The nature of calcium phosphate in mineralizing vertebrate tissues

This presentation will describe and summarize aspects of the chemical, biol ogical and physical nature of the mineral deposited in the normal vertebrat e skeletal and dental systems. Bone, calcifying cartilage and tendon, denti n, cementum and enamel mineral is a calcium phosphate, most often referred to as apatite and commonly denoted as Ca-10(PO4)(6)(OH)(2). The mineral is composed of crystals of a unique size and shape, having an unusual chemistr y including similar to 3-5% carbonate and 5-10% [HPO4] (2-), and serving as a reservoir for other cationic and anionic species. Apatite composition va ries in the type and degree of ion substitution, number of atomic vacancies , crystallinity, and age and maturation Nucleation, growth, and development of the crystals are mediated by organic matrix molecules specific for each tissue, notably collagen in all except enamel. Amelogenin protein modulate s apatite formation in part in the latter tissue. The interactions between such organic molecules and the mineral crystals are complex and not entirel y understood, but they ultimately lead to organic-inorganic composites with remarkable integrity, mechanical strength, distinct form and additional ph ysical properties that are functionally representative.