Antimicrobial photodynamic therapy has been used as adjuvant in periodontitis treatment. Dye dimerization difficulties this technique and sodium dodecyl sulfate – SDS - and urea may control it. The aim of these study was investigated the role of urea and urea 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 5min of irradiation. Dyes uptake and the absorbance spectrum were analyzed. There was no significant decrease in P. gingivalis groups; with A. actinomycetemcomitans, PDT3 and PDT5 showed complete reduction with dye in water and in urea with SDS. A. actinomycetemcomitans incorporated more dye than P. gingivalis. Absorbance at P. gingivalis showed slightly higher, and between the different media it was similar. The vehicles optimized the bacteria inactivation and increased aPDT effectiveness; the urea increased microbial death.