Bone Ultrastructure – Collagen-reinforced Mineral Matrix or Interpenetrating Network of Hydroxyapatite Crystals and Collagen Molecules?

C. Hellmich (Austria), J.-F. Barthélémy, and L. Dormieux (France)

Keywords

bone, hydroxyapatite, collagen, crystal foam, fibril, ho mogenization, continuum micromechanics

Abstract

We develop and verify three different continuum micromechanics representations of the collagen-mineral interaction in the elasticity of mineralized tissues: (i) mineral foam matrix with collagen inclusions [5], (ii) interpenetrating network of hydroxyapaptite crystals and collagen molecules, (iii) composite of fibrils (collagen hydroxyapatite network) embedded in a collagen-free ex trafibrillar mineral foam matrix. The most advanced con cept (iii), with the best predictive capabilities, integrates the two others into a consistent whole. There, the collagen is clearly represented as the governing element in induc ing tissues' the anisotropy, by (i) the anisotropy of molec ular collagen itself, (ii) the anisotropy of the fibrils, and (iii) the oriented morphology of the cylindrical fibrils in the isotropic extrafibrillar space.

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