Study of human cortical bone and demineralized human cortical bone viscoelasticity

The knowledge of human bone viscoelasticity is an important issue for defin ing semirigid calcified tissues implants. A very sensitive technique was us ed to investigate bone viscoelasticity: the thermally stimulated creep meth od. A study of demineralized human bone was performed to determine the mole cular origin of bone viscoelasticity. The thermally stimulated creep spectr a of bone and demineralized bone, at the hydrated state, present a similar shape with one main retardation mode located at -133 and -120 degreesC, res pectively. This mode is shifted toward higher temperatures after dehydratio n, revealing the existence of another mode at around - 155 degreesC. The an alysis of elementary spectra of bone and demineralized bone has shown that retardation times follow an Arrhenius equation, and that two compensation p henomena are observed with comparable compensation parameters. The first co mpensation phenomenon, which corresponds to the main retardation mode, was attributed to motions of water molecules located inside the collagen triple helix. The second compensation phenomenon, which reveals the existence of another relaxation mode at higher temperatures, was assigned to movements o f hydrophilic side chains bound to water molecules. As for the mode observe d at around -155 degreesC, it was associated with motions of aliphatic side chains. Overall, bone viscoelasticity originates from the organic matrix. (C) 2001 John Wiley & Sons, Inc.