Physiochemical modifications to bone mineral

Bone is a complex composite material consisting of three main components: a mineral phase structurally similar to calcium hydroxyapatite (HAp), an organic matrix containing collagenous and non-collagenous proteins and, water. The complexity of bone has led to an abundance of literature across a wide range of disciplines, which have endeavoured to provide a greater understanding of this material. In particular, heated bone studies are prevalent in biomedicine where heat treatment is often used to sterilise bone material required for xeno– and allo- grafts, in forensic science where species differentiation of unknown heated bone specimens would prove invaluable and in archaeology, where heated bone material often provides information about the cooking and funeral practices of our ancestors. Unfortunately, many of these studies are largely observational and some of the processes and mechanisms associated with heated bone are largely assumed and in some instances ambiguous. Over 1000 biological and synthetic HAp specimens were utilised during this research to investigate the fundamental processes and mechanisms associated with unheated and heated bone. In particular, three controversial areas of bone research were considered: - in vivo HAp crystal size control, the relationship between the organic and mineral components of bone during heat treatment and the confounding effects of cooling on bone mineral during heat treatment. This was achieved by considering the chemical composition of unheated biological and synthetic HAp specimens, and heated bone specimens from various species including human. The results of this thesis demonstrate that an intrinsic rather than extrinsic source may be responsible for in vivo biological HAp crystal size control, a concept which has not previously be considered. The results have also shown bone mineral crystallisation during heat treatment is promoted by the organic matrix and, cooling has an impact on both crystallisation and thermal decomposition of HAp during heat treatment. This research has also questioned the use of current X-ray diffraction (XRD) refinement techniques with nanocrystalline materials such as bone, to determine crystalline size and strain. Further interpretation of the results questioned whether heated bone data is comparable between research groups, whether it was possible to create a time and temperature predictive model for heated bone and whether human bone is statistically different from other bone types when dynamically heated. Due to the fundamental nature of this research, it is expected the results will have an impact across a wide range of disciplines including biomedicine, forensic science and archaeology.