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Teeth are
hard, and this hardness is caused by a form of calcium
called hydroxyapatite. Hydroxyapatite is the same substance
that makes bones hard. However, the bones have the added
advantage of an active blood supply, so the body has a
mechanism to remineralize any area of bone that needs
repair, while the teeth, once formed, must last a lifetime
without any active help from the body's defenses.
Hydroxyapatite is very susceptible to acid attack. The sugar
you eat is metabolized to a dilute acid in your mouth by the
germs in plaque. Hydroxyapatite is also quite susceptible to
"attack" by free fluoride ions as well, but instead
of causing destruction of the hydroxyapatite crystals, it
causes their transformation to fluoroapetite which
has most of the same characteristics as hydroxyapatite, but
is quite resistant to attack by acid. Thus, rinsing
the mouth with fluoride containing mouth washes and
toothpastes coats the outside of the teeth with a layer of
acid resistant fluoroapetite.
Additionally, fluoride, given to children during the time
the teeth are forming under the gums, actually incorporates
itself into the permanent structure of the teeth and imparts
some protection from decay for the life of the teeth
themselves. This is the reason that dentists encourage young
parents to give their children fluoride supplements (in
areas where there is none in the water supply).
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- Fluoride
promotes the "healing" of cavities: The regular use of
fluoride containing toothpastes and mouth rinses will
remineralize tooth structure which has been attacked by
acid. These areas tend to harden up and will remain that
way unless more sugar undermines the remineralized areas.
Fluoride increases the resistance of the teeth to acid
demineralization: Any tooth structure exposed to fluoride
will gain a surface molecular layer of fluoroapatite which
is resistant to acid attack.
Fluoride interferes with the function of the germs in
plaque which are responsible for turning the sugar you eat
into acid. This effect tends to last beyond the time of
brushing
Fluoride speeds up the formation of the internal structure
of the adult teeth after they have begun to erupt. When
teeth first erupt into the mouth, the nerves inside them
are very large. The nerve lays down more tooth structure
inside its own space as we get older. This has the overall
effect of strengthening the teeth since the teeth contain
more hard, mineralized material as they mature.
Fluoride given to children affects the shape of the teeth
themselves. The difference in shape is not obvious to non
dentists. The depth of the grooves in the tops of the back
teeth is reduced by fluoride. This area is where most
early decay tends to develop, and the reduction in the
depth of these grooves reduces the ability of the acid to
penetrate through the enamel into the softer dentin
underneath.
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The
downside to fluoride
There is one problem associated with fluoride. This involves
the appearance of the teeth if the child receives too much
fluoride while the teeth are forming. It is called as
Fluorosis
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