The fact that hydroxyapatite is "converting" to bone over time, of course has major advantages as there is not a foreign implant present and therefore not the risk of the implant being the cause of problems in the future.
It has been shown that there is a 2 stage response of the body to the placement of the granular version of coralline hydroxyapatite directly on the surface of facial bone. The initial response is the ingrowth of fibrous tissue into the pores in each granule as well as between the granules. After about 2 years the persons bone grows in by a process of osteoconduction to replace the collagen. So the definitive implant is formed by the patients bone.
To place the hydroxyapatite involves surgery on the surface of the bone, to lift the bone’s membrane, and place the granules in the pocket between the bone and the periosteum. It is not injected.
According to one of the best implant surgeons in the states, HA can provide the same augmentation as implants:
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Coral hydroxyapatite if properly placed can produce the same projection as an implant. Implant placement usually requires an operation with more exposure and hence, more swelling than coral hydroxyapatite placement."
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Michael J. Yaremchukhttps://www.realself.com/question/nyc-coral-hydroxyapatite-cheekbone-augmentation