Haversian bone

Of the many structural types of bone, only the lamellar , plexiform bone in the diaphysis compacta of long bones is of importance for fluorine dating, because only this material is homogeneous enough for the development of a dominant profile that starts from the periosteal surface. Especially in haversian bone (e.g. human bone), profiles may be forming at a number of points in the bone and in a number of different directions, stemming from surfaces within the bone (e.g. Haversian canals) or from the medullary cavity. These profiles often hide the true... 

The reason to extend the experiments to tooth material was the idea that the matrix would have a less porous structure compared to human haversian bone and be less exposed to diagenetic alteration. While the porosity in human bone is mainly determined by a complicated network between the Haversian system and the Volk-mann canals that are perpendicular to it, especially enamel is a far denser material than human bone and its organic content is significantly less (2% of organic material only). But in contrast to the enamel, dentine has a similar composition of the organic and the inorganic matrix compared to bone, and it has a high microporosity due to nerve canals that start from the pulpa and stop close to the enamel-dentine junction (edj). However, these nerve canals have a smaller diameter than a haversian pore (70 pm) and the canals are orientated parallel and are not connected with each other. So a fluorine ion cannot percolate from one pore to another, as it is the case in a human bone, but it has to overcome the distance from one canal to the next one by diffusion. So the permeability is low and this results in a smaller diffusion rate D. 

Figure 23 Mammalian bone at different levels of resolution (a) Collagen fibril with associated mineral, (b) Woven bone (random collagen distribution), (c) Lamellar bone showing separate lamellae with collagen organized in domains with preferred orientation alternating in adjacent lamellae, (d) Woven bone with blood channels shown as dark spots, woven bone stippled, (e) Primary lamellar bone orientation indicated by dashes, (f) Haversian bone, a collection of haversian systems are shown as a longitudinal structure. Each system has concentric lamellae around a central blood channel. Darkened area represents an empty (eroded) portion of the section which will be reconstituted with new bone, (g) Alternation of woven and lamellar bone, (h) Various orientations of heavily mineralized (cortical, or compact) bone, (i) Trabecular, or cancellous, bone (Wainwright et aL, 1976) (reproduced by permission of Hodder Arnold from Mechanical Design in Organisms, 1976).

Anderson C, Danylchuk KD. 1979. The effect of chronic excess zinc administration on the haversian bone remodelling system and its possible relationship to "Itai-ltai" disease. Environ Res 20 351-357. 

This technique was used successfully to show that bovine plexiform bone was definitely orthotropic while bovine haversian bone could be treated as transversely isotropic [Lipson and Katz, 1984]. The results were subsequently confirmed using bulk wave propagation techniques with considerable redundancy [Maharidge, 1984]. 

Table 47.2 lists the Qj (in GPa) for human (haversian) bone and bovine (both haversian and plexiform) bone. With the exception of Knefs [1978] measurements, which were made using quasi-static mechanical testing, aH the other measurements were made using bulk ultrasonic wave propagation. 

FIGURE 47.3 Diagram showing how laminar (plexiform) bone (a) differs more between radial and tangential directions R and T) than does haversian bone (b). The arrows are vectors representing the various directions [Wainwright et al., 1982] (Courtesy Princeton University Press). 

It is interesting to note that haversian bones, whether human or bovine, have both their compressive and shear anisotropy factors considerably lower than the respective values for plexiform bone. Thus, not only is plexiform bone both stiffer and more rigid than haversian bone, it is also more anisotropic. These two scalar anisotropy quantities also provide a means of assessing whether there is the possibility either of systematic errors in the measurements or artifacts in the modeling of the elastic properties of hard tissues. This is determined when the values of Ac (%) and/or As (%) are much greater than the close range of lower values obtained by calculations on a variety of different ultrasonic measurements (Table 47.5). A possible example of this is the value of As (%) = 7.88 calculated from the mechanical testing data of Knets [1978], Table 47.2. 

Haversian bone Also called osteonic. The form of bone found in adult humans and mature mammals, consisting mainly of concentric lamellar structures, surrounding a central canal called the haversian canal, plus lamellar remnants of older haversian systems (osteons) called interstitial lamellae. 

Katz J.L. 1976. Hierarchical modeling of compact haversian bone as a fiber reinforced material. In R.E. Mates, and C.R. Smith (Eds), Advances in Bioengineering, pp. 17-18. New York, American Society of Mechanical Engineers. 

Katz J.L. and Ukraincik K. 1972. A fiber-reinforced model for compact haversian bone. Program and Abstracts of the 16th Annual Meeting of the Biophysical Society, 28a FPM-Cl 5, Toronto. 

Pfretzschner, H. U. (2004). Fossilization of Haversian bone in aquatic environments. Comptes Rendus Palevoly 5, 605-616. 

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