Antimicrobial photodynamic therapy (aPDT) relies on the light activation of a photosensitizer to generate ROS that inactivate bacteria. This thesis investigated the efficiency of three blue light-absorbing photosensitizers, curcumin, Eosin Y and Rose Bengal, on several oral pathogens. Flow cytometry has been used to assess the antibacterial activity. Our results demonstrated that aPDT has the potential to efficiently inactivate bacteria with minimum adverse effects to host cells. Biofilms have shown a reduced susceptibility to aPDT as compared to planktonic bacteria. Optimizing aPDT parameters, such as light dose and photosensitizer delivery, was shown to increase the antibacterial effect on biofilms. Rose Bengal has demonstrated the ability to incorporate into the membranes of Gram-positive and –negative bacteria in sufficient amount to inactivate them upon blue light-irradiation. Although, aPDT has proven to be efficient against various oral pathogens, future research is warranted to improve the antibacterial activity against biofilms.