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 randomised controlled study with 15 volunteers was carried out to investigate the effect of photo-sensitiser and light dose on the killing of bacteria in oral plaque biofilms formed in vivo. All volunteers wore a removable in situ appliance carrying six enamel slabs for two phases of 2 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 220 muM 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 was determined using colony counting. RESULTS: The erythrosine dose of 220 muM caused the most cell killing relative to controls. Fifteen minutes of continuous irradiation with light and light fractionation of 5 x 1 min irradiation separated by 2-min-dark recovery periods were found to be the most effective bactericidal regimes. CONCLUSION: Erythrosine-based PDT shows promise as an antibacterial treatment for oral plaque biofilms. Further research is needed to prove its clinical and cost-effectiveness compared with current best practice.