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Sökning: hsv:(TEKNIK OCH TEKNOLOGIER) hsv:(Medicinteknik) > Engqvist Håkan

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1.
  • Engstrand, Johanna, et al. (författare)
  • Influence of polymer addition on the mechanical properties of a premixed calcium phosphate cement
  • 2013
  • Ingår i: Biomatter. - : Informa UK Limited. - 2159-2535. ; 3:4, s. e27249-
  • Tidskriftsartikel (refereegranskat)abstract
    • Premixed calcium phosphate cements can reduce handling complications that are associated with the mixing of cements in the operating room. However, to extend the clinical indication of ceramic cements their mechanical properties need to be further improved. The incorporation of a polymeric material with intrinsically high tensile properties could possibly assist in increasing the mechanical properties of calcium phosphate cement. In this study polymer microparticles made from poly(lactid-co-glycolide) plasticised with poly(ethylene glycol) 400 (PLGA/PEG microparticles) were added in amounts of up to 5 wt% to a premixed acidic calcium phosphate cement. The PLGA/PEG microparticles added undergo a shape transformation at 37°C, which could give a better integration between polymer microparticles and ceramic cement compared to polymer microparticles lacking this property. The results showed that the incorporation of 1.25 wt% PLGA/PEG microparticles increased the compressive strength by approximately 20% up to 15.1 MPa while the diametral tensile strength was kept constant. The incorporation of PLGA/PEG microparticles increased the brushite to monetite ratio after setting compared to pure ceramic cements. In conclusion, small amounts of PLGA/PEG microparticles can be incorporated into premixed acidic calcium phosphate cement and increase their mechanical properties, which could lead to increased future applications.
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2.
  • Lewin, Susanne, et al. (författare)
  • Monetite-based composite cranial implants demonstrate long-term clinical volumetric balance by concomitant bone formation and degradation
  • 2021
  • Ingår i: Acta Biomaterialia. - : Elsevier. - 1742-7061 .- 1878-7568. ; 128, s. 502-513
  • Tidskriftsartikel (refereegranskat)abstract
    • The use of calcium phosphates (CaPs) as synthetic bone substitutes should ideally result in a volumetric balance with concomitant bone formation and degradation. Clinical data on such properties is nevertheless lacking, especially for monetite-based CaPs. However, a monetite-based composite implant has recently shown promising cranial reconstructions, with both CaP degradation and bone formation. In this study, the volumetric change at the implant site was quantified longitudinally by clinical computed tomography (CT). The retrospective CT datasets had been acquired postoperatively ( n = 10), in 1-year ( n = 9) and 3-year ( n = 5) follow-ups. In the 1-year follow-up, the total volumetric change at the implant site was-8 +/- 8%. A volumetric increase (bone formation) was found in the implant-bone interface, and a volumetric decrease was observed in the central region (CaP degradation). In the subjects with 2-or 3-year follow-ups, the rate of volumetric decrease slowed down or plateaued. The reported degradation rate is lower than previous clinical studies on monetite, likely due to the presence of pyrophosphate in the monetite-based CaP-formulation. A 31-months retrieval specimen analysis demonstrated that parts of the CaP had been remodeled into bone. The CaP phase composition remained stable, with 6% transformation into hydroxyapatite. In conclusion, this study demonstrates successful bone-bonding between the CaP-material and the recipient bone, as well as a long-term volumetric balance in cranial defects repaired with the monetitebased composite implant, which motivates further clinical use. The developed methods could be used in future studies for correlating spatiotemporal information regarding bone regeneration and CaP degradation to e.g. patient demographics. Statement of significance In bone defect reconstructions, the use of calcium phosphate (CaP) bioceramics ideally results in a volumetric balance between bone formation and CaP degradation. Clinical data on the volumetric balance is nevertheless lacking, especially for monetite-based CaPs. Here, this concept is investigated for a composite cranial implant. The implant volumes were quantified from clinical CT-data: postoperatively, one year and three years postoperatively. In total,-8 +/- 8% ( n = 9) volumetric change was observed after one year. But the change plateaued, with only 2% additional decrease at the 3-year follow-up ( n = 5), indicating a lower CaP degradation rate. Osseointegration was seen at the bone-implant interface, with a 9 +/- 7% volumetric change after one year. This study presented the first quantitative spatiotemporal CT analysis of monetite-based CaPs.
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3.
  • Sladkova, Martina, et al. (författare)
  • Engineering human bone grafts with new macroporous calcium phosphate cement scaffolds
  • 2018
  • Ingår i: Journal of Tissue Engineering and Regenerative Medicine. - : Hindawi Limited. - 1932-6254 .- 1932-7005. ; 12:3, s. 715-726
  • Tidskriftsartikel (refereegranskat)abstract
    • Bone engineering opens the possibility to grow large amounts of tissue products by combining patient-specific cells with compliant biomaterials. Decellularized tissue matrices represent suitable biomaterials, but availability, long processing time, excessive cost, and concerns on pathogen transmission have led to the development of biomimetic synthetic alternatives. We recently fabricated calcium phosphate cement (CPC) scaffolds with variable macroporosity using a facile synthesis method with minimal manufacturing steps and demonstrated long-term biocompatibility in vitro. However, there is no knowledge on the potential use of these scaffolds for bone engineering and whether the porosity of the scaffolds affects osteogenic differentiation and tissue formation in vitro. In this study, we explored the bone engineering potential of CPC scaffolds with two different macroporosities using human mesenchymal progenitors derived from induced pluripotent stem cells (iPSC-MP) or isolated from bone marrow (BMSC). Biomimetic decellularized bone scaffolds were used as reference material in all experiments. The results demonstrate that, irrespective of their macroporosity, the CPC scaffolds tested in this study support attachment, viability, and growth of iPSC-MP and BMSC cells similarly to decellularized bone. Importantly, the tested materials sustained differentiation of the cells as evidenced by increased expression of osteogenic markers and formation of a mineralized tissue. In conclusion, the results of this study suggest that the CPC scaffolds fabricated using our method are suitable to engineer bone grafts from different cell sources and could lead to the development of safe and more affordable tissue grafts for reconstructive dentistry and orthopaedics and in vitro models for basic and applied research.
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4.
  • Berg, Camilla, et al. (författare)
  • ACP-Mg particles for treatment of dental hypersensitivity : a mode of action study
  • 2019
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Introduction/purpose:Dental hypersensitivity is a common clinical condition usually associated with exposed dentinal tubules. Occlusion of those, hindering fluid movement as a response to external stimuli, is one approach to reduce pain.[1] The occluding agent should induce mineralization and have a good filling effect. In this study, particles (200-400 nm) of Amorphous Calcium Phosphate with Mg (ACP-Mg) were used aiming to evaluate the mode of action with in-vitro studies on dentine as well as degradation properties in buffered systems.Methods:Degradation properties and ion-release was monitored by dispersing the particles in Tris-HCl (10 mg/mL) storing the dispersions at 37 °C.  In-vitro testing was performed on 1 mm thick dentine discs cut from extracted human molars. Specimens were etched in 35 % phosphoric acid, rinsed with DI-water followed by treatment by applying a gel formulation containing the particles using a soft bristled toothbrush, brushing 1 min on each side and leaving the specimen to rest for 3 min. Treatment was repeated four times during one day and samples were incubated at 37 °C in artificial saliva.Results:In vitro tests and degradation studies showed that ACP-Mg particles induced formation of Hydroxyapatite (HA). ICP-OES, XRD and SEM showed that there was a rapid release of all ions up to 6 hours followed by a re-precipitation of HA at 24 hours with a lower Mg-content. The crystallinity increased with time as the concentration of all ions decreased in the solutions. Morphological evaluation for the in-vitro tests showed that HA-like structures formed already after 24 hours on the dentine surface.  Cross-sections revealed that the particles reached as far as 80 µm from the surface and tubules, fully occluded by HA-like structures, was visible at comparable depths after 7 days.Conclusions:ACP-Mg particles can be used to reduce dentine hypersensitivity by effective occlusion of dentine tubules via rapid formation of surface and intra-tubular HA.References:1. Splieth CH, Tachou A. 2013. Epidemiology of dentin hypersensitivity. Clin Oral Investig. 17:3–8. 
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9.
  • Berg, Camilla, et al. (författare)
  • Synthesis of Ion Substituted Ceramic Core-Shell Particles for Dental Applications
  • 2018
  • Konferensbidrag (refereegranskat)abstract
    • Calcium phosphate spheres are interesting alternatives for dental applications due to their chemical similarity to teeth and biocompatibility. A spherical shape with a hollow cores allows for loading of therapeutic agents for drug delivery which potentially could be combined with other applications such as tooth remineralization and treatment of hypersensitivity.Precipitation reactions are one of the techniques used for synthesizing spherical particles, but little is known about the mechanism behind the sphere formation, which makes tuning of the material properties challenging. Previously, it has been shown that substituting ions can influence the crystallization process, which can enable greater control during the synthesis.In this study, several different substituting ions has been used in the synthesis of alkaline earth phosphates, to further investigate their role in sphere formation and to develop a robust synthesis technique.Particles of alkaline earth phosphates (Ca, Sr and Ba) were synthesized with a precipitation reaction. Solutions with constituent anions and cations were mixed at room temperature, and substituting ions (Mg, Ca or Sr) were added before heating at 60-100 °C. Reaction times varied between 10 minutes to 24 hours. Characterization of precipitates was performed with SEM, DLS and FIB to analyze morphology, size and cross-sections of the spheres. Crystal structure and atomic composition was analyzed with XRD and ICP-OES.Without substituting ions, precipitates had no specific shape and crystallized in an apatitic structure or as a hydrogenated phosphate. Substituting ions stabilized the initial amorphous phase during the reaction, hindering rapid crystal growth which allowed for self-assembly into hollow, spherical particles with a diameter between 300-700 nm. The phase composition and degree of ion substitution in the precipitates depended on the size and concentration of the substituting ions. The amount of substitution was determined in the range between 5-30 %, where precipitates with a low degree of substitution crystallized in a structure similar to β-tricalcium phosphate, whereas materials with a higher degree of substitution had an amorphous structure.In this study it was shown that it was possible to obtain hollow, spherical particles of calcium-, strontium- and barium phosphate, by using substituting ions during a precipitation reaction. This indicates that the approach can be used to tailor the properties of spherical particles intended for dental applications.
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10.
  • Brohede, Ulrika, et al. (författare)
  • Multifunctional implant coatings providing possibilities for fast antibiotics loading with subsequent slow release
  • 2009
  • Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 20:9, s. 1859-1867
  • Tidskriftsartikel (refereegranskat)abstract
    • The possibility to fast-load biomimetic hydroxyapatite coatings on surgical implant with the antibiotics Amoxicillin, Gentamicin sulfate, Tobramycin and Cephalothin has been investigated in order to develop a multifunctional implant device offering sustained local anti-bacterial treatment and giving the surgeon the possibility to choose which antibiotics to incorporate in the implant at the site of surgery. Physical vapor deposition was used to coat titanium surfaces with an adhesion enhancing gradient layer of titanium oxide having an amorphous oxygen poor composition at the interface and a crystalline bioactive anatase TiO2 composition at the surface. Hydroxyapatite (HA) was biomimetically grown on the bioactive TiO2 to serve as a combined bone in-growth promoter and drug delivery vehicle. The coating was characterized using scanning and transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The antibiotics were loaded into the HA coatings via soaking and the subsequent release and antibacterial effect were analyzed using UV spectroscopy and examination of inhibition zones in a Staphylococcus aureus containing agar. It was found that a short drug loading time of 15 min ensured antibacterial effects after 24 h for all antibiotics under study. It was further found that the release processes of Cephalothin and Amoxicillin consisted of an initial rapid drug release that varied unpredictably in amount followed by a reproducible and sustained release process with a release rate independent of the drug loading times under study. Thus, implants that have been fast-loaded with drugs could be stored for ~10 min in a simulated body fluid after loading to ensure reproducibility in the subsequent release process. Calculated release rates and measurements of drug amounts remaining in the samples after 22 h of release indicated that a therapeutically relevant dose could be achieved close to the implant surface for about 2 days. Concluding, the present study provides an outline for the development of a fast-loading slow-release surgical implant kit where the implant and the drug are separated when delivered to the surgeon, thus constituting a flexible solution for the surgeon by offering the choice of quick addition of antibiotics to the implant coating based on the patient need.
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