RESUMO
The current study evaluates the in vivo response to free form fabricated cobalt chromium (CoCr) implants with and without hydroxyapatite (HA) plasma sprayed coatings. The free form fabrication method allowed for integration of complicated pyramidal surface structures on the cylindrical implant. Implants were press fit into the tibial metaphysis of nine New Zealand white rabbits. Animals were sacrificed and implants were removed and embedded. Histological analysis, histomorphometry and electron microscopy studies were performed. Focused ion beam was used to prepare thin sections for high-resolution transmission electron microscopy examination. The fabricated features allowed for effective bone in-growth and firm fixation after 6 weeks. Transmission electron microscopy investigations revealed intimate bone-implant integration at the nanometre scale for the HA coated samples. In addition, histomorphometry revealed a significantly higher bone contact on HA coated implants compared to native CoCr implants. It is concluded that free form fabrication in combination with HA coating improves the early fixation in bone under experimental conditions.
Assuntos
Cromo/química , Cobalto/química , Durapatita/química , Tíbia/patologia , Animais , Osso e Ossos/metabolismo , Osso e Ossos/ultraestrutura , Materiais Revestidos Biocompatíveis/química , Feminino , Íons , Teste de Materiais , Microscopia Eletrônica de Transmissão/métodos , Osseointegração , Próteses e Implantes , Coelhos , Propriedades de Superfície , Tíbia/ultraestrutura , TitânioRESUMO
Addition of sugar surfactants, sucrose fatty acid esters and alkylpolyglucosides, to calcium phosphate cement designed for bone reconstruction is described. Thanks to their surface activity and through their adsorption at the surface of the calcium phosphate particles, they both induced a strong increase in the porosity (quantified by Image Analysis) and brought a very good workability. Other properties typically studied for these cements are reported, including setting times, compressive strength, cohesion in water, and effect of sterilization on these properties. The whole study brought good insight in the interest of adding these mild surfactants to improve several properties of the calcium phosphate cement, without impairing their function.
RESUMO
Addition of sugar surfactants, sucrose fatty acid esters and alkylpolyglucosides to a calcium phosphate cement, designed for bone reconstruction, is described. Thanks to their adsorption at the surface of the calcium phosphate particles, the sugar surfactants allowed a full injectability and brought a very good workability. Injectability was measured by monitoring force-distance curves. With some of the selected sugar surfactants adhesive properties of the cement pastes were also observed, which were measured by tack tests. Finally, some properties related to biological applications are described, including gentamicine release and osteoblast viability experiments. The whole study demonstrates that addition of these mild surfactants improved several properties of the calcium phosphate cement, without impairing function.
RESUMO
Chitosan associated to various scaffolds has been shown to promote growth and mineral rich matrix deposition by osteoblasts in vitro, whereas its influence on osteoclast differentiation, which plays also a central role in bone remodeling, has never been described. The purpose of this study was to investigate the differentiation and activity of human preosteoclastic cells on calcium phosphate cement containing 2% chitosan (Cementek/chitosan) compared to the Cementek alone. Human primary osteoclast precursors were cultured directly on both biomaterials in the presence of rhM-CSF and rhRANK-L for 7 days. Using LIVE/DEAD fluorescent assay, tartrate-resistant acid phosphatase staining, scanning electron microscopy and quantitative RT-PCR, we demonstrated that incorporation of chitosan to Cementek does not affect the proliferation and adhesion of preosteoclasts but inhibits the formation of TRACP positive cells and prevents the osteoclastic resorption of the composite biomaterial compared to Cementek alone. This inhibitory effect of chitosan on osteoclast resorption activity should have important implications on bone formation and bone remodeling after in vivo implantation. Indeed, based on the positive results obtained in vivo by several investigators, one can suggest that this property of chitosan can be beneficial for bone regeneration.
Assuntos
Cimentos Ósseos/farmacologia , Fosfatos de Cálcio/farmacologia , Diferenciação Celular/efeitos dos fármacos , Quitosana/farmacologia , Osteoclastos/citologia , Osteoclastos/efeitos dos fármacos , Células-Tronco/citologia , Fosfatase Ácida/genética , Fosfatase Ácida/metabolismo , Materiais Biocompatíveis/farmacologia , Cálcio/metabolismo , Proliferação de Células/efeitos dos fármacos , Forma Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Humanos , Isoenzimas/genética , Isoenzimas/metabolismo , Osteoclastos/enzimologia , Osteoclastos/ultraestrutura , Fosfatos/metabolismo , Plásticos , Células-Tronco/efeitos dos fármacos , Células-Tronco/enzimologia , Células-Tronco/ultraestrutura , Fosfatase Ácida Resistente a TartaratoRESUMO
The association of bone morphogenetic proteins (BMPs) with calcium phosphate bioceramics is known to confer them osteoinductive properties. The aim of this study was to evaluate the surface properties, especially regarding recombinant human BMP-2 (rhBMP-2) adsorption and release, of commercial sintered biphasic calcium phosphate ceramics after coating with biomimetic nanocrystalline apatite. The raw and coated ceramics exhibited similar macroporous structures but different nanometer-sized pores contents. Both types of ceramics showed Langmuir-type adsorption isotherms of rhBMP-2. The coating noticeably increased the rate of adsorption and the total amount of growth factor taken up, but the maximum coverage per surface area unit as well as the affinity constant appeared lower for coated ceramics compared with raw ceramic surfaces. The limited advantage gained by coating the ceramics can be assigned to a lower accessibility of the surface adsorption sites compared with the raw ceramics. The quantity of rhBMP-2 spontaneously released in cell culture medium during the first weeks was lower for coated samples than for uncoated ceramics and represented a minor fraction of the total adsorbed amount. In conclusion, the nanocrystalline apatite coating was found to favor the adsorption of rhBMP-2 while providing a mean to fine tune the release of the growth factor.
Assuntos
Apatitas/química , Proteína Morfogenética Óssea 2/química , Fosfatos de Cálcio/química , Cerâmica/química , Materiais Revestidos Biocompatíveis/química , Durapatita/química , Adsorção , Algoritmos , Humanos , Cinética , Teste de Materiais , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Nanopartículas , Porosidade , Pós , Proteínas Recombinantes/química , Difração de Raios XRESUMO
Many factors have been identified as risk factors for colic in horses in several epidemiological studies. The aim of our paper was to review the results of 12 epidemiological studies, in order to assess the impact of each risk factor for colic. According to the literature, the factors that increase the risk of colic are feeding practices (type and quality of food, type and changes of feeding), the intrinsic factors of horses (sex, age and breed), management (type and changes of housing and activity), medical history (a previous colic, administration of a medical treatment) and parasite control (the presence of worms and type of deworming program). Several individual factors were incriminated as risk factors by all the studies. Nevertheless, the different studies did not always agree on the role of other risk factors. The conclusions were tightly related to several criteria in the selection of the study population, like the type of the epidemiological study, the number and the origin of horses included and the location of the study.