The advancement in science and technology in the medical field amends a path for embedding new treatment modalities to the challenges presented by the viable diseases.Photodynamic therapy(PDT), sometimes called photochemotherapy, is a form of phototherapy using nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they become toxic to targeted malignant and other diseased cells. PDT has proven ability to kill microbial cells, including bacteria, fungi and viruses. This utilizes light to activate a photosensitizing agent in the presence of oxygen. The exposure of the photosensitizer to light results in the formation of toxic oxygen species, causing localized photodamage and cell death. Clinically, this reaction is cytotoxic and vasculotoxic. Depending on the type of agent, photosensitizers may be injected intravenously, ingested orally, or applied topically. Applications of PDT in dentistry is growing rapidly in the treatment of oral cancer, bacterial and fungal infection therapies, and photodynamic diagnosis (PDD) of the malignant transformation of oral lesions.