| 1. |
- Hansson, Stig, et al.
(författare)
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Characterisation of Titanium Dental Implants. II: Local Biomechanical Model
- 2010
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Ingår i: The Open Biomaterials Journal. - : Bentham Science Publishers Ltd.. - 1876-5025. ; 2, s. 36-52
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical model for estimation of the bone-to-implant interfacial shear strength induced by implant surface roughness has been developed. Two different assumptions regarding the constitutive behaviour of the interfacial bone were made. 1) The bone exhibits an ideally plastic deformation – the plastic mode. 2) The bone exhibits a linearly elastic deformation – the elastic mode. In the plastic mode it was found that the estimated interfacial shear strength was directly proportional to the 2D surface roughness parameter mean slope. For the elastic mode a new 2D surface roughness parameter was defined. With this parameter a direct proportionality between parameter value and estimated interfacial shear strength was also obtained in the elastic mode. The model was extended into 3D mode. The model was used to evaluate topographies of implant surfaces. The calculated results showed a similar trend to interfacial shear strength results reported in vivo.
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| 2. |
- Hansson, Stig, et al.
(författare)
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Global biomechanical model for dental implants.
- 2011
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Ingår i: Journal of biomechanics. - : Elsevier BV. - 1873-2380 .- 0021-9290. ; 44:6, s. 1059-65
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Tidskriftsartikel (refereegranskat)abstract
- The osseointegration of titanium dental implants is a complex process and there is a need for systematization of the factors influencing anchoring of implant. A common way of analyzing the strength of the fixation in bone is by measuring the torque required to remove the implants after healing. In this paper, a global biomechanical model is introduced and derived for removal torque situations. In this model, a gap is allowed to form between the bone and the implant and the size of the gap at fracture is a function of the surface roughness and can be shown to be directly related to the mean slope of the surface. The interfacial shear strength increases almost linearly with the mean slope and was also found to increase with an increase in the 2D surface roughness parameter, R(a). Besides the surface roughness, the design of the implant, the bone anatomy and the bone quality were shown to influence the interfacial shear strength. The Global biomechanical model can be used as a tool for optimizing the implant design and the surface topography to obtain high anchoring strength.
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| 3. |
- Johansson, Carina B., 1955, et al.
(författare)
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Enhanced implant integration with hierarchically structured implants: a pilot study in rabbits
- 2012
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Ingår i: Clinical Oral Implants Research. - : Wiley. - 1600-0501 .- 0905-7161. ; 23:8, s. 943-953
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To investigate bone-to-implant bonding for some novel surface modifications with a hierarchic structure and to correlate the in vivo results with surface roughness parameters. Materials and methods: Newly developed implants surfaces were tested in rabbits and compared with the commercially available OsseoSpeed™ (OS) implant. The blasted test samples were subjected to treatment in oxalic acid (AT-II), followed by subsequent etching in hydrofluoric acid (AT-I). Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the surface topography and chemical composition of the implants. Biomechanical testing after 6 weeks of healing was complemented with the quantification of fluorochromes and the results were subjected to a multivariate statistical analysis. Results: The results show, both with biomechanical- and with histomorphometrical tests, that the AT-I implants with different surface roughness at the micro (blasting), submicro (shallow cavities) and nanolevels (precipitates) have a greater bone tissue integration compared with the AT-II- and OS implants. The 2D bone-to-implant contact (BIC) data were in accordance with the 3D removal torque (RTQ) results even if the former were deduced from implants located in spongeous-type bone and the latter in cortical bone. The increase in RTQ values for the test samples AT-I and AT-II compared with the reference complies with the slightly higher Sa values for these surfaces. Conclusions: Using a combination of conventional methods with novel quantification of florochrome and multivariate analysis, the influence of surface roughness on different levels could be discriminated. The RTQ and BIC values show that the most hierarchical structure with submicro cavities and nanoscale precipitates possesses the most favourable osseointegration properties.
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| 4. |
- Löberg, Johanna, 1981, et al.
(författare)
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Characterisation of titanium dental implants I:critical assessment of surface roughness parameters
- 2010
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Ingår i: The Open Biomaterials Journal. - : Bentham Science Publishers Ltd.. - 1876-5025. ; 2, s. 18-35
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Tidskriftsartikel (refereegranskat)abstract
- Titanium is commonly used for dental implants because of its unique ability to get incorporated into living bone. There is an ongoing development to obtain better anchorage and surface properties such as roughness and chemical composition are modified to reach this. In this study titanium dental implant surfaces were characterised by recording the topographical changes induced by each individual processing step such as cleaning, blasting, and HF etching. To fully describe the different surfaces, the same point was analysed before and after each step using Atomic Force Microscopy (AFM) and 3D-Scanning Electron Microscopy (3D-SEM). A set of 3D surface parameters were calculated as a function of filter size to describe the topographic features at different levels. The chemical treatment introduces nano-sized features while blasting changes the topography at the micrometer level and by combining AFM and 3D-SEM the entire range can be assessed. The results show that the chemically induced changes in the topography can only be revealed by AFM while 3D-SEM gives a clear description of the topography of blasted surfaces. The fractal dimension for the chemically treated surface was the same as for the blasted surfaces but crossover size was much smaller. Besides the commonly used Sa parameter it is suggested that the root-mean-square of the surface slope (Sdq) and the void volume (Vvc) parameters are included in the characterisation of rough surfaces. These parameters can be used for correlation with in vivo performance.
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| 5. |
- Löberg, Johanna, 1981, et al.
(författare)
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Electronic properties of anodized TiO2 electrodes and the effect on the in-vitro response
- 2014
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Ingår i: Journal of Biomedical Materials Research. Part B - Applied biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 102:4, s. 826-839
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Tidskriftsartikel (refereegranskat)abstract
- For dental implants, improved osseointegration is obtained by modifying the surface roughness as well as oxide morphology and composition. A combination of different effects contributes to enhanced performance, but with surface roughness as the dominant factor. In order to single out the effect of oxide conductivity on biological response, oxide films with similar thickness and surface roughness but different electronic properties were formed using galvanostatic anodization. Three different current densities were used, 2.4, 4.8 and 11.9 mAcm-2, which resulted in growth rates ranging from 0.2 to 2.5 V/s. The electronic properties were evaluated using cyclic voltammetry and impedance spectroscopy, while the biological response was studied by cell activity and apatite formation. The number of charge carrier in the oxide film close to the oxide/solution interface decreased from 5.810-19 to 3.210-19 cm-2 with increasing growth rate, i.e. the conductivity decreased correspondingly. Cell response of the different surfaces was tested in-vitro using human osteoblast-like cells (MG-63). The results clearly show decreased osteoblast proliferation and adhesion but higher mineralisation activity for the oxide with lower conductivity at the oxide/solution interface. The apatite-forming ability was examined by immersion in simulated body fluid. At short times the apatite coverage was 26% for the anodized surfaces, significantly larger than for the reference with only 3% coverage. After one week of immersion the apatite coverage ranged from 73% to 56% and a slight differentiation between the anodized surfaces was obtained with less apatite formation on the surface with lower conductivity, in line with the cell culture results.
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| 6. |
- Löberg, Johanna, 1981, et al.
(författare)
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Electronic Properties of TiO2 Nanoparticles Films and the Effect on Apatite-Forming Ability.
- 2013
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Ingår i: International journal of dentistry. - : Hindawi Limited. - 1687-8728 .- 1687-8736. ; 2013
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticle-covered electrodes have altered properties as compared to conventional electrodes with same chemical composition. The changes originate from the large surface area and enhanced conduction. To test the mineralization capacity of such materials, TiO2 nanoparticles were deposited on titanium and gold substrates. The electrochemical properties were investigated using cyclic voltammetry and impedance spectroscopy while the mineralization was tested by immersion in simulated body fluid. Two types of nucleation and growth behaviours were observed. For smooth nanoparticle surfaces, the initial nucleation is fast with the formation of few small nuclei of hydroxyapatite. With time, an amorphous 2D film develops with a Ca/P ratio close to 1.5. For the rougher surfaces, the nucleation is delayed but once it starts, thick layers are formed. Also the electronic properties of the oxides were shown to be important. Both density of states (DOS) in the bandgap of TiO2 and the active area were determined. The maximum in DOS was found to correlate with the donor density (N d ) and the active surface area. The results clearly show that a rough surface with high conductivity is beneficial for formation of thick apatite layers, while the nanoparticle covered electrodes show early nucleation but limited apatite formation.
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| 7. |
- Löberg, Johanna, 1981, et al.
(författare)
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Integrated Biomechanical and Topographical Surface Characterization (IBTSC).
- 2014
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Ingår i: Applied Surface Science. - 0169-4332. ; 290, s. 215-222
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Tidskriftsartikel (refereegranskat)abstract
- In an attempt to reduce the need for animal studies in dental implant applications, a new model has been developed which combines well-known surface characterization methods with theoretical biomechanical calculations. The model has been named Integrated Biomechanical and Topographical Surface Characterization (IBTSC), and gives a comprehensive description of the surface topography and the ability of the surface to induce retention strength with bone. IBTSC comprises determination of 3D-surface roughness parameters by using 3D-Scanning Electron Microscopy (3D-SEM) and Atomic Force Microscopy (AFM), and calculation of the ability of different surface topographies to induce retention strength in bone by using the Local model. Inherent in this integrated approach is the use of a length scale analysis, which makes it possible to separate different size levels of surface features. The IBTSC concept is tested on surfaces with different level of hierarchy, induced by mechanical as well as chemical treatment. Sequential treatment with oxalic and hydrofluoric acid results in precipitated nano-sized features that increase the surface roughness and the surface slope on the sub-micro and nano levels. This surface shows the highest calculated shear strength using the Local model. The validity, robustness and applicability of the IBTSC concept are demonstrated and discussed.
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| 8. |
- Mattisson, Ingela, et al.
(författare)
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Surface characterization and electrochemical properties of hierarchically structured titanium surfaces
- 2013
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408. ; 48:2, s. 389-398
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Tidskriftsartikel (refereegranskat)abstract
- Newly designed implant surfaces with hierarchic structure have been characterized with respect to chemical composition, topography, electrical properties and cell culturing. Three levels of surface roughness are induced starting from a blasted surface with the naturally formed oxide layer. Dissolution of the blasted surface is obtained by chemical treatment in oxalic acid. The surface becomes smoother with multitude of shallow depressions in the walls and bottoms of the blasted structure. The surface oxide layer formed is somewhat thicker than the naturally formed oxide and may contain oxalate. In the final step, part of the oxide layer is dissolved in hydrofluoric acid leading to a high concentration of soluble titanium species. A nanostructured surface is formed by precipitation of titanium oxide at spots on the surface where locally the pH is increased due to hydrogen evolution. The surface roughness is only marginally changed by the chemical treatment while the conductivity of the surface layer is lower for the chemically treated surfaces compared with the blasted reference. The hierarchical structure mimics many natural processes for achieving high shear strength.
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