| 1. |
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| 2. |
- Almstrand, Ann-Charlotte, et al.
(author)
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Airway monitoring by collection and mass spectrometric analysis of exhaled particles.
- 2009
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In: Analytical chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 81:2, s. 662-8
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Journal article (peer-reviewed)abstract
- We describe a new method for simultaneously collecting particles in exhaled air for subsequent chemical analysis and measuring their size distribution. After forced exhalation, particles were counted and collected in spots on silicon wafers with a cascade impactor. Several phospholipids were identified by time-of-flight secondary ion mass spectrometric analysis of the collected spots, suggesting that the particles originated from the lower airways. The amount of particles collected in ten exhalations was sufficient for characterizing the phospholipid composition. The feasibility of the technique in respiratory research is demonstrated by analysis of the phospholipid composition of exhaled particles from healthy controls, patients with asthma, and patients with cystic fibrosis. We believe this technology will be useful for monitoring patients with respiratory disease and has a high potential to detect new biomarkers in exhaled air.
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| 3. |
- Almstrand, Ann-Charlotte, et al.
(author)
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TOF-SIMS analysis of exhaled particles from patients with asthma and healthy controls.
- 2012
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In: The European respiratory journal: official journal of the European Society for Clinical Respiratory Physiology. - : European Respiratory Society (ERS). - 1399-3003 .- 0903-1936. ; 39:1, s. 59-66
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Journal article (peer-reviewed)abstract
- Particles in exhaled air (PEx) may reflect the composition of respiratory tract lining fluid (RTLF); thus, there is a need to assess their potential as sources of biomarkers for respiratory diseases. In the present study, we compared PEx from patients with asthma and controls using time-of-flight-secondary ion mass spectrometry (TOF-SIMS) and multivariate analysis. Particles were collected using an instrument developed in-house. 15 nonsmoking subjects with physician-diagnosed asthma and 11 nonsmoking healthy controls performed 10 consecutive forced exhalations into the instrument. Particle concentrations were recorded and samples of particles collected on silicon plates were analysed by TOF-SIMS. Subjects with asthma exhaled significantly lower numbers of particles than controls (p=0.03) and the ratio of unsaturated to saturated phospholipids was significantly lower in samples from subjects with asthma (0.25 versus 0.35; p=0.036). Orthogonal partial least squares-discriminant analysis models showed good separation between both positive and negative spectra. Molecular ions from phosphatidylcholine and phosphatidylglycerol, and protein fragments were found to discriminate the groups. We conclude that analysis of PEx is a promising method to examine the composition of RTLF. In the present explorative study, we could discriminate between subjects with asthma and healthy controls based on TOF-SIMS spectra from PEx.
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| 4. |
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| 5. |
- Ballo, Ahmed, 1978, et al.
(author)
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Bone response to physical-vapour-deposited titanium dioxide coatings on titanium implants
- 2013
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In: Clinical Oral Implants Research. - : Wiley. - 0905-7161 .- 1600-0501. ; 24:9, s. 1009-1017
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Journal article (peer-reviewed)abstract
- Objectives: The aim of this study was to investigate the correlation between coating thickness and the crystal structure of physical-vapour-deposited (PVD) titanium dioxide coatings, and to evaluate their in vivo biocompatibility. Materials and methods: The PVD TiO 2 coatings of different thickness were deposited on machined titanium grade 2 screw-shaped implants. Non-coated titanium implants were used as controls. Coating properties such as thickness, crystal structure, coating morphology and roughness were characterized. Forty-eight implants were placed randomly into both tibias of 16 rats. The animals were euthanized 7 and 28 days postsurgery and block biopsies were prepared for histology, histomorphometry and SEM analysis. Results: The thicknesses of the PVDTiO 2 coatings were 120 and 1430 nm respectively. Histologically, new bone formed on all implant surfaces. The mean percentage of newly formed bone in contact with the implant (BIC) was significantly higher at early healing time (7 days) for the 120 nm thick PVD coating (39 ± 14%) than for both the 1430 nm thick PVD coating (22 ± 10%) (P = 0.043) and the machined surface (22 ± 9%) (P = 0.028). This difference was no longer evident after 28 days (P = 0.867). Conclusion: Bone formation and bone-to-implant contact are achieved to the same degree for TiO 2 surface modifications prepared by a PVD process as clinically used, machined titanium. Furthermore, a relatively thinner PVD coating promotes a higher degree of bone apposition shortly after implantation, thereby providing rationales for exploring the potential clinical use of these modifications.
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| 6. |
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| 7. |
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| 8. |
- Ballo, Ahmed, 1978, et al.
(author)
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Bone tissue reactions to biomimetic ion-substituted apatite surfaces on titanium implants
- 2012
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In: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 9:72, s. 1615-1624
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Journal article (peer-reviewed)abstract
- The aim of this study was to evaluate the bone tissue response to strontium-and silicon-substituted apatite (Sr-HA and Si-HA) modified titanium (Ti) implants. Sr-HA, Si-HA and HA were grown on thermally oxidized Ti implants by a biomimetic process. Oxidized implants were used as controls. Surface properties, i.e. chemical composition, surface thickness, morphology/pore characteristics, crystal structure and roughness, were characterized with various analytical techniques. The implants were inserted in rat tibiae and block biopsies were prepared for histology, histomorphometry and scanning electron microscopy analysis. Histologically, new bone formed on all implant surfaces. The bone was deposited directly onto the Sr-HA and Si-HA implants without any intervening soft tissue. The statistical analysis showed significant higher amount of bone-implant contact (BIC) for the Si-doped HA modification (P = 0.030), whereas significant higher bone area (BA) for the Sr-doped HA modification (P = 0.034), when compared with the non-doped HA modification. The differences were most pronounced at the early time point. The healing time had a significant impact for both BA and BIC (P < 0.001). The present results show that biomimetically prepared Si-HA and Sr-HA on Ti implants provided bioactivity and promoted early bone formation.
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Ballo, Ahmed Mansour, et al.
(author)
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Osseointegration of fiber-reinforced composite implants : Histological and ultrastructural observations
- 2014
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In: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 30:12, s. e384-e395
-
Journal article (peer-reviewed)abstract
- Objectives. The aim of this study was to evaluate the bone tissue response to fiber-reinforced composite (FRC) in comparison with titanium (Ti) implants after 12 weeks of implantation in cancellous bone using histomorphometric and ultrastructural analysis. Materials and methods. Thirty grit-blasted cylindrical FRC implants with BisGMA-TEGDMA polymer matrix were fabricated and divided into three groups: (1) 60 s light-cured FRC (FRC-L group), (2) 24 h polymerized FRC (FRC group), and (3) bioactive glass FRC (FRC-BAG group). Titanium implants were used as a control group. The surface analyses were performed with scanning electron microscopy and 3D SEM. The bone-implant contact (BIC) and bone area (BA) were determined using histomorphometry and SEM. Transmission electron microscopy (TEM) was performed on Focused Ion Beam prepared samples of the intact bone-implant interface. Results. The FRC, FRC-BAG and Ti implants were integrated into host bone. In contrast, FRC-L implants had a consistent fibrous capsule around the circumference of the entire implant separating the implant from direct bone contact. The highest values of BIC were obtained with FRC-BAG (58 ± 11%) and Ti implants (54 ± 13%), followed by FRC implants (48 ± 10%), but no significant differences in BIC or BA were observed (p = 0.07, p = 0.06, respectively). TEM images showed a direct contact between nanocrystalline hydroxyapatite of bone andboth FRC and FRC-BAG surfaces. Conclusion. Fiber-reinforced composite implants are capable of establishing a close bone contact comparable with the osseointegration of titanium implants having similar surface roughness.
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| 13. |
- Ballo, Ahmed, 1978, et al.
(author)
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Nanostructured model implants for in vivo studies: influence of well-defined nanotopography on de novo bone formation on titanium implants
- 2011
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In: International Journal of Nanomedicine. - 1178-2013 .- 1176-9114. ; 6, s. 3415-28
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Journal article (peer-reviewed)abstract
- An implantable model system was developed to investigate the effects of nanoscale surface properties on the osseointegration of titanium implants in rat tibia. Topographical nanostructures with a well-defined shape (semispherical protrusions) and variable size (60 nm, 120 nm and 220 nm) were produced by colloidal lithography on the machined implants. Furthermore, the implants were sputter-coated with titanium to ensure a uniform surface chemical composition. The histological evaluation of bone around the implants at 7 days and 28 days after implantation was performed on the ground sections using optical and scanning electron microscopy. Differences between groups were found mainly in the new bone formation process in the endosteal and marrow bone compartments after 28 days of implantation. Implant surfaces with 60 nm features demonstrated significantly higher bone-implant contact (BIC, 76%) compared with the 120 nm (45%) and control (57%) surfaces. This effect was correlated to the higher density and curvature of the 60 nm protrusions. Within the developed model system, nanoscale protrusions could be applied and systematically varied in size in the presence of microscale background roughness on complex screw-shaped implants. Moreover, the model can be adapted for the systematic variation of surface nanofeature density and chemistry, which opens up new possibilities for in vivo studies of various nanoscale surface-bone interactions.
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| 14. |
- Bredberg, Anna, et al.
(author)
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Comparison of Exhaled Endogenous Particles from Smokers and Non-Smokers Using Multivariate Analysis
- 2013
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In: Respiration. - : S. Karger AG. - 0025-7931 .- 1423-0356. ; 86:2, s. 135-142
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Journal article (peer-reviewed)abstract
- Background: Smoking, along with many respiratory diseases, has been shown to induce airway inflammation and alter the composition of the respiratory tract lining fluid (RTLF). We have previously shown that the phospholipid and protein composition of particles in exhaled air (PEx) reflects that of RTLF. In this study, we hypothesized that the composition of PEx differs between smokers and non-smokers, reflecting inflammation in the airways. Objective: It was the aim of this study to identify differences in the phospholipid composition of PEx from smokers and non-smokers. Methods: PEx from 12 smokers and 13 non-smokers was collected using a system developed in-house. PEx was analysed using time-of-flight secondary ion mass spectrometry, and the mass spectral data were evaluated using multivariate analysis. Orthogonal partial least squares (OPLS) was used to relate smoking status, lung function and pack years to the chemical composition of RTLF. The discriminating ions identified by OPLS were then used as explanatory variables in traditional regression analysis. Results: There was a clear discrimination between smokers and non-smokers according to the chemical composition, where phospholipids from smokers were protonated and sodiated to a larger extent. Poor lung function showed a strong association with higher response from all molecular phosphatidylcholine species in the samples. Furthermore, the accumulated amount of tobacco consumed was associated with variations in mass spectra, indicating a dose-response relationship. Conclusion: The chemical composition of PEx differs between smokers and nonsmokers, reflecting differences in the RTLF. The results from this study may suggest that the composition of RTLF is affected by smoking and may be of importance for lung function.
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| 15. |
- Bryne, Lars-Elof, et al.
(author)
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Ageing of modified wood : Part 2: Determination of surface composition of acetylated, furfurylated, and thermally modified wood by XPS and ToF-SIMS
- 2010
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In: Holzforschung. - 0018-3830 .- 1437-434X. ; 64:3, s. 305-313
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Journal article (peer-reviewed)abstract
- The main objective of this work was to study the chemical composition of surfaces and ageing effects on acetylated pine (Pinus sylvestris), heat treated spruce (Picea abies), and furfurylated radiata pine (Pinus radiata) in comparison to unmodified wood. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were the instruments of choice. Observation with a low-vacuum scanning electron microscope (LV-SEM) complemented the study. The spectroscopic information was also linked to a parallel wettability study on matched wood samples by the Wilhelmy method. The results show that XPS and ToF-SIMS are two powerful tools that in combination give complementary information, both quantitative and qualitative, and are well suited for observation of the ageing process of different wood surfaces. The hydrophobization process as a result of migration of extractives during ageing was well quantified by the XPS measurements and the results correlated well with wetting results. Several specific hydrophobic substances could be identified by ToF-SIMS measurements.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- de Peppo, Giuseppe Maria, 1981, et al.
(author)
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Free-form-fabricated commercially-pure Ti and Ti6Al4V porous scaffolds support the growth of human embryonic stem cell-derived medsodermal progenitors
- 2012
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In: The Scientific World Journal. - : Hindawi Limited. - 2356-6140 .- 1537-744X. ; 2012
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Journal article (peer-reviewed)abstract
- Commercially-pure titanium (cp-Ti) and the titanium-aluminum-vanadium alloy (Ti6Al4V) are widely used as reconstructive implants for skeletal engineering applications, due to their good mechanical properties, biocompatibility and ability to integrate with the surrounding bone. Electron beam melting technology (EBM) allows the fabrication of customized implants with tailored mechanical properties and high potential in the clinical practice. In order to augment the interaction with the biological tissue, stem cells have recently been combined with metallic scaffolds for skeletal engineering applications. We previously demonstrated that human embryonic stem cell-derived mesodermal progenitors (hES-MPs) hold a great potential to provide a homogeneous and unlimited supply of cells for bone engineering applications. This study demonstrates the effect of EBM-fabricated cp-Ti and Ti6Al4V porous scaffolds on hES-MPs behavior, in terms of cell attachment, growth and osteogenic differentiation. Displaying different chemical composition but similar surface properties, EBM-fabricated cp-Ti and Ti6Al4V scaffolds supported cell attachment and growth, and did not seem to alter the expression of genes involved in osteogenic differentiation and affect the alkaline phosphatase activity. In conclusion, interfacing hES-MPs to EBM-fabricated scaffolds may represent an interesting strategy for design of third-generation biomaterials, with the potential to promote implant integration in clinical conditions characterized by poor bone quality. Copyright 2012 G. M. de Peppo et al.
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| 20. |
- de Peppo, Giuseppe Maria, et al.
(author)
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Osteogenic response of human mesenchymal stem cells to well-defined nanoscale topography in vitro
- 2014
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In: International Journal of Nanomedicine. - 1176-9114 .- 1178-2013. ; 9:1, s. 2499-2515
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Journal article (peer-reviewed)abstract
- Background: Patterning medical devices at the nanoscale level enables the manipulation of cell behavior and tissue regeneration, with topographic features recognized as playing a significant role inthe osseointegration of implantable devices. Methods: In this study, we assessed the ability of titanium-coated hemisphere-like topographic nanostructures of different sizes (approximately 50, 100, and 200 nm) to influence the morphology, proliferation, and osteogenic differentiation of human mesenchymal stem cells (hMSCs). Results: We found that the proliferation and osteogenicdifferentiation of hMSCs was influenced by the size of the underlying structures, suggesting that size variations in topographic features at the nanoscale level, independently of chemistry, can be exploited to control hMSC behavior in a size-dependent fashion. Conclusion: Our studies demonstrate that colloidal lithography, in combination with coating technologies, can be exploited to investigate the cell response to well defined nanoscale topography and to develop next-generation surfaces that guide tissue regeneration and promote implant integration.
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| 21. |
- de Peppo, Giuseppe Maria, 1981, et al.
(author)
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Osteogenic response of human mesenchymal stem cells to well-defined nanoscale topography in vitro
- 2014
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In: International journal of nanomedicine. - : Informa UK Limited. - 1176-9114 .- 1178-2013. ; 9:1, s. 2499-2515
-
Journal article (peer-reviewed)abstract
- Background: Patterning medical devices at the nanoscale level enables the manipulation of cell behavior and tissue regeneration, with topographic features recognized as playing a significant role in the osseointegration of implantable devices. Methods: In this study, we assessed the ability of titanium-coated hemisphere-like topographic nanostructures of different sizes (approximately 50, 100, and 200 nm) to influence the morphology, proliferation, and osteogenic differentiation of human mesenchymal stem cells (hMSCs). Results: We found that the proliferation and osteogenic differentiation of hMSCs was influenced by the size of the underlying structures, suggesting that size variations in topographic features at the nanoscale level, independently of chemistry, can be exploited to control hMSC behavior in a size-dependent fashion. Conclusion: Our studies demonstrate that colloidal lithography, in combination with coating technologies, can be exploited to investigate the cell response to well defined nanoscale topography and to develop next-generation surfaces that guide tissue regeneration and promote implant integration.
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| 22. |
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| 23. |
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| 24. |
- Eriksson, Cecilia, et al.
(author)
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Interactions between human whole blood and modified TiO2-surfaces : Influence of surface topography and oxide thickness on leukocyte adhesion and activation
- 2001
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In: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 22:14, s. 1987-1996
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Journal article (peer-reviewed)abstract
- An in vitro model (Nygren et al., J Lab Clin Med 129 (1997) 35-46) was used to investigate interactions between leukocytes and four modified TiO2-surfaces. Surface topography was measured using scanning electron microscopy and optical profilometry while Auger electron spectroscopy was used to determine surface composition and oxide thickness. The surfaces were either smooth or rough with either thin or thick oxides. All surfaces consisted of TiO2 covered by a carbonaceous layer. The surfaces were incubated with capillary blood for time periods of between 8 min and 32h. Immunofluorescence techniques together with computer aided image analysis and chemiluminescence technique were used to detect cell adhesion, expression of adhesion receptors and the zymosan-stimulated respiratory burst response. Leukocyte adhesion to the surfaces increased during the first hours of blood-material contact and then decreased. Polymorphonuclear granulocytes were the dominating leukocytes on all surfaces followed by monocytes. Cells adhering to rough surfaces had higher normalized expression of adhesive receptors than cells on smooth surfaces. Maximum respiratory burst response occurred earlier on the smooth than on the rough surfaces. In conclusion, topography had a greater impact than oxide thickness on most cellular reactions investigated, but the latter often had a dampening effect on the responses. (C) 2001 Elsevier Science Ltd. All rights reserved.
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| 25. |
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| 26. |
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| 27. |
- Gabriel, B. L., et al.
(author)
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Site-specific adhesion of Staphylococcus epidermidis (RP12) in Ti-Al-V metal systems
- 1994
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In: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 15:8, s. 628-634
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Journal article (peer-reviewed)abstract
- Staphylococcus epidermidis (RP12) adhesion patterns were studied on the following titanium (Ti)-aluminium (Al)-vanadium (V) metal systems: (i) microfabricated samples consisting of Ti, Al and V islands deposited onto Ti or V substrata, (ii) pure Ti, Al and V metals, and (iii) medical grade Ti6Al4-V alloy. All of these surfaces were covered with their respective oxides formed upon exposure of the metals to air. Quantitative analysis of the number of cells bound per unit area indicates that S. epidermidis (RP12) exhibits greatest adhesion to pure V surfaces. When exposed to surfaces having controlled spatial variations in chemical composition on the 10 mu m scale (microfabricated samples), the bacteria preferentially populate V islands versus Ti or Al substrata. In the case of the biphasic Ti6Al4V alloy, the bacteria tend to adhere to V-rich, mixed phase regions and phase boundaries. These findings demonstrate that enhanced and preferential adhesion of S. epidermidis (RP12) occurs on V surfaces in TI-Al-V metal systems and suggest that bacterial interactions are influenced by surface oxide composition.
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| 28. |
- Hansson, Marie, 1979, et al.
(author)
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Iodine content and distribution in extratumoral and tumor thyroid tissue analyzed with X-ray fluorescence and time-of-flight secondary ion mass spectrometry.
- 2008
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In: Thyroid : official journal of the American Thyroid Association. - : Mary Ann Liebert Inc. - 1557-9077. ; 18:11, s. 1215-20
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Journal article (peer-reviewed)abstract
- BACKGROUND: The thyroid's ability to enrich and store iodine has implications for thyroid cancer genesis, progression, and treatment. The study objective was to investigate thyroid iodine content (TIC) in tumoral and extratumoral tissue in patients with papillary thyroid cancer (PTC) as opposed to thyroid healthy controls using two different techniques: X-ray fluorescence (XRF) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). METHODS: Tissue samples from 10 patients with normal thyroids and 7 patients with PTC were collected. TIC was quantified with XRF, and the iodine stores were located on a histological level with TOF-SIMS. RESULTS: Mean TIC in controls was 0.6 mg/mL (range 0.3-1.2 mg/mL). For the cancer patients, the mean TIC was 0.8 mg/mL (range 0.2-2.3 mg/mL) in extratumoral thyroid tissue, but no iodine was detected in the tumors. TOF-SIMS investigation of the PTC patients showed significantly higher TIC in extratumoral tissue than in tumoral tissue. Iodine in the extratumoral tissue was predominantly located in the follicle lumen with a variation in concentration among follicles. CONCLUSIONS: XRF and TOF-SIMS are two complementary methods for obtaining insight into content and localization of iodine in the thyroid. XRF can be used in vitro or in vivo on a large number of samples or patients, respectively. TOF-SIMS on the other hand provides detailed images of the iodine location. The combined information from the two methods is of value for further studies on iodine metabolism in thyroid malignancy.
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| 29. |
- Hansson, Marie, 1979, et al.
(author)
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Iodine Content and Distribution in Thyroid Specimens from Two Patients with Graves' Disease Pretreated with Either Propylthiouracil or Stable Iodine: Analysis Using X-Ray Fluorescence and Time-of-Flight Secondary Ion Mass Spectrometry.
- 2012
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In: Case reports in endocrinology. - : Hindawi Limited. - 2090-651X .- 2090-6501. ; 2012
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Journal article (peer-reviewed)abstract
- Patients with Graves' disease can be medically prepared before surgery in different ways, which may have various effects on iodine stores. Thyroid specimens were collected at surgery from two patients pretreated with propylthiouracil (PTU) and stable iodine, respectively. A quantitative analysis of iodine content was performed using X-ray fluorescence (XRF) in frozen tissue and a qualitative analysis of aldehyde-fixed material with Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). Iodine concentrations were 0.9mg/mL and 0.5mg/mL in the thyroid tissue from the patients treated with PTU and stable iodine respectively. TOF-SIMS showed iodine in the follicle lumina in both. However, in the PTU case, iodine was also seen within the thyrocytes indicating accumulation of iodinated compounds from uninhibited hormone release. XRF and TOF-SIMS can be used to follow iodine distribution within the thyroid and the intricate processes following the different medical treatment alternatives in Graves' disease.
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| 30. |
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| 31. |
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| 32. |
- Hoseini, Mohammed, et al.
(author)
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Tribological investigation of oriented HDPE
- 1999
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In: Proc. Polymer Processing Society, Asia/Australia Regional Meeting, Bangkok, Dec. 1999..
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Conference paper (other academic/artistic)
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| 33. |
- Hulander, Mats, et al.
(author)
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Immune complement activation is attenuated by surface nanotopography
- 2011
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In: International Journal of Nanomedicine. - 1176-9114 .- 1178-2013. ; 6, s. 2653-2666
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Journal article (peer-reviewed)abstract
- The immune complement (IC) is a cell-free protein cascade system, and the first part of the innate immune system to recognize foreign objects that enter the body. Elevated activation of the system from, for example, biomaterials or medical devices can result in both local and systemic adverse effects and eventually loss of function or rejection of the biomaterial. Here, the researchers have studied the effect of surface nanotopography on the activation of the IC system. By a simple nonlithographic process, gold nanoparticles with an average size of 58 nm were immobilized on a smooth gold substrate, creating surfaces where a nanostructure is introduced without changing the surface chemistry. The activation of the IC on smooth and nanostructured surfaces was viewed with fluorescence microscopy and quantified with quartz crystal microbalance with dissipation monitoring in human serum. Additionally, the ability of pre-adsorbed human immunoglobulin G (IgG) (a potent activator of the IC) to activate the IC after a change in surface hydrophobicity was studied. It was found that the activation of the IC was significantly attenuated on nanostructured surfaces with nearly a 50% reduction, even after pre-adsorption with IgG. An increase in surface hydrophobicity blunted this effect. The possible role of the curvature of the nanoparticles for the orientation of adsorbed IgG molecules, and how this can affect the subsequent activation of the IC, are discussed. The present findings are important for further understanding of how surface nanotopography affects complex protein adsorption, and for the future development of biomaterials and blood-contacting devices.
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| 34. |
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| 35. |
- Johansson, Bo-Lennart, et al.
(author)
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Chemical characterisation of different separation media based on agarose by static time-of-flight secondary ion mass spectrometry
- 2004
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1023:1, s. 49-56
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Journal article (peer-reviewed)abstract
- In this paper, the novel application of time-of-flight secondary ion mass spectrometry (TOF-SIMS) for qualitative and semi-quantitative investigation of the surface chemistry of separation media based on beaded agarose is reported. Five different media were studied: DEAE Sepharose Fast Flow, Q Sepharose Fast Flow, SP Sepharose Fast Flow, Phenyl Sepharose Fast Flow at ligand densities between 7 and 33% (w/w) and the base matrix Sepharose 6 Fast Flow. The obtained TOF-SIMS spectra reveal significant chemical information regarding the ligands (DEAE, Q, SP and Phenyl) which are covalently attached to the agarose-based matrix Sepharose 6 Fast Flow. For the anion-exchange media (DEAE and Q Sepharose Fast Flow), the positive TOF-SIMS spectra yielded several strong characteristic fragment peaks from the amine ligands. Structural information was obtained, e.g. from the peak at m/z 173.20, originating from the ion structure [(C2H5)2NCH2CH2NH(C2H5)2l+, which shows that the ligand in DEAE Sepharose Fast Flow is composed of both tertiary and quaternary amines. The positive spectrum of Phenyl Sepharose Fast Flow contained major fragments both from the base matrix and the ligand. The cation-exchanger (SP Sepharose Fast Flow) gave rise to a positive spectrum resembling that of the base matrix (Sepharose 6 Fast Flow) but with a different intensity pattern of the matrix fragments. In addition, peaks with low intensity at m/z 109.94, 125.94 and 139.95 corresponding to Na2SO2+, Na2SO3+ and Na2SO3CH2+, respectively, were observed. The positive TOF-SIMS spectrum of Sepharose 6 Fast Flow contains a large number of fragments in the mass range up to m/z 200 identified as CxHyOz and CxHy structures. The results clearly show that positive TOF-SIMS spectra of different media based on Sepharose 6 Fast Flow are strongly influenced by the ligand coupled to the matrix. The negative TOF-SIMS spectra contained several ligand-specific, characteristic peaks for the cation-exchanger, having sulphonate as the ion-exchange group. Negative fragments such as S-, SO-, SO2-, SO3-, C2H3SO3-, C3H5SO3- and OC3H5SO3- were observed. Phenyl Sepharose Fast Flow, which has an uncharged group (Phenyl) coupled to the agarose matrix yielded one ligand-related peak corresponding to the C6H5O- fragment. DEAE and Q ligands could only be identified by the appearance of the fragments CN- and CNO- in the negative spectrum. However, a strong peak corresponding to the counter ion (Cl-) was observed. TOF-SIMS analysis can also be used for the investigation of residues from the coupling procedure that bonds the ligands to the matrix. One example is the observation of bromine peaks in the negative spectrum of Q Sepharose Fast Flow. Furthermore, it has also been shown that different ligand concentrations of Phenyl Sepharose Fast Flow can easily be detected by TOF-SIMS analysis. Information regarding the difference between the ligand density on the surface of the beads and in the bulk can also be obtained. However, spectra registered on the outermost surface and on the pore surface (crushed beads) of DEAE Sepharose Fast Flow clearly show that the agarose and the DEAE groups are homogeneously distributed in the beads.
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| 36. |
- Karlsson, Joakim, et al.
(author)
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Characterization and comparison of materials produced by Electron Beam Melting (EBM) of two different Ti-6Al-4V powder fractions
- 2013
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In: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 213:12, s. 2109-2118
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Journal article (peer-reviewed)abstract
- Electron Beam Melting (EBM) has been recognized as a revolutionary technique to produce mass-customized parts to near-net-shape from various metallic materials. The technique produces parts with unique geometries from a powder stock material and uses an electron beam to melt the powder layer-by-layer to fully solid structures. In this study we have investigated the use of two different Ti-6Al-4V powders of different size fractions in the EBM process; a larger 45-100 mu m powder, and a smaller 25-45 mu m powder. We have also investigated the effects of two build layer thicknesses, 70 mu m and 50 mu m. respectively. We hypothesize that the smaller powder has the potential to improve surface resolution of parts produced in the EBM process. The EBM as-built parts were investigated regarding surface and bulk chemistry, surface oxide thickness, macro- and microstructure, surface appearance and mechanical properties. We conclude from the results that both powders and both build layer thicknesses are feasible to use in the EBM process. The investigated material properties were not significantly affected by powder size or layer thickness within the studied range of process parameters. However, the surface appearance was found to be different for the samples made with the different powder sizes.
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| 37. |
- Karlsson, Joakim, 1984-, et al.
(author)
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Digital image correlation analysis of local strain fields on Ti6Al4V manufactured by electron beam melting
- 2014
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In: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 618, s. 456-461
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Journal article (peer-reviewed)abstract
- Additive manufacturing, or 3D-printing as it is often called, build parts in a layer-by-layer fashion. A common concern, regardless of the specific additive manufacturing technique used, is the risk of inadequate fusion between the adjacent layers which in turn may cause inferior mechanical properties. In this work, the local strain properties of titanium parts produced by Electron Beam Melting (EBM®) were studied in order to gain information about the quality of fusion of the stock powder material used in the process. By using Digital Image Correlation (DIC) the strain fields in the individual layers were analyzed, as well as the global strain behavior of the bulk material. The results show that fully solid titanium parts manufactured by EBM are homogenous and do not experience local deformation behavior, neither on local nor on a global level.
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| 38. |
- Karlsson, Joakim, 1984-, et al.
(author)
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Surface oxidation behavior of Ti-6Al-4V manufactured by Electron Beam Melting (EBM®)
- 2015
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In: Journal of Manufacturing Processes. - : Elsevier BV. - 1526-6125. ; 17, s. 120-126
-
Journal article (peer-reviewed)abstract
- Additive manufacturing is an emerging manufacturing technology that enables production of patient specific implants, today primarily out of titanium. For optimal functionality and proper integration between the titanium implant and the body tissues surface properties, such as surface oxide thickness is of particular importance, as it is primarily the surface of the material which interacts with the body. Hence, in this study the surface oxidation behavior of titanium parts manufactured by Electron Beam Melting (EBM®) is investigated using the surface sensitive techniques ToF-SIMS and AES. Oxide thicknesses comparable to those found on conventionally machined surfaces are found by both analysis techniques. However, a build height dependency is discovered for different locations of the EBM® manufactured parts due to the presence of trapped moisture in the machine and temperature gradients in the build.
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| 39. |
- Karlsson, Joakim, 1984-, et al.
(author)
-
Thickness dependency of mechanical properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
- 2024
-
In: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810.
-
Journal article (peer-reviewed)abstract
- Metal powder bed additive manufacturing technologies, such as the Electron Beam Melting process, facilitate a high degree of geometric flexibility and have been demonstrated as useful production techniques for metallic parts. However, the EBM process is typically associated with lower resolutions and higher surface roughness compared to similar laser-based powder bed metal processes. In part, this difference is related to the larger powder size distribution and thicker layers normally use As part of an effort to improve the resolution and surface roughness of EBM fabricated components, this study investigates the feasibility of fabricating components with a smaller powder size fraction and layer thickness (similar to laser based processes). The surface morphology, microstructure and tensile properties of the produced samples were evaluated. The findings indicate that microstructure is dependent on wall-thickness and that, for thin walled structures, tensile properties can become dominated by variations in surface roughness.
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| 40. |
- Karlsson, Joakim, 1984-, et al.
(author)
-
Thickness dependency of surface properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
-
In: Additive Manufacturing. - 2214-8604 .- 2214-7810.
-
Journal article (peer-reviewed)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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| 41. |
- Kesteris, Uldis, et al.
(author)
-
Contamination of polyethylene cups with polymethyl methacrylate particles: an experimental study
- 2001
-
In: Journal of Arthroplasty. - : Elsevier BV. - 0883-5403. ; 16:7, s. 905-908
-
Journal article (peer-reviewed)abstract
- The articulating surfaces of 6 ultra-high molecular weight polyethylene cups were exposed to curing polymethyl methacrylate (PMMA) bone-cement and examined with scanning electron microscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Three of the cups were exposed to blood and bone-cement, and the rest were exposed to bone-cement only. After removal of the bone-cement bulk, PMMA particles were found and identified in all 6 cups. The particles were verified by identifying zirconium with energy-dispersive x-ray fluorescence spectroscopy in 5 cups and with LA-ICPMS in 1 cup. The degree of surface contamination was estimated with LA-ICPMS. The number of zirconium-containing particles detected was on average 10 to 20/mm2. PMMA bone-cement left in polyethylene cups during polymerization can contaminate the articulating surface with adherent PMMA particles.
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| 42. |
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| 43. |
- Larsson Wexell, Cecilia, 1965, et al.
(author)
-
Bone response to surface-modified titanium implants : Studies on the early tissue response to implants with different surface characteristics
- 2013
-
In: International Journal of Biomaterials. - : Hindawi Limited. - 1687-8787 .- 1687-8795.
-
Journal article (peer-reviewed)abstract
- In a series of experimental studies, the bone formation around systematically modified titanium implants is analyzed. In the present study, three different surface modifications were prepared and evaluated. Glow-discharge cleaning and oxidizing resulted in a highly stoichiometric TiO2 surface, while a glow-discharge treatment in nitrogen gas resulted in implants with essentially a surface of titanium nitride, covered with a very thin titanium oxide. Finally, hydrogen peroxide treatment of implants resulted in an almost stoichiometric TiO2, rich in hydroxyl groups on the surface. Machined commercially pure titanium implants served as controls. Scanning Auger Electron Spectroscopy, Scanning Electron Microscopy, and Atomic Force Microscopy revealed no significant differences in oxide thickness or surface roughness parameters, but differences in the surface chemical composition and apparent topography were observed. After surface preparation, the implants were inserted in cortical bone of rabbits and evaluated after 1, 3, and 6 weeks. Light microscopic evaluation of the tissue response showed that all implants were in contact with bone and had a large proportion of newly formed bone within the threads after 6 weeks. There were no morphological differences between the four groups. Our study shows that a high degree of bone contact and bone formation can be achieved with titanium implants of different surface composition and topography.
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| 44. |
- Larsson Wexell, Cecilia, 1965, et al.
(author)
-
Bone response to surface modified titanium implants: studies on electropolished implants with different oxide thicknesses and morphology.
- 1994
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In: Biomaterials. - 0142-9612. ; 15:13, s. 1062-74
-
Journal article (peer-reviewed)abstract
- In a series of experimental studies, bone formation was analysed around systematically modified titanium implants. In the present study, machined, electropolished and anodically oxidized implants were prepared, surface characterized and inserted in the cortical bone of rabbits (7 wks and 12 wks). SEM, scanning Auger electron spectroscopy and atomic force microscopy revealed no differences in surface composition but marked differences in oxide thickness, surface topography and roughness. Light microscopic morphology and morphometry showed that all implants were in contact with bone, and had a large proportion of bone within the threads. The smooth, electropolished implants were surrounded by less bone than the machined implants with similar oxide thickness, (4-5 nm) and the anodically oxidized implants with thicker oxides (21 nm and 180 nm, respectively) after 7 wks. These studies show that a high degree of bone contact and bone formation can be achieved with titanium implants which are modified with respect to oxide thickness and surface topography. However, it appears that a reduction of surface roughness may influence the rate of bone formation in rabbit cortical bone.
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| 45. |
- Larsson Wexell, Cecilia, 1965, et al.
(author)
-
Bone response to surface-modified titanium implants: studies on the early tissue response to machined and electropolished implants with different oxide thicknesses.
- 1996
-
In: Biomaterials. - 0142-9612. ; 17:6, s. 605-16
-
Journal article (peer-reviewed)abstract
- The bone formation around titanium implants with varied surface properties is investigated. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits (1, 3 and 6 weeks). Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition, between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads at 6 weeks. The smooth, electropolished implants, irrespective of anodic oxidation, were surrounded by less bone than the machined implants after 1 week. After 6 weeks the bone volume as well as the bone-implant contact were lower for the merely electropolished implants than for the other three groups. Our study shows that a high degree of bone contact and bone formation are achieved with titanium implants which are modified with respect to oxide thickness and surface topography. However, the result with the smooth (electropolished) implants indicates that a reduction of surface roughness, in the initial phase, decreases the rate of bone formation in rabbit cortical bone.
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| 46. |
- Larsson Wexell, Cecilia, 1965, et al.
(author)
-
Bone response to surface modified titanium implants - studies on the tissue response after 1 year to machined and electropolished implants with different oxide thicknesses.
- 1997
-
In: Journal of materials science. Materials in medicine. - 0957-4530. ; 8:12, s. 721-9
-
Journal article (peer-reviewed)abstract
- The bone formation around titanium implants with varied surface properties was investigated after 1 year in rabbits. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits. Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads. There were no significant differences between the differently prepared implant groups. Our study shows that a high degree of bone contact and bone formation is achieved after 1 year with titanium implants which are modified with respect to oxide thickness and surface topography. There is no indication that a reduction of surface roughness, which in the initial phase decreases the rate of bone formation, had any influence on the amount of bone after 1 year in rabbit cortical bone.
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| 47. |
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| 48. |
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| 49. |
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| 50. |
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