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  • 1
    Digitale Medien
    Digitale Medien
    Effect of calcium phosphate coating composition and crystallinity on the response of osteogenic cells in vitro (2003)
    Oxford, UK : Munksgaard International Publishers
    Clinical oral implants research 14 (2003), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The aim of this study was to investigate the effect of calcium phosphate coating crystallinity and composition on the proliferation and differentiation of rat bone marrow (RBM) cells. Grit-blasted titanium substrates were provided with thin sputter-coated calcium phosphate (Ca-P) films of different composition. The Ca-P-coated substrates were used as-sputtered or were heat-treated. XRD measurements showed that the as-sputtered coatings had an amorphous structure, whereas the heat-treated substrates showed an amorphous–crystalline structure. RBM cells were cultured on these substrates and on noncoated titanium substrates. After specific culture times, the expression of osteogenic markers by the cells was studied. On the amorphous–crystalline coatings as well as on titanium substrates, RBM cells proliferated, expressed alkaline phosphatase and showed mineralization. More mineralization was found on the amorphous–crystalline coatings than on the titanium substrates. Some precipitation was also found on substrates that were incubated in complete culture medium without cells. This precipitate disappeared after prolonged incubation. Alkaline phosphatase expression differed on the various amorphous–crystalline Ca-P-coated substrates, but no difference was found in the mineralization on these substrates. The amorphous Ca-P coatings showed extensive dissolution and some signs of precipitation after longer culture periods. Proliferation and differentiation of RBM cells was not seen on the amorphous coatings, regardless of Ca-P composition. We conclude that amorphous–crystalline Ca-P coatings stimulate differentiation of RBM cells, with only limited differences between coatings of various composition. In contrast, Ca-P coatings with an amorphous structure inhibit the growth and differentiation of RBM cells. This effect was found on all amorphous substrates, regardless of Ca-P composition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1600-0501.2003.00886.x
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  • 2
    Digitale Medien
    Digitale Medien
    Bone formation in Transforming Growth Factor beta-1-loaded titanium fiber mesh implants (2002)
    Copenhagen : Munksgaard International Publishers
    Clinical oral implants research 13 (2002), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The osteoconductive properties of porous titanium (Ti) fiber mesh with or without a calcium phosphate (Ca-P) coating and osteoinductive properties of non-coated Ti fiber mesh loaded with recombinant human Transforming Growth Factor beta-1 (rhTGF-β1) were investigated in a rabbit non-critical size cranial defect model. Nine Ca-P-coated and 18 non-coated porous titanium implants, half of them loaded with rhTGF-β1, were bilaterally placed in the cranium of 18 New Zealand White rabbits. At 8 weeks postoperative, the rabbits were sacrificed and the skulls with the implants were retrieved. Histological analysis demonstrated that in the TGF-β1-loaded implants, bone had been formed throughout the implant, up to its center, whereas in the non-loaded implants only partial ingrowth of bone was observed. Bone formation had a trabecular appearance together with bone marrow-like tissue. No difference in ingrowth could be observed between the non-TGF-β1-loaded non-coated implants and the Ca-P-coated ones. All histological findings were confirmed by image analysis: 97% ingrowth was seen in the rhTGF-β1-loaded implants, while only 57% and 54% ingrowth was observed in the non-loaded Ca-P-coated and non-coated implants, respectively. Bone surface area and bone fill were significantly higher in the rhTGF-β1-loaded implants (1.37 mm2 and 36%, respectively) than in the non-loaded implants (0.57 mm2 and 26%). No statistical difference was found for any parameter between the Ca-P-coated and non-coated implants. Quadruple fluorochrome labeling showed that in the Ti and Ti-CaP implants mainly bone guidance had occurred from the former defect edge, while in the Ti-TGF-β1 implants bone formation had mainly started in the center of a pore and proceeded in a centrifugal manner. Our results show that: (1) the combination of Ti-mesh with TGF-β1 can induce orthotopic bone formation; (2) Ti-fiber mesh has good osteoconductive properties; (3) a thin Ca-P coating, as applied in this study, does not seem to further enhance the bone-conducting properties of a titanium scaffold material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1600-0501.2002.130112.x
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  • 3
    Digitale Medien
    Digitale Medien
    Bone healing capacity of titanium plasma-sprayed and hydroxylapatite-coated oral implants (1998)
    Copenhagen : Munksgaard International Publishers
    Clinical oral implants research 9 (1998), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The influence of surface quality, in particular surface topography and implant material, was evaluated by inserting titanium- and hydroxylapatite plasma-sprayed coated implants into the maxilla of 10 goats. Three types of plasma-spray coatings were applied to tapered, screw shaped implants; titanium plasma-spray coating (TPS), titanium plasma-spray coating with additional acid passivation (TPSA) and a bilayered coating (TPS/HA) consisting of titanium plasma-spray coating (TPS) and a hydroxylapatite part (HA). In addition, as machined implants (TIM) were used as control. A total of 40 implants were inserted according a balanced split plot design. At the end of a 3-month healing period, it appeared that 5 implants (2 TPS, 1 TPSA, 1 TPS/HA and 1 TiM) were lost. Histological examination revealed a stronger bone response to TPS/HA coated implants. Even the TPS/HA coated implants induced bone formation on the part of the implant inserted into the sinus. No signs of delamination of the TPS coatings were visible. The HA part of the dual coating showed signs of degradation. Histomorphometrical analysis confirmed these findings. A significant difference in bone contact (P〈0.05) was measured between the TPS/HA coated implants and the other types of implants. Linear regression (r〉0.2) showed no correlation between the inscrew values at the base line and the bone contact measurements 3 months after healing. On the basis of these results, we can conclude that the chemical composition of the HA coating has a positive influence on the bone reaction. The influence of roughness is less evident.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1600-0501.1998.090407.x
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  • 4
    Digitale Medien
    Digitale Medien
    Initial interfacial healing events around calcium phosphate (Ca-P) coated oral implants (1997)
    Copenhagen : Munksgaard International Publishers
    Clinical oral implants research 8 (1997), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The bone response to different calcium phosphate (Ca-P) coated and non-coated titanium implants was evaluated in a goat animal model. Two types of Ca-P coatings have been investigated: an experimental plasma-spray bi-layered Ca-P coating (FA-HA) and an amorphous RF magnetron sputter coating (Ca-P-a). Fifty-four conical screw shaped implants were inserted in the lateral and medial femoral condyles of 18 Saanen goats. After implantation periods of 3, 12 and 24 days, the bone-implant interface was evaluated histologically and histomorphometrically. Light microscopical evaluation revealed that bone formation on the Ca-P coated implants proceeded faster. At 24 days higher percentages of bone contact were measured for both Ca-P coated implants than for non-coated implants. However, this difference was only significant for the FA-HA coated implants. On basis of these findings. we concluded that Ca-P coatings show improved bone response due to an initial difference in bone cell response.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1600-0501.1997.080506.x
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  • 5
    Digitale Medien
    Digitale Medien
    Injectable calcium phosphate cement as a filler for bone defects around oral implants: an experimental study in goats (2002)
    Oxford, UK : Blackwell Science, Ltd
    Clinical oral implants research 13 (2002), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The aim of this study was to evaluate the clinical applicability and biological behavior of a newly developed injectable calcium phosphate (Ca-P) cement as bone filler for gaps around oral implants. Twenty-four step-like implants, creating gaps of 1 and 2 mm, were inserted into the trabecular bone of the medial femoral condyles of six goats. Four different situations were tested: (1) implant + gaps; (2) implant + gaps, but covered with a polylactic acid membrane; (3) implant + gaps that were filled with Ca-P cement; and (4) implant + gaps that were filled with Ca-P cement and covered with a membrane. All implants were left in place for 12 weeks. Histological and quantitative histomorphometrical measurements demonstrated that implants + gaps had generally poor bone contact at the implant base. Furthermore, fibrous encapsulation was observed in the gap part. In contrast, the presence of a membrane promoted bone ingrowth into the gap and also the bone contact at the implant base. Injection of Ca-P cement resulted in an almost complete filling of the gaps around the implant. The cement surface was completely covered by bone. Active resorption and remodeling of cement particles was observed, suggesting a pattern of slow resorption associated with full replacement with newly formed bone. Additional use of a membrane did not result in adjunctive benefits. Bone-to-implant contact at the implant base was comparable with the implants provided only with a membrane. In conclusion, the Ca-P cement used here showed excellent clinical handling properties combined with a superior bone behavior. On the other hand, the degradation rate of the material was still very slow. This current characteristic can hamper the final clinical applicability of the material as gap filler for periimplant or periodontal defects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1600-0501.2002.130311.x
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  • 6
    Digitale Medien
    Digitale Medien
    Effect of microgrooved poly-l-lactic (PLA) surfaces on proliferation, cytoskeletal organization, and mineralized matrix formation of rat bone marrow cells (2000)
    Copenhagen : Munksgaard International Publishers
    Clinical oral implants research 11 (2000), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Previous experiments showed that microgrooved substrate surfaces can influence the in vitro behavior of osteoblast-like rat bone marrow (RBM) cells. Cellular morphology and matrix deposition can be directed by substrate chemistry and topography. RBM cells cultured on poly-l-lactic acid (PLA) exhibit increased mineralization and alkaline phosphatase activity compared to polystyrene substrates. Consequently, the purpose of the present in vitro study is to further evaluate the behavior of RBM cells on microgrooved (groove depth 0.5 to 1.5 μm, groove and ridge width 1 to 10 μm) polystyrene (PS) and PLA surfaces. Besides grooved, also smooth control surfaces were made. Our results confirmed that microtextured surfaces are capable of influencing the behavior of the osteoblast-like RBM cells in vitro. Microtopography did not influence the RBM proliferation rate, or cellular actin organization. However, confocal laser scanning microscopy showed that cellular attachment is dependent on the applied material. Also clear differences were found between textured PS and PLA, with regard to the calcium content. We therefore conclude, that the application of microtextures could possibly influence the bone regeneration around biodegradable PLA devices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1600-0501.2000.011004325.x
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  • 7
    Digitale Medien
    Digitale Medien
    A mechanical evaluation of TiO2-gritblasted and Ca-P magnetron sputter coated implants placed into the trabecular bone of the goat: part 1 (2000)
    Copenhagen : Munksgaard International Publishers
    Clinical oral implants research 11 (2000), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The influence of Ca-P magnetron sputter coated implants on the mechanical anchorage was evaluated in a goat model. Therefore, uncoated and coated screw designed commercially pure titanium TiO2-blasted implants were inserted into the trabecular bone of the femoral condyles of 12 goats. The thicknesses of the coatings were 0.1 μm (CaP-0.1), 1.0 μm (CaP-1) and 4.0 μm (CaP-4). In addition, uncoated TiO2-blasted implants (Ti) were used as control. Evaluation of the interface strength and appearance, using torque test and scanning electron microscopy, was done at implantation periods of 6 and 12 weeks. Although, especially at 6 weeks of implantation, the Ca-P coated implants showed higher failure torque values than the TiO2 blasted implants, the observed differences for type of implant and evaluation period were not significant (P〉0.1). SEM evaluation showed that all implants with failure values of more than 100 N conducted bone growth into their screw threads. In addition, we observed that the fracture plane for the CaP-4 implants was situated at the coating–implant interface or inside the coating. For the CaP-1 and CaP-0.1 the fracture line could not be determined definitely. For the Ti implants, the fracture torque testing resulted in failure at the bone–implant interface. Therefore, we conclude that all implants resulted in a good bonding strength with the surrounding bone. The sputtered Ca-P coatings seemed to improve the initial fixation of the TiO2 blasted implants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1600-0501.2000.011004305.x
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  • 8
    Digitale Medien
    Digitale Medien
    Swallowing thresholds of mandibular implant-retained overdentures with variable portion sizes (2004)
    Oxford, UK : Munksgaard International Publishers
    Clinical oral implants research 15 (2004), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: We analysed the effect of three portion sizes Optocal Plus (small, medium and large) on swallowing thresholds in subjects with either conventional complete dentures or mandibular implant-retained overdentures (transmandibular and permucosal cylindric implants). Tests were carried out in 52 women and 15 men (mean age 59 years) 4 years after treatment in a randomised controlled clinical trial. The results indicated that the degree of mucosal support for the mandibular denture did not affect the number of chewing strokes, time till swallowing or swallowed particle size. Only the chewing rate differed: subjects wearing mandibular implant-retained overdentures chewed the food at a higher rate than complete-denture wearers. With larger portion sizes, subjects needed significantly more chewing strokes and time until swallowing and they would have swallowed larger particles. Men chewed their food more efficiently than women, as they used the same number of chewing strokes and time, but achieved a greater particle size reduction at the swallowing moment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1600-0501.2004.01006.x
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  • 9
    Digitale Medien
    Digitale Medien
    Ceramic hydroxyapatite coating on titanium implants drives selective bone marrow stromal cell adhesion (2003)
    Oxford, UK : Munksgaard International Publishers
    Clinical oral implants research 14 (2003), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The aim of this study was to determine the cell characteristics that regulate implant osseointegration. The heterogeneity of bone marrow stromal cells obtained from 11 donors was assessed by measuring the expression of a large panel of adhesion molecules. Large differences in expression of adhesion molecules were detected depending on the culture conditions used. Cells cultured in fetal bovine serum induced the expression of different adhesion molecules from cells cultured in human serum. Donor-to-donor variation was determined by measuring the expression of adhesion molecules for stromal cells obtained from different donors that were processed identically. Fat adherent cells but also loose bone marrow cells showed large differences in expression of some but not all adhesion molecules. The flow cytometric data demonstrated large heterogeneity in expression of adhesion molecules, and this heterogeneity was influenced by culture conditions and varied from donor to donor. This demonstrates that the implant encounters different cell types, which could lead to different levels of integration. Surprisingly, in vitro only a subfraction of bone marrow stromal cells attached to titanium coated with ceramic hydroxyapatite. Adaptation of all cell types present in heterogeneous bone marrow to a coated surface is apparently not possible. Differential binding was not caused by aberrant staining of the stromal cells as the results were confirmed with bone marrow cells obtained from transgenic GFP mice. These results demonstrate that hydroxyapatite ceramics are selective in cell recruitment from the bone marrow, explaining the differences found in vivo for these coatings compared with titanium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1600-0501.2003.00949.x
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  • 10
    Digitale Medien
    Digitale Medien
    A histological evaluation of TiO2-gritblasted and Ca-P magnetron sputter coated implants placed into the trabecular bone of the goat: part 2 (2000)
    Copenhagen : Munksgaard International Publishers
    Clinical oral implants research 11 (2000), S. 0 
    Details
    ISSN: 1600-0501
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The aim of this study was to investigate the synergetic influence of surface topography and chemical composition of oral implant materials on bone response. For the experiment screw designed implants were used. The implants were grit-blasted with TiO2 particles. The implants were left uncoated (Ti) or provided with three different amorphous/crystalline Ca-P magnetron sputter coatings, resp. 0.1 μm (CaP-0.1), 1 μm (CaP-1) and 4 μm (CaP-4), in thickness. The implants were inserted in the medial femoral condyles of 12 goats. Each femur received 2 implants. After implantation periods of 6 and 12 weeks the implants were retrieved and prepared for histological and histomorphometrical evaluation (bone contact and bone mass). The light microscopy revealed that bone response to CaP-4 and CaP-1 implants was similar. For example, after 12 weeks, screw threads were almost completely covered with bone. In contrast to CaP-0.1 and Ti implants, where bone apposition was less pronounced. Histomorphometry demonstrated that the bone-to-implant contact for the CaP-1 and CaP-4 implants was significantly higher (P〈0.05) than for the CaP-0.1 and Ti implants. This difference existed already after 6 weeks and was even enhanced after 12 weeks. The bone mass measurements revealed that only at 12 weeks CaP-4 implants had significantly more bone contact inside the screw threads than non-coated Ti-implants (P〈0.05). Supported by our findings, we conclude that the additional application of a 1–4 μm thick Ca-P magnetron sputter coating can further improve the healing response to surface roughened oral implants placed into trabecular bone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1600-0501.2000.011004314.x
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