EFFECT OF DOSIMETRIC AND PHYSIOLOGICAL FACTORS ON THE LETHAL PHOTOSENSITIZATION OF PORPHYROMONAS-GINGIVALIS IN-VITRO

The aims of this study were to (1) determine the effect of dosimetric and physiological factors on the lethal photosensitization of Porphyro monas gingivalis using toluidine blue O (TBO) and light from a helium/ neon (HeNe) laser; (2) determine the influence of sensitizer concentra tion, preirradiation time, serum and growth phase on sensitizer uptake by P. gingivalis. The dosimetric factors studied were concentration o f TBO, light dose and preirradiation time. The physiological factors w ere presence of serum, pH and bacterial growth phase. Sensitizer uptak e by P. gingivalis under various conditions was determined using triti ated TBO (H-3-TBO). In the presence of TBO, a light dose-dependent inc rease in kill was attained (100% kill at 4.4 J). There was no signific ant effect on the numbers killed when TBO was increased from 12.5 to 5 0 mu g/mL. An increase in preirradiation time gave slightly increased kills, High kills were achieved at all three pH (6.8-8.0). Although ki lls were substantial in the presence of serum, they were significantly less than those obtained in the presence of saline, Cells in all thre e growth phases were susceptible to lethal photosensitization, althoug h stationary phase cells were slightly less susceptible. Maximum uptak e of TBO occurred within 60 s and uptake in serum was less than in sal ine. The uptake by the log phase cells was greater at lower concentrat ions of sensitizer (50 mu g/mL), compared to the other two phases.