Biomaterials 24 (2003) 5091–5097 Bone mineral change during experimental heating: an X-ray scattering investigation J.C. Hiller a, *, T.J.U. Thompson b , M.P. Evison b , A.T. Chamberlain c , T.J. Wess a a Department of Optometry and Vision Sciences, Biophysics Group, University of Cardiff, Redwood Building, Cathays Park, Cardiff CF10 3NB, UK b Department of Forensic Pathology, The Medico-Legal Centre, University of Sheffield, Watery Street, Sheffield S3 7ES, UK c Department of Archaeology, University of Sheffield, Northgate House, West Street, Sheffield S1 4ET, UK Received 3 December 2002; accepted 30 May 2003 Abstract The effects of heating and burning on bone mineral have previously been studied using techniques such as X-ray diffraction (XRD) with the aim of discerning a characteristic signature of crystal change. This would enable a better understanding of alteration to bone mineral during heating, which would in turn impact on the preparation and use of natural bone hydroxyapatite as a biomaterial resource. In addition, this knowledge could prove invaluable in the investigation of burned human remains from forensic and archaeological contexts in cremation and funerary practice. Here we describe a complementary method, small-angle X-ray scattering (SAXS), to determine more accurately the changes to bone crystallite size and shape during an experimental heating regimen. Samples were subjected to controlled heating at 500  C, 700  C, or 900  C for 15 or 45 min. Our results show bone crystallites begin to alter in the first 15 min of heating to 500  C or above. They then appear to stabilise to a temperature-specific thickness and shape with prolonged heating. While the samples heated to lower temperatures or for shorter periods produce XRD traces showing little alteration to the apatite, corresponding information obtained from SAXS shows an early, subtle change in crystal parameters. r 2003 Elsevier Ltd. All rights reserved. Keywords: XRD; Microstructure; Crystal growth; Bone; Hydroxyapatite 1. Introduction Bone mineral is an important biomaterial resource. Accurate measurement of bone crystal alteration, both in structure and composition, has been a focus of biomaterial research for several years (e.g. [1–6]). Heat treatment has been used to deproteinate bone mineral for use in osteoimplantation, since natural hydroxyapa- tite with the organic matrix removed is potentially a better basis for bone grafting than synthetic materials [1]. The usefulness of this material, however, relies on the retention of biogenic crystallite characteristics throughout the preimplantation treatment process. Changes to the biogenic composition and structure of bone mineral following heat treatment at different temperatures could affect its efficacy in these proce- dures. It would be valuable to know the temperature at which crystallites begin to change, and how rapid the alteration can be. This would allow for an optimisation of the heat treatment process to maximise the removal of the organic material in bone with the minimum of disruption to the mineral. In addition, the ability to identify burning and burned bone in the forensic and archaeological records has long been an important and contentious issue. Several techniques to determine burning or heating regimen used in archaeological contexts have been derived, with varying levels of success [7–10]. Determination of the temperature and duration of burning, as well as the background noise of potential diagenetic effects [11] would shed light on cooking practices, the early use of fire, cremation as a burial rite, and other archaeological and paleoanthropological puzzles. Further, the effects of burning on bone specimens and the determination of the techniques used are crucial in the resolution of forensic cases where cremation or other fire damage to remains is present (e.g. [3,12–15]). Previously, X-ray diffraction (XRD) and Fourier- transform infrared spectroscopy (FTIR) have been used ARTICLE IN PRESS *Corresponding author. Fax: +44-1786-464-994. E-mail address: j.c.hiller@stir.ac.uk (J.C. Hiller). 0142-9612/03/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0142-9612(03)00427-7