Similar results were obtained
by Glas (1962) with 3.3 wt.% fluoride for shark teeth enameloid.
In comparison, the fluoride content in the mineral in dentin
was much smaller, indicating the presence of fluorohydroxyapatite
(francolite), and also suggesting that the fluoride content in the
enameloid serves some hitherto unknown function which is not
only related to the hardness