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How to kill tooth decay without
a drill
A LASER wand could replace the dentist's drill
if clinical trials beginning next year are successful. The key is photodynamic
therapy (PDT),
in which light activates a killer molecule that wipes out bacteria in
decaying teeth.
In tests on extracted teeth, Mike Wilson and his
team at the Eastman Dental Institute in London have shown that PDT sterilises
the infected tooth tissue. Once
teeth in people's mouths are clear of infection, their bone tissue should
be able to regenerate itself.
The team also hopes PDT could help combat other
infections, particularly the hospital "superbugs" that are resistant
to antibiotics. The team has already tested PDT against MRSA, a virulent
superbug. "We wiped out over 99.9 per cent of the colony in samples
where human tissue was present," Wilson told the BA meeting.
To treat cavities, dentists drill the parts of the
tooth infected with decay-causing bacteria, leaving only healthy tissue.
"Most dentists are overcautious and drill
away a large part of the tooth," says Wilson.
PDT uses a photosensitiser molecule which binds
only to the bacteria. When the photosensitiser is bathed in laser light,
it releases oxygen radicals that kill the bacteria by punching holes in
them.
Wilson says he has disinfected extracted teeth using
a photosensitiser called toluidine blue. He will begin clinical trials
in people with cavities next year.
The researchers don't think bacteria will become
resistant to PDT. "So far, we haven't found any one site the photosensitiser
is binding to," explains Mark Wainwright of the University of Central
Lancashire, who is also working on PDT. "It just seems to adhere
generally around the cell walls." He says the bacteria would have
to change several aspects of their structure to become resistant.
From New
Scientist magazine, 16 September 2000.
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