Bactericidal effect of laser light and its potential use in the treatment of plaque-related diseases.

Chemical antibacterial agents are increasingly being used in prophylactic and therapeutic regimes for plaque-related diseases. As these agents can be rendered ineffective by the development of resistance in the target organisms there is a need to develop alternative antimicrobial approaches. Light from high-power lasers is known to be bactericidal and investigations have shown that it is effective against organisms implicated in caries and inflammatory periodontal diseases. However, the adverse effects of such light on dental hard tissues argue against its use solely as an antibacterial agent. Although light from low-power lasers has no adverse effect on bacterial viability, bacteria can be sensitised to killing by such light by prior treatment with a chemical photosensitising agent. Lethal photosensitisation of a wide range of cariogenic and periodontopathogenic bacteria has been demonstrated using light from a helium/neon or gallium aluminium arsenide laser in conjunction with a dye such as toluidine blue or aluminium disulphonated phthalocyanine as a photosensitiser. The advantages of the technique are that killing is achieved in very short periods of time (< 60 s), resistance development in the target bacteria would be unlikely and damage to adjacent host tissues can be avoided. This approach may be a useful alternative to antibiotics and antiseptics in eliminating cariogenic and periodontopathogenic bacteria from disease lesions.