Using a polyurethane foam replica method, porous hydroxyapatite scaffolds (PHS) were fabricated using conventional and microwave sintering techniques. The microstructure and material properties of the PHS, such as pore size, grain size, relative density and compressive strength, were investigated at different sintering temperatures and holding times to determine the optimal sintering conditions. There were interconnected pores whose sizes ranged between about 300 μm and 700 μm. At a conventional sintering temperature of 1100˚C, the scaffold had a porous microstructure, which became denser and saw the occurrence of grain growth when the temperature was increased up to 1300˚C. In the case of microwave sintering, even at low sintering temperature and short holding time the microstructure was much denser and had smaller grains. As the holding time of the microwave sintering was increased, higher densification was observed and also the relative density and compressive strength increased. The compressive strength values of PHS were 2.3MPa and 1.8MPa when conventional and microwave sintering was applied at 1300˚C, respectively.

Nano-crystalline hydroxyapatite (HAp) films were formed at the Ti surface by a single-step microarc oxidation (MAO), and HAp-zirconia composite (HZC) films were obtained by subsequent chemical vapor deposition (CVD) of zirconia onto the HAp. Through the CVD process, zero- and one-dimensional zirconia nanostructures having tetragonal crystallinity (t-ZrO2) were uniformly distributed and well incorporated into the HAp crystal matrix to form nanoscale composites. In particular, (t-ZrO2) was synthesized at a very low temperature. The HZC films did not show secondary phases such as tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP) at relatively high temperatures. The most likely mechanism for the formation of the t-ZrO2 and the pure HAp at the low processing temperature was proposed to be the diffusion of Ca2+ ions. The HZC films showed increasing micro-Vickers hardness values with increases in the t-ZrO2 content. The morphological features and phase compositions of the HZC films showed strong dependence on the time and temperature of the CVD process. Furthermore, they showed enhanced cell proliferation compared to the TiO2 and HAp films most likely due to the surface structure change.

It is necessary to improve the esthetic and function in the patient with oral and maxillofacial bone defects. Synthetic bone substitute materials and anorganic bovine bone mineral(ABBM) have been used for clinical restoration. The purpose of this study was to observe the biocompatibility and bone formation of synthetic hydroxyapatite(SHA) and ABBM in hole of rabbit's tibia. After specimens with SHA and ABBM at 8 weeks were fixed in 10% neutral formalin solution, dehydrated, and embedded with spurr low viscosity, they were cut by 500um with slow diamond wheel saw and grinded up to 200um in thickness. These specimens were coated with carbon and examined with r efraction microscope for bone density. Refraction microscopic features of 8 weeks in synthetic HA showed network-like new bone forming trabecular pattern attached to resorbed HA. Less well calcified trabecular bone surrounding conglomerated HAs showed irregular arrangement of numerous osteocytes. There was not completely filled in defected area by new bone trabecular. New trabecular bone formation by ABBM was more prominent and completely compacted in defect hole at 8 weeks. It suggested that although bone formation activity of AMMB might be superior to that on synthetic HA, both group would be the good biocompatibility in this experiment.

In this study, hydroxyapatite (HAp) and hydroxyapatite-yttria stabilized zirconia (HAp-3YSZ) with 20 vol. %– (ZrO2+3 %mol Y2O3) nanopowders were consolidated very rapidly to full density by High-frequency induction heat sintering (HFIHS). Effects of temperature and the addition of 3YSZ on the toughness, hardness and microstructure properties have been studied. 3YSZ second phase toughening HAp composites with higher toughness were successfully developed at relatively low temperatures through this technique. Compared with hardness and toughness obtained for pure HAp, the hardness and toughness for HAp-20vol. % 3YSZ were much higher.

The process of coprecipitation of biocomposite hydroxyapatite/chitosan from aqueous solution at low temperature in alkali environnement was examined. We have shown that initially we have the formation of amorphous octocalcium phosphates and the transferring from OCP to amorphous calcium phosphate , and then from TCP to calcium-deficient hydroxyapatite and hydroxyapatite . The transformation of ACP to HAP was inhibited in the presence of chitosan. The result suggests that there is an affinity binding between ACP and chitosan and subsequently blocking the active growth site of ACP.

In the present study, silver-doped antibacterial hydroxyapatites were successfully prepared by the sol-gel method. For the starting solution, the molar ratio of was set to 0.075:0.045:20:0.135; was added to a ratio of Ag to total cation concentration of . The prepared sol was dried at for 48h and heat-treated at for 2h to obtain particles in the 200-500nm size range. The product from the synthesis of silver-doped hydroxyapatite was investigated through X-ray diffraction experiments and scanning electron microscopy. The product showed high antibacterial properties, with a disinfection ratio of Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 25922) over as calculated from an antimicrobial effects evaluation by the shake flask method.