In the recent decade the applications of photodynamic therapy (PDT) rapidly increase in several topics and one of areas where the PDT in the future will be play significant role is dentistry. The different photosensitizing complexes with a good water solubility and with absorption with an intensive maximum in the red region (630-690 nm), which makes them suitable for photodynamic treatments, were investigated. The photochemical properties of complexes for singlet oxygen generation were investigated and were shown relations between uptake levels and light intensity to achieve increase in photodynamic efficacy. Photodynamic efficacy against fungi Candida albicans and bacteria's E. faecalis, MRSA and S. Mutans in planktonic media was evaluated. The high photodynamic efficacy was shown for SiPc at very low concentrations (0.9 μM) and light doses of 50 J cm-2 by intensity of light 60 mW cm-2. The photodynamic response for E. faecalis, MRSA and S. Mutans, after treatments with different photosensitizers show strong dependence on concentrations of photsensitzers and micro organisms. The level of inactivation of the pathogen bacteria's from 1-2 degree of initial concentration up to full inactivation was observed. The studied complexes were compared to the recently studied Methylene blue, Haematoporphyrine and tetra-methylpirydiloxy Zn(II)- phthalocyanines and experimental results show that some of them have a good potential for inactivation of representative pathogenic bacterial strains. Experimental results also indicate that photodynamic therapy appears an effective method for inactivation of oral pathogenic bacterias and fungi.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.