A study of the control of oral plaque biofilms via antibacterial photodynamic therapy

Aim: The aim of this study was to provide preliminary data on the most effective erythrosine concentration and light dose for the erythrosine-based photodynamic therapy (PDT) of oral plaque biofilms formed in vivo. Method: A randomized controlled study with 15 volunteers was carried out to investigate the effect of photosensitiser and light dose on the killing of bacteria in oral plaque biofilms formed in vivo. All volunteers wore a removable in situ appliance carrying 6 enamel slabs for two phases of two weeks each. During this time, plaque biofilms accumulated on the enamel slabs. The slabs were then removed from the appliances for PDT-treatment in vitro. In the first phase of the study, erythrosine doses of 22 and 220uM were used for the photodynamic treatment of the biofilms. In the second phase, the erythrosine concentration was kept constant, and the light dose was varied. Following treatment, the biofilms were disaggregated, and the total bacterial killing determined using colony counting. Results: The erythrosine dose of 220uM caused the most cell killing relative to controls. Fifteen minutes continuous irradiation with light and light fractionation of 5x1 minute irradiation separated by 2 minute dark recovery periods were found to be the most effective bactericidal regimes. Conclusion: Erythrosine-based PDT shows promise as an anti-bacterial treatment for oral plaque biofilms. Further research is needed to prove its clinical and cost-effectiveness compared with current best practice