Photochemical improvement of antimicrobial photodynamic therapy mediated by methylene blue on periodontal pathogenic bacteria

Antimicrobial photodynamic therapy has been used as adjuvant in periodontitis treatment. Antimicrobial photodynamic therapy (aPDT) uses a photosensitizer and light to generate reactive oxygen species, inducing microbial cell death while minimizing damage to surrounding tissues. Dye dimerization difficulties this technique and sodium dodecyl sulfate (SDS) and urea may control it. The aim of this study was to investigate the photodynamic inactivation of periodontopathogenic bacteria using methylene blue (MB) under three independent conditions: in water, in urea, and in urea combined with SDS. P. gingivalis and A. actinomycetemcomitans were each used in 6 groups: Control; Light - irradiated only; PS - dye only; PDT1, PDT3, PDT5 with 1, 3 and 5 min of irradiation. The primary outcome was bacterial viability - CFU/mL, and the secondary one was photosensitizer uptake, assessed by optical absorbance. Data were analyzed by one-way ANOVA with Tukey's post hoc test. There was no significant decrease in P. gingivalis groups; with A. actinomycetemcomitans, PDT3 and PDT5 showed complete reduction with MB and in urea with SDS. A. actinomycetemcomitans incorporated approximately 20% more dye than P. gingivalis in MB and MB+urea, while MB+urea + SDS enhanced incorporation in both strains, with overall absorbance 10% higher than the other solutions. These results demonstrate that combining urea and SDS with MB enhances dye uptake and photodynamic efficacy against periodontopathogenic bacteria.