Light in the blue region of the visible spectrum can be used selectively to suppress bacteria commonly associated with periodontitis, according to a study in the April issue of Journal of Antimicrobial Agents and Chemotherapy.
Researchers at The Forsyth Institute 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, other bacteria may invade and destroy gingiva 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) that have been implicated as pathogens associated with periodontitis. BPB accumulate black pigment consisting mainly of organic compounds called porphyrins. Some porphyrins are photosensitive, and when they are activated by visible light, a photo-dynamic reaction is induced that kills the microorganism within seconds.
Principal investigator Dr. Nikos Soukos, director of the Forsyth Laboratory of Applied Molecular Photomedicine, and colleague Dr. Max Goodson, director of Clinical Research at the Forsyth Institute, knew that other researchers had used lasers to deliver red or green light to partially inactivated certain oral bacteria, and that porphyrins absorb blue light more readily than red or green light.
In a study funded in part by National Institute of Dental and Craniofacial Research and BriteSmile Development, they used a halogen lamp source commonly used for tooth whitening to shine broadband light composed mainly of blue and a small percentage of green light (wavelengths ranged from 380-520 nanometers) on pure cultures of BPB and on dental plaque samples obtained from people 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 to 600 different bacteria. They also found that certain bacteria species were inactivated more readily by the light than were others. Varying the intensity and exposure times had different effects on different bacteria species.
They also found that when the proportion of BPBs was reduced, the proportion of 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," Dr. Soukos said.
The team is developing a hand-held, light-based device that one day might be used by consumers to help combat periodontal disease.
