Abstract
Hydroxyapatite ceramics has been demonstrated to be an appropriate material for biomedical applications owing to its bioactivity and high biocompatibility. It has an anisotropic crystal structure that belongs to the hexagonal system, and two types of crystal planes mainly appear on its crystal, which are a-plane and c-plane. Since these two crystal planes are very different in atomic elements, numbers and arrangements, they exhibit different nature (anisotropy). For this reason, it is said that crystal orientation might be intensifying its bioactivity and biocompatibility. However, the differences in biological features on these two crystal planes are not fully clarified yet. In this study, we have conducted an assessment to reveal anisotropic biological features of hydroxyapatite by using hydroxyapatite ceramics with controlled orientation fabricated by slip casting under a magnetic field. Tanase et al. have recently reported the difference in bioactivity on the two crystal planes by immersing crystal oriented hydroxyapatite ceramics into the simulated body fluid and found that c-plane oriented hydroxyapatite ceramics formed a precipitate layer earlier and thicker on its surface compared to a-plane oriented one. We first carried out Welch’s t-test on the difference in the thickness of the precipitate layer, reported previously to reveal the difference in bioactivity. Secondly, we conducted an osteoblast culture experiment on hydroxyapatite ceramics with controlled orientation to reveal the difference in initial cell attachment and cell morphology on the two crystal planes of hydroxyapatite using optical microscope observations. In the former case, the results of the Welch’s t-test indicated that the thickness of the precipitate significantly differed on each crystal oriented hydroxyapatite ceramics (P<0.05). In the latter case, initial cell attachment seemed to be better on the a-plane oriented hydroxyapatite ceramics and also the morphology of the osteoblasts seemed to be rounded on the a-plane oriented hydroxyapatite ceramics compared to the c-plane oriented one.
