Amorphous structures represent about 20% of the 60 or so different mineral types formed by the action of living organisms. Among these biogenic amorphous minerals, those that are composed principally of calcium and phosphate are most abundant in the teeth and exoskeletal structures of marine invertebrates. The existence of similar amorphous calcium phosphate (ACP) minerals in vertebrate organisms, on the other hand, has not been well established experimentally. In particular, the evidence for ACP as an integral mineral component in major hard tissues such as bone, cartilage, and dentin remains equivocal and the subject of considerable debate. Because physical and morphological evidence for ACP in skeletal tissue has been difficult to establish directly, much of our progress in clarifying the possible role ACP may play in biogenic calcification has come from synthetic and in vitro studies. This chapter will cover the salient structural, morphological, and chemical features of synthetic ACP and the insight these features provide in the development of a proper assessment of the presence and role of ACP in vivo. In keeping with the theme of this monograph, special attention will be given to the relationship of OCP to ACP.
Amorphous Calcium Phosphate
Octacalcium Phosphate Chapter in book, Octacalcium Phosphate, L.C. Chow, editor,