An X-ray study of the paracrystalline nature of bone apatite

Abstract

X-ray diffraction from oriented bone sections show that the crystalline apatite content of untreated mature cortical bovine bone has, in fact, a paracrystalline structure (i.e., no long range order). There is anisotropy in both lattice distortions and the sizes of the coherently diffracting domains. The paracrystalline mean distance fluctuations (g) were found to be 1.5 (+/- 0.1)% and 2.9 (+/- 0.2)% for the basal and prism planes respectively, the corresponding paracrystalline sizes being 220 (+/- 20) and 70 (+/- 10) A. The paracrystalline structure became more ordered above 600 degrees C, suggesting the association of hydroxyl and possibly carbonate and other ions with the paracrystalline structure. The paracrystalline model for bone apatite helps explain anomalies between X-ray and electron microscope measurements of crystal size and also more of the biological functions of the crystalline apatite.

Preparation of porous apatite granules from calcium phosphate cement

“…''Biological'' or ''bone-like'' apatite, which constitutes the bone mineral, is known to be a carbonated (4-10 wt.%), poorly crystallized, alkali (i.e., Na and K) and alkaline earth (Mg) element-doped, non-stoichiometric, calcium-deficient apatitic phosphate with a Ca/P molar ratio variable over the range of 1.50-1.70 [67][68][69]. The CaP cement used in the production of the porous granules of this study was previously shown to yield a fast deposition of new bone at the cement surface in its paste form [70].…”

The 2θ determination of diffraction peaks from `poor' powder samples. Application to biological apatite

“…However, the very high cost in time causes us to reject this method. Moreover, as not all coefficients are computed in the FFT, the integral breadth (Wagner, 1966;Wheeler & Lewis, 1977) is not computed. The width of the peaks is merely an experimental estimate and the variance (Moriwaki, Ida & Ymaga, 1975) cannot be directly deduced.…”

Cartilage Calcification

“…Third, the crystalline organization is questionable, because, in our experience, and in agreement with results previously reported in bone (Landis & Glimcher, 1978), the early deposits of inorganic substance formed in epiphyseal cartilage fail to generate any electron diffraction patterns of the specific calcium phosphate solid phase, which are, in fact, only produced by the more calcified regions, whose reflections, in any case, remain those of poorly crystalline hydroxyapatite. According to Wheeler and Lewis (1977) and Arnold et al (2001), the structures that form the early calcified deposits in bone are apatitic, but their crystal lattice contains so many distortions that they come to be intermediate between amorphous and crystalline; i.e., they have a paracrystalline character comparable with biopolymers. Fourth, the question is complicated by the possibility that amorphous calcium phosphate precedes the formation of the crystalline phase (Nudelman et al, 2010).…”