Dielectric properties of bone and its main mineral component

Thermally Stimulated Current (TSC) and Dielectric Spectroscopy (DS) have been applied to the analysis of the complex polarization phenomena in human cortical bone and mineral extracted from human cortical bone. To precise the organic or inorganic origin of higher temperature bone dielectric relaxations, the TSC relaxation modes of bone can be compared with corresponding mineral ones. But, if the first relaxation mode observed at 40°C can be easily attributed to intermolecular movements of the organic matrix, the second peak around 85°C can be associated either with mineral or organic matrix response. Fortunately, the analysis of the mineral fine structure shows that elementary processes are characterized by relaxation times following a compensation law. As the compensation temperature occurs in the same temperature range than the main dielectric loss peak, this TSC mode has been ascribed to molecular movements inside apatitic channels. Complementary mineral study by dielectric spectroscopy confirms the existence of this dielectric loss peak in the mineral. Moreover, the dielectric DS relaxation peaks position is in good agreement with the simulated dielectric energy losses deduced from the TSC fine structure analysis. TSC and DS spectrometry are well suited to analyse complex natural composites like bone