| Bone defects are common in clinic. Therapy to bone defects, especially defects in load-bearing position or large bone defects has been a long-standing problem. Up to date, commonly used bone defect repairing technologies include allograft, autograft, heterograft and the application of bone substitute. Autograft will result in new wound and bone defects in other locus and it is also very difficult to obtain bone in the exact shape of the defect. Allograft and heterograft may cause immune rejection and infectious diseases. Organic substance-free or decalcified bone lacks biomechanical strength and thus, is not ideal for clinic application. Although some progress has been made in the research of application of tissue engineering bone substitute for bone defect repairing and it may be used in the future, but until now, it is not feasible for clinical application. Therefore, the application of bone substitutes is the major means for bone defect repairing.Ideal bone grafting materials must satisfy some requirements such as imitation in composition, structure and shape to natural bone, functional restoration and compatibility in biomechanics. Up to date, all developed bone substitute materials (including ceramics, polymers, metals and composites) have their own advantages and disadvantages. Hydroxyapatite, which represents calcium phosphate ceramics family, is similar in composition with natural bone. It is biocompatible, osteoconductive and easy to fabricate to the exact shape as required. Especially, since the discovery of osteogenesis when Ca-P materials were implant in soft tissue at the end of the 80's of the last century, osteoinductivity of porous calcium phosphate ceramics has been well accepted all over the world. Recently, osteoinductivity of calcium phosphate ceramics has attracted much research interests. However, the biomechanical property of calcium phosphate ceramics is not ideal. Although it has been widely applied as bone substitute, it is limited to be used in non-load-bearing part due to its toughness and shortages in anti-fatigue property. When it is used in load-bearing position, the implantation always fails due to its biomechanics. On the other hand, titanium has been widely used in clinic as bone substitute and has been confirmed to be excellent in biocompatibility. When implanted in bone, titanium implant can be integrated inbone well. While compared with other metals, its elastic module is closer to bone and thus, it facilitates stress conduction between bone-titanium interfaces. Moreover, it has sufficient mechanical strength and elasticity to support human body. Unfortunately, it lacks osteoinductivity.Having combined the advantages of calcium phosphate ceramics and titanium, calcium phosphate ceramics coated titanium and titanium alloy have good prospect. To obtain both bioactivity and biomechanics, titanium substrates can be geometrically designed to fit the bone defects to avoid stress-shielding. On the other hand, because its porous structure facilitates the tissue ingrwoth and osteoblast adhesion, proliferation differentiation and gene expression, calcium phosphate ceramics coating could enhance the bioactivity of the implant and bone-implant integration.Coated materials are important parts of biomedical materials, especially, titanium and titanium alloys coated with hydroxyapatite have broad applications in clinic. This study systematically studied the solubility, biomineralization of plasma sprayed calcium phosphate coatings after different post-treatment methods. Result showed that after plasma-sprayed coatings were post-treated with different atmosphere and temperature, coatings with different composition and crystallinity can be obtained. In the process of post-treatment, temperature was crucial to the increase of crystallinity while water vapor is advantageous to the growth of crystal particle size. When the coatings were immersed in SBF and Tris-HCl solution, the dissolution of Ca ions occurred through ion exchange on the particle surface and thus, was strongly rel... |
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