Within endodontics photodynamic therapy (PDT) has been suggested as a disinfectant procedure during root canal treatment. A photoactive dye (photosensitizer), methylene blue or toluidine blue, are activated by a light source, usually lasers or light emitting diodes (LEDs), thereby forming free oxygen radicals supposing to kill the bacteria. New ultraviolet (UV) LEDs may be used without a photosensitizer. A recent study compared the killing efficacy of UV irradiation with an existing PDT on Enterococcus faecalis biofilm. UV irradiation was provided using UV LEDs on the biofilms, in the UVB (296nm) and UVC (266nm) region. The PDT was applied using the commercial product Fotosan®. The UV LEDs were able to eliminate the E. faecalis biofilm while the PDT was only able to make a reduction in the total number of viable cells. UV LEDs may improve disinfection procedures during root canal treatments.