| 1. |
- Palmquist, Anders, 1977, et al.
(author)
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Complex geometry and integrated macro-porosity: Clinical applications of electron beam melting to fabricate bespoke bone-anchored implants
- 2023
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In: Acta Biomaterialia. - : Elsevier BV. - 1742-7061 .- 1878-7568. ; 156, s. 125-145
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Research review (peer-reviewed)abstract
- The last decade has witnessed rapid advancements in manufacturing technologies for biomedical implants. Additive manufacturing (or 3D printing) has broken down major barriers in the way of producing complex 3D geometries. Electron beam melting (EBM) is one such 3D printing process applicable to metals and alloys. EBM offers build rates up to two orders of magnitude greater than comparable laser-based technologies and a high vacuum environment to prevent accumulation of trace elements. These features make EBM particularly advantageous for materials susceptible to spontaneous oxidation and nitrogen pick-up when exposed to air (e.g., titanium and titanium-based alloys). For skeletal reconstruction(s), anatomical mimickry and integrated macro-porous architecture to facilitate bone ingrowth are undoubtedly the key features of EBM manufactured implants. Using finite element modelling of physiological loading conditions, the design of a prosthesis may be further personalised. This review looks at the many unique clinical applications of EBM in skeletal repair and the ground-breaking innovations in prosthetic rehabilitation. From a simple acetabular cup to the fifth toe, from the hand-wrist complex to the shoulder, and from vertebral replacement to cranio-maxillofacial reconstruction, EBM has experienced it all. While sternocostal reconstructions might be rare, the repair of long bones using EBM manufactured implants is becoming exceedingly frequent. Despite the various merits, several challenges remain yet untackled. Nevertheless, with the capability to produce osseointegrating implants of any conceivable shape/size, and permissive of bone ingrowth and functional loading, EBM can pave the way for numerous fascinating and novel applications in skeletal repair, regeneration, and rehabilitation. Statement of significance: Electron beam melting (EBM) offers unparalleled possibilities in producing contaminant-free, complex and intricate geometries from alloys of biomedical interest, including Ti6Al4V and CoCr. We review the diverse range of clinical applications of EBM in skeletal repair, both as mass produced off-the-shelf implants and personalised, patient-specific prostheses. From replacing large volumes of disease-affected bone to complex, multi-material reconstructions, almost every part of the human skeleton has been replaced with an EBM manufactured analog to achieve macroscopic anatomical-mimickry. However, various questions regarding long-term performance of patient-specific implants remain unaddressed. Directions for further development include designing personalised implants and prostheses based on simulated loading conditions and accounting for trabecular bone microstructure with respect to physiological factors such as patient's age and disease status.
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| 2. |
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| 3. |
- Karlsson, Johan, 1984, et al.
(author)
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Stem cell homing using local delivery of plerixafor and stromal derived growth factor-1alpha for improved bone regeneration around Ti-implants
- 2016
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In: Journal of Biomedical Materials Research - Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 104:10, s. 2466-2475
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Journal article (peer-reviewed)abstract
- Triggering of the early healing events, including the recruitment of progenitor cells, has been suggested to promote bone regeneration. In implantology, local drug release technologies could provide an attractive approach to promote tissue regeneration. In this study, we targeted the chemotactic SDF-1a/CXCR4 axis that is responsible e.g. for the homing of stem cells to trauma sites. This was achieved by local delivery of plerixafor, an antagonist to CXCR4, and/or SDF-1a from titanium implants coated with mesoporous titania thin films with a pore size of 7.5 nm. In vitro drug delivery experiments demonstrated that the mesoporous coating provided a high drug loading capacity and controlled release. The subsequent in vivo study in rat tibia showed beneficial effects with respect to bone-implant anchorage and bone-formation along the surface of the implants when plerixafor and SDF-1a were delivered locally. The effect was most prominent by the finding that the combination of the drugs significantly improved the mechanical bone anchorage. These observations suggest that titanium implants with local delivery of drugs for enhanced local recruitment of progenitor cells have the ability to promote osseointegration. This approach may provide a potential strategy for the development of novel implant treatments.
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| 4. |
- Larsson Wexell, Cecilia, 1965, et al.
(author)
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Electropolished titanium implants with a mirror-like surface support osseointegration and bone remodelling
- 2016
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In: Advances in Materials Science and Engineering. - : Hindawi Limited. - 1687-8434 .- 1687-8442.
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Journal article (peer-reviewed)abstract
- This work characterises the ultrastructural composition of the interfacial tissue adjacent to electropolished, commercially pure titanium implants with and without subsequent anodisation, and it investigates whether a smooth electropolished surface can support bone formation in a manner similar to surfaces with a considerably thicker surface oxide layer. Screw-shaped implants were electropolished to remove all topographical remnants of the machining process, resulting in a thin spontaneously formed surface oxide layer and a smooth surface. Half of the implants were subsequently anodically oxidised to develop a thickened surface oxide layer and increased surface roughness. Despite substantial differences in the surface physicochemical properties, the microarchitecture and the composition of the newly formed bone were similar for both implant surfaces after 12 weeks of healing in rabbit tibia. A close spatial relationship was observed between osteocyte canaliculi and both implant surfaces. On the ultrastructural level, the merely electropolished surface showed the various stages of bone formation, for example, matrix deposition and mineralisation, entrapment of osteoblasts within the mineralised matrix, and their morphological transformation into osteocytes. The results demonstrate that titanium implants with a mirror-like surface and a thin, spontaneously formed oxide layer are able to support bone formation and remodelling.
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| 5. |
- Shah, Furqan A., et al.
(author)
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Ultrastructural evaluation of shrinkage artefacts induced by fixatives and embedding resins on osteocyte processes and pericellular space dimensions
- 2015
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In: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 103:4, s. 1565-76
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Journal article (peer-reviewed)abstract
- The integrity of the interface between the osteocyte (Ot) process and the canalicular wall was investigated in terms of change in the lateral dimensions of the Ot process in relation to the canalicular width, i.e., widening of the pericellular space. This has been interpreted as shrinkage of the Ot process relative to the canalicular wall during sample preparation stages of fixation, dehydration, and resin embedding. Sprague-Dawley rat tibial cross-sections were prepared for transmission electron microscopy (TEM). Four different fixative preparations: paraformaldehyde (PF), modified Karnovsky's (MK), glutaraldehyde (GRR) with ruthenium red (GRR), and zinc formalin (ZF); and two different embedding resins: LR Gold (LRG) and Epon812 (Epon) were evaluated. It was found that for LRG embedding, formalin-only fixatives (PF and ZF) induced lower shrinkage than GRR-containing fixatives (MK and GRR). In contrast, for Epon embedding, MK showed the highest shrinkage, while no differences were found between the remaining fixatives (PF, ZF, and GRR). All formalin-containing fixatives (MK, PF, and ZF) induced similar shrinkage in both embedding media. The most dramatic difference was for GRR fixation, which in combination with LRG embedding showed ∼62% more shrinkage than with Epon embedding, suggesting that the combination of GRR fixation and LRG embedding synergistically amplifies Ot shrinkage. These differences likely suggest a role of the resin in secondarily influencing the tissue structure following fixation. Further, the work confirms LRG as a poor embedding medium for bone specimens, as it causes large variations in shrinkage depending on fixation. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014.
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| 6. |
- Olsson, Rickard, 1959-, et al.
(author)
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Production of osseointegrating (bone bonding) surfaces on titanium screws by laser melt disruption
- 2018
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In: Journal of Laser Applications. - Melville, NY : Laser Institute of America. - 1042-346X .- 1938-1387. ; 30:4
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Journal article (peer-reviewed)abstract
- Several techniques can be used to modify implant surfaces in order to accelerate bone growth around titanium implants. One method is to generate a surface structure which stimulates bone growth and remodeling. This paper describes and explains a nonablative method for producing osseointegrating (structural and functional bone bonding) surfaces on titanium implants using laser processing. The focus is especially on surface texturing of dental implant screws, where the ability of a Nd:YAG laser to generate "splashy" surfaces covered in resolidified microscale droplets coated with nanoscale surface oxides is assessed. The surfaces produced were analyzed by a scanning electron microscope and energy dispersive x-ray spectroscopy. It is concluded that laser processing using Q-pulsed Nd:YAG lasers can generate surfaces which match the demands set by clinical experience. One important characteristic of the surfaces discussed here is that they involve overhanging features which are suitable for trapping red blood cells and which cannot be created by mechanical or chemical roughening techniques. © 2018 Laser Institute of America.
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| 7. |
- Lindahl, Carl, et al.
(author)
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Biomimetic calcium phosphate coating of additively manufactured porous CoCr implants
- 2015
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In: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 353, s. 40-47
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Journal article (peer-reviewed)abstract
- The aim of this work was to study the feasibility to use a biomimetic method to prepare biomimetic hydroxyapatite (HA) coatings on CoCr substrates with short soaking times and to characterize the properties of such coatings. A second objective was to investigate if the coatings could be applied to porous CoCr implants manufactured by electron beam melting (EBM). The coating was prepared by immersing the pretreated CoCr substrates and EBM implants into the phosphate-buffered solution with Ca2+ in sealed plastic bottles, kept at 60 degrees C for 3 days. The formed coating was partially crystalline, slightly calcium deficient and composed of plate-like crystallites forming roundish flowers in the size range of 300-500 nm. Cross-section imaging showed a thickness of 300-500 nm. In addition, dissolution tests in Tris-HCl up to 28 days showed that a substantial amount of the coating had dissolved, however, undergoing only minor morphological changes. A uniform coating was formed within the porous network of the additive manufactured implants having similar thickness and morphology as for the flat samples. In conclusion, the present coating procedure allows coatings to be formed on CoCr and could be used for complex shaped, porous implants made by additive manufacturing.
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| 8. |
- Calon, Tim, et al.
(author)
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Multimodal analysis of the tissue response to a bone-anchored hearing implant. : 11. Calon TGA, Johansson ML, Omar O, Shah FA, Budding D, Trobos M, Thomsen P, Stokroos RJ, Palmquist
- 2019
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In: 2nd Politzer Society Meeting/2nd World Congress of Otology, 28 May - 1 June, 2019, Warsaw, Poland..
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Conference paper (other academic/artistic)
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| 9. |
- Johansson, Martin L, et al.
(author)
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Clinical retrieval and analysis of percutaneous bone-anchored hearing implants using multiple analytical methodologies
- 2020
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In: 11TH WORLD BIOMATERIALS CONGRESS 11 - 15 December 2020.
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Conference paper (other academic/artistic)abstract
- Introduction: The percutaneous bone-anchored hearing system (BAHS) is an established form of hearing treatment for conductive or mixed hearing loss and single sided deafness [1]. The system consists of a titanium implant inserted in the temporal bone and mounted with an abutment onto which a sound processor is attached. It is considered to be a successful treatment with generally good outcomes in terms of audiology and quality of life [2]. However, associated adverse outcomes, such as peri-abutment inflammation and infection, pain and numbness may necessitate intervention, device removal or implant loss [2, 3]. The clinician must rely on subjective clinical measurements, whereas information on the biological events at the tissue-BAHS interface remain inaccessible. Reports of analyses of planned, electively retrieved BAHS implants, performed under perfectly controlled circumstances, are rare [4, 5]. The aim with this study was to gain insight into the biological processes around percutaneous bone-conducting devices by analysing retrieved implants. Experimental methods: Through the establishment of a bilateral collaboration network with European clinics, a retrieval and analytical protocol have been implemented. This will allow correlation of the clinical data with the underpinning microbiological, molecular and morphological fingerprints at the tissue interface. Multiple analytical and correlative strategies have been used, enabling multiscale and multimodal investigation of the tissue interface. Different sampling procedures and analytical tools were employed, including X-ray micro-computed tomography (micro-CT), histology/histomorphometry, fluorescence in situ hybridization (FISH), microbiology, quantitative polymerase chain reaction (qPCR), backscattered electron scanning electron microscopy (BSE-SEM) and Raman spectroscopy. Results and discussions: So far, retrieval, preservation and investigation of six BAHS implants with surrounding tissue have been performed. Causes for removal (1-7 years after implantation) were chronic pain, recurrent inflammation, cancer and mechanical complications. After micro-CT analysis and the samples were embedded for histological and ultrastructural analyses. This presentation describes the sample preparation route allowing assessment of the different hierarchical levels of interest of the tissue interface. Examples of the results from the different analyses will be presented, with emphasis on correlating the clinical outcome with the analytical findings. Conclusions: The implementation of a retrieval protocol combined with a subsequent multi-scale analytical strategy enables a correlation between the clinical history of patients and the underpinning microbiological, molecular and morphological events in the tissues interfacing the electively removed or failed percutaneous bone-anchored hearing implants.
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