The purpose of this study was to evaluate four commercial apatite products. Subperiosteal alveolar ridge augmentation was performed on the maxilla of rats by implantation of granules of two dense products and of two porous products, and the tissue response was compared with the material characteristics obtained by chemical analysis and infrared spectrometry. None of the apatites caused osteoinduction or osteoconduction; fibrous encapsulation with multinuclear giant cells was observed around all four types. One of the apatites was fluorapatite and not hydroxylapatite, as claimed by the manufacturer. The tissue response to this implant material was dominated by multinuclear giant cells.

Chemical, physical, and histologic studies on four commercial apatites used for alveolar ridge augmentation.
Pinholt EM, Ruyter IE, Haanaes HR, Bang G.
J Oral Maxillofac Surg. 1992 Aug; 50(8): 859-867; discussion 867-868