Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/jbm.a.37445

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Other Link： https://onlinelibrary.wiley.com/doi/pdf/10.1002/jbm.a.37445

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

This study investigates the effect of the curing mode (dual-cure vs. self-cure) of resin cements (four self-adhesive and seven conventional cements) on their flexural strength and flexural modulus of elasticity, alongside their shear bond strength to lithium disilicate ceramics (LDS). The study aims to determine the relationship between the bond strength and LDS, and the flexural strength and flexural modulus of elasticity of resin cements. Twelve conventional or adhesive and self-adhesive resin cements were tested. The manufacturer’s recommended pretreating agents were used where indicated. The shear bond strengths to LDS and the flexural strength and flexural modulus of elasticity of the cement were measured immediately after setting, after one day of storage in distilled water at 37 °C, and after 20,000 thermocycles (TC 20k). The relationship between the bond strength to LDS, flexural strength, and flexural modulus of elasticity of resin cements was investigated using a multiple linear regression analysis. For all resin cements, the shear bond strength, flexural strength, and flexural modulus of elasticity were lowest immediately after setting. A clear and significant difference between dual-curing and self-curing modes was observed in all resin cements immediately after setting, except for ResiCem EX. Regardless of the difference of the core-mode condition of all resin cements, flexural strengths were correlated with the LDS surface upon shear bond strengths (R2 = 0.24, n = 69, p < 0.001) and the flexural modulus of elasticity was correlated with them (R2 = 0.14, n = 69, p < 0.001). Multiple linear regression analyses revealed that the shear bond strength was 17.877 + 0.166, the flexural strength was 0.643, and the flexural modulus was (R2 = 0.51, n = 69, p < 0.001). The flexural strength or flexural modulus of elasticity may be used to predict the bond strength of resin cements to LDS.

DOI： 10.3390/polym15051128

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

The objective of this study was to first identify the timing and location of early mineralization of mouse first molar, and subsequently, to characterize the nucleation site for mineral formation...

DOI： 10.1039/d2tb02351b

PubMed

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Publishing type：Research paper (scientific journal)  

Postoperative bacterial infection is a serious complication of orthopedic surgery. Not only infections that develop in the first few weeks after surgery but also late infections that develop years after surgery are serious problems. However, the relationship between host bone and infection activation has not yet been explored. Here, we report a novel association between host bone collagen/apatite microstructure and bacterial infection. The bone-mimetic-oriented micro-organized matrix structure was obtained by prolonged controlled cell alignment using a grooved-structured biomedical titanium alloy. Surprisingly, we have discovered that highly aligned osteoblasts have a potent inhibitory effect on Escherichia coli adhesion. Additionally, the oriented collagen/apatite micro-organization of the bone matrix showed excellent antibacterial resistance against Escherichia coli. The proposed mechanism for realizing the antimicrobial activity of the micro-organized bone matrix is by the controlled secretion of the antimicrobial peptides, including β-defensin 2 and β-defensin 3, from the highly aligned osteoblasts. Our findings contribute to the development of anti-infective strategies for orthopedic surgeries. The recovery of the intrinsically ordered bone matrix organization provides superior antibacterial resistance after surgery.

DOI： 10.1016/j.bioadv.2023.213633

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Metals  

DOI： 10.2320/materia.61.760

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

This study investigated the effects of a multifunctional acrylate copolymer—Trimethylolpropane Triacrylate (TMPTA) and Di-pentaerythritol Polyacrylate (A-DPH)—on the mechanical properties of chemically polymerized acrylic resin and its bond strength to a CAD/CAM polymethyl methacrylate (PMMA) disk. The methyl methacrylate (MMA) samples were doped with one of the following comonomers: TMPTA, A-DPH, or Trimethylolpropane Trimethacrylate (TMPTMA). The doping ratio ranged from 10 wt% to 50 wt% in 10 wt% increments. The flexural strength (FS) and modulus (FM) of PMMA with and without comonomer doping, as well as the shear bond strength (SBS) between the comonomer-doped PMMA and CAD/CAM PMMA disk, were evaluated. The highest FS (93.2 ± 4.2 MPa) was obtained when doped with 20 wt% of TMPTA. For TMPTMA, the FS decreased with the increase in the doping ratio. For SBS, TMPTA showed almost constant values (ranging from 7.0 to 8.2 MPa) regardless of the doping amount, and A-DPH peaked at 10 wt% doping (8.7 ± 2.2 MPa). TMPTMA showed two peaks at 10 wt% (7.2 ± 2.6 MPa) and 40 wt% (6.5 ± 2.3 MPa). Regarding the failure mode, TMPTMA showed mostly adhesive failure between the CAD/CAM PMMA disk and acrylic resin while TMPTA and A-DPH showed an increased rate of cohesive or mixed failures. Acrylate’s addition as a comonomer to PMMA provided improved mechanical properties and bond strength to the CAD/CAM PMMA disk.

DOI： 10.3390/ma15217564

PubMed

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Bone apatite crystals grow in clusters, but the microstructure of these clusters is unknown. This study compares the structural and compositional differences between bone apatite clusters formed in intramembranous (IO) and endochondral ossification (EO). Calvaria (IO) and femurs (EO) are isolated from mice at embryonic days (E) 14.5 to 15.5 and post-natal days (P) 6 to 7, respectively. Results show that the initially formed bone apatite clusters in EO (≅1.2 µm2 ) are >10 times larger than those in IO (≅0.1 µm2 ), without significant changes in ion composition. In IO (E14.5 calvarium), early minerals are formed inside matrix vesicles (MVs). In contrast, in EO (P6 femur epiphysis), no MVs are observed, and chondrocyte-derived plasma membrane nanofragments (PMNFs) are the nucleation site for mineralization. Apatite cluster size difference is linked with the different nucleation sites. Moreover, an alkaline pH and slow P supply into a Ca-rich microenvironment are suggested to facilitate apatite cluster growth, as demonstrated in a biomimetic mineralization system. Together, the results reveal for the first time the distinct and exquisite microstructures of bone apatite clusters in IO and EO, and provide insightful inspirations for the design of more efficient materials for bone tissue engineering and repair.

DOI： 10.1002/adbi.202200076

PubMed

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Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The anisotropic microstructure of bone, composed of collagen fibers and biological apatite crystallites, is an important determinant of its mechanical properties. Recent studies have revealed that the preferential orientation of collagen/apatite composites is closely related to the direction and magnitude of in vivo principal stress. However, the mechanism of alteration in the collagen/apatite microstructure to adapt to the mechanical environment remains unclear. In this study, we established a novel ex vivo bone culture system using embryonic mouse femurs, which enabled artificial control of the mechanical environment. The mineralized femur length significantly increased following cultivation; uniaxial mechanical loading promoted chondrocyte hypertrophy in the growth plates of embryonic mouse femurs. Compressive mechanical loading using the ex vivo bone culture system induced a higher anisotropic microstructure than that observed in the unloaded femur. Osteocytes in the anisotropic bone microstructure were elongated and aligned along the long axis of the femur, which corresponded to the principal loading direction. The ex vivo uniaxial mechanical loading successfully induced the formation of an oriented collagen/apatite microstructure via osteocyte mechano-sensation in a manner quite similar to the in vivo environment.

DOI： 10.3390/ijms23137423

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.ijbiomac.2022.04.163

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Language：English   Publishing type：Research paper (scientific journal)  

We sought to compare the bond strength of resin cement on moist dentin to that on dry dentin, and determine the relationship between the bond strength and flexural strength of resin cement. The water content of the moist and dry dentins was estimated using infrared spectroscopy. Four adhesive and three self-adhesive resin cements were used. At three times of immediately, after one-day storage, and after 20,000 thermocycles (TC 20k), the shear bond strengths were measured. For all resin cements, both the shear bond strength and the flexural strength were the lowest immediately after setting; however, after one day of water storage or TC 20k, these resin cements had the highest values. Regardless of the condition of the dentin surface upon shear bond strength, the flexural strength of each resin cement was correlated with the shear bond strength of the dentin surface.

DOI： 10.4012/dmj.2021-278

PubMed

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/adbi.202101315

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/adbi.202101315

Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.colsurfb.2021.112283

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Publishing type：Research paper (scientific journal)   Publisher：Japan Prosthodontic Society  

DOI： 10.2186/jpr.jpr_d_21_00238

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

Resin composite is widely used in the dental field in clinics as a biomaterial. For example, it has been used as a composite material, a type of biomaterial, to repair caries and restore masticatory function, and as a luting agent to adhere the restoration to the tooth substrate. In order to demonstrate its function, we have measured the mechanical strength. From such basic research, we explain the potential of a dental material through the measurement of flexural strength and modulus of elasticity. In this research, we introduce commercial products that are actually used as composite materials suitable for tooth substrate and provide readers with their properties based on flexural strength and modulus of elasticity. In clinical performance, it might be advisable to delay polishing when a composite material is used for a luting material, a filling material and a core build-up material, as the flexural strength and the flexural modulus of elasticity were improved after 1 day of storage, and flexural strength and characteristics are considered as important mechanical properties of oral biomaterials.</p>

DOI： 10.3390/jcs5100282

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：English   Publishing type：Research paper (scientific journal)  

To evaluate the flexural and bonding properties, marginal adaptation, and polymerization shrinkage in flowable composite restorations and their relationships, four new generation flowable composites, one conventional, and one bulk-fill flowable composite were used in this study. Flexural properties of the composites and shear bond strength to enamel and dentin for flowable restorations were measured immediately and 24 h after polymerization. Marginal adaptation, polymerization shrinkage, and stress were also investigated immediately after polymerization. The flexural properties, and bond strength of the flowable composites to enamel and dentin were much lower immediately after polymerization than at 24 h, regardless of the type of the composite. Polymerization shrinkage and stress varied depending on the material, and bulk-fill flowable composite showed much lower values than the others. The marginal adaptation and polymerization shrinkage of the composites appeared to have a much stronger correlation with a shear bond strength to dentin than to enamel. The weak mechanical properties and bond strengths of flowable composites in the early stage after polymerization must be taken into account when using them in the clinic. In addition, clinicians should be aware that polymerization shrinkage of flowable composites can still lead to the formation of gaps and failure of adaptation to the cavity regardless of the type of composite.

DOI： 10.3390/polym13162613

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

A metallic solid-state adhesive for biological soft tissues was fabricated using Ti–6Al–4V alloys, and the influence of the minor β phase and the small amount of Al in the α phase are reported.

DOI： 10.1039/d1tb00919b

PubMed

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Mary Ann Liebert Inc  

DOI： 10.1089/ten.teb.2020.0352

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Other Link： https://www.liebertpub.com/doi/pdf/10.1089/ten.teb.2020.0352

Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Dental Materials and Devices  

DOI： 10.4012/dmj.2020-108

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/admi.202170033

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications  

During orofacial tissue development, the anterior and posterior regions of the Meckel’s cartilage undergo mineralization, while the middle region undergoes degeneration. Despite the interesting and particular phenomena, the mechanisms that regulate the different fates of Meckel’s cartilage, including the effects of biomechanical cues, are still unclear. Therefore, the purpose of this study was to systematically investigate the course of Meckel’s cartilage during embryonic development from a biomechanical perspective. Histomorphological and biomechanical (stiffness) changes in the Meckel’s cartilage were analyzed from embryonic day 12 to postnatal day 0. The results revealed remarkable changes in the morphology and size of chondrocytes, as well as the occurrence of chondrocyte burst in the vicinity of the mineralization site, an often-seen phenomenon preceding endochondral ossification. To understand the effect of biomechanical cues on Meckel’s cartilage fate, a mechanically tuned 3-dimensional hydrogel culture system was used. At the anterior region, a moderately soft environment (10-kPa hydrogel) promoted chondrocyte burst and ossification. On the contrary, at the middle region, a more rigid environment (40-kPa hydrogel) enhanced cartilage degradation by inducing a higher expression of MMP-1 and MMP-13. These results indicate that differences in the biomechanical properties of the surrounding environment are essential factors that distinctly guide the mineralization and degradation of Meckel’s cartilage and would be valuable tools for modulating in vitro cartilage and bone tissue engineering.

DOI： 10.1177/0022034520960118

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Other Link： http://journals.sagepub.com/doi/full-xml/10.1177/0022034520960118

DOI： 10.20944/preprints202102.0438.v1

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Vesicular and non-vesicular phospholipids were the nucleation sites in atherosclerotic calcification. Mineralization <italic>in vitro</italic> showed that LDL, PS and PC mineralized in 2 days. PS mineralized more than PC.</p>

DOI： 10.1039/d1ma00273b

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Language：English   Publishing type：Research paper (scientific journal)  

Much research has been conducted on fabricating biomimetic biomaterials in vitro. Tissue engineering approaches are often conducted by combining cells, scaffolds, and growth factors. However, the degradation rate of scaffolds is difficult to control and the degradation byproducts occasionally limit tissue regeneration. To overcome these issues, we have developed a novel system using a thermo-responsive hydrogel that forms scaffold-free, three-dimensional (3D) cell constructs with arbitrary size and morphology. 3D cell constructs prepared using bone marrow-derived stromal stem cells (BMSCs) exhibited self-organizing ability and formed bone-like tissue with endochondral ossification. Endothelial cells were then introduced into the BMSC construct and a vessel-like structure was formed within the constructs. Additionally, the bone formation ability was promoted by endothelial cells and cell constructs could be freeze-dried to improve their clinical application. A pre-treatment with specific protein protectant allowed for the fabrication of novel bone substitutes composed only of cells. This 3D cell construct technology using thermo-responsive hydrogels was then applied to other cell species. Cell constructs composed of dental pulp stem cells were fabricated, and the resulting construct regenerated pulp-like tissue within a human pulpless tooth. In this review, we demonstrate the approaches for the in vitro fabrication of bone and dental pulp-like tissue using thermo-responsive hydrogels and their potential applications.

DOI： 10.1080/14686996.2021.1945899

PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

The aims of this study were to investigate the effects of root dentin shear bond strength and pull-out force of resin core build-up materials on flexural strength immediately after setting, after one-day water storage, and after 20,000 thermocycles. Eight core build-up and three luting materials were investigated, using 10 specimens (n = 10) per subgroup. At three time periods-immediately after setting, after one-day water storage, and after 20,000 thermocycles, shear bond strengths to root dentin and pull-out forces were measured. Flexural strengths were measured using a 3-point bending test. For all core build-up and luting materials, the mean data of flexural strength, shear bond strength and pull-out force were the lowest immediately after setting. After one-day storage, almost all the materials yielded their highest results. A weak, but statistically significant, correlation was found between flexural strength and shear bond strength (r = 0.508, p = 0.0026, n = 33). As the pull-out force increased, the flexural strength of core build-up materials also increased (r = 0.398, p = 0.0218, n = 33). Multiple linear regression analyses were conducted using these three independent factors of flexural strength, pull-out force and root dentin shear bond strength, which showed this relationship: Flexural strength = 3.264 × Shear bond strength + 1.533 × Pull out force + 10.870, p = 0.002). For all the 11 core build-up and luting materials investigated immediately after setting, after one-day storage and after 20,000 thermocycles, their shear bond strengths to root dentin and pull-out forces were correlated to the flexural strength in core build-up materials. It was concluded that the flexural strength results of the core build-up material be used in research and quality control for the predictor of the shear bond strength to the root dentin and the retentive force of the post.

DOI： 10.3390/polym12122947

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Despite the fact that various reports have been discussing bone tissue regeneration, precise bone tissue manipulation, such as controlling the physical properties of the regenerated bone tissue, still remains a big challenge. Here, we focused on the teleost fish ribs showing flexible and tough mechanical properties to obtain a deeper insight into the structural and functional features of bone tissue from different species, which would be valuable for the superior design of bone-mimicking materials. Herein, we examined their compositions, microstructure, histology, and mechanical properties. The first rib of Carassius langsdorfii showed a higher Young’s modulus with a small region of chondrocyte clusters compared with other smaller ribs. In addition, highly oriented collagen fibers and osteocytes were observed in the first rib, indicating that the longest first rib would be more mature. Moreover, the layer-by-layer structure of the oriented bone collagen was observed in each rib. These microarchitectural and compositional findings of fish rib bone would give one the useful idea to reproduce such a highly flexible rib bone-like material.

DOI： 10.3390/ma13225099

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Current stem cell-based techniques for bone-like tissue synthesis require at least two to three weeks. Therefore, novel techniques to promote rapid 3D bone-like tissue synthesis in vitro are still required. In this study, we explored the concept of using cell nanofragments as a substrate material to promote rapid bone formation in vitro. The methods for cell nanofragment fabrication were ultrasonication (30 s and 3 min), non-ionic detergent (triton 0.1% and 1%), or freeze-dried powder. The results showed that ultrasonication for 3 min allowed the fabrication of homogeneous nanofragments of less than 150 nm in length, which mineralized surprisingly in just one day, faster than the fragments obtained from all other methods. Further optimization of culture conditions indicated that a concentration of 10 mM or 100 mM of β-glycerophosphate enhanced, whereas fetal bovine serum (FBS) inhibited in a concentration-dependent manner, the mineralization of the cell nanofragments. Finally, a 3D collagen-cell nanofragment-mineral complex mimicking a bone-like structure was generated in just two days by combining the cell nanofragments in collagen gel. In conclusion, sonication for three min could be applied as a novel method to fabricate cell nanofragments of less than 150 nm in length, which can be used as a material for in vitro bone tissue engineering.

DOI： 10.3390/ijms21155327

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Language：Japanese   Publisher：(公社)日本補綴歯科学会  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Dental Materials and Devices  

The mechanical properties of highly translucent partially stabilized zirconia (PSZ) need to be improved; however, improvement of mechanical properties often decreases translucency. To overcome this problem, a monoclinic ZrO2 (mZrO2)/SiO2 dispersion was prepared and applied as a coating material for PSZ. The influence of surface treatment by the mZrO2/SiO2 dispersion on the surface topography, crystallography, and mechanical properties of highly translucent PSZ was investigated in this study. Following the treatment, the mechanical strength of highly translucent PSZ improved by 170% compared with control, for the best mZrO2/SiO2 dispersion ratio and heating temperature condition, while maintaining its translucency. The proposed coating is promising for improving the mechanical properties of highly translucent PSZ.

DOI： 10.4012/dmj.2018-415

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

A variety of polymer- and ceramic-based soft-tissue adhesives have been developed as alternatives to surgical sutures, yet several disadvantages regarding the mechanical properties, biocompatibility, and handling hinder their further application particularly when applied for immobilization of implantable devices. Here, it is reported that a biocompatible and tough metal, titanium (Ti), shows instant and remarkable adhesion properties after acid treatment, demonstrated by ex vivo shear adhesion tests with mouse dermal tissues. Importantly, in vivo experiments demonstrate that the acid-treated Ti can easily and stably immobilize a device implanted in the mouse subcutaneous tissue. Collectively, the acid-treated Ti is shown as a solid-state instant adhesive material for biological soft tissues, which can have diverse applications including immobilization of body-implantable devices.

DOI： 10.1002/admi.201902089

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Publishing type：Research paper (scientific journal)   Publisher：Informa {UK} Limited  

DOI： 10.1080/08869634.2018.1488652

PubMed

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Publishing type：Research paper (scientific journal)  

This study investigated the mechanical properties, bond ability, and crystallographic forms of different sites in a highly translucent, multi-layered zirconia disk. Flexural properties, bond ability to resin cement, and phase composition were investigated at three sites of a highly translucent, multi-layered zirconia disk: incisal, middle, and cervical. Flexural strength (FS) and flexural modulus (FM) were measured with static three-point flexural test. Shear bond strength (SB) to resin cement was measured after 24 h storage (37°C). Phase composition under mechanical stress was analyzed using X-ray diffraction. Without air abrasion, FS at the incisal site yielded the lowest value and was significantly lower than the middle and cervical sites. Air abrasion lowered the FS of each site. FM at the incisal site without air abrasion showed the significantly lowest value, and air abrasion increased its FM value. At the middle and cervical sites, their FM values were higher than the incisal site but were not significantly affected by air abrasion. SB value did not show significant differences among the sites. After sintering, cubic zirconia was detected at each site. Rhombohedral phase transformation occurred after mirror polishing. In highly translucent, multi-layered zirconia which was mainly composed of cubic zirconia, rhombohedral phase transformation occurred under mechanical stress and resulted in weakened mechanical properties.

DOI： 10.1177/2280800020942717

Scopus

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Publishing type：Research paper (international conference proceedings)  

©2019 The Japan Institute of Metals and Materials In this study, we focused on the preferential orientation of the extracellular matrix (ECM) of bone, since ECM orientation has been shown to significantly affect the mechanical functions of bones. Bone analysis is in most cases based on the premise that the apatite crystallizes on the collagen template such that its c-axis is parallel with the running direction of the collagen fibril. Bone regeneration analysis has also been discussed assuming that the apatite c-axis orientation reflects collagen orientation. To understand the regeneration processes of both collagen and apatite individually, the preferential orientations of apatite and collagen in regenerated bone were simultaneously analyzed using a bone regeneration model of mouse femur with an 0.8-mm drill hole defect. The defects in mouse femur were filled with mineralized bone matrix, which shows an intact mineral density. However, the directions of orientation of the collagen and apatite deviate from the femur longitudinal axis in the regenerated bone. Moreover, electron diffraction analysis revealed that the apatite c-axis aligned along the extended axis of a collagen fibril both in regenerated and intact bones, indicating that the direction of the apatite c-axis is regulated by collagen fibril orientation even in the regenerated bone. In conclusion, the less-oriented apatite crystallite observed in the regenerated bone was shown to be formed due to the less-oriented collagen fibrils.

DOI： 10.2320/matertrans.MT-M2019341

Scopus

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/dvdy.78

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/dvdy.78

Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

In vitro synthesis of bone tissue has been paid attention in recent years; however, current methods to fabricate bone tissue are still ineffective due to some remaining gaps in the understanding of real in vivo bone formation process, and application of the knowledge in bone synthesis. Therefore, the objectives of this study were first, to perform a systematic and ultrastructural investigation of the initial mineral formation during intramembranous ossification of mouse calvaria from a material scientists' viewpoint, and to develop novel mineralization methods based on the in vivo findings. First, the very initial mineral deposition was found to occur at embryonic day E14.0 in mouse calvaria. Analysis of the initial bone formation process showed that it involved the following distinct steps: collagen secretion, matrix vesicle (MV) release, MV mineralization, MV rupture, and collagen fiber mineralization. Next, we performed in vitro mineralization experiments using MVs and hydrogel scaffolds. Intact MVs embedded in collagen gel did not mineralize, whereas, interestingly, MV nanofragments obtained by ultrasonication could promote rapid mineralization. These results indicate that mechanically ruptured MV membrane can be a promising material for in vitro bone tissue synthesis. © 2019 The Authors. journal Of Biomedical Materials Research Part A Published By Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1021-1030, 2019.

DOI： 10.1002/jbm.a.36618

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

OBJECTIVE: To assess whether a thermal annealing with a monoclinic zirconia (mZrO2) nanoparticle coating can improve the reliability of sandblasted yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and maintain its mechanical strength. METHODS: Commercially available Y-TZP (Lava Frame, 3M Dental Products) disks were sintered and surface-treated as follows: AS (as sintered, with no treatment); SB (sandblasting); SB-TA (sandblasting followed by thermal annealing at 1000 °C); and SB-mZr-TA (sandblasting followed by thermal annealing at 1000 °C with the mZrO2 nanoparticle coating). The mZrO2 nanoparticles of 21 nm in size were prepared by a hydrothermal method, and coated onto Y-TZP sintered disks as a 5 g/L ethanol dispersion. Biaxial flexural strength (S) was measured using the piston-on-three-ball test, and reliability was evaluated by the Weibull modulus (m). RESULTS: Biaxial flexural tests showed a significant increase in the strength of Group SB (SSB = 1445 ± 191 MPa) compared with Group AS (SAS = 1071 ± 112 MPa). The thermal annealing improved the reliabilities of the sandblasted Y-TZP (mSB-TA = 20.14 and mSB-mZr-TA = 21.33), as compared with Group SB (mSB = 7.77). However, the conventional thermal annealing without the mZrO2 coating caused a significant decrease in the strength of sandblasted Y-TZP (SSB-TA = 1273 ± 65 MPa). Importantly, the mZrO2 coating prevented the decrease in the strength caused by conventional thermal annealing (SSB-mZr-TA = 1379 ± 65 MPa). SIGNIFICANCE: The thermal annealing with the mZrO2 nanoparticle coating can improve the reliability of sandblasted Y-TZP and maintain its mechanical strength, which would otherwise be decreased by the conventional annealing process.

DOI： 10.1016/j.dental.2019.04.002

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：English   Publishing type：Research paper (scientific journal)  

Three-dimensional (3D) cell constructs composed only of cells and cell-secreted extracellular matrix have been attractive biomaterials for tissue engineering technology; however, controlling construct morphology and eliminating dead cells after fabrication remain a challenge. It has been hypothesized that moderate stress could shape constructs and eliminate dead cells. The purpose of this study was to establish an easily available technology for shaping 3D cell constructs and eliminating dead cells postfabrication. To achieve these objectives, spherical cell constructs composed of L-929 fibroblasts were processed using different sized syringe needles. Our results revealed that large-scale rod-shaped cell constructs could be fabricated, and that their diameters could be controlled according to the size of the syringe needle. Additionally, cell viability assays showed that >94% of cells in the rod-shaped constructs were viable, suggesting that dead cells, which have low adhesion force, were dispersed when compressive stress was applied during passage through the needle. The technology described in this study will be promising for future tissue engineering, especially for fabricating elongated tissues such as nerves and blood vessels. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 904-909, 2019.

DOI： 10.1002/jbm.a.36613

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acsabm.9b00014

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DOI： 10.3390/ijms20051097

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DOI： 10.1002/jbm.a.36455

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Language：English   Publishing type：Research paper (scientific journal)  

OBJECTIVE: To assess the influence of sandblasting conditions applied to conventional-type yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) on surface roughness, phase transformation, and biaxial flexural strength. METHODS: Commercially available Y-TZP (Lava Frame, 3M Dental Products) disks were used after sintering (specimen dimensions: 14mm in diameter and 1.2mm in thickness). The surfaces of specimens were ground, and then sandblast treatments were conducted at different pressures (0.20, 0.25, 0.30, 0.35 and 0.40MPa) and distances (1, 5, 10 and 20mm) with 50μm alumina particles. Surface roughness measurements were performed and scanning electron microscopy (SEM) images were taken for surface characterizations. Phase transformation of Y-TZP was identified by X-ray diffraction (XRD). Biaxial flexural strength was measured using the piston-on-three-ball test. RESULTS: The surface roughness increased significantly by increasing the sandblasting pressure, and microcracks were observed at high sandblasting pressure at 0.40MPa. The shortest sandblasting distance (1mm) was not effective to increase the surface roughness compared with other sandblasting distances. A tetragonal to monoclinic phase transformation was observed after grinding. The degree of the phase transformation tended to increase with sandblasting pressure, and significant effect was independent of the sandblasting distance. The biaxial flexural test showed improved mechanical strengths for the samples after sandblasting at 0.20-0.35MPa, with the maximum strength at 0.25MPa. Sandblasting at 0.40MPa decreased the strength as compared with 0.25MPa. SIGNIFICANCE: The surface roughness increased with increasing the sandblasting pressure, whereas there was an optimal sandblasting pressure range to increase biaxial flexural strength of Y-TZP.

DOI： 10.1016/j.dental.2018.11.009

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Language：Japanese   Publisher：岡山歯学会  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(公社)日本補綴歯科学会  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acsbiomaterials.7b00962

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acsbiomaterials.7b00962

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Bone is a sophisticated organic-inorganic hybrid material, whose formation involves a complex spatio-temporal sequence of events regulated by the cells. A deeper understanding of the mechanisms behind bone mineralization at different size scales, and using a multidisciplinary approach, may uncover novel pathways for the design and fabrication of functional bone tissue in vitro. The objectives of this study were first to investigate the environmental factors that prime initial mineralization using the secondary ossification center as an in vivo model, and then to apply the obtained knowledge for rapid in vitro synthesis of bone-like tissue. First, the direct and robust measurement of pH showed that femur epiphysis is alkaline (pH 8.5) at the initial mineral stage at post-natal day 6. We showed that the alkaline milieu is decisive not only for alkaline phosphatase activity, which precedes mineral formation at P6, but also for determining initial mineral precipitation and spherical morphology. Next, engineering approaches were used to synthesize bone-like tissue based on alkaline milieu and artificial chondrocyte membrane nanofragments, previously shown to be the nucleation site for mineral formation. Interestingly, mineralization using artificial cell membrane nanofragments was achieved in just 1 day. Finally, ex vivo culture of femur epiphysis in alkaline pH strongly induced chondrocyte burst, which was previously shown to be the origin of chondrocyte membrane nanofragments, and also enhanced mineral formation. Taken together, these findings not only shed more light on the microenvironmental conditions that prime initial bone formation in vivo, but they also show that alkaline milieu can be used as an important factor for enhancing methods for in vitro synthesis of bone tissue.

DOI： 10.1039/cBtb01544a

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

DOI： 10.1039/C8TB01544A

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

DOI： 10.1039/C7IB00130D

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Publishing type：Part of collection (book)   Publisher：Springer Singapore  

DOI： 10.1007/978-981-13-1002-7_22

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We investigated the possible linkage between the crystallinity and elemental ratios (Mg/Ca and Sr/Ca) of the femoral cortical bones of rats with chronic kidney disease (CKD) or diabetes mellitus (DM). The Mg/Ca and Sr/Ca ratios were measured by using the laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) technique and the crystallinity was evaluated by Raman spectroscopy on the same sample slice. The measured crystallinity varied significantly along the radial direction, reflecting the heterogeneities in the Mg/Ca ratio for the bone samples. For the endosteal cortical bone of CKD rats, the Mg/Ca ratio became higher. This is explained by the increase of the abundance of Mg in the bone, possibly due to the higher absorption efficiency of Mg in the intestine or due to the lower excretion efficiency of Mg from the kidney. For areas with a higher Mg/Ca ratio, the crystallinity of the bone was significantly more degraded than that for areas with a lower Mg/Ca ratio, suggesting that the substitution of Ca by Mg induced the deterioration of the crystallinity of hydroxyapatite (HAp). In addition, the measured Mg/Ca and Sr/Ca ratios of the bone were positively correlated with those found in serum samples. The data obtained here demonstrated that the metabolic alterations for inorganic elements caused the ionic substitutions of Ca by foreign cationic ions, and that the contents of foreign ions in the bone greatly affected the crystallinity of HAp.

DOI： 10.1039/c7an00734e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

Resin bonding to zirconia ceramics is difficult to achieve using the standard methods for conventional silica-based dental ceramics, which employ silane coupling monomers as primers. The hypothesis in this study was that a silane coupling oligomer a condensed product of silane coupling monomers would be a more suitable primer for zirconia. To prove this hypothesis, the shear bond strengths between a composite resin and zirconia were compared after applying either a silane coupling monomer or oligomer. The shear bond strength increased after applying a non-activated ethanol solution of the silane coupling oligomer compared with that achieved when applying the monomer. Thermal treatment of the zirconia at 110 degrees C after application of the silane coupling agents was essential to improve the shear bond strength between the composite resin cement and zirconia.

DOI： 10.4012/dmj.2016-334

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.actbio.2017.05.014

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Publishing type：Research paper (scientific journal)   Publisher：Public Library of Science ({PLoS})  

DOI： 10.1371/journal.pone.0176453

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Objectives. Dental ceramic surfaces are modified with silane coupling agents, such as gamma-ymethacryloxypropyl trimethoxy silane (gamma-MPTS), to improve bond strength. For bonding between lithium disilicate glass ceramic and resin cement, the objective was to investigate if 8-methacryloxyoctyl trimethoxy silane (8 -MOTS) could yield a similar performance as the widely used gamma-MPTS.
Methods. One hundred and ten lithium disilicate glass ceramic specimens were randomly divided into 11 groups (n = 10) according to pretreatment regime. All specimens were pre-treated with a different solution composed of one or a combination of these agents: 10 or 20 wt% silane coupling agent of gamma-MPTS or 8 -MOTS, followed by a hydrolysis solution of acetic acid or 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP). Each pretreated surface was luted to a stainless steel rod of 3.6 mm diameter and 2.0 mm height with resin cement. Shear bond strength between ceramic and cement was measured after 24-h storage in 37 degrees C distilled water.
Results. 8 -MOTS produced the same bonding performance as gamma-MPTS. Both silane coupling agents significantly increased the bond strength of resin cement, depending on their concentration. When activated by 10-MDP hydrolysis solution, 20 wt% concentration produced the highest values (gamma-MPTS: 24.9 +/- 5.1 MPa; 8 -MOTS: 24.6 +/- 7.4 MPa). Hydrolysis with acetic acid produced lower bond strengths than with 10-MDP.
Significance. Silane coupling pretreatment with 8 -MOTS increased the initial bond strength between lithium disilicate glass ceramic and resin cement, rendering the same bonding effect as the conventional gamma-MPTS. (C) 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2016.11.004

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Publishing type：Research paper (scientific journal)   Publisher：The Company of Biologists  

DOI： 10.1242/jcs.196907

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WICHTIG PUBLISHING  

Background: This study evaluated the surface morphology, chemical composition and adhesiveness of lithium disilicate glass ceramic after acid etching with hydrofluoric acid or phosphoric acid.
Methods: Lithium disilicate glass ceramic specimens polished by 600-grit silicon carbide paper were subjected to one or a combination of these surface treatments: airborne particle abrasion with 50-mu m alumina (AA), etching with 5% hydrofluoric acid (HF) or 36% phosphoric acid (Phos), and application of silane coupling agent (Si). Stainless steel rods of 3.6-mm diameter and 2.0-mm height were cemented onto treated ceramic surfaces with a self-adhesive resin cement (Clearfil SA Cement). Shear bond strengths between ceramic and cement were measured after 24-hour storage in 37 degrees C distilled water.
Results: SEM images of AA revealed the formation of conventional microretentive grooves, but acid etching with HF or Phos produced a porous surface. Bond strengths of AA+HF+Si (28.1 +/- 6.0 MPa), AA+Phos+Si (17.5 +/- 4.1 MPa) and HF+Si (21.0 +/- 3.0 MPa) were significantly greater than those of non-pretreated controls with Si (9.7 +/- 3.7 MPa) and without Si (4.1 +/- 2.4 MPa) (p&lt;0.05). In addition, HF etching alone (26.2 +/- 7.5 MPa) had significantly higher bond strength than AA alone (11.5 +/- 4.0 MPa) (p&lt;0.05). AA+HF, AA+Phos and HF showed cohesive failures.
Conclusions: Etching with HF or Phos yielded higher bond strength between lithium disilicate glass ceramic and self-adhesive resin cement without microcrack formation.

DOI： 10.5301/jabfm.5000303

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Simple and easy methods to evaluate swallowing are required because of the recently increased need of rehabilitation for dysphagia. "Artificial food bolus", but not "artificial food", would be a valuable tool for swallowing evaluation without considering the mastication effect which is altered according to the individual's oral condition. Thus, this study was carried out to fabricate artificial bolus resembling natural food bolus. The mechanical property and the volume change of food bolus in normal people were firstly investigated. Thirty healthy adults without dysphagia were selected and asked to chew four sample foods (rice cake, peanut, burdock, and gummy candy). The results indicated that Young's modulus of bolus before swallowing was below 150 kPa. The bolus volume before swallowing was below 400 mm(3). In addition, the saliva component ratio of each bolus was approximately 30wt%, and the average saliva viscosity of research participants was approximately 10 mPa.s. Based on the obtained data, artificial food bolus was designed and fabricated by using alginate hydrogel as a visco-elastic material and gelatin solution as a viscotic material with a ratio of 7: 3 based on weight. Consequently, the swallowing time of fabricated artificial food bolus was measured among the same participants. The results indicated the participants swallowed fabricated food bolus with similar manner reflecting their mechanical property and volume. Thus, this artificial food bolus would be a promising tool for evaluation of swallowing.

DOI： 10.1371/journal.pone.0168378

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Language：Japanese   Publisher：(一社)日本接着歯学会  

6種の接着システム[3種の処理材併用のレジンセメント;RelyX Ultimate(3M)、Resicem(Shofu)、ESTECEM(Tokuyama Dental)、2種の処理材を併用しないレジンセメント;G-Cem Cerasmart(GC)、SA Luting Plus(Kuraray Noritake Dental)、および1種のレジン配合型グラスアイオノマーセメント;Resiglass(Shofu)]を使用して硬化直後と1日後の象牙質に対する接着強さを検討、次に6種のCAD/CAM冠用レジンブロック[Lava Ultimate(3M)、Cerasmart(GC)、Shofu HC Block(Shofu)、ESTELITE BLOCK(Tokuyama Dental)、KZR-CAD HR(Yamakin)、KATANA Avencia (Kuraray Noritake Dental)]に対して1日後の被着面のサンドブラスト処理有無の影響も接着強さから検討した。その結果、象牙質に対する接着強さは、いずれのセメントも1日後の方が、硬化直後と比較して有意に高い値を示した(t-Test、p<0.05)。1日後のCAD/CAM冠用レジンブロックに対する接着強さは、4種の接着システム(Lava UltimateにScotchbond Universal Adhesive/RelyX Ultimateで接着させた場合、CerasmartにCeramic Primer II/G-Cem Cerasmartで接着させた場合、ESTELITE BLOCKにUNIVERSAL PRIMER/ESTECEMで接着させた場合、KZR-CAD HRにScotchbond Universal Adhesive/RelyX Ultimateで接着させた場合)にサンドブラスト処理することで有意に高い値を示した(t-Test、p<0.05)。しかし、それ以外の3種の接着システム(Shofu HC BlockにPorcelain Primer/Resicemで接着させた場合、Shofu HC BlockにResiglassで接着させた場合、KATANA AvenciaにClearfil Ceramic Primer/SA Luting Plusで接着させた場合)はサンドブラスト処理しても有意に高い値を示さなかった(t-Test、p>0.05)。(著者抄録)

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

Application of hydroxyapatite (HAp) nanoparticles to repair damaged enamel has attracted recent attention. In this study, HAp nanoparticles with various morphologies (spherical, short-rod, long-rod and fiber morphologies) were synthesized via chemical precipitation methods without the addition of template molecules, and the adsorption/desorption behaviors of a cationic antibacterial agent, cetylpyridinium chloride (CPC), on the HAp nanoparticles were evaluated. The adsorption of CPC on each HAp nanoparticle showed Langmuir-type adsorption, and the short-rod/long-rod HAp nanoparticles showed thermodynamically more stable adsorption of CPC than that with the spherical/fiber HAp nanoparticles. The desorption rate of CPC from the short-rod/long-rod HAp nanoparticles was slower than that of the spherical/fiber HAp nanoparticles. The HAp nanoparticles with different CPC release profiles presented here have potential applications as nanoparticulate enamel repair agents with antibacterial properties.

DOI： 10.4012/dmj.2015-420

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Biological tissues have specific cell patterns and well-organized structures which result from various organogenesis processes. Among which is branching morphogenesis which is the key developmental processes for many glandular tissues including lungs, kidney, salivary gland and liver. Many approaches were suggested to regenerate salivary gland tissue in vitro. Here, we developed a 3D culture technique to study and recapitulate the dynamic forces generated during SMG organogenesis by utilizing time lapse live imaging to monitor the cellular migration and reorganization process of both epithelium and mesenchyme cells.

DOI： 10.1109/MHS.2015.7438259

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Introduction: Salivary gland hypofunction, also known as xerostomia, occurs as a result of radiotherapy for head and neck cancer, autoimmune diseases, or aging. Xerostomia leads to oral health problems and thus affects the quality of life. Biological salivary gland tissue generated in vitro would provide an alternative mode of treatment for this disease.
Methods: To develop a novel method for modulating salivary gland tissue growth in vitro, we prepared a KP24 peptide-immobilized hydrogel sheet, wherein the peptide comprised repeating proline and lysine sequences, and evaluated the effect of this peptide on salivary gland tissue growth.
Results: We found that the KP24 peptide has the potential to enhance glandular tissue growth in vitro. This enhancement is associated with neurite outgrowth and increasing neural innervation.
Conclusion: KP24 peptide modified material would be a promising material for the modulation of salivary gland tissue growth in vitro. (C) 2016, The Japanese Society for Regenerative Medicine. Production and hosting by Elsevier B.V.

DOI： 10.1016/j.reth.2016.02.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Background
Sandblasting particles which remain on the surfaces of dental restorations are removed prior to cementation. It is probable that adhesive strength between luting material and sandblasting particle remnants might exceed that with restorative material. If that being the case, blasting particles adhere to sandblasted material surface could be instrumental to increasing adhesive strength like underlying bonding mechanism between luting material and silanized particles of tribochemical silica coating-treated surface. We hypothesize that ultrasonic cleaning of bonding surfaces, which were pretreated with sandblasting, may affect adhesive strength of a resin luting material to dental restorative materials.
Methods
We therefore observed adhesive strength of resin luting material to aluminum oxide was greater than those to zirconia ceramic and cobalt-chromium alloy beforehand. To measure the shear bond strengths of resin luting material to zirconia ceramic and cobalt-chromium alloy, forty specimens of each restorative material were prepared. Bonding surfaces were polished with silicon abrasive paper and then treated with sandblasting. For each restorative material, 40 sandblasted specimens were equally divided into two groups: ultrasonic cleaning (USC) group and non-ultrasonic cleaning (NUSC) group. After resin luting material was polymerized on bonding surface, shear test was performed to evaluate effect of ultrasonic cleaning of bonding surfaces pretreated with sandblasting on bond strength.
Results
For both zirconia ceramic and cobalt-chromium alloy, NUSC group showed significantly higher shear bond strength than USC group.
Conclusions
Ultrasonic cleaning of dental restorations after sandblasting should be avoided to retain improved bonding between these materials.

DOI： 10.1371/journal.pone.0147077

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI LTD  

Three-dimensional (3D) cell constructs are expected to provide osteoinductive materials to develop cell-based therapies for bone regeneration. The proliferation and spontaneous aggregation capability of induced pluripotent stemcells (iPSCs) thus prompted us to fabricate a scaffold-free iPSC construct as a transplantation vehicle. Embryoid bodies of mouse gingival fibroblast-derived iPSCs (GF-iPSCs) were seeded in a cell chamber with a round-bottom well made of a thermoresponsive hydrogel. Collected ball-like cell constructs were cultured in osteogenic induction medium for 30 days with gentle shaking, resulting in significant upregulation of osteogenic marker genes. The constructs consisted of an inner region of unstructured cell mass and an outer osseous tissue region that was surrounded by osteoblast progenitor-like cells. The outer osseous tissue was robustly calcified with elemental calcium and phosphorous as well as hydroxyapatite. Subcutaneous transplantation of the GF-iPSC constructs into immunodeficient mice contributed to extensive ectopic bone formation surrounded by teratoma tissue. These results suggest that mouse GF-iPSCs could facilitate the fabrication of osteoinductive scaffold-free 3D cell constructs, in which the calcified regions and surrounding osteoblasts may function as scaffolds and drivers of osteoinduction, respectively. With incorporation of technologies to inhibit teratoma formation, this system could provide a promising strategy for bone regenerative therapies.

DOI： 10.1155/2016/6240794

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Hindawi Limited  

Three-dimensional (3D) cell constructs are expected to provide osteoinductive materials to develop cell-based therapies for bone regeneration. The proliferation and spontaneous aggregation capability of induced pluripotent stem cells (iPSCs) thus prompted us to fabricate a scaffold-free iPSC construct as a transplantation vehicle. Embryoid bodies of mouse gingival fibroblast-derived iPSCs (GF-iPSCs) were seeded in a cell chamber with a round-bottom well made of a thermoresponsive hydrogel. Collected ball-like cell constructs were cultured in osteogenic induction medium for 30 days with gentle shaking, resulting in significant upregulation of osteogenic marker genes. The constructs consisted of an inner region of unstructured cell mass and an outer osseous tissue region that was surrounded by osteoblast progenitor-like cells. The outer osseous tissue was robustly calcified with elemental calcium and phosphorous as well as hydroxyapatite. Subcutaneous transplantation of the GF-iPSC constructs into immunodeficient mice contributed to extensive ectopic bone formation surrounded by teratoma tissue. These results suggest that mouse GF-iPSCs could facilitate the fabrication of osteoinductive scaffold-free 3D cell constructs, in which the calcified regions and surrounding osteoblasts may function as scaffolds and drivers of osteoinduction, respectively. With incorporation of technologies to inhibit teratoma formation, this system could provide a promising strategy for bone regenerative therapies.

DOI： 10.1155/2016/6240794

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Language：Japanese   Publisher：(一社)日本接着歯学会  

接着性レジンセメントシステムRelyX Ultimate/Scotchbond Universal Adhesive(3M)の、5種CAD/CAM冠用レジンブロック(Lava Ultimate:3M、CeraSmart:ジーシー、松風HC Block:松風、KZR-CAD HR:山本貴金属地金、KATANA Avencia:クラレノリタケデンタル)に対する接着強さに及ぼすサンドブラストおよびコジェット・サンドブラスト処理の影響を検討した。その結果、サンドブラストあるいはコジェット・サンドブラスト処理することにより、無処理と比較して全てのブロックにおいて有意に接着強さは向上した。ただし、サンドブラスト処理が有効か、コジェット・サンドブラスト処理が有効かは、それぞれのCAD/CAM冠用レジンブロックによって異なることが示された。(著者抄録)

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Language：English   Publisher：Elsevier Ltd  

Synthesised hydroxyapatite (HAp) exhibits excellent biocompatibility, making it an ideal candidate for use as a hard tissue substitute material. Nanoscale-size effects and surface phenomena impart HAp nanoparticles with unique properties compared to the conventional-sized HAp ceramics. Modification of HAp is also important for regulating its physiochemical properties. In this review, methods of HAp synthesis and modification, and various applications of HAp nanoparticles for dental and medical treatment are discussed.

DOI： 10.1016/j.jdsr.2015.03.004

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：English   Publisher：日本バイオマテリアル学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：English   Publishing type：Research paper (scientific journal)  

In vitro fabricated biological tissue would be a valuable tool to screen newly synthesized drugs or understand the tissue development process. Several studies have attempted to fabricate biological tissue in vitro. However, controlling the growth and morphology of the fabricated tissue remains a challenge. Therefore, new techniques are required to modulate tissue growth. RGD (arginine-glycine-aspartic acid), which is an integrin-binding domain of fibronectin, has been found to enhance cell adhesion and survival; it has been used to modify substrates for in vitro cell culture studies or used as tissue engineering scaffolds. In addition, this study shows novel functions of the RGD peptide, which enhances tissue growth and modulates tissue morphology in vitro. When an isolated submandibular gland (SMG) was cultured on an RGD-modified alginate hydrogel sheet, SMG growth including bud expansion and cleft formation was dramatically enhanced. Furthermore, we prepared small RGD-modified alginate beads and placed them on the growing SMG tissue. These RGD-modified beads successfully induced cleft formation at the bead position, guiding the desired SMG morphology. Thus, this RGD-modified material might be a promising tool to modulate tissue growth and morphology in vitro for biological tissue fabrication.

DOI： 10.1038/srep11468

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

The development of technologies to promote vascularization of engineered tissue would drive major developments in tissue engineering and regenerative medicine. Recently, we succeeded in fabricating three-dimensional (3D) cell constructs composed of mesenchymal stem cells (MSCs). However, the majority of cells within the constructs underwent necrosis due to a lack of nutrients and oxygen. We hypothesized that incorporation of vascular endothelial cells would improve the cell survival rate and aid in the fabrication of biomimetic bone tissues in vitro. The purpose of this study was to assess the impact of endothelial cells combined with the MSC constructs (MSC/HUVEC constructs) during short-and long-term culture. When human umbilical vein endothelial cells (HUVECs) were incorporated into the cell constructs, cell viability and growth factor production were increased after 7 days. Furthermore, HUVECs were observed to proliferate and self-organize into reticulate porous structures by interacting with the MSCs. After long-term culture, MSC/HUVEC constructs formed abundant mineralized matrices compared with those composed of MSCs alone. Transmission electron microscopy and qualitative analysis revealed that the mineralized matrices comprised porous cancellous bone-like tissues. These results demonstrate that highly biomimetic bone tissue can be fabricated in vitro by 3D MSC constructs incorporated with HUVECs.

DOI： 10.1371/journal.pone.0129266

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

Mineralization is one of the most important processes in normal bone tissue development and in disease condition. Developing a novel and standardized in vitro model system that can readily monitor both cellular dynamics and mineralization is crucial for better understanding the bone tissue development and growth. Recent studies indicated that the mechanical environment is a critical condition in mineralization. We hypothesized that hydrogel with different mechanical stiffness can provide a biomimetic mechanical environment that can modulate bone tissue growth and mineralization. A femur of mouse embryo (embryonic day 16) was embedded in agarose hydrogel (2-60 kPa) and cultured in an osteogenic medium for a week. Microcomputed tomography (mu CT) results revealed enhanced mineralization was detected in the femur head cultured in the gel condition, whereas no mineralization in the femur head cultured in the control (floating culture) condition. The mineralized region was corresponding to the region of secondary ossification center. Both histological and quantitative analyses indicated that the mineralized region of femur head cultured in 10 kPa gel condition was the highest and the mineralized area was significantly larger than that cultured in 2, 40, and 60 kPa gel condition. Immunofluorescence results indicated the enhanced mineralization caused by the higher chondrogenic differentiation at that region. This enhancement mainly relating to the mechanical forces and not to the oxygen tension was also confirmed. Since this system enhances and shortens the mineralization procedure compared with the conventional two-dimensional or three-dimensional cell culture system, this hydrogel system would be one of the unique models for better understanding the mineralized tissue development.

DOI： 10.1089/ten.tec.2014.0475

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

Mineralization is one of the most important processes in normal bone tissue development and in disease condition. Developing a novel and standardized in vitro model system that can readily monitor both cellular dynamics and mineralization is crucial for better understanding the bone tissue development and growth. Recent studies indicated that the mechanical environment is a critical condition in mineralization. We hypothesized that hydrogel with different mechanical stiffness can provide a biomimetic mechanical environment that can modulate bone tissue growth and mineralization. A femur of mouse embryo (embryonic day 16) was embedded in agarose hydrogel (2-60 kPa) and cultured in an osteogenic medium for a week. Microcomputed tomography (mu CT) results revealed enhanced mineralization was detected in the femur head cultured in the gel condition, whereas no mineralization in the femur head cultured in the control (floating culture) condition. The mineralized region was corresponding to the region of secondary ossification center. Both histological and quantitative analyses indicated that the mineralized region of femur head cultured in 10 kPa gel condition was the highest and the mineralized area was significantly larger than that cultured in 2, 40, and 60 kPa gel condition. Immunofluorescence results indicated the enhanced mineralization caused by the higher chondrogenic differentiation at that region. This enhancement mainly relating to the mechanical forces and not to the oxygen tension was also confirmed. Since this system enhances and shortens the mineralization procedure compared with the conventional two-dimensional or three-dimensional cell culture system, this hydrogel system would be one of the unique models for better understanding the mineralized tissue development.

DOI： 10.1089/ten.tec.2014.0475

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Association for Oral Biology  

Background Resoluble questions are estimated to mostly be resolved. Consequently, most of the remaining questions are those for which one has given up in looking for solutions
this may currently be the biggest problem for biological research. Therefore, for the continued advancement of biological sciences, it will be necessary to integrate current biological research with other fields, including chemistry, physics, robotics, material sciences, computer sciences, and mathematics. Highlight Integrated research will provide new insights into basic biology, as well as new technological outputs. Conclusion The newly emerging field of biodental engineering is one such example of integrated research with tremendous potential for facilitating future dental science research.

DOI： 10.1016/j.job.2015.01.002

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DOI： 10.1016/j.job.2015.01.002

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Language：Japanese   Publisher：(公社)日本補綴歯科学会  

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Language：Japanese   Publisher：(公社)日本補綴歯科学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

Encapsulation of cells in biocompatible polymers such as naturally derived hydrogels is an important technology that is used for cell therapy and tissue engineering. Herein, we introduce a simple and novel 3D-printed device to prepare hydrogel beads. The device is composed of a cylindrical tube with 1 inlet and 16 outlets. For the hydrogel solution, a low-melting-point agarose solution and sodium alginate are used. At a solution flow rate of 250 mu L/min and a stir speed of 500, 1000, or 1250 rpm, the device produced beads of diameters 50-100, 30-60, and 5-30 mu m, respectively. When the device was run at a flow rate of 500 mu L/min at the above-mentioned stir speeds, the bead diameters were 100-150, 60-90, and 30-60 mu m, respectively. Thus, this device can produce hydrogel beads of different sizes by altering the stir speed or the solution flow rate. In addition, we demonstrated that encapsulated MC3T3-E1 cells can survive and proliferate in the fabricated hydrogel when type I collagen is added to the gel solution. The simplicity of its design would make this device a valuable tool for rapid fabrication of cell encapsulated hydrogels.

DOI： 10.1089/3dp.2014.0023

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

Encapsulation of cells in biocompatible polymers such as naturally derived hydrogels is an important technology that is used for cell therapy and tissue engineering. Herein, we introduce a simple and novel 3D-printed device to prepare hydrogel beads. The device is composed of a cylindrical tube with 1 inlet and 16 outlets. For the hydrogel solution, a low-melting-point agarose solution and sodium alginate are used. At a solution flow rate of 250 mu L/min and a stir speed of 500, 1000, or 1250 rpm, the device produced beads of diameters 50-100, 30-60, and 5-30 mu m, respectively. When the device was run at a flow rate of 500 mu L/min at the above-mentioned stir speeds, the bead diameters were 100-150, 60-90, and 30-60 mu m, respectively. Thus, this device can produce hydrogel beads of different sizes by altering the stir speed or the solution flow rate. In addition, we demonstrated that encapsulated MC3T3-E1 cells can survive and proliferate in the fabricated hydrogel when type I collagen is added to the gel solution. The simplicity of its design would make this device a valuable tool for rapid fabrication of cell encapsulated hydrogels.

DOI： 10.1089/3dp.2014.0023

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Cortical bone exerts its biological properties through internal orientations of hydroxyapatite. Recently, we succeeded in fabricating three-dimensional (3D) patterns of bone matrices using fibrin gels. We hypothesized that these fibrin gels would induce cortical bone-like tissue in vivo and offer promising prospects for biomimetic materials. The purposes of this study were to assess the characteristics of osteoblastic-induced fibrin gels in vitro and evaluate whether fibrin gels with biomimetic matrices formed cortical bone-like tissue in vivo. When bone marrow stromal cell (BMSC)-containing fibrin gels were uniaxially fixed and cultured, BMSCs became aligned parallel to the fixed direction. The tensile strengths of the gels increased dramatically from 1.5 to 218 kPa after 50 days in culture. Furthermore, Fourier-transform infrared spectroscopy revealed that the fibrin gel constituents changed into those of native bone. Quantitative analyses of specific components demonstrated that the amounts of calcium and osteopontin in the gels increased with prolonged culture. After subcutaneous implantation into immunodeficient mice, cortical bone-like tissues that possessed layered structures were formed. The results indicated that 3D patterned bone matrices induced 3D patterned cortical bone formation in vivo. These biomimetic materials containing 3D patterned bone matrices are promising tools for the field of bone regenerative medicine. (C) 2014 Wiley Periodicals, Inc.

DOI： 10.1002/jbm.a.35212

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DOI： 10.1159/000442411

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DOI： 10.1002/jbmr.2502

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

Anodic oxidation is used for the surface treatment of commercial implants to improve their functional properties for clinical success. Here we conducted ultrastructural and chemical investigations into the micro- and nanostructure of the anodic oxide film of a titanium implant. The anodic oxidized layer of a Ti6Al4V alloy implant was examined ultrastructurally by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). They were also analyzed using energy dispersive X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). The TEM revealed that the oxide layer of the Ti6Al4V implant prepared through anodic oxidation was separated into two layers. Al and V were not present on the top surface of the anodic oxide. This can be attributed to the biocompatibility of the anodic oxidized Ti6Al4V alloy implant, because the release of harmful metal ions such as Al and V can be suppressed by the biocompatibility.

DOI： 10.4012/dmj.2014-121

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：English   Publisher：日本バイオマテリアル学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

Induced pluripotent stem cells (iPSCs) can differentiate into mineralizing cells and are, therefore, expected to be useful for bone regenerative medicine; however, the characteristics of iPSC-derived osteogenic cells remain unclear. Here, we provide a direct in vitro comparison of the osteogenic differentiation process in mesenchymal stem cells (MSCs) and iPSCs from adult C57BL/6J mice. After 30 days of culture in osteogenic medium, both MSCs and iPSCs produced robustly mineralized bone nodules that contained abundant calcium phosphate with hydroxyapatite crystal formation. Mineral deposition was significantly higher in iPSC cultures than in MSC cultures. Scanning electron microscopy revealed budding matrix vesicles in early osteogenic iPSCs; subsequently, the vesicles propagated to exhibit robust mineralization without rich fibrous structures. Early osteogenic MSCs showed deposition of many matrix vesicles in abundant collagen fibrils that became solid mineralized structures. Both cell types demonstrated increased expression of osteogenic marker genes, such as runx2, osterix, dlx5, bone sialoprotein (BSP), and osteocalcin, during osteogenesis; however, real-time reverse transcription-polymerase chain reaction array analysis revealed that osteogenesis-related genes encoding mineralization-associated molecules, bone morphogenetic proteins, and extracellular matrix collagens were differentially expressed between iPSCs and MSCs. These data suggest that iPSCs are capable of differentiation into mature osteoblasts whose associated hydroxyapatite has a crystal structure similar to that of MSC-associated hydroxyapatite; however, the transcriptional differences between iPSCs and MSCs could result in differences in the mineral and matrix environments of the bone nodules. Determining the biological mechanisms underlying cell-specific differences in mineralization during in vitro iPSC osteogenesis may facilitate the development of clinically effective engineered bone.

DOI： 10.1089/scd.2013.0344

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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コンポジットレジンシステム(以後CRSと表記)における初期硬化頃の歯質接着強さの推移を詳細に把握するため、光照射直後から24時間後までのエナメル質および象牙質に対する接着強さを測定した。材料は、市販の9種のCRS[QuiXX+Xeno IV(Dentsply/Caulk)、Filtek P-60+Adper Prompt L-Pop(3M ESPE)、Herculite XRV+OptiBond All-in-One(Kerr)、Tetric N-Ceram+AdheSE One VivaPen(Ivoclar Vivadent)、Solare P+G-Bond(GC)、BEAUTIFIL II+BeautiBond(Shofu)、Metafil AP+Brush & Bond(SunMedical)、Estelite P quick+Tokuyama Bond Force(Tokuyama Dental)、Clearfil Majesty Posterior+Clearfil tri-S Bond(Kuraray Noritake Dental)]を用いた。方法として、エナメル質および象牙質に対するせん断接着強さを、光照射直後、10分間、30分間、1時間、6時間、12時間および24時間37℃蒸留水中に浸漬後、測定した。その結果、エナメル質では、光照射直後の接着強さ(8.0-14.6 MPa)は、24時間後(13.6-21.8 MPa)の51-86%を示し、光照射直後と比較して、10分後では3種のCRSが、6時間後では3種のCRSにおいてそれぞれ有意に接着強さが向上した。象牙質では、光照射直後の接着強さ(7.8-13.3 MPa)は、24時間後(11.0-23.3 MPa)の54-73%を示し、光照射直後の接着強さと比較して、1時間後では1種のCRSが、6時間後では7種のCRSにおいてそれぞれ有意に接着強さが向上した。よって、CRSの歯質接着強さは、光照射直後からほぼ24時間後まで経時的に徐々に向上することが示された。(著者抄録)

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Publishing type：Research paper (scientific journal)   Publisher：IEEE  

DOI： 10.1109/MHS.2014.7006080

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Language：English   Publisher：The Biophysical Society of Japan General Incorporated Association  

DOI： 10.2142/biophys.54.S170_2

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(一社)日本接着歯学会  

6種の合着用レジン添加型グラスアイオノマーセメント[RMGICs:RelyX Luting Plus AutomixとVitremer Paste(両者3M ESPE)、Fuji Luting EXとFuji Luting S(両者GC)、SI-R21202とResiGlass Paste(両者松風)]の合着材としての有用性を検討する一環として、歯質、ジルコニア(Lava、3M ESPE)、金合金(GC's Casting Gold Type III M.C.、GC)や金銀パラジウム合金(CastWell M.C.12%Gold、GC)に対するせん断接着強さおよび曲げ特性(強さと弾性率)を硬化直後、1時間水中浸漬後、1日間水中浸漬後およびサーマルサイクル10,000回負荷(TC 10k)後に測定した。その結果、1時間水中浸漬後のRMGICの様々な接着強さは、硬化直後より有意に高く、1日間水中浸漬後の歯質接着強さは1時間水中浸漬後より有意に高かった。TC 10k後では多くのRMGICがそれぞれの測定項目で、大半が有意に低下した。曲げ特性に関しても前述と類似の傾向を示した。(著者抄録)

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

The fabrication of biomimetic skeletal myocyte constructs continues to present a challenge to functional tissue engineering. The skeletal myogenesis of bone marrow-derived mesenchymal stromal cells (BMSCs) to mimic the native tissue architecture offers great therapeutic promise, but remains particularly difficult. The aim of this study was to examine the possibility of accelerating the skeletal myogenic differentiation of BMSCs with an aligned structure by applying cyclic strain. Mouse BMSCs (mBMSCs) were plated on silicone sheets that were coated with fibronectin and subjected to cyclic 10% uniaxial strain when they reached 80%-90% cell confluency. Cells cultured in a growth medium that were subjected to cyclic strain at a frequency of 0.17 Hz (10 times/min) demonstrated a shift of alignment within 48 h from a completely random orientation to a well-aligned morphology with well-organized actin stress fibers that were parallel to the strain vector. The cyclic strain restricted the motility and proliferation of the aligned mBMSCs in the growth medium, which resulted in tight cellular contact in the cell population. When mBMSCs were subjected to cyclic strain in a myogenic medium, reverse transcription-polymerase chain reaction analysis demonstrated the upregulation of skeletal myogenic marker genes (myogenic factor 5 [Myf5], myogenin, and myogenic regulatory factor 4 [MRF4]), but not smooth muscle marker genes (myocardin and a-smooth muscle actin). In addition, immunocytochemistry showed that the mBMSCs fused to form multinucleated myosin-and myogenin-positive myotubes in the direction of the applied tension within 5 days. These results demonstrate that our simple method of applying of cyclic strain to cells cultured in a myogenic medium greatly accelerates the skeletal myogenic differentiation of mBMSCs with an aligned structure, and they highlight the importance of cellular alignment for creating physiologically relevant environments to study the myogenesis of BMSCs and engineer skeletal muscle.

DOI： 10.1089/ten.tea.2012.0164

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

The fabrication of biomimetic skeletal myocyte constructs continues to present a challenge to functional tissue engineering. The skeletal myogenesis of bone marrow-derived mesenchymal stromal cells (BMSCs) to mimic the native tissue architecture offers great therapeutic promise, but remains particularly difficult. The aim of this study was to examine the possibility of accelerating the skeletal myogenic differentiation of BMSCs with an aligned structure by applying cyclic strain. Mouse BMSCs (mBMSCs) were plated on silicone sheets that were coated with fibronectin and subjected to cyclic 10% uniaxial strain when they reached 80%-90% cell confluency. Cells cultured in a growth medium that were subjected to cyclic strain at a frequency of 0.17 Hz (10 times/min) demonstrated a shift of alignment within 48 h from a completely random orientation to a well-aligned morphology with well-organized actin stress fibers that were parallel to the strain vector. The cyclic strain restricted the motility and proliferation of the aligned mBMSCs in the growth medium, which resulted in tight cellular contact in the cell population. When mBMSCs were subjected to cyclic strain in a myogenic medium, reverse transcription-polymerase chain reaction analysis demonstrated the upregulation of skeletal myogenic marker genes (myogenic factor 5 [Myf5], myogenin, and myogenic regulatory factor 4 [MRF4]), but not smooth muscle marker genes (myocardin and a-smooth muscle actin). In addition, immunocytochemistry showed that the mBMSCs fused to form multinucleated myosin-and myogenin-positive myotubes in the direction of the applied tension within 5 days. These results demonstrate that our simple method of applying of cyclic strain to cells cultured in a myogenic medium greatly accelerates the skeletal myogenic differentiation of mBMSCs with an aligned structure, and they highlight the importance of cellular alignment for creating physiologically relevant environments to study the myogenesis of BMSCs and engineer skeletal muscle.

DOI： 10.1089/ten.tea.2012.0164

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

A biodegradable material that bonds to hard tissues such as bones and teeth is urgently needed for medical and dental applications. However, such materials are not available in today's clinical practice of orthopedics and dentistry. Therefore, we synthesized biodegradable phosphorylated pullulan to develop a biomaterial that combines primary properties such as high biocompatibility, good bonding potential to hard tissue, high strength, biodegradability, and osteoconductivity. The pharmacopoeial polysaccharide pullulan was chemically functionalized with dihydrogen phosphate groups. Phosphorylated pullulan was formed network by adding calcium ion, making the composite less soluble in water. Adhesive force measurement revealed that adhesiveness of the pastes before setting can be controlled through optimization of additives. In addition, histological evaluation revealed that phosphorylated pullulan-based composite possesses high biocompatibility. These results indicate that phosphorylated pullulan can be used as a key material for regeneration and reconstruction of bone and tooth.

DOI： 10.4028/www.scientific.net/KEM.529-530.516

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Anodization is an easily viable technique useful for producing TiO2 coatings on titanium substrates. Nanocrystalline anodic TiO2 structure was produced on titanium at 20 V using 1 M Na2SO4 and 0.5% NaF and consolidated by a further heat-treatment. Micro-crystalline anodic TiO2 was produced on titanium by applying a galvanostatic current density of 70 A/m(2) in water medium. To assess the usefulness of these nano- and micro-oxides for bone implant stability, physical properties and bone in vitro bioactivity including HA formation, cellular affinity and mouse-tissue morphogenesis, were evaluated. Bioactivity of the different anodic surfaces was evaluated by treating them in a simulated body fluid (SBF) to form hydroxyapatite (HA) and the rates of HA formation were compared. Deposits of HA could be seen on the nano-oxide surface within 7 days, whereas HA was detected only after 14 days on the micro-oxide surface. In vitro cell culture tests done using mouse osteoblasts indicated that the nano-oxides showed statistically significant cell activity than the micro-oxides and the machined titanium. Branching morphogenesis test done for 72 h on these surfaces showed more branching on the micro- and nano-oxides as compared with titanium surface. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msec.2012.07.034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Objective. Highly porous apatite-based bioceramic scaffolds have been widely investigated as three-dimensional (3D) templates for cell adhesion, proliferation, and differentiation promoting the bone regeneration. Their fragility, however, limits their clinical application especially for a large bone defect.
Methods. To address the hypothesis that using a ZrO2/hydroxyapatite (HAp) composite might improve both the mechanical properties and cellular compatibility of the porous material, we fabricated ZrO2/HAp composite scaffolds with different ZrO2/HAp ratios, and evaluated their characteristics. In addition, porous ZrO2/HAp scaffolds containing bone marrow derived stromal cells (BMSCs) were implanted into critical-size bone defects for 6 weeks in order to evaluate the bone tissue reconstruction with this material.
Results. The porosity of a ZrO2/HAp scaffold can be adjusted from 72% to 91%, and the compressive strength of the scaffold increased from 2.5 to 13.8 MPa when the ZrO2 content increased from 50 to 100 wt%. The cell adhesion and proliferation in the ZrO2/HAp scaffold was greatly improved when compared to the scaffold made with ZrO2 alone. Moreover, in vivo study showed that a BMSCs-loaded ZrO2/HAp scaffold provided a suitable 3D environment for BMSC survival and enhanced bone regeneration around the implanted material.
Significance. We thus showed that a porous ZrO2/HAp composite scaffold has excellent mechanical properties, and cellular/tissue compatibility, and would be a promising substrate to achieve both bone reconstruction and regeneration needed in the treatment of large bone defects. (C) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2012.09.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Anodization is an easily viable technique useful for producing TiO2 coatings on titanium substrates. Nanocrystalline anodic TiO2 structure was produced on titanium at 20 V using 1 M Na2SO4 and 0.5% NaF and consolidated by a further heat-treatment. Micro-crystalline anodic TiO2 was produced on titanium by applying a galvanostatic current density of 70 A/m(2) in water medium. To assess the usefulness of these nano- and micro-oxides for bone implant stability, physical properties and bone in vitro bioactivity including HA formation, cellular affinity and mouse-tissue morphogenesis, were evaluated. Bioactivity of the different anodic surfaces was evaluated by treating them in a simulated body fluid (SBF) to form hydroxyapatite (HA) and the rates of HA formation were compared. Deposits of HA could be seen on the nano-oxide surface within 7 days, whereas HA was detected only after 14 days on the micro-oxide surface. In vitro cell culture tests done using mouse osteoblasts indicated that the nano-oxides showed statistically significant cell activity than the micro-oxides and the machined titanium. Branching morphogenesis test done for 72 h on these surfaces showed more branching on the micro- and nano-oxides as compared with titanium surface. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msec.2012.07.034

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Language：Japanese   Publisher：(一社)日本接着歯学会  

5種の合着用レジン添加型グラスアイオノマーセメント[RMGICs:Fuji Luting EX、Fuji Luting S(ジーシー)、RelyX Luting Plus Automix、Vitremer Paste(スリーエム・エスペ)、ResiGlass Paste(松風)]の歯質接着性と曲げ特性を測定、レジンセメント[SA Luting(クラレノリタケ・デンタル)]と比較した。エナメル質と象牙質に対するせん断接着強さと曲げ強さと曲げ弾性率を、初期硬化、1時間水中浸漬後および1日間水中浸漬後測定した。1時間水中浸漬後のRMGICsとレジンセメントの歯質接着強さは、初期硬化より有意に高く、1日間水中浸漬後の歯質接着強さは1時間水中浸漬後より有意に高かった。曲げ特性に関しては類似の傾向を示したが、レジンセメントはRMGICsと比較して有意に高い値を示した。RMGICsのエナメル質と象牙質に対する接着強さと曲げ特性はそれぞれ有意な正の関係にあった。(著者抄録)

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS INC  

Previous research showed that the functional monomer 10-methacryloxydecyl dihydrogen phosphate (MDP) ionically bonds to hydroxyapatite (HAp) and forms a nano-layered structure at the interface with HAp-based substrates. Such hydrophobic nano-layering is considered to contribute to the long-term durability of the bond to tooth tissue. However, dental adhesives are complex mixtures usually containing different monomers. This study investigated the effect of the monomer 2-hydroxyethylmethacrylate (HEMA) on the chemical interaction of MDP with HAp by x-ray diffraction (XRD), nuclear magnetic resonance (NMR), and quartz crystal microbalance (QCM). We examined the chemical interaction of 5 experimental MDP solutions with increasing concentrations of HEMA. XRD revealed that addition of HEMA inhibits nano-layering at the interface, while NMR confirmed that MDP remained adsorbed onto the HAp surface. QCM confirmed this adsorption of MDP to HAp, as well as revealed that the demineralization rate of HAp by MDP was reduced by HEMA. It was concluded that even though the adsorption of MDP to HAp was not hindered, addition of HEMA inhibited interfacial nano-layering. Potential consequences with regard to bond durability necessitate further research.

DOI： 10.1177/0022034512460396

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Language：Japanese   Publisher：(一社)日本接着歯学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

Titanium has an osseointegrative property, while hydroxyapatite has an osteoconductive property. It remains a matter of controversy among researchers whether hydroxyapatite has higher osteoblast compatibility than titanium. Here, we compared the activities between osteoblasts cultured on titanium and those cultured on hydroxyapatite. An osteoblast-like cell line, MC3T3-E1, was cultured on machined titanium, evaporated titanium, and hydroxyapatite disks to compare the affinity of osteoblasts to each of these materials. The adhesion and proliferation of MC3T3-E1 cells were higher on hydroxyapatite disks than on the other disks. Osteoblast differentiation was not affected by the nature of disks investigated, but calcium was more easily deposited on the hydroxyapatite disks. The amount of absorbed serum proteins detected on hydroxyapatite was greater than that on titanium. In conclusion, our results indicate hydroxyapatite is a more suitable material for osteoblast growth than titanium because of its higher absorption of serum proteins.

DOI： 10.4012/dmj.2012-075

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

According to the 'Adhesion-Decalcification' concept, specific functional monomers within dental adhesives can ionically interact with hydroxyapatite (HAp). Some specific functional monomers form monomer-Ca salts due to chemical interactions. The chemical stability of the monomer-Ca salts was thought to contribute to bond durability. In the present study, we analyzed the chemical interaction between an acidic three-dimensional self-reinforcing monomer (3D-SR) of Bond Force and enamel, dentin and HAp, and assessed its chemical stability by thin-film X-ray diffraction (TF-XRD). 3D-SR forms a hydrolysis-resistant Ca-salt on the dentin in a clinical application time period and on enamel and HAp in a longer time period. This suggests that the functional monomer 3D-SR is able to contribute to bond durability.

DOI： 10.4012/dmj.2012-074

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

Titanium has an osseointegrative property, while hydroxyapatite has an osteoconductive property. It remains a matter of controversy among researchers whether hydroxyapatite has higher osteoblast compatibility than titanium. Here, we compared the activities between osteoblasts cultured on titanium and those cultured on hydroxyapatite. An osteoblast-like cell line, MC3T3-E1, was cultured on machined titanium, evaporated titanium, and hydroxyapatite disks to compare the affinity of osteoblasts to each of these materials. The adhesion and proliferation of MC3T3-E1 cells were higher on hydroxyapatite disks than on the other disks. Osteoblast differentiation was not affected by the nature of disks investigated, but calcium was more easily deposited on the hydroxyapatite disks. The amount of absorbed serum proteins detected on hydroxyapatite was greater than that on titanium. In conclusion, our results indicate hydroxyapatite is a more suitable material for osteoblast growth than titanium because of its higher absorption of serum proteins.

DOI： 10.4012/dmj.2012-075

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Titanium and its alloys are used as implant materials in dental and orthopaedic applications. The material affinities to host bone tissue greatly concern with the recovery period and good prognosis. To obtain a material surface having excellent affinity to bone, acid etching prior to alkali- and heat-treatment of Ti was conducted. The surface characteristics of the prepared sample indicated that the roughness as well as the wettability increased by pre-etching. Bone-like apatite was formed on pre-etched, alkali- and heat-treated Ti surface in simulated body fluid (SBF) within 3 days, while it takes 5 days on the solely alkali- and heat-treated surface. Osteoblastic cells showed better compatibility on the per-etched surface compared to the pure Ti surface or alkali- and heat-treated surface. Moreover, the pre-etched surface showed better pull-off tensile adhesion strength against the deposited apatite. Thus, acid etching prior to alkali- and heat-treatment would be a promising method for enhancing the affinity of Ti to host bone tissue. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2011.12.119

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Endochondral ossification is one of the essential bone development processes in vertebrates. Although researchers from a variety of fields, including cellular/molecular biology, chemistry, and materials science, have worked to gain a better understanding of the tissue development, integration of findings from these different fields remains a major challenge. An in vitro model system that reproduces endochondral ossification would be a valuable tool for overcoming this problem, because an in vitro standardized model system can be easily accessed by researchers from different fields. Here, we fabricated a large 3D mesenchymal stem cell (MSC) construct with a ball-like morphology, which is termed a cell ball, and cultured it under a hypoxia condition, since hypoxia causes chondrogenic differentiation of MSCs in primordial cartilage, which is crucial for endochondral ossification. Region-specific chondrogenic differentiation of MSCs and mineralization within the cartilage tissue were observed in the cell ball. The precipitated minerals were detected as hydroxyapatite. Consequently, a 3D construct consisting of mineralized tissue surrounded by cartilage tissue was obtained. Moreover, the angiogenic activity of this synthesized tissue changed depending on the chondrogenic phenotype remains in the tissue, which is similar to what happens in the ossification process. Thus, this MSC cell ball system clearly reproduced the initial stage of endochondral ossification in vitro. This system is a promising tool for use as an in vitro model for investigating bone tissue development.

DOI： 10.1039/c2ib20027a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Objectives. Titanium plates and apatite blocks are commonly used for restoring large osseous defects in dental and orthopedic surgery. However, several cases of allergies against titanium have been recently reported. Also, sintered apatite block does not possess sufficient mechanical strength. In this study, we attempted to fabricate a composite material that has mechanical properties similar to biocortical bone and high bioaffinity by compounding hydroxyapatite (HAp) with the base material zirconia (ZrO2), which possesses high mechanical properties and low toxicity toward living organisms.
Methods. After mixing the raw material powders at several different ZrO2/HAp mixing ratios, the material was compressed in a metal mold (8 mm in diameter) at 5 MPa. Subsequently, it was sintered for 5 h at 1500 degrees C to obtain the ZrO2/HAp composite. The mechanical property and biocompatibility of materials were investigated. Furthermore, osteoconductivity of materials was investigated by animal studies.
Results. A composite material with a minute porous structure was successfully created using ZrO2/HAp powders, having different particle sizes, as the starting material. The material also showed high protein adsorption and a favorable cellular affinity. When the mixing ratio was ZrO2/HAp = 70/30, the strength was equal to cortical bone. Furthermore, in vivo experiments confirmed its high osteoconductivity.
Significance. The composite material had strength similar to biocortical bones with high cell and tissue affinities by compounding ZrO2 and HAp. The ZrO2/HAp composite material having micro porous structure would be a promising bone restorative material. (C) 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2011.07.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Objectives. Titanium plates and apatite blocks are commonly used for restoring large osseous defects in dental and orthopedic surgery. However, several cases of allergies against titanium have been recently reported. Also, sintered apatite block does not possess sufficient mechanical strength. In this study, we attempted to fabricate a composite material that has mechanical properties similar to biocortical bone and high bioaffinity by compounding hydroxyapatite (HAp) with the base material zirconia (ZrO2), which possesses high mechanical properties and low toxicity toward living organisms.
Methods. After mixing the raw material powders at several different ZrO2/HAp mixing ratios, the material was compressed in a metal mold (8 mm in diameter) at 5 MPa. Subsequently, it was sintered for 5 h at 1500 degrees C to obtain the ZrO2/HAp composite. The mechanical property and biocompatibility of materials were investigated. Furthermore, osteoconductivity of materials was investigated by animal studies.
Results. A composite material with a minute porous structure was successfully created using ZrO2/HAp powders, having different particle sizes, as the starting material. The material also showed high protein adsorption and a favorable cellular affinity. When the mixing ratio was ZrO2/HAp = 70/30, the strength was equal to cortical bone. Furthermore, in vivo experiments confirmed its high osteoconductivity.
Significance. The composite material had strength similar to biocortical bones with high cell and tissue affinities by compounding ZrO2 and HAp. The ZrO2/HAp composite material having micro porous structure would be a promising bone restorative material. (C) 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2011.07.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The mechanical properties of the cellular microenvironment dramatically alter during tissue development and growth. Growing evidence suggests that physical microenvironments and mechanical stresses direct cell fate in developing tissue. However, how these physical cues affect the tissue morphogenesis remains a major unknown. We explain here that the physical properties of the cell and tissue microenvironment, biomimetically reproduced by using hydrogel, guide the tissue morphogenesis in the developmental submandibular gland (SMG). In particular, the softer gel enhances the bud expansion and cleft formation of SMG, whereas the stiffer gel attenuates them. These morphological changes in SMG tissue are led by soluble factors (FGF7/10) induction regulated by cell traction force derived from the tissue deformation. Our findings suggest that cells sense the mechanics of their surrounding environment and alter their properties for self-organization and the following tissue morphogenesis. Also, physically designed hydrogel material is a valuable tool for producing the biomimetic microenvironment to explore how physical cues affect tissue morphogenesis and to modulate tissue morphogenesis for in vitro tissue synthesis. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biomaterials.2011.05.072

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SCIENTIFIC PUBLISHERS  

Anodic TiO(2) nanotubes were produced on titanium at 20 V using 1 M Na(2)SO(4) and 0.5 wt% NaF. Oxidation for 3 hours produced amorphous tubes of diameter 100 nm and thicknesses 2 mu m. Heat-treatments were done for 3 hours at different temperatures. 300 degrees C treatment converted the amorphous coatings to anatase. 550 and 700 degrees C treatments formed dual anatase and rutile; 850 degrees C treatment crystallized to rutile. The treatment at 700 degrees C produced an oxide surface with higher roughness, lower wetting angle and higher coating adhesion. Bioactivity of the as-oxidized and heated coatings were evaluated by treating them in a simulated body fluid (SBF) to form hydroxyapatite (HA) and the rates of HA formation were compared. Deposits of HA could be seen on the dual oxide structure within 3 days. HA was detected after 7 days in the anatase structure and only after 21 days in the amorphous and rutile structures. In vitro cell culture tests done using mouse osteoblasts indicated that, the 700 degrees C-heated surface showed higher levels of cell activity than the other surfaces. It is concluded that the dual rutile and anatase structure formed by heating the oxide at 700 degrees C is the best of the five surfaces tested.

DOI： 10.1166/jnn.2011.4114

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Biomaterials containing components similar to the native biological tissue would have benefits as an implantable scaffold material. To obtain such biomimetic materials, cells may be great contributors because of their crucial roles in synthetic organics. In addition, the synthesized organics-especially those derived from osteogenic differentiated cells-become a place where mineral crystals nucleate and grow even in vitro. Therefore, to fabricate an organic/inorganic composite material, which is similar to the biological osteoid tissue, bone marrow derived mesenchymal stem cells (BMSCs) were cultured in a 3D fibrin gel in this study. BMSCs secreted bone-related proteins that enhanced the biomineralization within the gel when the cells were cultured with an osteogenic differentiation medium. The compositions of both synthesized matrices and precipitated minerals in the obtained materials altered depending on the cell culture period. The mineral obtained in the 3D gel showed low crystalline hydroxyapatite. The composite materials also showed excellent osteoconductivity with new bone formation when implanted in mice tibiae. Thus, we demonstrated the contributions of cells for fabricating implantable organic/inorganic composite gel materials and a method for controlling the material composition in the gel. This cell-based material fabrication method would be a novel method to fabricate organic/inorganic composite biomimetic materials for bone tissue engineering.

DOI： 10.3390/ma4010327

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DOI： 10.1016/j.matchemphys.2011.03.045

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Background: Induced pluripotent stem (iPS) cells efficiently generated from accessible tissues have the potential for clinical applications. Oral gingiva, which is often resected during general dental treatments and treated as biomedical waste, is an easily obtainable tissue, and cells can be isolated from patients with minimal discomfort.
Methodology/Principal Findings: We herein demonstrate iPS cell generation from adult wild-type mouse gingival fibroblasts (GFs) via introduction of four factors (Oct3/4, Sox2, Klf4 and c-Myc; GF-iPS-4F cells) or three factors (the same as GF-iPS-4F cells, but without the c-Myc oncogene; GF-iPS-3F cells) without drug selection. iPS cells were also generated from primary human gingival fibroblasts via four-factor transduction. These cells exhibited the morphology and growth properties of embryonic stem (ES) cells and expressed ES cell marker genes, with a decreased CpG methylation ratio in promoter regions of Nanog and Oct3/4. Additionally, teratoma formation assays showed ES cell-like derivation of cells and tissues representative of all three germ layers. In comparison to mouse GF-iPS-4F cells, GF-iPS-3F cells showed consistently more ES cell-like characteristics in terms of DNA methylation status and gene expression, although the reprogramming process was substantially delayed and the overall efficiency was also reduced. When transplanted into blastocysts, GF-iPS-3F cells gave rise to chimeras and contributed to the development of the germline. Notably, the four-factor reprogramming efficiency of mouse GFs was more than 7-fold higher than that of fibroblasts from tail-tips, possibly because of their high proliferative capacity.
Conclusions/Significance: These results suggest that GFs from the easily obtainable gingival tissues can be readily reprogrammed into iPS cells, thus making them a promising cell source for investigating the basis of cellular reprogramming and pluripotency for future clinical applications. In addition, high-quality iPS cells were generated from mouse GFs without Myc transduction or a specific system for reprogrammed cell selection.

DOI： 10.1371/journal.pone.0012743

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

A morphologically controlled three-dimensional (3D) cell construct composed of only cells and having no scaffold material might be a valuable biologic material for tissue engineering applications, as the scaffold materials can cause delay of tissue regeneration in some conditions. To obtain such a 3D cell construct, a 3D thermoresponsive hydrogel (poly-N-isopropylacrylamide) was prepared as a mold material that changes its volume depending on the temperature. Three-dimensional osteoblast cell constructs with a variety of morphologies as well as a monolayered cell sheet were obtained by decreasing the surrounding temperature of the hydrogel designed with a predefined shape and formed by curing in a polymer mold manufactured via 3D printing. The cell sheet or 3D cell constructs detachment resulted from a simple change in the gel volume, not by the surface chemistry of the gel, because the surface hydrophilicity of the gel was maintained over a wide temperature range. These 2D/3D cell constructs have numbers of exciting applications such as cell carriers for tissue regeneration or as model tissues for the biological study.

DOI： 10.1089/ten.tea.2009.0523

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT INC  

Apatite biomaterials have potential not only as cell vehicles for engineering bone tissue but also as regulators of calcium (Ca) concentration in situ for controlling osteoblast functions, for example, osteogenic differentiation and fate management of hematopoietic stem cells (HSCs). To design apatite materials having optimal chemical properties for the latter purpose, more detailed investigations into what effect Ca concentrations have on osteoblast functions is crucial. In this study, osteoblasts were cultured at different Ca concentrations, and the temporal alterations in osteogenic differentiation and HSC niche-related protein (angiopoietin-1, 2 [Ang1, 2]) expression were investigated. The different Ca concentrations (1.8-50 mmol/L) in the cell culture medium had no effect on the proliferation of osteoblasts, but did on the cell morphology. The higher Ca concentrations (&lt;6 mmol/L) enhanced the mineralization as well as Ang1 expression. In addition, Ang1 expression in osteoblasts showed higher correlation with expression of connexin43, the major marker of cell-cell interactions, whereas Ang2 related to integrin beta 1, the major marker of cell-matrix interactions. Thus, the local Ca concentration regulates cell morphology through the cell-cell or cell-matrix interactions, leading to the alteration of Ang1 expression in osteoblasts. Since these changes triggered by Ca are concerned with the osteogenic differentiation or reproduction of HSCs niche microenvironment, the results obtained in this study might be useful for designing apatite materials with optimal chemical properties.

DOI： 10.1089/ten.tea.2009.0337

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT INC  

Apatite biomaterials have potential not only as cell vehicles for engineering bone tissue but also as regulators of calcium (Ca) concentration in situ for controlling osteoblast functions, for example, osteogenic differentiation and fate management of hematopoietic stem cells (HSCs). To design apatite materials having optimal chemical properties for the latter purpose, more detailed investigations into what effect Ca concentrations have on osteoblast functions is crucial. In this study, osteoblasts were cultured at different Ca concentrations, and the temporal alterations in osteogenic differentiation and HSC niche-related protein (angiopoietin-1, 2 [Ang1, 2]) expression were investigated. The different Ca concentrations (1.8-50 mmol/L) in the cell culture medium had no effect on the proliferation of osteoblasts, but did on the cell morphology. The higher Ca concentrations (&lt;6 mmol/L) enhanced the mineralization as well as Ang1 expression. In addition, Ang1 expression in osteoblasts showed higher correlation with expression of connexin43, the major marker of cell-cell interactions, whereas Ang2 related to integrin beta 1, the major marker of cell-matrix interactions. Thus, the local Ca concentration regulates cell morphology through the cell-cell or cell-matrix interactions, leading to the alteration of Ang1 expression in osteoblasts. Since these changes triggered by Ca are concerned with the osteogenic differentiation or reproduction of HSCs niche microenvironment, the results obtained in this study might be useful for designing apatite materials with optimal chemical properties.

DOI： 10.1089/ten.tea.2009.0337

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

A morphologically controlled three-dimensional (3D) cell construct composed of only cells and having no scaffold material might be a valuable biologic material for tissue engineering applications, as the scaffold materials can cause delay of tissue regeneration in some conditions. To obtain such a 3D cell construct, a 3D thermoresponsive hydrogel (poly-N-isopropylacrylamide) was prepared as a mold material that changes its volume depending on the temperature. Three-dimensional osteoblast cell constructs with a variety of morphologies as well as a monolayered cell sheet were obtained by decreasing the surrounding temperature of the hydrogel designed with a predefined shape and formed by curing in a polymer mold manufactured via 3D printing. The cell sheet or 3D cell constructs detachment resulted from a simple change in the gel volume, not by the surface chemistry of the gel, because the surface hydrophilicity of the gel was maintained over a wide temperature range. These 2D/3D cell constructs have numbers of exciting applications such as cell carriers for tissue regeneration or as model tissues for the biological study.

DOI： 10.1089/ten.tea.2009.0523

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS INC  

Physico-chemical modifications of hydroxyapatite (HAp) materials are considered as pre-requisites for the development of new bioactive carrier materials for drug delivery and tissue engineering applications. Since acidic amino acids have well-documented affinities to both HAp and basic proteins, HAp modified by aspartic acid (Asp, acidic amino acid) might be one of the candidate substrates for a basic protein carrier. Here, we synthesized HAp in the presence of various concentrations of Asp and observed that HAp crystallinity and other physico-chemical properties were effectively modulated. Detailed studies indicated that Asp was not incorporated in the HAp crystal lattice, but rather was trapped in HAp crystals. Protein adsorption studies indicated that the HAp particles modified by Asp had a selective loading capacity for basic protein. Therefore, HAp particles containing Asp might have potential in drug delivery applications, especially as the carrier of basic proteins including bFGF and BMP.

DOI： 10.1177/0022034509357309

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Loading and releasing protein in a controllable way is extremely important for the protein vehicles used in bone tissue engineering. To obtain a suitable carrier material for basic proteins, such as BMP or bFGF, hydroxyapatite particles containing mercaptosuccinic acid (mercaptosuccinic acid (Met), (Mer-HAp)) were synthesized Physicochemical evaluation of Mer-HAp suggested that Mer was contained in HAp particles: it either simply adsorbed onto HAp crystals or was trapped among the HAp crystals. A protein adsorption Study using basic and acidic model proteins indicated that the synthesized Mer-HAp had selective loading properties of the basic protein. The loaded protein was gradually released from Mer-HAp in phosphate buffered saline. The protein release rate was different in each Mer-HAp synthesized with a different concentration of Mer. In addition, the protein release from Mer-HAp showed a similar profile with the Ca dissolution in different pH solutions, indicating that the Mer-HAp dissolution was concerned with the protein release from Mer-HAp Thus, Mer-HAp is a useful candidate for the basic protein carrier because it has properties which enable the loading and releasing of protein in a controllable way. (C) 2009 Acta Materialia Inc Published by Elsevier Ltd. All rights reserved

DOI： 10.1016/j.actbio.2009.10.019

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Language：English   Publisher：Nano Biomedical Society  

Biomaterials made using hydroxyapatite (HAp) and calcium phosphates, which are inorganic components of hard tissues, have been developed to fill bone defects caused by various diseases. A biomaterial of HAp containing collagen, an organic component of bone, has also been developed. However, the physical and biological functions of these bone biomaterials remain inadequate.<br>Focusing on Zinc(Zn) and Manganese(Mn) ions out of the divalent cations involved in the activity of integrins, which are molecules existing in cell membranes, we synthesized three kinds of inorganic biomaterials&mdash;pure HAp, Zn-containing HAp (Zn-HAp), and Mn-containing HAp (Mn-HAp)&mdash;by a wet process. These three kinds of HAp powders were formed into pellets of 6mm diameter and 1mm thickness and their bio-adaptability was investigated.<br>In vitro experiments using osteoblast-like cells (MC3T3E1) demonstrated that Mn-HAp showed higher cell adhesion potential than pure HAp, indicating that Mn addition improves bioresponses. This may be because Mn ions eluted from Mn-HAp pellets activated integrins, which are closely related to the cell adhesion potential of MC3T3E1 cells to the surface of the pellets.

DOI： 10.11344/nano.2.37.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Tendon insertions show specific three-dimensional (3D) cell and matrix configurations. To fabricate this transitional tissue in vitro, the development of a cell manipulation technique that can control cell and matrix patterning in the 3D construct is crucial. Bone marrow-derived stromal cells and osteoblasts were respectively cultured in fibrin gel using a custom-made device that can apply uniaxial continuous tensile strain to the gel at different strain rates. Cells in the strained fibrin gel showed a specific orientation, which was parallel to the strain direction, because of the structural change of fibrin fibres within the strained gel. The direction of cell proliferation in the strained gel was also restricted to the same direction. Subsequently, linearly aligned cell sets, similar to the cell patterning of tendon tissue, were obtained in this culture system. Notably, linearly aligned extracellular matrix and mineral patterning, which are crucial for the fabrication of tendon insertions, were also confirmed in the strained fibrin gel. A cell proliferation assay indicated that the strained gel with a higher strain rate enhanced cell proliferation in the gel. In contrast, a Real-Time PCR study indicated that the strained gel with a lower strain rate enhanced cell differentiation in the gel. Thus, our new cell culture system enabled us to fabricate a 3D construct containing patterned cells and matrices in a controllable manner. This would be an effective tool for reproducing tendon insertions in vitro.

DOI： 10.1039/b922418a

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Language：English   Publisher：Japanese Association for Oral Biology  

The resorption of alveolar bone in periodontitis and/or following toothextraction results in a significant problem in an individual's oral health-related quality of life. Strategies employing growth factor proteins and/orstem cell-based therapy have been successfully used to regenerate alveolarbone augmentationregeneration/however, cost-effectiveness issues illustratethe need for developing alternative strategies. One promising approach is the development of conventional chemical and biological therapeuticsto strongly stimulate endogenous cells to regenerate. Small-molecule compounds can have a variety of biological functions, serving as cell signaling molecules, as tools in molecular biology, and as drugs in medicine. Therefore, the discovery of natural and novel small-molecule synthetic regulators of differentiation and maturation of osteoblasts and/or osteoclasts would acceleratethe development of bone regenerative medicine. Recently,"chemical biology" has started to play an increasingly important role in both drug discovery and elucidating the mechanism of biological phenomena. This review first addresses the current needs and strategies for alveolar bone regeneration, followed by the potential small molecules associated with bone regeneration, with a concluding section on chemical biology-based high throughput screening approaches for identifying small molecules targeting osteoblast/osteoclast differentiation.

DOI： 10.2330/joralbiosci.52.107

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/adem.200800392

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Recently, the binding sequence Ser-Val-Val-Tyr-Gly-Leu-Arg (SVVYGLR) was found adjacent to the RGD sequence in osteopontin, suggesting involvement in osteo-immune cross-talk. The aim of this study was to investigate bioactive functions of a synthetic SVVYGLR peptide in osteoprogenitor cells and osteoclasts, and to examine potential applications in bone regeneration. The SVVYGLR peptide significantly enhanced the adhesion and proliferation of several human mesenchymal cells including bone marrow-derived mesenchymal stem cells, and alpha v beta 3 integrin was involved in cell attachment to the peptide. Additionally, the peptide reduced the number of TRAP-positive multinucleated cells during osteoclastogenesis of RAW264.7 cells and normal murine pre-osteoclasts, and also suppressed NFAT activity and expression of osteoclastogenesis-related mRNAs. When standardized bone defects in rat calvariae were filled with a collagen sponge containing the peptide or PBS (control), the number of TRAP-positive osteoclasts in the grafted sites after 3 weeks was significantly lower in the peptide group. By the 5th week, significantly enhanced resorption of the grafted collagen sponge and new bone formation was observed within and surrounding the sponge in the peptide group. These data suggest that SVVYGLR is an effective bioactive peptide for bone tissue regeneration that promotes attachment and proliferation of osteogenic cells while also suppressing osteoclastogenesis. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biomaterials.2009.05.032

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Octacalcium phosphate (OCP) and adipic acid-intercalated complexed OCP (Adi-OCP) were synthesized. Moreover, we made ceramic bodies out of them through a hydrothermal hot-pressing (HHP) method. Characteristic features of both the powder and ceramics were investigated by the X-ray diffraction method (XRD). Surface morphology of the ceramics was observed by scanning electron microscopy (SEM). Density, compressive strength and pore size distribution of the ceramics were measured. Crystalline structure of the newly developed OCP ceramics had no phase transformation from the starting materials. Moreover, the newly developed OCP ceramics had good mechanical properties only through the HHP treatment with a temperature as low as 110 degrees C. In order to evaluate bioactivity, the ceramics were immersed in simulating body fluid (SBF). It was predicted that OCP and Adi-OCP had better bioactivity than that of conventional HAp ceramics. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msec.2009.02.023

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：QUINTESSENCE PUBLISHING CO INC  

Purpose: Disinfection of dental impressions is an indispensable procedure for the control of cross-contaminatior however, there is limited information on the efficacy of disinfection under clinical conditions. The objective of this study was to clinically evaluate the disinfection efficacy of commercially available agents in removing oral pathogens from patient-derived impressions. Materials and Methods: Impressions from 54 patients were divided into groups and either left undisinfected or underwent I of 5 disinfection treatments: ( 1) 2% glutaraldehyde (GA), (2) 1% sodium hypochlorite (SH), (3) 0.25% benzalkonium chloride (BC), (4) 1 ppm ozonated water (OW), or (5) the Hygojet/MD520 system (HJ). An impression culture technique using a brain heart infusion agar medium was used to visualize the microbial contamination on the surface of the impression cultures. The persistent presence of oral pathogens on the impression cultures was examined using selective isolation agar plates. Results: The isolation frequencies of streptococci, staphylococci, Candida, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa species from undisinfected impressions were 100%, 55.6%, 25.9%. 25.9% and 5.6%. respectively. Disinfection with HJ and BC removed the microorganisms with the greatest efficacy, followed by GA, SH, and OW. Potential bacterial contamination could be detected even after disinfection had been performed. Combined use of BC plus GA or SH removed oral pathogens almost completely from dental impressions, Conclusions: This investigation showed that potential contaminants are still present, even after general disinfection procedures. Therefore. either HJ or the combined use of BC with GA or SH is recommended for clinical and laboratory use. Int J Prosthodont 200821,531-538.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

We have previously reported that an osteopontin -derived SVVYGLR peptide exhibited potent angiogenic activity in vitro and in vivo. In the present study, the focus points were on the in vitro effect of SVVYGLR on bone marrow stromal cell proliferation, as well as its in vivo effect on bone tissue formation when grafts made Of CO3 Ap-collagen sponge-as a scaffold biornaterial containing the SVVYGLR motif - were implanted. SVVYGLR peptide promoted bone marrow stromal cell proliferation. When a CO,Ap-collagen sponge containing SVVYGLR peptide was implanted as a graft into a tissue defect created in rat tibia, the migration of numerous vascular endothelial cells - as well as prominent angiogenesis - inside the graft could be detected after one week. These results thus suggested that our scaffold biomaterials including the peptide could be useful for bone tissue regeneration.

DOI： 10.4012/dmj.26.487

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

We have previously reported that an osteopontin -derived SVVYGLR peptide exhibited potent angiogenic activity in vitro and in vivo. In the present study, the focus points were on the in vitro effect of SVVYGLR on bone marrow stromal cell proliferation, as well as its in vivo effect on bone tissue formation when grafts made Of CO3 Ap-collagen sponge-as a scaffold biornaterial containing the SVVYGLR motif - were implanted. SVVYGLR peptide promoted bone marrow stromal cell proliferation. When a CO,Ap-collagen sponge containing SVVYGLR peptide was implanted as a graft into a tissue defect created in rat tibia, the migration of numerous vascular endothelial cells - as well as prominent angiogenesis - inside the graft could be detected after one week. These results thus suggested that our scaffold biomaterials including the peptide could be useful for bone tissue regeneration.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Hydroxyapatite (HAp) materials with different morphology, size and crystallinity were prepared and were implanted into a male rat tibia. Each of the HAp materials showed a high biocompatiblity and osteoconductivity. The morphology and size of the implanted HAp affected the intrusion of bone marrow derived cells among HAp materials, and this cell intrusion was important for regulating the newly formed bone mass. High crystalline sintered HAp was stable and remained in its initial shape for long periods. However, low crystalline HAp was absorbed and disappeared during bone remodeling. This study indicates that choosing suitable HAp materials in morphology, size and crystallinity is important for a treatment plan (e.g. reconstruction or regeneration; large region or small region etc.) and for achieving a desired prognosis.

DOI： 10.2109/jcersj.114.760

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Hydroxyapatite (HAp) materials with different morphology, size and crystallinity were prepared and were implanted into a male rat tibia. Each of the HAp materials showed a high biocompatiblity and osteoconductivity. The morphology and size of the implanted HAp affected the intrusion of bone marrow derived cells among HAp materials, and this cell intrusion was important for regulating the newly formed bone mass. High crystalline sintered HAp was stable and remained in its initial shape for long periods. However, low crystalline HAp was absorbed and disappeared during bone remodeling. This study indicates that choosing suitable HAp materials in morphology, size and crystallinity is important for a treatment plan (e.g. reconstruction or regeneration; large region or small region etc.) and for achieving a desired prognosis.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

Non-collagenous proteins in hard tissue matrix are thought to play a pivotal role in regulating the crystal growth of hydroxyapatite (HAp). As most non-collagenous proteins are acidic proteins containing acidic amino acid-rich sequences, we examined the growth of HAp crystals from HAp seed crystals in the presence/absence of acidic amino acid. New HAp formation generally started from the P-surface of HAp. However, in the presence of acidic amino acid, new HAp formation was observed on both P-surface and C-surface of HAp seed crystals. Furthermore, newly formed HAp showed specific orientation along the long-axis direction of HAp seed crystals. In terms of crystallinity, HAp formed in the presence of acidic amino acid showed low crystallinity. These results suggested that, in biomineralization, the adsorbed or free state of acidic amino acid would influence crystal formation and orientation as follows: 1) If free in solution, acidic amino acid would inhibit HAp crystal growth; 2) If adsorbed or immobilized on matrix, acidic amino acid would become HAp nucleation site and regulate the orientation of HAp crystals.

DOI： 10.4012/dmj.25.360

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG BERLIN  

Polymeric materials used in tissue engineering were initially used solely as delivery vehicles for transplanting cells. However, these materials are currently designed to actively regulate the resultant tissue structure and function. This control is achieved through spatial and temporal regulation of various cues (e.g., adhesion ligands, growth factors) provided to interacting cells from the material. These polymeric materials that control cell function and tissue formation are termed cell instructive polymers, and recent trends in their design are outlined in this chapter.

DOI： 10.1007/b137207

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Ceramic Society of Japan  

Hydroxyapatite (HAp) materials with different morphology, size and crystallinity were prepared and were implanted into a male rat tibia. Each of the HAp materials showed a high biocompatiblity and osteoconductivity. The morphology and size of the implanted HAp affected the intrusion of bone marrow derived cells among HAp materials, and this cell intrusion was important for regulating the newly formed bone mass. High crystalline sintered HAp was stable and remained in its initial shape for long periods. However, low crystalline HAp was absorbed and disappeared during bone remodeling. This study indicates that choosing suitable HAp materials in morphology, size and crystallinity is important for a treatment plan (e.g. reconstruction or regeneration
large region or small region etc.) and for achieving a desired prognosis.

DOI： 10.2109/jcersj.114.760

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

The chemical analysis of hydroxyapatite and fluorapatite was carried out using time-of-flight secondary ion mass spectrometry (TOF-SEAS). Hydroxyapatite and fluorapatite were synthesized at 80 +/- 1 degrees C and pH 7.4 +/- 0.2. Fluorapatite was better crystallized, with its (300) reflection shifted to a slightly higher angle. High-resolution transmission electron microscopy clearly revealed a typical, regular hexagonal cross section perpendicular to the c-axis for fluorapatite and a flattened hexagonal cross section for hydroxyapatite. FT-IR spectra of fluorapatite confirmed the absence of OH absorption peak - which was seen in hydroxyapatite at about 3570 cm(-1). TOF-SIMS mass spectra showed a peak at 40 amu due to calcium. In addition, a peak at 19 amu due to fluorine could be clearly seen, although the intensities Of PO, PO2, and PO3 were very low. It was confirmed that TOF-SIMS clearly showed the differences between positive and negative mass spectra of hydroxyapatite and fluorapatite, especially for F-. We concluded that TOF-SIMS exhibited distinct advantages compared with other methods of analysis.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MATERIALS RESEARCH SOCIETY  

Al2O3/BN nanocomposites were fabricated through a novel chemical route involving hot-pressing of alpha-Al2O3 powders covered partly with turbostratic BN (t-BN). The nano-sized hexagonal BN (h-BN) particles were found to be homogeneously dispersed within the Al2O3 grains as well as at grain boundaries, which is indicative of nanocomposite structures. Thus, the present nanocomposites exhibited the unique properties of high strength and low Young's modulus associated with nanocomposites. This paper discusses in detail the synthesis process and microstructural features of these materials.

DOI： 10.1557/JMR.2005.0010

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

Our previous study reported that an osteopontin-derived peptide SVVYGLR activates the adhesion, migration and tube formation abilities of endothelial cells in vitro. The present study investigated angiogenesis due to synthetic SVVYGLR and mutant peptides in vivo. Mutant peptides (n = 7) were synthesized by substituting alanine (A) for one of the 7 amino acids comprising SVVYGLR. In dorsal air sac assay, mouse dorsal skin 5 days after implantation of a chamber filled with SVVYGLR had approximately the same number of newly formed blood vessels to that filled with vascular endothelial growth factor (VEGF). The ability of angiogenesis due to SVVAGLR was significantly lower than that due to other 6 mutant peptides and SVVYGLR. This indicates that tyrosine (Y) plays an important role in angiogenesis due to SVVYGLR.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Angiogenesis plays an important role in various pathological conditions as well as some physiological processes. Although a number of soluble angiogenic factors have been reported, extracellular matrix also has crucial effect on angiogenesis through interaction with endothelial cells. Since recent reports showed osteopontin had some angiogenic activity, the effect of the SVVYGLR peptide, novel binding motif in osteopontin molecule, on angiogenesis was examined in this study. Synthetic peptide SVVYGLR did not have proliferative effect on endothelial cells but adhesion and migration activity to endothelial cells. Furthermore, SVVYGLR had as potent activity for tube formation in three-dimensional collagen gel as vascular endothelial growth factor which is known to be the strongest angiogenic factor. Electron microscopical analysis showed a number of microvilli on the endothelial luminar surface and tight junction formation in the luminar intercellular border between endothelial cells, indicating SVVYGLR induced cell porarity and differentiation of endothelial cells. This small peptide might be expected to stimulate angiogenesis to improve some ischemic conditions in the future because of some advantages due to smaller molecular weight. (C) 2003 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.bbrc.2003.09.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC DENTAL MATERIALS DEVICES  

In the regeneration,and repair of missing tissues, synthetic polymer scaffolds need many pores to involve cells and to supply cells with nutrients. The control of the pore size of biodegradable L-lactide/epsilon-caprolactone copolymer foams was studied by changing the polymer concentration and the cooling temperature in the freeze-drying method. The mixtures of polymer and 1, 4-dioxane solution were poured into an 18-8 stainless steel Petri dish and frozen. The pore size of a polymer foam tends to increase from the bottom towards the top of a Petri dish. The pore size decreased to one-half with increasing polymer concentration (1 to 10 wt%). The mean pore size in foams of 8% polymer concentration decreased from 100mum to 20mum as cooling temperature was lowered. This suggests that the,higher cooling rate due to lower cooling temperature can produce smaller ice-crystals and result in smaller pores.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：QUINTESSENCE PUBL CO INC  

Purpose: The objective of this study was to examine the cytotoxic effect of methyl methacrylate (MMA) monomer on 4 mammalian fibroblasts. Materials and Methods: Four cells-C3H10T1/2, L929, Balb/3T3 clone A31, and MC3T3-E1-were incubated for 6 days in 24-well microplates filled with 1 mL of Dulbecco's Modified Eagle medium containing MMA monomer that ranged from 0 to 200 mM/L. Cytotoxicity was evaluated by direct cell number count. Results: L929 possessed the largest TC,, value (the amount of MMA that caused 50% cell death) (34 mM/L), and Balb/3T3 clone A31 had the least value (1 mM/L); C3H10T1/2 and MC3T3-E1 had intermediate values (25 mM/L and 16 mM/L, respectively). Conclusion: This study showed that the MMA monomer had dose-dependent cytotoxicity, which Varied among the cells tested.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KARGER  

Hydroxyapatite (HAp) and fluorapatite (FAp) were synthesized in the presence of carbohydrates (glucose, fructose, galactose and sucrose), X-ray diffraction analysis showed that the crystallinity of two FAp groups that were synthesized in the presence of glucose or sucrose decreased with the increase in carbohydrate content, In SEM photographs we found that the size of their crystals was small and the shape changed. However, FAp groups that were snythesized in the presence of fructose or galactose showed little change in their crystallinity and shape, Four carbohydrates had some influence on size, but not on shape or crystallinity when synthesizing HAp. These results suggest that glucose and/or sucrose has a chemical affinity to FAp and inhibits the growth of FAp crystals, Copyright (C) 2000 S. Karger AG, Basel.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TRANS TECH PUBLICATIONS LTD  

The number and the structure of cross-links in type I collagen are different from each organ, therefore, orientation and diameter of type I collagen fibers are also different from each organ. When type I collagen is used as biomaterials for hard tissue regeneration, it can be considered that the characteristics and the quantity of newly created minerals in type I collagen are different depending on organs-derived. In this study, calcium phosphate were synthesized in type I collagen gels derived from pig skin or tendon and bovine bone, and the characteristics of obtained minerals were investigated. It was suggested that all the newly created products were octacalcium phosphate (OCP) in X-ray diffraction analysis. Furthermore, X-ray diffraction analysis showed that minerals obtained in bone collagen gel were significantly high in crystallinity compared with minerals obtained in skin and tendon collagen gel. However, the quantity of the newly created minerals in bone collagen decreased significantly compared with minerals obtained in skin and tendon collagen. Collectively these results suggest that the characteristics and quantity of minerals synthesized in type I collagen are depending on organ of origin.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Fluoridated hydroxyapatite was synthesized at 80 +/- 1 degrees C and pH 7.4 +/- 0.2 using a gradient fluoride supply system. X-ray diffraction analysis showed a typically apatitic pattern, although the (3 0 0) reflection was broader than that of homogeneous fluorapatite. Scanning electron micrographic observation indicated that the apatite was composed of rod-like crystals similarly to fluorapatite. High-resolution transmission electron microscopy showed electron damage in the core of the crystal. When the apatite pellet was prepared, electron spectroscopy for chemical analysis showed a negative gradient of fluoride concentration with depth in the crystals. The apparent solubility in 0.5 mol/l acetate buffer solution (37 degrees C and pH 4.0) was 9.16 +/- 0.39 mmol/l, much less than that of homogeneous hydroxyapatite 32.3 +/- 1.9 mmol/l, and less than that of heterogeneous two-layer fluoridated apatite with an outer fluoride-rich layer 12.5 +/- 0.6 mmol/l, which was synthesized previously by supplying fluoride during the latter half of the experimental period. These results suggest that graded fluoridated apatite may be formed by this process and have higher acid resistance than two-layer fluoridated apatite. (C) 1999 Elsevier Science Ltd. All rights reserved.

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Mechanical strain regulates endothelial cell patterning in vitro.

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：岡山歯学会  

高透光性ジルコニア(イットリアの含有量を増やして結晶相組成を変化させた部分安定化ジルコニア:PSZ)の機械的強度を向上させる工夫としてこれまで、イットリア以外の金属酸化物を添加する方法や、ジルコニア表層にガラスを浸漬させる手法などが試みられているが、強度向上は不十分であった。著者等は、強化ガラスの強化機構である表面圧縮応力層から着想を得て、ジルコニア表面をコーティングすることで表面圧縮応力層を形成させ、高透光性を保ったまま機械的強度を向上させる方法の開発を目指した。コーティング材として、単斜晶ZrO2とSiO2を混合させた分散液を用いた。単斜晶ZrO2の結晶相変化を利用することでPSZ表面に圧縮応力層を形成することを狙いとし、SiO2は無機結合材として添加した。分散液コーティング後に熱処理をすることでPSZの機械的強度は最大1.7倍まで向上した。

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(公社)日本補綴歯科学会  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese   Publisher：(一社)日本歯科理工学会  

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Language：Japanese   Publisher：(一社)日本歯科医学教育学会  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：English   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

Biomineralization occurs in many different animals and tissues. The structure of the mineralized tissue differs in the mineral composition, but also in the arrangement of mineral crystals at a micro- or nanoscale. In this study, we investigated the biomineralization process of cartilage during secondary ossification using micro-computated tomography (μCT), histological analysis and staining with alizarin red S and toluidine blue, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

In vitro fabrication of biological tissue from cells is one of the biggest challenges in bioengineering. For this purpose, the growth and morphological control of tissue is crucial. To control the submandibular gland tissue (SMG) morphogenesis, RGD immobilized alginate hydrogel was prepared, and used for its organotypic culture in this study. RGD immobilized hydrogel sheet enhanced the SMG branching. Moreover, the RGD immobilized hydrogel bead enhanced the region-specific cleft formation in the cultured SMG. Thus, the chemically-modified biomimetic environment fabricated by hydrogel material would be a valuable tool for in vitro modulation of the SMG tissue growth and morphology.

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

This study investigated the relationship between concentration of photoinitiator and generating behavior of polymer radicals, degree of conversion, and bond strength to tooth substrates in one-step adhesive. The experimental adhesives contained Bis-GMA, HEMA, MDP, ethanol, water and various concentration (1, 3 and 5 wt%) of Camphorquinone and Ethyl p-(dimethylamino)benzoate as initiators. The adhesive containing 3wt% initiators always generated higher amount of polymer radicals as compared with the others which showed similar generating behavior. The adhesive containing 1wt% initiators showed the lowest value in degree of conversion and bond strength, while the other two showed relatively high values.

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

We previously reported that three-dimensional (3D) mesenchymal stem cells (MSCs) construct could be fabricated by using thermo-responsive hydrogel. In this study, internal/external environments of the 3D cell construct induced by osteoblastic differentiation were investigated. The specific regions with chondrogenesis and osteogenesis were detected in the 3D cell construct during the culture. Calcified matrix was formed from MSCs inthe process of endochondral ossification. The 3D cell construct composed of MSCs could be a promising toolfor in vitro investigation of osteogenesis.

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

In tissue regeneration therapy, scaffold materials play pivotal roles on carrying cells at the site of tissue regeneration. However, the remained scaffold materials might attenuate the accurate tissue regeneration in some cases. Therefore, creating another cell carrying method without using scaffold material would be important. To obtain scaffold free-3D cell constructs, we synthesized thermo-responsive hydrogel by using poly N-isopropylacrylamide with several cross-linking agents. Consequently, we fabricated clear hydrogel, which changes its volume depending on the temperature. The gel allowed us to obtain 3D cell constructs with desired morphology.

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Language：English   Publisher：SAGE PUBLICATIONS INC  

Physico-chemical modifications of hydroxyapatite (HAp) materials are considered as pre-requisites for the development of new bioactive carrier materials for drug delivery and tissue engineering applications. Since acidic amino acids have well-documented affinities to both HAp and basic proteins, HAp modified by aspartic acid (Asp, acidic amino acid) might be one of the candidate substrates for a basic protein carrier. Here, we synthesized HAp in the presence of various concentrations of Asp and observed that HAp crystallinity and other physico-chemical properties were effectively modulated. Detailed studies indicated that Asp was not incorporated in the HAp crystal lattice, but rather was trapped in HAp crystals. Protein adsorption studies indicated that the HAp particles modified by Asp had a selective loading capacity for basic protein. Therefore, HAp particles containing Asp might have potential in drug delivery applications, especially as the carrier of basic proteins including bFGF and BMP.

DOI： 10.1177/0022034509357309

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

To obtain bioceramic that has both sufficient strength and biocompatibility for bone reconstruction, ZrO_2 /HAp composite with different ratio was sintered at 1500℃. SEM images indicated that ZrO_2 (100%) had a solid structure, whereas sintered HAp (100%) remained porous structure. Protein adsorption, cell adhesion and animal experiments indicated the drastic improvement of bioactivity of materials by containing HAp.

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

Our recent study indicated that hydroxyapatite (HAp) synthesized in the presence of aspartic acid showed special affinity to basic molecules. In addition, the detailed TEM observations indicated that small peapod like voids were formed in the HAp-Asp crystals. To understand the mechanism of this void formation, further TEM observations of synthesized HAp, HAp-Gly or HAp-Asp synthesized with different concentration of Asp were carried out. The results indicated that the organics contained in HAp-Asp or HAp-Gly were crucial on this void formation and alignment.

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Language：English   Publisher：ELSEVIER SCI LTD  

Loading and releasing protein in a controllable way is extremely important for the protein vehicles used in bone tissue engineering. To obtain a suitable carrier material for basic proteins, such as BMP or bFGF, hydroxyapatite particles containing mercaptosuccinic acid (mercaptosuccinic acid (Met), (Mer-HAp)) were synthesized Physicochemical evaluation of Mer-HAp suggested that Mer was contained in HAp particles: it either simply adsorbed onto HAp crystals or was trapped among the HAp crystals. A protein adsorption Study using basic and acidic model proteins indicated that the synthesized Mer-HAp had selective loading properties of the basic protein. The loaded protein was gradually released from Mer-HAp in phosphate buffered saline. The protein release rate was different in each Mer-HAp synthesized with a different concentration of Mer. In addition, the protein release from Mer-HAp showed a similar profile with the Ca dissolution in different pH solutions, indicating that the Mer-HAp dissolution was concerned with the protein release from Mer-HAp Thus, Mer-HAp is a useful candidate for the basic protein carrier because it has properties which enable the loading and releasing of protein in a controllable way. (C) 2009 Acta Materialia Inc Published by Elsevier Ltd. All rights reserved

DOI： 10.1016/j.actbio.2009.10.019

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Other Link： http://search.jamas.or.jp/link/ui/2010140743

Language：English   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/adem.200800392

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

Branching morphogenesis is an essential morphological process observed in developmental glandular organs. For organ culture substrate, alginate hydrogel with different mechanical property (stiffness) or chemical property (modified by different concentration of RGD peptide) was prepared. Embryonic mouse submandibular glands (SMG) cultured on the soft substrate or on the substrate modified by high concentration of RGD peptide enhanced the branching morphogenesis of SMG. Thus, the physico-chemical modification of tissue culture substrate would be one of the valuable methods that one can control the branching morphogenesis of salivary gland development.

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

To obtain bioceramic that has both sufficient strength and biocompatibility for bone reconstruction, HAp and ZrO_2 with different ratio was sintered at 1500℃. SEM images indicated that sintered HAp (100%) remained porous structure, whereas ZrO_2 (100%) had a solid structure. The composite ceramics (HAp/ZrO_2=40/60) showed lowest contraction (22.55%) in volume. Thus, the composite ceramics have different material properties depending on the mixture ratio of HAp and ZrO_2.

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

Fibrin is a natural polymer known for supporting wound healing by inducing angiogenesis and promoting cell attachment and proliferation. Thus fibrin may provide an ideal environment for accelerating bone regeneration. In this study, we developed a novel composite scaffold consist of ZrO_2/HAp and fibrin gel with osteoblasts and evaluated the biocompatibility of the synthesized materials.

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Language：English   Publisher：ELSEVIER SCI LTD  

Recently, the binding sequence Ser-Val-Val-Tyr-Gly-Leu-Arg (SVVYGLR) was found adjacent to the RGD sequence in osteopontin, suggesting involvement in osteo-immune cross-talk. The aim of this study was to investigate bioactive functions of a synthetic SVVYGLR peptide in osteoprogenitor cells and osteoclasts, and to examine potential applications in bone regeneration. The SVVYGLR peptide significantly enhanced the adhesion and proliferation of several human mesenchymal cells including bone marrow-derived mesenchymal stem cells, and alpha v beta 3 integrin was involved in cell attachment to the peptide. Additionally, the peptide reduced the number of TRAP-positive multinucleated cells during osteoclastogenesis of RAW264.7 cells and normal murine pre-osteoclasts, and also suppressed NFAT activity and expression of osteoclastogenesis-related mRNAs. When standardized bone defects in rat calvariae were filled with a collagen sponge containing the peptide or PBS (control), the number of TRAP-positive osteoclasts in the grafted sites after 3 weeks was significantly lower in the peptide group. By the 5th week, significantly enhanced resorption of the grafted collagen sponge and new bone formation was observed within and surrounding the sponge in the peptide group. These data suggest that SVVYGLR is an effective bioactive peptide for bone tissue regeneration that promotes attachment and proliferation of osteogenic cells while also suppressing osteoclastogenesis. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biomaterials.2009.05.032

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Language：English   Publisher：ELSEVIER SCIENCE BV  

Octacalcium phosphate (OCP) and adipic acid-intercalated complexed OCP (Adi-OCP) were synthesized. Moreover, we made ceramic bodies out of them through a hydrothermal hot-pressing (HHP) method. Characteristic features of both the powder and ceramics were investigated by the X-ray diffraction method (XRD). Surface morphology of the ceramics was observed by scanning electron microscopy (SEM). Density, compressive strength and pore size distribution of the ceramics were measured. Crystalline structure of the newly developed OCP ceramics had no phase transformation from the starting materials. Moreover, the newly developed OCP ceramics had good mechanical properties only through the HHP treatment with a temperature as low as 110 degrees C. In order to evaluate bioactivity, the ceramics were immersed in simulating body fluid (SBF). It was predicted that OCP and Adi-OCP had better bioactivity than that of conventional HAp ceramics. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msec.2009.02.023

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：English   Publisher：WILEY-LISS  

Bidirectional diffusion of the Ca and PO4 solutions into the fibrin gel was performed at various pH conditions and fluoride concentrations to generate organic/inorganic composite materials mimicking biomineralization. The minerals produced in this system had a higher crystallinity than those generated by the Solution mineralization system. The minerals generated in fibrin gel varied depending on the pH conditions as follows: Dicalcium phosphate dihydrate (DCPD) in the noncontrolled pH solution, the DCPD and octacalcium phosphate (OCP) mixture at pH 7.4, and the OCP and hydroxyapatite (HAp) mixture at pH 9.0. When fluoride ions were added in the ram-e of 2-500 ppm, the minerals produced at pH 7.4 altered from OCP/HAp to HAp/fluorapatite (FAp). In addition, the crystallinity of the obtained minerals increased with an increase in fluoride ion concentration, and the Solubility was inversely correlated to crystallinity. In Conclusion, we established I novel fabrication method for synthesizing organic/inorganic composite materials composed of fibrin and calcium phosphate and revealed that the characteristics of the minerals in the synthesized material can be controlled by the fabrication condition. (C) 2007 Wiley Periodicals, Inc.

DOI： 10.1002/jbm.a.31777

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Language：English   Publisher：WILEY-LISS  

Bidirectional diffusion of the Ca and PO4 solutions into the fibrin gel was performed at various pH conditions and fluoride concentrations to generate organic/inorganic composite materials mimicking biomineralization. The minerals produced in this system had a higher crystallinity than those generated by the Solution mineralization system. The minerals generated in fibrin gel varied depending on the pH conditions as follows: Dicalcium phosphate dihydrate (DCPD) in the noncontrolled pH solution, the DCPD and octacalcium phosphate (OCP) mixture at pH 7.4, and the OCP and hydroxyapatite (HAp) mixture at pH 9.0. When fluoride ions were added in the ram-e of 2-500 ppm, the minerals produced at pH 7.4 altered from OCP/HAp to HAp/fluorapatite (FAp). In addition, the crystallinity of the obtained minerals increased with an increase in fluoride ion concentration, and the Solubility was inversely correlated to crystallinity. In Conclusion, we established I novel fabrication method for synthesizing organic/inorganic composite materials composed of fibrin and calcium phosphate and revealed that the characteristics of the minerals in the synthesized material can be controlled by the fabrication condition. (C) 2007 Wiley Periodicals, Inc.

DOI： 10.1002/jbm.a.31777

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Language：English   Publisher：WILEY-LISS  

Bidirectional diffusion of the Ca and PO4 solutions into the fibrin gel was performed at various pH conditions and fluoride concentrations to generate organic/inorganic composite materials mimicking biomineralization. The minerals produced in this system had a higher crystallinity than those generated by the Solution mineralization system. The minerals generated in fibrin gel varied depending on the pH conditions as follows: Dicalcium phosphate dihydrate (DCPD) in the noncontrolled pH solution, the DCPD and octacalcium phosphate (OCP) mixture at pH 7.4, and the OCP and hydroxyapatite (HAp) mixture at pH 9.0. When fluoride ions were added in the ram-e of 2-500 ppm, the minerals produced at pH 7.4 altered from OCP/HAp to HAp/fluorapatite (FAp). In addition, the crystallinity of the obtained minerals increased with an increase in fluoride ion concentration, and the Solubility was inversely correlated to crystallinity. In Conclusion, we established I novel fabrication method for synthesizing organic/inorganic composite materials composed of fibrin and calcium phosphate and revealed that the characteristics of the minerals in the synthesized material can be controlled by the fabrication condition. (C) 2007 Wiley Periodicals, Inc.

DOI： 10.1002/jbm.a.31777

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：MARY ANN LIEBERT INC  

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Language：English   Publisher：QUINTESSENCE PUBLISHING CO INC  

Purpose: This study aimed to assess the persistent presence of microorganisms on patient-derived dental impressions and gypsum casts, while highlighting important human pathogens such as Candida, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. Materials and Methods: The practices and opinions regarding cross-infection control from 59 general dentists in Japan were obtained via a questionnaire. Alginate impressions were made from 56 patients. Using a brain heart infusion agar medium, impression and imprint cultures were carried out to visualize the microbial contamination on the surfaces of the impressions and gypsum casts, respectively. The colonies on the surfaces of the 30 impression cultures and 26 imprint cultures were collected by swabbing and then inoculated onto selective agar plates to detect streptococci, staphylococci, Candida, MRSA, and P aeruginosa. Results: The questionnaire showed that only 54% of general dentists had a cross-infection policy in their dental clinics, and only 30% to 40% were aware of the possible persistence of MRSA or P aeruginosa on impressions and gypsum casts. The impression/imprint cultures grew a large number of visible bacterial colonies on all of the impression/gypsum cast samples investigated. Selective agar cultures demonstrated the presence of streptococci (100, 100%), staphylococci (56.7, 65.4%), Candida (30, 46.2%), MRSA (26.7, 15.4%), and P aeruginosa (6.7, 7.7%) on the impressions and the gypsum casts, respectively. Conclusions: This investigation showed that patient-derived dental impressions and gypsum casts are contaminated with numerous microbes, including Candida, MRSA, and P aeruginosa, which are known pathogens responsible for nosocomial and/or life-threatening infection in the immunocompromised host.

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Language：Japanese   Publisher：Japanese Association of Regenerative Dentistry  

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Language：English   Publisher：PUBLIC LIBRARY SCIENCE  

Techniques developed for the in vitro reproduction of three-dimensional (3D) biomimetic tissue will be valuable for investigating changes in cell function in tissues and for fabricating cell/matrix composites for applications in tissue engineering techniques. In this study, we show that the simple application of a continuous strain to a fibrin gel facilitates the development of fibril alignment and bundle-like structures in the fibrin gel in the direction of the applied strain. Myoblasts cultured in this gel also exhibited well-aligned cell patterning in a direction parallel to the direction of the strain. Interestingly, the direction of cell proliferation was identical to that of cell alignment. Finally, the oriented cells formed linear groups that were aligned parallel to the direction of the strain and replicated the native skeletal muscle cell patterning. In addition, vein endothelial cells formed a linear, aligned vessel-like structure in this system. Thus, the system enables the in vitro reproduction of 3D aligned cell sets replicating biological tissue patterns.

DOI： 10.1371/journal.pone.0001211

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Language：English   Publisher：PUBLIC LIBRARY SCIENCE  

Techniques developed for the in vitro reproduction of three-dimensional (3D) biomimetic tissue will be valuable for investigating changes in cell function in tissues and for fabricating cell/matrix composites for applications in tissue engineering techniques. In this study, we show that the simple application of a continuous strain to a fibrin gel facilitates the development of fibril alignment and bundle-like structures in the fibrin gel in the direction of the applied strain. Myoblasts cultured in this gel also exhibited well-aligned cell patterning in a direction parallel to the direction of the strain. Interestingly, the direction of cell proliferation was identical to that of cell alignment. Finally, the oriented cells formed linear groups that were aligned parallel to the direction of the strain and replicated the native skeletal muscle cell patterning. In addition, vein endothelial cells formed a linear, aligned vessel-like structure in this system. Thus, the system enables the in vitro reproduction of 3D aligned cell sets replicating biological tissue patterns.

DOI： 10.1371/journal.pone.0001211

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Language：English   Publisher：NATURE PUBLISHING GROUP  

Microenvironmental conditions control tumorigenesis and biomimetic culture systems that allow for in vitro and in vivo tumor modeling may greatly aid studies of cancer cells' dependency on these conditions. We engineered three-dimensional ( 3D) human tumor models using carcinoma cells in polymeric scaffolds that recreated microenvironmental characteristics representative of tumors in vivo. Strikingly, the angiogenic characteristics of tumor cells were dramatically altered upon 3D culture within this system, and corresponded much more closely to tumors formed in vivo. Cells in this model were also less sensitive to chemotherapy and yielded tumors with enhanced malignant potential. We assessed the broad relevance of these findings with 3D culture of other tumor cell lines in this same model, comparison with standard 3D Matrigel culture and in vivo experiments. This new biomimetic model may provide a broadly applicable 3D culture system to study the effect of microenvironmental conditions on tumor malignancy in vitro and in vivo.

DOI： 10.1038/NMETH1085

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Language：English   Publisher：NATURE PUBLISHING GROUP  

Microenvironmental conditions control tumorigenesis and biomimetic culture systems that allow for in vitro and in vivo tumor modeling may greatly aid studies of cancer cells' dependency on these conditions. We engineered three-dimensional ( 3D) human tumor models using carcinoma cells in polymeric scaffolds that recreated microenvironmental characteristics representative of tumors in vivo. Strikingly, the angiogenic characteristics of tumor cells were dramatically altered upon 3D culture within this system, and corresponded much more closely to tumors formed in vivo. Cells in this model were also less sensitive to chemotherapy and yielded tumors with enhanced malignant potential. We assessed the broad relevance of these findings with 3D culture of other tumor cell lines in this same model, comparison with standard 3D Matrigel culture and in vivo experiments. This new biomimetic model may provide a broadly applicable 3D culture system to study the effect of microenvironmental conditions on tumor malignancy in vitro and in vivo.

DOI： 10.1038/NMETH1085

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：English   Publisher：MARY ANN LIEBERT INC  

Blood vessels of the vertebrate circulatory system typically exhibit tissue-specific patterning. However, the cues that guide the development of these patterns remain unclear. We investigated the effect of cyclic uniaxial strain on vascular endothelial cell dynamics and sprout formation in vitro in two-dimensional (2D) and three-dimensional (3D) culture systems under the influence of growth factors. Cells preferentially aligned and moved in the direction perpendicular to the major strain axis in monolayer culture, and mechanical strain also regulated the spatial location of cell proliferation in 2D cell culture. Cells in 3D cell culture could be induced to form sprouts by exposure to appropriate growth factor combinations (vascular endothelial growth factor and hepatocyte growth factor), and the strain direction regulated the directionality of this process. Moreover, cyclic uniaxial strain inhibited branching of the structures formed by endothelial cells and increased their thickness. Taken together, these data support the importance of external mechanical stimulation in the regulation of endothelial cell migration, proliferation, and differentiation into primitive vessels.

DOI： 10.1089/ten.2006.0058

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Language：English   Publisher：MARY ANN LIEBERT INC  

Blood vessels of the vertebrate circulatory system typically exhibit tissue-specific patterning. However, the cues that guide the development of these patterns remain unclear. We investigated the effect of cyclic uniaxial strain on vascular endothelial cell dynamics and sprout formation in vitro in two-dimensional (2D) and three-dimensional (3D) culture systems under the influence of growth factors. Cells preferentially aligned and moved in the direction perpendicular to the major strain axis in monolayer culture, and mechanical strain also regulated the spatial location of cell proliferation in 2D cell culture. Cells in 3D cell culture could be induced to form sprouts by exposure to appropriate growth factor combinations (vascular endothelial growth factor and hepatocyte growth factor), and the strain direction regulated the directionality of this process. Moreover, cyclic uniaxial strain inhibited branching of the structures formed by endothelial cells and increased their thickness. Taken together, these data support the importance of external mechanical stimulation in the regulation of endothelial cell migration, proliferation, and differentiation into primitive vessels.

DOI： 10.1089/ten.2006.0058

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Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：BENTHAM SCIENCE PUBL LTD  

Apatite-related calcium phosphate, the main component of biological hard tissue, has good biocompatibility and is an economical material. Methods for the synthesis of apatite materials including hydroxyapatite (HAp) have previously been established. Therefore, for many years, apatite materials have been utilized as substitute materials for bone in orthopedic and dental fields. Such types of conventional substitute materials, which are implanted in the human body, should ostensibly be chemically stable to maintain their quality over time. However, recent advances in tissue engineering have altered this concept. Physicians and researchers now seek to identify materials that alter their properties temporally and spatially to achieve ideal tissue regeneration. In order to use apatite materials for tissue engineering and as drug delivery systems, the materials require both a high affinity for cells, tissues and/or functional molecules (e.g. growth factors and genes) and controllable bioabsorbability. To achieve these properties, various physicochemical modifications of apalite materials have been attempted. In addition, fabrication desiring three-dimensional structures (e.g. size, morphology and porositv) of apatite materials for implant sites could be one of the crucial techniques used to obtain ideal prognoses. In this review, the latest research trends relating to the techniques for the fabrication and modification of apatite materials are introduced.

DOI： 10.2174/092986707782023208

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Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：BENTHAM SCIENCE PUBL LTD  

Apatite-related calcium phosphate, the main component of biological hard tissue, has good biocompatibility and is an economical material. Methods for the synthesis of apatite materials including hydroxyapatite (HAp) have previously been established. Therefore, for many years, apatite materials have been utilized as substitute materials for bone in orthopedic and dental fields. Such types of conventional substitute materials, which are implanted in the human body, should ostensibly be chemically stable to maintain their quality over time. However, recent advances in tissue engineering have altered this concept. Physicians and researchers now seek to identify materials that alter their properties temporally and spatially to achieve ideal tissue regeneration. In order to use apatite materials for tissue engineering and as drug delivery systems, the materials require both a high affinity for cells, tissues and/or functional molecules (e.g. growth factors and genes) and controllable bioabsorbability. To achieve these properties, various physicochemical modifications of apalite materials have been attempted. In addition, fabrication desiring three-dimensional structures (e.g. size, morphology and porositv) of apatite materials for implant sites could be one of the crucial techniques used to obtain ideal prognoses. In this review, the latest research trends relating to the techniques for the fabrication and modification of apatite materials are introduced.

DOI： 10.2174/092986707782023208

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：English   Publisher：NATURE PUBLISHING GROUP  

Non-viral gene vectors are commonly used for gene therapy(1-3) owing to safety concerns with viral vectors(4). However, nonviral vectors are plagued by low levels of gene transfection and cellular expression(1,2). Current efforts to improve the efficiency of non-viral gene delivery are focused on manipulations of the delivery vector(5-12), whereas the influence of the cellular environment in DNA uptake is oft en ignored. The mechanical properties ( for example, rigidity) of the substrate to which a cell adheres have been found to mediate many aspects of cell function including proliferation, migration and differentiation(13-17), and this suggests that the mechanics of the adhesion substrate may regulate a cell's ability to uptake exogeneous signalling molecules. In this report, we present a critical role for the rigidity of the cell adhesion substrate on the level of gene transfer and expression. The mechanism relates to material control over cell proliferation, and was investigated using a fluorescent resonance energy transfer (FRET) technique(18-21). This study provides a new material-based control point for non-viral gene therapy.

DOI： 10.1038/nmat1392

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Language：English   Publisher：NATURE PUBLISHING GROUP  

Non-viral gene vectors are commonly used for gene therapy(1-3) owing to safety concerns with viral vectors(4). However, nonviral vectors are plagued by low levels of gene transfection and cellular expression(1,2). Current efforts to improve the efficiency of non-viral gene delivery are focused on manipulations of the delivery vector(5-12), whereas the influence of the cellular environment in DNA uptake is oft en ignored. The mechanical properties ( for example, rigidity) of the substrate to which a cell adheres have been found to mediate many aspects of cell function including proliferation, migration and differentiation(13-17), and this suggests that the mechanics of the adhesion substrate may regulate a cell's ability to uptake exogeneous signalling molecules. In this report, we present a critical role for the rigidity of the cell adhesion substrate on the level of gene transfer and expression. The mechanism relates to material control over cell proliferation, and was investigated using a fluorescent resonance energy transfer (FRET) technique(18-21). This study provides a new material-based control point for non-viral gene therapy.

DOI： 10.1038/nmat1392

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：English   Publisher：ELSEVIER SCI LTD  

This study examines the possibility of using hydroxyapatite (HAp) particles as a controlled release carrier of protein. In order to achieve effective protein release from HAp particles, it is necessary to regulate the conjugated amount of protein on HAp and the resorption of HAp. HAp particles were synthesized at different temperatures (40 degreesC, 60 degreesC, 80 degreesC) in wet condition and the physicochemical properties of synthesized HAp particles were examined. HAp particles synthesized at low temperatures showed low crystallinity, high solubility and large specific surface area. The useful growth factors for bone regeneration, such as BMP, bFGF and TGF-beta, are basic proteins, so cytochrome c (pI = 10.2) was used as a model protein and the adsorptive property of protein on HAp particles was investigated. The protein adsorption on HAp particles changed depending on its specific surface area and the chart of protein adsorption on HAp particles showed a typical Langmuir curve. These findings suggest that the adsorbed amount of protein on HAp particles could be regulated by HAp synthesizing temperature and the concentrations of protein solution. The release kinetics of protein from the HAp particles that adsorbed the protein (HAp-pro) was also evaluated in different pH solutions (pH 4.0 and 7.0). The released protein gradually increased time dependently when HAp-pro were immersed in pH 4.0 solution, but the released protein was significantly smaller when HAp-pro were immersed in pH 7.0 solution. Moreover, the release rate of protein from HAp-pro differed in each HAp that was synthesized at different temperatures, suggesting that the release of protein from HAp-pro depended on HAp resorption. These results suggest that HAp particles synthesized at different temperature are useful as a controlled release carrier of protein. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biomaterials.2003.10.081

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Language：English   Publisher：ELSEVIER SCI LTD  

This study examines the possibility of using hydroxyapatite (HAp) particles as a controlled release carrier of protein. In order to achieve effective protein release from HAp particles, it is necessary to regulate the conjugated amount of protein on HAp and the resorption of HAp. HAp particles were synthesized at different temperatures (40 degreesC, 60 degreesC, 80 degreesC) in wet condition and the physicochemical properties of synthesized HAp particles were examined. HAp particles synthesized at low temperatures showed low crystallinity, high solubility and large specific surface area. The useful growth factors for bone regeneration, such as BMP, bFGF and TGF-beta, are basic proteins, so cytochrome c (pI = 10.2) was used as a model protein and the adsorptive property of protein on HAp particles was investigated. The protein adsorption on HAp particles changed depending on its specific surface area and the chart of protein adsorption on HAp particles showed a typical Langmuir curve. These findings suggest that the adsorbed amount of protein on HAp particles could be regulated by HAp synthesizing temperature and the concentrations of protein solution. The release kinetics of protein from the HAp particles that adsorbed the protein (HAp-pro) was also evaluated in different pH solutions (pH 4.0 and 7.0). The released protein gradually increased time dependently when HAp-pro were immersed in pH 4.0 solution, but the released protein was significantly smaller when HAp-pro were immersed in pH 7.0 solution. Moreover, the release rate of protein from HAp-pro differed in each HAp that was synthesized at different temperatures, suggesting that the release of protein from HAp-pro depended on HAp resorption. These results suggest that HAp particles synthesized at different temperature are useful as a controlled release carrier of protein. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biomaterials.2003.10.081

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Language：English   Publisher：ELSEVIER SCI LTD  

This study examines the possibility of using hydroxyapatite (HAp) particles as a controlled release carrier of protein. In order to achieve effective protein release from HAp particles, it is necessary to regulate the conjugated amount of protein on HAp and the resorption of HAp. HAp particles were synthesized at different temperatures (40 degreesC, 60 degreesC, 80 degreesC) in wet condition and the physicochemical properties of synthesized HAp particles were examined. HAp particles synthesized at low temperatures showed low crystallinity, high solubility and large specific surface area. The useful growth factors for bone regeneration, such as BMP, bFGF and TGF-beta, are basic proteins, so cytochrome c (pI = 10.2) was used as a model protein and the adsorptive property of protein on HAp particles was investigated. The protein adsorption on HAp particles changed depending on its specific surface area and the chart of protein adsorption on HAp particles showed a typical Langmuir curve. These findings suggest that the adsorbed amount of protein on HAp particles could be regulated by HAp synthesizing temperature and the concentrations of protein solution. The release kinetics of protein from the HAp particles that adsorbed the protein (HAp-pro) was also evaluated in different pH solutions (pH 4.0 and 7.0). The released protein gradually increased time dependently when HAp-pro were immersed in pH 4.0 solution, but the released protein was significantly smaller when HAp-pro were immersed in pH 7.0 solution. Moreover, the release rate of protein from HAp-pro differed in each HAp that was synthesized at different temperatures, suggesting that the release of protein from HAp-pro depended on HAp resorption. These results suggest that HAp particles synthesized at different temperature are useful as a controlled release carrier of protein. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biomaterials.2003.10.081

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Language：English   Publisher：ELSEVIER SCI LTD  

This study examines the possibility of using hydroxyapatite (HAp) particles as a controlled release carrier of protein. In order to achieve effective protein release from HAp particles, it is necessary to regulate the conjugated amount of protein on HAp and the resorption of HAp. HAp particles were synthesized at different temperatures (40 degreesC, 60 degreesC, 80 degreesC) in wet condition and the physicochemical properties of synthesized HAp particles were examined. HAp particles synthesized at low temperatures showed low crystallinity, high solubility and large specific surface area. The useful growth factors for bone regeneration, such as BMP, bFGF and TGF-beta, are basic proteins, so cytochrome c (pI = 10.2) was used as a model protein and the adsorptive property of protein on HAp particles was investigated. The protein adsorption on HAp particles changed depending on its specific surface area and the chart of protein adsorption on HAp particles showed a typical Langmuir curve. These findings suggest that the adsorbed amount of protein on HAp particles could be regulated by HAp synthesizing temperature and the concentrations of protein solution. The release kinetics of protein from the HAp particles that adsorbed the protein (HAp-pro) was also evaluated in different pH solutions (pH 4.0 and 7.0). The released protein gradually increased time dependently when HAp-pro were immersed in pH 4.0 solution, but the released protein was significantly smaller when HAp-pro were immersed in pH 7.0 solution. Moreover, the release rate of protein from HAp-pro differed in each HAp that was synthesized at different temperatures, suggesting that the release of protein from HAp-pro depended on HAp resorption. These results suggest that HAp particles synthesized at different temperature are useful as a controlled release carrier of protein. (C) 2003 Elsevier Ltd. All rights reserved.

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Language：Japanese   Publisher：The Japanese Society for Dental Materials and Devices (JSDMD)  

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：INT AMER ASSOC DENTAL RESEARCHI A D R/A A D R  

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Language：English   Publisher：JOHN WILEY & SONS INC  

The aim of this study was to investigate the biodegradation of carbonate apatite (CO(3)Ap)/collagen composite membrane as a new guided tissue regeneration membrane in vivo and to estimate its controlled release of CO(3)Ap in vitro. To control the biodegradation of the guided tissue regeneration membrane and to promote hard tissue regeneration in the periodontal region, we added CO(3)Ap into the collagen membrane. To investigate the biodegradation of CO(3)Ap/collagen composite membranes, the prepared membranes (CO(3)Ap:0, 10 wt % ) were cut into 5 x 5 x 0.1 mm and subcutaneously implanted into the backside of male rats under general anesthesia. The explanted membranes were investigated histologically. To estimate their controlled release of CO(3)Ap in vitro, the membranes (CO(3)Ap 0-10 wt %, 5 x 5 x 0.1 mm) were immersed into collagenase solution and compulsorily dissolved for 48 h. Histological results suggested that the membrane had a good biocompatibility and the biodegradable period was shortened with the presence of CO(3)Ap. In the solubility experiments of the membrane, eluted Ca concentrations gradually increased with total dependence on the dissolution of the collagen membrane, Our study demonstrated that the biodegradation time can be controlled by CO(3)Ap contents in the membrane and CO(3)Ap could be released from the membrane with the biodegradation period, (C) 2002 Wiley Periodicals, Inc.

DOI： 10.1002/jbm.10133

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Language：English   Publisher：JOHN WILEY & SONS INC  

The aim of this study was to investigate the biodegradation of carbonate apatite (CO(3)Ap)/collagen composite membrane as a new guided tissue regeneration membrane in vivo and to estimate its controlled release of CO(3)Ap in vitro. To control the biodegradation of the guided tissue regeneration membrane and to promote hard tissue regeneration in the periodontal region, we added CO(3)Ap into the collagen membrane. To investigate the biodegradation of CO(3)Ap/collagen composite membranes, the prepared membranes (CO(3)Ap:0, 10 wt % ) were cut into 5 x 5 x 0.1 mm and subcutaneously implanted into the backside of male rats under general anesthesia. The explanted membranes were investigated histologically. To estimate their controlled release of CO(3)Ap in vitro, the membranes (CO(3)Ap 0-10 wt %, 5 x 5 x 0.1 mm) were immersed into collagenase solution and compulsorily dissolved for 48 h. Histological results suggested that the membrane had a good biocompatibility and the biodegradable period was shortened with the presence of CO(3)Ap. In the solubility experiments of the membrane, eluted Ca concentrations gradually increased with total dependence on the dissolution of the collagen membrane, Our study demonstrated that the biodegradation time can be controlled by CO(3)Ap contents in the membrane and CO(3)Ap could be released from the membrane with the biodegradation period, (C) 2002 Wiley Periodicals, Inc.

DOI： 10.1002/jbm.10133

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Language：English   Publisher：ELSEVIER SCI LTD  

Hydroxyapatite (HAp) was synthesized in the presence of a variety of amino acids in order to investigate the effect of amino acid on the crystallinity and the solubility characteristics of HAp in the HAp-synthesizing condition. In the results of X-ray diffraction analysis. HAp synthesized in the presence of glycine (HAp-Gly). serine (HAp-Ser). aspartic acid (HAp-Asp) and glutamic acid (HAp-Glu) showed poor crystallinity compared with HAp synthesized in the absence of amino acid (HAp-con). The results of Fourier transform infrared spectroscope suggested the adsorption of these amino acids on HAp. Scanning electron microphotographs showed that the size and morphology of HAp adsorbed amino acids changed significantly. Furthermore, the solubility of these HAps increased significantly compared to HAp-con, each differing in four amino acids, However. other amino acids did not affect the crystallinity and morphology of HAp and had no significant change in their solubility. Collectively. this study suggests that the crystallinity and the solubility of synthesized HAp are different owing to the, variation of amino acids in the HAp synthesizing condition. It is expected that digestion-regulated HAp materials could be synthesized by using amino acid in their synthesizing condition. (C), 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0142-9612(01)00358-1

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Language：English   Publisher：ELSEVIER SCI LTD  

Hydroxyapatite (HAp) was synthesized in the presence of a variety of amino acids in order to investigate the effect of amino acid on the crystallinity and the solubility characteristics of HAp in the HAp-synthesizing condition. In the results of X-ray diffraction analysis. HAp synthesized in the presence of glycine (HAp-Gly). serine (HAp-Ser). aspartic acid (HAp-Asp) and glutamic acid (HAp-Glu) showed poor crystallinity compared with HAp synthesized in the absence of amino acid (HAp-con). The results of Fourier transform infrared spectroscope suggested the adsorption of these amino acids on HAp. Scanning electron microphotographs showed that the size and morphology of HAp adsorbed amino acids changed significantly. Furthermore, the solubility of these HAps increased significantly compared to HAp-con, each differing in four amino acids, However. other amino acids did not affect the crystallinity and morphology of HAp and had no significant change in their solubility. Collectively. this study suggests that the crystallinity and the solubility of synthesized HAp are different owing to the, variation of amino acids in the HAp synthesizing condition. It is expected that digestion-regulated HAp materials could be synthesized by using amino acid in their synthesizing condition. (C), 2002 Elsevier Science Ltd. All rights reserved.

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