as photosensitiser that is activated by exposure to light of a specific wavelength in the presence of oxygen. The transfer of energy from the activated

photosensitizer to available oxygen results in the formation of toxic oxygen species, such as singlet oxygen and free radicals. These very reactive

chemical species can damage proteins, lipids, nucleic acids, and other cellular components. Applications of PDT in dentistry are growing rapidly:

the treatment of oral cancer, bacterial and fungal infection therapies, and the photodynamic diagnosis of the malignant transformation of oral

lesions. PDT has shown potential in the treatment of oral leukoplakia, oral lichen planus, and head and neck cancer. PDT is being also tested in the

case of eradication of microbia which colonized root canals and dental plaque. The absence of genotoxic and mutagenic effects of PDT is an

important factor for long–term safety during treatment. The application of a Photodynamic therapy might be a new, potent tool in dental disorders.