title: High-resolution electron microscopy of octacalcium phosphate and its hydrolysis products.
abstract: The hydrolysis and dehydration products of synthetic octacalcium phosphate (OCP) were studied using X-ray diffraction, infrared spectroscopy, chemical analysis, and high-resolution electron microscopy (HREM). A "collapsed OCP" phase, identified by a characteristic 16.5 A reflection in its X-ray diffraction pattern, was observed when OCP was dehydrated. High resolution electron microscopy of the hydrolyzed and partially hydrolyzed reaction products also revealed local contrast features with an approximate 16.5 A periodicity. These features were consistent with a collapse of the OCP crystal structure and subsequent formation of epitaxial intergrowths of OCP and hydroxyapatite. Chemical analysis and X-ray diffraction of these samples were similar to previously reported calcium-deficient apatites. The hydrolysis of OCP to form calcium-deficient apatites is a reaction pathway which may be of importance in understanding the crystallographic changes occurring during the early stages of bone, calculus, and dental enamel formation.
mesh_terms: D001031:Apatites / Q000032:analysis*; D002118:Calcium / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis*; D003461:Crystallography; D006868:Hydrolysis; D008854:Microscopy, Electron / Q000379:methods; D010758:Phosphorus / Q000032:analysis; D013055:Spectrophotometry, Infrared; D014867:Water / Q000032:analysis; D014961:X-Ray Diffraction
chemical_list: D001031:Apatites; D002130:Calcium Phosphates; D014867:Water; C022045:octacalcium phosphate; D010758:Phosphorus; D002118:Calcium