| Several studies have demonstrated, that the mismatch in stiffness between bulk metal implants and human bone causes stress shielding phenomena, leading to bone remodelling and eventually loosening of the implant. In the design of dental implants and synthetic joints, groove or cavity was usually designed. But until now it is not easy that bone tissue is conducted growing into the cavities and grooves and tightly combine with the surface of implant because the cavities are often filled by soft tissue and sludged blood. It is important work to keep the space for new bone growing into and contact uninterruptedly between biomaterials and new bone tissue. Biodegradable materials could be degraded gradually and replaced by new bone tissue to achieve recovery perfectly, so it can be used for osteoconduction. The porous biomaterial can be filled into cavity of the titanium implant. It can induce bone tissue growth into the narrow cavity gradually after implanting, then achieve firm mechanical fixation.Theα-TCP andβ-TCP porous composite material was obtained by using NaHCO3 as vesicant. XRD results revealed that the hydroxyapatite(HAP) andβ-TCP phases are dominant, and there were a small quantity ofα-TCP and very few of impurity. SEM image indicates that the hydration products possesses fibre shaped HAP crystal which conglutinated and enwraped theβ-TCP crystal. There are a lot of macropores and micropores interconnected structure in the composite material.In this paper the freeze-drying method was used to make the chitosan(CS)/calcium phosphate system porous composite biomaterial. As XRD shows that the inorganic product is still amorphous phase. SEM image reveals that a large number of calcium phosphate crystal distributed in chitosan matrix uniformly, and the composite biomaterial exists a plenty of porous at a range from 50 to 200μm.The two kind of composites combine with Ti tubes(φ4×8mm). The Ti tubes' cavities were filled with the two kinds of composites. The bone implants were embedded into dog's tibia, and removed after 2.5,3,3.5,4,5 months of implantation. The implant combined with tibia tightly, as showed in X-ray photos.The specimen, that is material and tissue in the cavities of Ti tubes, is stained with haematoxylin-eoxin(HE). There is no material in the blank sample's cavity, and it has a lot of spare space, which is placed by a great deal of lipocyte after 2.5 to 3.5 months of implantation. And then the lipocyte reduces slowly, and is replaced by new cells and new bone tissue.The chitosan(CS)/calcium phosphate system porous composite, which is implanted in dog's tibia for 2.5 months, is degraded completely. And it grows more new bone tissue than the blank specimen. That proves that the porous composite could achieve inducing bone tissue growth into narrow cavity in early phase after implantation. But the speed of material biodegradation is far faster than the new bone growth, so lipocyte, which would disturb the normal tissue growth, invade in the spare space.The main reaction is degraded for after 2.5 months implantation. The HAP andβ-TCP porous composite is embedded into dog's tibia. As degradable of material, the new bone tissue grows gradually. It matches well that the speed of material degradable and bone growth. That means the HAP andβ-TCP porous composite could induce bone tissue growth into narrow cavity in bone implant. |
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