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Pujari-Palmer, M., Robo, C., Persson, C., Procter, P. & Engqvist, H. (2018). Influence of cement compressive strength and porosity on augmentation performance in a model of orthopedic screw pull-out. Journal of The Mechanical Behavior of Biomedical Materials, 77, 624-633.
Open this publication in new window or tab >>Influence of cement compressive strength and porosity on augmentation performance in a model of orthopedic screw pull-out
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2018 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 77, 624-633 p.Article in journal (Refereed) Published
Abstract [en]

Disease and injuries that affect the skeletal system may require surgical intervention and internal fixation, i.e. orthopedic plate and screw insertion, to stabilize the injury and facilitate tissue repair. If the surrounding bone quality is poor the screws may migrate, or the bone may fail, resulting in screw pull-out. Though numerous studies have shown that cement augmentation of the interface between bone and implant can increase screw holding strength in bone, the physical properties of cement that influence pull-out force have not been investigated. The present study sought to determine how the physical properties of calcium phosphate cements (CPCs), and the strength of the biological or synthetic material surrounding the augmented screw, affected the corresponding orthopedic screw pull-out force in urethane foam models of healthy and osteoporotic bone (Sawbones). In the simplest model, where only the bond strength between screw thread and cement (without Sawbone) was tested, the correlation between pull-out force and cement compressive strength (R2 = 0.79) was weaker than correlation with total cement porosity (R2 = 0.89). In open pore Sawbone that mimics “healthy” cancellous bone density the stronger cements produced higher pull-out force (50-60% increase). Higher strength, lower porosity, cements also produced higher pull-out forces (50-190% increase) in Sawbones with cortical fixation if the failure strength of the cortical material was similar to (bovine tibial bone), or greater than (metal shell), actual cortical bone. This result is of particular clinical relevance where fixation with a metal plate implant is indicated, as the nearby metal can simulate a thicker cortical shell and, thereby, increase the pull-out force of screws augmented with stronger cements. The improvement in pull-out force was apparent even at low augmentation volumes of 0.5 ml (50% increase), which suggest that in clinical situations where augmentation volume is limited the stronger, lower porosity CPCs may still produce a significant improvement in screw holding strength. When correlations of all the tested models were compared both cement porosity and compressive strength accurately predicted pull-out force (R2=1.00, R2=0.808), though prediction accuracy depended upon the strength of the material surrounding the Sawbone. The correlations strength was low for bone with no, or weak, cortical fixation. Higher strength and lower porosity CPCs also produced greater pull-out force (1-1.5 kN) than commercial CPC (0.2-0.5kN), but lower pull-out force than PMMA (2-3 kN). The results of this study suggest that the likelihood of screw fixation failure may be reduced by selecting calcium phosphate cements with lower porosity and higher bulk strength, in patients with healthy bone mineral density and/or sufficient cortical thickness. This is of particular clinical relevance when fixation with metal plates is indicated, or where the augmentation volume is limited.

Keyword
Screw pull-out, Orthopedic screw augmentation, Calcium phosphate cement, Bioceramic, Bone biomechanics, Sawbones, Cortical fixation
National Category
Medical Materials Ceramics Applied Mechanics Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-320157 (URN)10.1016/j.jmbbm.2017.10.016 (DOI)
Funder
Swedish Research Council, 621–2011-3399EU, FP7, Seventh Framework Programme, 262948
Available from: 2017-04-16 Created: 2017-04-16 Last updated: 2018-01-04Bibliographically approved
Garbani, M., Xia, W., Rhyner, C., Prati, M., Scheynius, A., Malissen, B., . . . Terhorst-Molawi, D. (2017). Allergen-loaded strontium-doped hydroxyapatite spheres improve allergen-specific immunotherapy in mice. Allergy. European Journal of Allergy and Clinical Immunology, 72(4), 570-578.
Open this publication in new window or tab >>Allergen-loaded strontium-doped hydroxyapatite spheres improve allergen-specific immunotherapy in mice
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2017 (English)In: Allergy. European Journal of Allergy and Clinical Immunology, ISSN 0105-4538, E-ISSN 1398-9995, Vol. 72, no 4, 570-578 p.Article in journal (Refereed) Published
Abstract [en]

Background

Immunomodulatory interventions play a key role in the treatment of infections and cancer as well as allergic diseases. Adjuvants such as micro- and nanoparticles are often added to immunomodulatory therapies to enhance the triggered immune response. Here, we report the immunological assessment of novel and economically manufactured microparticle adjuvants, namely strontium-doped hydroxyapatite porous spheres (SHAS), which we suggest for the use as adjuvant and carrier in allergen-specific immunotherapy (ASIT).

Methods and Results

Scanning electron microscopy revealed that the synthesis procedure developed for the production of SHAS results in a highly homogeneous population of spheres. SHAS bound and released proteins such as ovalbumin (OVA) or the major cat allergen Fel d 1. SHAS-OVA were taken up by human monocyte-derived dendritic cells (mdDCs) and murine DCs and did not have any necrotic or apoptotic effects even at high densities. In a murine model of ASIT for allergic asthmatic inflammation we found that OVA released from subcutaneously injected SHAS-OVA led to a sustained stimulation of both CD4+ and CD8+ T-cells. ASIT with SHAS-OVA as compared to soluble OVA resulted in similar humoral responses but in a higher efficacy as assessed by symptom scoring.

Conclusion

We conclude that SHAS may constitute a suitable carrier and adjuvant for ASIT with great potential due to its unique protein-binding properties.

National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-310479 (URN)10.1111/all.13041 (DOI)000397489400007 ()27590538 (PubMedID)
Funder
Swedish Research Council, 2013-5419
Available from: 2016-12-16 Created: 2016-12-16 Last updated: 2017-05-15Bibliographically approved
Ting, M., Jefferies, S. R., Xia, W., Engqvist, H. & Suzuki, J. B. (2017). Classification and Effects of Implant Surface Modification on the Bone: Human Cell-Based In Vitro Studies. Journal of Oral Implantology, 43(1), 58-83.
Open this publication in new window or tab >>Classification and Effects of Implant Surface Modification on the Bone: Human Cell-Based In Vitro Studies
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2017 (English)In: Journal of Oral Implantology, ISSN 0160-6972, E-ISSN 1548-1336, Vol. 43, no 1, 58-83 p.Article, review/survey (Refereed) Published
Abstract [en]

Implant surfaces are continuously being improved to achieve faster osseointegration and a stronger bone to implant interface. This review will present the various implant surfaces, the parameters for implant surface characterization, and the corresponding in vitro human cell-based studies determining the strength and quality of the bone-implant contact. These in vitro cell-based studies are the basis for animal and clinical studies and are the prelude to further reviews on how these surfaces would perform when subjected to the oral environment and functional loading.

Place, publisher, year, edition, pages
ALLEN PRESS INC, 2017
Keyword
titanium, dental implant, implant surface morphology, osseointegration, surface topography
National Category
Medical and Health Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-320997 (URN)10.1563/aaid-joi-D-16-00079 (DOI)000395366200011 ()27897464 (PubMedID)
Available from: 2017-04-28 Created: 2017-04-28 Last updated: 2017-04-28Bibliographically approved
Li, H., Edin, F., Hayashi, H., Gudjonsson, O., Danckwardt-Lillieström, N., Engqvist, H., . . . Xia, W. (2017). Guided Growth of Auditory Neurons: Bioactive Particles Towards Gapless Neural - Electrode Interface. Biomaterials, 122, 1-9.
Open this publication in new window or tab >>Guided Growth of Auditory Neurons: Bioactive Particles Towards Gapless Neural - Electrode Interface
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2017 (English)In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 122, 1-9 p.Article in journal (Refereed) Published
Abstract [en]

Cochlear implant (CI) is a successful device to restore hearing. Despite continuous development, frequency discrimination is poor in CI users due to an anatomical gap between the auditory neurons and CI electrode causing current spread and unspecific neural stimulation. One strategy to close this anatomical gap is guiding the growth of neuron dendrites closer to CI electrodes through targeted slow release of neurotrophins. Biodegradable calcium phosphate hollow nanospheres (CPHSs) were produced and their capacity for uptake and release of neurotrophins investigated using I-125-conjugated glia cell line-derived neurotrophic factor (GDNF). The CPHSs were coated onto CI electrodes and loaded with neurotrophins. Axon guidance effect of slow-released neurotrophins from the CPHSs was studied in an in vitro 3D culture model. CPHS coating bound and released GDNF with an association rate constant 6.3 x 10(3) M(-1)s(-1) and dissociation rate 2.6 x 10(-5) s(-1), respectively. Neurites from human vestibulocochlear ganglion explants found and established physical contact with the GDNF-loaded CPHS coating on the CI electrodes placed 0.7 mm away. Our results suggest that neurotrophin delivery through CPHS coating is a plausible way to close the anatomical gap between auditory neurons and electrodes. By overcoming this gap, selective neural activation and the fine hearing for CI users become possible.

National Category
Medical and Health Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-276334 (URN)10.1016/j.biomaterials.2016.12.020 (DOI)000394472500001 ()28107660 (PubMedID)
Funder
Swedish Research Council, 2013-5419
Available from: 2016-03-07 Created: 2016-02-11 Last updated: 2017-04-28Bibliographically approved
Skjöldebrand, C., Schmidt, S., Vuong, V., Pettersson, M., Grandfield, K., Hogberg, H., . . . Persson, C. (2017). Influence of Substrate Heating and Nitrogen Flow on the Composition, Morphological and Mechanical Properties of SiNx Coatings Aimed for Joint Replacements. Materials, 10(2).
Open this publication in new window or tab >>Influence of Substrate Heating and Nitrogen Flow on the Composition, Morphological and Mechanical Properties of SiNx Coatings Aimed for Joint Replacements
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2017 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 10, no 2Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
MDPI AG, 2017
Keyword
silicon nitride, coating, hip joint replacement, X-ray photoelectron spectroscopy (XPS), nanoindentation, hardness, Young's modulus, transmission electron microscopy (TEM)
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-320778 (URN)10.3390/ma10020173 (DOI)000395445800080 ()
Funder
EU, FP7, Seventh Framework Programme, GA-310477Carl Tryggers foundation , CTS 14:431
Available from: 2017-04-25 Created: 2017-04-25 Last updated: 2017-11-29Bibliographically approved
Qin, T., Han, Y., Zhang, P., Wani, I. H., Nikolajeff, F., Leifer, K. & Engqvist, H. (2017). Template-free synthesis of phosphate-based spheres via modified supersaturated phosphate buffer solutions. Journal of materials science. Materials in medicine, 28(7), Article ID 99.
Open this publication in new window or tab >>Template-free synthesis of phosphate-based spheres via modified supersaturated phosphate buffer solutions
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2017 (English)In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 28, no 7, 99Article in journal (Refereed) Published
Abstract [en]

Modified supersaturated phosphate buffer solutions were used to synthesize phosphate-based spheres, including calcium phosphate (CaP), strontium phosphate (SrP) and barium phosphate (BaP). A series of ions concentrations in the modified phosphate buffer solutions were investigated in order to study their effects in precipitates morphologies. During synthesis, it was found that magnesium was the key factor in sphere formation. The morphologies of calcium phosphate, strontium phosphate and barium phosphate precipitates varied as the concentration of magnesium ions varied. When sufficient magnesium was provided, the precipitates appeared spherical, and the diameter was in range of 0.5-2 mu m. The morphologies, compositions and structure of spheres were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N-2 adsorption analysis. Moreover, the application of magnesium substituted calcium phosphate spheres in dentin tubules occlusion was investigated.

Place, publisher, year, edition, pages
SPRINGER, 2017
National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-329001 (URN)10.1007/s10856-017-5911-x (DOI)000403777800001 ()28534282 (PubMedID)
Available from: 2017-09-06 Created: 2017-09-06 Last updated: 2017-09-06Bibliographically approved
Qin, T., Han, Y., Zhang, P. & Engqvist, H. (2017). The formation of calcium fluoride microspheres via solubility equilibrium. Ceramics International, 43(16), 14521-14524.
Open this publication in new window or tab >>The formation of calcium fluoride microspheres via solubility equilibrium
2017 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 43, no 16, 14521-14524 p.Article in journal (Refereed) Published
Abstract [en]

The focus of this study is on synthesis and mechanism of calcium fluoride (CaF2) spheres. Magnesium is the decisive factor in the formation of the spheres. The solubility product constant of Mg1-xCaxF2 is higher than those of CaF2 and MgF2. The structure of particles evolved to being spherical due to solubility equilibrium. The calcium fluoride spheres have great potential as dental materials in bleaching products.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2017
Keyword
Calcium fluoride, Sphere, Solubility equilibrium, Magnesium
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-336428 (URN)10.1016/j.ceramint.2017.07.148 (DOI)000411299300198 ()
Available from: 2017-12-18 Created: 2017-12-18 Last updated: 2017-12-18Bibliographically approved
Xia, W., Qin, T., Suska, F. & Engqvist, H. (2016). Bioactive spheres: the way of treating dentin hypersensitivity. ACS biomaterials science and engineering, 2(5), 734-740.
Open this publication in new window or tab >>Bioactive spheres: the way of treating dentin hypersensitivity
2016 (English)In: ACS biomaterials science and engineering, ISSN 2373-9878, Vol. 2, no 5, 734-740 p.Article in journal (Refereed) Published
Abstract [en]

Sealing exposed dental tubules is the most effective and long-term way to relieve the pain induced by dental sensitivity. A bioactive hollow sphere (strontium substituted calcium phosphate) was synthesized and added in toothpaste to study its effect on dental hypersensitivity via tooth tubules occlusion and mineralization. The size of spheres is perfect for penetrating into dental tubules, reaching to 20 pm into the tubules. The exposed dental tubules were occluded by spheres and new apatite layer after 3 days brushing. The spheres attached to the surface of dentin and the mineralized surface contained two layers, a porous layer followed by a dense apatite layer. The porous layer can be dissolved in an acidic solution, but the following dense layer could be kept even after soaking in an acid solution. In conclusion, Sr-substituted calcium phosphate spheres could be a good candidate for at-home treatment of dental hypersensitivity.

Keyword
calcium phosphate, spheres, occlusion, mineralization, dental sensitivity
National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-284233 (URN)10.1021/acsbiomaterials.5b00499 (DOI)000375893600004 ()
Funder
Swedish Research Council, 2013-5419
Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2017-01-19Bibliographically approved
Vallhov, H., Xia, W., Engqvist, H. & Scheynius, A. (2016). Bioceramic microneedles in allergen-specific immunotherapy. In: : . Paper presented at 11th World Immune Regulation Meeting. .
Open this publication in new window or tab >>Bioceramic microneedles in allergen-specific immunotherapy
2016 (English)Conference paper, Oral presentation only (Refereed)
National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-284210 (URN)
External cooperation:
Conference
11th World Immune Regulation Meeting
Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2017-01-19
Xia, W., Chang, J. & Engqvist, H. (2016). Biological Effect of Ions in CalciumPhosphates on Bone Regeneration. In: Design of Bioactive Materials for Bone Repair and Regeneration: . World Scientific.
Open this publication in new window or tab >>Biological Effect of Ions in CalciumPhosphates on Bone Regeneration
2016 (English)In: Design of Bioactive Materials for Bone Repair and Regeneration, World Scientific, 2016Chapter in book (Refereed)
Place, publisher, year, edition, pages
World Scientific, 2016
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-284117 (URN)978-981-4667-65-4 (ISBN)
External cooperation:
Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2017-01-19
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/hakan.engqvist@angstrom.uu.se

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