Microstructure and Properties of Plasma Sprayed Bioactive Glass Ceramics CoatingsPart of:
Natural bone derived glass-ceramics are promising biomaterials for implants. Due to their price and mechanical properties however they are preferably applied as coatings on load bearing implants. The presentation will describe result obtained by plasma spraying of bioactive glass ceramics containing natural bone onto selected implant materials such as stainless steel, alumina, and titanium alloy.
The coating thickness measured by computed X-ray tomography is about 0.2 to 0.3 mm. The microstructure of coatings as well as the interface between the substrates and coatings were tested by SEM of cross sections. The results show a defect free interface between the support and the coating. No cracks or gaps are observed in the substrate to coating interface. SBF treatment of plasma sprayed coating is not influencing the boundary between the support and the coating.
As a result of the above described plasma spraying of the protein free and the sintered protein free bovine bone containing glass-ceramics a crack free, nearly dense, low porosity coatings was obtained. The plasma spraying modifies the phase composition, and new calcium phosphate phases e.g. α-whitlockite, tetracalcium phosphate, etc. are formed at the high temperature of the plasma. Adherence of the coating is excellent, and the process itself is beneficial to the dissolution properties, because the dissolution rate is slower as compared to the bulk material.
The surface of all substrates is fully covered by these plasma sprayed coatings. Although the coatings do not show a fully dense, pore free microstructure, they perfectly cover the substrates and have low porosity. Pre-treated protein free bovine bone containing coatings have smaller porosity, higher Vickers microhardness in bulk, and higher compressive strength. Such microstructure will easily dissipate mechanical stresses and will not deteriorate even after the subsequent SBF-treatment (during the formation of a new Ca-phosphate layer), they will neither crack nor scale.
This way the specific surface is higher and therefore it will provide a better contact with the body fluid which in turn promotes the formation of a new layer and enhances the binding of implants.