- © The Mineralogical Society Of America
Calcium phosphate is the dominant solid mineral phase within the skeletal and dental tissues of vertebrates. This chapter concentrates on the structure and composition of the solid calcium inorganic orthophosphate (Ca–Pi) phase in bone and the mechanisms that are thought to induce the onset of this mineralization process as an example of biological mineralization in general. It is important to recognize that the Ca–Pi mineral phase is deposited in a living tissue and is a substance that is continuously being synthesized, resorbed and replaced by the action of living cells. Therefore, the composition, structure and other properties of the solid Ca–Pi mineral phase will change in space and time, depending on the general body metabolism and the local cellular functions in specific regions of bone. Similar considerations arise in studies of the mineralized tissues of invertebrates, where the crystals consist of various lattice arrangements of CaCO3 (calcite, aragonite, vaterite) deposited in hierarchical arrangement with the constituents of the ordered organic matrices. Furthermore, the nature of the Ca–Pi phase in bone is significantly different from synthetic, highly crystallized and geological hydroxylapatites, which is reflected in the physical, structural properties and physiological functions of the biological apatites.
This chapter is an attempt to summarize at least some of the historical background leading to the more recent research over the past several decades. The focus here is on investigations at the molecular and nano-scales, now possible both theoretically and experimentally, which have been applied to determine the “nature” of the solid Ca–Pi mineral phase of bone and other calcified vertebrate tissues from the inception of mineralization to the changes that occur during crystal maturation (“crystal aging”) and the “normal” aging of the animal. The topics addressed below include an introduction to the basic concepts, relevant terminology and cellular events involved in bone …