Scientific Articles of Hydroxyapatite (HAP):
Limeback L, Enax J, Meyer F. (2021). Biomimetic hydroxyapatite and caries prevention: a systematic review and meta-analysis.
Human tooth enamel is composed of hydroxyapatite (HAP) crystals (96–98% based on tooth mass). The crystals are organized into enamel prisms, which you can see in the middle of Figure 1.
Figure 1. Schematic illustrations of the hierarchical structure of giant panda’s tooth enamel (Weng et al; 2016)
Enamel prisms are formed from rods with HAP fibers inside. These fibers are 2800x smaller than the diameter of a normal hair!