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Polymers used in Dentistry - White Fillings - Polymer Composite.
Polymers are used in dentistry to make white fillings for teeth.
What are Teeth made from?
Teeth
are mainly made from hydroxyapatite
(sometimes
called hydroxylapatite), which is
a type of calcium
phosphate
with the formula
Ca10(PO4)6(OH)2. The outside layer
of teeth, called
enamel, contains over
90% hydroxyapatite.
Enamel is the hardest substance in the human body.
Why are Fillings needed?
Bacteria which live in the mouth produce acid in the presence
of
starch
and sugar. The acid can cause small
holes to form in
the tooth's enamel.
Eventually these holes become
big enough
to reach the nerve inside the tooth and it becomes painful.
A dentist can fill these
holes
before they reach the nerve to prevent further decay.
What is an Amalgam?
For many years teeth have been
filled with a mixture of metals
called an amalgam. Amalgam means an alloy of mercury.
The
amalgam used for fillings contains
mercury, silver and
other
metals.
The amalgam is strong enough to
withstand the pressures put on the
back teeth (called molars)
during crunching and chewing. It has the disadvantage
that it looks
like dark silver and is a good
conductor
of
heat which can make eating hot or cold things
unpleasant.
What is a Polymer Composite?
More recently dentists have used a
white composite
for filling teeth.
A composite is a substance made
by combining two or more materials.
White fillings
are a composite of a
polymer filled with glass.
The filling is put on the tooth in the form of a paste
and then a beam of ultraviolet (uv)
light is shone
on it. The uv
light initiates (starts)
chemical reactions
in the paste which
form a number of cross links
between the polymer chains. The polymer
containing
the glass filler becomes a
solid three dimensional
cross linked network which fills the hole in the
tooth.
Links Polymers Revision Questions
gcsescience.com The Periodic Table Index Polymers Quiz gcsescience.com
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