Blue photosensitizers for aPDT eliminate Aggregatibacter actinomycetemcomitans in the absence of light: An in vitro study

The main treatment of periodontal disease is the mechanical removal of supra and subgingival biofilm. Adjuvant therapies as antimicrobial photodynamic therapy (aPDT) may offer improved clinical and microbiological results. The aim of this in vitro study was to evaluate the effect of toluidine and methylene blue dyes, associated with red laser and LED, on elimination of a suspension of Aggregatibacter actinomycetemcomitans (A.a). Experimental groups (n = 29) consisted of positive (broth) and negative (gentamicin) controls, three different dyes concentrations (0.05; 0.1; 10 mg/ml) alone or associated with laser (660 nm) at two power settings (70 and 100 mW) and LED (627 ± 10 nm). Bacterial suspension received all treatments, and after serial dilutions they were cultured for 24 h in petri dishes for colony forming unit counts. Data were analyzed by ANOVA complemented by Tukey's test (p 0.05). It can be concluded that blue dyes for aPDT, at high concentration (10 mg/ml), are capable of eliminating A.a without adjuvant use of light sources. •Methylene 10 mg/ml with LED and with red laser 100 mW had bactericidal effect.•Methylene group 10 mg/ml with 70 mW red laser showed a significant reduction.•Toluidine blue 10 mg/ml with LED/laser showed similar results to the negative control.•All other toluidine groups were similar to the positive control.•Toluidine and methylene blue dyes at 10 mg/ml are effective in eradicated A.a.