Age and temperature related changes to the ultrastructure and composition of human bone mineral

Abstract

This X-ray diffraction (XRD) investigation of heat-treated human femoral bone showed that the main mineral phase of both unheated bone and bone heated to 600 degrees C resembled that of a poorly crystalline form of hydroxyapatite. The rod-shaped apatite crystals in unheated bone persisted in bone heated up to 400 degrees C. Recrystallization at approximately 600 degrees C, produced larger crystals, which either retained their original morphology or changed to tabular or equidimensional shapes. The size of the apatite crystals in unheated and heated bone specimens was dependent on both temperature and age. When heated above 600 degrees C the crystallinity of the bone mineral increased, and the XRD pattern more closely resembled that of hydroxyapatite. Partial decomposition of the hydroxyapatite phase to calcium oxide above 1000 degrees C, and beta-tricalcium phosphate, alpha-tricalcium phosphate, and calcium oxide phosphate between 1200 degrees C and 1400 degrees C, indicated that the original apatite phase was both calcium deficient and contained carbonate. The relative peak intensities of the thermal decomposition products were related to some extent to the age of the deceased person and reflected the compositional changes that occur during bone aging. Because the thermally induced changes to the composition and ultrastructure of bone mineral were influenced by the age of the individual, this investigation proposed that the heat treatment of bone tissue may offer an alternative way of studying bone aging.