Atomic force microscopy and indentation force measurement of bone.

This review is summarizing the results obtained from atomic force microscopy (AFM) and nanoindentation experiments to date. The combination of both techniques is especially powerful. It allows to carefully choose indentation locations as well as the post-hoc analysis of the created indents, and hence the possibility to assess the properties of microstructural elements of bonessue. In addition, AFM has improved our understanding of bone ultrastructure and force spectroscopy experiments have led to the discovery of a molecular self-healing effect of bone that may be based on a small fraction of unstructured proteins. Nanoindentation measurements on bone, pose inherent problems since bone is an anisotropic solid showing elastic, viscoelastic, and time-dependent plastic behavior. Hence, derived parameters such as elastic modulus and hardness are to some extent dependent on measurement protocols. However, the development of extensions to the Oliver-Pharr method, being the most widely used analysis method, as well as novel dynamic testing techniques could improve the situation. Nanoindentation is widely used to study bone tissue and some important principal findings have been reported to date. These are presented here together with specific results from nanoindentation experiments of human and animal bones and tables are presented collating the data that can be found in the literature to date.