Effect of mineral dissolution from bone specimens on the viscoelastic properties of cortical bone.

Although physiological saline (0.15M NaCl aqueous solution) has been used as a storage solution to prevent bone specimens from drying, there have been reports that Ca(2+) ions dissolve from bone specimens during the storage in saline. In order to determine whether such storage has a marked effect on mechanical properties, the relaxation modulus of bovine cortical bone stored in physiological saline was compared with that stored in a buffer solution containing a sufficient amount of Ca(2+) ions. After storage in saline, the modulus value of specimens was significantly reduced from that before storage. On the other hand, the modulus value of specimens soaked in the solution containing sufficient Ca(2+) ions did not change after storage. The relaxation rate of a bone specimen stored in physiological saline was larger than that of a specimen stored in Ca(2+)-buffered saline solution and that of the control specimens. The results suggest that by the dissolution of Ca(2+) ions from a bone specimen during storage in physiological saline, percolated paths of mineral phase and of reinforced matrix phase are disjoined, resulting in reduction in the elastic modulus and change in the viscoelastic properties of bone.