Structural and Tissue Reaction Properties of Novel Hydroxyapatite Ceramics with Unidirectional Pores

Abstract

Porous ceramics of hydroxyapatite was fabricated utilizing the crystal growth of thin ice columns parallel to one another in gelatin gel containing hydroxyapatite nanoparticles. The obtained ceramics possessed unidirectional pore channels with a porosity of around 75% and showed compressive strength of up to 13.1 MPa. As control materials, porous hydroxyapatite ceramics with a directionless pore structure were also fabricated by isotropic freezing and compared with the unidirectional samples regarding compressive strength and tissue reaction in vivo. Although the porosity and pore size distribution were similar, the compressive strength and new bone formation ability of the unidirectional samples were significantly greater than those of the random structured porous ceramics.

Biomaterials by freeze casting

“…The terminal sedimentation velocity of such a particle is 4.4 mm s −1 . Diameters of hydroxyapatite particles used in freeze casting are typically much smaller than this, ranging from 100 nm to 2 mm (Lee & Shin 2007;Moritz & Richter 2007;Suetsugu et al 2007;Yoon et al 2007;Deville 2008). They are thus in the laminar-flow regime, and their sedimentation velocities range from 26 nm s −1 to 11 mm s −1 , respectively.…”

Potential Bone Replacement Materials Prepared by Two Methods

“…Fu et al reported that cellular, as opposed to lamellar, pore architectures were much better at supporting the proliferation of pre-osteoblastic cells in vitro [22]. However, in a parallel study, Fu et al determined that lamellar architectures yield higher compressive strength than cellular structures of similar overall porosity [24]. This suggests that, although the cellular-type architecture of the sintered cancellous scaffolds (Figure 6a) may be better suited for cell proliferation and potential bone ingrowth, the lamellar-type freeze-casted scaffolds (Figure 6b) are better suited for potential load-bearing applications requiring higher compressive strength and stiffness.…”

“…water), is directionally frozen in a mold, then sublimated to remove the frozen liquid phase and sintered to densify the porous ceramics [16]. Several research groups have developed varying techniques for freeze-casting biocompatible ceramics, such as HA, for potential tissue engineering applications [17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Bone Augmentation Using Novel Unidirectional Porous Hydroxyapatite with Bone Morphogenetic Protein-2 on Rat Skull

“…Previously, Iwasashi et al reported good osteogenesis after implantation of UDPHAp in tibial cortical bone defects of rabbits and dogs [2][3][4] . In the result section, we speculate whether UDPHAp would be suitable for the treatment of alveolar bone augmentation by the onlay graft with rhBMP-2.…”

“…Furthermore, it possesses good osteoconductivity, as shown by its implantation in the femoral intramedullary cavity and in the tibial cortical defect in a rabbit [2][3][4] . One of the important points in clinical use of biomaterials is that they must be not only biocompatible but also stable immediately after they are implanted.…”