Methods: S. mutans was grown in planktonic culture and incubated with the photosensitizer (PS) tin ethyl etiopurpurin for 30 min, then exposed to a 664 nm diode laser at doses of 15, 30 and 45 j/cm2 (treatment groups in triplicate, control groups in duplicate). S. mutans was also grown in biofilms on glass and polished denture acrylic and subjected to the same photodynamic assays. After 48h, colony-forming units (CFUs) were counted to determine survival following the PDT assays.
Results: Survival was greatly reduced (greater than 3-log kill) in all planktonic light treatment groups (Light doses = 15, 30, and 45 j/cm2 with (PS)) compared to the control groups (No light/No (PS), No light/(PS) and No light/DMSO). Survival was reduced in the biofilm light treatment groups on glass and polished denture acrylic. Higher light doses (45 j) achieved greater than 3-log kill in biofilms grown on glass, but all light doses achieved a greater then 3-log kill on biofilms grown on polished denture acrylic.
Conclusions: Photodynamic therapy is effective against S. mutans in planktonic culture and biofilm using the photosensitizer tin ethyl etiopurpurin at light doses of 15, 30, and 45 j/cm2.