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

Zirconia ceramics have been widely used in dentistry. Herein, we assess the surface morphology, surface texture, and osteoblast response of additively manufactured zirconia and alumina-toughened zirconia (ATZ) in comparison with titanium. The surface roughness, contact angle, and surface microstructure of titanium sandblasted with large-grit alumina and subsequently acid-etched using 18% HCl and 49% H2SO4 (SLA-titanium), uniaxially pressed zirconia (UP zirconia), additively manufactured zirconia (AM zirconia), and additively manufactured ATZ (AM ATZ) were investigated. Moreover, the cell viability, alkaline phosphatase (ALP) activity, and gene expression of type I collagen on these materials were evaluated. The data were statistically analyzed using one-way ANOVA with Tukey's post hoc test. SLA-titanium showed the highest surface roughness and contact angle. The other three materials showed comparable surface roughness and contact angles. Micro- and nanoroughness were observed on the surface of SLA-titanium. UP zirconia and AM zirconia had similar surface morphologies. The cell viability, ALP activity, and gene expression of type I collagen on AM zirconia were comparable to or better than those on SLA-titanium. Our results indicate that AM zirconia is a promising material for zirconia dental implants.

DOI： 10.3390/ma15238685

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

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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

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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

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All-ceramic restorations have become increasingly popular in dentistry. Toward ensuring that these restorations adhere to the tooth structure, this study determines the optimal femtosecond laser (FL) treatment parameters for lithium disilicate glass-ceramics and highly translucent zirconia ceramics with respect to surface morphology. For both the ceramics, the following surface conditions were investigated: (1) as-sintered; (2) Al2O3 sandblasted; (3) FL treatment (dot pattern with line distances of 14, 20, and 40 µm); (4) FL treatment (crossed-line pattern with a line distance of 20 and 40 µm). Surface roughness parameters were estimated using a 3D confocal laser microscope; microstructures were analyzed using a scanning electron microscope. Peak fluence (Fpeak) values of 4 and 8 J/cm2 and irradiation numbers (N) of 20 and 10 shots were selected to create dot patterns in highly translucent zirconia and lithium disilicate glass-ceramics, respectively. Furthermore, Fpeak = 8 J/cm2 and N = 20 shots were chosen to obtain crossed-line patterns in both ceramics. Our results show that lithium disilicate glass-ceramics and highly translucent zirconia exhibit a similar surface morphology under each of the surface treatment conditions. Therefore, FL irradiation of dot or crossed-line patterns (at a distance of 20 and 40 µm) are potential candidates for future investigations.

DOI： 10.3390/ma15103614

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Inorganic pigments have been widely used due to their low cost of production, strong hiding power, and chemical resistance; nevertheless, they have limited hue width and chromaticity. To eliminate these disadvantages, we herein propose the use of an ingenious biotemplate technique to produce Al-enriched biogenic iron oxide (BIOX) materials. Spectrophotometric color analysis showed that high levels of Al inclusion on heat-treated BIOX samples produced heightened yellowish hues and lightness. The Al-enriched BIOX sheaths exhibited a stable tubular structure and excellent thermal stability of color tones after heating at high temperatures and repetitive heat treatments. Ultrastructural analysis and mechanical destruction experiments revealed that the highly chromatic orange-hue of these pigments are ascribed probably to an ingenious cylindrical nanocomposite architecture composed of putative Fe-included low crystalline Al oxide regions and hematite particles embedded therein. The present work therefore demonstrates that the bioengineered material can serve as an epochal orange-hued inorganic pigment with low toxicity and marked thermostability that should meet large industrial demand.

DOI： 10.1021/acsomega.1c07390

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

INTRODUCTION: Osteocytes play a role as mechanosensory cells by sensing flow-induced mechanical stimuli applied on their cell processes. High-resolution imaging of osteocyte processes and the canalicular wall are necessary for the analysis of this mechanosensing mechanism. Focused ion beam-scanning electron microscopy (FIB-SEM) enabled the visualization of the structure at the nanometer scale with thousands of serial-section SEM images. We applied machine learning for the automatic semantic segmentation of osteocyte processes and canalicular wall and performed a morphometric analysis using three-dimensionally reconstructed images. MATERIALS AND METHODS: Six-week-old-mice femur were used. Osteocyte processes and canaliculi were observed at a resolution of 2 nm/voxel in a 4 × 4 μm region with 2000 serial-section SEM images. Machine learning was used for automatic semantic segmentation of the osteocyte processes and canaliculi from serial-section SEM images. The results of semantic segmentation were evaluated using the dice similarity coefficient (DSC). The segmented data were reconstructed to create three-dimensional images and a morphological analysis was performed. RESULTS: The DSC was > 83%. Using the segmented data, a three-dimensional image of approximately 3.5 μm in length was reconstructed. The morphometric analysis revealed that the median osteocyte process diameter was 73.8 ± 18.0 nm, and the median pericellular fluid space around the osteocyte process was 40.0 ± 17.5 nm. CONCLUSION: We used machine learning for the semantic segmentation of osteocyte processes and canalicular wall for the first time, and performed a morphological analysis using three-dimensionally reconstructed images.

DOI： 10.1007/s00774-022-01321-x

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Other Link： https://link.springer.com/article/10.1007/s00774-022-01321-x/fulltext.html

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Nitrogen/phosphorus-containing melamines (NPCM), a durable flame-retardant, were prepared by the successive treatment of ArOH (Ar = Br n C6H5-n , n = 0, 1, 2, and 3) with POCl3 and melamine monomer. The prepared flame-retardants were grafted through the CH2 unit to lignocellulose nanofibers (LCNFs) by the Mannich reaction. The resulting three-component products were characterized using FT-IR (ATR) and EA. The thermal behavior of the NPCM-treated LCNF fabric samples was determined using TGA and DSC analyses, and their flammability resistances were evaluated by measuring their Limited Oxygen Index (LOI) and the UL-94V test. A multitude of flame retardant elements in the fabric samples increased the LOI values as much as 45 from 20 of the untreated LCNFs. Moreover, the morphology of both the NPCM-treated LCNFs and their burnt fabrics was studied with a scanning electron microscope (SEM). The heat release lowering effect of the LCNF fabric against the water-based paint was observed with a cone calorimeter. Furthermore, the mechanical properties represented as the tensile strength of the NPCM-treated LCNF fabrics revealed that the increase of the NPCM content in the PP-composites led to an increased bending strength with enhancing the flame-retardance.

DOI： 10.1039/d1ra08716a

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OBJECTIVES: The aim of this study was to evaluate the mechanical properties, bonding performance and anti-microbial activity of a novel composite cement containing cetylpyridinium chloride (CPC) modified montmorillonite ('CPC-Mont'), and using these parameters to determine the optimal particle size and concentration of CPC-Mont the composite cement can be loaded with. METHODS: CPC-Mont particles with a median diameter of 30 and 7 µm were prepared and added to a composite cement at a concentration of 2, 3, 4, 5 and 7.5 wt%. Mechanical properties and bonding performance of the experimental composite cements were evaluated by 3-point bending and micro-tensile bond-strength testing. The amount of CPC released from the cement disks was quantified using a UV-vis recording spectrophotometer. The anti-biofilm activity was studied using scanning electron microscopy (SEM). RESULTS: Adding 30-μm CPC-Mont decreased the mechanical properties and bonding performance of the composite cement, while no reduction was observed for the 7-μm CPC-Mont loaded cement formulation. Although CPC release substantially decreased during the 7-day period assessed, 5- and 7.5-wt% CPC-Mont loaded composite cement inhibited biofilm formation for 30 days. SIGNIFICANCE: Loading composite cement with CPC-Mont with a median diameter of 7 µm at concentrations of 5-7.5 wt% was effective in achieving continuous anti-biofilm activity, while maintaining mechanical strength and bonding performance.

DOI： 10.1016/j.dental.2021.10.009

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

Pathological mineralization, such as that in atherosclerosis or following transplantation of biomaterials, is associated with millions of deaths worldwide. A deeper understanding of the mechanisms underlying mineral nucleation in pathological mineralization will facilitate the development of novel bioinspired materials/techniques as therapeutics for either disease prevention or bone tissue reconstruction. The objective of this study was to perform a systematic and ultrastructural analysis of the nucleation sites of atherosclerotic mineralization from the viewpoint of material science. Histological staining, ultrastructural analysis, and selected area elemental mapping of human atherosclerotic tissues revealed two different nucleation sites in a collagenous and a lipidic area, respectively, comprising phospholipidic large vesicles (average 827 +/- 470 nm) and non-vesicular phospholipids. In both sites, the initial minerals were identified to be amorphous calcium phosphate (ACP), which then transformed into hydroxyapatite (HAp). Mineralization assays in vitro was performed by incubating non-vesicular low- (LDL) and high- (HDL) density lipoprotein and cholesterol in 2 mM CaCl2 for 2 days, without additional phosphate. Calcium ions in the formed minerals, measured using atomic absorption (AA) spectroscopy, showed that only LDL was mineralized. We then evaluated the mineralization of the major phospholipids, phosphatidylserine (PS) and phosphatidylcholine (PC) under the same conditions. The results of AA and mineral dry weight showed that PS was more abundantly mineralized than PC, most likely due to its higher hydrolysis rate. Similar to the in vivo findings, PS mineralization initially formed ACP, which then crystallized into HAp. Taken together, these results indicated that atherosclerosis involves two distinct nucleation sites and that non-vesicular phospholipids were one of the major nucleation sites for atherosclerotic mineral formation.

DOI： 10.1039/d1ma00273b

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

X-ray diffraction (XRD) surface analysis and ultrastructural interfacial characterization using transmission electron microscopy (TEM) confirmed that the functional monomer 10–methacryloyloxydecyl dihydrogen phosphate (10-MDP) self-assembles into nano-layers at adhesive-tooth interfaces. Self-assembled nano-layering is thought to contribute to the durability of bonding to tooth dentin, although this has not been proven yet. In order to disclose this potential bond-durability contribution of nano-layering, we observed the 3-dimensional (3D) spreading of nano-layering by a series of focused-ion-beam (FIB) milled cross sections by scanning electron microscopy (FIB-SEM) and examined the mechanical properties of self-assembled nano-layering using scanning probe microscopy (SPM). A commercial 10-MDP-containing 3-step self-etch adhesive partially demineralized dentin up to submicron depth, forming a submicron hydroxyapatite-rich hybrid layer. TEM chemically and ultrastructurally confirmed the formation of interfacial nano-layering. FIB-SEM 3D reconstructions disclosed a 3D network of self-assembled nano-layering extending from the hybrid layer up to within the adjacent adhesive-resin layer. SPM revealed that nano-layering within the adhesive-resin layer possessed a higher elastic modulus than that of the surrounding adhesive resin, hereby suggesting that nano-layering contributes to the mechanical strength of adhesives like filler particles do. Nano-layering’s 3D expanded structure is expected to strengthen the surrounding resin, as well to better interconnect the adhesive-resin layer to the hybrid layer. In conclusion, this exploratory study demonstrated that nano-layering constitutes a strong phase at the adhesive interface, which may contribute to the clinical longevity of the 10-MDP-based bond to dentin.

DOI： 10.1177/0022034520979133

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Other Link： http://journals.sagepub.com/doi/full-xml/10.1177/0022034520979133

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

PURPOSE: To evaluate effect of air-particle abrasion protocol and primer on surface topography and bond strength of resin cement to high-translucent zirconia ceramics. MATERIALS AND METHODS: Two hundred disk-shaped high-translucent zirconia specimens of 5Y-PSZ were prepared. The specimens were assigned to 5 groups in terms of particle type and air-particle abrasion pressure: (1) control, (2) alumina with 0.2 MPa-air pressure [AB-0.2], (3) alumina with 0.4 MPa-air pressure [AB-0.4], (4) glass beads with 0.2 MPa-air pressure [GB-0.2], and (5) glass beads with 0.4 MPa-air pressure [GB-0.4]. Two different primers 1% MDP (Experimental) and MDP-silane primer (Clearfil Ceramic Primer Plus) was also tested. Stainless steel rods were bonded to the 5Y-PSZ specimens with PANAVIA V5. For each group, the tensile bond strength (TBS) was measured after 24-hour water storage (n = 10) and after 5000 thermal-cycling (n = 10) at crosshead speed of 2 mm/min. The data were statistically analyzed using Weibull analysis. Surface roughness (Sa) was measured using a 3D-Laser Scanning Confocal Microscope (n = 5) and analyzed by t-test with Bonferroni correction. Surface topography using scanning electron microscopy (SEM) and surface elemental analysis using energy dispersion spectroscopy (EDX), and cross-section SEM at the interface with composite cement were also investigated. RESULTS: In MDP-silane groups, the highest TBS was observed in AB-0.4 after 24 hours and GB-0.4 after thermal-cycling (p < 0.05). In MDP groups, AB groups resulted in the significantly higher TBS than GB groups (p < 0.05). AB-0.4 group showed the highest Sa value compared to all groups (p < 0.005), meanwhile GB groups did not show different Sa compared to control (p > 0.005). CONCLUSION: Air-abrasion with different particle and blasting pressure can improve bonding to zirconia with proper primer selection. Particularly, glass beads abrasion followed by MDP-silane primer and alumina abrasion followed by MDP primer alone provided stable bond strength of resin cement to high-translucent zirconia after aging. High-translucent zirconia abraded with glass beads achieves a desirable bonding performance without creating surface microcracks which may hinder zirconia's mechanical properties.

DOI： 10.1111/jopr.13372

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

This study aimed to investigate whether inorganic elements of polymer-infiltrated ceramic (PIC) and microfilled resin (MFR) for CAD/CAM would affect initial bond strength to luting agent. Inorganic elements of PIC and MFR were different with shape and ingredient observed by SEM, STEM and EDS. Microtensile bond strengths (µTBS) value of PIC was increased by 10-methacryloyloxydecyl dihydrogen phosphate (MDP) and acetic acid (AA)- or MDP-activated silane treatment, and further increased by succeeding heat treatment (HT). The µTBS of MFR was increased by MDP and MDP-activated silane, but decreased by AA-activated silane without HT. The HT improved the µTBS of MFR with AA-activated silane, but conversely for MDP-activated silane. Only in MFR, phosphoric acid (PA) application before each surface treatment dramatically decreased the µTBS of AA-activated silane. FTIR peaks in MFR shifted according to phosphate group's peak. MFR would possess high phosphate group adsorption capacity, with MDP effectively improving its bonding capability.

DOI： 10.4012/dmj.2020-029

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Mary Ann Liebert Inc  

Bone regeneration was one of the earliest fields to develop in the context of tissue regeneration, and currently, repair of small-sized bone defects has reached a high success rate. Future researches are expected to incorporate more advanced techniques toward achieving rapid bone repair and modulation of the regenerated bone quality. For these purposes, it is important to have a more integrative understanding of the mechanisms of bone formation and maturation from multiple perspectives and to incorporate these new concepts into the development and designing of novel materials and techniques for bone regeneration. This review focuses on the analysis of the earliest stages of bone tissue development from the biology, material science, and engineering perspectives for a more integrative understanding of bone formation and maturation, and for the development of novel biology-based engineering approaches for tissue synthesis in vitro. More specifically, the authors describe the systematic methodology that allowed the understanding of the different nucleation sites in intramembranous and endochondral ossification, the space-making process for mineral formation and growth, as well as the process of apatite crystal cluster growth in vivo in the presence of suppressing biomolecules.Impact StatementA detailed understanding of the developmental process of bone tissue leads to the acquisition of useful information for the bone tissue fabrication. This review summarizes the study of the calcification process of the calvaria and epiphyses from an engineering perspective and provides useful information for the realization of bone tissue biofabrication. Here, we describe the new mechanism of space formation for mineralization such as rupture of chondrocytes and disruption of cell-cell adhesion. We also describe the roles of nucleation site such as cell membrane nanofragments and matrix vesicles.

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

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

Ceramic restorations are often adhesively luted onto the tooth prep. The so-called touch-cure concept was developed to yield optimum polymerization of composite cement at the restoration-cement-tooth interface for immediate bond stabilization. Although this touch cure is theorized to initiate polymerization at the interface when the accelerator in the primer makes contact with the cement, this process has not yet been proven. This study aimed to elucidate the mechanism of touch cure by measuring the degree of conversion (DC) of composite cement applied with or without an accelerator-containing tooth primer (TP) versus an accelerator-free primer using real-time Fourier-transform infrared spectroscopy (RT-FTIR) and attenuated total reflection (ATR)–FTIR. Interfacial bond strength was measured in shear mode, the accelerator composition confirmed by X-ray fluorescence analysis (XRF), and the interfacial interaction of TP and composite cement with dentin investigated by X-ray diffraction (XRD), focused-ion-beam scanning electron microscopy (FIB-SEM) with 3-dimensional interface reconstruction, and transmission electron microscopy (TEM). RT/ATR-FTIR revealed the significantly highest DC when the composite cement was applied with the accelerator-containing primer. XRF disclosed a vanadium compound as a novel chemical accelerator within TP, instead of a classic chemical curing initiator system, to set off touch cure as soon the cement contacts the previously applied primer. Although the TP contains the acidic functional monomer 10-MDP for adhesion to tooth tissue, touch cure using the accelerator-containing TP combined the fastest/highest DC with the highest bond strength. FIB-SEM and TEM confirmed the tight interfacial interaction at dentin with submicron hybridization along with stable 10-MDP also Ca-salt nanolayering.

DOI： 10.1177/00220345211001020

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Other Link： http://journals.sagepub.com/doi/full-xml/10.1177/00220345211001020

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

Several dental materials contain silver for antibacterial effect, however the effect is relatively low. The reason for the lower antibacterial efficacy of silver is considered to be the fact that silver ions bind to chloride ions in saliva. To develop new effective silver antibacterial agents that can be useful in the mouth, we synthesized two novel amino acid (methionine or histidine)-silver complexes (Met or His-Ag) loaded with montmorillonite (Mont) and analyzed their antibacterial efficacy. At first the complexes were characterized using nuclear magnetic resonance (NMR), and amino acid-Ag complex-loaded Mont (amino acid-Ag-Mont) were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The antibacterial efficacy of these materials in dental acrylic resin was then investigated by bacterial growth measurement using a spectrophotometer. As controls, commercially available silver-loaded zeolite and silver-zirconium phosphate were also tested. Dental acrylic resin incorporating His-Ag-Mont strongly inhibited Streptococcus mutans growth. This was explained by the fact that His-Ag complex revealed the highest amounts of silver ions in the presence of chloride. The structure of the amino acid-Ag complexes affected the silver ion presence in chloride and the antibacterial efficacy. His-Ag-Mont might be used as antibacterial agents for dental materials.

DOI： 10.3390/ma14061442

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

DOI： 10.26502/acbr.50170191

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

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

OBJECTIVES: To synthesize and characterize brushite particles in the presence of acidic monomers (acrylic acid/AA, citric acid/CA, and methacryloyloxyethyl phosphate/MOEP) and evaluate the effect of these particles on degree of conversion (DC), flexural strength/modulus (FS/FM) and ion release of experimental composites. METHODS: Particles were synthesized by co-precipitation with monomers added to the phosphate precursor solution and characterized for monomer content, size and morphology. Composites containing 20 vol% brushite and 40 vol% reinforcing glass were tested for DC, FS and FM (after 24 h and 60 d in water), and 60-day ion release. Data were subjected to ANOVA/Tukey tests (DC) or Kruskal-Wallis/Dunn tests (FS and FM, alpha: 5%). RESULTS: The presence of acidic monomers affected particle morphology. Monomer content on the particles was low (0.1-1.4% by mass). Composites presented similar DC. For FS/24 h, only the composite containing DCPD_AA was statistically similar to the composite containing 60 vol% of reinforcing glass (without brushite, "control"). After 60 days, all brushite-containing materials showed similar FS, statistically lower than the control composite (p<0.01). Composites containing DCPD_AA, DCPD_MOEP or DCPD_U ("unmodified") showed statistically similar FM/24 h, higher than the control composite. After prolonged immersion, all composites were similar to the control composite, except DCPD_AA. Cumulative ion release ranged from 21 ppm to 28 ppm (calcium) and 9 ppm to 17 ppm (phosphate). Statistically significant reductions in ion release between 15 and 60 days were detected only for the composite containing DCPD_MOEP. SIGNIFICANCE: Acidic monomers added to the synthesis affected brushite particle morphology. After 60-day storage in water, composite strength was similar among all brushite-containing composites. Ion release was sustained for 60 days and it was not affected by particle morphology.

DOI： 10.1016/j.msec.2020.111178

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Naturally occurring tubular iron oxides produced by aquatic bacteria in Leptothrix spp. are promising raw materials for hematite-based red pigments because of the higher heat resistance as compared with chemically synthesized hematite compounds. Here, we report iron oxide red pigments prepared through an additive deposition of aluminum on culture-based biogenous iron oxide (cBIOX) sheaths using an artificial culture system of L. cholodnii strain OUMS1. The heat-treated Al-containing cBIOXs exhibited elevated chroma and lightness along with increasing Al contents and enhanced thermal stability of color tones to repetitive heat treatments. XRD analysis showed a monophasic pattern of hematite in the Al-rich cBIOX after heating at a wide range of high temperatures. Micromorphology analyses revealed that putative Al oxide regions present among hematite particles plausibly prevented the grain growth of hematite during heat treatments. The results therefore demonstrate that the bioderived Al-rich iron oxide sheaths can serve as innovative inorganic red pigments feasible for industrial applications.

DOI： 10.1021/acsabm.0c00476

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

OBJECTIVE: Hydrofluoric-acid etching followed by silanization is a routine clinical protocol for durable bonding to glass ceramics. Simplifying ceramic-bonding procedures, new technological developments involve the inclusion of a silane coupling agent in a self-adhesive composite cement. To investigate the effectiveness of the incorporated silane coupling agent, shear bond strength (SB) to ceramic and dentin, contact angle of water (CA), transmission electron microscopy (TEM), X-ray diffraction (XRD) and 29Si nuclear magnetic resonance (NMR) assessments were correlatively conducted. MATERIALS AND METHODS: SB to glass ceramic was measured without ('immediate') and with ('aged') 50K thermocycles upon application of (1) the silane-containing self-adhesive composite cement Panavia SA Cement Universal ('SAU'), being light-cured: 'SAU_light', (2) 'SAU_chem': chemically cured SAU, (3) 'SAP_light': light-cured Panavia SA Cement Plus ('SAP'), and (4) 'SAP_CP': SAP light-cured after separate silanization using Clearfil Ceramic Primer Plus ('CP'). CA was also measured on glass ceramic. The cement pastes before and upon mixing were characterized using 29Si NMR. SB of SAU or SAP onto dentin was measured. Finally, the cement-dentin interface was characterized by TEM and XRD. RESULTS: The immediate and aged SB to glass ceramic of SAU did not significantly differ from those of SAP_CP, while they were significantly higher than those of SAP. CA of SAU did not significantly differ from that of SAP_CP, but it was significantly higher than CA of SAP. 29Si NMR revealed siloxane bonds after mixture. SB of SAU and SAP to dentin did not show any significant difference. SEM, TEM and XRD confirmed tight and chemical interaction, respectively. SIGNIFICANCE: Incorporating silane in a 10-MDP-based self-adhesive composite cement combined efficient silane-coupling ability at the ceramic surface with effective bonding ability at dentin.

DOI： 10.1016/j.dental.2020.04.014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Several studies have shown the clinical success of hydraulic calcium-silicate cements (hCSCs) for direct and indirect pulp capping and root repair.</p>

DOI： 10.1039/d0tb00079e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

The remineralization mechanism in dental caries lesions is not completely understood. This study reports on ultrastructural and chemical changes observed within arrested caries lesions. Carious human teeth were observed using scanning electron microscopy (SEM) and focused-ion-beam (FIB)-SEM. The crystals detected in the caries lesions were characterized by transmission electron microscopy (TEM), along with chemical element mapping using energy-dispersive spectroscopy (EDS)-STEM. FIB-SEM 3D reconstructions revealed a severely damaged dentin surface abundantly covered by bacteria. Although the dentin tubules were clogged up to a depth of 100 μm, bacterial invasion into dentin tubules was not observed. TEM crystal analysis and EDS-STEM revealed the presence of Ca and P, as well as of Mg within the HAp crystals deposited inside the dentin tubules. It was concluded that extensive remineralization with deposition of Mg-HAp crystals had occurred in dentin tubules of caries-arrested dentin. Understanding the natural remineralization process is thought to be helpful for developing clinical biomimetic remineralization protocols.

DOI： 10.1038/s41598-020-61111-1

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Other Link： http://www.nature.com/articles/s41598-020-61111-1

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

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

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Other Link： http://journals.sagepub.com/doi/full-xml/10.1177/2280800020942717

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

Long-term anti-bacterial effect is a desired ability of any dental material in combating tooth caries as one of the most common and widespread persistent diseases today. Among several cationic quaternary ammonium compounds with antiseptic properties, cetylpyridinium chloride (CPC) is often used in mouthrinses and toothpastes. In this study, we incorporated CPC in a soft phyllosilicate mineral (clay), referred to as montmorillonite (Mont), to enable gradual CPC release with rechargeability. Besides measuring CPC release and recharge, we examined the anti-bacterial effect, cytotoxicity and bonding effectiveness of five experimental adhesive formulations, prepared by adding 1 and 3 wt% CPC_Mont, 3 wt% Mont (without CPC), and 1 and 3 wt% CPC (without Mont) to the commercial adhesive Clearfil S3 Bond ND Quick ('C-S3B'; Kuraray Noritake). Strong inhibition of Streptococcus mutans biofilm formation by CPC_Mont adhesives was confirmed by optical density and SEM. CPC release from CPC_Mont adhesives was higher and lasted longer than from CPC adhesives, while CPC_Mont adhesives could also be recharged with CPC upon immersion in 2 wt% CPC. In conclusion, CPC_Mont technology rendered adhesives anti-bacterial properties with recharge ability, this without reducing its bonding potential, neither increasing its cytotoxicity. STATEMENT OF SIGNIFICANCE: Dental caries is one of the most prevalent chronic diseases in the population worldwide and is the major cause of tooth loss. In this study, we developed cetylpyridinium chloride (CPC) loaded montmorillonite (CPC-Mont) with a long-term antibacterial efficacy to prevent caries. CPC is an antibacterial agent approved by FDA, used as an OTC drug and contained in oral hygiene aids. CPC-Mont was incorporated in a dental adhesive to gradually release CPC. CPC_Mont technology rendered adhesives anti-bacterial properties with rechargeability, this without reducing its bonding potential, neither increasing its cytotoxicity.

DOI： 10.1016/j.actbio.2019.09.045

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

The functional monomer 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), used in many dental adhesives, self-assembles in nano-layers at adhesive-tooth interfaces. Recently, several states of the POH groups of 10-MDP_Ca salts were suggested, while their actual status has not been elucidated yet. We mechanistically investigated 10-MDP_Ca-salt nano-layering at adhesive-dentin interfaces, correlatively using scanning transmission electron microscopy with energy-dispersive X-ray spectrometry (STEM-EDS), X-ray diffraction (XRD) and solid state nuclear magnetic resonance (NMR). STEM-EDS confirmed the presence of Ca and P in each nano-layer. Both XRD and NMR revealed that the two terminal POH groups of 10-MDP reacted with Ca. This twofold POH interaction of 10-MDP with Ca was stable in water and is therefore expected to contribute to durable nano-layering of 10-MDP_Ca salts in the hybrid and adhesive layer. STATEMENT OF SIGNIFICANCE: The functional monomer 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), commonly used in dental adhesives with favorable long-term clinical outcome, has been documented to self-assemble into nano-layers at adhesive-tooth interfaces. Characterizing ultra-morphologically (STEM) and chemically (STEM-EDS, XRD, NMR) the mechanisms of interaction of 10-MDP with bulk dentin in a similar manner as what occurs clinically, it was found that the water stable 10-MDP_Ca salts consist of CaRPO4, meaning that the two OH groups of the phosphate group of 10-MDP ionically reacted with Ca. This stable structure is expected to contribute to durable nano-layering of 10-MDP_Ca salts in the hybrid and adhesive layer and hence to clinical longevity of the adhesively bonded tooth restoration.

DOI： 10.1016/j.actbio.2019.08.029

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

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

Tribochemical silica coating (TSC) is commonly used to pretreat zirconia surfaces prior to luting. Although many studies demonstrate an adhesion-promoting effect of TSC on zirconia, its actual interaction mechanism has not been fully elucidated. We therefore characterized the ultrastructure of TSC-treated zirconia and tested shear-bond strength. STEM/EDS disclosed a micro-roughened zirconia surface partially covered with fused Al and Si, while residual unfused silica particles could also still be detected. TSC-treated zirconia having received the solely silane primer exhibited a significantly lower shear-bond strength than zirconia on which the combined 10-MDP/silane primer was applied. SEM fracture analysis revealed residual silica particles on both the zirconia and cement sides. Correlative ultrastructural and chemical surface characterization revealed that TSC deposited an inhomogeneous silica layer on the zirconia surface, which explains why the solely silane coupling agent was less effective than the combined 10-MDP/silane ceramic primer for bonding to zirconia pretreated by TSC.

DOI： 10.4012/dmj.2017-397

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

This study presents a new strategy for preparing highly oriented nanorod array of divalent ion substituted hydroxyapatite (HAp) and factors controlling the rate of glass conversion. HAp nanorod arrays were prepared on a series of alkali/alkaline-earth silicate glasses in the Na2O-CaO-SrO-SiO2 system in phosphate aqueous solutions with different pH values via a glass conversion process. The effects of the substitution of Sr2+ for Ca2+ and the network connectivity (NC) of the silicate glasses on the degree of crystal orientation of the nanorod array of HAp crystals, the crystallite size, and the partial substitution of Sr2+ for Ca2+ in the HAp crystal lattice were investigated using X-ray diffraction, Si-29 magic angle spinning nuclear magnetic resonance (NMR) spectroscopy, and field-emission scanning electron microscopy. Sr-free Na2O-CaO-SiO2 glass was converted into HAp nanorod arrays highly-oriented toward the c-axis, whereas the increase in the NC of the glass led to a decrease in the rate of the conversion process from glass to HAp, which resulted in the reduction of the degree of c-axis orientation of the nanorod array of the HAp crystals. However, the rate of the conversion process was remarkably promoted in alkaline phosphate solutions, resulting in an increase of the degree of c-axis orientation of the nanorod array. The Sr/(Sr + Ca) molar fraction of silicate glasses determined the molar fraction of substituted Sr2+ in HAp crystal lattice.

DOI： 10.1016/j.ceramint.2018.07.101

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

OBJECTIVES: Although the functional monomer glycero-phosphate dimethacrylate (GPDM) has since long been used in several dental adhesives and more recently in self-adhesive composite cements and restoratives, its mechanism of chemical adhesion to hydroxyapatite (HAp) is still unknown. We therefore investigated the chemical interaction of GPDM with HAp using diverse chemical analyzers and ultra-structurally characterized the interface of a GPDM-based primer formulation with dentin. METHODS: HAp particles were added to a GPDM solution for various periods, upon which they were thoroughly washed with ethanol and water prior to being air-dried. As control, 10-methacryloyloxydecyl dihydrogen phosphate (MDP) was used. The molecular interaction of GPDM with HAp was analyzed using X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (NMR) spectroscopy. Crystal formation upon application of GPDM onto dentin was analyzed using thin-film XRD (TF-XRD). Its hydrophobicity was measured using contact-angle measurement. The interaction of GPDM with dentin was characterized using transmission electron microscopy (TEM). RESULTS: XRD revealed the deposition of dicalcium phosphate dihydrate (DCPD: CaHPO4·2H2O) on HAp after 24h. NMR confirmed the adsorption of GPDM onto HAp. However, GPDM was easily removed after washing with water, unlike MDP that remained adhered to HAp. Dentin treated with GPDM appeared more hydrophilic compared to dentin treated with MDP. TEM disclosed exposed collagen in the hybrid layer produced by the GPDM-based primer formulation. SIGNIFICANCE: Although GPDM adsorbed to HAp, it did not form a stable calcium salt. The bond between GPDM and HAp was weak, unlike the strong bond formed by MDP to HAp. Due to its high hydrophilicity, GPDM might be an adequate monomer for an etch-and-rinse adhesive, but appears less appropriate for a 'mild' self-etch adhesive that besides micro-retention ionically interacts with HAp, or for a self-adhesive restorative material.

DOI： 10.1016/j.dental.2018.04.003

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Language：Japanese   Publisher：(一社)日本骨代謝学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Inc.  

Objective: To assess the influence of alumina sandblasting on four highly translucent dental zirconia grades. Methods: Fully sintered zirconia disk-shaped specimens (15-mm diameter
0.5-mm thickness) of four highly translucent yttria partially stabilized zirconia (Y-PSZ) grades (KATANA HT, KATANA STML, KATANA UTML, Kuraray Noritake
Zpex Smile, Tosoh) were sandblasted with 50-μm alumina (Al2O3) sand (Kulzer) or left ‘as-sintered’ (control) (n = 5). For each zirconia grade, the translucency was measured using a colorimeter. Surface roughness was assessed using 3D confocal laser microscopy, upon which the zirconia grades were statistically compared for surface roughness using a Kruskal–Wallis test (n = 10). X-ray diffraction (XRD) with Rietveld analysis was used to assess the zirconia-phase composition. Micro-Raman spectroscopy was used to assess the potentially induced residual stress. Results: The translucency of KATANA UTML was the highest (36.7 ± 1.8), whereas that of KATANA HT was the lowest (29.5 ± 0.9). The ‘Al2O3-sandblasted’ and ‘as-sintered’ zirconia revealed comparable surface-roughness Sa values. Regarding zirconia-phase composition, XRD with Rietveld analysis revealed that the ‘as-sintered’ KATANA UTML contained the highest amount of cubic zirconia (c-ZrO2) phase (71 wt%), while KATANA HT had the lowest amount of c-ZrO2 phase (41 wt%). KATANA STML and Zpex Smile had a comparable zirconia-phase composition (60 wt% c-ZrO2 phase). After Al2O3-sandblasting, a significant amount (over 25 wt%) of rhombohedral zirconia (r-ZrO2) phase was detected for all highly translucent zirconia grades. Significance: Al2O3-sandblasting did not affect the surface roughness of the three highly translucent Y-PSZ zirconia grades, but it changed its phase composition.

DOI： 10.1016/j.dental.2017.12.008

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

Biomineralization involves complex processes and interactions between organic and inorganic matters, which are controlled in part by the cells. The objectives of this study were, first, to perform a systematic and ultrastructural investigation of the initial mineral formation during secondary ossification center of mouse femur based on material science and biology viewpoint, and then develop novel biomaterials for mineralization based on the in vivo findings. First, we identified the very initial mineral deposition at postnatal day 5 (P5) at the medial side of femur epiphysis by nanocomputed tomography. Initial minerals were found in the surroundings of hypertrophic chondrocytes. Interestingly, histological and immunohistochemical analyses showed that initial mineralization until P6 was based on chondrocyte activity only, i.e., it occurred in the absence of osteoblasts. Moreover, electron microscopy-based ultrastructural analysis showed that cell-secreted matrix vesicles were absent in the early steps of osteoblast-independent endochondral ossification. Instead, chondrocyte membrane nanofragments were found in the fibrous matrix surrounding the hypertrophic chondrocytes. EDS analysis and electron diffraction study indicated that cell membrane nanofragments were not mineralized material, and could be the nucleation site for the newly formed calcospherites. The phospholipids in the cell membrane nanofragments could be a source of phosphate for subsequent calcium phosphate formation, which initially was amorphous, and later transformed into apatite crystals. Finally, artificial cell nanofragments were synthesized from ATDC5 chondrogenic cells, and in vitro assays showed that these nanofragments could promote mineral formation. Taken together, these results indicated that cell membrane nanofragments were the nucleation site for mineral formation, and could potentially be used as material for manipulation of biomineralization.

DOI： 10.1021/acsbiomaterials.7b00962

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

OBJECTIVE: To assess light irradiance (LI) delivered by two light-curing units (LCU's) and to measure the degree of conversion (DC) of three composite cements, when cured through different thicknesses of two novel CAD-CAM block materials. METHODS: 100-μm-thick films of a dual-curable composite cement (G-CEM LinkAce, GC), a light-curable flowable resin-based composite (RBC) (G-ænial Universal Flo, GC) and a micro-hybrid RBC (G-ænial Posterior, GC) were investigated as luting agents. Two 'polymer-ceramic' CAD-CAM blocks (Cerasmart, GC; Enamic, Vita Zahnfabrik) were sectioned in slabs with different thicknesses (1, 3 and 5mm). LI at the bottom of the specimens was measured using a calibrated spectrometer, while being light-cured through the CAD-CAM block slabs for 40s with a low- (±500mW/cm2) or high- (±1,600mW/cm2) irradiance LCU (n=5). After light-curing, micro-Raman spectra of the composite films were acquired to determine DC at 5min, 10min, 1h and 24h. LI data were statistically analyzed by Kruskal-Wallis followed by post-hoc comparisons, while a linear mixed-effect model was applied for the DC analysis. In addition, the CAD-CAM blocks ultrastructure was characterized upon argon-ion slicing using scanning transmission electron microscopy (STEM). Finally, light transmission (LT) through each CAD-CAM block material was assessed using a spectrophotometer. RESULTS: Curing-light attenuation and DC were significantly influenced by thickness and type of the overlying material. LCU only had a significant effect on DC of the micro-hybrid RBC. DC significantly increased over time for all composite cements. CAD-CAM block structural analysis revealed a relatively small and homogenous filler configuration (mean filler size of 0.2-0.5μm) for Cerasmart, while Enamic contained ceramic grains varying in shape and size (1-10μm), which were interconnected by the polymer-based network. LT was much higher at a wavelength range of 300-800nm for Cerasmart than for Enamic. SIGNIFICANCE: Light-curable composite cements can be cured through a restoration up to 2.7-mm thickness, depending on the kind of CAD-CAM material. A high-irradiance LCU only has a limited effect on the maximum thickness of the polymer-ceramic CAD-CAM material that can be cured through.

DOI： 10.1016/j.dental.2017.11.008

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

Analysis of tissue development from multidisciplinary approaches can result in more integrative biological findings, and can eventually allow the development of more effective bioengineering methods. In this study, we analyzed the initial steps of mineral formation during secondary ossification of mouse femur based on biological and bioengineering approaches. We first found that some chondrocytes burst near the mineralized area. External factors that could trigger chondrocyte burst were then investigated. Chondrocyte burst was shown to be modulated by mechanical and osmotic pressure. A hypotonic solution, as well as mechanical stress, significantly induced chondrocyte burst. We further hypothesized that chondrocyte burst could be associated with space-making for mineral expansion. In fact, ex vivo culture of femur epiphysis in hypotonic conditions, or under mechanical pressure, enhanced mineral formation, compared to normal culture conditions. Additionally, the effect of mechanical pressure on bone formation in vivo was investigated by immobilization of mouse lower limbs to decrease the body pressure onto the joints. The results showed that limb immobilization suppressed bone formation. Together, these results suggest chondrocyte burst as a novel fate of chondrocytes, and that manipulation of chondrocyte burst with external mechano-chemical stimuli could be an additional approach for cartilage and bone tissue engineering.

DOI： 10.1039/c7ib00130d

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DOI： 10.1177/0022034518763606

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

The collagen network acts as a scaffold for calcification and its three-dimensional structure influences bone strength. It is therefore important to observe the collagen network in detail and three-dimensionally. In this study, we observed the collagen network of chick embryonic calvariae in membranous bone three-dimensionally using orthogonally arranged FIB-SEM. A 25 x 25 mm area of chick embryonic calvaria was observed at a high resolution (25 nm per pixel). The inside of the bone (i.e. the primary calcified tissue), the bone cells (i.e. the osteoblasts and the osteocytes), the organelles, and the collagen fibrils were observed in detail. These structures were observed three-dimensionally using the Amira software program. In addition, the collagen fibrils of the bone were automatically extracted using the XTracing extension software program, and three-dimensional morphometry was performed. Almost all of the collagen fibrils ran along the longitudinal axis of the trabecular bone. We found that the regularity of the collagen fibril orientation was less remarkable in the osteoblast layer, which contained numerous osteoblasts. The collagen fibril orientation started to show regularity toward the central bone layer, which contained few bone cells.

DOI： 10.1039/c7ib00073a

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

Leptothrix species produce microtubular organic-inorganic materials that encase the bacterial cells. The skeleton of an immature sheath, consisting of organic exopolymer fibrils of bacterial origin, is formed first, then the sheath becomes encrusted with inorganic material. Functional carboxyl groups of polysaccharides in these fibrils are considered to attract and bind metal cations, including Fe(III) and Fe(III)-mineral phases onto the fibrils, but the detailed mechanism remains elusive. Here we show that NH2 of the amino-sugar-enriched exopolymer fibrils is involved in interactions with abiotically generated Fe(III) minerals. NH2-specific staining of L. cholodnii OUMS1 detected a terminal NH2 on its sheath skeleton. Masking NH2 with specific reagents abrogated deposition of Fe(III) minerals onto fibrils. Fe(III) minerals were adsorbed on chitosan and NH2-coated polystyrene beads but not on cellulose and beads coated with an acetamide group. X-ray photoelectron spectroscopy at the N1s edge revealed that the terminal NH2 of OUMS1 sheaths, chitosan and NH2-coated beads binds to Fe(III)-mineral phases, indicating interaction between the Fe(III) minerals and terminal NH2. Thus, the terminal NH2 in the exopolymer fibrils seems critical for Fe encrustation of Leptothrix sheaths. These insights should inform artificial synthesis of highly reactive NH2-rich polymers for use as absorbents, catalysts and so on.

DOI： 10.1038/s41598-017-06644-8

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

Objective. Bioactive glasses and surface pre-reacted glass-ionomer (sPRG) filler possess cario-static properties owing to ion release. Many studies investigated potential cariostatic effects; few studies evaluated the surface stability and the structural changes their surfaces undergo in acidic conditions.
Methods. The surface resistance against acid attack and the surface receptiveness for bacterial adhesion and biofilm formation of a sPRG-filled (Beautifil ll, Shofu) and conventional glass-filled (Herculite XRV Ultra, Kerr) resin-based composite (RBC), and a conventional glass-ionomer cement (GIC; Fuji IX GP Extra, GC) were examined. Specimens (n = 3) were immersed in distilled water or lactic acid (pH 4.0) for 3 days. Bacterial growth and biofilm formation were recorded using optical density and SEM.
Results. Upon 3-day immersion in lactic acid, the surface of the sPRG-filled RBC revealed multiple holes, while virtually no change in surface integrity was observed for the conventional RBC and GIC. Bacterial growth measurements revealed that none of the materials inhibited Streptococcus mutans (p&lt;0.05). Remarkably, cross-sectional SEM revealed that S. mutans had penetrated the etch pits induced by lactic acid in/around the sPRG filler. Ion-release measurements revealed that sPRG-filled RBC released boron and fluoride, while GIC only released fluoride. However, the concentration of ions released by both materials appeared not sufficient to inhibit bacterial growth. Moreover, the structural surface change and resultant increased surface roughness appeared to have promoted biofilm formation.
Significance. While having bioactive potential through ion release, the stability of surface integrity of bioactive materials is a key-parameter to be assessed with regard to their cario-static potential. (C) 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2017.04.002

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

Dental implants are highly effective for improving the occlusion function after tooth loss. However, ordinarily titanium dental implants sometimes require long term for the osseointegration. If there is insufficient bone in the patients, surgical pre-treatment such as autologous bone transplantation is required, imposing a big burden on the patient. Furthermore, a predominance of invasion of the gingival epithelium by epithelial cells at an early stage increases the risk of unsuccessful osseointegration. Therefore, to reduce the burden on the patient and increase the success rate of dental implant treatment, we need to develop a dental implant that can promote osseointegration more quickly and efficiently. We presumed that it would be one of efficient strategies for the quick and reliable osseointegration if we could control the cell population around the dental implant. Here, we micro-patterned a titanium surface by using a gelatin matrix. Mesenchymal stem cells were cultured, and cell populations were investigated. On the titanium surface with a micro-patterned gelatin matrix, mesenchymal stem cells first adhered to the titanium and then to the gelatin, enabling cell adhesion to be controlled time dependently. These results suggest that it may be possible to develop functional dental implants in which we can control the cell population of epithelial and mesenchymal stem cells and can promote quick and reliable osseointegration.

DOI： 10.11159/nddte17.111

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

Currently, the functional monomer 10-methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) was documented to chemically bond to zirconia ceramics. However, little research has been conducted to unravel the underlying mechanisms. This study aimed to assess the chemical interaction and to demonstrate the mechanisms of coordination between 10-MDP and zirconium oxide using H-1 and P-31 magic angle spinning (MAS) nuclear magnetic resonance (NMR) and two dimensional (2D) H-1 -&gt; P-31 heteronuclear correlation (HETCOR) NMR. In addition, shear bond-strength (SBS) tests were conducted to determine the effect of 10-MDP concentration on the bonding effectiveness to zirconia. These SBS tests revealed a 10-MDP concentration-dependent SBS with a minimum of 1-ppb 10-MDP needed. P-31-NMR revealed that one P-OH non-deprotonated of the PO3H2 group from 10-MDP chemically bonded strongly to zirconia. H-1-P-31 HETCOR NMR indicated that the 10-MDP monomer can be adsorbed onto the zirconia particles by hydrogen bonding between the P=O and Zr-OH groups or via ionic interactions between partially positive Zr and deprotonated 10-MDP (P-O-). The combination of H-1 NMR and 2D H-1-P-31 HETCOR NMR enabled to describe the different chemical states of the 10-MDP bonds with zirconia; they not only revealed ionic but also hydrogen bonding between 10-MDP and zirconia.

DOI： 10.1038/srep45563

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Objective. CAD-CAM blocks to fabricate semi-direct and indirect restorations are available in different sorts of ceramics as well as composite. In order to bond restorations prepared out of composite blocks into tooth cavities, it is recommended to gently sandblast the surface prior to the application of a primer/adhesive. Today, the effect of sandblasting composite block surfaces has not thoroughly been investigated. In this study, the ultra-structure of composite CAD-CAM blocks was investigated with special attention to the effect of sandblasting on the surface topography and of silanization on the bonding performance.
Methods. Five different composite CAD-CAM blocks were involved. We correlatively investigated their structural and chemical composition using X-ray diffraction (XRD), energy dispersion spectroscopy (EDS), scanning electron microscopy (SEM) and (scanning) transmission electron microscopy ((S)TEM). The effect of sandblasting was also imaged in cross-section and at the interface with composite cement. Finally, we measured the shear bond strength to the sandblasted block surface with and without silanization.
Results. All composite blocks revealed a different ultra-structure. Sandblasting increased surface roughness and resulted in an irregular surface with some filler exposure. Sandblasting also damaged the surface. When the sandblasted composite blocks were silanized, superior bonding receptiveness in terms of higher bond strength was achieved except for Shofu Block HC.
Significance. Sandblasting followed by silanization improved the bond strength to composite CAD-CAM blocks. However, sandblasting may also damage the composite CAD-CAM block surface. For the composite CAD-CAM block Shofu Block HC, the damage was so severe that silanization did not improve bond strength. (C) 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2016.12.003

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DOI： 10.11159/ijtan.2017.003

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

Objective. For bonding indirect restorations, some 'universal' adhesives incorporate a silane coupling agent to chemically bond to glass-rich ceramics so that a separate ceramic primer is claimed to be no longer needed. With this work, we investigated the effectiveness/stability of the silane coupling function of the silanecontaining experimentally prepared adhesives and Scotchbond Universal (3MESPE).
Methods and materials. Experimental adhesives consisted of Scotchbond Universal and the silane-free Clearfil S3 ND Quick (Kuraray Noritake) mixed with Clearfil Porcelain Bond Activator (Kuraray Noritake) and the two adhesives to which gamma-methacryloxypropyl-trimethoxysilane (gamma-MPTS) was added. Shear bond strength was measured onto silica-glass plates; the adhesive formulations were analyzed using fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance (NMR). In addition, shear bond strength onto CAD-CAM composite blocks was measured without and after thermo-cycling ageing.
Results. A significantly higher bond strength was recorded when Clearfil Porcelain Bond Activator was freshly mixed with the adhesive. Likewise, the experimental adhesives, to which gamma-MPTS was added, revealed a significantly higher bond strength, but only when the adhesive was applied immediately after mixing; delayed application resulted in a significantly lower bond strength. FTIR and C-13 NMR revealed hydrolysis and dehydration condensation to progress with the time after gamma-MPTS was mixed with the two adhesives. After thermocycling, the bond strength onto CAD-CAM composite blocks remained stable only for the two adhesives with which Clearfil Porcelain Bond Activator was mixed.
Significance. Only the silane coupling effect of freshly prepared silanecontaining adhesives was effective. Clinically, the use of a separate silane primer or silane freshly mixed with the adhesive remains recommended to bond glass-rich ceramics. (C) 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2016.07.002

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

Species of the Fe/Mn-oxidizing bacteria Leptothrix produce tremendous amounts of microtubular, Fe/Mn-encrusted sheaths within a few days in outwells of groundwater that can rapidly clog water systems. To understand this mode of rapid sheath production and define the timescales involved, behaviors of sheath-forming Leptothrix sp. strain OUMS1 were examined using time-lapse video at the initial stage of sheath formation. OUMS1 formed clumps of tangled sheaths. Electron microscopy confirmed the presence of a thin layer of bacterial exopolymer fibrils around catenulate cells (corresponding to the immature sheath). In time-lapse videos, numerous sheath filaments that extended from the periphery of sheath clumps repeatedly fragmented at the apex of the same fragment, the fragments then aggregated and again elongated, eventually forming a large sheath clump comprising tangled sheaths within two days. In this study, we found that fast microscopic fragmentation, dissociation, re-aggregation and re-elongation events are the basis of the rapid, massive production of Leptothrix sheaths typically observed at macroscopic scales.

DOI： 10.3390/biology5030032

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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：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：SAGE PUBLICATIONS INC  

The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (mu Raman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-mu m transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia-and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. mu Raman revealed t-ZrO2 -to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia-and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical elemental shifts recorded in the veneering ceramic did not suffice to draw definitive conclusions regarding potential chemical interaction of the veneering ceramic with zirconia. Sandblasting damaged the zirconia surface and induced phase transformation that also resulted in residual compressive stress. Difference in CTE of zirconia versus that of the veneering ceramic resulted in an unfavorable residual tensile stress at the zirconia-veneering ceramic interface.

DOI： 10.1177/0022034515608825

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

Objective. The functional monomer 10-MDP has been considered as one of the best performing functional monomers for dental adhesives. Different adhesives containing 10-MDP are commercially available, among which many so-called 'universal' adhesives. We hypothesize that the quality of the functional monomer 10-MDP in terms of purity may affect bonding performance.
Methods. We therefore characterized three different 10-MDP versions (10-MDP_KN provided by Kuraray Noritake; 10-MDP_PCM provided by PCM; 10-MDP_DMI provided by DMI) using NMR, and analyzed their ability to form 10-MDP_Ca salts on dentin using XRD. The 'immediate' and 'aged' micro-tensile bond strength (mu TBS) to dentin of three experimental 10-MDP primers was measured. The resultant interfacial adhesive-dentin ultra-structure was characterized using TEM.
Results. NMR disclosed impurities and the presence of 10-MDP dimer in 10-MDP_PCM and 10-MDP_DMI. 10-MDP_PCM and 10-MDP_DMI appeared also sensitive to hydrolysis. 10-MDP_KN, on the contrary, contained less impurities and dimer, and did not undergo hydrolysis. XRD revealed more intense 10-MDP_Ca salt deposition on dentin induced by 10-MDP_KN. The adhesive based on the experimental 10-MDP_KN primer resulted in a significantly higher 'immediate' bond strength that remained stable upon aging; the mu TBS of the experimental 10-MDP_PCM and 10-MDP_DMI adhesives significantly dropped upon aging. TEM revealed thicker hybridization and more intense nano-layering for 10-MDP_KN.
Significance. It was concluded that primer impurities and the presence of 10-MDP dimer affected not only hybridization, but also reduced the formation of 10-MDP_Ca salts and nano-layering. 10-MDP in a high purity grade is essential to achieve durable bonding. (C) 2015 Published by Elsevier Ltd on behalf of Academy of Dental Materials. All rights reserved.

DOI： 10.1016/j.dental.2015.09.019

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

The purpose of the present study was to evaluate the mechanical and chemical properties of a novel glass ionomer cement for use as a pit and fissure sealant containing a porous hydroxyapatite, namely, apatite ionomer cement (AIC). Control sealant samples were used Fuji III (GIC-S). The experiment sealant samples (AIC-S) consisted of porous spherical hydroxyapatite (HApS) particles added at 28 wt% to GIC-S powder. The GIC-S and AIC-S samples were evaluated through mechanical strength measurements, scanning electron microscopy observations, energy dispersive X-ray spectroscopy analysis, fluoride ion release tests, and antibacterial tests. The flexural strength of the AIC-S was significantly higher than that of GIC-S for each period, 1 h, 24 h and 1 year. The fluoride release dose for AIC-S was consistently higher than that for GIG-S. In addition, the antibacterial properties of AIC-S were superior to those of GIC-S. The novel AIC-S may be a more suitable sealant material for pits and fissures with intact and/or infected enamel.

DOI： 10.4012/dmj.2014-195

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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：(公社)日本生物工学会  

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

Among several functional monomers, 10-methacryloxydecyl dihydrogen phosphate (10-MDP) bonded most effectively to hydroxyapatite (HAp). However, more hydrolysis-resistant functional monomers are needed to improve bond durability. Here, we investigated the adhesive potential of the novel fluoro-carbon functional monomer 6-methacryloxy-2,2,3,3,4,4,5,5-octafluorohexyl dihydrogen phosphate (MF8P; Kuraray Noritake Dental Inc., Tokyo, Japan) by studying its molecular interaction with powder HAp using solid-state nuclear magnetic resonance (H-1 MAS NMR) and with dentin using x-ray diffraction (XRD) and by characterizing its interface ultrastructure at dentin using transmission electron microscopy (TEM). We further determined the dissolution rate of the MF8P_Ca salt, the hydrophobicity of MF8P, and the bond strength of an experimental MF8P-based adhesive to dentin. NMR confirmed chemical adsorption of MF8P onto HAp. XRD and TEM revealed MF8P_Ca salt formation and nano-layering at dentin. The MF8P_Ca salt was as stable as that of 10-MDP; MF8P was as hydrophobic as 10-MDP; a significantly higher bond strength was recorded for MF8P than for 10-MDP. In conclusion, MF8P chemically bonded to HAp. Despite its shorter size, MF8P possesses characteristics similar to those of 10-MDP, most likely to be associated with the strong chemical bond between fluorine and carbon. Since favorable bond strength to dentin was recorded, MF8P can be considered a good candidate functional monomer for bonding.

DOI： 10.1177/0022034513514447

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

The term nanobacteria, sometimes referred to as nanobacteria-like particles (NLPs), is presently recognized as a misnomer for inert calcified nanoparticles. However, misinterpretation of its propagation as a living organism still continues. Ultrastructural and elemental analyses, combining immuno-electron microscopy with an original NLP isolate (P-17) derived from urinary stones, and an IgM monoclonal antibody (CL-15) raised against P-17 have now revealed that, oxidized lipids with acidified functional groups were key elements in NLP propagation. Lamellar structures composed of acidic/oxidized lipids provided structural scaffolds for carbonate apatite crystals. During in vitro culture, lipid peroxidation induced by gamma-irradiation of FBS was a major cause of accelerated NLP propagation. In pathological tissue samples from hyperlipidemic atherosclerosis-prone mice, CL-15 co-localized with fatty plaques, macrophage infiltrates and osteocalcin staining of aortic valve lesions. These observations indicate that naturally occurring NLP composed of mineralo-oxidized lipids complexes are generated as by-products rather than etiological agents of chronic inflammation. (C) 2014 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.nano.2013.08.010

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC BIOSCIENCE BIOENGINEERING JAPAN  

When constructing an in vitro model of liver tissue to mimic the in vivo liver microenvironment, the major challenge is to preserve and maintain the hepatocyte phenotype. The aim of this study was to develop a novel intelligent hybrid sponge for use in a dense co-culture system designed to simulate the liver microenvironment. We prepared a galactosylated chitosan (GCs)/hyaluronic acid (HA) hybrid sponge using a freeze-drying technique for the co-culture of primary hepatocytes and endothelial cells. Subsequently, we investigated the biocompatibility of the GCs/HA scaffold with primary hepatocytes and endothelial cells in terms of cell attachment, morphology, bioactivity, and maintenance of specific liver functions. The GCs/HA-hybrid sponge demonstrated good biocompatibility not only with primary hepatocytes, but also with endothelial cells. In our model, primary hepatocytes exhibited superior bioactivity and higher levels of liver-specific functions in terms of hepatocyte-specific gene expression, urea production, and testosterone metabolism as compared to a monoculture system. We succeeded in constructing a liver tissue-like model using the GCs/HA-hybrid sponge. Therefore, we anticipate that GCs/HA-hybrid sponges may be a promising matrix for the co-culture of hepatocytes and endothelial cells in liver tissue engineering, and might be employed as a novel co-culture model for applications in toxicology and drug metabolism. (C) 2013, The Society for Biotechnology, Japan. All rights reserved.

DOI： 10.1016/j.jbiosc.2013.06.015

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Objectives. The functional monomer 10-methacryloxydecyl dihydrogen phosphate (10-MDP), recently used in more self-etch adhesives, chemically bonds to hydroxyapatite (HAp) and thus tooth tissue. Although the interfacial interaction of the phosphoric-acid functional group of 10-MDP with HAp-based substrates has well been documented, the effect of the long carbon-chain spacer of 10-MDP on the bonding effectiveness is far from understood.
Methods. We investigated three phosphoric-acid monomers, 2-methacryloyloxyethyl dihydrogen phosphate (2-MEP), 6-methacryloyloxyhexyl dihydrogen phosphate (6-MHP) and 10-MDP, that only differed for the length of the carbon chain, on their chemical interaction potential with HAp and dentin, this correlatively using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Commercial 6-MHP and 10-MDP containing adhesives were investigated as well.
Results. XRD revealed that on HAp only 10-MDP produced monomer-calcium salts in the form of 'nano-layering', while on dentin all monomers produced 'nano-layering', but with a varying intensity in the order of 10-MDP &gt; 6-MHP &gt; 2-MEP. TEM confirmed that 10-MDP formed the thickest hybrid and adhesive layer. XRD and TEM revealed 'nano-layering' for all commercial adhesives on dentin, though less intensively for the 6-MHP containing adhesive than for the 10-MDP ones.
Significance. It is concluded that not only the phosphoric-acid group but also the spacer group, and its length, affect the chemical interaction potential with HAp and dentin. In addition, the relatively strong 'etching'' effect of 10-MDP forms more stable monomer-Ca salts, or 'nano-layering', than the two shorter carbon-chain monomers tested, thereby explaining, at least in part, the better bond durability documented with 10-MDP containing adhesives. (c) 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2013.05.006

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

We have designed and synthesized a new class of rhodamine dyes with an extended p-conjugated system and named them 3',3 ''-bis(oxospiroisobenzofuran)-3,7-bis(diethylamino) benzopyrano-xanthene (ABPX01) dyes. ABPX01 exhibits fluorescence emission in both dilute solution and the aggregate state, whereas conventional rhodamine dyes show aggregation-induced quenching (AIQ). The chemical species of ABPX01 in solution were determined by spectrophotometric measurements and density functional theory (DFT) calculations to study the relationship among chemical species, color, and fluorescence emission. ABPX01 has various forms: the spirolactone form (ABPX01(0)), which is colorless; and the monocationic form (ABPX01H(+)) and the dicationic form (ABPX01H(2)(2+)), which are colored. By orienting a pair of spirolactone benzene moieties differently, the stereoisomers of trans-and cis-ABPX01(0) were separated and their crystal structures determined. ABPX01H(2)(2+) was identified to be a red fluorescent species. Detailed spectroscopic and electron microscopic investigations led to the assumption that the ABPX01H(2)(2+) formed ion associates with Cl- as counter anions in HCl aqueous solution, and the nano-and submicrometer-sized colloidal aggregates of ABPX01 hydrochloride exhibit fluorescence emission. To further verify the aggregation-induced emission enhancement (AIEE) mechanism, ABPX01 hydrochloride was synthesized and its fluorescence was similarly checked in the powder state. AIEE in ABPX01 might be attributed to the synergistic combination of the restriction of dye-dye interaction induced dimer formation by sterically hindered ion associates and carboxylic benzene moieties, and the structural rigidity and intermolecular arrangement of the xanthene moiety. We expect that the design strategy of ABPX dyes will be extended to the development of a wide variety of functional organic-dye-based fluorophores (ODFs) with suitable fluorescence-emission controlled mechanisms for many useful applications in new electroluminescent devices.

DOI： 10.1039/c2cp43503a

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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：English   Publisher：WILEY-BLACKWELL  

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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：SAGE PUBLICATIONS INC  

According to the 'Adhesion-Decalcification' concept, specific functional monomers within dental adhesives can ionically interact with hydroxyapatite (HAp). Such ionic bonding has been demonstrated for 10-methacryloyloxydecyl dihydrogen phosphate (MDP) to manifest in the form of self-assembled 'nano-layering'. However, it remained to be explored if such nano-layering also occurs on tooth tissue when commercial MDP-containing adhesives (Clearfil SE Bond, Kuraray; Scotchbond Universal, 3M ESPE) were applied following common clinical application protocols. We therefore characterized adhesive-dentin interfaces chemically, using x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), and ultrastructurally, using (scanning) transmission electron microscopy (TEM/STEM). Both adhesives revealed nano-layering at the adhesive interface, not only within the hybrid layer but also, particularly for Clearfil SE Bond (Kuraray), extending into the adhesive layer. Since such self-assembled nano-layering of two 10-MDP molecules, joined by stable MDP-Ca salt formation, must make the adhesive interface more resistant to biodegradation, it may well explain the documented favorable clinical longevity of bonds produced by 10-MDP-based adhesives.

DOI： 10.1177/0022034512437375

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

Due to the high corrosion resistance and strength to density ratio titanium is widely used in industry, and also in a gamut of medical applications. Here we report for the first time on our development of a titanium passivation layer sensor that makes use of surface plasmon resonance (SPR). The deposited titanium metal layer on the sensor was passivated in air, similarly to titanium medical devices. Our "Ti-SPR sensor" enables analysis of biomolecule interactions with the passivated surface of titanium in real time. As a proof of concept, corrosion of a titanium passivation layer exposed to acid was monitored in real time. The Ti-SPR sensor can also accurately measure the time-dependence of protein adsorption onto the titanium passivation layer at sub-nanogram per square millimeter accuracy. Besides such SPR analyses, SPR imaging (SPRI) enables real time assessment of chemical surface processes that occur simultaneously at "multiple independent spots" on the Ti-SPR sensor, such as acid corrosion or adhesion of cells. Our Ti-SPR sensor will therefore be very useful to study titanium corrosion phenomena and biomolecular titanium-surface interactions with application in a broad range of industrial and biomedical fields. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2011.11.025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MOSHER & LINDER, INC  

Purpose: To clarify the effects of the addition of silanized (S) and unsilanized (U) spherical silica filler to resin-modified glass-ionomer cement and of powder-liquid ratio on (1) the early marginal gap-width of restorations in both tooth cavities and Teflon molds, (2) the gap-formation of restorations in Class V cavities, and (3) the compressive strength of the cement. Methods: Resin-modified glass-ionomer powder (Fuji II LC EM, GC) was modified by adding 5 and 10 wt% of powder respectively, of S and U, and then the powder-liquid ratio was increased up to 4.8. Human premolars, extracted for orthodontic reasons, were used for this study. Cylindrical cavities (1.5 mm deep, 3.5 mm in diameter; one cavity was prepared in each tooth in the coronal region and medial surface) were prepared in extracted human premolar teeth and restored with resin-modified glass-ionomer cements. Each restoration margin was inspected immediately after curing and polishing (as the immediate condition was the most severe), the maximum gap-width and the opposing width (if any) were determined microscopically (n= 10). An additional test was conducted in model Class V cavities. After finishing of restorations in model Class V cavities, each tooth was sectioned in a bucco-lingual direction through the center of the restoration, and the presence or absence of gaps along the cavity interface was evaluated (n=10). Additionally, the maximum marginal gap-width and the opposing-width along margins of restorations in cylindrical Teflon molds were measured (n= 10). The compressive strengths of the restorative materials were determined immediately after light-activation (n=10). Results: Marginal gap (tooth cavity: 0.32 to 0.25-0.20%, P&lt; 0.05; Teflon cavity: 0.94 to 0.6-0.8%, P&lt; 0.05) and cavity adaptation (no gap in the Class V: 22 to 40-50%, P&lt; 0.05) of the restorations improved with increasing powder-liquid ratio (3.0 to 4.4-4.8) and compressive strength increased (111 to 150-170 MPa, P&lt; 0.05). Highly significant correlation coefficients were found for the relationships between powder-liquid ratio and (1) percentage of marginal gap width in the tooth cavity (r= -0.96, P= 0.002, n= 6), (2) gap-free tooth/cement interfaces (r= 0.90, P= 0.015, n= 6), (3) percentage of marginal gap widths in the Teflon mold (i.= 0.98, P= 0.0004, n= 6) and (4) compressive strengths of the cements (r= 0.95, P= 0.004, n= 6). (Am J Dent 2011;24:310-314).

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By a facile LiNO3 flux method, lithium manganese oxide composites (xLi(4)Mn(5)O(12)center dot yLi(2)MnO(3)) were synthesized using a hierarchical organization precursor of manganese dioxide. Li4Mn5O12 and Li2MnO3 have spinel and rocksalt structures, respectively. The lithiation and structural transformation from the precursor to the composites occurred topotactically from exterior toward interior in the precursor particle with the increase of reaction time, and the composites had core-shell spinel@rocksalt structures in addition to the original hierarchical core-shell organization. The electrochemical measurements at 50 degrees C after 50 cycles confirmed that a typical spinel@rocksalt cathode had higher capacity retention (87.1%) than that with the composition close to the stoichiometric spinel (64.6%), indicating the Li2MnO3 shell can improve cycling stability for the composite electrode at elevated temperature. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2011.06.005

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Following the "adhesion-decalcification" concept, specific functional monomers possess the capacity to primary chemically interact with hydroxyapatite (HAp). Such ionic bonding with synthetic HAp has been demonstrated for 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), manifest as self-assembled "nanolayering". In continuation of that basic research this study aimed to explore whether nanolayering also occurs on enamel and dentin when a 10-MDP primer is applied following a common clinical application protocol. Therefore, the interaction of an experimental 10-MDP primer and a control, commercially available, 10-MDP-based primer (Clearfil SE Bond primer (C-SE), Kuraray) with enamel and dentin was characterized by X-ray diffraction (XRD), complemented with transmission electron microscopy interfacial ultrastructural data upon their reaction with enamel and dentin. In addition, XRD was used to study the effect of the concentration of 10-MDP on nanolayering on dentin. Finally, the stability of the nanolayers was determined by measuring the bond strength to enamel and dentin when a photoinitiator was added to the experimental primer or when interfacial polymerization depended solely on the photoinitiator supplied with the subsequently applied adhesive resin. XRD confirmed nanolayering on enamel and dentin, which was significantly greater on dentin than on enamel, and also when the surface was actively rubbed with the primer. Nanolayering was also proportional to the concentration of 10-MDP in the primer. Finally, the experimental primer needed the photoinitiator to obtain a tensile bond strength to dentin comparable with that of the control C-SE primer (which also contains a photoinitiator), but not when bonded to enamel. It is concluded that self-assembled nanolayering occurs on enamel and dentin, even when following a clinically used application protocol. The lower bonding effectiveness of mild self-etch adhesives to enamel should be ascribed in part to a lower chemical reactivity (nanolayering) with enamel HAP. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2011.04.026

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Previous research, in which the bonding effectiveness of the 3 self-etch monomers HAEPA, EAEPA, and MAEPA was determined, showed that MAEPA was most effective. In this study, the molecular interactions of these monomers with hydroxyapatite and dentin were investigated by combining x-ray diffraction, infrared spectroscopy, and scanning electron microscopy. We tested the null hypothesis that the bonding performance of these monomers does not correlate to the formation of monomer-calcium salts and to hydrolytic stability of these monomer-calcium complexes. Monomer/ethanol/water solutions were prepared and applied to synthetic hydroxyapatite and dentin. While HAEPA and EAEPA dissolved dentin considerably and deposited unstable calcium-phosphate salts (DCPD), MAEPA formed hydrolysis-resistant monomer-calcium salts that remained attached to the dentin surface even after being washed. The chemical stability of the monomer-Ca salts was thought to contribute in particular to the bond durability, but this study shows that the formation of stable monomer-calcium salts also enhances the 'immediate' bonding performance of self-etch adhesives.

DOI： 10.1177/0022034510397197

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DOI： 10.18939/jsdmd.30.1_63

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

Although decayed/fractured teeth can be reconstructed minimally invasively and nearly invisibly using adhesive technology, the clinical longevity of dental composite restorations is still too short. Water sorption is thought to be the principal cause of destabilization of the biomaterial-tooth bond. However, the actual mechanisms of interfacial degradation are far from understood. Here we report how nano-controlled molecular interaction at the biomaterial-hard tissue interface can improve bond durability. The use of functional monomers with a strong chemical affinity for the calcium in hydroxyapatite is essential for long-term durability. Correlative X-ray diffraction and solid-state nuclear magnetic resonance disclosed a time-dependent molecular interaction at the interface with stable ionic bond formation of the monomer to hydroxyapatite competing in time with the deposition of less stable calcium phosphate salts. The advanced tooth-biomaterial interaction model gives not only an insight into the mechanisms of bond degradation, but also provides a basis to develop functional monomers for more durable tooth reconstruction. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actbio.2010.03.024

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

This study investigated the effects of spherical silica filler (SSF) on the workability and mechanical properties of resin-modified glass ionomer cements for luting (RMGICL). Varying powder/liquid ratios (P/L=2.0, 2.2, 2.4, and 2.6) of a commercially available glass ionomer cement (Fuji Lute, GC Corp.) were mixed with SSF at different weight percentages (5, 7.5, and 10%). On film thickness, statistically significant effects of SSF addition were noted at 2.5 minutes after mixing started, notably at P/L=2.4 and 2.6 when 7.5 and 10 wt% of SSF were added. The same result was also obtained for consistency evaluation. On mechanical and bonding strengths to the tooth substrate, no statistically significant differences were observed among all the SSF weight percentages within each P/L ratio. SSF-added RMGICL, at a higher powder/liquid ratio exhibited increased mechanical and bonding strengths when compared to a control without SSF addition, but nonetheless maintained the film thickness with no further increase.

DOI： 10.4012/dmj.2009-092

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

Titanium and hydroxyapatite (HA) are widely used as biomaterials for dental and medical applications. HA-coated titanium implants have excellent biocompatibility and mechanical properties. However, the adherence of HA film formed on titanium substrate is weak because of the lack of chemical interaction between HA and titanium. A solution to this problem is to form an intermediate film on titanium substrate, which provide excellent adherence to both titanium substrate and HA. We developed a novel biomaterial called calcium titanate-amorphous carbon (CaTiO3-aC) coating prepared by modified thermal decomposition-method. The purpose of this study was to evaluate the effect of CaTiO3-aC and HA coating (positive control), and Ti (negative control) on osteoblastic (MT3T3-E1) cell responses. An increased cellular proliferation was observed in CaTiO3-aC coating compared to HA coating. The maximum expressions of ALP activity, Col I and ALP mRNA were higher and achieved in shorter period of time in CaTiO3-aC coating compared to others. These results demonstrated that CaTiO3-aC promoted better cell attachment, cellular proliferation, and osteoblastic differentiation compared with HA. In conclusion, we suggested that CaTiO3-aC could be considered as an important candidate as a coating material.

DOI： 10.1177/0885328209340334

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

Objective. Biomaterials with anti-microbial properties are highly desirable in the oral cavity. Ideally, bactericidal molecules should be immobilized within the biomaterial to avoid unwanted side-effects against surrounding tissues. They may then however loose much of their antibacterial efficiency. The aim of this study was to investigate how much antibacterial effect an immobilized bactericidal molecule still has against oral bacteria.
Methods. Experimental resins containing 0, 1 and 3% cetylpyridinium chloride (CPC) were polymerized, and the bacteriostatic and bactericidal effects against Streptococcus mutans were determined. Adherent S. mutans on HAp was quantitatively determined using FE-SEM and living cells of S. mutans were quantified using real-time RT-PCR. The amount of CPC released from the 0%-, 1%- and 3%-CPC resin sample into water was spectrometrically quantified using a UV-vis recording spectrophotometer.
Results. UV spectrometry revealed that less than 0.11 ppm of CPC was released from the resin into water for all specimens, which is lower than the minimal concentration generally needed to inhibit biofilm formation. Growth of S. mutans was significantly inhibited on the surface of the 3%-CPC-containing resin coating, although no inhibitory effect was observed on bacteria that were not in contact with its surface. When immersed in water, the antibacterial capability of 3%-CPC resin lasted for 7 days, as compared to resin that did not contain CPC.
Significance. These results demonstrated that the bactericidal molecule still possessed significant contact bacteriostatic activity when it was immobilized in the resin matrix. (C) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dental.2008.08.012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOURNAL HARD TISSUE BIOLOGY  

In the current study, we compared the recently developed CaTiO3-amorphous carbon (CaTiO3-aC) as a bone inducing coating material with HA from aspects of surface electric charge and solubility. CaTiO3-aC had negative surface electric charge similar to HA. Thus similar tissue reaction and bone inducing ability were considered to obtain.
On the other hand solubility of CaTiO3-aC coating was lower than HA. Moreover though CaTiO3-aC itself showed low solubility, CaCO3 was found to be included in it, and long-term slow Ca2+ release occurred. Thus the sample was suggested to be used as an ion exchange material.
When the implant using Ti/CaTiO3-aC/HA double layer coating was developed, first bioactive state of the implant will continue due to HA character. Then even early resorption of HA occurs, bioactive state will continue due to CaTiO3-aC layer. Therefore Ti base will not expose. This result is supposed to contribute long term success of the implant.

DOI： 10.2485/jhtb.17.115

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

The purpose of this study was to evaluate how ultrasonic cleaning of silica-coated zirconia surfaces would influence the latter's bond strength to resin luting material. Forty zirconia specimens were divided into four groups: one air abrasion group and three silica-coated groups. Silica-coated specimens were cleaned with distilled water using an ultrasonic cleaner after tribochemical silica coating and then divided into three groups according to cleaning durations: I minute, 5 minutes, or without cleaning. Following which, resin luting material was polymerized against the specimens. After storage in water for 24 hours, the specimens were subjected to shear bond strength test. Shear bond strength of silica-coated group without cleaning was significantly higher than the other three groups, but there were no statistically significant differences among the three latter groups. SEM images suggested visible differences among the treatment methods. With EDXS analysis, it was revealed that ultrasonic cleaning decreased the silica content on the treated surfaces. Therefore, results showed that ultrasonic cleaning of tribochemically silica-coated zirconia surfaces decreased the adhesion efficacy to resin luting material.

DOI： 10.4012/dmj.27.842

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PATIENT: An 83-year-old woman visited the hospital for new complete dentures. A mesh type stainless palatal plate (Trutissu plate) was selected, because it enables the patient to experience the taste and temperature of food. Twenty one months after insertion, the patient returned complaining of pain on mucosa under the mandibular denture base. On clinical examination, a small swollen area was observed on the palatine rugae region of the mesh plate. By making a small hole in the swollen part, a creamy mass of dark brown color was discharged from the swollen space between the laminated structure of the Trutissu plate. Three months after the first deformation was corrected, further deformation of the Trutissu plate was observed. The patient admitted that she had not used the ultrasonic cleansing apparatus. A candidiasis-like lesion was observed on the palatal mucosa. DISCUSSION: The formation of Candida biofilms on dentures may assist survival of fungal cells and contribute to the disease process in patients with denture stomatitis. In this case, the patient did not use ultrasonic cleaner, thus resulting in microbial accumulation and morphological change of the laminated mesh plate. However, this is rare in the clinical use of the Trutissu mesh plate, and the only case reported in 20 years. Ultrasonic cleansing was effective in removing microorganisms from the denture. CONCLUSION: Routine ultrasonic cleansing should be performed to avoid the possible accumulation of microorganisms in the laminated mesh structure.

DOI： 10.2186/jjps.52.555

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOURNAL HARD TISSUE BIOLOGY  

We developed a novel method for titanium coating material using modified thermal decomposition technique, specifically focusing on presence of CaTiO3 and carbon C. Two layers of thin film coating composed of CaTiO3-amorphous carbon compound (CaTiO3-aC) and hydroxyapatite (HA) were generated on titanium surface. In this method, ratios of Ca/P as well as Ca/Ti, sintering temperature and sintering velocity were carefully planned. Within crystal structure of CaTiO3 granules, 4 atomic % of carbon in amorphous state was included. By our method, inclusion of carbon in HA suggested formation of carbonate apatite. Regarding with attachment-detachment experiment at titanium surface, adhesion strength was 2.5 times stronger in CaTiO(3)aC/FIA coating substrate as compared to HA only coating material. Results of the novel developed modified thermal decomposition method suggested that the 2 layers biomaterial composed of CaTiO3-aC (0.6 mu m) and carbonate apatite-included HA (2.4 mu m) can be used as a coating material on titanium surface.

DOI： 10.2485/jhtb.17.47

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Language：Japanese   Publisher：JAPAN INST METALS  

Fatigue crack initiation and propagation have been investigated in relation to the aged microstructure in an Al-4%Ge alloy by means of a fatigue test, microstructural characterization, and fractography. Specimens were solution-treated at 693 K, quenched in iced water, kept at 273 K for 60 s, aged at 473 K for times up to 72 ks and then fatigue-tested. It was confirmed that as the aging time increases, the tensile strength initially increases, reaches a maximum, and then decreases, while the fatigue strength monotonously decreases. Both in the interior and at the surface of the specimen, as the aging proceeded, the growth of precipitates inside the grain as well as on the grain boundary was observed while the width of precipitate free zones (PFZs) adjacent to the grain boundary was almost constant. Fractographic observations showed that intergranular fracture became predominant with increasing aging time and decreasing stress amplitude. From this result and close observations of the fatigue cracks initiation sites, the cracking was deduced to proceed in the following steps: 1) cracks initiate in the intergranular region of the specimen surface, 2) the cracks propagate along the intergranular region towards the interior of the specimen, 3) the crack path transits to the transgranular region because of the increase in true stress, 4) ductile fracture occurs with a marked reduction in area. The crack initiation was presumed to occur as a result of intrusion and extrusion formations along the soft PFZs that play a similar role to that of the persistent slip bands in most metallic materials. © 2006 The Japan Institute of Metals.

DOI： 10.2320/jinstmet.70.897

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DOI： 10.2485/jhtb.14.309

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Other Link： http://search.jamas.or.jp/link/ui/2007049575

Language：English   Publishing type：Research paper (scientific journal)   Publisher：INT SOC HISTOLOGY & CYTOLOGY  

Scanning electron microscopy (SEM) was employed to study the effect of calcitonin on the distribution of actin filaments in osteoclasts obtained from rat tibiae. Fluorescent microscopy was also applied to examine calcitonin-induced changes in the distribution of actin filaments, non-muscle myosin, M-Ras, and extracellular signal-regulated kinase (ERK) to clarify the role of ERK in the cytoskeleton of osteoclasts. SEM of control osteoclasts revealed a ring-like structure in the peripheral region. Labeled actin filaments and non-muscle myosin were detected in the peripheral region and exhibited a ring-like pattern. Immunoreactivity indicating M-Ras and ERK was also detected in the vicinity of the actin ring. After calcitonin treatment, many osteoclasts exhibited a retracted appearance and lacked a discernible actin ring. Numerous retraction fibers were found at the edge of calcitonin-treated osteoclasts. Actin filaments and non-muscle myosin were concentrated in the cytoplasm of calcitonin-treated osteoclasts, and exhibited a filamentous pattern. Labeled M-Ras and ERK also accumulated in the central region of these osteoclasts. These findings suggest that actin-myosin interaction plays an essential role in the retraction of osteoclasts induced by calcitonin. ERK may play a role in this interaction by activating myosin light chain kinase, as previously observed in smooth muscle cells.

DOI： 10.1679/aohc.68.143

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

Immunohistochemistry for osteocalcin (OC) was performed on the rat vagal and glossopharyngeal sensory ganglia. OC-immunoreactive (IR) neurons were detected in the jugular (10%), petrosal (11%) and nodose ganglia (6%). The cell size analysis demonstrated that OC-IR neurons were predominantly small to medium-sized in the jugular ganglion (mean +/- S.D. = 356.3 +/- 192.2 mum(2), range = 86.5 - 831.5 mum(2)). On the other hand, such neurons were medium-sized to large in the petrosal (mean +/- S.D. = 725.6 +/- 280.7 mum(2), range = 124.7 - 1540.4 mum(2)) and nodose ganglia (mean +/- S.D. = 857.5 +/- 330.2 mum(2), range = 367.1 - 1608.0 mum(2)). In the circumvallate papilla, OC-IR nerve fibers were located in the vicinity of taste buds. Some taste bud cells were also immoureactive for the calcium-binding protein (CaBP). In the carotid body, however, OC-IR nerve fibers could not be detected. Retrograde tracing with fluorogold revealed that OC-IR nerve fibers in the circumvallate papilla mainly originated from the petrosal ganglion. These findings may suggest that OC-IR petrosal neurons have chemoreceptive function in the tongue. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.brainres.2004.10.011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Histochemical, immunohistochemical and electron energy-loss spectroscopic studies were performed to examine the relationship between sulphated glycosaminoglycans and medullary bone calcification using oestrogen-injected male Japanese quail. Sulphated glycosaminoglycans, detected by high iron diamine (HID) or HID-thiocarbohydrazide-silver protein (HID-TCH-SP) methods, were distributed throughout the matrix of medullary bone, some periphery and extending tips of the trabeculae stained weakly, and the globular structures at osteoid areas were exclusively positive for HID-TCH-SP stain. Immunohistochemistry identified keratan sulphate located in the globular structures at osteoid areas and calcified matrix, but chondroitin-4 sulphate and chondroitin-6 sulphate were not detected in the matrix. Using electron spectroscopic imaging, sulphur was determined to be localized in the globular structures. These results demonstrate that medullary bone matrix accumulates keratan sulphate in the globular structures, which are the foci for calcification, and eventually in the calcified areas. This suggests that keratan sulphate containing sulphur is maintained in the calcified matrix. These results indicate a unique process of calcification exists in medullary bone.

DOI： 10.1093/jmicro/dfh097

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

Immunohistochemistry for activated caspase-3 and terminal deoxynucleotidyl transferease-mediated dUTP-biotin nick end labeling (TUNEL) was performed on the trigeminal ganglion after infraorbital nerve transection in newborn rats. The injury induced caspase-3-immunoreactivity and DNA fragmentation in neuronal cell bodies in the maxillary division of the ganglion ipsilateral to the injury. Starting at 16 h post-injury the immunoreactive and TUNEL-positive neurons increased and reached the peak at 24 h (7.9% and 8.9%, respectively). Thereafter they decreased and returned to the normal control level (much less than1%) by 72 h. A double staining procedure revealed coexpression of caspasc-3-immunoreactivity and DNA fragmentation. 75.5% (114/151) of TUNEL-positive neurons expressed the immunoreactivity, while 84.4% (114/135) of immunoreactive neurons exhibited DNA fragmentation signal. These results suggest that caspase-3 plays an important role in apoptotic elimination of neonatally axotomized rodent primary neurons. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.brainres.2004.05.069

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Language：Japanese   Publisher：岡山歯学会  

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Language：English   Publisher：The Society of Hard Tissue Biology  

The morphology and characteristics of melanosomes are important features for differentiating melanocyte-derived melanotic lesions such as benign and malignant melanoma. There are two types of melanosome; eumelanin and pheomelanin. In this study, we attempted to elucidate the characteristics of melanosomes in malignant melanomas (melanotic type and amelanotic type) by ultrastructural analysis. In the melanotic type malignant melanoma in situ, pleomorphic and ellipsoid abnormal melanosomes, so-called eumelanin melanosomes, were detected, together with an increase in alkali elution rate. In the melanotic type invasive malignant melanoma, irregular ellipsoid and spheroid melanosomes were found either as discrete bodies or compound melanosomes, with further increase in alkali elution. In the amelanotic type malignant melanoma in situ, there were no melanosomes in atypical melanocytes and keratinocytes. In the amelanotic type invasive malignant melanoma, a few round melanosomes with low density matrix, so-called pheomelanin melanosomes, distributed in the cytoplasm. Our findings suggest that abnormal melanosome morphology and characteristics are predictive differential markers for the melanotic type or amelanotic type of oral malignant melanomas.

DOI： 10.2485/jhtb.13.87

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

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Background: The morphology and contents of melanosomes are important features for differentiating melanocyte-derived melanotic lesions such as melanosis and malignant melanoma. Methods: In this study, we attempted to elucidate the structure of melanin and sulphur content in oral melanosis and malignant melanomas by ultrastructural analysis. Results: In oral melanosis, the essential pathological findings were overproduction of eumelanin and discharge of melanin into keratinocytes. In malignant melanoma in situ, pleomorphic and ellipsoid abnormal melanosomes with an increase in sulphur content and alkali elution rate were detected. In invasive malignant melanoma, the irregular ellipsoid and spheroid melanosomes existing either as discrete bodies or compound melanosomes with furtherly increased sulphur content and alkali elution were detected. Conclusions: Our findings suggest that abnormal melanosome morphology and high sulphur content are predictive markers for assessment of early or precancerous melanotic lesions and malignant melanoma.

DOI： 10.1034/j.1600-0714.2002.00010.x

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Language：Japanese   Publisher：公益社団法人 日本顕微鏡学会  

DOI： 10.11410/kenbikyo1950.37.22

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Other Link： https://projects.repo.nii.ac.jp/?action=repository_uri&item_id=357319

Publishing type：Research paper (international conference proceedings)  

A mixture of heparin-Sepharose-purified bovine bone morphogenetic protein (BMP) and type I atellocollagen was implanted in the subcutaneous tissues of 4-week, 10-month and 18-month-old rats. The implants were removed at 7, 14 and 21 days after implantation. The effects of rat age on ectopic bone formation were evaluated on the explants using H and E staining, morphometric analysis, alkaline phosphatase (ALP) activity and calcium (Ca) content determination, as well as immunohistochemical staining of type IV collagen present in the basement membrane of blood vessels. On day 14 and 21, bone was observed in 4-week and 10-month-old rats but the amount of bone formed in the later was less than in the former. In 18-month-old rats, bone was first found focally in very limited regions of the explants on day 21 and the amount of bone was much less than in 4-week-old rats. At all periods ALP activity was higher in younger rats. On day 7, there were more blood vessels in the explants of 4-week-old rats than in those of 10- or 18-month-old rats. On day 14 and 21, more blood vessels were found in the central regions of the explants in 4-week-old rats than in the same regions in 10- or 18-month-old rats. The findings in the present study indicated that the rate and quantity of ectopic bone formation were reduced, and that the difference in blood vessel distribution might be related to the reduction in ectopic bone formation in aged rats, and suggest that the difference in blood vessel distribution is related to ectopic bone formation. Magnetism can stimulate ectopic bone formation induced by BMP. Copyright (C) 2000 Elsevier Science Ireland Ltd.

DOI： 10.1016/S0928-4680(00)00036-5

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

Carrier materials with sensor for drug concentration hold great promise as smart delivery systems for drugs which have strong side effects, such as anticancer agents and bactericides. However, any carriers sensing drug concentration have not been turned to practical use. We found that the phosphopullulan and CPC complex changed their interaction at critical micelle concentration of CPC with phosphopullulan. It was also revealed that this phenomenon strongly related the bactericidal effects of the complex.

DOI： 10.14832/gsjsdmd.2010f.0.29.0

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To effectively exploit the properties of antibacterial agents, we synthesized phosphorylated polysaccharides as the carrier for bactericide delivery to surface of apatitic substrates. It was indicated that 0.01% phosphorylated pullulan and 0.01% cetylpyridinium chloride (CPC) consistently exhibited an antibacterial effect, even after rinsing with distilled water, although CPC at a concentration of 10% showed no effect on bacterial growth after slight rinsing.

DOI： 10.14832/gsjsdmd.2009f.0.30.0

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DOI： 10.14832/gsjsdmd.2009s.0.39.0

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Event date： 2017

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Event date： 2016.12.3 - 2016.12.4

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Event date： 2016.12.3 - 2016.12.4

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Event date： 2016.12.3 - 2016.12.4

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Event date： 2016.11.3 - 2016.12.4

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Event date： 2016.10.27 - 2016.10.28

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Event date： 2016.10.27 - 2016.10.28

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Event date： 2016.10.8 - 2016.10.9

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Event date： 2016.9.16 - 2016.9.19

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Event date： 2016.8.24 - 2016.8.26

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Event date： 2016.8.24 - 2016.8.26

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Event date： 2016.7

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Event date： 2016.7

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Event date： 2016.3.18

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Event date： 2016

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Event date： 2016

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Event date： 2016

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Event date： 2016

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Event date： 2016

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Event date： 2015.3.16

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Event date： 2015

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Event date： 2015

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Event date： 2015

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Event date： 2014.10

Language：Japanese  

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Event date： 2014.3.13

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Event date： 2014

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Event date： 2014

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Event date： 2014

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Event date： 2013.3.15

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Event date： 2013

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Event date： 2013

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Event date： 2013

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Event date： 2013

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Event date： 2013

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Event date： 2012

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Event date： 2012

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Event date： 2012

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Event date： 2011

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Event date： 2011

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Event date： 2011

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Event date： 2011

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2008

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Event date： 2007.8.28 - 2007.8.29

Presentation type：Oral presentation (invited, special)  

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Event date： 2006

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Event date： 2002

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Event date： 2001

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Event date： 2000

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Event date： 1996

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Event date： 1995

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Event date： 1995

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Event date： 1994

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Event date： 1994

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Event date： 1994

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Event date： 1994

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Event date： 1994

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Event date： 1994

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Event date： 1994

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Event date： 1993

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Event date： 1993

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Event date： 1993

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Event date： 1992

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