TOOTHBRUSHES of the future may get breath fresher than any amount of
conventional brushing by using light and a special toothpaste to sterilise
people’s mouths. Light beamed into the mouth through the bristles of a
toothbrush could activate photosensitive compounds in the toothpaste, killing
the bacteria that cause tooth decay, gum disease and bad breath.
The idea stems from a cancer treatment called photodynamic therapy, in which
inactive chemicals are “switched on” by light. They generate singlet
oxygen—reactive, molecular oxygen—which attacks cell membranes.
Scientists at Imperial College and the Eastman Dental Institute in London are
now adapting this technique to fight oral bacteria. They had envisaged using
relatively powerful versions of the treatment in dental surgeries (Technology,
27 January, p 24), but are now patenting the toothbrush idea for everyday
“This therapy can tackle caries, gum disease and infections like
Candida albicans,” says Michael Wilson of the Eastman Dental
Institute. And the treatment will not damage the mouth and gums, since bacteria
appear to be more vulnerable to photodynamic therapy than healthy human
Light from a compact source in the handle of the toothbrush, such as a laser,
is guided to the ends of the bristles, which act as optical fibres. Brushing
brings the photosensitive compound into contact with the oral bacteria, and the
light activates the compound and begins to kill them.
David Phillips and Ilya Eigenbrot at Imperial College hope that the new
system will be simple and safe enough to use at home. However, the researchers
will have to brush up on their chemistry if their idea is to catch on: the
current generation of photosensitive compounds would stain the mouth blue. But
the team thinks that even without active toothpaste, the shear novelty of a
glowing toothbrush might encourage children to brush their teeth.