Scanning and transmission electron microscopy of calcified tissues

Some recent innovations have been utilized to extend studies of the structure of calcified tissues on the ultra- and microstructural levels of organization. The introduction of hydrazine as a replacement for the conventionally used ethylene diamine to deproteinize calcified tissue samples has resulted in the acquisition of previously unobtainable information about the mineral phase as it exists in situ. This enables inference of mineral-organic interrelationships when coupled with the EDTA demineralization technique used to study collagen fiber frameworks. In addition, a method for obtaining whole single osteons and separating them into lamellar constituents permits observations of the collagen-apatite orientation within successive lamellae of compact Haversian bone. The use of the structural information derived to develop a fiber-reinforced model of compact bone as a composite material is outlined and discussed.