Key Engineering Materials Vols. 336-338

Abstract: Since a small globular particle was first used as support for three-dimensional (3D) growth of anchorage-dependent cells in suspended cultures, a variety of microspheres as tissue engineering scaffolds have been developed. In this paper, β-TCP and chitosan were selected as the components of microspheres due to their biodegradability and osteogenic properties. The biodegradable β-TCP/chitosan composite microspheres were prepared by a solid-in-water-in-oil (s/w/o) emulsion cross-linking method in this paper. The size distribution, surface morphology, and microstructure of the microspheres were evaluated. Scanning electron microscopy revealed that the size of the microspheres with good spherical morphology was distributed in the range of 50~200μm. In vitro immersion experiments were carried out to evaluate the degradability of the microspheres, and the results demonstrated that the chitosan/β-TCP composite microspheres were potential materials as tissue engineering scaffolds for bone repair.

Abstract: β-tricalcium phosphate (β-TCP) added with certain amounts of β-calcium pyrophosphate (β-CPP) was prepared. Degradation behavior of β-TCP/β-CPP ceramic was tested by soaking in Tris solution for 20d. The morphologies of composites before and after degradation were observed by SEM. The weight loss was tested after soaking in immersion solution. The results showed that the β-TCP/β-CPP ceramic had great potential as a biodegradable bone substitute.

Abstract: The aim of this work is to improve the mechanical properties of calcium phosphate bone cement (CPC) by appending chitosan microspheres to CPC base. That chitosan degrades rapidly than bone cement has been proved by previous investigations. Porous CPC has low compressive strength because of the pores in it weakening the structure. Additive chitosan microspheres can improve the mechanical properties by bearing the compress with the CPC base and produce pores after degradation. This study investigates the effect of chitosan microspheres on the setting time, mechanical properties, phase evolution and morphology of CPC. The additive proportion of chitosan microspheres ranges from 0 wt% to 30 wt%. Compared with original CPC, the modified CPC has higher compressive strength, without significantly affecting the chemical properties. The phase composition of the CPC is tested by XRD. The microstructures of CPC are observed using SEM. The final setting times range from 5~15 minutes and can be modulated by using different liquid and powder (L/P) ratio.

Abstract: An injectable calcium phosphate bone cement was prepared by combining amorphous calcium phosphate (ACP) and dicalcium phosphate dihydrate (DCPD) for use in non-invasive surgery in this work. The effect of the conserving time on the viscosity, yield stress and injectability of the calcium phosphate cement (CPC) pastes were studied. The results showed that as the conserving time of the pastes prolonged, the viscosity and the yield stress of the pastes increased exponentially, and the injectability of the pastes decreased. This resulted from the transformation of DCPD and ACP into hydroxyapatite via hydration reaction. The results also indicated that the pastes still exhibited good injectability in even 15 min after preparation of the CPC pastes.

Abstract: In this paper, we study the effect of repairing the dog's femoral defects with the artificial bone integrating the nano-calcium phosphates/zirconia porous artificial bone scaffold with the autologous osteoblasts. We transplanted the artificial bone to the femoral defect of the dog, and at the same time, simple scaffold and the autologous cancellous bone were implanted as the control group. 3 months after the transplantation, the specimen was taken out with complete integration with the bone in these 3 groups and the bone defect got the complete bone union. The mechanics strength test showed that the group of the artificial bone was the strongest, followed by the cancellous bone group, and the simple material group was lower, but the strength was stronger than that before the transplantation. In the sixth month, the complete femoral defect repair was found in each group and the complete formation of the Haversian canal can be found on the histology examination. According to the mechanics strength test, there was no significant difference (P<0.05).

Abstract: In order to improve the bioactivity of calcium phosphate bioceramics, biphasic HA/β-TCP (BCP) bioceramics were prepared by the microwave sintering and the microwave plasma sintering. Bone-like apatite formation of the resulting samples was investigated in simulated body fluid (SBF). The samples were also implanted in dorsal muscles of healthy dogs for 1.5and 3 months. All samples after taking out were examined by histological observation. Bone formation in different sintering ways and temperatures was investigated in details. Better osteoinductivity was found in samples sintered by the microwave and microwave plasma instead of the conventional furnace, as well as by lower temperature (1050 oC) instead of higher temperature (1150 oC). It accounts for that the increase in degradability of materials sintered by microwave and microwave plasma or lower temperature leads to the better of bone-like apatite formation and bone formation due to fine grains and lower crystallinity.

Abstract: Hydroxyapatite (HA) coatings were deposited on titanium substrate by means of pulsed laser deposition (PLD) with Nd:YAG laser. Deposition was carried out at 20 Pa of water vapor atmosphere and at room temperature. An Nd:YAG laser operating at a repetition rate of 10 HZ was used for deposition. In above deposition condition, the HA coatings deposited by PLD at room temperature are amorphous phase, and Ca/P ratio in HA coatings decreases with increasing water vapor pressure. The amorphous HA coatings were recrystallized after hydrothermal treatment at 190°C for 10 h. The bonding strength of the HA coating to the Ti substrate is up to 19.6 MPa. The structure and morphology of samples were characterized by X-ray diffraction, Fourier transform infrared reflection specterophotometry, scanning electron microcopy. The atomic ration of Ca and P was semiquantitatively determined by electron probe micro analyzer.

Abstract: Porous β-TCP scaffold was prepared using three-dimensional gel-lamination technology with foamy slurry. Then the sintered scaffolds were soaked in 1.5SBF solution to achieve scaffolds with bone-like structure. After soaking, a low crystallized bone-like apatite layer containing CO3 -2 was formed on the surface of the scaffold. With presoaking in NaOH solution, the formation of the bone-like apatite layer on the surface of the scaffold in 1.5SBF solution was accelerated. In this way, a bioactive porous β-TCP scaffold with bone-like structure could be prepared.

Abstract: In the present study, bioactive functional gradient coatings were prepared using net-energy controlled plasma spraying technology. The microstructure and phases of the bioactive functional gradient coating were examined by means of transmission electron microscope, scanning electron microscopy and X-ray diffraction. The results revealed that: (1) as-sprayed coatings contained a large amount of amorphous phases and some nano-sized HA crystals formed during rapid solidification, (2) surface of the coating was very rough with different-sized micropores, and the gradient layer was much denser which firmly bonded to the substrate without gaps and obvious interface between the coating and the substrate

Abstract: The present work aimed to evaluate the biological properties between the bioglass coated and uncoated zirconia implants. A total of 24 implants were retrieved. Bioglass coated and uncoated porous implants were implanted in the mandible of 4 dogs. At the experimental times of 4 and 8 weeks after sacrifice, the histological sections specimens of the implants and surrounding tissues were processed to determine the osteointegration rate; The other corresponding implants were processed for SEM microanalysis. A significantly higher affinity index was demonstrated in vivo by histomorphometric evaluation in coated versus uncoated implants. The osteointegration rates varied between 21.5% and 47.7% (cancellous bone), and between 28.0% and 56.8% (cortical bone). (p < 0.05). SEM analysis demonstrated better bone adhesion to the material in coated implant at any weeks. Coated implants are highly biocompatible and osteoconductive.