Shark Tooth Hunting

The teeth of sharks are not attached to the jaw, but embedded
in the flesh, and in many species are constantly replaced
throughout the shark's life. When they lose a working tooth it
will be replaced by the next tooth behind it. All sharks have
multiple rows of teeth along the edges of their upper and lower
jaws. New teeth grow continuously in a groove just inside the
mouth and move forward from inside the mouth on a "conveyor
belt" formed by the skin in which they are anchored. Typically
a shark has two to three working rows of teeth with 20 to 30
teeth in each row, although a whale shark has about 300 teeth
in each row. The replacement rate has not been measured in
most sharks but normally the teeth seem to be replaced every
two weeks. The lemon shark replaces its teeth every 8–10
days, and the great white shark replaces its teeth about every
100 days for young sharks and about every 230 days for old
sharks. Most sharks shed individual teeth, but the cookie-cutter
shark sheds the whole lower jaw at once. The shape of a shark's
tooth depends on its diet; those that feed on mollusks and
crustaceans have dense flattened teeth for crushing, those that
feed on fish have needle-like teeth for gripping, and those that
feed on larger prey such as mammals have pointed lower teeth
for gripping and triangular upper teeth with serrated edges for
cutting. The teeth of plankton-feeders such as the basking shark
are greatly reduced and non-functional