Scientists at The Forsyth Institute have found that blue light can be
used to selectively suppress certain bacteria commonly associated with
destructive gum disease:

   The research, published in the April Journal of Antimicrobial
Agents and Chemotherapy, suggests that light in the blue region of the
visible spectrum might be useful in preventing, controlling or treating
periodontitis -- an oral infection that can lead to loss of bone and
teeth.

   "Some of the key bacterial pathogens associated with periodontitis
produce and accumulate compounds that are sensitive to light," said
Nikos Soukos, DDS PhD, Director of the Forsyth Laboratory of Applied
Molecular Photomedicine and the principal investigator. "We found that,
when exposed to particular wavelengths of light, a percentage of those
pathogens was eradicated within seconds."

   Another important finding was that when the proportion of such
pathogens was reduced, the proportion of other, potentially helpful,
bacteria increased. "This suggests that it might one day be feasible to
use light to restore a healthy bacterial balance in the mouth," Soukos
said.

   The current research stemmed from an observation by Max Goodson
DDS, PhD, Director of Clinical Research at Forsyth, that the blue light
used in a tooth whitening procedure appeared to decrease inflammation
of the gums.

   The team is currently developing a hand-held, light-based device
that might, one day, be used by consumers to help combat periodontal
disease.

   If proved effective in clinical trials Goodson said, "Technology
employing blue light to improve oral ecology could be the most
important advance in maintaining periodontal health since the invention
of the toothbrush."

   Background Previous Forsyth research had shown that as many as 700
different types of oral bacteria may be found in dental plaque that
accumulates on teeth. While some bacteria appear to be benign or even
helpful, others may invade and destroy gum tissue and bone -- leading
to loss of teeth, and, possibly, to infection elsewhere in the body.

   Among the more destructive bacteria are the so-called
"black-pigmented bacteria" (BPB) which have been implicated as
pathogens associated with periodontitis. Such bacteria accumulate black
pigment consisting mainly of organic compounds called porphyrins. Some
porphyrins are photosensitive, and, when activated by visible light,
induce a photodynamic reaction that kills the microorganism within
seconds.

   In embarking on their research, Soukos and Goodson knew that other
researchers had used lasers to deliver red or green light, which
partially inactivated certain oral bacteria. The Forsyth team also
knew, from published reports, that porphyrins absorb blue light more
readily than light that is red or green.

   The team employed a halogen lamp source commonly used for tooth
whitening to shine broadband light comprised mainly of blue and a small
percentage of green light (wavelengths ranged from 380 to 520
nanometers) on pure cultures of BPB and on dental plaque samples
obtained from individuals with chronic periodontitis.

   They found that the light rapidly killed BPB in pure cultures and
that it selectively eliminated BPB in plaque samples containing 500-600
different bacteria. They also found that certain species were more
readily inactivated by the light than others and that varying the
intensity and exposure time had different impacts on different species.

   The researchers conclude that intraoral light exposure can
selectively reduce pathogens in dental plaque.

   If proved effective in clinical studies, the findings could lead to
new methods for preventing or controlling periodontal disease. Such
methods would be rapid, non-invasive, and nontoxic, Soukos said.

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