Different behavior of implanted hydroxyapatite depending on morphology, size and crystallinity

Hydroxyapatite (HAp) materials with different morphology, size and crystallinity were prepared and were implanted into a male rat tibia. Each of the HAp materials showed a high biocompatiblity and osteoconductivity. The morphology and size of the implanted HAp affected the intrusion of bone marrow derived cells among HAp materials, and this cell intrusion was important for regulating the newly formed bone mass. High crystalline sintered HAp was stable and remained in its initial shape for long periods. However, low crystalline HAp was absorbed and disappeared during bone remodeling. This study indicates that choosing suitable HAp materials in morphology, size and crystallinity is important for a treatment plan (e.g. reconstruction or regeneration; large region or small region etc.) and for achieving a desired prognosis.