Structure of Bones and Teeth

Fossils not only provide the geologic record of evolution, they also remind us of the crucial role that mineralized tissues play in the biology of organisms. Mineralized tissues are composite structures consisting of an inorganic mineral phase, an organic phase, and cells. In this article, I provide an overview of the mineral–matrix relationships in bones and teeth, highlight the significant differences between biologic apatites and geological hydroxylapatite, and describe the recent advances and challenges in genetic, spectroscopic, and microscopic studies of the mineralization of bones and teeth. Biologic apatites are analogues of geologic hydroxylapatite but, especially in the case of bone and dentin, differ in having highly disordered, non-stoichiometric structures with numerous point deficiencies and carbonate substitutions. We will distinguish these structures in the present text by referring to bioapatite or apatite as distinct from stoichiometric hydroxylapatite. These topics have been reviewed recently in greater detail (Glimcher 2006).