Lethal Photosensitization of Cariogenic Bacteria Inseminated into Tooth Slices

Objectives: The aim of this study was to determine the effect of lethal photosensitization on the viability of various cariogenic bacteria present in the tooth structure. Methods: Tooth slices were incubated with broth cultures of four cariogenic organisms for 24h at 37^oC to allow the formation of biofilms. Photosensitization was carried out with a diode (GaAlAs) laser in the presence of Toluidine Blue O (TBO) as the sensitizer. The bacterial biofilms were exposed to the diode laser for 1 minute in the presence of TBO as a test group. Furthermore one group was exposed to TBO alone, one to laser alone and one was not exposed to either TBO or laser (control). Results: Overall, the results showed reductions in the viability of all bacteria investigated in the test group. Significant reductions were observed in the viability of Lactobacillus casei (13%) as well as Streptococcus mutans (20%) and Actinomyces viscosus (53%) relative to the controls (100% viability). The viability of Streptococcus salivarius was the least affected (86%). Conclusion: The current study indicates that lethal photosensitization of cariogenic bacteria may provide an alternative or an additional approach to treating caries. Using this approach the need to remove the bulk of dentin can be circumvented.