Background: Current research aims to find alternatives to conventional methods for suppressing periodontopathogenic bacteria. Photodynamic therapy (PDT) could be a suitable treatment procedure of periodontal infections.

Methods: In the present study, the PDT method was tested with two photosensitizers, chlorine e6 and BLC1010, in an experiment on beagle dogs. The animals were infected with Porphyromonas gingivalis (Pg) and Fusobacterium nucleatum (Fn) in all subgingival areas. After infection, we observed clinical signs of gingival inflammation, including an increase of redness and bleeding on probing. Microbiological monitoring before and after treatment was performed using polymerase chain reaction (PCR). PDT was conducted with a diode laser with a wavelength of 662 nm using a power of 0.5 W and the photosensitizers.

Results: The PDT procedure carried out with either of the photosensitizers caused a significant reduction in the clinical inflammation signs of redness and BOP, compared to the controls (laser only and no treatment). Furthermore, PDT with chlorine e6 caused a significant reduction in P. gingivalis-infected sites, whereas there was a lack in suppression after PDT with BLC1010. F. nucleatum could hardly be reduced with chlorine e6, and only to a certain extent with BLC 1010 and laser only. In the control groups, the Pg-infected test sites did not change.

Conclusions: This study demonstrated that the photodynamic therapy using photosensitizer and a 662 nm laser light source is distinctly advantageous in reducing the periodontal signs of redness and bleeding on probing. The procedure also appears to significantly suppress P. gingivalis. J Periodontol 2005;76:1100-1105.