Susceptibility of oral bacteria to antibacterial photodynamic therapy

Effective methods for managing the oral microbiome are necessary to ensure not only the oral but also the systemic health of a human body. The purpose of this study was to determine the sensitivity of four photosensitizers (PSs) to blue light in six representative oral bacterial species that cause intraoral diseases. The following six strains were investigated: Actinomyces israelii, Enterococcus faecium, Fusobacterium nucleatum, Lactobacillus gasseri, Streptococcus mutans, Veillonella parvula. PS stock solutions (1 mg/ml) were prepared by dissolving curcumin and protoporphyrin-IX in dimethyl sulfoxide, and resazurin and riboflavin in distilled water. The inoculation of 20 ml of a bacterial suspension cultured for 24 hours was mixed with 1,980 ml of each test solution, and then a light source was placed in front of the mixture. The irradiation wavelength was 405 nm and its applied energy was 25.3 J. The independent-samples t-test and one-way analysis of variance within groups were performed to compare the antibacterial effects in the four PSs. The antibacterial susceptibility when using different PSs and visible blue-light irradiation differed between the bacterial strains. Antibacterial photodynamic therapy that includes light exposure and PSs can be used to control the oral bacteria strains related to oral disease.