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Boston--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."
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)
whichhave 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 sourcecommonly 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.

The research was funded in part by National Institute of Dental and Craniofacial Research and 
BriteSmile Development Inc.
The Forsyth Institute is an independent, non-profit research organization focused on 
oral, craniofacial and related biomedical science.