| 1. |
- Brånemark, Rickard, 1960, et al.
(författare)
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Biomechanical characterization of osseointegration during healing: an experimental in vivo study in the rat.
- 1997
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Ingår i: Biomaterials. - 0142-9612. ; 18:14, s. 969-78
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Tidskriftsartikel (refereegranskat)abstract
- This study reports torsion tests and pull-out tests on osseointegrated commercially pure titanium fixtures. The tests were performed in vivo on a total of 26 rats. Three fixtures with a diameter of 2.0 mm were installed bilaterally in the proximal tibia in each animal. The mechanical testing was performed immediately after installation, after 2, 4, 8 and 16 weeks of unloaded healing. The torsional strength started to increase after 4 weeks of unloaded healing and there was a significant increase with time during the initial 16 weeks. The pull-out load increased rapidly during the first 4 weeks; thereafter, a moderate increase occurred during the following 12 weeks. A histological evaluation was performed after 0, 4, 8 and 16 weeks. There were significant (P < 0.01) correlations between torque and percentage of bone in contact with the fixture, and between pull-out load and the bone thickness around the fixture (P < 0.001). Estimations of shear stresses and shear moduli in the bone tissue (pull-out test) and at the interface (torque test) indicated that the increase in bone volume around the implant substantially improved the mechanical capacity.
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| 2. |
- Esposito, Marco, 1965, et al.
(författare)
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Immunohistochemistry of soft tissues surrounding late failures of Brånemark implants.
- 1997
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Ingår i: Clinical oral implants research. - 0905-7161. ; 8:5, s. 352-66
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the present investigation was to characterize the cellular composition of the soft tissues surrounding consecutively retrieved late failures of Brånemark implants. Criteria for implant failure were signs of loss of osseointegration (radiographic peri-fixtural radiolucency and mobility). The clinical history of the implants did not include adverse symptoms. At the time of retrieval, percussion-induced pain was experienced at 4/8 implants, but no macroscopical signs of inflammation or infection or infection was observed. Immunohistochemistry was applied on 6 marginal peri-implant specimens and on specimens of deeper tissues associated with the previously load-bearing implant surface from 8 failed implants, whereas 6 clinically healthy mucosal specimens and 4 hyperplastic biopsies from stable implants served as controls. The immunohistochemical evaluation showed that the soft tissues surrounding failed implants contained a large number of macrophages (CD68), HLA-DR positive cells, lymphocytes and plasma cells preferentially accumulated towards the removed implant surface. PMNs were a rare finding. Downgrowth of epithelium, in some cases encapsulating the whole fixture, was observed in sections where an intact implant/soft tissue interface was preserved. Healthy control mucosal specimens always contained labelled cells, albeit in a low amount, whereas hyperplastic control samples displayed an intense inflammatory and immunological response with numerous positive cells and PMNs scattered throughout the biopsy. In conclusion, failed implants were characterized by a chronic inflammatory response of the surrounding tissues with macrophages as the predominant labelled cell type, while hyperplastic tissues around stable implants were distinguished by an acute inflammatory process. These findings suggest that an on-going infection is unlikely to be the etiological factor for the late failures of dental implants examined in this study.
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| 3. |
- Brånemark, Rickard, 1960, et al.
(författare)
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Biomechanical and morphological studies on osseointegration in immunological arthritis in rabbits.
- 1997
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Ingår i: Scandinavian journal of plastic and reconstructive surgery and hand surgery / Nordisk plastikkirurgisk forening [and] Nordisk klubb for handkirurgi. - 0284-4311. ; 31:3, s. 185-95
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Tidskriftsartikel (refereegranskat)abstract
- The biomechanics and morphology of the interface between bone tissue and threaded, commercially pure titanium implants were studied i an experimental model of monoarticular arthritis in New Zealand white rabbits (n = 8). Two of the eight rabbits died before evaluation. Immunisation with bovine serum albumin (BSA) and repeated intra-articular injections with BSA in one knee joint elicited an immune response and clinical signs of inflammation. The opposite joint was injected with saline. Three implants were inserted intra-articularly in the lateral femoral condyle in each joint. After a period of six weeks the stability of two of the three implants was evaluated by pull-out and torsion tests using a standardised biomechanical model. The rabbits were killed by perfusion fixation, and the implants and surrounding tissue were retrieved en bloc for histological analysis. The amount of bone, the degree of bone apposition, and the biomechanical evaluation showed that the absolute mechanical capacity of anchorage was not significantly reduced on the arthritic side compared with the control knees. These results indicate that it might be possible to obtain osseointegration in juxta-articular bone despite local joint inflammation.
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| 4. |
- Larsson Wexell, Cecilia, 1965, et al.
(författare)
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Bone response to surface modified titanium implants - studies on the tissue response after 1 year to machined and electropolished implants with different oxide thicknesses.
- 1997
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Ingår i: Journal of materials science. Materials in medicine. - 0957-4530. ; 8:12, s. 721-9
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Tidskriftsartikel (refereegranskat)abstract
- The bone formation around titanium implants with varied surface properties was investigated after 1 year in rabbits. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits. Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads. There were no significant differences between the differently prepared implant groups. Our study shows that a high degree of bone contact and bone formation is achieved after 1 year with titanium implants which are modified with respect to oxide thickness and surface topography. There is no indication that a reduction of surface roughness, which in the initial phase decreases the rate of bone formation, had any influence on the amount of bone after 1 year in rabbit cortical bone.
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| 5. |
- Thomsen, Peter, 1953, et al.
(författare)
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Structure of the interface between rabbit cortical bone and implants of gold, zirconium and titanium.
- 1997
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Ingår i: Journal of materials science. Materials in medicine. - 0957-4530. ; 8:11, s. 653-65
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Tidskriftsartikel (refereegranskat)abstract
- The role of surface properties (chemical and structural) for the interaction between biomaterials and tissue is not yet understood. In the present study, implants made of titanium, zirconium (transition metals with surface oxides) and gold (metallic surface) were inserted into the rabbit tibia. Light microscopic (LM) morphometry showed that after 1 and 6 mo the gold implants had less amount of bone within the threads and a lower degree of bone-implant contact than the titanium and zirconium implants, which did not differ from each other. These quantitative differences were supported by LM and ultrastructural observations of the interface. The ultrastructural observations in addition demonstrated that the layer of non-collagenous amorphous material located between the implant and the calcified bone was appreciably thicker around zirconium than around titanium implants. The factors potentially responsible for the observed morphological differences in the bone around the different material surfaces are discussed.
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| 6. |
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