Purpose: This randomized in vitro study determined parameters for using a light-emitting diode (LED) with toluidine blue O (TBO) for reduction of Streptococcus mutans counts inside carious dentin. Materials and Methods: Seventy-two bovine coronary dentin slabs were immersed in Streptococcus mutans culture for demineralization. Dentin slabs were allocated to 6 groups (n = 12) as follows: control (treated with 0.9% NaCl solution for 5 min); TBO (treated with 0.1 mg/ml TBO for 5 min); LEDA (submitted to irradiation for 4.2 min); LEDB (submitted to irradiation for 6.5 min); photodynamic therapy A (PDTA; treated with TBO plus irradiation for 4.2 min) and photodynamic therapy B (PDTB; treated with TBO plus irradiation for 6.5 min). The energy densities used for 4.2 and 6.5 min correspond to 166 and 249 J/cm2, respectively. Before and after treatments, dentin samples were analyzed with regard to S. mutans counts. The carious lesion depth produced by the microbiological model was analyzed by polarized light microscopy. ANOVA/Tukey tests were utilized to compare log reductions among groups (α = 5%). Results: Bacterial reduction was observed when dentin was exposed to both TBO and LED at both irradiation times. However, no difference in S. mutans reduction was found between the two energy densities. Conclusion: Although the use of LED combined with TBO was effective in reducing the Streptococcus mutans counts in carious dentin, this effect may not have clinical significance.
Keywords: LED, caries, bovine tooth, Streptococcus mutans, in vitro study, dentin