| 1. |
- Arvidsson, Anna, 1973, et al.
(författare)
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Nucleation and growth of calcium phosphates in the presence of fibrinogen on titanium implants with four potentially bioactive surface preparations. An in vitro study.
- 2009
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Ingår i: Journal of Materials Science: Materials in Medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 20:9, s. 1869-1879
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Tidskriftsartikel (refereegranskat)abstract
- Abstract The aim of this study was to compare the nucleating and crystal growth behaviour of calcium phosphates on four types of potentially bioactive surfaces, using the simulated body fluid (SBF) model with added fibrinogen. Blasted titanium discs were modified by alkali and heat treatment, anodic oxidation, fluoride treatment, or hydroxyapatite coating. The discs were immersed in SBF with fibrinogen for periods of 3 days and 1, 2, 3 and 4 weeks. The topography, morphology, and chemistry of the surfaces were evaluated with optical interferometry, scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX), and x-ray photoelectron spectroscopy (XPS), respectively. All surface modifications showed early calcium phosphate formation after 3 days, and were almost completely covered by calcium phosphates after 2 weeks. After 4 weeks, the Ca/P ratio was approximately 2.0 for all surface groups except the fluoride modified surface, which had a Ca/P ratio of 1.0–1.5. XPS measurements of the nitrogen concentration, which can be interpreted as an indirect measure of the protein content, reached a peak value after 3 days immersion and decreased thereafter. In conclusion, the results in the present study, when compared to earlier SBF studies without proteins, showed that fibrinogen stimulates calcium phosphates formation. Furthermore, no pronounced differences could be detected between blasted controls and the potentially bioactive specimens.
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| 2. |
- Barkarmo, Sargon, et al.
(författare)
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Enhanced bone healing around nanohydroxyapatite-coated polyetheretherketone implants : An experimental study in rabbit bone
- 2014
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Ingår i: Journal of biomaterials applications. - : Sage Publications. - 0885-3282 .- 1530-8022. ; 29:5, s. 737-747
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To investigate the bone response to threaded polyetheretherketone (PEEK) implants coated with nanohydroxyapatite. Materials and methods: A total of 39 PEEK implants were coated with nanocrystalline hydroxyapatite and 39 uncoated implants were used as controls. The implant surface was characterized by optical interferometry and scanning electron microscope. The implants were inserted in the tibia and femur of 13 rabbits. After 6 weeks of healing, quantitative and qualitative analyses were performed. Results: The test implants showed significantly higher removal torque test values compared with the control group. Histomorphometric evaluation demonstrated higher bone-to-implant contact for the test implants; however, there were no differences in bone area between the groups. Qualitative histological analyses demonstrated inflammatory cellular reactions in close vicinity of both implant surfaces. A two-cell layer of foreign body giant cells was observed irrespective of sample type. Conclusion: Our findings demonstrate that implants with a threaded design render good stability to PEEK in both coated and uncoated implants. Nanohydroxyapatite-coated PEEK implants demonstrated improved bone formation compared with uncoated controls.
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| 3. |
- Bougas, Kostas, 1980, et al.
(författare)
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In vitro Evaluation of Calcium Phosphate Precipitation on Possibly Bioactive Titanium Surfaces in the Presence of Laminin.
- 2011
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Ingår i: Journal of Oral & Maxillofacial Research. - : Stilus Optimus. - 2029-283X. ; 2:3, s. e3-
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The aim of the present study was to evaluate calcium phosphate precipitation and the amount of precipitated protein on three potentially bioactive surfaces when adding laminin in simulated body fluid.Material and Methods: Blasted titanium discs were prepared by three different techniques claimed to provide bioactivity: alkali and heat treatment (AH), anodic oxidation (AO) or hydroxyapatite coating (HA). A blasted surface incubated in laminin-containing simulated body fuid served as a positive control (B) while a blasted surface incubated in non laminin-containing simulated body fuid served as a negative control (B-). The immersion time was 1 hour, 24 hours, 72 hours and 1 week. Surface topography was investigated by interferometry and morphology by Scanning Electron Microscopy (SEM). Analysis of the precipitated calcium and phosphorous was performed by Energy Dispersive X-ray Spectroscopy (EDX) and the adsorbed laminin was quantified by iodine (125I) labeling.Results: SEM demonstrated that all specimens except for the negative control were totally covered with calcium phosphate (CaP) after 1 week. EDX revealed that B- demonstrated lower sum of Ca and P levels compared to the other groups after 1 week. Iodine labeling demonstrated that laminin precipitated in a similar manner on the possibly bioactive surfaces as on the positive control surface.Conclusions: Our results indicate that laminin precipitates equally on all tested titanium surfaces and may function as a nucleation center thus locally elevating the calcium concentration. Nevertheless further studies are required to clarify the role of laminin in the interaction of biomaterials with the host bone tissue.
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| 4. |
- Bougas, Kostas, 1980, et al.
(författare)
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Laminin Coating Promotes Calcium Phosphate Precipitation on Titanium Discs in vitro.
- 2011
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Ingår i: Journal of Oral & Maxillofacial Research. - : Stilus Optimus. - 2029-283X. ; 2:4, s. e5-
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The objective of this study was to investigate the effect of a laminin coating on calcium phosphate precipitation on three potentially bioactive titanium surfaces in simulated body fluid.Material and Methods: Blasted titanium discs were prepared by alkali and heat treatment (AH), anodic oxidation (AO) or hydroxyapatite coating (HA) and subsequently coated with laminin. A laminin coated blasted surface (B) served as a positive control while a blasted non coated (B-) served as a negative control. Surface morphology was examined by Scanning Electron Microscopy (SEM). The analysis of the precipitated calcium and phosphorous was performed by Energy Dispersive X-ray Spectroscopy (EDX).Results: The thickness of the laminin coating was estimated at 26 Å by ellipsometry. Interferometry revealed that the coating process did not affect any of the tested topographical parameters on µm level when comparing B to B-. After 2 weeks of incubation in SBF, the alkali-heat treated discs displayed the highest calcium phosphate deposition and the B group showed higher levels of calcium phosphate than the B- group.Conclusions: Our results suggest that laminin may have the potential to be used as a coating agent in order to enhance the osseoinductive performance of biomaterial surfaces, with the protein molecules possibly functioning as nucleation centres for apatite formation. Nevertheless, in vivo studies are required in order to clarify the longevity of the coating and its performance in the complex biological environment.
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| 5. |
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| 6. |
- Currie, Fredrik, 1975
(författare)
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Organic reactions in self-organized surfactant systems
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this work has been to investigate how microemulsions and micellar systems can be used as reaction media to overcome reactant incompatibility, enhance reaction rates and especially to control product composition, i.e., introducing regioselectivity, in organic synthesis. It was found that a significant increase in reaction rate can be obtained in properly formulated self-assembled systems as compared to the rates obtained in non-surfactant systems. The reaction rate differed between different surfactant classes and in many of the reactions studied cationic surfactant systems performed better than nonionic surfactant systems. It was found that there can be a considerable difference in reaction rate also between self-assembled systems based on surfactants of the same class. Investigation of the rates of a substitution reaction in microemulsions based on either a fatty alcohol ethoxylate or a sugar-based amphiphile, both of which are nonionic surfactants, showed that the reaction went much faster in the system based on the ethoxylated surfactant. This was attributed to a lower dielectric constant of the surfactant headgroup layer of the fatty alcohol ethoxylate than of the sugar-based surfactant, which should result in higher reactivity of the attacking anionic nucleophile. An alternative explanation to the higher reactivity of the system based on the ethoxylated surfactant is that this microemulsion has a higher dynamics, i.e., faster rate of disintegration and reformation of the oil-water interface. A substitution reaction between an alkyl phenol and a water soluble electrophile was studied in microemulsions and in micellar systems based on either a nonionic or a cationic surfactant. It was found that the reaction went faster in the self-assembled systems based on cationic surfactant than in those based on nonionic surfactant and that the micellar systems gave higher reaction rates than the microemulsions. The high reactivity in the systems based on the cationic surfactant was attributed to formation of a π-cation complex between the benzene ring of the alkyl phenol and the surfactant headgroup. It was showed that the oil-water interface of microemulsions could be used as template to induce regioselectivity both of electrophilic aromatic substitutions and of nucleophilic aliphatic substitution reactions. Monosubstitution of a symmetrical bifunctional reactant constituted a particularly striking example of how a microemulsion can be used as a tool to control regioselectivity.
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| 7. |
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| 8. |
- Franke Stenport, Victoria, 1970, et al.
(författare)
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Precipitation of calcium phosphate in the presence of albumin on titanium implants with four different possibly bioactive surface preparations. An in vitro study
- 2008
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Ingår i: Journal of Materials Science: Materials in Medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 19:12, s. 3497-3505
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to compare the nucleating behaviour on four types of bioactive surfaces by using the simulated body fluid (SBF) model with the presence albumin. Titanium discs were blasted (B) and then prepared by alkali and heat treatment (AH), anodic oxidation (AO), fluoridation (F), or hydroxyapatite coating (HA). The discs were immersed in SBF with 4.5 mg/ml albumin for 3 days, 1, 2, 3 and 4 weeks and analysed with scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and X-ray photoelectron spectroscopy (XPS). Topographic surface characterisation was performed with a contact stylus profilometer. The results demonstrated that the bioactive surfaces initiated an enhanced calcium phosphate (CaP) formation and a more rapid increase of protein content was present on the bioactive surfaces compared to the blasted control surface. The observation was present on all bioactive surfaces. The fact that there was a difference between the bioactive surfaces and the blasted control surface with respect to precipitation of CaP and protein content on the surfaces support the fact that there may be biochemical advantages in vivo by using a bioactive surface.
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| 9. |
- Göransson, Anna, 1970, et al.
(författare)
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An in vitro comparison of possibly bioactive titanium implant surfaces.
- 2009
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Ingår i: Journal of Biomedical Materials Research Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 88:4, s. 1037-1047
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to compare Ca and P formation (CaP) and subsequent bone cell response of a blasted and four different possibly bioactive commercially pure (cp) titanium surfaces; 1. Fluoride etched (Fluoride), 2. Alkali-heat treated (AH), 3. Magnesium ion incorporated anodized (TiMgO), and 4. Nano HA coated and heat treated (nano HA) in vitro. Furthermore, to evaluate the significance of the SBF formed CaP coat on bone cell response. The surfaces were characterized by Optical Interferometry, Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). CaP formation was evaluated after 12, 24 and 72 h in simulated body fluid (SBF). Primary human mandibular osteoblast-like cells were cultured on the various surfaces subjected to SBF for 72 h. Cellular attachment, differentiation (osteocalcin) and protein production (TGF-beta(1)) was evaluated after 3 h and 10 days respectively. Despite different morphological appearances, the roughness of the differently modified surfaces was similar. The possibly bioactive surfaces gave rise to an earlier CaP formation than the blasted surface, however, after 72 h the blasted surface demonstrated increased CaP formation compared to the possibly bioactive surfaces. Subsequent bone cell attachment was correlated to neither surface roughness nor the amount of formed CaP after SBF treatment. In contrast, osteocalcin and TGF-beta(1) production were largely correlated to the amount of CaP formed on the surfaces. However, bone response (cell attachment, osteocalcin and TGF-F production) on the blasted controls were similar or increased compared to the SBF treated fluoridated, AH and TiMgO surface. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008.
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| 10. |
- He, Wenxiao, 1985, et al.
(författare)
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Formation of Bone-like Nanocrystalline Apatite Using Self-Assembled Liquid Crystals
- 2012
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 24:5, s. 892-902
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Tidskriftsartikel (refereegranskat)abstract
- A two-step process using liquid crystalline phases combined with controlled postcrystallization for the preparation of bone-like apatite has been developed. First, amorphous calcium phosphate (ACP) spherules with a diameter of 10.8 +/- 1.4 nm and specific surface area (SSA) in the range of 150-170 m(2)/g were synthesized within a reverse hexagonal liquid crystalline (LC) phase. Second, the ACP spherules were dispersed and aged in Milli-Qwater, where they crystallized into poorly crystalline apatite (PCA). The addition of heparin during aging was explored, which was shown to retard the ACP - PCA conversion. The particle formation within the LC phase was monitored using synchrotron small-angle X-ray scattering, and the formed materials were characterized by X-ray diffraction, conventional and high-resolution transmission electron microscopy, nitrogen adsorption, thermogravimetry with infrared-coupled analysis, and Raman spectroscopy. The PCA formed using the LC aging route presented bone-resembling features, such as,Ca2+ and OH- deficiency, CO32- substitution, poor crystallinity; and ultrahigh SSA of 356 m(2)/g. The resulting particles were compared to hydroxyapatite synthesized via a conventional water-based precipitation method. The LC-aging route exhibited excellent controllability over the CaP crystallization, which enabled facile tailoring of the resulting material properties for different types of application.
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| 11. |
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| 12. |
- Meirelles, Luiz, 1974, et al.
(författare)
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Bone reaction to nano hydroxyapatite modified titanium implants placed in a gap-healing model
- 2008
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Ingår i: Journal Biomedical MAterials Research - A. - : Wiley. - 1549-3296 .- 1552-4965. ; 87:3, s. 624-631
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Tidskriftsartikel (refereegranskat)abstract
- Nanohydroxyapatite materials show similar chemistry to the bone apatite and depending on the underlying topography and the method of preparation, the nanohydroxyapatite may simulate the specific arrangement of the crystals in bone. Hydroxyapatite (HA) and other CaP materials have been indicated in cases in which the optimal surgical fit is not achievable during surgery, and the HA surface properties may enhance bone filling of the defect area. In this study, very smooth electropolished titanium implants were used as substrata for nano-HA surface modification and as control. One of each implant (control and nano HA) was placed in the rabbit tibia in a surgical site 0.7 mm wider than the implant diameter, resulting in a gap of 0.35 mm on each implant side. Implant stability was ensured by a fixating plate fastened with two side screws. Topographical evaluation performed with an optical interferometer revealed the absence of microstructures on both implants and higher resolution evaluation with AFM showed similar nanoroughness parameters. Surface pores detected on the AFM measurements had similar diameter, depth, and surface porosity (%). Histological evaluation demonstrated similar bone formation for the nano HA and electropolished implants after 4 weeks of healing. These results do not support that nano-HA chemistry and nanotopography will enhance bone formation when placed in a gap-healing model. The very smooth surface may have prevented optimal activity of the material and future studies may evaluate the synergic effects of the surface chemistry, micro, and nanotopography, establishing the optimal parameters for each of them.
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| 13. |
- Meirelles, Luiz, 1974, et al.
(författare)
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Effect of hydroxyapatite and titania nanostructures on early in vivo bone response
- 2008
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Ingår i: Clinical Implant Dentistry and Related Research. - : Wiley. - 1708-8208 .- 1523-0899. ; 10:4, s. 245-254
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Hydroxyapatite or titania nano structures were applied on smooth titanium implant cylinders. The aim was to investigate whether nano HA may result in enhanced osseointegration compared to nano titania structures. Material and Methods: Surface topography evaluation included detailed characterization of nano size structures present at the implant surface combined with surface roughness parameters at the micro- and nano- meter level of resolution. Microstructures were removed from the surface to ensure that bone response observed was dependent only on the nanotopography and/or chemistry of the surface. Early in vivo bone response (4 weeks) evaluation was investigated in a rabbit model. Results: In the present study, nano titania coated implants showed an increased coverage area and feature density, forming a homogenous layer compared to nano HA implants. Bone response observed at 4 weeks could not be explained by the surface chemistry. New formed bone connected to the original cortical bone demonstrated an increase of 24% for the nano titania compared to the nano HA implant, although the difference was not statistically significant. Conclusion: Thus, no evidence of enhanced bone formation to nano hydroxyapatite modified implants was observed compared to nano titania modified implants. The presence of specific nano structures; dependent on the surface modification exhibiting different size and distribution did modulate in vivo bone response.
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| 14. |
- Meirelles, Luiz, 1974, et al.
(författare)
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The effect of chemical and nano topographical modifications on early stage of osseointegration
- 2008
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Ingår i: The International Journal of Oral & Maxillofacial Implants. - 0882-2786. ; 23:4, s. 641-7
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the effect of chemically modified implants with similar micro but different nano topography on early stage of osseointegration. Materials and Methods: Screw shaped implants were placed in the flat proximal medial tibial methaphyses of 10 New Zealand white rabbits. Blasted (control); blasted-fluoride and blasted-nano HA implants were investigated. Surface evaluation included chemical analyses with x-ray photoelectron spectroscopy, morphological analyses with scanning electron microscopy and topographical analyses with interferometry. Bone response was investigated with removal torque measurements and histological analyses after a healing period of 4 weeks. Results: Chemical analyses revealed the presence of Ti, O, C and N in all implant groups. The blasted-F group revealed F and the blasted nano HA group Ca and P with simultaneous decrease of Ti and O. Surface roughness parameters showed a slight decrease of the average height deviation for the blasted nano-HA and blasted-F compared to the blasted control implants. SEM images at high magnification indicated the presence of nano structures on the chemically modified implants. Removal torque (RTQ) mean values revealed an increase of 17% to 25% for the chemically modified implants compared to the control implants and the histological analyses demonstrated a similar enhanced bone formation to the chemically modified implants with nanostructures. Conclusion: Chemical modifications used in the present study were capable of producing a unique nano topography and together with the ions present at the implant surface may explain the increased RTQ and histomorphometric values after a healing period of 4 weeks.
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