Susceptibility of Streptococcus mutans biofilms to photodynamic therapy: an in vitro study.
OBJECTIVE
The purpose of this study was to evaluate the antimicrobial effect of toluidine blue O (TBO), in combination with either a helium/neon (HeNe) laser or a light-emitting diode (LED), on the viability and architecture of Streptococcus mutans biofilms.


METHODS
Biofilms were grown on hydroxyapatite discs in a constant depth film fermentor fed with artificial saliva that was supplemented with 2% sucrose four times a day, thus producing a typical 'Stephan pH curve'. Photodynamic therapy was subsequently carried out on biofilms of various ages with light from either the HeNe laser or LED using energy densities of between 49 and 294 J/cm(2).


RESULTS
Significant decreases in the viability of S. mutans biofilms were only observed when biofilms were exposed to both TBO and light, when reductions in viability of up to 99.99% were observed with both light sources. Overall, the results showed that the bactericidal effect was light dose-dependent and that older biofilms were less susceptible to photodynamic therapy. Confocal laser scanning microscopy images suggested that lethal photosensitization occurred predominantly in the outermost layers of the biofilms.


CONCLUSIONS
Photodynamic therapy may be a useful approach in the treatment of dental plaque-related diseases.
Department of Microbiology and Immunology, Dental School of Piracicaba, State University of Campinas, 901 Limeira Av., Piracicaba, São Paulo, Brazil.
Iriana Carla Junqueira
IC
Zanin
Reginaldo Bruno
RB
Gonçalves
Aldo Brugnera
AB
Junior
Christopher Keith
CK
Hope
Jonathan
J
Pratten
D018441:Biofilms / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006863:Hydrogen-Ion Concentration; D053685:Laser Therapy; D007834:Lasers; D008027:Light; D018613:Microscopy, Confocal; D010789:Phototherapy / Q000379:methods*; D013295:Streptococcus mutans / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects*; D014048:Tolonium Chloride / Q000494:pharmacology
D014048:Tolonium Chloride