Biomedical Engineering Reference
In-Depth Information
40
P
Ca
30
20
10
0
Head
Tail
Edge
Fig. 5.10
Detection of Ca/P ratio on the various positions of the enamel rod
Fig. 5.11
Schematic diagram of force analysis in the occlusal cross section of a single enamel rod
during the nanoindentation process
One possible reason could be explained by the arrangement of the internal
hydroxyapatite crystals in an enamel rod. As mentioned above, human tooth enamel
is composed of hierarchical structures. Hydroxyapatite crystals are the fundamental
hierarchical structure level, which assemble into nanofibrils and fibers level by
level. Finally, the fibers assemble into an enamel rod through a unique arrangement.
The ideal hydroxyapatite crystal fiber arrangement in an enamel rod is shown in
Fig.
5.11
[
4
]. In the center of the head area, the fibers are aligned parallel to the rod
