RESUMO
Photodynamic therapy (PDT) uses a photoactive dye (photosensitizer [PS])that activates by exposure to light of a specific wavelength in the presence of oxygen. The energy transfer from the activated PS to available oxygen leads to the formation of reactive oxygen species, such as singlet oxygen and free radicals. These chemical species are extremely reactive and can damage proteins, lipids, nucleic acids, and other components of the bacterial cell wall. Bacterial biofilms are widely implicated in their role in the causation of gingivitis and periodontitis. Prophylactic and therapeutic regimens for dental plaque related diseases include the usage of various chemotherapeutic agents. Since it is difficult to maintain therapeutic concentrations of these agents in the oral cavity and they run the risk of being rendered ineffective by bacterial resistance mechanisms, the need for an alternative antimicrobial approach in the treatment and prevention of dental plaque related diseases was felt. Many studies have reported the killing of bacteria via lethal photosensitization including both Gram-positive and Gram-negative bacteria. Photosensitization leads to bacterial elimination, with minimal chances of microbial resistance and with no adverse effects on host tissues and resident microflora. In dentistry, PDT has found use in the treatment of oral cancers, bacterial and fungal infections, and also in the detection of malignancies. PDT is free from genotoxic and mutagenic effects; another important factor for long-term safety. The ease of accessibility of the oral cavity to illumination makes it a suitable target for PDT.