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Nanoindentation Measurements of Bone Viscoelasticity as a Function of Hydration State

Published online by Cambridge University Press:  26 February 2011

Amanpreet Kaur Bembey ,
Michelle Oyen ,
Andrew Bushby  and
Alan Boyde
Amanpreet Kaur Bembey
Affiliation:
a.k.bembey@qmul.ac.uk, Queen Mary, University of London, Materials, Mile End Road, London, n/a, E1 4NS, United Kingdom
Michelle Oyen
Affiliation:
mloyen@virginia.edu
Andrew Bushby
Affiliation:
a.j.bushby@qmul.ac.uk
Alan Boyde
Affiliation:
a.boyde@qmul.ac.uk
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Abstract

Bone is an anisotropic material, and its mechanical properties are determined by its microstructure as well as its composition. Mechanical properties of bone are a consequence of the proportions of, and the interactions between, mineral, collagen and water. Water plays an important role in maintaining the mechanical integrity of the composite, but the manner in which water interacts within the ultrastructure is unclear. Dentine being an isotropic two-dimensional structure presents a homogenous composite to examine the dehydration effects. Nanoindentation methods for determining the viscoelastic properties have recently been developed and are a subject of great interest. Here, one method based on elastic-viscoelastic correspondence for ‘ramp and hold’ creep testing (Oyen, J. Mater. Res., 2005) has been used to analyze viscoelastic behavior of polymeric and biological materials. The method of ‘ramp and hold’ allows the shear modulus at time zero to be determined from fitting of the displacement during the maximum load hold. Changes in the viscoelastic properties of bone and dentine were examined as the material was systematically dehydrated in a series of water:solvent mixes. Samples of equine dentine were sectioned and cryo-polished. Shear modulus was obtained by nanoindentation using spherical indenters with a maximum load hold of 120s. Samples were tested in different solvent concentrations sequentially, 70% ethanol to 50% ethanol, 70 % ethanol to 100% ethanol, 70% ethanol to 70% methanol to 100% methanol, and 70% ethanol to 100% acetone, after storage in each condition for 24h. By selectively removing and then replacing water from the composite, insights in to the ultrastructure of the tissue can be gained from the corresponding changes in the experimentally determined moduli, as well as an understanding of the complete reversibility of the dehydration process.

Keywords

elastic propertiesboneorganic
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 898: Symposium L – Mechanical Behavior of Biological and Biomimetic Materials , 2005 , 0898-L07-04
Copyright
Copyright © Materials Research Society 2006

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