Comparative evaluation of photodynamic therapy using LASER or light emitting diode on cariogenic bacteria: An in vitro study

OBJECTIVE: The aim of this study was to evaluate in vitro the effect of photodynamic therapy (PDT) using LASER or light emitting diode (LED) on cariogenic bacteria (Streptococcus mutans [SM] and Lactobacillus casei [LC]) in bovine dentin. MATERIALS AND METHODS: Twenty five fragments of dentin were contaminated with SM and LC strands and divided into five experimental groups according to the therapy they received (n = 5): C – control (no treatment), SCLED – no dye/LED application (94 J/cm(2)), SCLASER – no dye/LASER application (94 J/cm(2)), CCLED – dye/LED application (94 J/cm(2)) and CCLASER – dye/LASER application (94 J/cm(2)). The dye used was methylene blue at 10 mM. Dentin scrapes were harvested from each fragment and prepared for counts of colony forming units (CFU)/mL. The data were analyzed using Kruskal–Wallis, followed by Student–Newman–Keuls (α =0.05). RESULTS: Regarding SM, groups CCLASER and CCLED showed a significant reduction in CFU/mL, which was statistically superior to the SCLASER, SCLED and C groups. Regarding LC, the groups CCLASER and CCLED caused a significant reduction in CFU/mL when compared with SCLASER, which showed intermediate values. SCLED and C had a lesser effect on reducing CFU/mL, where the former showed values similar to those of SCLASER. CONCLUSIONS: In conclusion, PDT combined with LASER or LED and methylene blue had a significant antimicrobial effect on cariogenic bacteria in the dentin.