| 1. |
- Cai, Yixiao, et al.
(författare)
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Fabrication of translucent nanoceramics via a simple filtration method
- 2015
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:121, s. 99848-99855
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Tidskriftsartikel (refereegranskat)abstract
- Generally, particle packing density, grain size and morphology are the important factors that affect the transparency of ceramics. In order to achieve better transparency of ceramics, efforts should be developed to eliminate or minimize light scattering or absorption. Therefore the porosity and size of crystals in a ceramic body should be strictly controlled. Typical transparent ceramics are fabricated by pressure-assisted sintering techniques such as hot isostatic pressing (HIP), spark plasma sintering (SPS), and pressure-less sintering (PLS). However, a simple energy efficient production method remains a challenge. In this study, we describe a simple fabrication process via a facile filtration system that can fabricate translucent hydroxyapatite based ceramics. The translucent pieces yielded from filtration exhibit optical transmittance that was confirmed by UV spectroscopy. Briefly, the morphology and size of ceramic nanoparticles, filtration pressure and filtration time are important parameters to be discussed. Compared with different hydroxyapatite nanoparticles, spherical nanoparticles easily form a densely packed structure, followed by sintered ceramics. When the strontium content in HA increases, the morphology of HA changes from nano-spheres to nano-rods, following a decrease in transparency. A pressure filtration model combining Darcy's law and the Kozeny-Carman relation has been discussed to simulate and explain why the translucent ceramics can be fabricated via such a simple process. This method could be further applied to prepare other translucent functional ceramics by controlling the size and morphology of ceramic particles.
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| 2. |
- Chen, Song, et al.
(författare)
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Synthesis of calcium phosphate crystals with thin nacreous structure
- 2016
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Ingår i: CrystEngComm. - : Royal Society of Chemistry. - 1466-8033. ; 18:6, s. 1064-1069
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Tidskriftsartikel (refereegranskat)abstract
- Nacre-like structures have attracted great interest in recent years due to their outstanding toughness, stiffness and impact resistance. However, there is a challenge associated with engineering nacre-like calcium phosphate crystals. In this study, thin nacreous-like monetite sheets were synthesized in solutions guided by a surfactant. The influence of temperature, initial pH, Ca/P ratio, stirring time and the concentration of cetyltrimethylammonium bromide (CTAB) on the nacre-like structure has been studied. Findings showed that a nacre-like structure could only be formed at a high temperature (90 °C), high initial pH (11), sufficient stirring time (3 h), and under the presence of CTAB. A small-angle X-ray scattering experiment carried out at a synchrotron radiation facility showed that the distance between nanolayers was around 2.6 nm and TEM confirmed the fine sheet-like structure. The mechanism of the formation the nacre-like structure and its characterization were discussed.
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| 3. |
- Chen, Song, et al.
(författare)
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Synthesis of calcium phosphate crystals with thin nacreous structure
- 2016
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 18:6, s. 1064-1069
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Tidskriftsartikel (refereegranskat)abstract
- Nacre-like structures have attracted great interest in recent years due to their outstanding toughness, stiffness and impact resistance. However, there is a challenge associated with engineering nacre-like calcium phosphate crystals. In this study, thin nacreous-like monetite sheets were synthesized in solutions guided by a surfactant. The influence of temperature, initial pH, Ca/P ratio, stirring time and the concentration of cetyltrimethylammonium bromide (CTAB) on the nacre-like structure has been studied. Findings showed that a nacre-like structure could only be formed at a high temperature (90 degrees C), high initial pH (11), sufficient stirring time (3 h), and under the presence of CTAB. A small-angle X-ray scattering experiment carried out at a synchrotron radiation facility showed that the distance between nanolayers was around 2.6 nm and TEM confirmed the fine sheet-like structure. The mechanism of the formation the nacre-like structure and its characterization were discussed.
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| 4. |
- Forsgren, Johan, et al.
(författare)
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A Template-Free, Ultra-Adsorbing, High Surface Area Carbonate Nanostructure
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:7, s. e68486-
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Tidskriftsartikel (refereegranskat)abstract
- We report the template-free, low-temperature synthesis of a stable, amorphous, and anhydrous magnesium carbonate nanostructure with pore sizes below 6 nm and a specific surface area of ~ 800 m2 g−1, substantially surpassing the surface area of all previously described alkali earth metal carbonates. The moisture sorption of the novel nanostructure is featured by a unique set of properties including an adsorption capacity ~50% larger than that of the hygroscopic zeolite-Y at low relative humidities and with the ability to retain more than 75% of the adsorbed water when the humidity is decreased from 95% to 5% at room temperature. These properties can be regenerated by heat treatment at temperatures below 100°C.The structure is foreseen to become useful in applications such as humidity control, as industrial adsorbents and filters, in drug delivery and catalysis.
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| 5. |
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| 6. |
- Fu, Le, et al.
(författare)
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Transparent single crystalline ZrO2-SiO2 glass nanoceramic sintered by SPS
- 2016
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 36:14, s. 3487-3494
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Tidskriftsartikel (refereegranskat)abstract
- Transparent ZrO2-SiO2 glass ceramics show potential for application in the dental industry. The application of this material prepared by a sol-gel method was hindered by the difficulties in obtaining large dimension samples. Spark plasma sintering (SPS) offers the possibility of achieving transparent ZrO2-SiO2 glass ceramics. In this study, a ZrO2-SiO2 powder was prepared by the sol-gel method and subsequently sintered by SPS. Varied sintering temperatures and pressures were explored to achieve better mechanical strength and transparency. TEM results showed single crystalline ZrO2 spherical nanocrystals (approximately 20 nm) homogenously embedded in the SiO2 matrix. Tetragonal ZrO2 was the only crystalline phase in all specimens. With sintering conditions of 1200 degrees C and 30 MPa, a glass ceramic with fracture toughness of 4.13 MPa was obtained. This value is similar to the commercial dental glass ceramic of IPS e.max (R) Press. The studied transparent glass ceramic with high transparency and moderate mechanical strength shows promise for dental application.
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| 7. |
- Gomes-Ferreira, Pedro Henrique Silva, et al.
(författare)
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PTH 1-34-functionalized bioactive glass improves peri-implant bone repair in orchiectomized rats: Microscale and ultrastructural evaluation
- 2022
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Ingår i: Biomaterials Advances. - : Elsevier BV. - 2772-9508. ; 134
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work was to investigate the use of Biogran® functionalized with parathyroid hormone (PTH) 1–34 by sonochemistry for the local delivery of this anabolic agent to the implant site. The effects of Biogran® and topical administration of PTH 1–34 on peri-implant bone regeneration were evaluated from the microscale to ultrastructural levels in healthy (SHAM) and orchiectomized (ORQ). While some animals only received a titanium implant in their tibial metaphyses (CLOT group), in others the peri-implant defect was first filled with Biogran® either without or with PTH 1–34 functionalization (BG and BGPTH groups, respectively) prior to implant installation. Osseointegration was characterized from a biomechanical perspective by measuring the removal torque with the counter-torque technique. Micro-CT was used to evaluate the percentage of bone volume, trabecular thickness, number and separation, and bone-implant contact (BIC). Dynamics of new bone formation were assessed by measuring fluorochrome area, daily mineral apposition rate, and neoformed bone area using confocal laser microscopy. RT-PCR was performed to evaluate ALP and osteocalcin expression. The interface between newly formed bone and Biogran® was examined using scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) at the micro-and nanoscale, respectively, while elemental analyses were completed in SEM with energy-dispersive X-ray spectroscopy (EDS). STEM imaging demonstrated the intimate attachment of bone to Biogran® (nanoscale level). Overall, the results suggest that the effectiveness of the topical administration of PTH 1–34 at the implant site seems enhanced in osteoporotic bone, promoting peri-implant bone regeneration to comparable levels in healthy conditions.
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| 8. |
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| 9. |
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| 10. |
- Grandfield, Kathryn, et al.
(författare)
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Bone response to free form fabricated hydroxyapatite and zirconia scaffolds : a transmission electron microscopy study in the human maxilla
- 2012
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Ingår i: Clinical Implant Dentistry and Related Research. - : Wiley. - 1523-0899 .- 1708-8208. ; 14:3, s. 461-469
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Tidskriftsartikel (refereegranskat)abstract
- Background: Understanding the interfacial reactions to synthetic bone regenerative scaffolds in vivo is fundamental for improving osseointegration and osteogenesis. Using transmission electron microscopy, it is possible to study the biological response of hydroxyapatite (HA) and zirconia (ZrO2) scaffolds at the nanometer scale.Purpose: In this study, the bone-bonding abilities of HA and ZrO2 scaffolds produced by free-form fabrication were evaluated in the human maxilla at 3 months and 7 months.Materials and Methods: HA and ZrO2 scaffolds (ø: 3 mm) were implanted in the human maxilla, removed with surrounding bone, embedded in resin, and sectioned. A novel focused ion beam (FIB) sample preparation technique enabled the production of thin lamellae for study by scanning transmission electron microscopy.Results: Interface regions were investigated using high-angle annular dark-field imaging and energy-dispersive X-ray spectroscopy analysis. Interfacial apatite layers of 80 nm and 50 nm thickness were noted in the 3- and 7-month HA samples, respectively, and bone growth was discovered in micropores up to 10 µm into the samples.Conclusions: The absence of an interfacial layer in the ZrO2 samples suggest the formation of a direct contact with bone, while HA, which bonds through an apatite layer, shows indications of resorption with increasing implantation time. This study demonstrates the potential of HA and ZrO2 scaffolds for use as bone regenerative materials.
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| 11. |
- Grandfield, Kathryn, et al.
(författare)
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Characterization of dental interfaces with electron tomography
- 2014
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 9:2, s. 029001-
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the interface between dental materials and tooth is critical in the prevention of secondary caries. Assessing this interface with high-resolution clarity has traditionally been challenging. This work highlights electron tomography, carried out in the transmission electron microscope, as a novel technique to obtain both three-dimensional and nanometer scaled information on dental materials in contact with dentin. In this study, commercial calcium aluminate and glass ionomer based luting agents in contact with human dentin were prepared for electron microscopy via focused ion beam milling. Imaging with high-angle annular dark field provided compositional contrast, and combined with tilting over large angular ranges, enabled the reconstruction of the three-dimensional interface between tissue and cement. The characteristics of the interface were observed with this extra dimensionality and superior resolution, providing evidence for the viability of this technique in interfacial studies of dental materials.
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| 12. |
- Grandfield, Kathryn, et al.
(författare)
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Effect of Calcium and Strontium on Mesoporous Titania Coatings for Implant Applications
- 2013
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Ingår i: Journal of Biomaterials and Nanobiotechnology. - : Scientific Research Publishing, Inc.. - 2158-7027 .- 2158-7043. ; 4:2, s. 107-113
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Tidskriftsartikel (refereegranskat)abstract
- ncreasing interest in the role of ions such as calcium and strontium in bone formation has called for the investigation of multifunctional ion-doped implant coatings. Mesoporous titania coatings incorporating calcium or strontium enabled a unique pore morphology and potential for drug delivery. Coatings were produced on titanium by an evaporation induced self-assembly method with the addition of calcium or strontium to the sol causing a shift in morphology from a hexagonally-packed to a worm-like porous network. Pore sizes ranged from 3.8 - 5 nm and coatings exhibited high surface areas between 181 - 215.5 m2/g, as measured by N2adsorption-desorption. Coatings were loaded with 1 mg/ml Cephalothin, and showed sustained release of the antibiotic over one week in vitro. Cell studies confirmed that the ion addition had no toxic effect on human-like osteoblastic SaOS-2 cells. The results of this study suggest the potential for mesoporous coatings with calcium or strontium incorporation for direct bone-interfacing and combined drug delivery implant applications.
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| 13. |
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| 14. |
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| 15. |
- Grandfield, Kathryn, et al.
(författare)
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Focused ion beam in the study of biomaterials and biological matter
- 2012
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Ingår i: Advances in Materials Science and Engineering. - : Hindawi Limited. - 1687-8434 .- 1687-8442. ; , s. 841961-
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Tidskriftsartikel (refereegranskat)abstract
- The application of focused ion beam (FIB) techniques in the life sciences has progressed by leaps and bounds over the past decade. A once dedicated ion beam instrument, the focused ion beam today is generally coupled with a plethora of complementary tools such as dual-beam scanning electron microscopy (SEM), environmental SEM, energy dispersive X-ray spectroscopy (EDX), or cryogenic possibilities. All of these additions have contributed to the advancement of focused ion beam use in the study of biomaterials and biological matter. Biomaterials, cells, and their interfaces can be routinely imaged, analyzed, or prepared for techniques such as transmission electron microscopy (TEM) with this comprehensive tool. Herein, we review the uses, advances, and challenges associated with the application of FIB techniques to the life sciences, with particular emphasis on TEM preparation of biomaterials, biological matter, and their interfaces using FIB.
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| 16. |
- Grandfield, Kathryn, et al.
(författare)
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Free form fabricated features on CoCr implants with and without hydroxyapatite coating in vivo : a comparative study of bone contact and bone growth induction
- 2011
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 22:4, s. 899-906
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Tidskriftsartikel (refereegranskat)abstract
- The current study evaluates the in vivo response to free form fabricated cobalt chromium (CoCr) implants with and without hydroxyapatite (HA) plasma sprayed coatings. The free form fabrication method allowed for integration of complicated pyramidal surface structures on the cylindrical implant. Implants were press fit into the tibial metaphysis of nine New Zealand white rabbits. Animals were sacrificed and implants were removed and embedded. Histological analysis, histomorphometry and electron microscopy studies were performed. Focused ion beam was used to prepare thin sections for high-resolution transmission electron microscopy examination. The fabricated features allowed for effective bone in-growth and firm fixation after 6 weeks. Transmission electron microscopy investigations revealed intimate bone-implant integration at the nanometre scale for the HA coated samples. In addition, histomorphometry revealed a significantly higher bone contact on HA coated implants compared to native CoCr implants. It is concluded that free form fabrication in combination with HA coating improves the early fixation in bone under experimental conditions.
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| 17. |
- Grandfield, Kathryn, et al.
(författare)
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High-resolution three-dimensional probes of biomaterials and their interfaces.
- 2012
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Ingår i: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences. - : The Royal Society. - 1364-503X .- 1471-2962. ; 370:1963, s. 1337-51
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Tidskriftsartikel (refereegranskat)abstract
- Interfacial relationships between biomaterials and tissues strongly influence the success of implant materials and their long-term functionality. Owing to the inhomogeneity of biological tissues at an interface, in particular bone tissue, two-dimensional images often lack detail on the interfacial morphological complexity. Furthermore, the increasing use of nanotechnology in the design and production of biomaterials demands characterization techniques on a similar length scale. Electron tomography (ET) can meet these challenges by enabling high-resolution three-dimensional imaging of biomaterial interfaces. In this article, we review the fundamentals of ET and highlight its recent applications in probing the three-dimensional structure of bioceramics and their interfaces, with particular focus on the hydroxyapatite-bone interface, titanium dioxide-bone interface and a mesoporous titania coating for controlled drug release.
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| 18. |
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| 19. |
- Grandfield, Kathryn, 1986-
(författare)
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Nanoscale Osseointegration : Characterization of Biomaterials and their Interfaces with Electron Tomography
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bone response is one of the key determining factors in the overall success of biomaterials intended for bone regeneration and osseointegration. Understanding the formation of bone at an implant surface may lead to the improved design of biomaterials for the future. However, due to the inhomogeneity of bone tissue at an interface, two-dimensional images often lack detail on the interfacial complexity. Furthermore, the increasing use of nanotechnology in the design and production of biomaterials demands characterization techniques on a similar nano length scale.While current analysis methods, such as X-ray tomography, transmission electron microscopy, focused ion beam microscopy and scanning electron microscopy, provide a basis for analysing biomaterials and biointerfaces, they are incapable of doing so with both nanometre resolution and three-dimensional clarity. In contrast, electron tomography may be used to characterize the three-dimensional structure of biomaterials and their interfaces to bone with nanometre resolution.In this work, hydroxyapatite scaffolds, and laser-modified titanium and Ti6Al4V implants were studied in contact with human or rabbit bone. Z-contrast electron tomography revealed that the orientation of collagen in bone apposing hydroxyapatite, titanium and Ti6Al4V implants is consistently parallel to the implant surface, where the bioactive layer that precipitates on HA is oriented perpendicular to the implant surface. With this method, complete three-dimensional nanoscale osseointegration of titanium-based implants was also established.The extension of this technique from interfacial analyses to the design of biomaterials provided an understanding of the pore structure of mesoporous titania. In further investigations, the open three-dimensional pore network, as revealed by electron tomography, showed promise as a coating that improves implant osseointegration and enables site-specific drug-delivery from an implant surface.In summary, it was demonstrated that two-dimensional characterization techniques were insufficient for the investigation of nanostructured biomaterials, as well as their interfaces to bone. Visualizing biointerfaces and biomaterials with nanometre precision in three-dimensions can expose new fundamental information on materials properties and bone response, enabling better design of biomaterials for the future.
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| 20. |
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| 21. |
- Grandfield, Kathryn, et al.
(författare)
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Three-dimensional structure of laser-modified Ti6Al4V and bone interface revealed with STEM tomography
- 2011
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Ingår i: Frontiers in Electron Microscopy in Materials Science.
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Konferensbidrag (refereegranskat)abstract
- The Ti6Al4V titanium alloy is one of the most routinely used materials in implant technologies. It is a suitable biomaterial due to its intrinsic mechanical properties, the excellent biocompatibility of its native surface titanium-dioxide layer, and its ability to osseointegrate. The early interaction between an implant’s surface and bone is a leading factor for implant success, where multiple surface properties contribute to improved bone anchorage. An important parameter is surface topography, both on the micron and nanoscale. Laser-modification has been performed in the thread valleys of Ti6Al4V screws to alter their surface chemistry and topography to form a nanostructured surface titanium-dioxide. Since the valley regions are associated with increased bone formation kinetics and influential to implant bonding, the modified screws may exhibit enhanced bone attachment. In order to understand the underlying mechanisms and structure of the interface to nanostructured implant surfaces, characterization techniques with sufficient resolution are needed. Z-contrast electron tomography offers the possibility to explore the interfacial structure with high-resolution in three-dimensions. Furthermore, by operating in STEM mode, artifacts arising from diffraction contrast in the crystalline implant are avoided, while a high-degree of compositional contrast is maintained in the bone matrix. The aim of the present paper was to evaluate Z-contrast electron tomography as a tool to analyze the bone interface to a nanostructured implant surface. Implants were placed in the rabbit tibia and removed with surrounding bone after 8 weeks. Focused ion beam (FIB) was used to prepare specimens for transmission electron microscopy (TEM). Elemental analysis with energy dispersive x-ray spectroscopy (EDXS) over the implant-bone interface confirms the intermixing of bone apatite and titanium dioxide. This was further substantiated with three-dimensional reconstructions created from Z-contrast electron tomograms. Collagen fibers of the surrounding bone appear to have been laid down parallel to the implant surface. Accordingly, visualization of the laser-modified interface with nanoscale three-dimensional resolution, as offered by Z-contrast electron tomography, gives new insights into bone bonding mechanisms between roughened titanium-dioxide surfaces and bone.
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| 22. |
- Grandfield, Kathryn, 1986-, et al.
(författare)
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Three-dimensional structure of laser-modified Ti6Al4V and bone interface revealed with STEM tomography
- 2013
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 127, s. 48-52
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Tidskriftsartikel (refereegranskat)abstract
- The early interaction between an implant's surface and bone is a leading factor for implant success, where multiple surface properties contribute to improved bone anchorage. An important parameter is surface topography, both on the micron and nanoscale. Laser-modification has been performed in the thread valleys of Ti6Al4V screws to alter their surface chemistry and topography to form a nanostructured surface titanium-dioxide. Implants were placed in the rabbit tibia, removed with surrounding bone after 8 weeks, fixated, dried and resin embedded. Focused ion beam milling (FIB) was used to prepare specimens from the resin blocks for transmission electron microscopy (TEM). Z-contrast electron tomography offered the possibility to explore the interfacial structure with high-resolution in three-dimensions. With this technique, collagen fibers of the surrounding bone appear to have been laid down parallel to the implant surface. Accordingly, visualization of the laser-modified interface with nanoscale three-dimensional resolution, as offered by Z-contrast electron tomography, gives new insights into bone bonding mechanisms between roughened titanium-dioxide surfaces and bone.
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| 23. |
- Grandfield, Kathryn, 1986-, et al.
(författare)
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Ultrastructural characterisation of the hydroxyapatite–coated pedicle screw and human bone interface
- 2012
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Ingår i: International Journal of Nano and Biomaterials. - 1752-8933 .- 1752-8941. ; 4:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The early fixation of pedicle screws is crucial for improving spinal stabilisation. Firm and immediate fixation between pedicle screws and bone prevents aseptic loosening and implant failure. Coating with hydroxyapatite is a possible method to improve the fixation of metallic implants in bone. In this study, scanning transmission electron microscopy (STEM) has been used to investigate the ultrastructure of the plasma–sprayed hydroxyapatite coating and human bone interface in detail. Focused ion beam sample preparation also enabled the investigation of the bone–lacunae interface. An intimate contact and elemental analysis between bone and HA coatings suggests bioactive fixation. Therefore, coating with hydroxyapatite leads to enhanced biocompatibility at the ultrastructural level and may lead to improved early and long–term fixation of pedicle screws.
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| 24. |
- Grandfield, Kathryn, et al.
(författare)
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Visualizing biointerfaces in three dimensions : electron tomography of the bone-hydroxyapatite interface
- 2010
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 7:51, s. 1497-501
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Tidskriftsartikel (refereegranskat)abstract
- A positive interaction between human bone tissue and synthetics is crucial for the success of bone-regenerative materials. A greater understanding of the mechanisms governing bone-bonding is often gained via visualization of the bone-implant interface. Interfaces to bone have long been imaged with light, X-rays and electrons. Most of these techniques, however, only provide low-resolution or two-dimensional information. With the advances in modern day transmission electron microscopy, including new hardware and increased software computational speeds, the high-resolution visualization and analysis of three-dimensional structures is possible via electron tomography. We report, for the first time, a three-dimensional reconstruction of the interface between human bone and a hydroxyapatite implant using Z-contrast electron tomography. Viewing this structure in three dimensions enabled us to observe the nanometre differences in the orientation of hydroxyapatite crystals precipitated on the implant surface in vivo versus those in the collagen matrix of bone. Insight into the morphology of biointerfaces is considerably enhanced with three-dimensional techniques. In this regard, electron tomography may revolutionize the approach to high-resolution biointerface characterization.
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| 25. |
- Grandfield, Kathryn, et al.
(författare)
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Where bone meets implant : the characterization of nano-osseointegration
- 2013
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 5:10, s. 4302-4308
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Tidskriftsartikel (refereegranskat)abstract
- The recent application of electron tomography to the study of biomaterial interfaces with bone has brought about an awareness of nano-osseointegration and, to a further extent, demanded increasingly advanced characterization methodologies. In this study, nanoscale osseointegration has been studied via laser-modified titanium implants. The micro- and nano-structured implants were placed in the proximal tibia of New Zealand white rabbits for six months. High-resolution transmission electron microscopy (HRTEM), analytical microscopy, including energy dispersive X-ray spectroscopy (EDXS) and energy-filtered TEM (EFTEM), as well as electron tomography studies were used to investigate the degree of nano-osseointegration in two- and three-dimensions. HRTEM indicated the laser-modified surface encouraged the formation of crystalline hydroxyapatite in the immediate vicinity of the implant. Analytical studies suggested the presence of a functionally graded interface at the implant surface, characterized by the gradual intermixing of bone with oxide layer. Yet, the most compelling of techniques, which enabled straightforward visualization of nano-osseointegration, proved to be segmentation of electron tomographic reconstructions, where thresholding techniques identified bone penetrating into the nanoscale roughened surface features of laser-modified titanium. Combining high-resolution, analytical and three-dimensional electron microscopy techniques has proven to encourage identification and understanding of nano-osseointegration.
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| 26. |
- Karlsson, Joakim, 1984-, et al.
(författare)
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Thickness dependency of surface properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
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Ingår i: Additive Manufacturing. - 2214-8604 .- 2214-7810.
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Tidskriftsartikel (refereegranskat)abstract
- The surface morphology of components produced by powder bed metal additive manufacturing is of interest for multiple industry sectors including biomedical and aerospace. For some applications, improvements in surface finish can reduce or eliminate the requirement for secondary finishing processes. In this study, titanium alloy (Ti6Al4V) samples were manufactured using the Electron Beam Melting (EBM) process. The effect of variations in sample thickness, powder size distribution and layer thickness were measured with three different techniques, both for direct measurement and comparison of the techniques. Ra-values in the range of 15 µm – 37 µm were obtained and varied depending on measurement technique. However, independent of technique, Ra values were found to be dependent on powder size distribution, build layer thickness, and wall thickness. Analytical transmission electron microscopy of cross sections prepared by focused ion beam milling revealed that the outermost surfaces consisted of an oxide layer of 5 nm -6 nm thickness.
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| 27. |
- Lee, Bryan, et al.
(författare)
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Dual-Topography Electric Discharge Machining of Titanium to Improve Biocompatibility
- 2016
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Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 296, s. 149-156
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Tidskriftsartikel (refereegranskat)abstract
- Surface modifications of titanium are widespread in an effort to improve the osseointegration capabilities of the metal for orthopaedic and dental applications. Here, electrical discharge machining (EDM) was used to create modified, notably, dual-topography surfaces on titanium. By swapping conventional copper electrodes for a titanium electrode and water dielectric, modified surfaces free of trace element contaminants were produced. Three surfaces were produced by varying the peak currents at 10 A, 29 A and a uniquely hierarchical multi current combination of 29 A followed by 2.4 A. The physicochemical properties of these surfaces were analyzed by scanning electron microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), and Auger Spectroscopy. These revealed the topography of the modified surfaces and a titanium oxide layer that was markedly thicker on the EDM samples compared to controls. In vitro cell testing was carried out with osteoblast-like MC3T3-E1 cells. Cell differentiation was increased in all EDM modified surfaces compared to controls and early differentiation was promoted on the dual-topography surface. The present study suggests the promise of dual-topography surfaces created using EDM for implant applications.
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| 28. |
- Micheletti, Chiara, et al.
(författare)
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Bone structure and composition in a hyperglycemic, obese, and leptin receptor-deficient rat: Microscale characterization of femur and calvarium
- 2023
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Ingår i: Bone. - 8756-3282. ; 172
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic abnormalities, such as diabetes mellitus and obesity, can impact bone quantity and/or bone quality. In this work, we characterize bone material properties, in terms of structure and composition, in a novel rat model with congenic leptin receptor (LepR) deficiency, severe obesity, and hyperglycemia (type 2 diabetes-like condition). Femurs and calvaria (parietal region) from 20-week-old male rats are examined to probe bones formed both by endochondral and intramembranous ossification. Compared to the healthy controls, the LepR-deficient animals display significant alterations in femur microarchitecture and in calvarium morphology when analyzed by micro-computed X-ray tomography (micro-CT). In particular, shorter femurs with reduced bone volume, combined with thinner parietal bones and shorter sagittal suture, point towards a delay in the skeletal development of the LepR-deficient rodents. On the other hand, LepR-deficient animals and healthy controls display analogous bone matrix composition, which is assessed in terms of tissue mineral density by micro-CT, degree of mineralization by quantitative backscattered electron imaging, and various metrics extrapolated from Raman hyperspectral images. Some specific microstructural features, i.e., mineralized cartilage islands in the femurs and hyper-mineralized areas in the parietal bones, also show comparable distribution and characteristics in both groups. Overall, the altered bone microarchitecture in the LepR-deficient animals indicates compromised bone quality, despite the normal bone matrix composition. The delayed development is also consistent with observations in humans with congenic Lep/LepR deficiency, making this animal model a suitable candidate for translational research.
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| 29. |
- Micheletti, Chiara, et al.
(författare)
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Ultrastructure and Nanoporosity of Human Bone Shown with Correlative On-Axis Electron and Spectroscopic Tomographies
- 2023
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Ingår i: ACS Nano. - 1936-0851 .- 1936-086X. ; 17:24, s. 24710-24724
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Tidskriftsartikel (refereegranskat)abstract
- Mineralized collagen fibrils are the building block units of bone at the nanoscale. While it is known that collagen fibrils are mineralized both inside their gap zones (intra-fibrillar mineralization) and on their outer surfaces (extra-fibrillar mineralization), a clear visualization of this architecture in three dimensions (3D), combining structural and compositional information over large volumes, but without compromising the resolution, remains challenging. In this study, we demonstrate the use of on-axis Z-contrast electron tomography (ET) with correlative energy-dispersive X-ray spectroscopy (EDX) tomography to examine rod-shaped samples with diameters up to 700 nm prepared from individual osteonal lamellae in the human femur. Our work mainly focuses on two aspects: (i) low-contrast nanosized circular spaces (“holes”) observed in sections of bone oriented perpendicular to the long axis of a long bone, and (ii) extra-fibrillar mineral, especially in terms of morphology and spatial relationship with respect to intra-fibrillar mineral and collagen fibrils. From our analyses, it emerges quite clearly that most “holes” are cross-sectional views of collagen fibrils. While this had been postulated before, our 3D reconstructions and reslicing along meaningful two-dimensional (2D) cross-sections provide a direct visual confirmation. Extra-fibrillar mineral appears to be composed of thin plates that are interconnected and span over several collagen fibrils, confirming that mineralization is cross-fibrillar, at least for the extra-fibrillar phase. EDX tomography shows mineral signatures (Ca and P) within the gap zones, but the signal appears weaker than that associated with the extra-fibrillar mineral, pointing toward the existence of dissimilarities between the two types of mineralization.
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| 30. |
- Olofsson, Johanna, 1981-, et al.
(författare)
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Fabrication and evaluation of SixNy coatings for total joint replacements
- 2012
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 23:8, s. 1879-1889
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Tidskriftsartikel (refereegranskat)abstract
- Wear particles from the bearing surfaces of joint implants are one of the main limiting factors for total implant longevity. Si3N4 is a potential wear resistant alternative for total joint replacements. In this study, SixNy-coatings were deposited on cobalt chromium-discs and Si-wafers by a physical vapour deposition process. The tribological properties, as well as surface appearance, chemical composition, phase composition, structure and hardness of these coatings were analysed. The coatings were found to be amorphous or nanocrystalline, with a hardness and coefficient of friction against Si3N4 similar to that found for bulk Si3N4. The low wear rate of the coatings indicates that they have a potential as bearing surfaces of joint replacements. The adhesion to the substrates remains to be improved.
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| 31. |
- Palmquist, Anders, 1977, et al.
(författare)
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Bone-titanium oxide interface in humans revealed by transmission electron microscopy and electron tomography
- 2012
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 9:67, s. 396-400
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Tidskriftsartikel (refereegranskat)abstract
- Osseointegration, the direct contact between an implant surface and bone tissue, plays a critical role in interfacial stability and implant success. Analysis of interfacial zones at the micro- and nano-levels is essential to determine the extent of osseointegration. In this paper, a series of state-of-the-art microscopy techniques are used on laser-modified implants retrieved from humans. Partially laser-modified implants were retrieved after two and a half months' healing and processed for light and electron microscopy. Light microscopy showed osseointegration, with bone tissue growing both towards and away from the implant surface. Transmission electron microscopy revealed an intimate contact between mineralized bone and the laser-modified surface, including bone growth into the nano-structured oxide. This novel observation was verified by three-dimensional Z-contrast electron tomography, enabling visualization of an apatite layer, with different crystal direction compared with the apatite in the bone tissue, encompassing the nano-structured oxide. In conclusion, the present study demonstrates the nano-scale osseointegration and bonding between apatite and surface-textured titanium oxide. These observations provide novel data in human specimens on the ultrastructure of the titanium–bone interface.
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Schwarcz, Henry, et al.
(författare)
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Effect of plate orientation on apparent thickness of mineral plates by transmission electron microscopy
- 2024
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Ingår i: JOURNAL OF BONE AND MINERAL METABOLISM. - 0914-8779 .- 1435-5604. ; 42, s. 344-351
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Tidskriftsartikel (refereegranskat)abstract
- PurposeTransmission electron microscopy (TEM) is widely used to study the ultrastructure of bone. The mineral of bone occurs as polycrystalline mineral plates about 3 to 6 nm in thickness. A problem in using TEM to make quantitative analyses of bone is that the orientation of the plates with respect to the plane of the section being imaged is expected to affect their apparent thickness. The purpose of this study was to test if this was true, if the apparent thickness of plates changed substantially as a result of tilt of the section.MethodsWe prepared TEM sections of samples of cortical human bone by ion beam milling, orienting one section parallel to the collagen fibril axes and one perpendicular to them. We obtained TEM bright field and HAADF images of these sections, tilting the sections up to +/- 20 degrees at 2 degrees intervals and measuring the apparent thickness of individual mineral platelets at each angle of tilt.ResultsThickness appears to double as section is tilted +/- 20 degrees. True thickness of plates is determined by tilting the section along an axis parallel to the plate orientation and determining the minimum apparent thickness. However, as plates are tilted away from minimum-thickness orientation, they become less well-resolved, disappearing when tilted more than 20 degrees. We therefore also measured apparent thickness of only the darkest (most electron scattering) plate images in an untilted section and obtained the same average thickness as that obtained by tilting.ConclusionWe conclude that tilting of the section is not necessary to obtain an accurate measurement of the thickness of mineral plates.
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| 36. |
- Shah, Furqan A., et al.
(författare)
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Micrometer-Sized Magnesium Whitlockite Crystals in Micropetrosis of Bisphosphonate-Exposed Human Alveolar Bone
- 2017
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 17:10, s. 6210-6216
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Tidskriftsartikel (refereegranskat)abstract
- Osteocytes are contained within spaces called lacunae and play a central role in bone remodelling. Administered frequently to prevent osteoporotic fractures, antiresorptive agents such as bi-sphosphonates suppress osteocyte apoptosis and may be localized within osteocyte lacunae. Bisphosphonates also reduce osteoclast viability and thereby hinder the repair of damaged tissue. Osteocyte lacunae contribute to toughening mechanisms. Following osteocyte apoptosis, the lacunar space undergoes mineralization, termed "micropetrosis". Hypermineralized lacunae are believed to increase bone fragility. Using nanoanalytical electron microscopy with complementary spectroscopic and crystallographic experiments, postapoptotic mineralization of osteocyte lacunae in bisphosphonate-exposed human bone was investigated. We report an unprecedented presence of similar to 80 nm to similar to 3 mu m wide, distinctly faceted, magnesium whitlockite [Ca18Mg2(HPO4)(2)(PO4)(12)] crystals and consequently altered local nanomechanical properties. These findings have broad implications on the role of therapeutic agents in driving biomineralization and shed new insights into a possible relationship between bisphosphonate exposure, availability of intracellular magnesium, and pathological calcification inside lacunae.
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| 37. |
- Skjöldebrand, Charlotte, et al.
(författare)
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Influence of Substrate Heating and Nitrogen Flow on the Composition, Morphological and Mechanical Properties of SiNx Coatings Aimed for Joint Replacements
- 2017
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nitride (SiNx) coatings are promising for joint replacement applications due to their high wear resistance and biocompatibility. For such coatings, a higher nitrogen content, obtained through an increased nitrogen gas supply, has been found to be beneficial in terms of a decreased dissolution rate of the coatings. The substrate temperature has also been found to affect the composition as well as the microstructure of similar coatings. The aim of this study was to investigate the effect of the substrate temperature and nitrogen flow on the coating composition, microstructure and mechanical properties. SiNx coatings were deposited onto CoCrMo discs using reactive high power impulse magnetron sputtering. During deposition, the substrate temperatures were set to 200 degrees C, 350 degrees C or 430 degrees C, with nitrogen-to-argon flow ratios of 0.06, 0.17 or 0.30. Scanning and transmission electron spectroscopy revealed that the coatings were homogenous and amorphous. The coatings displayed a nitrogen content of 23-48 at.% (X-ray photoelectron spectroscopy). The surface roughness was similar to uncoated CoCrMo (p = 0.25) (vertical scanning interferometry). The hardness and Young's modulus, as determined from nanoindentation, scaled with the nitrogen content of the coatings, with the hardness ranging from 12 +/- 1 GPa to 26 +/- 2 GPa and the Young's moduli ranging from 173 +/- 8 GPa to 293 +/- 18 GPa, when the nitrogen content increased from 23% to 48%. The low surface roughness and high nano-hardness are promising for applications exposed to wear, such as joint implants.
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| 38. |
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| 39. |
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| 40. |
- Thorfve, Anna, 1982, et al.
(författare)
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Three-dimensional analytical techniques for evaluation of osseointegrated titanium implants
- 2015
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Ingår i: Materials Science and Technology. - 0267-0836 .- 1743-2847. ; 31:2, s. 174-179
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Tidskriftsartikel (refereegranskat)abstract
- Osseointegration, the direct bonding of titanium implant materials with bone, is critical for implant success where nanostructured surface features contribute to nano-osseointegration. However, we also know that features and processes on the microscale influence the biocompatibility of implant materials. We highlight the advantages of using mutlilength scale analyses, focusing on three-dimensional techniques, ranging from X-ray microcomputed tomography, to focused ion beam, to high resolution electron tomography to identify markers of osseointegration. A titanium implant with modified biomimetic coating studied in vitro and in vivo at various time points is used to exemplify the complementary information gained from three-dimensional analyses from the micro- to nanoscale.
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| 41. |
- Vuong, Vicky, et al.
(författare)
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Surface and Subsurface Analyses of Metal-on-Polyethylene Total Hip Replacement Retrievals
- 2016
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Ingår i: Annals of Biomedical Engineering. - : Springer Nature. - 0090-6964 .- 1573-9686. ; 44:5, s. 1685-1697
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Tidskriftsartikel (refereegranskat)abstract
- Metal-on-polyethylene (MoP) articulations are one of the most reliable implanted hip prostheses. Unfortunately, long-term failure remains an obstacle to the service life. There is a lack of higher resolution research investigating the metallic surface component of MoP hip implants. This study investigates the surface and subsurface features of metallic cobalt chromium molybdenum alloy (CoCrMo) femoral head components from failed MoP retrievals. Unused prostheses were used for comparison to differentiate between wear-induced defects and imperfections incurred during implant manufacturing. The predominant scratch morphology observed on the non-implanted references was shallow and linear, whereas the scratches on the retrievals consisted of largely nonlinear, irregular scratches of varying depth (up to 150 nm in retrievals and up to 60 nm in reference samples). Characteristic hard phases were observed on the surface and subsurface material of the cast samples. Across all samples, a 100-400 nm thick nanocrystalline layer was visible in the immediate subsurface microstructure. Although observation of the nanocrystalline layer has been reported in metal-on-metal articulations, its presence in MoP retrievals and unimplanted prostheses has not been extensively examined. The results suggest that manufacturing-induced surface and subsurface microstructural features are present in MoP hip prostheses prior to implantation and naturally, these imperfections may influence the in vivo wear processes after implantation.
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| 42. |
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| 43. |
- Wang, Xiaoyue, et al.
(författare)
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Biomineralization at Titanium Revealed by Correlative 4D Tomographic and Spectroscopic Methods
- 2018
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 5:14
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Tidskriftsartikel (refereegranskat)abstract
- At an implant biointerface, where an engineered material merges into a biological environment, complex biophysicochemical interactions occur. One typical biointerface is the bond between human bone and dental or orthopedic implants, which is based on the biomineralization of essential bone components such as hydroxyapatite, at the implant surface. However, the exact bonding mechanism between bone and implants is still unclear. The distribution of both the mineralized and organic components of bone at the interface, and their origins, requires improved characterization. Here, the first correlative characterization is reported using multiple-length-scale tomography and spectroscopy techniques to probe the chemical structure of the biointerface between human bone and commercial titanium dental implant down to the atomic scale in four dimensions (4D). The existence of an intervening transition zone bonding mature bone tissue is demonstrated to implant at multiple length scales, where the phase of bone mineral differs immediately adjacent to the implant and atomic-scale osseointegration is confirmed. The correlative 4D electron energy loss spectroscopy tomography and atom probe tomography workflow established herein is transferable to other applications in materials or biological sciences.
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| 44. |
- Xia, Wei, et al.
(författare)
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Mesoporous titanium dioxide coating for metallic implants
- 2012
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Ingår i: Journal of Biomedical Materials Research. Part B - Applied biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 100B:1, s. 82-93
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Tidskriftsartikel (refereegranskat)abstract
- A bioactive mesoporous titanium dioxide (MT) coating for surface drug delivery has been investigated to develop a multifunctional implant coating, offering quick bone bonding and biological stability. An evaporation induced self-assembly (EISA) method was used to prepare a mesoporous titanium dioxide coating of the anatase phase with BET surface area of 172 m2/g and average pore diameter of 4.3 nm. Adhesion tests using the scratch method and an in situ screw-in/screw-out technique confirm that the MT coating bonds tightly with the metallic substrate, even after removal from bone. Because of its high surface area, the bioactivity of the MT coating is much better than that of a dense TiO2 coating of the same composition. Quick formation of hydroxyapatite (HA) in vitro can be related to enhance bonding with bone. The uptake of antibiotics by the MT coating reached 13.4 mg/cm3 within a 24 h loading process. A sustained release behavior has been obtained with a weak initial burst. By using Cephalothin as a model drug, drug loaded MT coating exhibits a sufficient antibacterial effect on the material surface, and within millimeters from material surface, against E.coli. Additionally, the coated and drug loaded surfaces showed no cytotoxic effect on cell cultures of the osteoblastic cell line MG-63. In conclusion, this study describes a novel, biocompatiblemesoporous implant coating, which has the ability to induce HA formation and could be used as a surface drug-delivery system.
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| 45. |
- Xia, Wei, et al.
(författare)
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Synthesis and release of trace elements from hollow and porous hydroxyapatite spheres
- 2011
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 22:30, s. 305610-
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Tidskriftsartikel (refereegranskat)abstract
- It is known that organic species regulate fabrication of hierarchical biological forms via solution methods. However, in this study, we observed that the presence of inorganic ions plays an important role in the formation and regulation of biological spherical hydroxyapatite formation. We present a mineralization method to prepare ion-doped hydroxyapatite spheres with a hierarchical structure that is free of organic surfactants and biological additives. Porous and hollow strontium-doped hydroxyapatite spheres were synthesized via controlling the concentration of strontium ions in a calcium and phosphate buffer solution. Similarly, fluoride and silicon-doped hydroxyapatite spheres were synthesized. While spherical particle formation was attainable at low and high temperature for Sr-doped hydroxyapatite, it was only possible at high temperature in the F/Si-doped system. The presence of inorganic ions not only plays an important role in the formation and regulation of biological spherical hydroxyapatite, but also could introduce pharmaceutical effects as a result of trace element release. Such ion release results showed a sustained release with pH responsive behavior, and significantly influenced the hydroxyapatite re-precipitation. These ion-doped hydroxyapatite spheres with hollow and porous structure could have promising applications as bone/tooth materials, drug delivery systems, and chromatography supports.
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| 46. |
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