solution, while the BB group showed less change on the enamel surface compared with the TP group. Meanwhile, the two acid-etching adhesives caused considerable demineralization. Taken together, these findings indicated that the action of self-etching systems was evidently more conservative.
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Takuya OHKUBO, Makoto OIZUMI, Takuya KOBAYASHI
2009 Volume 28 Issue 4 Pages
426-432
Published: 2009
Released on J-STAGE: August 31, 2009
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Effects of methylmercaptan solution (MS), a volatile sulfur compound produced by gram-negative oral microorganisms, on the adhesion of reline denture resins were investigated. For this purpose, a total of 120 disk-shaped specimens prepared from a heat-polymerized denture base resin (Acron) immersed in MS of different concentrations (0.01, 0.1, and 1.0 mol) as well as in purified water as a control at 37°C for 4 weeks. Each of three commercial autopolymerizing reline resins (Rebaron, Mild Rebaron, and Tokuyama Rebase II) was bonded to a specimen. The shear bond strength tests were conducted for the specimens, with and without the application of a primer. The bond strength with 1.0 mol MS was significantly lower than those with other solutions (
p < 0.05). The primer application had a significant positive effect on the bond strength. The debonded Acron surfaces showed evidence of incomplete polymerization. The results suggested a potential adhesion-inhibiting effect of the MS on relined dentures.
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Yoshiharu NAKAMURA, Satoru HOJO, Hideaki SATO
2009 Volume 28 Issue 4 Pages
433-437
Published: 2009
Released on J-STAGE: August 31, 2009
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The objective of this study was to test the hypothesis that thermal cycling weakens the flexural strength of porcelain. Specimens of Deguceram Gold and Vita Omega 900 were tested in four groups of 30 specimens each: in the original glazed condition
versus being ground with 1000-grit, 600-grit, and 100-grit silicon carbide abrasives. Corresponding to these four types of surface treatments, four groups of 30 specimens per group received 5,000 times of thermal cycling. Flexural strength was measured using a four-point flexural test, and Weibull modulus was calculated. Within each type of surface treatment, the thermal cycling treatment did not result in any decrease in flexural strength although it caused the Weibull modulus to become smaller — except for the control and thermal-cycled groups of 600-grit surface treatment.
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Tae-Sung JEONG, Ho-Seung KANG, Sung-Ki KIM, Shin KIM, Hyung-Il KIM, Yo ...
2009 Volume 28 Issue 4 Pages
438-445
Published: 2009
Released on J-STAGE: August 31, 2009
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The present study sought to evaluate the effect of resin shades on the degree of the polymerization. To this end, response variables affected by the degree of polymerization were examined in this study — namely, microhardness, polymerization shrinkage, and color change. Two commercial composite resins of four different shades were employed in this study: shades A3, A3.5, B3, and C3 of Z250 (Z2) and shades A3, A3.5, B3, and B4 of Solitaire 2 (S2). After light curing, the reflectance/absorbance, microhardness, polymerization shrinkage, and color change of the specimens were measured. On reflectance and absorbance, Z2 and S2 showed similar distribution curves regardless of the resin shade, with shade A3.5 of Z2 and shade A3 of S2 exhibiting the lowest/highest distributions. Similarly for attenuation coefficient and microhardness, the lowest/highest values were exhibited by shade A3.5 of Z2 and shade A3 of S2. On polymerization shrinkage, no statistically significant differences were observed among the different shades of Z2. Similarly for color change, Z2 specimens exhibited only a slight (Δ
E*=0.5–0.9) color change after immersion in distilled water for 10 days, except for shades A3 and A3.5. Taken together, results of the present study suggested that the degree of polymerization of the tested composite resins was minimally affected by resin shade.
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Shuzo KITAYAMA, Toru NIKAIDO, Rena MARUOKA, Lei ZHU, Masaomi IKEDA, Ak ...
2009 Volume 28 Issue 4 Pages
446-453
Published: 2009
Released on J-STAGE: August 31, 2009
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This study was conducted to enhance the tensile bond strengths of resin cements to zirconia ceramics. Fifty-six zirconia ceramic specimens (Cercon Base) and twenty-eight silica-based ceramic specimens (GN-1, GN-1 Ceramic Block) were air-abraded using alumina. Thereafter, the zirconia ceramic specimens were divided into two subgroups of 28 each according to the surface pretreatment; no pretreatment (Zr); and the internal coating technique (INT). For INT, the surface of zirconia was coated by fusing silica-based ceramics (Cercon Ceram Kiss). Ceramic surfaces were conditioned with/without a silane coupling agent followed by bonding with one of two resin cements; Panavia F 2.0 (PF) and Superbond C&B (SB). After 24 hours storage in water, the tensile bond strengths were tested (
n=7). For both PF and SB, silanization significantly improved the bond strength to GN-1 and INT (
p<0.05). The INT coating followed by silanizaton demonstrated enhancement of bonding to zirconia ceramics.
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Hiroyuki ARIKAWA, Hideo TAKAHASHI, Takahito KANIE, Seiji BAN
2009 Volume 28 Issue 4 Pages
454-460
Published: 2009
Released on J-STAGE: August 31, 2009
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The purpose of this study was to investigate effects of various visible light photoinitiators on the polymerization efficiency and color of the light-activated resins. Four photoinitiators, including camphorquinone, phenylpropanedione, monoacrylphosphine oxide (TPO), and bisacrylphosphine oxide (Ir819), were used. Each photoinitiator was dissolved in a Bis-GMA and TEGDMA monomer mixture. Materials were polymerized using dental quartz-tungsten halogen lamp (QTH), plasma-ark lamp and blue LED light-curing units, and a custom-made violet LED light unit. The degree of monomer conversion and CIE
L*a*b* color values of the resins were measured using a FTIR and spectral transmittance meter. The degree of monomer conversions of TPO- and Ir819-containing resins polymerized with the violet-LED unit were higher than camphorquinone-containing resin polymerized with the QTH light-curing unit. The lowest color values were observed for the TPO-containing resin.
Our results indicate that the TPO photoinitiator and the violet-LED light unit may provide a useful and improved photopolymerization system for dental light-activated resins.
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Daisuke YAMASHITA, Miho MACHIGASHIRA, Motoharu MIYAMOTO, Hironobu TAKE ...
2009 Volume 28 Issue 4 Pages
461-470
Published: 2009
Released on J-STAGE: August 31, 2009
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The aim of this study was to evaluate the effect of surface roughness on the initial attachment of mouse osteoblast-like cells on ceriastabilized zirconia/alumina nanocomposite (NANOZR) and yttria-stabilized zirconia (3Y-TZP) in comparison to those on pure titanium (Ti) and alumina oxide (AO). Specimens with smooth and rough surfaces were prepared by grinding with diamond paper or by sandblasting, respectively. For four substrates examined, the number of attached cells on the rough surface specimens was significantly higher than that on the smooth surface specimens (
p < 0.05). Integrin α
5 and
β1 expression had a greater increase in rough surface specimens than in smooth surface specimens. Actin cytoskeleton organization was, however, similar for both smooth and rough surface specimens. NANOZR and 3Y-TZP produced good cell attachment, similar to Ti and AO. The overall results demonstrated that NANOZR and 3Y-TZP with rough surface could provide good initial cell responses, adequate for future implant usage.
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Masanori OMAE, Yasuo SHINNOU, Kumiko TANAKA, Tomoko ABO, Takashi NAKAT ...
2009 Volume 28 Issue 4 Pages
471-476
Published: 2009
Released on J-STAGE: August 31, 2009
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The aim of this study was to investigate the effect of Er:YAG laser irradiation on human dentin surface using X-ray photoelectron spectroscopy (XPS). 10 human dentin disks were prepared from extracted human molars for XPS analysis. These specimens were divided into two groups of five: a control group and group that were irradiated by an Er:YAG laser beam (100 mJ, 1Hz). All specimens were analyzed by XPS over a wide scanning range and narrow scanning ranges. The Ca/P ratio was calculated from the XPS results.
In the results, the binding energies of Ca, P, and N in the laser-irradiated group were higher than those in the control group. The Ca/P ratio of the Er:YAG laser irradiated group (1.24±0.05) was significantly lower than that of the control group (1.52±0.16).
This study showed that Er:YAG laser irradiation decreased Ca/P ratio and denatured the collagen of human dentin.
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Ken NIWA, Kiyotaka OGAWA, Ken MIYAZAWA, Taiju AOKI, Tatsushi KAWAI, Sh ...
2009 Volume 28 Issue 4 Pages
477-486
Published: 2009
Released on J-STAGE: August 31, 2009
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We are currently developing a small perforated titanium subperiosteal implant specifically for orthodontic therapy, which can be placed anywhere on the bone surface. In the present study, we coated this implant with hydroxyapatite (HA) or α-tricalcium phosphate (α-TCP) in an attempt to shorten the initial stabilization period relative to the few months that is usually required. The coated implants were placed beneath the periosteum in rabbit femora. The implants were observed by radiographically and histologically, and measured the tensile strength of the bone–implant interface.
Two weeks after placement, the volume of new bone formed in the perforations of the implant was significantly greater for the α-TCP-coated implants than for the HA-coated implants.
Our findings indicate that new bone is formed faster in the surrounding area with α-TCP- and HA-coated subperiosteal implants than with uncoated implants, and that α-TCP is a particularly effective stimulator of new bone formation.
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Chie IHARA, Hidekazu TAKAHASHI, Ryosuke MATSUI, Takuto YAMANAKA, Toshi ...
2009 Volume 28 Issue 4 Pages
487-492
Published: 2009
Released on J-STAGE: August 31, 2009
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The purpose of this study was to assess the behavior of laminated thermoforming materials in an underwater environment to understand the durability of mouthpieces for scuba diving. Two thermoforming materials, polyolefin (PO) and ethylene-vinyl acetate copolymer (EV), were laminated and stored in air, 37°C water, and 37°C water under 0.2-MPa pressure for 1 and 4 weeks . The load/ bonding width (bonding strength: BS) and displacement at the start of delamination (SD) and fracture (FR) were analyzed with 3-way ANOVA. BS values at SD and FR in air were significantly greater than those under the other conditions, and the BS at SD of EV was significantly greater than that of PO, though the effects of materials, duration and their interactions were not significantly different. The displacements at SD and FR were significantly influenced by the material. These results suggest that both materials can be employed for making a diving custom mouthpiece.
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Yasuhiro IIDA, Toru NIKAIDO, Shuzo KITAYAMA, Tomohiro TAKAGAKI, Go INO ...
2009 Volume 28 Issue 4 Pages
493-500
Published: 2009
Released on J-STAGE: August 31, 2009
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The purpose of this study was to evaluate dentin bond strengths and to observe the adhesive-dentin interface after acid-base challenge using fluoride-free and fluoride-releasing self-etching adhesive systems; Clearfil SE Bond (SE), FL-Bond (FL) and FL-Bond II(FL II). Fifteen dentin surfaces from human molars were ground and bonded with one of three adhesive systems. The microtensile bond strength (μTBS) test was performed at a crosshead speed of 1 mm/min. The interface of the bonded specimens after acid-base challenge were also examined by a SEM. The μTBS of SE were significantly higher than those of FL and FL II (
p<0.05), however, there were no significant differences between FL and FL II (
p>0.05). An acid-base resistant zone (ABRZ) was observed in all the groups, however, formation of the ABRZ was material dependent. Fluoride-release from the adhesive is a key factor to create thick ABRZ.
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Takahito KANIE, Koichi TOMITA, Masayuki TOKUDA, Hiroyuki ARIKAWA, Koic ...
2009 Volume 28 Issue 4 Pages
501-506
Published: 2009
Released on J-STAGE: August 31, 2009
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The purpose of this investigation was to determine whether experimental light-curing soft lining materials (ESLMs) based on commercially available urethane acrylate oligomers (UA-160TM, UV-3200B, UV-3500BA, and UV-3700B) are suitable for clinical use by measuring their viscosity, compressive modulus, Shore A hardness, tensile strength, adhesive strength, and cytotoxicity. The viscosities of the four ESLMs at 25°C were 10.5 Pa·s, UV-3500BA; 144.0 Pa·s, UA-160TM; 328.8 Pa·s, UV-3700B; and 1079.7 Pa·s, UV-3200B. Polymerized UV-3700B was very soft, whereas the softness of the other ESLMs was similar to that of conventional soft lining materials. No significant difference in adhesive strength was observed between UV-3500BA and UV-3700B at 1 day and those at 12 months. Cytotoxicity was measured by a MTT-based assay using HeLa S3 and Ca9-22 cells. UV-3200B and UV-3700B oligomers and all four polymerized ESLMs showed cell viability over 95.2% (
p < 0.05).
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Yuki HIRAJIMA, Hidekazu TAKAHASHI, Shunsuke MINAKUCHI
2009 Volume 28 Issue 4 Pages
507-512
Published: 2009
Released on J-STAGE: August 31, 2009
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The present study investigated the influences of a denture strengthener on the deformation of a maxillary complete denture. Three groups of maxillary complete dentures were fabricated (Group 1 without a strengthener; Group 2 with a Co-Cr alloy wire strengthener; Group 3 with an experimental fiberglass strengthener). The denture deformation during occlusal load was monitored using four rosette strain gauges. The maximum principle strain (MPS) of each gauge, except for that at the labial frenum, increased proportionally with the increase of the applied load. The MPS at the incisive papilla (IP) was consistently the highest among the measuring positions regardless of the denture types. The MPS at IP in Group 1 was significantly higher than those in Groups 2 and 3 when the applied load was equal (
p<0.05). These results suggested that the strengthener in the acrylic maxillary complete denture would reduce deformation of the denture during occlusal loading.
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Seigo OKAWA, Kikuo HOMMA, Mitsugu KANATANI, Kouichi WATANABE
2009 Volume 28 Issue 4 Pages
513-518
Published: 2009
Released on J-STAGE: August 31, 2009
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Electrochemical deposition of calcium phosphate (CAP) on valve metals such as Ta, Nb, and Zr, was performed by anodic oxidation with alternate polarity inversion at an applied 20 VDC. A saturated hydroxyapatite(HAP)-phosphoric acid solution (pH 3) was used as the electrolyte. FTIR, XRD, and XPS were employed to investigate the detailed characteristics of the deposition. HAP was precipitated on Ta; HAP including brushite and monetite on Nb; and HAP and monetite on Zr. The Ca/P atomic ratios were 1.3-1.5 by XPS, and HPO
42– bands were detected on Ta by FTIR. Therefore, the HAP precipitated on Ta was a Ca-deficient HAP. In addition, the XPS spectra of the specimens showed that phosphate ions were incorporated into the anodic oxide film. Deposits with nano-grain size were observed by AFM. The results confirmed that CAP with nano-grain size was deposited on valve metals by the anodic oxidation with polarity inversion.
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