Ultrastructure of ceramic-bone interface using hydroxyapatite and β-tricalcium phosphate ceramics and replacement mechanism of β-tricalcium phosphate in bone

Abstract

Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) are useful for grafting and augmentation of bone tissue. Observation by transmission electron microscopy (TEM) was done to investigate the ultrastructures at the interfaces between the biomaterials and the adjacent tissue, and osteogenesis around the biomaterials in the present study. HA and β-TCP ceramics were used in disk forms which had macropores and micropores, and were implanted between the parietal bone and the cranial periosteum of rats. Specimens were prepared for observation at 4 and 8 weeks postoperatively. The microscopic results indicated that an intervening layer was present on the surface of HA, whereas it was not present on the surface of β-TCP. A characteristic fibrillar structure was observed in the intervening layer between HA and bone under decalcification by HCl. In β-TCP, in reticular structures observed close to the bone tissue by optical microscopy, calcification and sparse collagen fibers were interspersed among the granules of β-TCP. In addition, close to the interface between β-TCP and bone, many osteocytes with numerous processes were present. Some processes were elongated towards the interface. These results revealed the difference in the ultrastructures of the interfaces between HA and β-TCP, and the dissolution mechanism of β-TCP in bone.