ScienceDaily (Dec. 15, 2010) — In a study that
the authors describe as lending credence to the idiom, “by the skin of
your teeth,” scientists are reporting that the protective shield
fluoride forms on teeth is up to 100 times thinner than previously
believed. It raises questions about how this renowned cavity-fighter
really works and could lead to better ways of protecting teeth from
decay, the scientists suggest.
Their study appears in American Chemical Society’s journal Langmuir.
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Frank Müller and colleagues point out that tooth decay is a major
public health problem worldwide. In the United States alone, consumers
spend more than $50 billion each year on the treatment of cavities. The
fluoride in some toothpaste, mouthwash and municipal drinking water is
one of the most effective ways to prevent decay. Scientists long have
known that fluoride makes enamel — the hard white substance covering
the surface of teeth — more resistant to decay. Some thought that
fluoride simply changed the main mineral in enamel, hydroxyapatite, into
a more-decay resistant material called fluorapatite.
The new research found that the fluorapatite layer formed in this way
is only 6 nanometers thick. It would take almost 10,000 such layers to
span the width of a human hair. That’s at least 10 times thinner than
previous studies indicated. The scientists question whether a layer so
thin,which is quickly worn away by ordinary chewing, really can shield
teeth from decay, or whether fluoride has some other unrecognized effect
on tooth enamel. They are launching a new study in search of an answer.