Analysis of hydroxyapatite (HAp) texture in regenerated hard tissues using micro-beam X-ray diffractometer technique

摘要

Preferential orientations of hydroxyapatite (HAp) crystallites in various biological normal and regenerated hard tissues were analyzed by the micro-beam X-ray diffractometer (XRD) with a beam spot of 100 |xra in diameter. HAp texture differs in the normal hard tissues with the different shapes under various stress conditions in vivo. Predominant alignment of the c-axis in HAp was observed as one orientation along the longitudinal axis in a rabbit ulna and as two-dimensional orientation in a rabbit skull along the surface. The alignment in a monkey dentulous mandible orients basically along the longitudinal direction in the flat bone, but the c-axis changes to preferentially align near the tooth along the normal direction to the flat bone surface parallel to the biting direction due to force of mastication. Regenerating processes of defect introduced artificially in the rabbit ulna and skull were also monitored by the micro-beam XRD technique. Regeneration at the bone defect was induced by a biodegradable gelatin hydrogel incorporating basic fibroblast growth factor with a water content of 85 wt%. The new bone was predominantly formed near the residual periosteum on the neighboring radius and the alignment of the c-axis in HAp showed a tendency to recover to that in the original bone, while the perfect recovery was not achieved in the ulna with the defect regenerated for 4 weeks and in the skull for 12 weeks. It was concluded that the micro-scale measurement of HAp texture is one of the useful new methods to evaluate extent of regeneration in hard tissues.