Synthesis of hydroxyapatite films on porous Al2O3 substrate for hard tissue prosthetics

Biocompatibility and bioactivity enhancement of Ce stabilized ZrO(2) doped HA coatings by controlled porosity change of Al(2) O(3) substrates

Al(2) O(3) substrates with controlled porosity were manufactured from nanosized powders obtained by plasma processing. It was observed that when increasing the sintering temperature the overall porosity was decreasing, but the pores got larger. In a second step, Ce stabilized ZrO(2) doped hydroxyapatite coatings were pulsed laser deposited onto the Al(2) O(3) substrates. It was shown that the surface morphology, consisting of aggregates and particulates in micrometric range, was altered by the substrate porosity and interface properties, respectively. TEM studies evidenced that Ce stabilized ZrO(2) doped HA particulates ranged from 10 to 50 nm, strongly depending on the Al(2) O(3) porosity. The coatings consisted of HA nanocrystals embedded in an amorphous matrix quite similar to the bone structure. These findings were congruent with the increased biocompatibility and bioactivity of these layers confirmed by enhanced growing and proliferation of human mesenchymal stem cells.

The fabrication and biochemical evaluation of alumina reinforced calcium phosphate porous implants

Alumina reinforced calcium phosphate porous implants were manufactured to improve the mechanical strength while maintaining the bioactivity of calcium phosphate ceramics. The alumina porous bodies, which provided the mechanical strength, were fabricated by a polyurethane sponge method and multiple coating techniques resulted in the porous bodies with a 90-75% porosity and a compressive strength of up to approximately 6MPa. The coating of hydroxyapatite (HAp) or tricalcium phosphate (beta-TCP) was performed by dipping the alumina porous bodies into calcium phosphate ceramic slurries and sintering the specimens. The fairly strong bonding between the HAp or TCP coating layer and the alumina substrate was obtained by repeating the coating and sintering processes. The biochemical evaluations of the porous implants were conducted by in vitro and in vivo tests. For in vitro test, the implants were immersed in Ringer's solution and the release of Ca and P ions were detected and compared with those of calcium phosphate powders. For in vivo test, the porous bodies were implanted into mixed breed dogs and bone mineral density measurements and histological studies were conducted. The alumina reinforced HAp porous implants had a higher strength than the HAp porous implants and exhibited a similar bioactivity and osteoconduction property to the HAp porous implants.