Selecting suitable substances for photodynamic therapy in periodontitis

objectives: Photodynamic therapy (PDT)is an interesting anti-infective approach in periodontitis treatment.It was the aim of our study to select suitable photosensitizers (PS) for subsequent pre-clinical and clinical studies and to set up an efficient test setting for testing further substances. Methods: The in vitro test setting, which is presented here, is based on human gingival fibroblasts (HGF, primary cell culture), treated root surfaces (dentine slices of unaffected 3rd molars) and animal tissues. There exist many known photosensitizers. So far we examined chlorines, pheophorbides and dyes. Absorption spectra were recorded in a photospectrometer. The following tests on HGF included variations in PS-concentration, incubation time and irradiation power density using lasers at 532 and 665 nm. PDT temperature generation was measured in an animal tissue model. At last, for one of the dyes (BLC 2003), adherence and proliferation tests were conducted on prepared and irradiated root surfaces. A light microscope and an electron microscope were used to evaluate the number and morphology of the adhered fibroblasts. Results: All tested candidate substances revealed photodynamic activity to different degrees. Most effective was the Chlorine BLC 1013. Least effective was the Pheophorbide BLC 1060. The temperature rise by PDT was not critical, the proliferation of HGF on treated root surfaces was slightly inhibited by the dye BLC 2003 (p=0.001, Mann-Whitney U test). Conclusion: While the test setting presented so far is effective in estimating the phototoxic potential of various substances, more specific tests like the presented adhesion/proliferation test should also be included when substances are going to be screened. Support: Photosensitizers and Lasers were kindly provided by the biolitec AG, Jena, Germany.